JP2598322B2 - Driving force control device for four-wheel drive vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a driving force control device including a power distribution device for front and rear wheels and a differential limiting device for left and right wheels mounted on a driving system in a four-wheel drive vehicle. More specifically, the present invention relates to a device that variably controls a driving force distribution torque and a differential limiting torque according to each traveling condition or the like.

[Conventional technology]

In general, in a four-wheel drive vehicle, the torque distribution of the front and rear wheels is always fixed at a fixed ratio (for example, 50:50), such as with a center differential, whereas the torque distribution of the front and rear wheels is controlled by a hydraulic clutch or the like depending on running conditions and road surface conditions. It is conceivable to optimize by variable control. Also, in the limiting device of the differential device interposed between the left and right wheels, a differential limiting control hydraulic clutch is provided to variably control the differential limiting torque according to various conditions, thereby improving running performance and the like. It is thought that.

The variable control of the front and rear wheel torque and the left and right wheel differential limiting torque requires at least two sets of hydraulic clutches for each control, and also a hydraulic control system such as an oil pump and a valve means. Placement is important.
Here, considering the compact assembly of the hydraulic clutch, it is conceivable to dispose the hydraulic clutch inside the case of the transmission or the differential, but it is necessary to consider the following points. That is, the oil of the hypoid gear such as the final reduction gear or the deflecting gear device is generally used under the condition that the load of the gear and the slip speed are extremely large, so that the oil having good load resistance is used. Since the viscosity is so large that the viscosity remarkably changes with temperature, it is unsuitable as a working fluid for an oil pump. At low temperatures, hydraulic control by a duty solenoid valve may become impossible. In addition, hydraulic clutches under this oil condition generally have a low friction coefficient and a large temperature dependency, and are liable to generate vibration and stick-slip when relative slip is given unless an appropriate friction coefficient adjusting agent is added. It is difficult to exhibit the friction characteristics (μ-v characteristics) with respect to the sliding speed stably for a long time. For this reason, when a hydraulic clutch is incorporated in a case of a transmission or a deflecting gear device, it is necessary to partition at least the hydraulic clutch control oil passage side to use an oil different from the hypoid gear oil. In particular, in a clutch that requires fine control to give relative slip, it is preferable to use a different lubricating oil for the clutch itself from the hypoid gear oil. It is also important to arrange the hydraulic chamber of the hydraulic clutch on the fixed side instead of the general rotating drum side to prevent the effect of centrifugal hydraulic pressure and improve control accuracy.

On the other hand, in the control system of front and rear wheel torque and differential limiting torque, while maximizing the performance of the four-wheel drive vehicle,
It is desired to control so as to improve the running performance, turning performance, and the like due to the left and right wheel differential limitation.

Therefore, conventionally, there is a prior art of this type of power control, for example, in JP-A-61-155027. Here, two hydraulic clutches for driving the front wheels and for driving the rear wheels are provided in the case of the transfer device on the transmission output side, and the power distribution of the front and rear wheels is controlled by the hydraulic control of the two hydraulic clutches. It is shown. In the prior art of JP-A-62-103227, a multi-plate friction clutch is provided between a differential case and a side gear of a differential device, and the clutch is pressed by a hydraulic piston via a rod, a spacer, a bearing, and a reaction plate. To generate a differential limiting torque. It is shown that the differential limiting torque is variably controlled according to the difference between the left and right wheel rotation speeds. Japanese Patent Application Laid-Open No. 1-95939 discloses a transfer case in which an input side is connected to a transmission output shaft, and an output side is connected to a propeller shaft. It is disclosed that a clutch is provided with a differential limiting device, and a single hydraulic circuit and a control circuit control the distribution of driving force or the differential limiting force based on longitudinal or lateral acceleration.

[Problems to be solved by the invention]

However, the above-mentioned prior art does not simultaneously perform both of the torque distribution of the front and rear wheels and the differential limiting torque of the left and right wheels. In addition, since all of the prior arts are configured to share a hypoid gear oil or the like that is required to withstand heavy load as the lubricating oil of the hydraulic clutch, the oil is not suitable as a differential fluid due to a change in viscosity as described above, and is particularly fine. There is a problem such as stick-slip in a clutch that requires control to give relative slip.

