JPH078613B2 - Vehicle rear wheel drive - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a rear-wheel drive system that changes the drive torque of left and right rear wheels in a vehicle to make a turning travel, and more specifically,
The present invention relates to a device that is capable of turning when turning.

[Prior art]

Generally, in vehicles that drive the rear wheels, such as front engine / rear drive (FR) vehicles and four-wheel drive (4WD) vehicles, in general, from the transmission output side to the left and right rear wheel drive shafts via a differential device. Composed of transmission. Therefore, the vehicle can drive in a smooth turning motion because the left and right driving torques are always equal and the difference in rotation between the inner and outer wheels during turning is absorbed. Also, by adding a differential limiting device to the differential device, the left and right wheel driving forces become unequal based on the left and right wheel rotational speed difference, and the kinetic performance of the vehicle is different from that of a vehicle without the differential limiting device. Some have been done.

[Problems to be Solved by the Invention]

By the way, in the above-described conventional technique, the rotational difference between the inner and outer wheels is absorbed when the vehicle turns, but the driving torques of the inner and outer wheels are always equal, so that the turning performance cannot be improved. In addition, in the case where the differential limiting device is added, the difference in driving force between the left and right wheels occurs for the first time after a difference in rotational speed between the left and right wheels, such as in turning, which causes a difference in motion performance. This movement performance is not always desirable, since it occurs passively. Therefore, it is an object of the present invention to provide a rear-wheel drive system for a vehicle that can improve the turning performance as well as being capable of smoothly turning while absorbing the difference in rotation between the inner and outer wheels.

[Means for solving problems]

To this end, the present invention is configured such that the final reduction gear is transmitted to the left and right rear wheel drive shafts via the left and right hydraulic clutches with variable transfer torque capacities, respectively, and is controlled by the factors of vehicle speed, turning amount and direction, and input torque. , The hydraulic circuit is configured to set the transmission torque capacity of the left and right hydraulic clutches separately, and the left and right hydraulic clutches are arranged so that the driving torque of the outer wheels becomes larger than that of the inner wheels in the middle and low speed range during vehicle turning. Is configured to control the torque.

[Action]

Based on the above configuration, the driving torque of the outer wheels is larger than that of the inner wheels of the left and right rear wheels in the middle and low speed range during turning of the vehicle, so that the hydraulic clutch on the inner wheel side absorbs the rotation difference to enable turning.
Further, a yawing moment in the same direction as the cornering force received by the front wheels is generated around the center of gravity of the vehicle to promote the turning ability. In this way, according to the present invention, the left and right rear wheels can also turn when turning in the middle and low speed ranges, and the turning performance can be improved.

