GB1603113A

GB1603113A - Methods of and apparatus for monitoring the relative locations of a valve and a valve seat

Info

Publication number: GB1603113A
Application number: GB995677A
Authority: GB
Original assignee: Engineering Research & Applic
Current assignee: Engineering Research & Applic
Priority date: 1978-03-31
Filing date: 1978-03-31
Publication date: 1981-11-18

Description

(54) IMPROVEMENTS IN OR RELATING TO METHODS OF AND APPARATUS FOR MONITORING THE RELATIVE LOCATIONS OF A VALVE AND A VALVE SEAT (71) We. ENGINEERING RE SEARCH AND APPLICATION LI MITED, a British Company of London Road, Dunstable, Bedfordshire. LU6 3UR, do hereby declare the invention for which we pray that a patent may be granted to us, and the method bv which it is to be performed to be particularly described in and by the following statement: This invention relates to methods of and apparatus for monitoring the relative locations of a valve and a valve seat which co-operate together to control induction and/or exhaust of a gaseous medium through a port in a wall of a chamber.

The technique for setting intake and exhaust valves of motor vehicle internal combustion engines in relation to the rocker arms with which they are associated in use, which is in general use in plant for the volume production of motor vehicles, involves the setting of a gap between the valve and the associated rocker arm by shop floor operatives with the aid of conventional feeler gauges. It has been realised that a higher standard of accuracy in the setting of intake and exhaust valves of motor vehicle internal combustion engines could be achieved in such an environment if there was a simple method which could be operated readily by shop floor operatives in such plant to indicate accurately that a partially unseated intake or exhaust valve is displaced from its valve seat by a predetermined distance.One proposal which has been made comprises the step of introducing a controlled supply of air into the combustion chamber of the engine and of monitoring the rate of flow that controlled air supply during movement of the valve away from its valve seat in order to provide an indication of the displacement af the valve from its valve seat in terms of the consequent change in the monitored air flow. It was found however that the relationship between displacement of a valve from its valve seat and the consequent change in the monitored air flow rate varies from one engine to another so that the method as proposed was not suitable for use by shop floor operatives in plant for the volume production of motor vehicles in order to set the intake and exhaust valves of the engines in relation to the rocker arms with which they are associated in use.

The object of this invention is to provide a method of and apparatus for determining the relative locations of an unseated valve and its associated valve seat which can be used readily by shop floor operatives in plant for the volume production of motor vehicles as an aid in the setting of the intake and exhaust valves of the engines of a series of motor vehicles produced in that plant.

This invention arises from our application that the relationship between the displacement from its valve seat of an intake or exhaust valve of an internal combustion engine and the change in the flow rate of a flow of air into the respective combustion chamber which accompanies such movement of that valve varies from one engine to another because each cylinder of each engine has various leakage paths by which air supplied to the combustion chamber that is formed in that cylinder leaks from that chamber when the associated intake and exhaust valves are seated and that each cylinder of each engine has its own individual characteristics for such leakage.

Accordingly we have concluded that the effects of such leakage upon the change in the monitored air flow rate that accompanies displacement of each intake or exhaust valve from its related seat must be taken into account if any such change in the monitored air flow rate is to be used to produce an indication of the corresponding displacement of the intake or exhaust valve from its seat.We have realised also that our invention is not limited in its application to methods of and apparatus for determining the relative locations of an unseated internal combustion engine intake or exhaust valve and its associated valve seat during the setting of such a valve relative to the rocker arm with which it is associated in use. but that our invention is applicable to any situation in which an indication is required of the relative locations of a valve and a valve seat which co-operate together to control induction and/or exhaust of a gaseous medium through a port in a wall of a chamber which has a potential gaseous medium leakage path separate from such a port.

According to one aspect of this invention there is provided a method of monitoring the relative locations of a valve and i valve seat which co-operate together to control induction and/or exhaust of a gaseous medium through a port in a w;;ll of a chamber which has a potential gaseous medium leakage path separate lrolll any such port, wherein fluid is caused 1() flow into the chamber, the fluid flow is moni- tored and an output signal is derivctl ll-om a factor of that fluid flow which valves with movement of said valve relative to its valve seat and which is effectively uninlluenced by leakage from said chamber olller than through said port, said output signil being used as an indication of the relative location of the valve and the valve sell.

Preferablv a substantially constant pressure is established within the ch'imher by air flowing into the chamber before the valve is moved relative to its valve seit and the output signal is derived.

The output signal may be an indication of rate of change of pressure of fluid flow to the chamber which accompanies movement of said valve relative to its valve seat after the establishment of such a substantially constant pressure in the chamber because within sensible limits, the initial response of the rate of change of pressure to movement of the valve is virtually insensitive to the substantially constant pressure that is established in the chamber. However such an output signal is not readily presentable in an analogue form on a visual indicator.Presentation of the output signal in an analogue form on a visual indicator is desirable because it enables a shop floor operative to appreciate the proximity of a predetermined location of the valve relative to its valve seat and thus the sense and the order of minor adjustment he must make in order to st the valve in the required location if a method according to this invention is being carried out during the setting of intake or exhaust valves of internal combustion engines relative to the rocker arms with which they are associated in use.

