FR2778375A1 - Automotive clutch pedal with return spring - Google Patents

Abstract

An automotive clutch pedal (2) with a lever pivots against a fixed point (6). An attachment links a point on the pedal with the clutch mechanism. The clutch pedal moves against the force of a return spring (11), which increases progressively during pedal travel to a dead point, and then reverses. The return spring consists of two concentric coil springs.

Description

The invention relates to a di.noqitif dP maneuvering a embravage

  intended in particular for motor vehicles and comprising an operating lever which is pivotally mounted in a center of rotation provided in a fixed position and which can reach two extreme positions, one of which corresponds to a clutch state and the other to the clutch release state. device also comprising means for exerting a force on the lever, the direction of the force reversing at a point

  of unstable equilibrium located between the two extreme points.

  Such devices are described in particular in DE-OS 29 23 027 and include a spring said to pass through an unstable equilibrium point, which is used

  to reduce the forces to be exerted on the pedal.

  To this end, this spring is used in a prestressed state between an operating lever generally used in the form of a clutch pedal and a

  component forming part of the vehicle body.

  When the declutching pedal is operated, the spring is compressed even more strongly until it reaches the unstable equilibrium point at which its two points of articulation and the center of rotation of the operating lever are located on a line. , so that the

  spring exerts no pivoting force on the lever.

  then it relaxes, so that a force opposing that of the Belleville spring of the clutch acts and therefore that the force to be exerted on the pedal decreases during the clutch process. The relaxation of the Belleville spring during the clutch process again compresses the spring passing through an unstable equilibrium point and returns the clutch pedal to the initial position. The alignment of the springs passing through an unstable equilibrium point with the other elastic elements, in particular with the Belleville spring of the clutch, has been the subject of multiple variants (by

  example DE-OS 34 17 814, FR 76 27871, JP 61-163569).

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  The drawback of the proposed solutions lies in the fall in the variation of the forces exerted on the pedal after exceeding the unstable equilibrium point, a fall which results from the combination of the elastic elements present in the momentary path of the forces and their levers. articulation, so that there appears the impression during the declutching process of a "hole" in the generation of the force produced on the pedal and which is felt to be troublesome by most drivers. Compensating for this characteristic by varying the lever lengths of the spring passing through an unstable equilibrium point (DE-OS 29 23 027) represents a solution which, however, is of a complicated embodiment.

  and whose price is not negligible.

  The invention therefore aims to provide a device which makes it possible to assimilate the force exerted on the operating lever. after passing through the unstable equilibrium point and up to the extreme point of the declutching stroke, maximum force and it is a question of trying to obtain a cheap solution. simple in design and can easily be fitted out

done a posteriori.

  The invention therefore relates to a device for operating a clutch intended in particular for motor vehicles. comprising an operating lever which is rotatably mounted around a center of rotation situated in a fixed position and which can reach two extreme positions, one of which corresponds to the tightening and the other to the release of the clutch, further comprising means exercise on the lever of a force whose direction is reversed at an unstable equilibrium point located between the two extreme points: according to an essential feature of the invention, said means present in the state of loosening of the 'clutch a non-linear variation of force which assists the clutch process along the stroke from the unstable equilibrium point to the extreme position.

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  Thus, the action of the means for assisting the declutching process can be adjusted so that immediately after passing through the unstable equilibrium point, a large force which acts in the direction of travel of the pedal and which - by being adapted to the constant of the other springs of the clutch - decreases with the increase in this stroke of the pedal towards the extreme point of disengagement therefore allows by simple means compensation for the fall in the variation of the force after passage by the unstable equilibrium point of the devices

of the prior art.

  Force accumulators, for example elastic elements, elastomers or the like, are advantageously provided for this use. When elastic elements are used, coil springs are particularly advantageous and these can be compression and traction elements and

can be combined.

  It may moreover be advantageous to use a combination of several of these elements for the generation of an overall characteristic curve of elasticity yes is not linear for the function of passing through an unstable equilibrium point. The variation of lever lengths on the prescribed circular path around the point of articulation of the spring, which is produced by means

  expensive correspondents, becomes useless.

  I1 can also be advantageous, in order to make savings with regard to the multiplicity of parts and the mounting, to produce the spring passing through an unstable equilibrium point in one piece and to represent in it the non-linear characteristic curve under made of

two or more storeys.

