JPH0775946B2 - 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 device, a rotation difference sensitive differential limiting means is provided on an outer peripheral portion parallel to the output shaft of the differential device, and the differential limiting means includes a cam having cam surfaces provided on a pair of side gears, A pair of plungers slidably provided on the sleeve between the cams and a fluid chamber communicating between the plungers via an orifice are provided.

(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 expands significantly.

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, it may cause some leakage of oil from the seal or suction of external oil. Then the amount of oil inside changes.

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) that support the case, so use a larger size side bearing. There is a need to.

Therefore, the present applicant has proposed a differential limiting device that solves the above problems by the specification and drawings of Japanese Patent Application No. 62-184485 (see Japanese Utility Model Application Laid-Open No. 1-87350).

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 =
Only a parabolic cam coupling characteristic such as A or B in FIG. 4 represented by ax ² can be obtained.

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 control the speed of turning by reducing the side force of the tire at the same time as obtaining the driving force, but in the case of an ordinary driver who is not accustomed to sports driving like this, if the accelerator is pressed too much during turning, torque to the outer wheel will be increased. Is 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, although a viscous coupling is known as a rotation difference sensitive differential limiting device, this viscous coupling has characteristics shown in C of FIG. 4, and an appropriate differential limiting torque is obtained in a region where the differential rotation is small. However, it is not possible to expect an appropriate increase in driving force in a region where the differential rotation is large.

Therefore, if the characteristic shown in D of FIG. 4 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 in view of the above problems, and it is an object of the present invention to develop a rotation-difference-sensitive differential limiting device that can obtain an optimum differential limiting torque characteristic regardless of the magnitude of differential rotation. And

(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 rotatably supported via a pinion shaft. Of the pinion, the pair of side gears meshing with the pinion, and one of the two output shafts connected to the side gear, the rotation difference in which the driving force is transmitted from the side gear to the one output shaft through the differential limiting device. In the sensitive differential limiting device, the differential limiting means is provided on the differential case and a cam surface formed on the inner surface of one of the two members of the 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 making circumferential contact with the cam surface by relative rotation, a plurality of fluid chambers that change in volume as the cam bodies reciprocate, and each fluid Provided at the end of the fluid passage communicating with the chamber, when the fluid chamber pressure is below a predetermined pressure, the flow passage toward the accumulator chamber is throttled, and when the pressure exceeds the predetermined pressure, the flow passage toward the accumulator chamber is opened according to the fluid chamber pressure. And a variable orifice.

(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. By being pressed against the cam surface, a limited differential function is exerted.

When differential rotation occurs, this differential rotation causes the cam body that makes circumferential contact with the cam surface to reciprocate in the radial direction, and of this reciprocal movement, toward the center of the rotation axis, the variable orifice is used to reduce the volume of the fluid chamber. The pressure in the fluid chamber rises due to the flow resistance due to, and the hydraulic pressure obtained by multiplying 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 pressing force acts as the differential limiting torque and drives. The differential is limited so that the force distribution is reduced on the high speed rotation side and increased on the low speed rotation side.

The differential limiting torque characteristic of this device is such that when the fluid chamber pressure is below a predetermined pressure, the flow passage toward the accumulator chamber is throttled, and when the pressure exceeds the predetermined pressure, the flow passage toward the accumulator chamber is variable according to the fluid chamber pressure. Since the orifice is used, the cam coupling characteristic expressed by a quadratic function is shown up to the middle rotation range of the differential rotation where the fluid chamber pressure becomes a predetermined pressure.
When the fluid chamber pressure exceeds a predetermined pressure, it exhibits a viscous coupling-like characteristic in which the increase rate of the differential limiting torque is suppressed.

