GB2296769A - Tachograph - Google Patents

Abstract

A tachograph for recording vehicle speed is provided with a recording mechanism that facilitates easy alignment of the recording stylus (not shown) with the base line of the speed scale of a tachograph disc (not shown) corresponding with a measured vehicle speed of zero. The stylus is indirectly connected to a carrier (46) which is axially displaceable by an amount related to the measured vehicle speed. The carrier (46) has projections (47, 48) which abut with one of several eccentric stops (49, 50). By rotating the stops (49, 50), the axial position of the carrier (46), and therefore the stylus when the measured value is zero, may be adjusted. The stops (49, 50) are integrally moulded onto a base plate with enough friction for them to be rotatably self locking and resistant to vibrational movement and each of the stops can be broken off in order to use the mechanism over a greater range. <IMAGE>

Description

Tachograph This invention relates to a tachograph in general and more particularly to a recording system there for.

Tachograph recording, that is the recording of at least the speeds at which a motor vehicle has been travelling, the distances covered and the various working times, as well as a driver's break periods, serve not only for assessing the economical utilisation of a vehicle, but also for accident evaluation and, in the case of traffic checks, for veritin whether traffic regulations have been observed.

In view of the above, it is necessary, particularlx for the accurate recording of vehicle speed, that correct positioning of the circular lines of the speed scale printed on a tachograph disc ith the recording stylus used for marking the disc is obtained. Owing to various production and assembly tolerances, particularlx in the case of those tachographs in which a) the tachograph discs are associated with a support movable relative to the device housing and, b) carriers of the recording styluses of the tachograph are displaceably mounted in the housing, correct alignment may not always be readily achieved after the assembly of a tachograph.

This means that it is necessary, subject to setting the steepness of the characteristic curve of the speed-measuring system position accuratel! the speedrecording stylus on a speed-scale circle. Preferably this "ill be on the base line of the speed-scale which corresponds to the quantit, being monitored having a value of zero. Such an adjustment generally requires considerable effort to obtain the correct alignment.

The calibration method customarily used to determine the desired position of the speed-recording stylus involves making a test recording. To perfonn an adjustment either the speed-measuring mechanism can be turned in a suitable elongated-hole fastening or the holder of the speed-recording stylus can be bent.

This usually makes it necessary to perform repeated test runs and involves repeated opening and closing of the tachograph. Such an adjustment method, which requires a large number of manipulations, the results of which depend on the skill and care of the person performing the adjustments, is time-consuming.

The time required to adjust each unit cannot be planned and therefore the adjustment stage cannot be directly incorporated into the production flow of a large-scale production process.

The object of the present invention is to provide a mechanism for use in a tachograph which reduces the adjusting effort required to obtain the correct positioning of the recording stylus, in particular to simplif the means required for the adjustment and to make the adjusting procedure more effective.

According to the present invention there is provided a tachograph for recording at least one measured parameter and having its recording system arranged on a mounting plate and further comprising: a drivable carrier serving to move a recording stylus: and at least one stop means co-operable with the carrier so that when the value of the measured parameter is zero the carrier engages a peripheral surface of the stop means, wherein the stop means is rotatably mounted on the mounting plate and the peripheral surface thereof is eccentric relative to its axis of rotation.

Preferred embodiments of the present invention are defined in the subclaims.

A particular advantage which the invention offers is that adjusting measures, such as bending the holder of the speed-recording stylus, with, inter alia, the uncertainty as to the mechanical hysteresis, or displacing the speedmeasuring mechanism, making it necessary to loosen and re-tighten at least two screwed connections at each adjusting operation, can be avoided.

A further advantage is that the stop means, provided in accordance with the invention, for adjusting the zero position of the speed recording system, can be moulded as an integral part, preferably by injection moulding direction onto or into the mounting plate of the recording system, the stop means having the required rotatability and a self-locking action to render either a separate mounting for the stop or a clamping stage for example by means of using a screes, as being unnecessary after the adjustment procedure. In addition, the invention makes it feasible to manufacture only one mounting plate which is suitable for use utith all the required various measuring ranges.This means that zero positions of all the various measuring ranges of the recording stylus can be adjusted either using a single, suitably constructed stop means or, at least two adjustable stop means may be provided, of which the stop means provided for the smaller measuring range or ranges can be removed in a simple manner, preferabl! without tools.

It should also be noted that, in the same way, it is also possible to adjust the zero position of a recording system provided for recording the engine speeds, if a tachograph is additionally equipped with such a recording system The invention will be explained in greater detail below with reference to the accompanying drasvings, in which:: Fig. 1 shows a plan view of a recording system made in accordance s ith the invention of a tachograph in its zero position using one stop means, Fig. 2 shows a sectional representation of the fastening point of the stop means in the direction of the arrow A in Fig. 1, Fig. 3 shows a partial representation of an alternative embodiment of the recording system according to Fig. 1 using at least two stop means associated with different measuring ranges, Fig. 4 shows a side view of the alternative embodiment according to Fig. 3 in the direction of the arrow B, Fig. 5 shows a partial sectional representation of the alternative embodiment according to Fig. 3, Fig. 6 shows a further exemplary embodiment relating to the construction of an adjustable stop means.

