JPH0756330B2 - Differential rotation sensitive differential limiting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a rotation difference sensing device that converts a fluid pressure generated according to a rotation difference between left and right wheels into a differential limiting torque to limit the differential between the left and right wheels. Type differential limiting device.

(Prior Art) Conventionally, as a rotation difference sensitive type differential limiting device, for example, a device described in JP-A-61-62642 is known.

In this conventional source, there is shown a rotation difference sensitive differential limiting means provided on an outer peripheral portion parallel to the output shaft of the differential device,
The differential limiting means includes a cam having cam surfaces provided on a pair of side gears, a pair of plungers slidably provided on a sleeve between the cams, and a fluid communicating between the plungers via an orifice. It is configured with a room.

(Problems to be Solved by the Invention) However, such a conventional device has various problems that cannot be put to practical use, as described below.

When the differential rotation occurs, the oil receives a force due to the flow of the oil and is adiabatically compressed. Therefore, the volume of the oil expands as the oil temperature rises. In particular, since the rotation difference sensitive type differential limiting means is provided on the outer peripheral portion parallel to the output shaft of the differential device, centrifugal force acts on the oil inside, and the volume of the oil has a large expansion degree.

However, since the rotation difference sensitive differential limiting means does not have an accumulator chamber and there is no discharge valve from the accumulator chamber, a strong force is generated as an internal force in this system, the head of the plunger is crushed, The cam surface may peel.

Although the oil inside the plunger is sealed,
As described above, when a large internal force is applied, the amount of oil in the inside changes due to the action of either leaking the oil from the seal or sucking the oil from the outside to some extent.

If the oil leaks even a little, the reduction of the oil due to the differential is unavoidable, and the function of the device is deteriorated. Also, if the structure of the seal is such that it sucks the external oil, the internal oil gradually increases due to the differential operation, and the function of the device stops.

Since the plungers are pressed against the left and right cases with a great force during the differential operation, it is necessary to make the rigidity of this case extremely strong. Also, when the case is expanded by the force of the plunger, the force of this expansion will be taken up by the side bearings (not shown) supporting the case.
It is necessary to use a large size side bearing.

Therefore, the present applicant has proposed a differential limiting device which solves the above problems by the specification and drawings of Japanese Utility Model Application No. 62-184485.

However, in the differential limiting device of the prior application, the throttle opening degree by the orifice is constant, and the differential limiting torque characteristic is that the left and right wheel relative rotational speed (differential rotation) is x and the left and right wheel torque difference ( When the differential limiting torque is y, y =
It is possible to obtain only a quadratic function curve characteristic represented by ax ² such as A or B in FIG. 3, that is, a characteristic in which the gain is small in a region where the differential rotation is small and the gain sharply increases as the differential rotation increases. Can not.

Therefore, when the characteristic of A is selected, in the case of a vehicle such as sports running, when the driver is an expert, the accelerator is turned on during turning to increase the rotation of the inner wheel and to apply a large torque to the outer wheel side. , It is possible to obtain a driving force and at the same time control to reduce the side force of the tire to accelerate the turning.

However, for an ordinary driver who is not accustomed to sports driving like this, if the accelerator is pressed too much during turning, the torque on the outer wheel becomes too large and the side force is extremely reduced, which may cause the vehicle to spin. .

On the other hand, when the characteristic of B is selected in order to avoid such a situation, the differential limiting torque is not generated because the differential rotation is not significantly generated, and thus the split having a difference in friction coefficient between the left and right road surfaces. When traveling on the μ road, the effect of the differential limiting device is low, and the effect of suppressing tack-in and braking during turning is low.

Further, as a piston pump type torque transmission device in which a one-way valve which is opened and closed by fluid pressure is provided instead of the orifice of a constant opening, for example, Japanese Patent Publication No. 54-41.
The devices described in Japanese Patent No. 34 and Japanese Patent No. 87203 are known.

However, since these one-way valves are valves that press a ball or valve element with a coil spring, there is almost no flow throttling effect (orifice effect), and when the load exceeds the set load by the coil spring, the hydraulic oil opens greatly. Will flow out in a large amount, that is, it will only open and close like ON-OFF.

