WO2008023207A1

WO2008023207A1 - Apparatus for adjusting the valve stroke in an internal combustion engine

Info

Publication number: WO2008023207A1
Application number: PCT/HU2006/000067
Authority: WO
Inventors: Gyula Toth; József MERCZ
Original assignee: Ricardo Deutschland Gmbh
Priority date: 2006-08-22
Filing date: 2006-08-22
Publication date: 2008-02-28

Abstract

The valve stroke adjusting unit (21) comprises a lifting member (22) having a profiled valve lifting surface (28) resting on the actuating surface (69) of the single-arm rocker (6) and a bore (24) which is arranged on a first shaft surface (26) of the camshaft (17), said lifting member (22) having a profiled moving surface (29), a motion transmitting lifting lever (30) having a first arm (31) and a second arm (32), said first arm (31) being in contact with the profiled moving surface (29) of the lifting member (22), said second arm (32) being in contact with the outer surface (19) of the lifting cam (18) of the camshaft (17), and a stroke adjusting element (37) having a pin (36) on which the motion transmitting lifting lever (30) is arranged in a turnable way, said stroke adjusting element (37) being arranged by its bore (38) on a second shaft surface (39) of the camshaft (17) and having a turning member (40) linked to a stroke control member (45) actuated by an engine controller.

Description

Apparatus for adjusting the valve stroke in an internal combustion engine

TECHNICAL FIELD

The present invention relates to an apparatus for adjusting the valve stroke in an internal combustion engine, mainly in a spark ignition pistone engine of a vehicle, by which any rate between minimum stroke and maximum stroke can be adjusted. Therefore, the apparatus is suitable for controlling Otto engines without a throttle valve.

BACKGROUND ART

In the case of Otto engines, a factor causing loss is the output regulating throttle valve in the intake pipe which, as a result of the resistance caused by said valve, limits the volume of air introduced into the combustion space of the engine. The output regulating function may also be attained by varying the opening period and lifting height of the intake valve, with losses much lower than those of the solution mentioned before. In certain prior art regulation approaches, the angular position of the maximum valve lift is constant vis-a-vis the crankshaft while the valve stroke is varying.

Such a solution is disclosed in patent document EP 1 039 103 B1 where a common camshaft performs valve lifting, the extent of which is influenced by a valve lift varying mechanism which is in an actuating relationship with a single- arm rocker.

In patent document DE 101 55 007 A1 a mechanism is described in which there is a valve lift varying mechanism arranged between the valve lifting camshaft and a single-arm rocker, and the mechanism runs on bearings on a separate shaft and is fitted with regulating members.

Patent document WO 2004/009967 A1 discloses a variable stroke valve lifting mechanism which has a compact construction, needs a small space and is applicable for DOHC engines of cars. In another design of the valve lift varying mechanism, the place of maximum valve lift changes simultaneously with varying the valve stroke and the angular position of valve opening remains approximately unchanged, as a result of which the angular position of the maximum valve lift is displaced towards the angular position of valve opening that can be considered to be unchanged. A mechanism having such operating characteristics is described in patent document US 6 019 076 relating to a multi-pivot mechanism arranged around the camshaft. This approach results in unfavourable characteristics due to the noise level during operation and to wear and tear stemming from prolonged use.

DISCLOSURE OF INVENTION

The objective of the present invention is to create an apparatus which ensures a valve stroke steplessly variable between minimum and maximum values, without the occurrence of a phase shift in valve lifting, consequently by keeping the angular position of valve opening approximately constant. The space required by this apparatus is small, it has a favourable orientation from the aspect of cylinder head design, and it includes less components and joining points than prior art solutions. It is to be taken into consideration in meeting said objective that, in order to be used, the apparatus should fit in the cylinder head space of car engines produced currently in mass production. The more recent designs have double camshafts and four valves (DOHC) which are quite bulky, and there is hardly any chance to install an apparatus which makes the cylinder head even bulkier.