The recording system 1 as illustrated in Figure 1 is preferably emploved in tachographs in which a tachograph disc 2 can either be automaticallv drawn in and brought out of the recording system or is associated xvith a drawer or a carrier which can be displaced or swivelled parallel to a mounting plate ; which carries the recording system 1. The invention can, however, also be implemented in tachographs in which the clockwork mechanism and the centring and driving arbor associated with the tachograph discs are arranged in a swing-open cover. in contrast to the first-mentioned types of tachograph, these tachographs are T;noxvn to offer the advantage that in order to change a tachograph disc, it is unnecessar) to lift and lower the recording styluses or the tachograph disc support when the latter is in the recording position. What is essential in this case is that the tachograph, after mounting the recording system 1 so as to be ready for operation, is open at the rear allowing adjustment of the recording system 1 to be effected.

In Figure 1, 4 denotes a centring and driving arbor, of which the timesynchronous drive (not illustrated) is arranged, for example, in the bottom 5 of a drawer. 6, 7, 8 and 9 denote holders moulded as integral parts, preferably by injection moulding on the mounting plate 3 and of which one holder pair 6, 7 serves for the fastening of a guide rod 10. In the other holder pair 8, 9 there is positioned as eccentric shaft or eccentrically mounted shaft 11. The shaft can be driven by a positioning motor (not illustrated) via gears 12, 13 and 14 and comprises, in the exemplary embodiment illustrated, a cylindrical rod 15 which is eccentrically received in drivers 16 and 17 mounted in the holders 8 and 9. In this arrangement, the gear 12 is associated with the driver 16.A cut-out 18 provided in the mounting plate 3 allows the centring and driving arbor 4 to project into the plane of the mounting plate 3, so that the mounting plate 3 acts as a holding-down device for the tachograph disc 2. It is also apparent from Figure 1 that a carrier 19 is displaceably mounted on the guide rod 10. Formed on the carrier 19 is an arm 20 schich extends b! a finger 21 into the vicinity of the eccentric shaft 11. In addition, a spring 22 is secured to the arm 20 in order to bias the arm in the direction of the disc 2, and a recording stylus 23 is fastened to the said arm, to be precise to a limb of the arm 20, not visible in Figure 1 engaging under the rod 15 of the eccentric shaft 11.For the sake of completeness, it should also be noted that one leg 24 of the spring 22 is alias supported on the arm 20, whereas the other leg 25 lies against the eccentrically mounted rod 15. When the eccentric shaft 11 is rotated with the purpose of lowering the recording stylus 23 onto the tachograph disc 2, the spring 22 serves as a sprung driver to supply a recording force to bias the arm and stylus in the direction of the disc. In contrast to this, the finger 21 has the task of serving, after a certain amount of play, as a driver for lifting the recording stylus 23 off from the tachograph disc 2 when the eccentric shaft 11 is further rotated.

The carrier 19 is displaced along the guide rod 10 by an amount relating to the magnitude of the measured parameter. The carrier 19 is driven by a stepper motor 26 which is fastened to the mounting plate 3 b' means of screws 27 and 28 on suitable supports. The carrier 19 can also be rotated to a small extent about a longitudinal axis of the rod 10.

A pinion 29, which is fastened on the drive shaft of the motor pointing towards the mounting plate 3, meshes with a gear 30 which is formed as one piece with a gear 31. The latter is in engagement with teeth 32 fonned on the carrier 19. A cut-out 33 provided in the mounting plate 3 makes it possible not only for the recording stylus 23 to reach through onto the tachograph disc 2, but also for the carrier 19 to penetrate into the plane of the mounting plate 3, thereby allowing a substantially more compact construction.

A stop 40 in the form of a disc-like body has a uniform circular periphery 39 and is mounted on the plate 3 about a non central axis thus allowing the stop to undergo eccentric rotational movement.

The tachograph disc 2 illustrated in Figure 1 is provided, in customary\ fashion, with a printed scale designed for a recording period of 24 hours, of which, for simplicit, only time scales 34, 3e and speed-scale circles are illustrated, one of which is denoted by 36. 37 denotes a concentric line representing the zero line of the speed recordings which is recorded bs the recording stylus 23 when the canier 19 abuts the periphen 39 of the stop 40 by means of a projection 38 formed on the said carrier. The stop 40 is moulded as an integral part directly on the mounting plate 3 to project therefrom.In this arrangement, the stop 40 is seated on the mounting plate 3 in such a way that it mar be rotated, but otherwise it is connected in a manner resistant to vibration and therrnal expansion. The force required to rotate the stop 40 on the mounting plate 3, that is, the torque required for adjusting the stop 40 through overcoming the retaining force, can be determined by the dimensions h, d1 and d2 of the stop 40, or rather of the flange (not specifically denoted) integrally moulded on the stop 40. The retaining force can be increased by emploving a suitably formed ribbing on the mounting plate 3.