Further, when a clutch for power distribution is provided in the transmission and a clutch for limiting the differential is provided in the rear wheel differential device as disclosed in Japanese Patent Application Laid-Open No. It is thought that the mountability of the machine will deteriorate,
If an attempt is made to supply hydraulic pressure to the power distribution clutch and the differential limiting hydraulic clutch from the same hydraulic power source, the oil path needs to be extended for a long time, which is not preferable in terms of control response, reliability and maintainability. It is also possible to equip each with a hydraulic source such as an oil pump, but in that case, a new problem arises in terms of an increase in cost and a securing of an arrangement space.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to compactly and independently use two sets of hydraulic clutches for front and rear wheel torque distribution and differential limiting torque by using a differential device or the like. And a proper arrangement so as not to generate centrifugal oil pressure. Further, it is possible to control the torque distribution and the differential limiting torque by each hydraulic clutch so as to improve running performance, turning performance, steering stability, starting performance, and the like.
An object of the present invention is to provide a driving force control device for a wheel drive vehicle.

[Means for Solving the Problems] In order to achieve the above object, the driving force control device of the present invention is configured to directly transmit power to one of the front and rear wheels and to transmit power to the other via a power distribution device. In wheel drive vehicles,
The power distribution device provided with the first hydraulic clutch is installed at an input portion of a front differential device or a rear differential device configured to be transmitted from an output shaft of a transmission via a propeller shaft, and the first hydraulic clutch is provided. Is connected to the drive pinion of the deflecting gear device, the ring gear of the deflecting gear device is provided on the outer periphery of the differential case of the differential device, and the differential device is provided with a differential limiting control device having a second hydraulic clutch. It is characterized in that the power distribution of the front and rear wheels is controlled by the transmission torque of the first hydraulic clutch, and the differential limitation of the left and right wheels is controlled by the transmission torque of the second hydraulic clutch.

[Action]

Based on the above configuration, the output from the transmission is always transmitted to one of the front and rear wheels, and simultaneously transmitted to the other of the front and rear wheels in accordance with the transmission torque of the first hydraulic clutch of the power distribution device. It runs with wheel drive. Then, the transmission torque of the first hydraulic clutch of the power distribution device is changed according to slip and running conditions, and by controlling the power distribution of the front and rear wheels, slip of the front and rear wheels is prevented, so that running performance, running stability and starting can be achieved. Improve the properties. Further, the differential of the differential device is limited by the second hydraulic clutch of the differential limit control device, and the differential limiting torque is variably controlled in accordance with slip or running conditions to prevent left and right wheels from slipping, and It promotes the improvement of performance and turning performance.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, the overall outline of a four-wheel drive vehicle to which the present invention is applied is, for example, a vertical transaxle type front engine / front drive (FF) -based four-wheel drive vehicle with a manual transmission. State. Reference numeral 1 denotes an engine, 2 denotes a clutch, 3 denotes a subtransmission, and 10 denotes a manual transmission, which are vertically arranged in the vehicle longitudinal direction.

The auxiliary transmission 3 is provided between the intermediate shaft 4 from the clutch 2 and the input shaft 11 to the manual transmission 10 and is configured to be switched between high and low stages. A differential device 5 is provided.

The manual transmission 10 is provided with a plurality of speed-change gears 13 and a synchronizing mechanism 14 between an input shaft 11 and an output shaft 12 so as to shift to a plurality of speeds. Through the front wheel 6. A transfer device 7 is disposed at the rear of the manual transmission 10. The transfer shaft 9 is further connected to the output shaft 12 via a transfer gear 8.

The transfer shaft 9 is connected to a propeller shaft 21 via a joint 20 and extends rearward to be connected to a rear differential device 30. The pinion shaft 22 at an input portion of the rear differential device 30 is connected to the rear drive from the propeller shaft 21. axis
25 is divided and arranged coaxially, and a power distribution device 40 is interposed between the two. Also, rear differential device
30 is provided with a differential limit control device 50, the left and right axles 23L,
23R is connected to the left and right rear wheels 24L, 24R.