Accordingly we prefer that the output signal comprises the difference between the rate of flow of fluid to the chamber at a given instant when the valve is unseated and the rate of flow of fluid to the chamber that prevailed when the valve was seated and the substantially constant pressure was established within the chamber.

According to another aspect of this invention there is provided apparatus for monitoring the relative locations of a valve and a valve seat which co-operate together to control induction and/or exhaust of a gaseous medium through one port in a wall of a chamber which has a potential gaseous medium leakage path separate from any such port, the apparatus comprising a fluid source at which fluid is available at a controlled rate of flow and pressure. a conduit for conveying fluid from the fluid source to another port of the chamber, a transducer which is responsive to fluid flow through the conduit and the chamber when the conduit is connected to said other port and the apparatus is in use. the transducer having an outlet from which it emits an electrical signal which is a function of that fluid flow whereby that fluid flow is moni tore, signal processing means and indicating means, the signal processing means having an input which is connected to the output of the transducer so as to receive an electrical signal which is emitted bv the transducer, and an output which is connected to an input of the indicating means, the signal processing means being arranged to derive from the electrical signals received from the transducer an the output signal which is a function of a factor of the fluid flow which varies with movement of said valve relative to its seat and which is effectively uninfluenced by leakage from said chamber other than through said one port the indicating means being arranged to display the output signal as an indication of the relative locations of the valve and the valve seat.

The signal processing means ma) comprise a differentiator circuit. The signal processing means may include a comparator as well. The indicating means may comprise one indicator which is operable by an output signal emitted by the comparator hen the comparator indicates that the electrical sig- nal received from the transducer is below a predetermined level. The indicating means may include two other indicators which are operable bv output signals from the differentiator circuit when the comparator senses that the electrical signal emitted by the transducer exceeds the predetermined level, one of said other indicators being activated by an output signal from the differintiator circuit which indicates zero rite of change in the magnitude of the electrical signal received by the differentiator circuit from the transducer and the other of said other indicators being adapted to be actuated by an output signal from the differentiator circuit which indicates a negative rate of change in the output signal from the transducer within predetermined limits.

Each of the three indicators may be visual indicators such as lamps. Preferablv the transducer responds to pressure of fluid in the conduit which is related to the rate of flow of fluid through the conduit.

The signal processing means of the preferred form of apparatus in which this invention is embodied includes signal storage means and comparator means, the signal storage means being for storing a signal emitted by the transducer which indicates the establishment of substantially constant conditions of pressure within the conduit or the chamber and the comparator means being for comparing the signal stored by the signal storage means with the output signal of the transducer and for emitting an output signal which is conveyed to the indicator means, that output signal comprising the difference between the signal stored by the signal storage means and the output signal from the transducer with which it is compared. the indicating means including ana tongue display means for displaying the output signal received from the comparator continuously.

The apparatus may include differentiating means for differentiating with respect to time the signal that is emitted bv the transducer once substantially constant pressure conditions have been established within the conduit and the chamber, and first and second comparator means associ- ated with the differentiating means, the first comparator means being adapted to compare the differentiation of the signal that is emitted by the transducer with a reference and to emit an output signal when the differentiated signal is positive, the output signal from the first comparator means being adapted to effect cancellation of the signal that is stored by the signal storage means and storage of a fresh output signal from the transducer in its place. and the second comparator means being adapted to compare the differentiation of the signal that is emitted by the transducer with a reference signal and to emit an output signal when the differentiated signal is negative, such an output signal from the second comparator means being adapted to disenable further operation of the differentiating means.

Conveniently the apparatus includes a probe fitted to one end of the conduit and for insertion into said other port. the probe comprising a valve head, a tubular body and a two-position rotary shut-off valve in the valve head, the valve head forming an inlet port to which said one end of the conduit is connected and an outlet port which communicates with the bore of the tubular body, the two-position rotary shut-off valve being adapted to allow communication between the inlet and the outlet in one of its two positions and to shut off such communication in its other position, the probe carrying an annular collar of deformable material, which abuts an annular shoulder which is formed at the end of the tubular body remote from the valve head, and a tubular sleeve which is slidable upon the outer surface of the tubular body, the rotary valve carrying lever operable cam means outside the valve head, the cam means co-operating with a follower surface formed at the end of the tubular sleeve remote from the collar.

the arrangement being such that the collar is in its relaxed condition when the valve is in said other position to shut off communication between the inlet and the outlet so that, when said end of the probe and the collar are inserted into the other port of -the chamber and the lever operable cam means ale rotated to rotate the rotary valve from said one position to the other position to open communication between the inlet and the outlet of the valve head to allow fluid to flow through the probe into the chamber.

the cam means force the tubular sleeve towards said end of the probe so as to deform the collar and effect a fluid tight seal between the probe and said other port when the rotary valve member is in said other position.