Therefore, regarding the transfer torque characteristic, the torque increases due to the valve being fully closed in the differential rotation region where the fluid pressure below the set load is applied, but the valve is repeatedly opened and closed in the differential rotation region where the fluid pressure exceeding the set load is applied. The transmission torque is kept constant, and large torque transmission cannot be performed in a high differential rotation range, which is important when used as a differential limiting device.

A rotation difference sensitive differential limiting device to which a viscous coupling is applied is known. In this viscous coupling, a highly viscous silicone oil or the like is filled as shown in C of FIG. Therefore, the gain decreases in the high differential rotation range due to the decrease in viscosity in the high shear speed region, and an appropriate differential limiting torque is generated in the low differential rotation region. In a large region, it is impossible to expect an appropriate increase in driving force.

Therefore, if the characteristic shown in D of FIG. 3 is selected in order to obtain an appropriate increase in the driving force in the region where the differential rotation is large by viscous coupling, a large differential limiting torque is obtained even in the region where the differential rotation is small. Therefore, the initial understeer, that is, the problem that the turning radius becomes large when acceleration is applied during turning, occurs.

The present invention has been made by paying attention to the problems as described above, and has a very simple structure, but is suitable for a general driver, that is, the optimum differential limiting torque characteristic, that is, a range from a low differential rotation region to a high differential rotation region. It is an issue to develop a rotation-sensitive differential limiting device that can obtain linear characteristics with almost constant gain.

(Means for Solving the Problems) In order to solve the above problems, in the rotation difference sensitive differential limiting device of the present invention, the differential case connected to the drive input side is rotatable via a pinion shaft. The supported pinion, the pair of side gears meshing with the pinion, and the two output shafts connected to the side gears are the rotational difference to which the driving force is transmitted through the differential limiting means provided in the middle of the driving force transmission path. In the sensitive differential limiting device, the differential limiting means is provided on a cam surface formed on an inner surface of one member of the differential case and a pair of side gears that rotate relative to each other, and on the other member, Radially arranged cam bodies that reciprocate in the radial direction while slidingly contacting the cam surface by relative rotation, a plurality of fluid chambers that change in volume as the cam bodies reciprocate, and the respective fluid chambers. A plurality of fluid passages communicating with the accumulator chamber, a plurality of fluid passages communicating between the fluid chambers and the accumulator chamber, and a single fluid passage arranged so as to simultaneously close the plurality of accumulator chamber-side open ends of the fluid passages. It consists of a valve plate and one bolt that fixes the valve plate at the center position equidistant from the opening ends on the accumulator chamber side. The valve opening that serves as an outflow path toward the accumulator chamber is defined by the fluid chamber pressure and the accumulator chamber pressure. And a plate valve for linearly adjusting the differential limiting torque characteristic with respect to the differential rotation by changing the flexural deformation of the valve plate that flexes in accordance with the differential pressure between To do.

(Operation) When there is no differential rotation, the driving force input from the differential case is evenly distributed to both output shafts.

However, even when there is no differential rotation, when the cam body rotates at a high speed when traveling straight on a highway at high speed, centrifugal force acts on the cam body, and the centrifugal force causes the cam body to move. It will be pressed against the cam surface, and will exert some limited differential function.

When differential rotation occurs, the cam body slidingly contacting the cam surface reciprocates in the radial direction due to the differential rotation. When the volume of the fluid chamber is reduced by moving toward the center of the rotation axis in this reciprocation,
The pressure in the fluid chamber rises due to the flow resistance due to the plate bubbles, and the fluid pressure, which is the product of the generated hydraulic pressure and the pressure receiving area of the cam body, becomes the force that presses the cam body against the cam surface, and this pushing force acts as the differential limiting torque. However, the differential is limited so that the driving force is distributed on the high-speed rotation side to be small and the constant-speed rotation side is large.