Our objectives have been met by an apparatus arranged around the camshaft and by actuating a single-arm rocker through a turning lifting member that is moved by a two-arm lever. For applications in multi-cylinder engines, the lifting member is preferably assembled from two halves.

Thus, the present invention relates to an apparatus for adjusting the valve stroke in an internal combustion engine, comprising a camshaft actuating the valve by a lifting cam, a single-arm rocker having a turning end adjoined to the stem end of the valve, an actuating surface and a substantially unmoveable support, and a spring-loaded valve stroke adjusting unit operatively arranged between the lifting cam and the actuating surface of the single-arm rocker. According to the invention, the valve stroke adjusting unit comprises a lifting member having a profiled valve lifting surface resting on the actuating surface of the single-arm rocker and a bore which is arranged on a first shaft surface of the camshaft, said lifting member having a profiled moving surface, a motion transmitting lifting lever having a first arm and a second arm, said first arm being in contact with the profiled moving surface of the lifting member, said second arm being in contact with the outer surface of the lifting cam of the camshaft, and a stroke adjusting element having a pin on which the motion transmitting lifting lever is arranged in a turnable way, said stroke adjusting element being arranged by its bore on a second shaft surface of the camshaft and having a turning member which is linked to a stroke control member actuated by an engine controller.

In a preferred embodiment, the motion transmitting lifting lever is a two-arm lever, the first arm and second arm of which include an angle of approximately 90 degrees, the first arm has a first contact surface being in contact with the profiled moving surface of the lifting member, and the second arm has a second contact surface being represented by an outer surface of a roller arranged on a pin fixed in the second arm.

In another preferred embodiment, the actuating surface of the single-arm rocker is represented by the outer surface of the roller arranged on a pin fixed in the single-arm rocker.

In a further preferred embodiment, the stroke control member is a control shaft, the turning member of the stroke adjusting element is a radial cut-out open outwards with parallel side surfaces, to which an outer surface of a roller arranged on a pin is fitted without any clearance, the pin is fixed in a control arm fixed to the control shaft, and the axis of the control shaft is parallel with the geometric axis of the camshaft.

In a still further preferred embodiment, the valve lifting surface has generatrices which are straight lines parallel with the geometric axis of the camshaft, and the curvature radius associated with any tangent thereof is larger than the curvature radius associated with any tangent thereof is larger than the curvature radius associated with the tangent of the actuating surface of the single-arm rocker.

In a further preferred embodiment, the lifting member has a lower lifting member half and an upper lifting member half which are secured to each other by a bolt joint, embracing the first shaft surface of the camshaft.

In a further preferred embodiment, in the case of two neighbouring valves, each of them has a single-arm rocker, a lifting member and a motion transmitting lifting lever assigned thereto, and the two motion transmitting lifting levers are arranged on a pin of a common stroke adjusting element.

In a further preferred embodiment, between the stroke adjusting element and the lifting member there is a tensioning spring designed as a hairpin spring, a wound part of which is arranged on the pin of the stroke adjusting element, a bent first end of the hairpin spring is supported by a groove of the lifting member, and a bent second end thereof rests on a spring support pin of the stroke adjusting element.

In a further preferred embodiment, the radius of the bore, embedding the camshaft, of the stroke adjusting element is equal with or larger than the distance between a cam tip of the valve lifting cam and the geometric axis of rotation of the camshaft.

In a still further preferred embodiment, the radius of the bore, embedding the camshaft, of the lifting member is equal with or smaller than the base circle radius of the valve lifting cam.

It is a substantial benefit of the apparatus according to the present invention that the camshaft carries the valve stroke adjusting device and the radius of shaft surfaces of the camshaft is only slightly larger than the distance of the cam lifting tip from the geometric axis of rotation, which results in favourable access for installation.

BRIEF DESCRIPTION OF DRAWINGS A preferred embodiment of the apparatus according to the present invention will be described below on the basis of the accompanying drawings, where

Fig. 1 is a pictorial schematic view of an exemplary embodiment of the apparatus according to the invention,

Fig. 2 is a view of the embodiment as shown in Fig. 1 taken according to the arrow K, and

Fig. 3 shows movement diagrams of the valve lifting with various valve stroke values.

