TORQUE-LIMITING DEVICE FOR VEHICLE

Providing a vehicle torque limiter device enabling acquisition of a hysteresis torque with a simple structure. Since a friction force F1 generated on friction surfaces between a pressure plate 80 and a first friction material 88 is smaller than a friction force F2 generated on friction surfaces between a lining plate 76 and the first friction material 88, when a torque T is input to a damper device 38, a slip first occurs between the pressure plate 80 and the first friction material 88, and the lining plate 76 and the first friction material 88 integrally rotate. In this case, a hysteresis torque T1 is generated based on the friction force between the pressure plate 80 and the first friction material 80. Since a torque limiter mechanism 68 also acts as a hysteresis mechanism in this way, the torque limiter mechanism 68 is realized that can generate the hysteresis torque with a simple structure.

MODE FOR CARRYING OUT THE INVENTION

An example of the present invention will now be described in detail with reference to the drawings. In the following example, the figures are simplified or deformed as needed and portions are not necessarily precisely depicted in terms of dimension ratio, shape, etc.

First Example

FIG. 1is a general configuration diagram for explaining a hybrid type vehicle drive device10to which the present invention is applied. InFIG. 1, the vehicle drive device10transmits a torque of a first drive source12, i.e., a main drive source, to a wheel-side output shaft14acting as an output member in a vehicle such that the torque is transmitted from the wheel-side output shaft14via a differential gear device16to a pair of left and right drive wheels18. The vehicle drive device10is disposed with a second electric motor MG2capable of selectively providing power running control for outputting drive power for running and regenerative control for recovering energy as a second drive source and the second electric motor MG2is coupled via an automatic transmission22to the wheel-side output shaft. Therefore, an output torque transmitted from the second electric motor MG2to the wheel-side output shaft is increased and decreased depending on a gear ratio γs (=rotation speed Nmg2 of the second electric motor MG2/rotation speed Nout of the wheel-side output shaft) set by the automatic transmission22.

The automatic transmission22interposed in a power transmission path between the second electric motor MG2and the drive wheels18is configured such that a plurality of stages having the gear ratio γs greater than “1” can be established; at the time of power running when a torque is output from the second electric motor MG2, the torque can be increased and transmitted to the wheel-side output shaft; and, therefore, the second electric motor MG2is configured with a lower capacity or in a smaller size. As a result, for example, if the rotation speed Nout of the wheel-side output shaft is increased in association with a higher vehicle speed, the gear ratio γs is made smaller to reduce the rotation speed (hereinafter referred to as a second electric motor rotation speed) Nmg2 of the second electric motor MG2so as to maintain the operation efficiency of the second electric motor MG2in a favorable state, or if the rotation speed Nout of the wheel-side output shaft is reduced, the gear ratio γs is made larger to increase the second electric motor rotation speed Nmg2.

The first drive source12is mainly made up of an engine24acting as a main power source, a first electric motor MG1, and a planetary gear device26acting as a power distribution mechanism for combining or distributing torque between the engine24and the first electric motor MG1. The engine24is a known internal combustion engine combusting fuel to output power, such as a gasoline engine and a diesel engine, and is configured to have an operational state, such as a throttle valve opening degree and an intake air amount, a fuel supply amount, and an ignition timing, electrically controlled by an engine-control electronic control device (E-ECU) not depicted mainly made up of a microcomputer. The electronic control device is supplied with detection signals from an accelerator operation amount sensor AS detecting an operation amount of an accelerator pedal, a brake sensor BS for detecting the presence of operation of a brake pedal, etc.

The first electric motor MG1is, for example, a synchronous electric motor, configured to selectively fulfill a function as an electric motor generating a drive torque and a function as an electric generator, and is connected via an inverter30to an electric storage device32such as a battery and a capacitor. The inverter30is controlled by a motor-generator-control electronic control device (MG-ECU) not depicted mainly made up of a microcomputer, thereby adjusting or setting the output torque or a regenerative torque of the first electric motor MG1.

The planetary gear device26is a single pinion type planetary gear mechanism including a sun gear S0, a ring gear R0disposed concentrically to the sun gear S0, and a carrier CA0supporting a pinion gear P0meshing with the sun gear S0and the ring gear R0in a rotatable and revolvable manner as three rotating elements to generate a known differential action. The planetary gear device26is disposed concentrically to the engine24and the automatic transmission22. Since the planetary gear device26and the automatic transmission22are symmetrically configured relative to a center line, the lower halves thereof are not depicted inFIG. 1.

In this example, a crankshaft36of the engine24is coupled via a damper device38and a power transmission shaft39to the carrier CA0of the planetary gear device26. On the other hand, the sun gear S0is coupled to the first electric motor MG1, and the ring gear R0is coupled to the wheel-side output shaft. The carrier CA0, the sun gear S0, and the ring gear R0act as an input element, a reaction force element, and an output element, respectively.

If a reaction torque from the first electric motor MG1is input to the sun gear S0for an output torque of the engine24input to the carrier CA0in the planetary gear device26, a direct torque occurs in the ring gear R0that is the output element and, therefore, the first electric motor MG1acts as an electric generator. When the rotation speed of the ring gear R0, i.e., the rotation speed (output shaft rotation speed) Nout of the wheel-side output shaft14is constant, a rotation speed (engine rotation speed) Ne of the engine24can continuously be changed by changing a rotation speed Nmg1 of the first electric motor MG1higher and lower.

The automatic transmission22of this example is made up of a set of Ravigneaux type planetary gear mechanisms. In other words, the automatic transmission22is disposed with a first sun gear S1and a second sun gear S2; a larger diameter portion of a stepped pinion P1meshes with the first sun gear S1; a smaller diameter portion of the stepped pinion P1meshes with a pinion P2; and the pinion P2meshes with a ring gear R1(R2) disposed concentrically to the sun gears S1and S2. The pinions P1and P2are held by a common carrier CA1(CA2) in a rotatable and revolvable manner. The second sun gear S2meshes with the pinion P2.