As a control system, an oil pump 61 equipped with a motor 60 is mounted on the carrier 31 side of the rear differential device 30, and the oil pump 61 has a circuit configuration to a power distribution device 40 and a differential limit control device 50 via a hydraulic control device 62. The control unit 70 is configured to be electrically controlled by a duty output signal.

2 and 3, the rear differential device 30 will be described in detail.

The rear differential device 30 includes a carrier 31 in which a drive pinion 32 of a pinion shaft 22 is supported and inserted by a bearing 33, and a ring gear 36 integrated with a differential case 35 supported at both ends by bearings 34, 34 and a drive pinion 32. Mesh with. Also, inside the differential case 35, the pinion 38 of the pinion shaft 37 meshes with the left and right side gears 39L, 39R, and the side gears 39L, 39R are spline-coupled to the axles 23L, 23R, respectively. The power is transmitted to the left and right rear wheels 24L and 24R, and the rotation difference is absorbed.

In the power distribution device 40, an extension case 41 is integrally provided in front of the carrier 31, and the rear drive shaft 25 is installed inside the extension case 41 with both ends supported by bearings 42, 42. Further, an oil seal 43 is provided between the carrier 31 and the spacer 22a of the pinion shaft 22 next to the bearing 33, whereby the chamber 41a inside the extension case 41 is separated from the rear differential device 30, and is different from the hypoid gear oil. It has become possible to use lubricating oil for hydraulic clutches. The rear drive shaft 25 is disposed coaxially with the pinion shaft 22 and has an end fitted through a needle bearing 44, and a first hydraulic clutch 45 is provided between the two.

The first hydraulic clutch 45 has a drum 45 a mounted on a flange 25 a of a rear drive shaft 25, and a hub 45 mounted on the pinion shaft 22.
b is positioned by the thrust washer 46 and spline-coupled. And the flange 25a behind the drum 45a is the bearing 42
, And a plurality of plates 45c and disks 45d are alternately arranged between the drum 45a and the hub 45b. A hydraulic chamber 45e, a piston 45f, and a return spring 45g are attached to the fixed-side carrier 31 so that centrifugal oil pressure is not generated.The piston 45f presses and contacts the plate 45c via a thrust bearing 47. The clutch torque is generated.

Note that the periphery of the first hydraulic clutch 45 is
An oil passage 22b provided in the extension case 41 is filled with a predetermined amount of lubricating oil for a hydraulic clutch.The rotation of each part lubricates the plate 45c, the disk 45d, etc. Lubricating oil is supplied from the path 22b to the needle bearing 44 and the thrust washer 46.

The differential limit control device 50 includes a side case 51 integrally fitted on the axle 23R side of the carrier 31, a shaft portion 35a at one end of the differential case 35 inserted into the side case 51, and a bearing for the axle 23R. Supported by 53. An oil seal 52 is interposed between the shaft part 35a of the side case 51, the differential case 35 and the axle 23R, and a chamber 51a inside the side case 51 is formed by side gears 39L, 39R and a pinion 38 in the differential case. A second hydraulic clutch 55 is provided between the axle 23R and the shaft portion 35a of the differential case 35 separately from the dynamic gear device and the deflecting gear device including the drive pinion 32 and the ring gear 36.

In the second hydraulic clutch 55, a plurality of plates 55c and disks 55d are alternately arranged between the drum 55a of the axle 23R and the hub 55b of the differential case shaft portion 35a.
The rear of 55a is supported on the side case 51 via a thrust bearing 54. Similarly to the above, the hydraulic chamber 55e, the piston 55f, and the return spring 55g are attached to the fixed-side retainer case 51a, and the piston 55f is pressed against the plate 55c to generate a differential limiting torque.

Since the chamber 51a inside the side case 51 communicates with the chamber 41a inside the extension case 41 via a connection hole (not shown), the lubricating oil for the first hydraulic clutch 45 is supplied to the second hydraulic clutch. Since the second hydraulic clutch 55 is disposed so as to be immersed in the drum 55a, it is possible to lubricate each part of the second hydraulic clutch 55.