【Example】

An embodiment of the present invention will be specifically described below with reference to the drawings. In FIG. 1, reference numeral 1 is a pinion shaft to which power from a transmission device is transmitted via a propeller shaft (not shown) in an FR vehicle, which is rotatably supported by a gear case 2 and has a pinion 11 at an end portion thereof. It is facing within 2. A rear wheel drive shaft 3 oriented in the vehicle left-right direction is rotatably supported in the gear case 2, and a final gear 30 is constituted by a crown gear 31 assembled integrally with the rear wheel drive shaft 3 meshing with the pinion 11. . And the left and right end portions projecting from the gear case 2 of the rear wheel drive shaft 3, the left drive shaft through the left hydraulic clutch 4 _L 5
_L and the right drive shaft 5 _R are connected to each other via a right hydraulic clutch 4 _R so that the rear wheels 8 _L , 8 _R (see FIG. 3,
(See FIG. 4) are separately driven. Here, the hydraulic clutches 4 _L and 4 _R have variable transmission torque capacities according to the hydraulic pressure, and include a hydraulic circuit 7 controlled by a signal of a control system 6 described later. Therefore, the configuration of the hydraulic circuit 7 will be described by taking the one hydraulic clutch 4 _L side as a representative. This is because the oil pump 71, the pressure regulating valve 72, the clutch hydraulic control valve 73,
It has a duty solenoid valve 74 and the hydraulic clutch 4 _L
An oil passage 75 connects to an oil pump 71 via a clutch hydraulic pressure control valve 73. The clutch hydraulic control valve 73 has an oil pump 71 in the valve body.
And port 73a leading to the side, and the port 73b leading to the hydraulic clutch 4 _L side, a spool valve and a drain port 73c. Then, the spool 73d balances with the added pressure of the oil pressure on the port 73b side and the signal oil pressure in the signal oil pressure chamber 73f against the biasing force of the spring 73e, thereby closing both the port 73a and the drain port 73c and closing the clutch. While keeping the oil pressure constant, the drain port 73c is opened to decrease the clutch oil pressure when the signal oil pressure rises, and the port 73a is opened to increase the clutch oil pressure when the signal oil pressure falls. Further, the pressure regulating valve 72 is a port that communicates with the oil pump 71 through an oil passage 75 in a valve body that has a hydraulic chamber 72a that communicates with the signal hydraulic chamber 73f of the clutch hydraulic pressure control valve 73 through an oil passage 76.
72b, a port 72c communicating with the oil passage 76, and a drain port 72
The spool 72e is equipped with d and the spool 72e balances with the hydraulic pressure in the hydraulic chamber 72a against the biasing force of the spring 72f, thereby closing the ports 72b and 72d and increasing the pressure in the hydraulic chamber 72a. The drain port 72d is opened, and the port 72b is opened when the pressure drops, so that a constant hydraulic pressure is always taken out to the port 72c, that is, the oil passage 76. It is the duty solenoid valve 74 _L that generates the signal oil pressure in the signal oil pressure chamber 73 f of the clutch oil pressure control valve 73 to which such a constant oil pressure is supplied via the oil passage 76, depending on the duty signal described later. The hydraulic pressure in the signal hydraulic pressure chamber 73f is discharged. The hydraulic circuit is similarly configured on the hydraulic clutch 4 _R side, and the clutch hydraulic pressure is controlled by the duty solenoid valve 74 _R. Here, the control system 6 that generates a duty signal as a control signal will be described. A vehicle speed sensor 61 that detects a vehicle speed,
A steering angle sensor 62 for detecting turning and its direction, an input torque sensor 60 for detecting input torque from the transmission output side to the rear wheels, and a control unit 63 for generating a predetermined duty signal using these sensor outputs as input signals. Be equipped with. The control unit 63 includes a vehicle speed discriminating unit 64 that discriminates the vehicle speed according to the output of the vehicle speed sensor 61 and a turning amount that discriminates the amount of straight traveling, right turning, or left turning of the vehicle according to the output of the steering angle sensor 62. And a direction determination unit 65, a torque distribution ratio calculation unit 66 that determines the torque distribution ratio to the left and right hydraulic clutches 4 _L and 4 _R according to the outputs of both the determination units 64 and 65, and the torque distribution ratio calculation unit 66. Of the clutch hydraulic pressure to the left and right hydraulic clutches 4 _L and 4 _R based on the output of the input torque sensor 60 and the output of the clutch torque calculation unit 67, and the duty ratio according to the output of the clutch hydraulic pressure calculation unit 67. Two duty ratio setting sections 68 _L and 68 _{R for} setting are provided. Then, the torque distribution ratio calculation unit 66 controls the left and right hydraulic clutches when the vehicle is traveling straight.
The torque distribution ratio to the rear wheels 8 _L and 8 _R via 4 _L and 4 _R is the same, and when the vehicle turns in the medium to low speed range, the torque distribution on the outer wheel side is larger than that on the inner wheel inside the turn, and conversely. When turning in the high speed range, the torque distribution on the inner wheel side is set to be larger than that on the outer wheel side. Also, the left and right hydraulic clutches 4 _L , 4 in the clutch hydraulic pressure calculation unit 67
Explaining the hydraulic pressure calculation of _R , the input torque T _O is the fifth
As shown in FIG. 5A, it changes depending on the relationship between the shift position and the engine suction pipe negative pressure, and the transmission torque capacity and hydraulic pressure of the hydraulic clutch are increasing functions as shown in FIG. 5B. Therefore, the left and right torque distribution ratios T _L and T _R in the torque distribution ratio calculation unit 66 are T _L = T _R
In the case of straight running, the left and right clutch hydraulic pressures P _L and P _R are both set to the maximum, the transmission torque capacities C _L and C _R are also set to the maximum, and the left and right rear wheels are split into two without slipping at any input torque. Communicate to. On the other hand, if the allocation state of the T _L> T _R, the T _L side defined maximum torque transfer capacity C _L with the clutch oil pressure P _L, a _{T L / (T L + T} R) of the input torque T _O Transmit without slipping. On the other hand, on the T _R side, the transmission torque capacity C _R is calculated by the following equation from the input torque T _O and T _L , T _{R at} this time. _{C R = T O × {T} R / (T L + T R)} Then, the clutch oil pressure P _R in accordance with the transmission torque capacity C _R
Determine. Then, the drive torque is reduced so that the input torque T _O is transmitted by T _R / (T _L + T _R ), and slippage is allowed. In the above configuration, the control system 6 controls the driving torques of the left and right rear wheels 8 _L , 8 _R separately according to the vehicle speed and the traveling state of turning. In the straight traveling state of the vehicle, the torque distribution ratio to the left and right hydraulic clutches 4 _L and 4 _R by the torque distribution ratio calculation unit 66 is the same,
The left and right hydraulic clutches 4 _L , 4 _R are controlled to have the same hydraulic pressure, and the left and right rear wheels 8 _L , 8 _R are driven with the same torque. When the vehicle turns in the medium to low speed range, the torque distribution ratio in the torque distribution ratio calculation unit 66 is determined to be larger on the outer wheel side than on the inner wheel. Based on this, for example, in a left turn in the medium to low speed range, the duty signal corresponding to the left hydraulic clutch 4 _L has a small duty ratio, the signal hydraulic pressure by the duty solenoid valve 74 _L is set large, and the clutch hydraulic pressure becomes small. At the same time, the duty ratio of the duty signal corresponding to the right hydraulic clutch 4 _R becomes large, the signal hydraulic pressure by the duty solenoid valve 74 _R is set small, and the clutch hydraulic pressure becomes large. That is, the left and right hydraulic clutches 4 _L , 4
Depending on the torque distribution ratio, _R is controlled so that the left side is small and the right side is large. Therefore, the right rear wheel 8 _R is driven with a sufficient transmission torque, and the left rear wheel 8 _L is driven with a smaller transmission torque than the right side.
And this means that the left hydraulic clutch 4 _L permits a predetermined slip, the left rear wheel 8 _L absorbs the rotational difference between the inner and outer rings are slightly low speed than the right rear wheel 8 _R, smooth Enables smooth turning. Especially, the driving torque of the left rear wheel 8 _L inside the turn is small,
Since the driving torque of the turning outer rear right wheel 8 _R is large, the vehicle produces a yawing moment of the left in the vehicle center of gravity G around based on the difference between the driving torque of the inner and outer rings (see FIG. 3). This is in the same direction as the yawing moment around the center of gravity G of the vehicle based on the cornering force received by the front wheels 9 _L , _R , so that the turning performance is improved. In the case of turning to the right, the same action works symmetrically. Next, when the vehicle turns in the high speed range, the torque distribution ratio in the torque distribution ratio calculation unit 66 is determined to be larger on the inner wheel side than on the outer wheel, which is opposite to the case in the medium to low speed range. Therefore, in this case, contrary to the above, the left rear wheel 8 _L is driven with a sufficient transmission torque, and the right rear wheel 8 _R is driven with a transmission torque smaller than the left side. And in turning in the high speed range, large drive torque of the left rear wheel 8 _L of the turning inner, since the driving torque of the right rear wheel 8 _R of the turning outer small, based on the difference between the driving torque of the inner and outer rings vehicle Generates a rightward yawing moment around the center of gravity G (see FIG. 4). This is in the opposite direction to the yawing moment around the center of gravity G of the vehicle due to the cornering force received by the front wheels 9 _L , 9 _R , and acts in a direction to cancel this out a little, so that the stability of turning traveling is improved. In the case of turning right, exactly the same operation is performed. Although the present invention has been described by taking the FR vehicle as an example, the present invention is a 4WD vehicle,
It can be applied to anything that drives the rear wheels, such as a rear engine / rear drive vehicle.