To adjust the stop 40, there is provided either a slot 41 suitable for the insertion of a screwdriver, or a hexagonal protrusion or recess, which is more advantageous for the transmission of greater actuating forces. It is also possible to construct the stop 40 with an adjusting knob, for example provided with knurling, so that it can be adjusted without tools. Figure 1 further illustrates, with the aid of dot-dash lines, how the zero position of the arm 20 corresponding to a measured value of zero, may be adjusted with the stop 40, of the recording system 1 over a plurality of measuring ranges. 42 denotes a spring fastened to the carrier 19 which serves to compensate the gear backlash in the recording system 1.

Figure 6 shows an exemplary embodiment of a stop 43. on which there is interallx moulded an arm 44 which embraces the mounting plate 3. The ann 44 thus serves for additionally securing the stop 43 on the mounting plate 3 and, since it is constructed as a toggle, serves as an adjusting element at the same time.

For better understanding of this exemplary embodiment, it should also be mentioned that the mounting plate 3 is relieved concentricity with the axis of the stop 43 in such a was that rotational movement of the arm 44 within a certain angular range is possible. The throw of the eccentric part 44 of the stop 43 must correspond to the sum of the maximum possible production and assembly tolerances of the components of the recording system 1, unless a plurality of measuring ranges are to be covered as in the exemplary embodiment according to Figure 1.

In the alternative embodiment according to Figures 3, 4 and 5, a carrier 46 is provided on which two projections 47 and 48 are formed. With these projections there are associated stops 49 and 50 which are rotatable and integrally moulded on the mounting plate 3. The stops 49 and 50 are uniform discs and each is provided with an actuating slot 51 and 52, respectivel!r. and with a shaped peripheral region 53 and 54, respectively, which forms a curved eccentric path leading from the outer uniform circumferential profile towards the centre of the respective stops.Each peripheral stop surface thus serves for adjusting different zero positions of the carrier 46, and therefore the speed-recording stylus by abutting the projections 47 or 48 respectivel. This solution is expedient particularly when measuring ranges which have a relatively large difference in the recording stroke are employed.

With this solution, it is necessary for the stop associated with the measuring range having the smaller recording stroke to be removed if the recording system is to execute a larder stroke. Consequently, the stop 49 is constructed such that it can be broken off, that is to say it is joined to a ring 56, integrally moulded on the mounting plate 3, merely via a web 55, to be precise in such a way that the web 55 is orientated substantially in the direction of movement of the carrier 46, so as to be able optimally to absorb the stop forces.

For the sake of completeness, it should also be mentioned that 57 denotes a bearing journal of the carrier 46, and 58 and 59 denote the bearing journals of the carrier 19.

Claims (11)

Claims

1. A tachograph for recording at least one measured parameter and having its recording system arranged on a mounting plate (3) and further comprising: a drivable carrier (19, 46) serving to move a recording stylus (23); and at least one stop means (40, 43, 49, 50) co-operable with the carrier so that when the value of the measured parameter is zero the carrier (19, 46) engages a peripheral surface of the stop means (40, 43, 49, 50), wherein the stop means is rotatably mounted on the mounting plate (3) and the peripheral surface thereof is eccentric relative to its axis of rotation.

2. A tachograph according to claim 1 wherein the stop means (40, 43, 49, 50) is moulded as an integral part directly into or onto the mounting plate (3) to project therefrom in such a manner that it is rotatable and self locking.

3. A tachograph according to claim 1 or 2 wherein the stop means (40) is a regular body mounted to rotate eccentrically.

4. A tachograph according to claim 1 or 2 wherein the stop means (49, 50) is a bodx mounted to rotate about its centre and having at least one region (53, 54) of its peripheral surface of different radius relative to the remainder of the peripheral surface.

5. A tachograph according to any one of claims 1. 2 3 or 4 characterised in that a pluralin; of stop means (40, 43 49, 50) are mounted on the plate (3) in spaced relation to one another and constructed in such a wa' that, the! can be selectively removed in order to define a plurality of zero positions of the recording stylus (23).

6. A tachograph according to any one of claims l to 5 wherein the measured parameter is vehicle speed.

7. A tachograph according to any one of claims 1 to 6 and further comprising a stepping motor (26) to drive the carrier (19,46) via gears (29, 30).

8. A tachograph according to any one of claims 1 to 7 and further comprising an arm (90) connecting the stylus (23) to the carrier ( 19, 46).

9. A tachograph according to claim 8 and further comprising means (15) to lift the recording stylus (23) away from a tachograph disc by engaging with a finger portion (21) of the arm (20).

10. A tachograph according to any one of the proceeding claims and further comprising means (22) for biasing the recording stylus against a tachograph disc.

11. A tachograph substantially as illustrated in and with reference to an! one of the figures of the accompany drawings.