JPH09226558A - Vehicle fluid pressure drive - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To accurately control distribution of driving force according to a road surface friction coefficient. A drive axle 10 driven by a prime mover 100.
1, drive-side fluid pressure driving means 102 that is driven synchronously with the drive axle 101 to supply pressurized fluid, driven-side fluid pressure drive means 104 connected to the driven axle 103, and drive-side fluid pressure drive Means 102 and driven side fluid pressure driving means 10
4, a high-pressure flow path 105 and a low-pressure flow path 106 that communicate with 4,
Pressure adjusting means 107 that is interposed between the high-pressure flow passage 105 and the low-pressure flow passage 106 and can change the pressure of the high-pressure flow passage 106.
An antilock braking device 110 for adjusting the braking force of the vehicle, and a road surface friction coefficient estimating means 108 for estimating a road surface friction coefficient μ during the operation of the antilock braking device.
And a driving force control means 109 for driving the pressure adjusting means 107 according to the road surface friction coefficient μ.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a drive device for distributing a driving force of a prime mover to front wheels and rear wheels via fluid pressure.

[0002]

2. Description of the Related Art As a means for distributing driving force to front and rear wheels of a vehicle, instead of a mechanical power transmission mechanism such as a propeller shaft that has been conventionally adopted, the driving force is distributed to a plurality of axles by fluid pressure. Several fluid pressure drive devices have been proposed, for example, Japanese Patent Laid-Open No. 4-92727 is known.

This includes a hydraulic pump connected to a front-wheel drive shaft driven by an engine via an electromagnetic clutch, and a hydraulic motor connected to a rear-wheel drive shaft and driven according to the hydraulic pressure from the hydraulic pump. In addition, the driving force of the engine is distributed to the front wheels and the rear wheels via the fluid pressure.

Further, as disclosed in JP-A-5-131857, a hydraulic pump driven by an engine,
A hydraulic motor that drives the left and right wheels by using the discharge pressure of this hydraulic pump as a drive source and a pressure control valve that regulates the upper limit of the discharge pressure of the hydraulic pump are provided for low μ roads (friction roads). This is intended to suppress excessive idling of the wheels when accelerating on a road surface having a low coefficient μ, and so on.

[0005]

However, in the former example of the former case, when the front wheels run idle on a low μ road such as a snowy road, a pressure is applied to the pump discharge side and a driving force is applied to the hydraulic motor. Although generated, the transfer characteristic of the drive torque with respect to the slip amount is uniquely determined by the discharge amounts of the hydraulic pump and the hydraulic motor, and if the transfer characteristic of the drive torque is determined with respect to the slip amount on a snowy road or the like. However, there was a problem that all four wheels slip on extremely low μ roads such as frozen roads.

On the other hand, in the latter conventional example, when the idling of the drive wheels on the side where the drive system is mechanically connected to the engine is detected, the upper limit of the transmission torque characteristic of the hydraulic motor with respect to the slip amount is lowered. This prevents the wheels from idling due to excessive driving torque and tries to ensure running stability.However, until the wheels idling and the transmission torque characteristics are changed, driving is performed in the same manner as above. There was a problem that performance etc. temporarily deteriorated.

Therefore, the present invention has been made in view of the above problems, and a fluid pressure drive device for a vehicle capable of ensuring drive performance and running stability without causing idling of drive wheels at the time of starting or accelerating. The purpose is to provide.

[0008]

A first aspect of the present invention is, as shown in FIG. 9, a drive axle 101 driven by a prime mover 100.
And a drive side fluid pressure drive means 102 that is driven in synchronization with the drive axle 101 to supply a pressurized fluid, and the driven axle 1
Driven fluid pressure driving means 104, driving side fluid pressure driving means 102 and driven fluid pressure driving means 1
In the vehicle fluid pressure drive device including the high pressure flow passage 105 and the low pressure flow passage 106 communicating with the high pressure flow passage 104, the high pressure flow passage 1 is interposed between the high pressure flow passage 105 and the low pressure flow passage 106.
A pressure adjusting means 107 capable of changing the pressure of 06, an antilock brake device 110 for adjusting the braking force of the vehicle,
A road surface friction coefficient estimating means 108 for estimating a road surface friction coefficient μ while the antilock brake device is operating, and a driving force control means 109 for driving the pressure adjusting means 107 according to the road surface friction coefficient μ are provided.

In a second aspect based on the first aspect, the road surface friction estimating means estimates the road surface friction coefficient μ based on the brake fluid pressure when the antilock brake device commands the holding state. To do.