The second electric motor MG2is controlled via an inverter40by the motor-generator-control electronic control device (MG-ECU) to act as an electric motor or an electric generator and an assist output torque or a regenerative torque is adjusted or set. The second sun gear S2is coupled to the second electric motor MG2and the carrier CA1is coupled to the wheel-side output shaft. The first sun gear S1and the ring gear R1make up a mechanism corresponding to a double pinion type planetary gear device along with the pinions P1and P2, and the second sun gear S2and the ring gear R1make up a mechanism corresponding to a single pinion type planetary gear device along with the pinion P2.

The automatic transmission22is disposed with a first brake B1disposed between the first sun gear S1and a housing42that is a non-rotating member for selectively fixing the first sun gear S1, and a second brake B2disposed between the ring gear R1and the housing42for selectively fixing the ring gear R1. The brakes B1, B2are so-called friction engagement devices using a frictional force to generate a braking force and are implemented by employing multi-plate type engagement devices or band-type engagement devices. The brakes B1, B2are configured such that torque capacities thereof are respectively continuously changed depending on engagement pressures generated by a hydraulic actuator for the brake B1and a hydraulic actuator for the brake B2such as hydraulic cylinders.

The automatic transmission22configured as described above is configured such that the second sun gear S2acts as an input element, that the carrier CA1acts as an output element, that a high-speed stage H is established with a gear ratio γsh greater than “1” when the first brake B1is engaged, and that a low-speed stage L is established with a gear ratio γs1 greater than the gear ratio γsh of the high-speed stage H when the second brake B2is engaged instead of the first brake B1. In other words, the automatic transmission22is a two-speed transmission in which a shift between the gear stages H and L is performed based on a running state such as a vehicle speed V and a required drive power (or an accelerator operation amount). More specifically, shift stage ranges are determined in advance as a map (shift diagram) and control is provided such that one of the shift stages is set depending on a detected operational state.

FIG. 2is a cross-sectional view for explaining a configuration of the damper device38depicted inFIG. 1in detail. The lower half of the damper device38from an axial center C is not depicted inFIG. 2. The damper device38is disposed around the axial center C between the engine24and the planetary gear device26in a power transmittable manner. The power transmission shaft39depicted inFIG. 1is spline-fitted to an inner circumferential portion of the damper device38.

The damper device38includes a pair of left and right disc plates56rotatable around the axial center C, a hub member58relatively non-rotatably coupled to the power transmission shaft39by spline fitting and disposed relatively rotatably to the disc plates56around the same axial center, coil springs62(torsion springs) made of spring steel interposed between the disc plates56and the hub member58to operatively (elastically) couple the disc plates56and the hub member58while elastically deforming depending on a relative rotation amount between the members, a hysteresis mechanism64generating a friction force between the disc plates56and the hub member58, and the torque limiter mechanism68disposed on the outer circumferential side of the disc plates56. The torque limiter mechanism68corresponds to a vehicle torque limiter device of the present invention.

The disc plates56are made up of a pair of disc-shaped first and second plates70and72on the right and left and are relatively non-rotatably fixed by a rivet66with the coil springs62axially sandwiched by the plates70and72. The rivet66also acts as a fastening member of a lining plate76of the torque limiter mechanism68described later. The first plate70has a plurality of first opening holes70aformed in a circumferential direction for housing the coil springs62. The second plate72has a plurality of second opening holes72aformed in the circumferential direction at positions corresponding to the first opening holes70afor housing the coil springs62. A plurality of the coil springs62is housed in spaces formed by the first opening holes70aand the second opening holes72a. As a result, when the disc plates56rotate around the axial center C, the coil springs62are revolved around the axial center C in the same way.

The hub member58is formed from a cylindrical portion58aincluding inner circumferential teeth spline-fitted to the power transmission shaft39in an inner circumferential portion and circular-plate-shaped flange portions58bradially extending outward from an outer circumferential surface of the cylindrical portion58a. The coil springs62are housed in spaces formed between the flange portions58bin the rotation direction. As a result, when the hub member58rotates around the axial center C, one ends of the coil springs62abut on the hub member58and, therefore, the coil springs62are revolved around the axial center C in the same way. With such a configuration, the coil springs62operatively couple the disc plates56and the hub member58while elastically deforming depending on a relative rotation amount between the members. For example, when the disc plates56rotate, one ends of the coil springs62are pressed and the other ends of the coil springs62press the flange portions58bof the hub member58, thereby rotating the hub member58. In this case, since the coil springs62transmit the rotation while being elastically deformed, a shock due to torque variation is absorbed by the elastic deformation of the coil springs62.

The hysteresis mechanism64is disposed on the inner circumferential side of the coil springs62and between the disc plates56and the flange portions58bof the hub member58in an axial direction. The hysteresis mechanism64is made up of a plurality of friction materials, a disc spring, etc., and generates a friction force between the disc plates56and the hub member58. Optimum hysteresis torque is set by adjusting this friction force. The hysteresis mechanism64of this example includes a friction engagement element made of a friction material with a low friction coefficient and a friction engagement element made of a friction material with a high friction coefficient to generate two-stage hysteresis torques.

The torque limiter mechanism68(the torque limiter device of the present invention) is disposed on the outer circumferential side of the disc plates56and has a function of preventing torque transmission exceeding a preset limit torque Tlim. The torque limiter mechanism68includes the annular-plate-shaped lining plate76fastened by the rivet66along with the disc plates56to integrally rotate around the axial center C with the disc plates56, a support plate78consisting of a disc-shaped first support plate78aand a circular-plate-shaped second support plate78blocated on the outer circumferential side, a circular-plate-shaped pressure plate80disposed adjacently to the lining plate76to be housed in the support plate78, a cone-shaped disc spring82interposed in a preloaded state in a gap between the pressure plate80and the first support plate78ain the axial direction, a first friction material88(friction material) interposed between the pressure plate80and the lining plate76, and a second friction material89interposed between an inner circumferential portion of the second support plate78band the lining plate76. The pressure plate80corresponds to a cover plate of the present invention.