One embodiment of this invention will be described now bv wav of example with reference to the accompanying drawings in which: Figure 1 is a diagrammatic illustration of apparatus according to this invention for setting intake and exhaust valves of internal combustion engines: Figure 2 is a partly sectional side elevation of a probe which forms part of the apparatus that is illustrated in Figure 1 and is drawn to a larger scale than Figure 1. the probe being illustrated in the condition it adopts when it is in use to allow air flow through it:: Figure 3 is a section on the plane III-III of Figure 2 with the probe shown in the inoperative condition; Figure 4 is a graphical illustration of a method for setting intake and exhaust valves of internal combustion engines using the apparatus illustrated in Figures 1 to 3; Figure 5 is a diagrammatic illustration of another form of signal processing means for use in the apparatus that is illustrated in Figures 1 to 3; Figure 6 is a graphical illustration of a method for setting intake and exhaust valves of an internal combustion engine using the apparatus illustrated in Figures 1, 2, 3 and 5 of the accompanying drawings.

Figure 7 is a diagrammatic illustration of a modification to the form of signal processing means illustrated in Figure 5; and Figure 8 is a graphical illustration of a method for setting intake and exhaust valves of internal combustion engines using the modified apparatus illustrated in Figure 7.

The apparatus illustrated in Figure 1 comprises a pressure regulator 11 which has an inlet 12 which is for connection to a source of clean dry compressed air. The regulator 11 has an outlet 13 as well which is connected to a length of flexible tubing 14 via a calibrated flow restriction 15.

The flexible tubing 14 has two tappings 16 and 17. An air inlet port of a pressure gauge 18 is connected to the tapping 16. An air inlet port of an electro-pneumatic transducer 19 is connected to the tapping 17.

The transducer 19 has an output terminal 21 from which an output signal is emitted, the output signal being generated by the transducer 19 and being related to the air pressure at the air inlet of the transducer 19.

A lead 22 connects the output terminal 21 to an input terminal 23 of electronic signal processing means 24 which have three output terminals 25, 26 and 27. A first lamp 28 is connected to the output terminal 25 and conveniently is coloured blue. A second lamp 29 is connected to the output terminal 26 and conveniently is coloured red. A third lamp 31 is connected to the output termfinal 27 and conveniently is coloured green.

A tubular probe 32 is fitted at one end to the end of the flexible tubing 14 remote from the calibrated restriction 15. The other end of the probe 32 is adapted to be seated in a fluid tight manner within the spark plug aperture 33 of a cylinder 34 of a spark ignition internal combustion engine for an automobile.

The detailed construction of a preferred form of tubular probe 32 will be described now with reference to Figures 2 and 3.

A tube 35 is screwed at one end into a tapped hole 36 which is formed in a valve head 37. The inner end of the tapped hole 36 is open and comprises an outlet port 38 which is formed in the larger diameter portion of the cylindrical wall of a two diameter stepped through bore 39. A grub screw 40 locks the tube 35 in position within the hole 36. An inlet port 41 is formed in the larger diameter portion of the through bore 39 as well and is at the inner end of another tapped hole 42 in the valve head 37. An obtuse angle is included between the axes of the tapped holes 36 and 42 which are contained within a plane which is normal to the axis of the through bore 39. The end of the length of flexible tubing 14 remote from the transducer 19 is received in the tapped hole 42 in a fluid tight manner.A stepped spool 43 having two portions of different diameters is a sliding fit within the through bore 39 and is larger than the bore 39 so that it projects from the bore 39 at either end when the step between its two portions abuts the annular shoulder between the two portions of the bore 39. Each portion of the stepped spool 43 has an annular groove 44, 45 formed in it and each groove 44, 45 accommodates a sealing ring 46, 50. The larger diameter portion of the spool 43 has a recess 47 formed in it between its annular groove 45 and the step, the base of the recess 47 being flat and being in a diametral plane of the spool 43. The recess 47 is aligned with the inlet and outlet ports 38 and 41 when the step abuts the shoulder in the stepped bore 39.

The spool 43 carries a cam plate 48, 49 at either projecting end. A handle 51 is fitted to the cam plate 49 so that the spool 43 and the two cam plates 48 and 49 can be rotated manually about the axis of the bore 39 between one position, which is shown in dotted lines in Figure 2, in which communication between the inlet port 41 and the outlet port 38 is blocked by the spool 43 and another position, shown in full lines in Figure 2, in which the inlet port 41 communicates with the outlet port 38 via the recess 47.

An annular recess 52 is formed in the outer surface of the tube 35 near to the end of the tube 35 that is remote from the valve head 37. The bore of the tube 35 is reduced at that end to form an outlet nozzle 53. A collar 54 of elastomeric or other suitable resiliently deformable impervious material is fitted into the annular recess 52. The collar 54 has an annular flange 55 at its end nearer to the valve head 37.

