JP2014001841A - Limited slip differential device with variable cam angle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a limited slip differential device which has a performance for reducing effects of a differential limitation in low-speed traveling and for rapidly improving the effects of the differential limitation in accordance with increase of engine output.SOLUTION: In the limited slip differential device, a pinion shaft spreads out a cam hole of a pressure ring, thereby generating the effects of the differential limitation, and characteristics of the limited slip differential device are determined by a cam angle of the cam hole. A mechanical spring or spring having a force in a direction opposite to a rotating direction of the pinion shaft is utilized to accomplish a cam angle varying mechanism for the cam hole of the pressure ring. When the force of the mechanical spring or the spring is stronger than a rotational force of the pinion shaft, the cam angle becomes smaller and the effects are reduced. When the rotational force of the pinion shaft becomes stronger than the force of the mechanical spring or the spring, the cam angle becomes larger.

Description

The present invention relates to a limited slip differential device that limits a differential mechanism that distributes a single power to two drive wheels.

Many of today's automobiles distribute the driving force generated by a single engine to two front or rear tires. When the automobile travels on a straight line, it is only necessary to distribute an equal driving force to the left and right tires. However, when the car turns a curve, the circle drawn by the inner tire and the circle drawn by the outer tire are different, so if you distribute the engine driving force equally to the left and right tires, I can't turn.

In general, a differential device having a differential gear as a principle for rotating (differential) the inner tire and the outer tire at different speeds is provided. A differential device exists on the front wheel shaft in the front wheel drive vehicle and on the rear wheel shaft in the rear wheel drive vehicle. In a four-wheel drive vehicle, not only the front and rear differential devices are provided, but also the center differential device that absorbs the front and rear rotational difference may be provided.

There are two problems with a differential device that makes a car running smoothly. If one of the tires on the drive shaft falls into a groove or climbs onto ice and becomes unloaded or nearly unloaded, the differential device increases the driving force of the engine to the tire on the lighter load side. Because of the transmission, the driving force cannot be transmitted to the tire that is in contact with the other ground. In other words, the presence of the differential device makes it impossible for the automobile to move forward if one of the tires is idle due to wheel removal, on ice, or muddyness. This is the first problem.

Another problem is when a sports car equipped with a differential device or a motor sports car turns a curve. When a sports car or a motor sports car turns a curve at a high speed, the vehicle body tilts outward due to centrifugal force, the inner tire floats, and the ground load (resistance) decreases. The inner tire is in the same state as the previous wheel-removed state, and the engine driving force is transmitted more by the differential device. Therefore, the inner tire is supposed to transmit more driving force than the inner tire. Cannot be provided with sufficient driving force. That is, due to the presence of the differential device, sports cars and motor sports cars lose temporary propulsion during cornering. This is the second problem.

In order to solve the above two problems, a limited slip differential device (hereinafter referred to as “LSD”) incorporating a mechanism for limiting the differential function of the differential device is known. There are LSDs of various principles. Here, the principles and effects of an LSD called a general mechanical type as a prior art will be described with reference to FIGS.

FIG. 1 depicts a rear-wheel drive vehicle with LSD that is about to start on a slippery road surface with only the left rear wheel. The driving force of the engine is transmitted to the LSD by the propeller shaft. The final pinion gear attached to the propeller shaft meshes with the ring gear attached to the differential case of the LSD, and rotates the LSD main body.

In a normal differential device, the car cannot start because only the left rear wheel rotates. However, in the case of LSD, the pressure plate fixed to the side shaft and the pressure plate fixed to the differential case generate frictional force due to surface contact via the gear oil, and the side shaft that drives the left rear wheel Limit operation. This frictional force is called initial torque. The initial torque is generated by a frictional force obtained by pressing the two types of pressure plates in advance with a cone plate (slab spring) or a spring. Based on the above principle, even if the vehicle with LSD rides on a slippery road surface, the differential function of the differential device is limited, so the vehicle can start slowly. This is the solution to the first problem by LSD.

FIG. 2 depicts a rear-wheel drive sports car or motorsport car with LSD that is about to turn to the right at high speed. The higher the speed or the smaller the turning radius of the turn, the greater the centrifugal force acting outward from the center of the circle, and the right rear wheel, which is the driving wheel, floats. The driving force of will escape. The LSD has the above-described initial torque, but the driving force from the engine is higher than the initial torque during high-speed turning, and the idle rotation of the right rear wheel cannot be suppressed.