In FIG. 4, the hydraulic control system will be described first. The discharge pressure of the oil pump 61 driven by the motor 60 is regulated by the regulator valve 63 to generate predetermined operating oil pressure and lubricating oil pressure. The hydraulic pressure oil passage 64 communicates with the first and second hydraulic clutches 45 and 55 on the hydraulic chamber side through clutch control valves 65a and 65b and oil passages 66a and 66b. The oil passage 64 communicates with the control side of the duty solenoid valves 69a and 69b and the clutch control valves 65a and 65b through the pilot valve 67 and the oil passages 68a and 68b. The duty signal of the control unit 70 is output to the duty solenoid valves 69a and 69b to generate a duty pressure.
By operating the first and second hydraulic clutches 45, 65a and 65b,
The clutch pressure of 55 is controlled to a desired value.

Next, the electric control system of the control unit 70 will be described.

First, as input signals, a front wheel speed sensor 71, a rear wheel speed sensor 72, a rear left wheel speed sensor 73, a rear right wheel speed sensor
74, a throttle opening sensor 76, a gear position sensor 77, a steering angle sensor 78, and an acceleration sensor 79. In the power distribution control system, a rotation speed difference detection unit 80a to which the front wheel rotation speed NF of the front wheel rotation speed sensor 71 and the rear wheel rotation speed NR of the rear wheel rotation speed sensor 72 are input.
And the rotation speed difference ΔNa is calculated by ΔNa = NF−NR. If the rotation speed difference ΔNa is equal to or greater than the set value, slip is determined by the slip determination unit 81a, and the clutch pressure setting unit 8
Search the map in 2a to determine a high clutch pressure Pa. This clutch pressure Pa is corrected to be reduced by the steering angle θ of the steering angle sensor 78 to avoid tight corner braking, and the signal of the clutch pressure Pa is changed to a duty signal by the duty conversion unit 83a, and the duty signal is transmitted to the duty solenoid valve 69a. Is output. When the rotation speed difference ΔNa is equal to or smaller than the set value, the normal traveling determination section 84a determines that the vehicle is traveling normally, and the clutch pressure setting section 85a searches the map for the clutch pressure Pa in this case. Here, in a map based on the vehicle speed V of the rear wheel speed sensor 72 and the throttle opening φ of the throttle opening sensor 76, the clutch pressure Pa is controlled so that the torque transmitted to the rear wheels is equivalent to the front and rear axle load distribution. I do. Further, the gear position e of the gear position sensor 77 is corrected to increase at the lower gear, and the gear position e is corrected to decrease by the angle θ of the angle sensor 78,
The increase is corrected by the acceleration g of the acceleration sensor 79, and the optimum clutch pressure Pa is set according to each traveling condition. This clutch pressure Pa is also duty-converted and output.

The differential limiting control system also includes a rotation speed difference detection unit 80b to which the rear left wheel rotation speed NL of the left wheel rotation speed sensor 73 and the rear right wheel rotation speed NR of the rear right wheel rotation speed sensor 74 are input. ΔNb is calculated by ΔNb = NL−NR. Also in this case, similarly to the above, it has a slip determination section 81b, a normal traveling determination section 84b, clutch pressure setting sections 82b and 85b, and a duty conversion section 83b.
Then, in the case of slip and normal running, the clutch pressure Pb is set by a map search substantially similar to the above.

Next, the operation of the driving force control device for a four-wheel drive vehicle having such a configuration will be described.

First, the power of the engine 1 is input to the manual transmission 10 via the clutch 2 and the auxiliary transmission 3, and the shifted power is supplied to the output shaft 12.
From the front differential device 5 and the front wheels 6. The shifting power is input to the first hydraulic clutch 45 of the power distribution device 40 via the transfer device 7, the propeller shaft 21, and the rear drive shaft 25. Here, when the vehicle is running,
The front and rear wheel rotation speeds Nf, NR and the like are input to the control unit 70 and processed, and the flowchart of FIG. 5A is executed. Therefore, in the steady running on a dry road surface, it is determined that the vehicle is running normally on the basis of NF ク ラ ッ チ NR, and the clutch pressure Pa is continuously changed so as to have a distribution ratio corresponding to the axle load distribution of the front and rear wheels. Output to the solenoid valve 69a.