Further, the differential limiting torque characteristic of this device is obtained by the plate valve that uses the flexural deformation of the valve plate that flexes in response to the fluid chamber pressure for the valve opening that serves as the outflow passage toward the accumulator chamber. When compared with the quadratic function characteristic of a fixed orifice with a constant opening, the following characteristic change is observed.

First, in the small differential rotation range where the differential rotation occurs and the fluid chamber pressure is at the low pressure level, the plate valve is kept fully closed, and the rising of the differential limiting torque is observed.

Then, the fluid chamber pressure rises as the differential rotation increases, the plate valve begins to bend, and the working fluid outflow regulation is strong until the valve opening becomes the same as the fixed orifice. Therefore, the differential limiting torque is higher than the quadratic function characteristic.

Further, when the differential rotation increases and the valve opening due to the flexural deformation of the plate valve increases and exceeds the valve opening of the fixed orifice, the outflow regulation of the working fluid becomes weaker, resulting in a quadratic function characteristic. Compared to this, the differential limiting torque is lower.

That is, the quadratic function characteristic is corrected in the linear direction, and the differential limiting torque characteristic shows a linear characteristic in which the gain is constant from the low differential rotation region to the high differential rotation region.

Therefore, while the fluid chamber pressure generated corresponding to the differential rotation is used as a valve actuator in an extremely simple configuration, the differential limiting torque characteristic most suitable for a general driver, that is, from the region where the differential rotation is low, It is possible to obtain a linear characteristic in which the gain is almost constant up to a high region.

Further, since the degree of flexural deformation corresponding to the fluid chamber pressure can be set by the flexural strength of the plate valve or the like, it is possible to match the differential limiting torque characteristics with various required characteristics.

The plate valve, which restricts the outflow from the fluid chamber when differential rotation occurs, has one valve rate that is arranged so as to simultaneously close the plurality of accumulator chamber side opening ends of the fluid passage, and the plurality of accumulator chamber side opening ends. Since it is composed of one bolt that fixes the valve plate at the equidistant center position, it is necessary to store the plate valve in a limited space as compared with the case where the plate valves are individually provided at the opening ends on the accumulator chamber side. This is useful for reducing the size and weight of the device.

Further, the valve opening at the plurality of accumulator chamber side opening ends is kept constant due to the bending deformation of the valve plate, and the valve opening variation is different as compared with the case where the plate valves are individually provided at the plurality of accumulator chamber side opening ends. It can be suppressed.

Furthermore, even when matching the differential limiting torque characteristics with various required characteristics, it can be adjusted easily by setting the thickness of one valve plate, the material and shape, or the tightening torque of one bolt. Adjustments can be made by matching.

(Example) Hereinafter, the present invention will be described based on an example shown in the drawings.

First, the configuration of the embodiment will be described.

As shown in FIG. 1, in the rotation difference sensitive differential limiting device of the embodiment, the rotation difference sensitive differential limiting device 2 having the differential limiting function is provided in the differential device 1 having the differential function. It is a device that is combined in a built-in state, and the differential unit 1 is rotatably supported via a differential case 10 into which a driving force is input via a drive pionion 3 and a ring gear 4 and a pinion shaft 11. The pinion 12, the pair of side gears 13 and 14 meshing with the pinion 12, and the two output shafts 15 and 16 connected to the side gears 13 and 14 are provided.

Then, the driving force is transmitted to the output shafts 15 and 16 in an even distribution when no differential rotation occurs, and when the differential rotation occurs, only the differential limiting torque by the rotation difference sensitive differential limiting means 2 is generated. The driving force is transmitted from the high rotation side to the low rotation side.