However, the LSD can limit the differential function of the differential device in proportion to the engine driving force applied to the LSD. A cam hole is provided in the pressure ring of the LSD, and the pinion shaft tries to expand the cam hole of the pressure ring by a driving force transmitted from the engine. When the cam hole is expanded, the frictional force between the two types of pressure plates between the pressure ring and the differential case can be increased. In other words, the LSD limits the differential function of the differential device by increasing the frictional force between the two types of pressure plates in proportion to the increase in engine driving force applied to the LSD.

Based on the above principle, an automobile with LSD can pass without stalling when attempting to turn a curve at high speed while maintaining a high engine driving force. This is the solution to the second problem by LSD.

Problems to be solved by the invention

FIG. 3 shows the cam hole structure of the LSD. A pinion shaft having a round cross section is sandwiched between diamond-shaped cam holes. The direction of the force that the pinion shaft applies to the pressure ring differs by 180 degrees when accelerating by opening the throttle of the engine and when applying the engine brake. In other words, in general LSD, the differential function is limited both during acceleration and during engine braking.

A car entering a curve uses foot brakes and engine brakes. At this time, the LSD restricts the operation of the differential gear and tries to match the rotational speeds of the left and right tires. For this reason, a method has been proposed in which the cam angle when accelerating by opening the throttle of the engine and the cam angle during engine braking are changed (Patent Publication 2007-315555). The wider the cam angle, the easier the pinion shaft will spread the pressure ring and the better the LSD will be. LSD with the same cam angle on the acceleration side and the engine brake side is 2 Way, LSD with a narrow cam angle on the engine brake side compared to the acceleration side is 1.5 Way, the cam angle on the engine brake side is zero, and the LSD function is available only during acceleration The operating LSD is called 1 Way.

FIG. 4 shows the characteristics of LSD. The horizontal axis represents the driving torque by the engine output applied to the LSD, and the vertical axis represents the differential function limiting rate (lock rate), which is the effect of LSD. 100% on the vertical axis represents a state where there is no differential device, that is, a differential lock state. If the LSD is too effective during low-speed driving, it becomes difficult to handle in daily driving such as turning at an intersection. Ideally, the minimum initial torque should be secured, a wide cam angle should be provided, and the effectiveness of the LSD should increase as the drive torque increases. On the other hand, when the cam angle is large, the LSD starts to be effective even at low speed running frequently used in daily running. On the other hand, if the cam angle is narrowed, the effectiveness of LSD during low-speed traveling can be suppressed, but sufficient LSD effectiveness during high-speed traveling cannot be obtained.

In order to satisfy the LSD performance requirement at the time of low speed driving and high speed driving, it is necessary to satisfy the characteristic 37 shown in FIG. However, LSD having this characteristic has not been realized. In the present invention, the structure and principle of LSD that realizes this characteristic will be described.

Patent Publication 2007-315555

Means for solving the problem

It has already been described that the limiting ratio of the differential function which is the effect of LSD can be set by the cam angle of the pressure ring. In order to realize the LSD having the characteristic 37 in FIG. 4, it is necessary to realize a structure in which the cam angle increases at a low speed as the cam angle decreases and the engine output increases.

In the present invention, a cam angle variable mechanism is realized using a spring or a spring having a force in a direction opposite to the direction in which the pinion shaft pushes and widens the cam hole. If the spring or spring force is stronger than the rotational force of the pinion shaft, the cam angle becomes smaller. On the other hand, when the rotational force of the pinion shaft increases in proportion to the engine output, the cam angle can be widened by pushing down the spring or the force of the spring.

Effect of the invention

According to the LSD of the present invention, the LSD performance can be fully exploited during high-speed traveling with a large engine output without feeling any disadvantages of LSD during low-speed traveling.

The present invention relates to a limited slip differential device that limits a differential mechanism that distributes a single power to two drive wheels.

It is a figure which shows the principle and effect of the motor vehicle provided with the conventional LSD (slippery road surface). It is a figure which shows the principle and effect of the motor vehicle provided with the conventional LSD (at the time of high-speed turning). It is explanatory drawing which shows the cam hole structure and operation | movement of the conventional LSD. It is explanatory drawing which shows the characteristic view of LSD. It is explanatory drawing which shows LSD of Example 1 by this invention. It is explanatory drawing which shows LSD of Example 2 by this invention.