On the other hand, in the hydraulic control system, the motor 60
61 is always driven, and the operating oil pressure is controlled by the regulator valve 63 so that the duty solenoid valves 69a and 69b and the clutch control valves 65a and 65
Led to 5b. For this reason, the duty solenoid valve 69a controls the discharge pressure of the pilot pressure adjusted by the pilot valve 67 using a duty signal to change the control pressure of the clutch control valve 65a.
The operating oil pressure is led to 45e, and the above-described clutch pressure Pa is generated. Therefore, the piston 45f has a plate 45c and a disc 45d.
Is pressed in accordance with the clutch pressure to generate a clutch torque, and power corresponding to the clutch torque is input to the differential case 35 of the rear differential device 30 via the drive pinion 32 of the pinion shaft 22 and the ring gear 36. Then, the gears are equally distributed to the side gears 39L and 39R and transmitted to the rear wheels 24L and 24R. Thus, full-time four-wheel drive travel is achieved.

At this time, the left and right wheel rotation speeds NL and NR are also input to the control unit 70, and the flowchart of FIG. 5B is executed.
Therefore, in such normal running, NL ≒ NR and the clutch pressure
Pb is set to substantially zero, and the clutch pressure Pb of the second hydraulic clutch 55 of the differential limit control device 50 is substantially zero due to the duty solenoid valve 69b. For this reason, each part of the rear differential device 30 becomes free, and at the time of turning, freely acts as a differential to absorb the rotational difference.

Next, when starting and accelerating, the clutch pressure Pa depends on the load.
Is set large, the transmission torque of the first hydraulic clutch 45 increases, and the power distribution to the rear wheels increases.
Four-wheel drive performance is improved. At this time, as the clutch pressure Pa also increases, the piston 55f presses the plate 55c and the disk 55d in the second hydraulic clutch 55, and a differential limiting torque is generated between the differential case 35 and the one side gear 39R. For this reason, the left and right rear wheels 24L, 24R are differentially limited and tend to be in the state of differential lock, improving running stability, and effectively transmitting power to the rear wheels 24L, 24R to promote start acceleration. During turning, the clutch pressures Pa and Pb are reduced according to the steering angle θ, the rear wheel power distribution is reduced, and the differential limiting torque is also reduced, so that the vehicle turns smoothly without tight corner braking.

On the other hand, if the front wheel slips on a rough road, the slip is determined based on the rotation speed ΔNa, and the clutch pressure Pa becomes maximum. For this reason, the front and rear wheels are brought into a directly connected state by the first hydraulic clutch 45, and the front and rear wheels are substantially equally distributed in power, thereby preventing a slip and maximizing running performance. Also, when one of the left and right rear wheels 24L, 24R slips, the slip is determined based on the rotation speed difference ΔNb, and the clutch pressure Pb
Is maximized. For this reason, the differential lock is performed by the second hydraulic clutch 55 so that the rear differential device 30 is integrated, and escape from a rough road can be performed. Control of these slips is performed separately for either one or both simultaneously.

In addition, power distribution and differential limiting control are performed according to various running conditions and road surface conditions.

In FIG. 6, another embodiment of the present invention will be described.

In this embodiment, the second hydraulic clutch 55 of the differential limit control device 50 is disposed inside the differential case 35 of the rear differential device 30. That is,
A plate 55c and a disk 55d are installed between the differential case 35 and the hub 55b integral with one side gear 39L inside the differential case 35, and a hydraulic chamber 55e, a piston 55f, and a return spring are mounted on a flange 35b integral with the differential case 35. 55g is installed. Further, the pinion 38 and the side gears 39L, 39 inside the differential case 35 are provided.
The lubricating oil for the clutch is separated from the deflecting gear device including the drive pinion 32 and the ring gear 36 by the oil seal 52 in the portion R and the second hydraulic clutch 55, and the first hydraulic clutch in the extension case 41. An oil passage (not shown) communicates with the lubricating oil 45 to lubricate the pinion 38, the side gears 39L and 39R, and the second hydraulic clutch 55.