FIG. 3is a partially enlarged cross-sectional view of the torque limiter mechanism68ofFIG. 2. Description will hereinafter be made with reference toFIG. 3. The support plate78is made up of a pair of the disc-shaped first support plate78aand the circular-plate-shaped second support plate78bon the left and right having outer circumferential portions disposed with bolt holes84and86, respectively, for bolt-fastening not depicted fixing a flywheel50ofFIG. 1and the support plates78aand78b.

The first support plate78ahas an inner circumferential portion bent in the axial direction to form a space between the first support plate78aand the second support plate78b. This space houses the disc spring82, the pressure plate80, the first friction material88, the lining plate76, and the second friction material89in this order from the first support plate78atoward the second support plate78bin the axial direction.

The lining plate76is an annular-plate-shaped member fixed by the rivet66along with the first plate70and the second plate72. The pressure plate80is also formed into an annular plate shape. The pressure plate80and the lining plate76are configured to be relatively rotatable around the same axial center C. The first friction material88is interposed between the pressure plate80and the lining plate76. The first friction material88is formed into an annular plate shape, for example. Alternatively, the first friction materials88may be formed into an arc shape and arranged at regular angular intervals side-by-side in the circumferential direction.

In the first friction material88, a friction surface on the side adjacent to the pressure plate80is configured to be slidable on the pressure plate80. A friction surface of the first friction material88adjacent to the lining plate76is configured to be slidable on the lining plate76. Therefore, the first friction material88is fixed by neither the adjacent pressure plate80nor the lining plate76.

A friction coefficient μ1 of the friction surfaces (sliding surfaces) between the pressure plate80and the first friction material88is made smaller than a friction coefficient μ2 of the friction surfaces (sliding surfaces) between the lining plate76and the first friction material88. Therefore, a friction force F1 generated on the friction surfaces between the pressure plate80and the first friction material88is smaller than a friction force F2 generated on the friction surfaces between the lining plate76and the first friction material88.

A stopper90is disposed between the pressure plate80and the first friction material88to define an upper limit value of a slip amount (relative rotation amount) between the pressure plate80and the first friction material88. The stopper90is made up of a column-shaped projection92axially projecting from the friction surface of the pressure plate80adjacent to the first friction material88, and a circular stopper hole94formed in the first friction material88. The projection92is housed in the stopper hole94and has a backlash (gap) in the circumferential direction (rotation direction) for defining a predetermined slip amount (relative rotation) between the pressure plate80and the first friction material88.

FIG. 4is an arrow view of the pressure plate80and the first friction material88viewed from arrow A inFIG. 3. As depicted inFIG. 3, the stopper hole94is formed into a perfectly circular hole larger than the diameter of the projection92. As a result, the backlash is formed between the projection92and the stopper hole94and a slip in the rotation direction is allowed between the pressure plate80and the first friction material88by the backlash. Therefore, when a slip amount between the pressure plate80and the first friction material88reaches a defined value, the projection92abuts on the wall surface of the stopper hole94, making the pressure plate80and the first friction material88relatively non-rotatable.

The second friction material89is interposed between the inner circumferential portion of the second support plate78band the lining plate76. The second friction material is formed into, for example, an annular plate shape, as is the case with the first friction material88. Alternatively, the second friction materials89may be formed into an arc shape and arranged at regular angular intervals side-by-side in the circumferential direction.

In the second friction material89, a friction surface on the side adjacent to the second support plate78bis configured to be slidable on the second support plate78band a friction surface adjacent to the lining plate76is configured to be slidable on the lining plate76. Therefore, the second friction material89is fixed by neither the adjacent second support plate78bnor the lining plate76. The friction coefficient μ is set to the friction coefficient μ2 on both the friction surfaces (sliding surfaces) between the second support plate78band the second friction material89and the friction surfaces (sliding surfaces) between the lining plate76and the second friction material89.

The disc spring82is interposed in the preloaded state between the first support plate78aand the pressure plate80. The disc spring82is formed into a cone shape with an inner circumferential end portion thereof abutting on the pressure plate80and an outer circumferential end portion abutting on the first support plate78aand is deformed and interposed to have a deflection amount generating the preload (disc spring load W). Therefore, the disc spring82axially presses the pressure plate80toward the lining plate76by the disc spring load W. As a result, a friction force F is generated between the pressure plate80and the first friction material88, between the lining plate76and the first friction material88, between the second support plate78band the second friction material89, and the lining plate76and the second friction material89. The disc spring82corresponds to a pressing member of the present invention.

An operation of the damper device38configured as described above will be described.FIG. 5depicts relationship between a torque T input to the damper device38and a torsional angle θ of the damper device38. The horizontal axis indicates the torsional angle θ and the vertical axis indicates the torque T. When the torque T is input to the damper device38and the torsional angle θ increases to a torsional angle θ1, a slip first occurs on the friction surfaces between the pressure plate80and the first friction material88having the lower friction coefficient μ1, and a hysteresis torque T1 is generated at this point. The hysteresis torque T1 in this case is represented by the following Equation (1). In Equation (1), r1 denotes an operation radius (rotation radius) of the first friction material80and W denotes the disc spring load of the disc spring82.

When the torsional angle θ reaches θ2, the slip amount allowed by the stopper90reaches the defined value. In this case, the projection92abuts on the stopper hole94in the stopper90, making the pressure plate80and the first friction material88relatively non-rotatable. Therefore, the slip is regulated between the pressure plate80and the first friction material88. A slip then occurs on the friction surfaces between the lining plate76and the first friction material88. A torque T2 generated in this case is represented by the following Equation (2). Since the friction coefficient μ2 is larger than the friction coefficient μ1, the torque T2 becomes larger than the torque T1 (T2>T1). The torque T2 is a limit torque Tlm of the torque limiter mechanism68.

As a result, the single stage hysteresis torque T1 is realized in the torque limiter mechanism68. The torque limiter mechanism68is disposed closer to the outer circumference than the disc plates56, the operation radius (rotation radius) r1 of the first friction material88is made larger. Therefore, since a wide range of hysteresis torque from small hysteresis torque to large hysteresis torque can be acquired by adjusting the friction coefficient μ1 and the disc spring load W of the disc spring82, a degree of freedom of design is significantly improved. Since the torque limiter mechanism68also acts as the hysteresis mechanism, i.e., the torque limiter mechanism68is also used as the hysteresis mechanism, the torque limiter mechanism68is realized that can generate the hysteresis torque with a simple structure.