A rigid tubular sleeve 56 is a sliding fit on the outer surface of the tube 35, extends between the flange 55 of the collar 54 and that part of the valve head 37 that surrounds the outer end of the tapped hole 36, and has an annular flange 57 at its end nearer to the valve head 37. The sleeve 56 is held, by the resilient loading of the collar 54. with its flange 57 in abutment with the valve head 37 when the handle 51 and the cam plates 48 and 49 are in the position which is illustrated in dotted lines in Figure 2. so that the collar 54 is relaxed as shown in Figure 3. Rotation of the cam plates 48 and 49 with the spool 43 by angular movement of the handle 51 from the position shown in dotted lines in Figure 2 to the position shown in full lines in Figure 2. causes the rigid sleeve 56 to be forced towards the nozzle 53 by the interaction of the profiled edges of the cam plates 48 and 49 and the follower surface that comprises the adjacent end face of the annular flange 57. The resultant axial movement of the tubular sleeve 56 causes deformation of the collar 54 so that the sleeve portion of the collar 54 is belled outwardly as shown in Figure 2.

In order to use the apparatus to set the clearances for the intake and exhaust valves 58 and 59 of a cylinder 34 of an engine, the operator connects the pressure regulator input 12 to the source of clean dry compressed air, the handle 51 being positioned as shown chain dotted in Figure 2 so that communication between the interior of the flexible tubing 14 and the nozzle 53 is blocked by the rotary spool valve 43. The pressure regulator 11 is then set to establish a predetermined controlled level of air pressure upstream of the calibrated restriction 15 (say 15 p.s.i.) which. because there is no air flow through the restriction 15 and the tubing 14, will be indicated by the pressure gauge 18 and by an appropriate output signal from the transducer 19.The end of the probe 32 that carries the collar 54 is then inserted into the spark plug aperture 33 of the cylinder 34. the operator having first checked to ensure that the engine camshaft is positioned so that the cam followers which govern the positions of the intake and exhaust valves 58 and 59 are engaged with the minimum diameter portions of the respective cam and thus so that the intake and exhaust valves 58 and 59 are seated as shown in Figure 1. The operator will also have checked to ensure that the manual adjusters that are provided for adjusting the clearance between each intake or exhaust valve SX. 59 and its associated rocker arm (not shown) are slack.The handle 51 is then rotated to open the rotary valve 43 so that the sleeve 56 is moved towards the collar 54 which is deformed to effect a fluid tight seal between the probe 32 and the periphery of the spark plug aperture 32, and air flows into the cylinder 34 from the flexible tubing 14 via the bore of the tube 32 and the nozzle 53 at its end. The pressure in the tubing 14 downstream of the calibrated restriction 15 will fall until the conditions of air flow through the flexible tubing 14 and into the cylinder 34 stabilise and a substantially constant pressure level is maintained in the cylinder 34 annd the flexible tubing 14. Leakage of air from the cylinder 34 for example past the piston rings, will result in a steady small air flow through the flexible tubing 14 and the cylinder 34 when stabilised conditions have been established.

The electronic signal processing means 24 will respond to the output signals it receives from the transducer 19 by sensing the fall of pressure in the flexible tubing 14 and the establishment subsequently of substantially constant pressure conditions in the cylinder 34 and in the flexible tubing 14 at a level below that set initially by manipulation of the pressure regulator 11 and will be rendered operative to monitor output signals from the pressure transducer 19 in response to the establishment of those two conditions.

The magnitude of the output signal from the pressure transducer 19 will be compared with another signal which represents a predetermined minimum level of pressure (say 5 p.s.i.) once the electronic signal processing means 24 are operative.

The first lamp 28 will be energised by the signal processing means 24 if the pressure at which substantially constant pressure conditions in the cylinder 34 and the flexible tubing 14 are established is below the predetermined minimum level and energisation of that first lamp 28 will indicate that the magnitude of leakage from the cylinder 34 is excessive so that the engine will be rejected and no further attempt will be made to set the clearances of the intake and exhaust valves 58 and 59.

The second lamp 29 will be energised by the signal processing means 24 if the pressure at which substantially constant pressure conditions in the cylinder 34 and the flexible tubing 14 exceed the predetermined minimum level. The operator will insert an appropriate setting gauge between the end of the valve stem of one of the intake and exhaust valves 58 and 59 and the rocker arm with which it co-operates when the second lamp 29 is energised. He will then manipulate the adjuster provided on that rocker arm so as to move that rocker arm in the direction necessary to effect opening movement of the respective valve 58, 59, such movement being transmitted to that valve 58, 59 through the setting gauge so that the valve 58, 59 is unseated.

The signal processing means 24 of one form of apparatus in which this invention is embodied includes a differentiator circuit which differentiates the output signals received from the pressure transducer 19 with respect to time when the signal processing means 24 are operative. The initial rate of fall of pressure which accompanies initial opening of one of the valves 58, 59 is effectively insensitive to other leakage from the respective cylinder and hence is an indication of the initial rate of air flow between that valve 58, 59 and its seat since the pressure regulator 11 maintains the pressure upstream of the calibrated restrictor 15 constant.Having regard to the limitation on speed of movement of the valve 58, 59 that follows from the facts that the valve 58. 59 is opened manually, the influence of rate of movement of the valve 58, 59 upon the rate of airflow between the valve 58, 59 and its valve seat during initial opening of the valve 58, 59 can be ignored at the air pressures employed. It follows that, ignoring the rate of movement of the valve 58,59, during initial opening of the valve 58, 59, there is a fundamental relationship between the distance by which the valve 58, 59 is displaced from its valve seat and the rate of air flow between that valve 58, 59 and its valve seat so that, during initial opening of the valve 58, 59, the output signal from the differentiator circuit is an indication of the distance between that valve 58, 59 and its valve seat.The output signal from the differentiator circuit is monitored and the third lamp 31 is energised when that signal indicates a rate of fall of pressure which is within a predetermined range, the upper limit of that range being the rate of fall of pressure that corresponds to the rate of flow of the initial air flow between the valve 58. 59 and its seat that occurs when the valve 58, 59 has been cracked initially and unseated sufficiently to allow air flow through the port, and the lower limit of that range being spaced from the upper limit by the amount that provides the maximum acceptable tolerance in setting the clearances of intake and exhaust valves.