DESCRIPTION OF PREFERRED EMBODIMENT

In Figs. 1 and 2 an embodiment of the apparatus according to the invention is shown which is a mechanism capable of actuating for example two intake valves or exhaust valves of a cylinder head with four valves and two camshafts (DOHC), where the camshafts run on bearings in the cylinder head and the spark plug, not shown, has a central location. The engine is of the Otto type. The apparatus adjusting the valve stroke makes it unnecessary to apply a throttle valve in the intake pipe for regulating the engine output.

In Fig. 1 only a pair of intake valves 2 and 2A of one cylinder are shown, and the apparatus 1 according to the invention will be described with respect to the valve 2. The apparatus for actuating the valve 2A is of the same construction.

The apparatus 1 actuates the intake valve 2 of a cylinder not shown in the direction of its valve stem 4 in a variable stroke length against a valve spring 70 which is adjoined to the valve stem 4 via a valve spring retainer 72 and a valve spring key 71. The other intake valve 2A of the cylinder is actuated in the same manner. The valve stem 4 has an end 5 that is in touch with a pressure surface 8 arranged at a first end 7 of a single-arm rocker 6. The geometric axis of rotation of the single-arm rocker 6 is defined by a support formed as a bearing shell 10 located at its second end 9. The bearing shell 10 is fitted to a ball head 11 of a hydraulic lash adjuster 12. The bearing shell 10 held by the hydraulic lash adjuster 12 constitutes a substantially unmoveable support for the single-arm rocker 6 during operation. At the central part of the single-arm rocker 6, there is a roller 15 with an outer surface 16, running on a bearing on a pin 14 secured in a bore 13 of the single-arm rocker 6, said outer surface 16 constituting an actuating surface 69 of the single-arm rocker 6.

A valve stroke adjusting unit 21 is arranged between the outer surface 16 of the single-arm rocker 6 and a lifting cam 18 of a camshaft 17 for actuating the valve 2, by which the rate of the valve stroke can be varied on a stepless basis between approximately zero and the maximum value.

As it is shown in Fig. 1 , the camshaft 17, in a per se known manner, has a lifting cam 18 with an outer surface 19 and a cam tip 20. On the camshaft 17, adjacent to the lifting cam 18, there is a shaft surface 39. On the other side of the shaft surface 39, there is another similar lifting cam 18A. The lifting cams 18 and 18A are for controlling a pair of inlet valves, not shown, belonging to a further cylinder of the engine, said further cylinder being adjacent to the cylinder of the pair of valves 2 and 2A. The lifting cams actuating the valves 2 and 2A, which cannot be seen in Figs. 1 and 2, are designed in the same manner as the lifting cams 18 and 18A, and the shaft surface therebetween has the same design as that of the shaft surface 39. Therefore, in the following description of the lifting of the valve 2 reference will be made to the lifting cam 18, the outer surface 19, the cam tip 20 and the shaft surface 39.

The valve stroke adjusting unit 21 comprises a lifting member 22 the axis of rotation of which is identical with the geometric axis of rotation of the camshaft 17. The lifting member 22, having a hub part 23 with a bore 24, is arranged in a turnable way on a shaft surface 26 of the camshaft 17. The lifting member 22 has a nose part 25 protruding from the hub part 23. The hub part 23 has a cylindrical outer surface 27 to which, according to the figure, the lower valve lifting surface 28 of the nose part 25 is continuously adjoined, the latter surface constituting a support surface for the roller 15 of the single-arm rocker 6. According to the figure, the upper moving surface 29 of the nose part 25 represents a support surface for a contact surface 33 on a first arm 31 of a motion transmitting lifting lever 30, said contact surface 33 constituting a pressure surface. The motion transmitting lifting lever 30 has a second arm 32 with a bore 34. There is a pin 73 fixed in the bore 34 and a roller 74 is arranged on the pin 73, said roller 74 having an outer surface 75 which rests on the outer surface 19 of the lifting cam

18 of the camshaft 17.