In this embodiment, since the hydraulic chamber 55e of the piston 55f and the hydraulic chamber on the side of the return spring 55g are substantially the same, if the differential case 35 is filled with lubricating oil, the centrifugal hydraulic pressure can be canceled. .

The embodiment of the present invention has been described above. The front engine / rear drive (FR) base, the rear engine
It can be applied to a rear drive (RR) base and a horizontal transaxle type, and the transmission may be an automatic transmission or a continuously variable transmission.

Further, in relation to the antilock brake (ABS) control, the torque of the first and second hydraulic clutches 45 and 55 can be controlled during the operation of the ABS to keep the drive system in the most effective coupled state.

〔The invention's effect〕

As described above, according to the present invention, a power distribution device with a hydraulic clutch in a four-wheel drive vehicle,
The system is equipped with a differential limiting control device with a hydraulic clutch to perform both power distribution and differential limiting control.
It can improve running performance, steering stability, starting performance, turning performance, and the like.

In particular, by the combination of power distribution and differential limiting torque,
The performance of a four-wheel drive vehicle can be maximized.

Furthermore, since the power distribution device and the differential limiting control device are mounted on a single differential device, the structure of the transmission and the transfer is reduced,
Moreover, the control system can be integrated into a differential device,
Control response is improved.

In addition, since the power distribution and the differential limitation are controlled by the first and second hydraulic clutches, the electro-hydraulic control system is shared and the electronic control system can be simplified.

Furthermore, since both hydraulic clutches are housed separately from the differential device, and exclusive lubricating oil can be used, there is no occurrence of stick-slip or the like. Also,
The hydraulic chamber and the piston are provided on the fixed side and are not affected by the centrifugal hydraulic pressure.

In another embodiment, by mounting the hydraulic clutch inside the differential case, the structure becomes more compact, and the on-board performance of the differential device and the design flexibility of the supporting method are increased.

[Brief description of the drawings]

1 is an overall configuration diagram showing an embodiment of a driving force control device for a four-wheel drive vehicle of the present invention, FIG. 2 is a horizontal sectional view of a main part, FIG. 3 is a III-III sectional view of FIG. FIG. 4 is a diagram showing a hydraulic and electric control system, FIG. 5 (a) is a flowchart of an operation of a power distribution control, FIG. 5 (b) is a flowchart of an operation of a differential limiting control, and FIG. 6 shows another embodiment. It is sectional drawing. 6 Front wheel, 10 Manual transmission, 24L, 24R Rear wheel, 30
... Rear differential device, 40 ... Power distribution device, 45 ... First hydraulic clutch, 50 ... Differential limit control device, 55 ... Second hydraulic clutch, 62 ... Hydraulic control device,
70 ... Control unit

Claims (4)

(57) [Claims] 1. A four-wheel drive vehicle having a direct transmission configuration to one of the front and rear wheels and a transmission configuration to the other via a power distribution device. The output unit of the first hydraulic clutch is connected to a drive pinion of a deflecting gear unit, which is arranged at an input portion of a front differential device or a rear differential device that is transmitted through a propeller shaft from an output shaft of the machine. A ring gear of the deflecting gear device is provided on the outer periphery of the differential case of the differential device, and a differential limiting control device having a second hydraulic clutch is mounted on the differential device, and the front and rear wheels are transmitted by the transmission torque of the first hydraulic clutch. Of the left and right wheels by the transmission torque of the second hydraulic clutch. Four-wheel drive vehicle, wherein Rukoto driving force control apparatus. 2. The first hydraulic clutch is housed separately from the deflecting gear unit side by an oil seal inside a case protruding from a carrier of the differential device, and at least a hydraulic chamber and a piston are connected to the case by the case. The driving force control device for a four-wheel drive vehicle according to claim 1, which is mounted on the side. 3. The second hydraulic clutch is separated from the side of the deflecting gear device by an oil seal inside a case protruding from a side of a carrier of the differential device, and is provided between the differential case and one of the side gears. 3. The method according to claim 1, wherein
Drive force control device for wheel drive vehicles. 4. The driving force control device for a four-wheel drive vehicle according to claim 3, wherein the second hydraulic clutch has a hydraulic chamber and a piston mounted on the case side.