In a third aspect based on the first aspect, the driving force control means changes the gain of the pressure adjusting means in accordance with the road surface friction coefficient μ.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the driving force control means, when the road surface friction coefficient μ is equal to or less than a predetermined value, transmits torque to a preset rotational speed difference between the drive axle and the driven axle. On the other hand, when the road surface friction coefficient μ exceeds a predetermined value, the transmission torque with respect to the preset rotational speed difference between the drive axle and the driven axle is increased.

[0012]

Therefore, in the first aspect of the invention, on the road surface having a low road surface friction coefficient μ, when the drive axle idles and a rotational speed difference occurs between the drive axle and the driven axle, the drive side fluid pressure drive means and the driven side fluid pressure are generated. The driving force corresponding to the fluid pressure generated by the difference in the number of rotations of the driving means is distributed from the driving axle to the driven axle. At this time, the driving force control means controls the pressure adjusting means according to the road surface friction coefficient μ obtained during braking. The hydraulic pressure applied to the driven-side fluid pressure drive means can be adjusted accurately, and the drive torque distributed to the driven axle can be changed according to the road surface friction coefficient μ during running to prevent idle rotation of the driven axle. This can be prevented, and by estimating the road surface friction coefficient μ while the antilock brake device is operating, the friction coefficient μ can be estimated according to the actual road surface condition and the control accuracy can be improved.

In the second aspect of the invention, when the antilock brake device commands the holding state of the brake fluid pressure, the friction coefficient between the tire and the road surface = the road surface friction coefficient μ becomes maximum, and at this time, The brake fluid pressure, the known friction coefficient of the braking device, the actual road surface friction coefficient μ can be accurately estimated from the wheel load, and the driving force control means does not exceed this road surface friction coefficient μ. The drive force distributed to the driven axle can be adjusted to prevent idling of the driven axle.

According to a third aspect of the invention, the driving force control means is
Since the gain of the pressure adjusting means is changed according to the road surface friction coefficient μ, for example, when the road surface friction coefficient μ is low, the gain is set low, and when the road surface friction coefficient μ is set high, the gain is set to be distributed to the driven axle. The rising of the driving force can be set so as not to exceed the value according to the road surface friction coefficient μ, and idling of the driven axle can be prevented.

According to the fourth aspect of the invention, the torque transmitted from the drive axle to the driven axle is changed according to the road surface friction coefficient μ.
When the road friction coefficient μ is high, the transmission torque increases, and when the road friction coefficient μ is low, the transmission torque also decreases.Therefore, it is possible to ensure the idle rotation of the driven axle during starting or acceleration while responding to changes in the road friction coefficient μ. Can be prevented.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the accompanying drawings.

1 to 3 show an embodiment in which the present invention is applied to a front-wheel drive vehicle to make a four-wheel drive vehicle.
2 is a schematic configuration diagram of a drive system, and FIG. 3 is a schematic configuration diagram of an antilock brake system (hereinafter referred to as ABS).

In FIGS. 1 and 2, the driving force of the engine 1 is transmitted through the output gear 2 a of the transmission 2 to the front wheel side differential device 3.
And a part of the driving force is input to the front wheel 5 via the front axle 4 as a drive axle connected to the output side of the front wheel differential device 3.
And the fluid pressure pump 6 which constitutes the drive side fluid pressure drive means is connected via the front wheel side differential device 3.

A ring gear 3b formed in the differential gear case 3a of the front wheel differential device 3 meshes with a gear 2a connected to the output side of the transmission 2 and is rotationally driven.
A pinion 3d is attached to a pair of pinion shafts 3c formed in the differential gear case 3a, and a pair of side gears 3e coupled to the left and right front axles 4 mesh with these pinions 3d.

The differential gear case 3a
Ring gear 3f formed in parallel with the ring gear 3b
The rotary shaft 6b of the fluid pressure pump 6 is connected via a gear 6a that meshes with.

The suction port 6c of the fluid pressure pump 6 is connected to the discharge port 10b of the fluid pressure pump motor 10 which constitutes the driven fluid pressure driving means via the low pressure pipe 8L as a low pressure passage, and the fluid pressure pump 6 The discharge port 6d is connected to the suction port 10a of the fluid pressure pump motor 10 via a high pressure pipe 8H as a high pressure flow path.

On the other hand, on the side of the rear axle 12 as the driven axle, the ring gear 11b formed on the differential gear case 11a of the rear wheel side differential device 11 is attached to the gear 10d formed on the rotary shaft 10c of the fluid pressure pump motor 10. The rear wheel side differential device 11 is in mesh with each other and has a structure similar to that of the front wheel side differential device 3, and a pair of pinion shafts 1 formed in the differential gear case 11a.
A pinion 11d is attached to 1c, and a pair of side gears 11e coupled to the left and right rear axles 12 mesh with these pinion 11d to form a rear wheel 13 and a fluid pressure pump motor 10.
Are linked.