The motion transmitting lifting lever 30 is designed as a two-arm lever, where the first arm 31 and the second arm 32 include an angle of approximately 90 degrees, and has a bore 35 in its central part by which it is turnable arranged to a pin 36. The pin 36 is secured, preferably welded, to a stroke adjusting element 37 having a bore 38 which is arranged on the shaft surface 39 of the camshaft 17. The stroke adjusting element 37 has a turning member, formed as a radial cut-out 40 open outwards, to the side surfaces 41 of which an outer surface 78 of a roller 77 arranged on a pin 76 is fitted without any clearance. The pin 76 is secured in a bore 43 of a control arm 42. The control arm 42 has a bore 44 by which it is secured on a stroke control member formed as a control shaft 45, the latter being in a rotational relationship with the engine control unit, not shown.

In the apparatus 1 , it is to be ensured that, also at the valve stroke of minimum rate, an outer surface 75 of a roller 74 is supported by the outer surface

19 of the lifting cam 18 of the camshaft 17, said roller 74 being arranged on a pin 73 of the second arm 32 of the motion transmitting lifting lever 30. To this end, there is a hairpin spring 46, a first end 47 of which is supported in a groove 48 of the lifting member 22 and a second end 49 thereof is supported by a pin 50 secured in the stroke adjusting element 37. A wound part 51 of the hairpin spring 46 surrounds the pin 36 with an annular clearance 52 that enables a free adjustment of the hairpin spring 46. The pin 36 makes sure that the hairpin spring 46 may not fall into the cylinder head when it becomes loose or broken.

The apparatus 1 is of a design suitable for a multi-cylinder engine. Therefore, the lifting member 22 consists of two halves. The valve lifting surface 28 is on the lower lifting member half 53 and the moving surface 29 is on the upper lifting member half 54. In the lifting member 22, the lower lifting member half 53 and the upper lifting member half 54 are adjoined to one another by a groove 55 and an adjoining rib 56, they are clamped by a socket-head bolt 57. In the upper lifting member half 54 there is a threaded bore 58 in which the bolt 57 guided through a bore 59 is located, said bolt 57 pressing the division surface 60 of the lower lifting member half 53 and the division surface 61 of the upper lifting W

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member half 54 against each other. The valve lifting surface 28 is designed on the lower lifting member half 53 and generatrices of said valve lifting surface 28, for example the generatrix 66, are straight lines parallel with the geometric axis of the camshaft 17, and the curvature radius associated with any tangent thereof is larger than the curvature radius associated with the tangent of the actuating surface 69 of the single-arm rocker 6.

The shape of the valve lifting surface 28 is selected to ensure that the valve lift S of the intake valve 2 relative to the turning angle φ of the camshaft 17 provides the characteristic curves A to F as shown in Fig. 3, where the lifting and releasing portions of the curves are symmetric, and the angular position of valve opening is substantially independent from the turning angle φ of the camshaft 17. Accordingly, the valve lifting surface 28 has a first section 62 at the hub part 23 by which no valve lifting occurs. In the valve lifting surface 28 there are a second section 63 connected to the first section 62 and a third section 64 connected to the second section 63, said second and third sections being located at the nose part 25. The second section 63 determines the initial phase of the valve lift when the hydraulic lash adjuster 12 is slightly compressed so that it reaches its stable position. The third section 64 determines a further phase of the valve lift, up to the maximum lift.

The moving surface 29 of the lifting member 22 is designed in the upper part of the upper lifting member half 54, as shown in the figures, and in the plane perpendicular to the axis of rotation of the camshaft 17, its profile 67 is designed in view of velocity and acceleration rates permissible in the apparatus 1.

In the exemplary embodiment shown, the bore 38 of the stroke adjusting element 37, which bore 38 is fitted to the shaft surface 39 of the camshaft 17, has a slightly larger radius than the distance between the cam tip 20 of the valve lifting cam 18 and the geometric axis of rotation of the camshaft 17. The radius of the bore 24 of the lifting member 22, fitted to the shaft surface 26 of the camshaft 17, is slightly smaller than the base circle radius of the valve lifting cam 18.