【The invention's effect】

As described above, according to the present invention, slippage is allowed in the inner-side hydraulic clutches of the left and right rear wheels in the middle and low speed ranges when the vehicle is turning, so that a large rotation difference between the inner and outer wheels is reliably absorbed, It is possible to make a good turn. Further, in this case, the torque distribution of the left and right rear wheels causes a yawing moment in the same direction as the yawing moment due to the cornering force of the front wheels around the center of gravity of the vehicle to promote the turning performance, so that the turning performance is improved. With this improved turning performance, the steering force is reduced and the steering wheel is cut more easily. Since such turning performance can be obtained by adding a hydraulic clutch without the need for a differential device or a rear wheel steering device, the structure is simplified.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram of a control system, FIG. 3 is an explanatory view of the action when the vehicle runs in a medium or low speed turn, and FIG. 4 is a high speed turn of the vehicle. Fig. 5 (a) is a diagram showing an input torque characteristic, and Fig. 5 (b) is a diagram showing a clutch characteristic. 4 _L …… Left hydraulic clutch, 4 _R …… Right hydraulic clutch, 5 _L
...... Left drive shaft, 5 _R …… Right drive shaft, 7 …… Hydraulic circuit,
30 …… Final reduction gear, 60 …… Input torque sensor, 61 …… Vehicle speed sensor, 62 …… Steering angle sensor, 63 …… Control unit, 66…
… Torque distribution ratio calculator, 67 …… Clutch oil pressure calculator.

Claims (1)

[Claims] Claim: What is claimed is: 1. A final drive unit is configured to transmit power to the left and right rear wheel drive shafts via left and right hydraulic clutches with variable transmission torque capacities. The hydraulic circuit is configured to set the clutch transmission torque capacity separately, and the left and right hydraulic clutches are torque-controlled so that the driving torque of the outer wheel is larger than that of the inner wheel in the middle and low speed range when the vehicle is turning. Rear wheel drive for vehicles.