Fluid pressure motor 6 and fluid pressure pump motor 10
A communication pipe 14 is arranged between a high-pressure pipe 8H and a low-pressure pipe 8L that connect to each other. An electromagnetic proportional throttle valve 20 for changing the throttle according to a command signal from a drive controller 21 is provided in the communication pipe 14. Intervened.

Here, the fluid pressure pump 6 connected to the front wheel 5
The transmission characteristics of the driving torque with respect to the front-rear wheel speed difference (ΔN) of the fluid pressure pump motor 10 connected to the rear wheel 13 will be described. As shown in FIG. 6, the wheel grips the snow surface on a snow-covered road or the like. Road friction coefficient μ on low μ roads
Is relatively high, and the throttle amount of the electromagnetic proportional throttle valve 20 is set so that the upper limit torque and the gain are also increased in accordance with the road surface friction coefficient μ, and maximum drive torque is transmitted within the range of the road surface friction coefficient μ. You can

On the other hand, in the icy road, the throttle amount of the electromagnetic proportional throttle valve 20 is set so that the road surface friction coefficient μ becomes considerably low and the upper limit torque and gain also become low.

By setting such a transmission characteristic, even if the front wheel 5 mechanically connected to the engine runs idle, the transmission torque to the rear wheel 13 is suppressed according to the road surface friction coefficient μ, and the rear wheel is suppressed. It is possible to prevent 13 from slipping.

The drive controller 21 drives the electromagnetic proportional throttle valve 20 so as to obtain the torque transmission characteristics as described above according to the road surface friction coefficient μ estimated as described later, that is, the high pressure according to the road surface friction coefficient μ. By changing the throttle amount from the pipe 8H to the low pressure pipe 8L, the fluid pressure in the high pressure pipe 8H is adjusted, and the drive torque generated by the fluid pressure pump motor 10 is controlled.

The drive controller 21 is mainly composed of a microcomputer and is connected to the ABS controller 33 shown in FIG. 3 through terminals 23, 25 and 27 for reading the road surface friction coefficient μ and the like.

The terminal 23 is provided with a brake signal line 22a for detecting that the driver has stepped on the brake pedal, the terminal 25 is provided with an ABS signal line 24b showing that the ABS controller 33 is operating, and the terminal 27 is provided with the ABS signal line 24b. Is connected to the low μ road signal lines 26b indicating the road surface friction coefficient μ estimated during the operation of the ABS controller 33, and each signal is input to the drive controller 21.

ABS connected to the drive controller 21
The controller 33 detects four wheel speed sensors 34a to 34d and a longitudinal acceleration G of the vehicle as shown in FIG.
The sensor 40 is used as an input to adjust the hydraulic pressure of the brake circuit according to the slip ratio and deceleration of the wheel.
The brake signal line 22 similar to the above is connected between the terminals 23, 25, 27 and the ABS controller 33.
a, ABS signal line 22a and low μ road signal line 26a are provided.

Explaining this brake circuit, the master cylinder 31 that responds to the brake pedal is provided with a master back 30, and the wheel cylinder 3 of each wheel is provided.
Pressure control valve 32 for distributing and adjusting hydraulic pressure to 5a to 35d
And the pressure control valve 32 is driven in response to a command from the ABS controller 33. The wheel speeds from the wheel speed sensors 34a to 34d and the G sensor 4 are connected to each other.
From the pseudo vehicle speed corresponding to the deceleration from 0, the ABS controller 33 drives the pressure control valve 32 to adjust the brake fluid pressure so that the slip ratio of each wheel becomes a predetermined value.

The ABS is a so-called four sensor,
This is a general 4-channel type, and the anti-lock operation according to the deceleration by the G sensor 40 is described in "Automotive Engineering December 1990" (Railway Japan Co., Ltd. 199).
It is as disclosed on pages 56 to 69, etc., issued on Dec. 1, 2000, and will not be described in detail here.

Next, an example of the control performed by the drive controller 21 is shown in the flowchart of FIG. 4, and will be described in detail below with reference to this flowchart.

First, in step S51, the signal line 22a
Of the brake signal is read, and it is determined in step S52 whether or not the brake is operated. If the brake is operated, the process proceeds to step S53. If not, the process returns to step S51.