As shown in FIGS. 1 and 2, the rotation difference sensitive differential limiting means 2 is a cam formed on the inner surface of a cam case 20 splined to one of the output shafts 15 and 16. A driving piston 40 (cam body) which is provided on the surface 21 and a rotor 30 which is spline-coupled to the other output shaft 16 and which radially reciprocates while slidingly contacting the cam surface 21 by differential rotation; A cylinder chamber 50 (fluid chamber) whose volume changes with the reciprocating movement of the driving piston 40,
A balance oil passage 60 (fluid passage) that communicates the opposing cylinder chambers 50, a regulator oil passage 80 that communicates the accumulator chamber 70 with each cylinder chamber 50 via a one-way valve 81, and an accumulator from the balance oil passage 60. A valve plate 91 provided on the opening end surface of the axially branched oil passage 61 toward the chamber 70 and a plate valve 90 (variable opening valve) constituted by a bolt 92 are provided.

The cam case 20 is provided via a cam case cover 22 that is spline-coupled to the output shaft 15, has a cam surface 21 formed on the inner surface, and a side gear 14 on the outer side.
Are formed. That is, the output shaft 15 and the cam case cover
22, the cam case 20, and the side gear 14 are an integral rotating member.

The rotor 30 is spline-coupled to the output shaft 16 and is inserted in the cam surface 21 of the cam case cover 20. The rotor 30 is disposed at a position facing the cam surface 21 at equal intervals in the radial direction. A cylinder hole 31 is formed at the location.

The driving pistons 40 are six cam members that are oil-tightly provided in the cylinder hole 31 by the seal ring 41. The sliding contact surface with the cam surface 21 ensures smooth contact movement and high Hertzian contact stress. In order to do so, it is formed into a spherical surface.

The cylinder chamber 50 is formed between the cylinder hole 31 and the driving piston 40 such that the chamber volume changes depending on the stroke position of the piston 40.

Three balance oil passages 60 are formed in the rotor 30, and connect the opposing cylinder chambers 50, 50 of the same phase in the reciprocating stroke of the driving piston 40.

The accumulator chamber 70 is a chamber for temporarily increasing and decreasing the amount of oil by temporarily storing and discharging hydraulic oil, and an accumulator piston 71 provided in the rotor 30 in an oil-tight state so as to reciprocate, and the piston 71 and a spring retainer. And a spring 73 interposed between the spring 73 and 72.

The accumulator piston 71 is provided with a piston seal 74, and the rotor 30 at the position where the piston seal 74 is provided is provided with a valve hole 75 in the radial direction.
When the accumulator chamber 70 exceeds the set pressure and the accumulator piston 71 moves to the right in the drawing, the valve hole 75 communicates with the accumulator chamber 70 to exert a relief valve function of releasing hydraulic oil.

The regulator oil passage 80 is an oil passage provided for adjusting the hydraulic pressure of the cylinder chamber 50, and by connecting the accumulator chamber 70 and each cylinder chamber 50 through the one-way valve 81, the cylinder chamber pressure is increased. When the one-way valve 81 is opened at a pressure lower than the chamber pressure, pressurized hydraulic oil is supplied from the accumulator chamber 70 to each cylinder chamber 50.

The plate valve 90 includes a valve plate 91 arranged at the opening end faces of three axial branch oil passages 61 extending from the balance oil passage 60 to the accumulator chamber 70, and the valve plate 91.
The bolt fixing position is the center position of these three axially branched oil passages 61, that is, the center axis position.

Then, by utilizing the flexural deformation of the valve plate 91 toward the accumulator chamber 70 side, which occurs corresponding to the differential pressure between the internal pressure of the cylinder chamber 50 and the internal pressure of the accumulator chamber 70 (actually, it is substantially equal to the internal pressure of the cylinder chamber 50). The valve opening is gradually increased from the fully closed state where the valve plate 91 is in close contact with the opening end surface of the axial branch oil passage 61 in accordance with the increase in the differential pressure.

Next, the operation of the embodiment will be described.

(B) Non-differential rotation When driving straight on low- and medium-speed dry asphalt roads, etc., there is no difference in rotational speed (differential rotation) between the left and right wheels connected to the output shafts 15 and 16. When there is no relative rotation between the case cover 20 and the rotor 30, the driving piston 40
Does not reciprocate in the radial direction, so the differential case
The engine driving force input from 10 is evenly distributed to the output shafts 15 and 16.