  Possible embodiments can consist of springs having progressive elasticity and / or two or more individual zones with which a corresponding number of individual elasticity constants can be associated. In addition, at least one floor of the

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  spring can be made so as to be sufficiently soft so that its turns are in abutment against each other under prestressing and therefore that it is short-circuited and is not put back into service until the end of a stroke of the pedal of corresponding length. so that in this case a weak assistance brought to the force exerted on the pedal is active towards the end of the stroke of the latter. The length of the spring can moreover be dimensioned so that the latter remains over the entire stroke of the pedal at least under a slight prestress so that the rattling noises can

be avoided.

  The dimensions of the spring passing through an unstable equilibrium point are preferably brought into line with those of the corresponding initial spring of a device according to the prior art in order to allow simple retrofitting of equipment and to produce without difficulty a device according to the invention capable of taking the place of a device according to the prior art. Even an optimization consisting in simply putting at the same level the forces exerted on the pedal after passing through the unstable equilibrium point and the maximum of the force exerted by the pedal of known devices is possible simply by using a spring passing through. an unstable equilibrium point which is adapted to the whole evolution of the forces exerted on the pedal. The device can advantageously be used in manual clutches, actuated for example by a Bowden transmission, as well as in hydraulically controlled clutches in which the clutch pedal can actuate a piston of a master cylinder which generates a control pressure of the declutching device which

  causes the clutch processes.

  Furthermore, in certain exemplary embodiments in which an actuation system for

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  the clutch is provided for the traction speed and the engine brake speed, the operating lever can be produced so that it can be actuated almost without force thanks to the spring passing through an unstable equilibrium point, the means of representation of this spring by its nonlinear behavior which can balance, possibly ensuring in addition the described compensation functions, existing non-linear auxiliary characteristic curves of leverage and power

actuation system.

  Otherwise. the device can compensate for characteristic curves of Belleville springs and their leverage, forming part of self-adjusting clutches, which compensate for wear of the friction linings and which are generally characterized by a fairly rapid fall in the force produced on the pedal as a function of the stroke of the latter after passing through the unstable equilibrium point, as well as other combinations of spring and lever having

  nonlinear characteristic curves.

  The invention will be described in more detail by way of nonlimiting example with regard to the accompanying drawings in which: FIG. 1 is a sketch of representation of the operating principle of a spring passing through an unstable equilibrium point at three selected pedal positions, FIG. 2 is a characteristic curve of an exemplary embodiment according to the invention of a spring passing through an unstable equilibrium point with respect to the prior art, FIG. 3 is a graph of the force as a function of the pedal stroke of an exemplary embodiment according to the invention of a mounted spring, passing through an unstable equilibrium point, compared with the prior art,

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  FIG. 4 is a graph of the force as a function of the stroke of the pedal of an exemplary embodiment according to the invention of a device for operating the clutch with respect to the prior art, and FIG. 5 illustrates a exemplary embodiment of a device according to the invention intended for maneuvering

of a clutch.

  FIG. 1 represents the operating mode of a device for operating a clutch 1. having the form of a clutch pedal 2, with three selected positions I, II, III thereof, as well as a spring 3 passing through an unstable equilibrium point, the spring 3 being highlighted on an enlarged scale and the part for transmitting the force of the pedal to the clutch being eliminated for the sake of simplicity. The spring 3 is mounted at one end along the direction of its action while being connected in a fixed position. but in an orientable manner, to the body (not shown) of the vehicle by means of an articulation point 4. The other end of the spring 3 is rotatably mounted at another articulation point 7 on a support 5 secured to the pedal 2 When it is actuated, the pedal 2 pivots about an axis 6 which supports it in a fixed position on the

  bodywork by means of an axis simply indicated.

  ! 5 In position I, the clutch is tight and pedal 2 is in the initial state. Due to the preload of the spring 3 passing through an unstable equilibrium point,

  a force acts on the support 5 and therefore on the pedal 2 au-

  below the center of rotation 6, that is to say in the opposite direction to that of the force F of the foot which moves the clutch pedal 2 and therefore the latter is pushed towards a stop not shown, The driver pushes the pedal 2 , against this force present, with the force F of its foot towards the spring 3 by further banding the latter. Position II

  represents a state at which the two points of articulation 4.

  7 and the center of rotation 6 are on a line, from

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  so that the spring 3 exerts on the pedal 2 no force causing a rotational movement and therefore it

  found at the point of unstable equilibrium.