The operator continues to manipulate the adjustment means on the rocker arms until the third lamp 31 is energised when he sets the respective valve 58, 59 and removes the setting gauge. He must readjust the rocker arm if the third lamp 31 should be deenergised before he stops adjustment and sets the valve 58. 59. A method for setting the clearance of an intake or exhaust valve 58. 59 as just described is illustrated in Figure 4.

The procedure is repeated for the other of the intake and exhaust valves 58 and 59 of the same cylinder 34 and then for each of the intake and exhaust valves 58 and 59 of the remaining cylinders of the engine.

One of the difficulties an operator must overcome when carrying out a method as just described and as illustrated in Figure 4 is that he does not have any indication of the proximity of the acceptance range when the third lamp 31 is de-energised. Accordingly we prefer to use a different form of signal processing means which is illustrated in Figure 5 and which includes a signal storage circuit 61 and a further comparator 62 instead of the differentiator circuit. The signal storage circuit 61 stores the signal from the pressure transducer 19 that led to energisation of the second lamp 29 and provides the further comparator 62 with a reference signal of the same magnitude as the signal it stores.The further comparator 62 compares the reference signal with the output signal emitted by the pressure transducer 19 whilst the valve 58. 59 is being opened by manipulation of the adjustment means on the respective rocker arm and transmits to a visual analog indicator 63 an analog signal which represents the difference between the reference signal and the output signal from the pressure transducer 19. The analog signal is displayed visually by the visual analog indicator 63 and is an analog indication of the instantaneous displacement of the valve 58, 59 from its seat.

The operator continues to adjust the adjustment means on the rocker arm associated with the displaced valve 58. 59 whilst watching the display presented by the visual analog indicator 63 and until he sees from the signal on the indicator 63 that the desired displacement of the valve 58, 59 from its seat has been achieved. The signal processing means would be adapted to energise the third lamp 31 for a range of output signals from the further comparator 62 that represents the acceptable tolerances on either side of the desired displacement of the valve 58, 59 from its seat. A method for setting the clearance of an intake or exhaust valve 58, 59 as just described with reference to Figure 5 is illustrated in Figure 6.

As before the setting gauge is removed once the desired clearance has been set and the procedure is repeated for the other valve 58, 59 of the respective cylinder 34 and for each of the other intake and exhaust valves of the engine.

The operator will use an oversize setting gauge when carrying out either of the methods for setting the clearance of an intake or exhaust valve which have been described above with reference to the drawings. The difference between the optimum setting gauge and the oversize setting gauge will compensate for the fact that air flow between the valve and its seat will not occur until shortly after initial cracking of that valve.

If an operator omits to ensure that the manual adjusters that are provided for adjusting the clearance between each intake or exhaust valve 5 & 59 and its associated rocker arm are slack, there is a risk that the valves 58 and 59 may be unseated before insertion of the setting gauge. Consequently the pressure at which substantially constant conditions are established in the cylinder 34, just after initial insertion of the probe 32 into the spark plug aperture 33. will be lower than if the valves 58 and 59 were seated. Hence. either the first lamp 28 vill be energised by the signal processing means 24 to indicate, probably incorrectly. that the engine should be rejected, or, when the second lamp 29 is energised, instead of being just a measure of leakage of air from the cylinder 34 when the valves 58 and 59 are seated, the reference signal provided for the further comparator 62 will be a measure of the total leakage of air from the cylinder 34 including that past the unseated valve 58.

59.

The form of signal processing means 24 which is described above with reference to Figures 5 and 6 and which is illustrated diagrammatically in Figure 5 can be modified to avoid the necessity for the operator to check that the manual adjusters are slack before he uses the apparatus to set the clearances for the intake and exhaust valves 58 and 59 of a cylinder 34 of the engine.

The modification is illustrated in Figure 7 and comprises the addition of an integrated circuit 64 and use of a modified signal storage circuit 61A which has an additional input. The input terminal 23 of the signal processing means 24 is connected in parallel to the first input terminal of the signal storage circuit 61a and to the input of the integrated circuit 64. There are two significant modifications to the signal storage circuit 61 which are embodied in the signal storage circuit 61A. Firstly, the signal storage circuit 61A is adapted to store the output signal from the transducer 19 when substantially constant pressure conditions are established in the cylinder 34 before insertion of the setting gauge. irrespective of whether or not the second lamp 29 is energised. Secondly provision is made in the signal storage circuit 61A for resetting the stored signal.