DESCRIPTION OF SYMBOLS 1 Rear-wheel drive car 2 Left front wheel 3 Right front wheel 4 Engine 5 Propeller shaft 6 Left side shaft 7 Right side shaft 8 Left rear wheel 9 Right rear wheel 10 Limited slip differential device 11 Slippery road surface 12 Right rear with reduced ground load Wheel 13 Final pinion gear 14 Pressure ring 15a Pressure plate 15b fixed to the differential case Pressure plate 16 fixed to the side shaft Cone plate (Sarabane)
17 Left Side Gear 18 Right Side Gear 19 Pinion Shaft 20 Pinion Gear 21 Cam Hole 22 Differential Case 23 Ring Gear 24 Pinion Shaft Movement During Acceleration 25 Pinion Shaft Movement During Deceleration 26 Force Pushing Pressure Plate 27 Acceleration Side Cam Angle 28 Deceleration Side Cam angle 29 1.5 Way type cam hole 30 1 Way type cam hole 31 Differential function limiting rate (lock rate)
32 Drive torque 33 Low-speed driving area (area with mesh line)
34 100%
35 Characteristics of differential lock 36 Characteristics of large cam angle 37 Characteristics of small cam angle 38 Initial torque 39 Characteristics of the present invention 40 Operation at low speed with low engine output 41 Operation at high engine output 42 Operation at low speed 43 Leaf spring 44 Leaf spring holding groove 45 Spring 46 Variable cam

A first embodiment of the present invention will be described. FIG. 5 shows the operation of the cam hole using the leaf spring according to the present invention. The cam hole shows the case of 1 Way. The cam angle on the acceleration side is large, and a leaf spring is installed in front of it. During acceleration, the pinion shaft pushes the leaf spring open. At low speed, the leaf spring opens slightly, which is equivalent to a small cam angle. Further, when the engine output is increased and the force by which the pinion shaft pushes the leaf spring exceeds the force of the leaf spring, the leaf spring is pressed against the original cam hole, so the cam angle becomes large. As described above, according to the present invention, a variable cam angle can be realized simply by adding a leaf spring to the pressure ring, and there is no disadvantage of LSD at low speed, and LSD capable of obtaining high-speed cornering performance can be realized. .

In the LSD of the first embodiment, the characteristics of the LSD can be adjusted by the strength of the leaf spring. If it is a soft leaf spring, the point at which the cam angle changes can be set to the low speed side. On the contrary, if it is a hard spring, the point where the cam angle changes can be set to the high speed side.

The first embodiment of the present invention has been described above by taking the case of a 1-Way LSD as an example, but a 1.5-Way or 2-Way LSD can also be realized.

A second embodiment of the present invention will be described. FIG. 6 shows the operation of a variable cam hole operated by a spring according to the present invention. The variable cam has a structure that moves around a fulcrum fixed to the pressure ring, and includes a spring. The cam hole shows the case of 1 Way. The cam angle on the acceleration side is large, and a variable cam is installed in front of it. During acceleration, the pinion shaft opens the variable cam. At low speed, the variable cam opens slightly, which is equivalent to a small cam angle. Further, when the engine output is increased and the pinion shaft exceeds the force of the spring of the variable cam, the cam angle is increased because the variable cam is pressed against the original cam hole. As described above, according to the present invention, a variable cam angle can be realized, and there is no disadvantage of LSD at a low speed, and an LSD capable of obtaining a high-speed cornering performance can be realized.

In the LSD of the second embodiment, the characteristics of the LSD can be adjusted by the strength of the spring. If it is a soft spring, the point at which the variable cam angle changes can be set to the low speed side. On the contrary, if it is a hard spring, the point where the variable cam angle changes can be set to the high speed side.

As described above, the second embodiment of the present invention has been described by taking the case of a 1-way LSD as an example, but a 1.5-way or 2-way LSD can also be realized.

Claims (3)

In the differential case that rotates when the driving force of the engine is transmitted, the pinion gear attached to the I-shaped or cross pinion shaft and the side gear connected to the axle mesh with each other and are sandwiched between a pair of pressure rings. In the limited slip differential device having a plurality of pressure plates between the differential case and a structure in which the pinion shaft pushes the pressure ring by the rotational driving force applied to the pressure ring.
A limited slip differential device, wherein a cam angle of a cam hole in which a pinion shaft pushes a pressure ring changes depending on a magnitude of a driving force applied to the pressure ring. The limited slip differential device according to claim 1, wherein a plate spring is used for the cam angle varying mechanism. The limited slip differential device according to claim 1, wherein a variable cam hole operated by a spring is used for the variable mechanism of the cam angle.

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