  During the continuation of the thrust exerted on the pedal 2, the relaxation of the spring 3 produces a force which assists that which is exerted on the pedal. because the force of the spring attacks the lever arm of the Maze 2 which is located in the center of rotation 6 on the opposite side from that of the lever arm on which the

o10 force F of the oied.

  The spring 3 continues its relaxation with the increase in the travel of the labyrinth and the conformation according to the invention of this spring becomes perceptible by the

  decrease in the force F exerted on the Daedalus.

  In the illustrated embodiment, the spring 3. whose action is not linear. is on two individual floors 3a. 3b auxauels the constants

  of elasticity Ci. C2 can be affected. with C1> C2.

  So. the second floor 3b. which is the softest, undergoes a compression such that its turns are in abutment against each other and therefore it is short-circuited until the first stage 3a of the spring is relaxed and. during the continuation of the pedal stroke, the second stage 3b of the spring relaxes. At position III, pedal 2 is fully pushed, but the second stage 3b of the spring is held slightly under pretension so that it retains

  its positioning in its housing.

  To show the elasticity curve of the example shown in FIG. 1, the graph in FIG. 2 illustrates the variation F of the force as a function of the stroke s of the spring 3 (solid line) with respect to a spring. used in the prior art and having a linear characteristic curve (broken line). This graph shows the non-linear characteristic curve of the spring in the form of two individual stages 3a, 3b having the elastic constants C1, C2, with Ci> C2. Other nonlinear characteristic curves can be by

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  hyperbolic example using a winding

  progressive spring or several individual stages.

  FIG. 3 illustrates the repercussion on the force Fppei exerted on the pedal as a function of the stroke SB of c.tt. cimrnirp T. [mndifict: inn çri rnnnOrtc dj p1vi r while the stroke of the pedal is carried out while the prestressed spring performs a circular path around its point of articulation on the body transforms the force F of spring 3 (figure 1) in the force Fppei produced on the pedal. The broken line curve indicates la1 fnorce Fppi that Ln rpanrt linear p g nr an unstable equilibrium point according to the prior art exerts on the pedal. This spring first of all also undergoes further compression in part I of the travel of the pedal and. after passing through the unstable equilibrium point - characterized by the position II of the pedal - it makes a contribution to the force Fppei exerted on the pedal, which increases continuously, by its relaxation in the range III of the pedal stroke but whose contribution is becoming increasingly weak. The spring according to

  the invention passing through an unstable equilibrium point -

  which is represented by the solid line - reacts until the unstable equilibrium point is exceeded

  close in the same way as the prior art spring.

  however. for short strokes of the SB pedal and after passing through an unstable equilibrium point, it first makes an increasing contribution to reach a maximum and when continuing the lengthening of the SB strokes of the pedal, it brings decreasing force contributions, the greatest contributions being associated with the elements of the spring having the steepest characteristic curve and the relaxation of the stiff spring element occurs for pedal strokes SB aui are notably lower than those producing maximum force, so during arands SB pedal strokes. there is no longer a soft floor 3b

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  of the spring (Figure 1), which provides the weakest

contribution to the force, which acts.

  The advantage of using non-linear springs passing through an unstable equilibrium point is clearly shown in the graph in FIG. 4 in which the overall force FG of the clutch pedal is brought as a function of the strokes SB of this last. Curve 1 shows the overall force FG exerted on the pedal as a function of the stroke SB of the latter without the use of a spring passing through an unstable equilibrium point. The pedal forces are greatly increased and after a maximum force has been overcome, they fall back. Curve 2 illustrates the prior art by varying the overall force of the FG pedal with an initial force F0 acting by the preload of the spring passing through an unstable equilibrium point and a maximum after passing this point at the position II of the pedal. which gives the driver the impression of a "hole" in the evolution of the clutch actuation force. If the fall in the overall force FG of the pedal after exceeding the maximum was even greater than that shown in the graph. there would be the

  risk that the clutch pedal remains blocked.

  The use of a spring according to the invention produces a change in the overall force as a function of the stroke SB of the pedal - which is shown on curve 3 - which results in a significantly less fall in the overall force FG after that maximum strength has been reached. because the nonlinear spring only provides much lower force contributions from its soft stage and therefore. in this part of the pedal travel, the overall force Fg does not fall as sharply as that caused by the use by a linear action spring. The difference between the prior art and the spring according to the invention when passing through an equilibrium point

  unstable is characterized by AFG strength gain.