Since conventional hysteresis mechanisms are disposed on the inner circumferential portion of the damper device, a large hysteresis torque is difficult to acquire. To acquire a large hysteresis torque in the conventional hysteresis mechanisms, it is required to use high friction coefficient material and increase a pushing load of the disc spring; however, since high friction coefficient material has poor abrasion resistance, if the pushing load of the disc spring is increased, peripheral components receive a larger reaction force and, therefore, the strength of these components must be raised. Thus, a large hysteresis torque is difficult to acquire.

On the other hand, since the torque limiter mechanism68is disposed with the hysteresis torque mechanism in this example, the operation radius (rotation radius) of the friction material increases and even a large hysteresis torque can easily be realized. For example, it is conventionally difficult to attenuate a resonance or engine start torque, which is input equal to or greater than the engine maximum torque, with hysteresis torque. In this regard, since a hysteresis torque exceeding the engine maximum torque can be generated in this example, the attenuation with hysteresis torque can be achieved at the time of resonance or engine start.

As described above, according to this example, since the friction force F1 generated on the friction surfaces between the pressure plate80and the first friction material88is smaller than a friction force F2 generated on the friction surfaces between the lining plate76and the first friction material88, when the torque T is input to the damper device38, a slip first occurs between the pressure plate80and the first friction material88, and the lining plate76and the first friction material88integrally rotate. In this case, the hysteresis torque T1 is generated based on the friction force between the pressure plate80and the first friction material80. In other words, the pressure plate80and the first friction material88making up the torque limiter mechanism68act as the hysteresis mechanism. When the slip amount between the pressure plate80and the first friction material88reaches the defined value, the stopper90is actuated and the slip between the pressure plate80and the first friction material88is inhibited. As a result, the torque limiter mechanism68acts as a normal torque limiter based on the friction force generated on the friction surfaces between the lining plate76and the first friction material88. Since the torque limiter mechanism68is also used as the hysteresis mechanism in this way, the torque limiter mechanism68is realized that can generate the hysteresis torque with a simple structure. Since the torque limiter mechanism68is disposed closer to the outer circumference than the disc plates56, the operation radius (rotation radius) of the torque limiter mechanism68is increased and even a large hysteresis torque can be realized. By using low friction material etc., a small hysteresis torque can also easily be acquired. This configuration can easily be achieved without adding the number of components.

According to this example, since this configuration can simply be achieved by differentiating the friction coefficients of the both surfaces of the friction material, forming the stopper hole94in the friction material, and forming the projection92on the pressure plate80in a conventional configuration, a wide range of hysteresis torque can be generated without making a significant design change.

Since the two-stage hysteresis mechanism64is included in this example, three-stage hysteresis torques can be realized by adding the hysteresis of the torque limiter mechanism64.

Other examples of the present invention will be described. In the following description, the portions common with the example are denoted by the same reference numerals and will not be described.

Second Example

FIG. 6is a cross-sectional view for explaining a structure of a torque limiter mechanism102included in a damper device100that is another example of the present invention, corresponding toFIG. 3in the example. A support plate104is made up of a pair of a disc-shaped first support plate104aand a circular-plate-shaped second support plate104bon the left and right. The first support plate104ahas an inner circumferential portion bent in the axial direction to form a space between the first support plate104aand the second support plate104b. This space houses a disc spring108, a pressure plate106, a first friction material110, the lining plate76, and a second friction material112from the first support plate104atoward the second support plate104b. The torque limiter mechanism102corresponds to the vehicle torque limiter device of the present invention; the first friction material110corresponds to a first friction material of the present invention; the second friction material112corresponds to a second friction material of the present invention; the pressure plate106corresponds to a first cover plate of the present invention; the second support plate104bcorresponds to a second cover plate of the present invention; and the disc spring108corresponds to the pressing member of the present invention.

The pressure plate106and the second support plate104bare rotatably disposed around the axial center C and the lining plate76is relatively rotatable to the pressure plate106and the second support plate104baround the axial center C.

The first friction material110is interposed between the pressure plate106and the lining plate76. In the first friction material110, a friction surface on the side adjacent to the pressure plate106is configured to be slidable on the pressure plate106and a friction surface adjacent to the lining plate76is configured to be slidable on the lining plate76. Therefore, the first friction material110is fixed by neither the pressure plate106nor the lining plate76.

A friction coefficient μ1 of the friction surfaces (sliding surfaces) between the pressure plate106and the first friction material110is made smaller than a friction coefficient μ2 of the friction surfaces (sliding surfaces) between the lining plate76and the first friction material110. Therefore, a friction force F1 generated between the pressure plate106and the first friction material110is smaller than a friction material F2 generated between the lining plate76and the first friction material110.

A first stopper116(first stopper) is disposed between the pressure plate106and the first friction material110to define a maximum amount of a slip amount (relative rotation amount) between the pressure plate106and the first friction material110. The first stopper116is made up of a column-shaped projection118axially projecting from the friction surface of the pressure plate106adjacent to the first friction material110, and a perfectly circular stopper hole120formed in the first friction material110. The projection118is housed in the stopper hole120to form a backlash L1(gap) in the circumferential direction (rotation direction) for defining the slip amount (relative rotation) between the pressure plate106and the first friction material110.

The second friction material112is formed between the inner circumferential portion of the second support plate104band the lining plate76. In the second friction material112, a friction surface on the side adjacent to the second support plate104bis configured to be slidable on the second support plate104band a friction surface adjacent to the lining plate76is configured to be slidable on the lining plate76. Therefore, the second friction material112is fixed by neither the second support plate104bnor the lining plate76.

The friction surfaces (sliding surfaces) between the second support plate104band the second friction material112are set to the friction coefficient μ1. In other words, the friction coefficient is made equal to the friction coefficient μ1 of the friction surfaces (sliding surfaces) between the pressure plate106and the first friction material110. A friction coefficient μ3 of the friction surfaces (sliding surfaces) between the lining plate76and the second friction material112is made larger than the friction coefficient μ2 of the friction surfaces (sliding surfaces) between the lining plate76and the first friction material110.