Therefore, when the differential rotation is low, the differential limiting torque has a small characteristic to prevent understeer in the initial stage of turning, and when the differential rotation is in the medium rotation, the differential limiting torque is high such as improvement in running performance on a split μ road. In order to obtain the differential limiting effect, the increase rate of the differential limiting torque has a large characteristic, and in the high differential rotation speed range, the torque transmission to the outer wheel side is prevented from increasing to the extent that the tire loses side force even when the accelerator is turned on. Therefore, the optimum differential limiting torque characteristic can be obtained regardless of the magnitude of the differential rotation, such that the rate of increase of the differential limiting torque is small.

(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. The differential means 1 is a device combined in a built-in state, and the differential means 1 includes a pinion 12 rotatably supported via a pinion shaft 11 in a differential case 10 connected to a drive input side, and the pinion 12. A pair of side gears 13,1 meshing
4 and two output shafts 15,1 connected to the side gears 13,14
It has 6 and.

Then, the driving force is directly transmitted from the side gear 13 to one of the output shafts 15 and 16, and the other output shaft 15 is transmitted.
From 16 to the side gear 14 to rotation difference sensitive differential limiting means 2
The driving force is transmitted via.

The rotation-sensitive differential limiting means 2 is a differential case that rotates relative to each other, as shown in FIGS. 1 to 3.
Of the 10 and side gears 14, the cam surface 31 formed on the inner surface of the case cover 30 of one of the differential cases 10
And six driving pistons 50 (cam bodies) that are provided on the gear base 40 of the other side gear 14 and are radially arranged to reciprocally move while making circumferential contact with the cam surface 31 by relative rotation.
And six cylinder chambers 60 (fluid chambers) whose volumes change with the reciprocating movement of the driving piston 50, balance oil passages 70 (fluid passages) communicating with the cylinder chambers 60, and the balance oil passages 70 It is provided at the end, and when the internal pressure of the cylinder chamber 60 is below a predetermined pressure, the flow path to the accumulator chamber 90 is throttled, and when it exceeds the predetermined pressure, the flow path to the accumulator chamber 90 is opened according to the internal pressure of the cylinder chamber 60. Orifice
72, an accumulator chamber 90 formed in the central portion of the regulator oil passage 80, and a relief valve 100 for discharging hydraulic oil (fluid) from the accumulator chamber 90 to the outside.

The case cover 30 is integrally provided with the differential case 10, which is a drive input member, by bolting.

The gear base 40 is disposed in the cam surface 31 of the case cover 30 in an inserted state, forms the side gear 14, and is spaced at equal intervals in the radial direction at a position facing the cam surface 31. A cylinder hole 42 is formed at the position.

The driving piston 50 is a cam member provided in an oil-tight state by a seal ring 51 with respect to the cylinder hole 42, and a circumferential contact surface with the cam surface 31 is formed by a spherical surface 50a to ensure smooth contact movement. ing. The radius of curvature of the spherical surface 50a is smaller than the radius of curvature of the cam surface 31, but larger than the radius of curvature of a ball whose diameter is approximately the inner diameter of the cylinder hole 42 (for example, called a driving ball), and a high Hertzian contact stress. Is set to.

The cinder chamber 60 is formed between the cylinder hole 42 and the driving piston 50.

The balance oil passage 70 is an oil passage that is formed in the gear base 40 and connects the cylinder chambers 60, 60 facing each other in the same phase in the reciprocating stroke of the driving piston 50, and the balance oil passages 70, 70, 70 Branch in the axial direction (axial direction) from
Further, the axial oil passage 71 guided to the accumulator chamber 90.
Is provided with a variable orifice 72.

The variable orifice 72 is attached to the gear base by a bolt 74.
It is composed of an orifice plate 73 (FIG. 2) attached to the 40 and a retainer plate 102 which will be described later. When the internal pressure of the cylinder chamber 60 is equal to or lower than a predetermined pressure, the flow path to the accumulator chamber 90 is provided to the retainer plate 102.
Orifice groove of orifice plate 73 pressed by
The retainer plate 102 is flexed and deformed in accordance with the internal pressure of the cylinder chamber 60 when it is throttled by 73a and exceeds a predetermined pressure, and the orifice flow passage expansion due to this deformation is added to open the flow passage toward the accumulator chamber 90.