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  FIG. 5 illustrates an exemplary embodiment according to the invention of a device 1 for operating a clutch, not shown. comprising a pedal 2 equipped with a plate 3 and articulated so as to be able to pivot about an axis 6 on the body, not shown, of the vehicle. In the illustrated embodiment, a support 8 which is provided on the declutching pedal 2 radially outside the articulation axis 6 has the shape of a blocked stud on which the push rod 9 is articulated a master cylinder 10 comprising a connection b for transmitting its pressure to a

  declutching a hydraulically operated clutch, the master-

  cylinder 10 being connected by screws 10a to a body (not shown) of the vehicle. To provide assistance to the force F of the foot when the clutch is released, a spring 3 passing through an unstable equilibrium point, which is mounted by means of a stud locked on the articulation point 7 radially between the plate 2a of the pedal and the pivot axis 6 of the latter, bears against the vehicle body on a hinge point 4 provided radially between the hinge point 7 and the pivot axis 6. This spring 3, which is in two individual stages 3a, 3b and has a characteristic curve of elasticity which is not linear, penetrates by a pointed support 11 into a concave bearing shell 12 produced in the support 13 fixed to the vehicle body , so as to allow a balance of forces by shifting the bodywork relative to the clutch pedal 2 or to the turns of the spring. A telescopic combination of a guide sleeve 14 connected to the support 11 of the spring and a guide rod 15 passing through this sleeve and connected in turn to the housing 16 of the pedal side spring assumes the guiding of the spring 3 along of his direction of action. The housing 16 of the spring is extended by a connecting rod 17 which bears on

the support stud 7.

  At the initial position of the declutching pedal 2 and when the clutch is tightened, the stage 3b of the spring is turned against turn - that is to say that it is short-circuited - and the stage 3a of this spring is prestressed. so that pedal 2 is held at its

  position. When pedal 2 is pressed, spring 3 -

  more precisely its stage 3a - is more compressed, because it results from the pivoting movement of the pedal 2 that the stroke of the spring is shortened and it is necessary to exert an additional force F at the foot and more particularly up to the point of the stroke of the pedal to which the pivot axis 6 and the articulation points 4. 7 of the spring 3 are located on a liana. The device is at the unstable equilibrium point of the spring 3. When the pedal stroke continues to increase, the spring 3 again elongates and assists the force F of the foot of the

  as described with reference to Figures 3 and 4.

  At the extreme position of the pedal 2 ′ to which the clutch is released, the stage 3a of the spring is completely relaxed and its stage 3b is sufficiently so that it stands by itself in the mounting position thanks to the still active force of the spring. so that additional restraint and possible rattling of the

  spring 3 in the free state are avoided.

  It should be understood that it is possible to make various modifications to the embodiments

  described and represented without departing from the scope of the invention.

Claims (12)

RESELL CATIONS   1. A device for operating a clutch intended in particular for motor vehicles and comprising an operating lever which is rotatably mounted around a center of rotation provided in a fixed position and which can reach two extreme positions, one of which corresponds to one clutch state and the other, in the clutch release state, a device further comprising means for exerting on the lever a force whose direction is reversed at an unstable equilibrium point located between the two extreme points, characterized in that said means (3) have in the release state of the clutch, along the race going from the unstable point of equilibrium to the extreme position. a nonlinear variation of force which supports the clutch process.   2. Device according to claim 1, characterized in that said means consist of at least a coil spring.   3. Device according to one or other of the   claims 1 and 2, characterized in that said means   are made in the form of at least one helical spring which has a progressive characteristic curve. 4. Device according to one or other of the   claims 1 and 2, characterized in that the spring   coil or coil springs which is (are)   used (s) are a spring or compression springs.   5. Device according to one or other of the   claims 1 and 2, characterized in that the spring   coil or coil springs which is (are) used consist of a tension spring or tension springs.   6. Device according to any one of   previous claims, characterized in that said   3 means are a combination of at least two elements of a helical spring. 13 2778375   7. Device according to any one of   previous claims, characterized in that said   means consist of a combination of at least two stages of spring having characteristic curves of elasticity which differ. 8. Device according to claim 7, characterized in that a spring stage is short-circuited over at least part of the stroke of the operating lever. 9. Device according to any one of   previous claims, characterized in that the   helical spring is prestressed over the entire stroke between the two extreme points (4, 7). 10. Device according to any one of   previous claims, characterized in that   used for a manually operated clutch.   11. Device according to any one of   Claims 1 to 9, characterized in that it is used   for a hydraulically operated clutch.   12. Device according to any one of   previous claims, characterized in that   used for a wear compensation clutch.