As a result, the smallest friction coefficient is the friction coefficient μ1 of the friction surfaces (sliding surfaces) between the pressure plate106and the first friction material110and the friction coefficient μ1 of the friction surfaces (sliding surfaces) between the second support plate104band the second friction material112, and the friction coefficient μ2 of the friction surfaces (sliding surfaces) between the lining plate76and the first friction material110is larger than the friction coefficient μ1 while the friction coefficient μ3 of the friction surfaces (sliding surfaces) between the lining plate76and the second friction material112is the largest (μ3>μ2>μ1). Therefore, the friction force F1 generated between the pressure plate106and the first friction material110and the friction force F1 generated between the second support plate104band the second friction material112are equal to each other and smaller than the friction force F2 generated between the lining plate76and the first friction material110. The friction force F2 generated between the lining plate76and the first friction material110is smaller than a friction force F3 generated between the lining plate76and the second friction material112(F3>F2>F1).

A second stopper122(second stopper) is disposed between the second support plate104band the second friction material112to define a slip amount (relative rotation amount) between the second support plate104band the second friction material112. The second stopper122is made up of a column-shaped projection124axially projecting from the friction surface of the second support plate104badjacent to the second friction material112, and a perfectly circular stopper hole126formed in the second friction material112. The projection124is housed in the stopper hole126to form a backlash L2(gap) in the circumferential direction for defining the slip amount (relative rotation) between the second support plate104band the second friction material112. The backlash L2of the second stopper122is configured to be larger than the backlash L1set in the first stopper116. For example, as depicted inFIG. 6, the projections118and124are formed into a columnar shape while the stopper holes120and126are formed into a circular shape, and the diameter of the projection124is formed smaller than that of the projection118while the stopper hole126is formed larger than the stopper hole120. With such a configuration, the slip amount defined by the first stopper116is made smaller than the slip amount defined by the second stopper122.

An operation of the damper device100configured as described above will be described.FIG. 7depicts relationship between a torque T transmitted to the damper device100and a torsional angle θ. When the torque T is input to the damper device100and the torsional angle θ increases to a torsional angle θ1, a slip first occurs on the friction surfaces between the pressure plate106and the first friction material110and the friction surfaces between the second support plate104band the second friction material112. This is because the lowest friction coefficient is the friction coefficient μ1 between the pressure plate106and the first friction material110and between the second support plate104band the second friction material112. In this case, a hysteresis torque T1 represented by the following Equation (3) is generated. In Equation (3), r1 denotes an operation radius (rotation radius) of the first friction material110and W denotes the disc spring load of the disc spring108.

When the torsional angle θ reaches the torsional angle θ2, the projection118abuts on the stopper hole120in the first stopper116, making the pressure plate106and the first friction material110relatively non-rotatable. A slip then occurs on the friction surfaces between the lining plate76and the first friction material110. The slip continues on the friction surfaces between the second support plate104band the second friction material112. In this case, a hysteresis torque T2 represented by the following Equation (4) is generated. In this equation, μ2 is the friction coefficient on the friction surfaces between the lining plate76and the first friction material110. The friction coefficient μ2 is larger than the friction coefficient μ1 and, therefore, the hysteresis torque T2 is larger than the hysteresis torque T1.

When the torsional angle θ further increases and reaches the torsional angle θ3, the projection124abuts on the stopper hole126in the second stopper122, making the second support plate104band the second friction material112relatively non-rotatable. Therefore, the slip between the second support plate104band the second friction material112is regulated. A slip lastly occurs between the lining plate76and the second friction material112. A torque T3 in this case is represented by the following Equation (5). In this equation, μ3 denotes the friction coefficient on the friction surfaces between the lining plate76and the second friction material112. Since the friction coefficient μ3 is the largest based on Equation (5), the torque T3 becomes the largest. The torque T3 is the limiter torque Tlm of the torque limiter mechanism102.

As described above, the two-stage hysteresis torques T1, T2 are realized in the torque limiter mechanism102. Since the torque limiter mechanism102is also used as the hysteresis mechanism, the torque limiter mechanism102is realized that can generate the hysteresis torque with a simple structure. Since the torque limiter mechanism102is disposed on the outer circumferential side of the disc plates56, the first friction material110and the second friction material112have a larger radius (effective radius) r1. Therefore, since a wide range of hysteresis torque from small hysteresis torque to large hysteresis torque can be acquired by adjusting the friction coefficients μ1 to μ3 and the disc spring load of the disc spring108, a degree of freedom of design is significantly improved. Four-stage hysteresis torques can be realized along with the hysteresis mechanism64generating conventional two-stage hysteresis torques.

As described above, according to this example, when the torque T is input to the damper device100, a slip first occurs on the friction surfaces between the pressure plate106and the first friction material110and the friction surfaces between the second support plate104band the second friction material112, and a first hysteresis torque T1 is generated at this point. When the first stopper116is locked, a slip occurs between the lining plate76and the first friction material110and a second hysteresis torque T2 is generated at this point. When the second stopper122is locked, the torque limiter mechanism102acts as a normal torque limiter based on the friction force generated between the lining plate76and the second friction material112. In this way, the torque limiter mechanism102can be realized that enables acquisition of two-stage hysteresis torques.

Third Example

FIG. 8is a cross-sectional view of a torque limiter mechanism152(torque limiter device) of a damper device150that is yet another example of the present invention. The torque limiter mechanism152of this example is disposed as a plurality of mechanisms (at four locations in this example) at regular angular intervals in the circumferential direction rather than being entirely continuously disposed in the circumferential direction as in the examples. As depicted inFIG. 8, the torque limiter mechanism152includes the lining plate76, a pressure plate156, a first friction material158interposed between the lining plate76and the pressure plate156, a support plate160, a second friction material162interposed between the lining plate76and the support plate160, and a clamping member164clamping the pressure plate156and the support plate160from the both ends in the axial direction. The torque limiter mechanism152corresponds to the vehicle torque limiter device of the present invention; the pressure plate156corresponds to the first cover plate of the present invention; the support plate160corresponds to the second cover plate of the present invention; the clamping member164corresponds to the pressing member of the present invention; the first friction material158corresponds to the first friction material of the present invention; and the second friction material162corresponds to the second friction material of the present invention.