However, even if the left and right wheels do not rotate differentially, the output shaft 1
Centrifugal force acts on the driving piston 40 provided in the rotor 30 that rotates at high speed with the rotation of 5, 16
This centrifugal force causes the driving piston 40 to move to the cam surface 21.
And the differential limiting torque is generated.

Therefore, when the vehicle travels straight ahead at high speed, the function of limiting the differential is somewhat exerted, and the stability of traveling straight ahead at high speed can be improved.

(B) When differential rotation occurs When the vehicle rotates on a rough road or when one wheel is stuck, if there is a difference in rotational speed between the left and right wheels connected to the output shafts 15 and 16, the case cover
Relative rotation also occurs between the rotor 20 and the rotor 30, and due to this relative rotation, the driving piston 40 slidingly contacting the cam surface 21 reciprocates in the radial direction. When attempting to reduce the volume, the pressure in the cylinder chamber 50 increases due to the flow resistance generated by the outflow regulation by the plate valve 90, and the hydraulic pressure that is generated by multiplying the generated hydraulic pressure with the pressure receiving area of the piston 40 cams the driving piston 40. The force acts on the surface 21, and this force acts as a differential limiting torque, and the differential is limited so that the distribution of the driving force is reduced on the high speed rotation side and increased on the low speed rotation side.

And, the differential limiting torque characteristic by the embodiment device is a plate valve 90 that changes the valve opening degree, which is the outflow path toward the accumulator chamber 70, from fully closed in accordance with the differential pressure between the cylinder chamber pressure and the accumulator chamber pressure. Since it is used, the following characteristic changes are observed when compared with the quadratic function characteristic by the fixed orifice having a constant opening shown by the characteristic A in FIG.

First, in the small differential rotation range up to the differential rotation ΔN ₁ where the differential rotation ΔN occurs and the fluid chamber pressure becomes the same pressure level as the accumulator chamber pressure, the plate valve 90 should be kept fully closed. The rising of the differential limiting torque T _LSD is seen at.

And, from the fully closed plate valve 90 due to the increase of the differential rotation ΔN to the differential rotation ΔN ₂ where the valve opening becomes the same as the fixed orifice, the outflow regulation of the hydraulic oil is strengthened, that is, the flow resistance is high. As a result, the differential limiting torque T _LSD is higher than the quadratic function characteristic.

Furthermore, when the differential rotation ΔN rises and exceeds the differential rotation ΔN _{2 at} which the valve opening is the same as the fixed orifice, the outflow regulation of the hydraulic oil is weakened, that is, the flow resistance is low, The differential limiting torque T _LSD is lower than that of the quadratic function characteristic.

That is, by correcting the quadratic function characteristic A in the linear direction,
As the differential limiting torque characteristic, as shown by the characteristic E in FIG. 3, a linear characteristic is shown in which the gain is substantially constant from a low differential rotation ΔN region to a high differential rotation ΔN region.

Therefore, when the differential rotation ΔN is low, it is sufficient to prevent understeer in the initial stage of turning, and when the differential rotation ΔN is medium rotation, improvement of running performance on the split μ road, suppression of tuck-in, and turning. Highly effective for braking inside,
When the differential rotation ΔN is high, even if the accelerator is turned on, the torque transmission to the outer wheel side is so great that the tire loses the side force on the snow-covered road (μ = 0.3) or the wet road surface (μ = 0.45). It is possible to obtain the optimum differential limiting torque T _LSD characteristic that can prevent the rise.

As described above, the effects listed below are obtained in the rotation difference sensitive differential limiting device of the embodiment.

Since the plate valve 90 uses the differential pressure generated corresponding to the differential rotation ΔN as a valve actuator, the configuration is extremely simple, and the number of parts and the cost are not increased.

Optimal differential rotation for ordinary drivers △ N
It is possible to obtain a linear differential limiting torque characteristic in which the gain is almost constant from a low region to a high region.

Since the opening degree of the valve due to the differential pressure can be set by the valve bending strength or the like, it is possible to match the differential limiting torque characteristics with various required performances.