As shown in FIG. 3, the regulator oil passage 80 is an oil passage that connects the cylinder chambers 60, 60, 60, 60, 60, 60 and the accumulator chamber 90 to each other. 6 radial oil passages 81 communicating with 60 (radial direction), ...,
, 81 and one axial center oil passage 82 that joins the respective radiant oil passages 81, ..., 81 at the axial center position, and each radiant oil passage 81 ,.
From the accumulator room 90 to each cylinder room 60,…,
A one-way valve 83, ..., 83 having a ball valve structure that allows only the flow of hydraulic oil to 60 is provided.

The accumulator chamber 90 is a chamber for temporarily increasing and decreasing the amount of oil by temporarily storing and releasing hydraulic oil, and an accumulator piston 91 provided in a gear base portion 40 in an oil-tight state so that it can reciprocate, and the piston 91 and a spring. The spring 93 is interposed between the retainer 92 and the retainer 92.

The accumulator piston 91 has a valve hole 101 formed on the central axis of the accumulator piston 91 and a protruding portion 102a of the retainer plate 102.
The relief valve 100 is formed to open when is moved to the right in the drawing, and the hydraulic oil is released to the outside when the accumulator chamber 90 exceeds the set 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 30 and the rotor 40, the driving piston 50
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 when there is no difference in rotational speed between the left and right wheels, when the vehicle travels straight on a highway at high speed, the output shaft
A centrifugal force acts on the driving piston 50 provided on the gear base 40 that rotates at high speed with the rotation of 15, 16 and the driving piston 50 is pressed against the cam surface 31 by this centrifugal force, and the differential limiting torque is increased. Occurs.

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 is also generated between 30 and the gear base 40, and due to this relative rotation, the driving piston 50 circumferentially contacting the cam surface 31 reciprocates in the radial direction. When attempting to reduce the volume of the
The internal pressure rises, and the hydraulic pressure obtained by multiplying the generated hydraulic pressure and the pressure receiving area of the piston 50 becomes the force that presses the driving piston 50 against the cam surface 31, and this pressing force acts as the differential limiting torque, and the driving force is distributed. The differential is limited so that the high speed rotation side is reduced and the low speed rotation side is increased.

The differential limiting torque characteristic of the embodiment device is such that when the internal pressure of the cylinder chamber 60 is equal to or lower than a predetermined pressure, the flow path toward the accumulator chamber 90 is narrowed, and when the internal pressure of the cylinder chamber 60 exceeds the predetermined pressure, the accumulator chamber 90 corresponds to the internal pressure of the cylinder chamber 60. Since the variable orifice 72 that opens the flow path toward is used, as shown by the chain double-dashed line characteristic A ′ in FIG. 4, up to the middle rotation range of the differential rotation where the internal pressure of the cylinder chamber 60 becomes a predetermined pressure, It shows a cam coupling characteristic expressed by a quadratic function with a constant orifice opening, and when the internal pressure of the cylinder chamber 60 exceeds a predetermined pressure,
It exhibits a viscous coupling-like characteristic in which the increasing rate of the differential limiting torque is suppressed by the gradually opening orifice opening, and the differential limiting torque characteristic is a combination of both characteristics.

Therefore, in the low differential rotation range, the differential limiting torque has a small characteristic in order to prevent understeer in the initial stage of turning.

Further, in the middle rotation speed range of the differential rotation, the rate of increase of the differential limiting torque, which is highly effective for improving running performance on the split μ road, suppressing tack-in, braking during turning, and the like, becomes a large characteristic.

Furthermore, in the high differential rotation range, even when the accelerator is turned on, the snow-covered road (μ = 0.3) or wet road surface (μ = 0.4).
In 5), etc., the rate of increase of the differential limiting torque is small in order to prevent the increase in torque transmission to the outer wheel side that causes the tire to lose side force.