The support plate160is formed into an annular plate shape and formed with a bolt hole166for bolt-fastening not depicted and a through-hole168for allowing the clamping member164to penetrate in the axial direction. The support plate160and the pressure plate156are configured to be rotatable around the axial center C and the lining plate76is relatively rotatable to the support plate160and the pressure plate156around the axial center C.

The friction surfaces between the first friction material158and the pressure plate156are configured to be slidable on (relatively rotatable to) each other and the friction surfaces between the first friction material158and the lining plate76are configured to be slidable on (relatively rotatable to) each other. The friction surfaces between the second friction material162and the support plate160are configured to be slidable on (relatively rotatable to) each other and the friction surfaces between the second friction material162and the lining plate76are configured to be slidable on (relatively rotatable to) each other.

The clamping member164(pressing member) is made of spring steel and includes a first abutting portion170having an inner circumferential end portion abutting on the pressure plate156, a second abutting portion172abutting on the support plate160, and a coupling portion174coupling outer circumferential end portions of the first abutting portion170and the second abutting portion172in the axial direction. The clamping member167axially clamps (presses) the pressure plate156and the support plate160with a preset preload (disc spring load W).

A first stopper176(first stopper) is disposed between the pressure plate156and the first friction material158to define (limit) a slip amount (relative rotation amount) between the pressure plate156and the first friction material158. The first stopper176is made up of a column-shaped projection178axially projecting from the friction surface of the pressure plate156adjacent to the first friction material158, and a stopper hole180formed in the first friction material158. The projection178is housed in the stopper hole180to form a backlash L1in the rotation direction for allowing a predetermined slip amount (relative rotation) between the pressure plate156and the first friction material158.

A second stopper182(second stopper) is disposed between the support plate160and the second friction material162to define a slip amount (relative rotation amount) between the support plate160and the second friction material162. The second stopper182is made up of a projection184axially projecting from the friction surface of the support plate160adjacent to the second friction material162, and a stopper hole186formed in the second friction material162. The projection178and the projection184are assumed to have the same shape (external diameter). The projection184is housed in the stopper hole186to form a backlash (gap) L2for defining the slip amount (relative rotation amount) between the support plate160and the second friction material162. The backlash L2is formed larger than the backlash L1of the first stopper176.

FIG. 9is an A-arrow view of the pressure plate156and the first friction material158in the torque limiter mechanism152ofFIG. 8viewed from arrow A ofFIG. 8.FIG. 9is a simplified view and is not drawn in accurate scale etc.

As depicted inFIG. 9, the circular-plate-shaped pressure plate156has the four first friction materials158arranged separately at regular angular intervals in the circumferential direction. InFIG. 9, the first friction material158on the top is denoted by a reference numeral as a first friction material158a, and the first friction materials158are denoted by respective reference numerals as a first friction material158bto a first friction material158dclockwise from the first friction material158a. As depicted inFIG. 9, the first friction materials158ato158dare disposed with respective first stoppers176ato176ddefining a slip amount between the pressure plate156and the first friction materials158. The stopper holes180are denoted by reference numerals (180ato180d) in the same way as the first friction materials158. In this example, each of the disc spring loads W generated by the clamping members164is not changed.

Although the first stoppers176(176ato176d) have the projections178of a common shape, the stopper holes180(180ato180d) have circumferential widths different from each other. Specifically, as depicted inFIG. 9, a groove width Ha-1 of the stopper hole180ais the smallest among the stopper holes180; a groove width Hb-1 of the stopper hole180bis formed larger than the groove width Ha-1 of the stopper hole180a; a groove width Hc-1 of the stopper hole180cis formed larger than the groove width Hb-1 of the stopper hole180b; and a groove width Hd-1 of the stopper hole180dis formed larger than the groove width Hc-1 of the stopper hole180c.

FIG. 10is a B-arrow view of the support plate160and the second friction material162in the torque limiter mechanism152ofFIG. 8viewed from arrow B ofFIG. 8.FIG. 10is a simplified view and is not drawn in accurate scale etc., and the outer circumferential portion of the support plate160is not depicted.

As depicted inFIG. 10, the circular-plate-shaped support plate160has the four second friction materials162arranged separately at regular angular intervals in the circumferential direction. InFIG. 10, the second friction material162on the top is denoted by a reference numeral as a second friction material162a, and the second friction materials162are denoted by respective reference numerals as a second friction material162bto a second friction material162dclockwise from the second friction material162a. As depicted inFIG. 10, the second friction materials162ato162dare disposed with respective second stoppers182ato182ddefining a slip amount between the support plate160and the second friction materials162. The stopper holes186making up the second stoppers182are denoted by reference numerals (186ato186d) in the same way as the second friction materials162.

The projections184of the second stoppers182ato182dhave a shape common with the projections178of the first stoppers176. On the other hand, the stopper holes186ato186dhave circumferential widths different from each other. Specifically, as depicted inFIG. 10, a groove width Ha-2 of the stopper hole186ais the smallest among the stopper holes186; a groove width Hb-2 of the stopper hole186bis formed larger than the groove width Ha-2 of the stopper hole186a; a groove width Hc-2 of the stopper hole186cis formed larger than the groove width Hb-2 of the stopper hole186b; and a groove width Hd-2 of the stopper hole186dis formed larger than the groove width Hc-2 of the stopper hole186c.

Comparing the groove widths (Ha-1 to Hd-1, Ha-2 to Hd-2) including the groove widths (Ha-1 to Hd-1) of the stopper holes180of the first stoppers176, the groove widths are set to relationship represented by the following Equation (6). Since the projections178of the first stoppers176and the projections184of the second stoppers182have the same shape, Equation (6) corresponds to a size of the backlash L, i.e., a level of the slip amount (relative rotation amount) defined (allowed) by the stoppers176and182.