The integrated circuit 64 comprises a differentiator circuit 65 which has its input connected to the input terminal 23 and its output connected in parallel to the signal input terminal of each of two high gain comparators 66 and 67. A suitable constant electrical potential is applied to the other input terminal. of each comparator 66 and 67 and serves as the reference signal for the respective comparator 66, 67. The comparator 66 emits a pulsed output whenever the differentiator circuit 65 emits a positive output voltage signal and that pulsed output is fed to the additional input of the signal storage circuit 61A which is a reset signal input.

Signal storage circuit 61A responds to receipt at its reset signal input of a pulse of the pulsed output signal by cancelling the stored signal and by storing another signal which is the signal received at that instant at its first imput from the pressure transducer 19, that other signal being stored until the next pulse of the pulsed output signal is received at the reset signal input when it is replaced similarly. The comparator 67 emits an output signal when the differentiator circuit emits a negative output voltage signal and that output signal disenables further operation of the integrated circuit 64 to effect resetting of the signal stored by the signal storage circuit 61.

The operator will be able to insert the appropriate setting gauge between the end of the valve stem of each of the intake and exhaust valves 58 and 59 of each cylinder 34 if the manual adjusters for those valves are sufficiently slack when the probe 32 is inserted into the spark plug aperture 33. He will know that the engine should be rejected if he can so insert the appropriate setting gauge and the first lamp 28 is energised.

Also, if he can so insert the appropriate setting gauge and the second lamp 29 is energised, the procedure for setting the clearances for the valves 58 and 59 of that cylinder 34 will be just as is described above with reference to Figures 5 and 6, the differentiator circuit 64 being disenabled by the output from the comparator 67 that follows the initial fall in pressure in the cylinder 34 that accompanies initial opening of the valves 58 and 59.

Figure 8 shows that. if a valve 58, 59 is open when the probe 32 is inserted into the spark plug aperture 33, the pressure level at which the air flow conditions stabilise is lower than would be the case if both the valves 58 and 59 were seated. The operator must slacken off the adjusters and allow the unseated valve 58, 59 to seat before he can insert the appropriate setting gauge. The pressure in the cylinder 34 increases as the valve 58, 59 approaches its seat and then remains constant when the valve seats.

The signal storage circuit 61A initially stores a signal which is equivalent in magnitude to the pressure at which the air flow conditions stabilised initially with a valve 58, 59 open. The stored signal is increased incrementally as the pressure in the cylinder 34 increases whilst the valve 58, 59 closes, the incremental increase being effected by the pulsed output from the comparator 66 which follows the increase in pressure.

The clearances for the valves 58 and 59 of that cylinder 34 are then set by the procedure that has been described above with reference to figures 5 and 6, the differentiator circuit 64 being disenabled by the output from the comparator 67 that follows the initial fall in pressure in the cylinder 34 that accompanies initial opening of the valve 58, 59 after insertion of the appropriate setting gauge.

The pressure gauge 18 may be replaced by an analogue indicator which is connected to a suitable output of the signal processing means 24 and which is adapted to be activated by the output of the transducer 19, suitably processed by the signal processing means 24, to indicate the pressure in the tubing 14 downstream of the restriction 15.

It will be appreciated that the tapping 16 is blanked off when the analogue indicator is fitted instead of the pressure gauge 18.

WHAT WE CLAIM IS: 1. A method of monitoring the relative locations of a valve and a valve seat which