That is, the differential limiting torque characteristics are the thickness and material of the valve plate 91, the shape setting of the valve plate 91 (preload is given by making it slightly umbrella-shaped, etc.) and the bolt 92.
By adjusting by tightening torque setting, etc., it is possible to easily match the required performance of the adaptive vehicle.

Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and the present invention can be applied even if there is a design change or the like within a range not departing from the gist of the present invention. included.

For example, the plate valve 90 of the embodiment is a valve that linearly changes the valve opening degree in accordance with the differential pressure between the fluid pressure and the accumulator chamber pressure, but only the fluid chamber pressure is used as the valve operating pressure. A plate valve that linearly changes the opening may be used.

(Effects of the Invention) As described above, in the rotation difference sensitive differential limiting device of the present invention, the accumulator serves as the means for restricting the outflow from the fluid chamber when the differential rotation of the differential limiting means occurs. The valve opening, which becomes the outflow path toward the chamber, is changed by utilizing the bending deformation of the valve plate that bends in response to the fluid chamber pressure,
Since the device is equipped with a plate valve that linearly adjusts the differential limiting torque characteristic with respect to the differential rotation, the differential limiting torque characteristic that is most suitable for ordinary drivers, that is, the differential rotation It is possible to obtain a linear characteristic in which the gain is substantially constant from a low region to a high region, and it is possible to match the differential limiting torque characteristic with various required characteristics.

In addition, the plate valve fixes one valve plate arranged so as to simultaneously close the plurality of accumulator chamber-side opening ends of the fluid path and the valve plate at a central position equidistant from the plurality of accumulator chamber-side opening ends. Since it is configured with one bolt, the plate valve can be housed in a limited space compared to the case where the plate valve is provided at each of the opening ends on the accumulator chamber side, which is useful for reducing the size and weight of the device. However, it is possible to suppress variations in the valve opening at the plurality of accumulator chamber-side open ends due to the bending deformation of the valve plate. Furthermore, even when matching the differential limiting torque characteristics with various required characteristics, it can be adjusted easily by setting the thickness of one valve plate, the material and shape, or the tightening torque of one bolt. Adjustments can be made by matching.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional plan view showing a rotation difference sensitive differential limiting device according to an embodiment of the present invention, and FIG. 2 is a vertical front view showing a rotation difference sensitive differential limiting device taken along the line I-I in FIG. FIG. 3 is a differential limiting torque characteristic diagram. 1 ... Differential means 2 ... Rotation-sensitive differential limiting means 10 ... Differential case 11 ... Pinion shaft 12 ... Pinion 13,14 ... Side gear 15,16 ... Output shaft 20 ... Case cover 21 ... Cam surface 30 ... Rotor 40 ... Driving piston (cam body) 50 ... Cylinder chamber 60 ... Balance oil passage (fluid passage) 70 ... Accumulator chamber 80 ... Regulator oil passage 90 ... Plate valve (variable opening valve)

Claims (1)

[Claims] 1. A differential case connected to a drive input side, a pinion rotatably supported via a pinion shaft, a pair of side gears meshing with the pinion, and two output shafts connected to the side gears. Is a rotation-difference sensitive differential limiting device in which driving force is transmitted via differential limiting means provided in the middle of the driving force transmission path, wherein the differential limiting means is a relative case of the differential case and a pair of side gears. A cam surface formed on the inner surface of one of the two rotating members, and a cam body provided on the other member and radially arranged to reciprocate in the radial direction while slidingly contacting the cam surface by relative rotation, and the cam body A plurality of fluid chambers that change in volume with the reciprocating movement of the plurality of fluid chambers; One valve plate arranged so as to block the side opening end at the same time, and one bolt that fixes the valve plate at a central position equidistant from the plurality of accumulator chamber side opening ends, and flows toward the accumulator chamber. A plate valve that changes the valve opening degree that serves as a path by using the flexural deformation of the valve plate that flexes in response to the fluid chamber pressure, and linearly adjusts the differential limiting torque characteristics for differential rotation, A differential rotation sensitive differential limiting device characterized by being means.