The friction coefficient μ of the friction surfaces between the pressure plate156and the first friction material158ais set to μ1; the friction coefficient of the friction surfaces between the lining plate76and the first friction material158ais set to μ2; the friction coefficient μ of the friction surfaces between the support plate160and the second friction material162ais set to μ1; and the friction coefficient μ of the friction surfaces between the lining plate76and the second friction surface162ais set to μ3. The friction coefficient μ of the friction surfaces between the pressure plate156and the first friction material158bis set to μ1; the friction coefficient μ of the friction surfaces between the lining plate76and the first friction material158bis set to μ4; the friction coefficient μ of the friction surfaces between the support plate160and the second friction material162bis set to μ1; and the friction coefficient μ of the friction surfaces between the lining plate76and the second friction surface162bis set to μ5. The friction coefficient μ of the friction surfaces between the pressure plate156and the first friction material158cis set to μ1; the friction coefficient μ of the friction surfaces between the lining plate76and the first friction material158cis set to μ6; the friction coefficient μ of the friction surfaces between the support plate160and the second friction material162cis set to μ1; and the friction coefficient μ of the friction surfaces between the lining plate76and the second friction surface162cis set to μ7. The friction coefficient μ of the friction surfaces between the pressure plate156and the first friction material158dis set to μ1; the friction coefficient μ of the friction surfaces between the lining plate76and the first friction material158dis set to μ8; the friction coefficient μ of the friction surfaces between the support plate160and the second friction material162dis set to μ1; and the friction coefficient μ of the friction surfaces between the lining plate76and the second friction surface162dis set to μ9.

The friction coefficients μ1 to μ9 are set to relationship represented by the following Equation (7). In other words, equal and smallest values are set as a friction force F1 generated between the pressure plate156and the first friction material158a, the friction force F1 generated between the support plate160and the second friction material162a, the friction force F1 generated between the pressure plate156and the first friction material158b, the friction force F1 generated between the support plate160and the second friction material162b, the friction force F1 generated between the pressure plate156and the first friction material158c, the friction force F1 generated between the support plate160and the second friction material162c, the friction force F1 generated between the pressure plate156and the first friction material158d, and the friction force F1 generated between the support plate160and the second friction material162d. A friction force F2 generated between the lining plate76and the first friction material158ais larger than the friction force F1. A friction force F3 generated between the lining plate76and the second friction surface162ais larger than the friction force F2. A friction force F4 generated between the lining plate76and the first friction material158bis larger than the friction force F3. A friction force F5 generated between the lining plate76and the second friction surface162bis larger than the friction force F4. A friction force F6 generated between the lining plate76and the first friction material158cis larger than the friction force F5. A friction force F7 generated between the lining plate76and the second friction surface162cis larger than the friction force F6. A friction force F8 generated between the lining plate76and the first friction material158dis larger than the friction force F7. A friction force F9 generated between the lining plate76and the second friction surface162dis larger than the friction force F8. The relationship is represented by the following Equation (8).

Based on Equations (7) and (6), for the friction materials having the friction surfaces with the larger friction coefficients μ set between the friction materials and the lining plate76, the slip amounts defined by the first stoppers176and the second stoppers182are set larger.

An operation of the torque limiter mechanism152configured as described above will be described.FIG. 11depicts relationship between a torque transmitted to the damper device150of this example and a torsional angle θ. When the torque T is input to the damper device150, the torsional angle θ increases in proportion. When the torsional angle θ reaches θ1, a slip occurs on the friction surfaces having the friction coefficient μ of μ1 (the friction surfaces between the pressure plate156and the first friction materials158ato158dand the friction surfaces between the support plate160and the second friction materials162ato162d). In this case, a hysteresis torque T1 (=r1×μ1×W) is generated.

When the torsional angle θ reaches θ2, the projection178abuts on the stopper hole180in the first stopper176a, regulating a slip between the pressure plate156and the first friction material158a. A slip then occurs between the lining plate76and the first friction material158ahaving the friction coefficient μ of μ2. The slip continues on the friction surfaces having the friction coefficient μ of μ1 other than the friction surfaces regulated by the first stopper176a. In this case, a hysteresis torque T2 (=r1×μ2×W) is generated until the torsional angle θ reaches θ3.

When the torsional angle θ reaches θ3, the projection184abuts on the stopper hole186ain the second stopper182a, regulating a slip between the support plate160and the second friction material162a. A slip then occurs on the friction surfaces between the lining plate76and the second friction surface162ahaving the friction coefficient μ of μ3. The slip continues on the friction surfaces having the friction coefficient μ of μ1 other than the friction surfaces regulated by the first stopper176aand the second stopper182aand the friction surfaces having the friction coefficient μ of μ2. In this case, a hysteresis torque T3 (=r1×μ3×W) is generated until the torsional angle θ reaches θ4.

When the torsional angle θ reaches θ4, the projection178abuts on the stopper hole180bin the first stopper176b, regulating a slip between the pressure plate156and the first friction material158b. A slip then occurs between the lining plate76and the first friction material158bhaving the friction coefficient μ of μ4. The slip continues on the friction surfaces having the friction coefficient μ of μ1 other than the friction surfaces regulated by the first stoppers176a,176b, and the second stopper182aand the friction surfaces having the friction coefficients μ of μ2 and μ3. In this case, a hysteresis torque T4 (=r1×μ4×W) is generated until the torsional angle θ reaches θ5.

When the torsional angle θ reaches θ5, the projection184abuts on the stopper hole186bin the second stopper182b, regulating a slip between the support plate160and the second friction material162b. A slip then occurs between the lining plate76and the second friction material162bhaving the friction coefficient μ of μ5. The slip continues on the friction surfaces having the friction coefficient μ of μ1 other than the friction surfaces regulated by the first stoppers176a,176band the second stoppers182a,182band the friction surfaces having the friction coefficients μ of μ2 to μ4. In this case, a hysteresis torque T5 (=r1×μ5×W) is generated until the torsional angle θ reaches θ6.