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. 59. The form of signal processing means 24 which is described above with reference to Figures 5 and 6 and which is illustrated diagrammatically in Figure 5 can be modified to avoid the necessity for the operator to check that the manual adjusters are slack before he uses the apparatus to set the clearances for the intake and exhaust valves 58 and 59 of a cylinder 34 of the engine. The modification is illustrated in Figure 7 and comprises the addition of an integrated circuit 64 and use of a modified signal storage circuit 61A which has an additional input. The input terminal 23 of the signal processing means 24 is connected in parallel to the first input terminal of the signal storage circuit 61a and to the input of the integrated circuit 64. There are two significant modifications to the signal storage circuit 61 which are embodied in the signal storage circuit 61A. Firstly, the signal storage circuit 61A is adapted to store the output signal from the transducer 19 when substantially constant pressure conditions are established in the cylinder 34 before insertion of the setting gauge. irrespective of whether or not the second lamp 29 is energised. Secondly provision is made in the signal storage circuit 61A for resetting the stored signal. The integrated circuit 64 comprises a differentiator circuit 65 which has its input connected to the input terminal 23 and its output connected in parallel to the signal input terminal of each of two high gain comparators 66 and 67. A suitable constant electrical potential is applied to the other input terminal. of each comparator 66 and 67 and serves as the reference signal for the respective comparator 66, 67. The comparator 66 emits a pulsed output whenever the differentiator circuit 65 emits a positive output voltage signal and that pulsed output is fed to the additional input of the signal storage circuit 61A which is a reset signal input. Signal storage circuit 61A responds to receipt at its reset signal input of a pulse of the pulsed output signal by cancelling the stored signal and by storing another signal which is the signal received at that instant at its first imput from the pressure transducer 19, that other signal being stored until the next pulse of the pulsed output signal is received at the reset signal input when it is replaced similarly. The comparator 67 emits an output signal when the differentiator circuit emits a negative output voltage signal and that output signal disenables further operation of the integrated circuit 64 to effect resetting of the signal stored by the signal storage circuit 61. The operator will be able to insert the appropriate setting gauge between the end of the valve stem of each of the intake and exhaust valves 58 and 59 of each cylinder 34 if the manual adjusters for those valves are sufficiently slack when the probe 32 is inserted into the spark plug aperture 33. He will know that the engine should be rejected if he can so insert the appropriate setting gauge and the first lamp 28 is energised. Also, if he can so insert the appropriate setting gauge and the second lamp 29 is energised, the procedure for setting the clearances for the valves 58 and 59 of that cylinder 34 will be just as is described above with reference to Figures 5 and 6, the differentiator circuit 64 being disenabled by the output from the comparator 67 that follows the initial fall in pressure in the cylinder 34 that accompanies initial opening of the valves 58 and 59. Figure 8 shows that. if a valve 58, 59 is open when the probe 32 is inserted into the spark plug aperture 33, the pressure level at which the air flow conditions stabilise is lower than would be the case if both the valves 58 and 59 were seated. The operator must slacken off the adjusters and allow the unseated valve 58, 59 to seat before he can insert the appropriate setting gauge. The pressure in the cylinder 34 increases as the valve 58, 59 approaches its seat and then remains constant when the valve seats. The signal storage circuit 61A initially stores a signal which is equivalent in magnitude to the pressure at which the air flow conditions stabilised initially with a valve 58, 59 open. The stored signal is increased incrementally as the pressure in the cylinder 34 increases whilst the valve 58, 59 closes, the incremental increase being effected by the pulsed output from the comparator 66 which follows the increase in pressure. The clearances for the valves 58 and 59 of that cylinder 34 are then set by the procedure that has been described above with reference to figures 5 and 6, the differentiator circuit 64 being disenabled by the output from the comparator 67 that follows the initial fall in pressure in the cylinder 34 that accompanies initial opening of the valve 58, 59 after insertion of the appropriate setting gauge. The pressure gauge 18 may be replaced by an analogue indicator which is connected to a suitable output of the signal processing means 24 and which is adapted to be activated by the output of the transducer 19, suitably processed by the signal processing means 24, to indicate the pressure in the tubing 14 downstream of the restriction 15. It will be appreciated that the tapping 16 is blanked off when the analogue indicator is fitted instead of the pressure gauge 18. WHAT WE CLAIM IS:

1. A method of monitoring the relative locations of a valve and a valve seat which

co-operate together to control induction and/or exhaust of a gaseous medium through a port in a wall of a chamber which has a potential gaseous medium leakage path separate from any such port, wherein fluid is caused to flow into the chamber, the fluid flow is monitored and an output signal is derived from a factor of that fluid flow which varies with movement of said valve relative to its valve seat and which is effectively uninfluenced by leakage from said chamber other than through said port, said output signal being used as an indication of the relative location of the valve and the valve seat.

2. A method according to Claim 1, wherein a substantially constant pressure is established within the chamber by air flowing into the chamber before the valve is moved relative to its valve seat and the output signal is derived.

3. A method according to Claim 2, wherein the output signal is an indication of rate of change of pressure of fluid flow to the chamber which accompanies movement of said valve relative to its valve seat after the establishment of such a substantially constant pressure in the chamber.

4. A method according to Claim 2, wherein the output signal comprises the difference between the rate of flow of fluid to the chamber at a given instant when the valve is unseated and the rate of flow of fluid to the chamber that prevailed when the valve was seated and the substantially constant pressure was established within the chamber.

5. A method according to Claim 4, wherein the output signal is presented in an analogue form on a visual indicator.

6. A method of setting an intake or exhaust valve of an internal combustion engine relative to the rocker arm with which it is associated in use in which the relative locations of the valve and its seat are monitored by a method according to any one of Claims 1 to 5.

7. Apparatus for monitoring the relative locations of a valve and a valve seat which co-operate together to control induction and/or exhaust of a gaseous medium through one port in a wall of a chamber which has a potential gaseous medium leakage path separate from any such port, the apparatus comprising a fluid source at which fluid is available at a controlled rate of flow and pressure, a conduit for conveying fluid from the fluid source to another port of the chamber, a transducer which is responsive to fluid flow through the conduit and the chamber when the conduit is connected to said other port and the apparatus is in use, the transducer having an outlet from which it emits an electrical signal which is a function of that fluid flow whereby that fluid flow is monitored, signal processing means and indicating means, the signal processing means having an input which is connected to the output of the transducer so as to receive an electrical signal which is emitted by the transducer, and an output which is connected to an input of the indicating means, the signal processing means being arranged to derive from the electrical signals received from the transducer an output signal which is a function of a factor of the fluid flow which varies with movement of said valve relative to its valve seat and which is effectively uninfluenced by leakage from said chamber other than through said one port, the indicating means being arranged to display the output signal as an indication of the relative locations of the valve and the valve seat.