To make sure that the second arm 32 of the motion transmitting lifting lever 30 makes a minimum influence on the axial space requirement of the apparatus 1 , the lifting member 22 has a corner cut-out 68 which provides free space for the moving of the second arm 32.

The apparatus 1 according to the embodiment shown in Figs. 1 and 2 operates as follows.

The apparatus 1 as shown in Fig. 1 is in a position corresponding to the maximum rate valve lift, i.e. the valves 2 and 2A are displaced so that the largest valve opening is achieved.

The stroke adjusting element 37 is in its extreme position, and the lifting cam 18 lifts while rotating the second arm 32 of the motion transmitting lifting lever 30 via the roller 15, turning this and together with it the first arm 31 around the pin 36. The outer surface 16 of the roller 15 is pressed by the hairpin spring 46 against the outer surface 19 of the lifting cam 18. Through its contact surface 33, the first arm 31 of the motion transmitting lifting lever 30 presses down the moving surface 29 of the lifting member 22 and, therefore, the lifting member 22 is turned clockwise, as a result of which the second section 63 and then the third section 64 of the valve lifting surface 28 press down the single-arm rocker 6 via the roller 15 arranged on the pin 14 therein. By means of its pressure surface 8, the single-arm rocker 6 pushes the end 5 of the valve stem 4 to the rate of the largest valve stroke, and then turning round, the lifting cam 18 resets the motion transmitting lifting lever 30 via the cam tip 20, as a result of which the lifting member 22 turns back in an opposite direction reseting the single-arm rocker 6, and the valve stem 4 and the valve 2, respectively, are moved back until they close.

As against the position shown in Fig. 1 , by turning clockwise the control shaft 45 and the control arm 42, respectively, i.e. by releasing the accelerator, the stroke adjusting element 37 turns anti-clockwise, and together with it turns the pin 36, the motion transmitting lifting lever 30, and the lifting member 22 anticlockwise whereby the first section 62 of the valve lifting surface 28 is in contact with the outer surface 16 of the roller 15 arranged on the pin 14 in the single-arm rocker 6. In this position of the stroke adjusting element 37, when the camshaft 17 turns, the lifting cam 18 lifts during its rotation via the roller 74 the motion transmitting lifting lever 30, which is pressed on the outer surface 19 of the lifting cam 18 by the hairpin spring 46, and the motion transmitting lifting lever 30 turns the lifting member 22.

The first section 62 of the valve lifting surface 28 does not cause any valve lift in any angle position of the lifting member 22. The second section 63 and the third section 64 of the valve lifting surface 28 press down the single-arm rocker 6 as a result of turning, through the roller 15 arranged on the pin 14 therein. The angular displacement of the lifting member 22 determined by the lifting cam 18 is constant irrespective of the valve stroke. The rate of the valve stroke depends on how large is that part of the first section 62 which actuates the roller 15 at its outer surface 16 during operation.

Fig. 3 shows the valve lift S as a function of the turning angle φ of the camshaft 17. In Fig. 3 there are six valve lifting curves A to F, of which F is the curve of the largest valve stroke. For the curves E to A, the rate of valve stroke is gradually smaller. As shown by the curves A to F, the starting of the valve lift is within narrow limits, i.e. it starts in an approximately identical angular position, the maximum valve lift is reached in different angular positions, and the angular interval between the starting of the lift and the finishing of the valve lifting is widened by increasing the valve stroke.

While the invention has been described by reference to a preferred embodiment, it should be understood that a number of changes could be made by the person skilled in the art within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiment, but that it have the full scope as defined by the following claims.