As described above, in the rotation difference-sensitive differential limiting device of the embodiment, the orifice opening is constant until the internal pressure of the cylinder chamber 60 reaches a predetermined pressure, and when the internal pressure of the cylinder chamber 60 exceeds the predetermined pressure, the internal pressure increases in accordance with the internal pressure. Variable orifice 72 with large orifice opening
The effect of being able to obtain the optimum differential limiting torque characteristics regardless of the magnitude of the differential rotation, especially the optimum characteristics that do not lead to a vehicle spin even during an accelerated turn for an ordinary driver, is obtained. .

In addition, the differential limiting torque characteristics are adapted by adjusting the orifice groove 73a, the thickness of the retainer plate 102, the shape of the retainer plate 102 (preloading by making it somewhat umbrella-shaped, etc.). It is possible to easily match the required characteristics of the 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, in the embodiment, one balance oil passage is provided,
Although an example in which a variable orifice was made by combining an orifice plate and a retainer plate was shown, a balanced oil passage was branched in parallel, one oil passage was provided with a fixed orifice, and the other oil passage was closed to a specified pressure. The variable orifice may be configured by providing a valve that expands the flow passage cross-sectional area according to the internal hydraulic pressure when the pressure exceeds a predetermined pressure.

Further, in the present embodiment, the differential limiting means is provided between the differential case and one side gear,
The present invention can be applied to a rotation-sensitive differential limiting device having a configuration in which differential limiting means is provided between one side gear and the other side gear as in the second embodiment of Japanese Patent Application No. 62-184485. Of course there is.

(Effects of the Invention) As described above, in the rotation difference sensitive differential limiting device of the present invention, the differential control means that exhibits the differential limiting function is the differential case and the relative position of the 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 circumferentially contacting the cam surface by relative rotation, and the cam body Is provided at the end of the fluid passage that communicates with each fluid chamber and the plurality of fluid chambers that change in volume with the reciprocating movement of the fluid chamber. Since it has a variable orifice that opens the flow path toward the accumulator chamber according to the fluid chamber pressure, the optimum differential limiting torque characteristic can be obtained regardless of the magnitude of the differential rotation. Is profitable To be

[Brief description of drawings]

FIG. 1 is a vertical sectional side view taken along the line I--I of FIG. 3 showing a rotation difference sensitive type differential limiting device according to an embodiment of the present invention, FIG. 2 is a view showing an orifice plate, and FIG. FIG. 4 is a vertical sectional front view of the rotation difference sensitive differential limiting device by the II line, and FIG. 4 is a differential limiting torque characteristic diagram. 1 …… Differential means 2 …… Differential limiting means 10 …… Differential case 11 …… Pinion shaft 12 …… Pinion 13,14 …… Side gear 15,16 …… Output shaft 30 …… Case cover 31 …… Cam surface 40 …… Gear base 50 …… Driving piston (cam body) 60 …… Cylinder chamber 70 …… Balance oil passage (fluid passage) 72 …… Variable orifice 73 …… Orifice plate 80 …… Regulator oil passage 90 …… Accumulator chamber 100 …… Relief valve 102 …… Retainer plate

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. Among these, in the rotation difference sensitive differential limiting device in which the driving force is transmitted to the one output shaft from the side gear through the differential limiting means, the differential limiting means is one of the differential case and the pair of side gears. A cam surface formed on the inner surface of one of the two members that rotate relative to each other, and a cam body that is provided on the other member and that radially reciprocates while making circumferential contact with the cam surface by relative rotation, and the cam. A plurality of fluid chambers whose volumes change with the reciprocating movement of the body, and an accumulator provided at the end of the fluid passage that communicates with each fluid chamber. A rotation-difference-sensitive differential limiting device characterized in that it is provided with a variable orifice that restricts a flow path toward the chamber and opens a flow path toward the accumulator chamber according to the fluid chamber pressure when the pressure exceeds a predetermined pressure.