8. Apparatus according to Claim 7, wherein the signal processing means comprise a differentiator circuit.

9. Apparatus according to Claim 8, wherein the signal processing means include a comparator as well.

10. Apparatus according to Claim 9, wherein the indicating means comprise one indicator which is operable by an output signal emitted by the comparator when the comparator indicates that the electrical signal received from the transducer is below a predetermined level.

11. Apparatus according to Claim 10, wherein the indicating means include two other indicators which are operable by output signals from the differentiator circuit when the comparator senses that the electrical signal emitted by the transducer ex ceeds the predetermined level, one of said other indicators being activated by an output signal from the differentiator circuit which indicates zero rate of change in the magnitude of the electrical signal received by the differentiator circuit from the transducer and the other of said other indicators being adapted to be actuated by an output signal from the differentiator circuit which indicates a negative rate of change in the output signal from the transducer within predetermined limits.

12. Apparatus according to Claim 11, wherein each of the three indicators is a visual indicator.

13. Apparatus according to Claim 12, wherein each indicator is a lamp.

14. Apparatus according to any one of Claims 7 to 13, wherein the transducer is adapted to respond to pressure of fluid in the conduit which is related to the rate of flow of fluid through the conduit.

15. Apparatus according to any one of Claims 7 to 14. wherein the signal processing means includes signal storage means and comparator means, the signal storage means being for storing a signal emitted by the transducer which indicates the establishment of substantially constant conditions of pressure within the conduit and the chamber, the comparator means being for comparing the signal stored by the signal storage means with the output signal of the transducer and for emitting an output signal which is conveyed to the indicator means, that output signal comprising the difference between the signal stored by the signal storage means and the output signal from the transducer with which it is compared, and the indicating means including analogue display means for displaying the output signal received from the comparator continuously.

16. Apparatus according to any one of claims 7 to 15, including a probe fitted to one end of the conduit and for insertion into said other port, the probe comprising a valve head, a tubular body and a twoposition rotary shut-off valve in the valve head, the valve head forming an inlet port to which said one end of the conduit is connected and an outlet port which communicates with the bore of the tubular body. the two-position rotary shut-off valve being adapted to allow communication between the inlet and the outlet in one of its two positions and to shut off such communication in its other position. the probe carrying an annular collar of deformable material, which abuts an annular shoulder which is formed at the end of the tubular body remote from the valve head, and a tubular sleeve which is slidable upon the outer surface of the tubular body. the rotary valve carrying lever operable cam means outside the valve head, the cam means co-operating with a follower surface formed at the end of the tubular sleeve remote from the collar.

the arrangement being such that the collar is in its relaxed condition when the valve is in said other position to shut off communication between the inlet and the outlet so that, when said end of the probe and the collar are inserted into the other port of the chamber and the lever operable cam means are rotated to rotate the rotary valve from said one position to the other position to open communication between the inlet and the outlet of the valve head to allow fluid to flow through the probe into the chamber, the cam means force the tubular sleeve towards said end of the probe so as to deform the collar and effect a fluid tight seal between the probe and said other port when the rotary valve member is in said other position.

17. Apparatus according to claim 15 or claim 16 when appended to claim 15, including differentiating means for differentiating with respect to time the signal that is emitted by the transducer once substantially constant pressure conditions have been established within the conduit and the chamber, and first and second comparator means associated with the differentiating means, the first comparator means being adapted to compare the differentiation of the signal that is emitted by the transducer with a reference and to emit an output signal when the differentiated signal is positive, the output signal from the first comparator means being adapted to effect cancellation of the signal that is stored by the signal storage means and storage of a fresh output signal from the transducer in its place, and the second comparator means being adapted to compare the differentiation of the signal that is emitted by the transducer with a reference signal and to emit an output signal when the differentiated signal is negative, such as output signal from the second comparator means being adapted to disenable further operation of the differentiating means.

18. A method of setting an intake or exhaust valve of an internal combustion engine relative to the rocker arm with which it is associated in use substantially as described hereinbefore with reference to Figures 1 to 4 or Figures 1 to 3, 5 and 6 of the accompanying drawings, or Figures 1 to 3, 5 and 6 of the accompanying drawings modified substantially as described hereinbefore with reference to Figures 7 and 8 of the accompanying drawings.

19. Apparatus for setting an intake or exhaust valve of an internal combustion engine relative to the rocker arm with which it is associated in use substantially as described hereinbefore with reference to Figures 1 to 4 and as illustrated in Figures 1 to 3 of the accompanying drawings, or substantially as described hereinbefore with reference to Figures 1 to 3, 5 and 6 and as illustrated in Figures 1 to 3 and 5 of the accompanying drawings, or substantially as described hereinbefore with reference to Figures 1 to 3, 5 and 6 and modified substantially as described hereinbefore with reference to Figures 7 and 8 and as illustrated in Figures 1 to 3 and 7 of the accompanying drawings.