When the torsional angle θ reaches θ6, the projection178abuts on the stopper hole180cin the first stopper176c, regulating a slip between the pressure plate156and the first friction material158c. A slip then occurs between the lining plate76and the first friction material158chaving the friction coefficient μ of μ6. The slip continues on the friction surfaces having the friction coefficient μ of μ1 other than the friction surfaces regulated by the first stoppers176ato176cand the second stoppers182a,182band the friction surfaces having the friction coefficients μ of μ2 to μ5. In this case, a hysteresis torque T6 (=r1×μ6×W) is generated until the torsional angle θ reaches θ7.

When the torsional angle θ reaches θ7, the projection184abuts on the stopper hole186cin the second stopper182c, regulating a slip between the support plate160and the second friction material162c. A slip then occurs between the lining plate76and the second friction material162chaving the friction coefficient μ of μ7. The slip continues on the friction surfaces having the friction coefficient μ of μ1 other than the friction surfaces regulated by the first stoppers176ato176cand the second stoppers182ato182cand the friction surfaces having the friction coefficients μ of μ2 to μ6. In this case, a hysteresis torque T7 (=r1×μ7×W) is generated until the torsional angle θ reaches θ8.

When the torsional angle θ reaches θ8, the projection178abuts on the stopper hole180din the first stopper176d, regulating a slip between the pressure plate156and the first friction material158d. A slip then occurs between the lining plate76and the first friction material158dhaving the friction coefficient μ of μ8. The slip continues on the friction surfaces having the friction coefficient μ of μ1 other than the friction surfaces regulated by the first stoppers176ato176dand the second stoppers182ato182cand the friction surfaces having the friction coefficients μ of μ2 to μ7. In this case, a hysteresis torque T8 (=r1×μ8×W) is generated until the torsional angle θ reaches θ9.

When the torsional angle θ reaches θ9, the projection184abuts on the stopper hole186din the second stopper182d, regulating a slip between the support plate160and the second friction material162d. A slip then occurs between the lining plate76and the second friction material162dhaving the friction coefficient μ of μ9. The slip continues on the friction surfaces having the friction coefficients μ of μ2 to μ8. In this case, a torque T9 (=r1×μ9×W) is generated and the torque T9 is the limit torque Tlm of this example.

As described above, by circumferentially arranging pluralities of the first friction materials158and the second friction materials162(158ato158d,162ato162d), the hysteresis torques T1 to T8 can be acquired in multiple stages.

As described above, according to this example, by differentiating the friction coefficients μ1 to μ9 from each other on the friction surfaces of a plurality of the first friction materials158ato158dand a plurality of the second friction materials162ato162dand the lining plate76, the torque limiter mechanism152can be implemented that enables acquisition of multistage hysteresis torque with a simple structure.

Fourth Example

FIGS. 12 to 14depict other forms of the projections and the stopper holes making up the stopper90, first stoppers116,176, and second stoppers122,182of the examples described above. A stopper200ofFIG. 12is made up of a column-shaped projection204formed on a pressure plate202and a bottomed-cylinder-shaped stopper hole208formed in a friction material206, for example. A reinforcing member210consisting of bottomed-cylinder-shaped metal is embedded in a wall surface of the stopper hole208in a fitting manner. As a result, the projection204abuts on the reinforcing member210rather than directly abutting on a friction material resin making up the friction material206. Therefore, deterioration in durability and damage are prevented from occurring due to direct abutting on the projection204to the friction material resin. The shape of the reinforcing member210may be changed as needed depending on the shape of the stopper hole208.

A stopper220ofFIG. 13is made up of a column-shaped projection224formed on a pressure plate222and a cylindrical stopper hole228formed in a friction material226. The friction material226of this example has a structure formed by attaching a first friction material232and a second friction material234to an arc-shaped metal plate230. A circumferential end portion of the metal plate230projects into the stopper hole228. When the stopper220is formed in this way, the projection224abuts on the circumferential end portion of the metal plate230without abutting the friction material resin. Therefore, deterioration in durability and damage are prevented from occurring due to direct abutting on the projection224to the friction material resin.

A stopper240ofFIG. 14is made up of a column-shaped projection246formed on a pressure plate242and a cylindrical stopper hole250formed in a friction material248. A cylindrical rubber member252is fitted to an outer circumferential surface of the projection246. When the stopper240is configured in this way, the projection246does not directly contact the friction material resin of the friction material248and a shock at the time of contact is alleviated. As depicted inFIG. 15, when the projection246contacts the rubber member252at the torsional angle θ2, torsional characteristics are changed by the rubber member252and a change from the hysteresis torque T1 to the limiter torque T2 is gradually made along with an increase in the torsional angle θ. Therefore, a sharp change is prevented when the hysteresis torque T1 is switched to the limiter torque T2. The shape of the rubber member252may be changed as needed depending on the shape of the projection246.

Although the cylindrical rubber member252is fitted to the projection246inFIG. 14, a spring member may be interposed between the projection246and the friction material248. If the spring members are disposed on the both ends in the circumferential direction, a function of automatically centering the hysteresis mechanism is added.

Although the examples of the present invention have been described in detail with reference to the drawings, the present invention is applied in other forms.

For example, although all the projections have a columnar shape in the examples, this is not a limitation and the projection may have a square shape etc. The stopper hole may freely be changed depending on a shape of the projection. In other words, the shapes of the projection and the stopper hole may freely be changed as long as the stopper is configured to define a circumferential slip.

Although the torque limiter mechanism152realizes eight-stage hysteresis torques, a change can freely be made by changing the numbers of friction materials etc., arranged in the circumferential direction.

Although the hysteresis mechanism64is disposed on the damper device in the examples, the hysteresis torque can be generated in the torque limiter mechanism68and, therefore, the hysteresis mechanism can be omitted.

Although a plurality of the first friction materials158and a plurality of the second friction materials162are used in the torque limiter mechanism152in the examples, the torque limiter mechanism152may be configured such that only the first friction materials158are disposed with the first stoppers176or that only the second friction materials162are disposed with the second stoppers182.

In the examples, the first friction materials and the second friction materials may be interposed at positions with left and right reversed.

The above description is merely an embodiment and the present invention may be implemented in variously modified and improved forms based on the knowledge of those skilled in the art.

NOMENCLATURE OF ELEMENTS