Claims

1. An apparatus for adjusting the valve stroke in an internal combustion engine, comprising a camshaft (17) actuating the valve (2, 2A) by a lifting cam (18), a single-arm rocker (6) having a turning end (7) adjoined to the stem end (5) of the valve (2), an actuating surface (69) and a substantially unmoveable support (10), and a spring-loaded valve stroke adjusting unit (21) operatively arranged between the lifting cam (18) and the actuating surface (69) of the single-arm rocker (6), c h a ra cte rized in that the valve stroke adjusting unit (21) comprises a lifting member (22) having a profiled valve lifting surface (28) resting on the actuating surface (69) of the single-arm rocker (6) and a bore (24) which is arranged on a first shaft surface (26) of the camshaft (17), said lifting member (22) having a profiled moving surface (29), a motion transmitting lifting lever (30) having a first arm (31) and a second arm (32), said first arm (31) being in contact with the profiled moving surface (29) of the lifting member (22), said second arm (32) being in contact with the outer surface (19) of the lifting cam (18) of the camshaft (17), and a stroke adjusting element (37) having a pin (36) on which the motion transmitting lifting lever (30) is arranged in a tumable way, said stroke adjusting element (37) being arranged by its bore (38) on a second shaft surface (39) of the camshaft (17) and having a turning member (40) linked to a stroke control member (45) actuated by an engine controller.

2. The apparatus according to claim 1 , characterized in that the motion transmitting lifting lever (30) is a two-arm lever, the first arm (31) and the second arm (32) of which include an angle of approximately 90 degrees, the first arm (31) has a first contact surface (33) being in contact with the profiled moving surface (29) of the lifting member (22), and the second arm (32) has a second contact surface being represented by an outer surface (75) of a roller (74) arranged on a pin (73) fixed in the second arm (32).

3. The apparatus according to any of claims 1 and 2, characterized in that the actuating surface (69) of the single-arm rocker (6) is represented by an outer surface (16) of a roller (15) arranged on a pin (14) fixed in the single-arm rocker (6).

4. The apparatus according to any of claims 1 to 3, characterized in that the stroke control member is a control shaft (45), the turning member of the stroke adjusting element (37) is a radial cut-out (40) open outwards with parallel side surfaces (41), to which an outer surface (78) of a roller (77) arranged on a pin (76) is fitted without any clearance, the pin (76) is fixed in a control arm (42) fixed to the control shaft (45), and the axis of the control shaft (45) is parallel with the geometric axis of the camshaft (17).

5. The apparatus according to any of claims 1 to 4, characterized in that the valve lifting surface (28) has generatrices (66) which are straight lines parallel with the geometric axis of the camshaft (17), and the curvature radius associated with any tangent thereof is larger than the curvature radius associated with the tangent of the actuating surface (69) of the single-arm rocker (6).

6. The apparatus according to any of claims 1 to 5, characterized in that the lifting member (22) has a lower lifting member half (53) and an upper lifting member half (54) which are secured to each other by a bolt joint (57), embracing the first shaft surface (26) of the camshaft (17).

7. The apparatus according to claim 1 , characterized in that, in the case of two neighbouring valves (2, 2A), each of them has a single-arm rocker (6), a lifting member (22) and a motion transmitting lifting lever (30) assigned thereto, and the two motion transmitting lifting levers (30) are arranged on a pin (36) of a common stroke adjusting element (37).

8. The apparatus according to claim 1 , characterized in that between the stroke adjusting element (37) and the lifting member (22) there is a tensioning spring designed as a hairpin spring (46), a wound part (51) of which is arranged on the pin (36) of the stroke adjusting element (37), a bent first end (47) of the hairpin spring (46) is supported by a groove (48) of the lifting member (22), and a bent second end (49) thereof rests on a spring support pin (50) of the stroke adjusting element (37).

9. The apparatus according to claim 1, characterized in that the radius of the bore (38), embedding the camshaft (17), of the stroke adjusting element (37) is equal with or larger than the distance between a cam tip (20) of the valve lifting cam (18) and the geometric axis of rotation of the camshaft (17).

10. The apparatus according to claim 1, characterized in that the radius of the bore (24), embedding the camshaft (17), of the lifting member (22) is equal with or smaller than the base circle radius of the valve lifting cam (18).