In step S53, the signal line 24b to AB
The S operation signal is read, and it is determined in step S54 whether the ABS has operated. If the ABS is operating, the process proceeds to step S55. If not, the step S5 is performed.
Return to 1.

In step S55, the signal line 26b to AB
The road surface friction coefficient μ signal estimated and calculated by the S controller 33 is read, and in step S56, it is determined whether the read road surface friction coefficient μ is equal to or less than a predetermined value.

If the read road surface friction coefficient μ is equal to or smaller than the predetermined value, the gain of the driving torque of the fluid pressure pump motor 10 is reduced in step S57, and is set to, for example, the gain of the icy road shown in FIG.

On the other hand, if the road surface friction coefficient μ exceeds the predetermined value, the gain of the drive torque is returned to the predetermined value.
Set to the gain of the snow-covered road shown in.

Thus, by setting the gain of the proportional electromagnetic throttle valve 20 according to the read road surface friction coefficient μ, it is possible to distribute the driving torque according to the road surface friction coefficient μ during traveling.

Next, the estimation calculation of the road surface friction coefficient μ performed by the ABS controller 33 will be described.

The relationship between the brake provided on each wheel and the wheel is
As shown in the one-wheel model of FIG. 7, a brake rotor 63 is coaxially provided on a wheel 64, and a brake caliper 61 driven by a wheel cylinder 62 is arranged at a predetermined position from the center of rotation of the brake rotor 63. Is the brake caliper 61
Is the effective radius of. Further, although not shown in the drawing, a hydraulic pressure sensor is provided in the pipe of each wheel, and the ABS controller 3
3 monitors the brake fluid pressure of each wheel. In addition, 65 is a ground line, and the distance from the rotation center of the wheel 64 to the ground line 65 is the dynamic radius rt of the tire.

In the braking state in which the ABS controller 33 operates, as shown in FIG. 8, the ABS controller 33 repeatedly commands the pressure control valve 32 to increase, hold, and depressurize, and the actual wheel rotation speed is determined by the frictional force with the road surface. The slip ratio is controlled to maximize the slip ratio. At this time, the ABS controller 3
When the brake fluid pressure holding state is commanded, that is, 3 detects the brake fluid pressure p that is the maximum frictional force, and estimates the road surface friction coefficient μ from the following equation.

[0043]

[Equation 1]

Therefore, the drive controller 21 is
The road surface friction coefficient μ obtained by the ABS controller 33 is read during the BS operation, and the proportional electromagnetic throttle is used to increase or decrease the drive torque to the driven side fluid pressure pump motor 10 according to the road surface friction coefficient μ obtained at the time of the previous braking. Control the valve 20,
Now, when traveling in the pattern shown in FIG. 5,
Proportional electromagnetic throttle valve 2 according to road friction coefficient μ obtained during deceleration
When the estimated road surface friction coefficient μ is high, the gain is set high, and when the estimated road surface friction coefficient μ is low, the gain is set low.

At the time of the next start or acceleration, the drive torque distributed to the fluid pressure pump motor 10 is set to a gain (torque transmission characteristic) according to the road surface friction coefficient μ. It is possible to improve the driving performance and the running stability because all the driving wheels do not idle, and the road surface friction coefficient μ can be estimated by A
Since it is performed while the brake fluid pressure is being maintained during BS operation, it is possible to accurately grasp the current road surface state, and drive the driven axle with the maximum drive torque according to the road surface friction coefficient μ. Therefore, the driving force distribution control to the driven axle can be performed with high accuracy by following the actual change of the road surface condition.

[0046]

As described above, according to the first aspect of the invention, when the drive axle idles on a road surface having a low road surface friction coefficient μ and a rotational speed difference occurs between the drive axle and the driven axle, the drive side fluid pressure drive means is provided. And the driving force corresponding to the fluid pressure generated by the rotational speed difference between the driven-side fluid pressure driving means is distributed from the driving axle to the driven axle.
At this time, the driving force control means can drive the pressure adjusting means according to the road surface friction coefficient μ obtained during braking to accurately adjust the fluid pressure to the driven-side fluid pressure driving means, and The drive torque distributed to the driven axle can be changed according to the change of the road surface friction coefficient μ, and the driven axle can be prevented from idling at the time of starting or accelerating. Since it is possible to improve driving performance and running stability, the road surface friction coefficient μ is estimated during the operation of the antilock brake device, so that the road surface condition can be accurately grasped. It is possible to realize highly accurate torque distribution control, and the road surface friction coefficient μ
It is possible to drive the driven axle with the maximum drive torque according to the above.

The second aspect of the present invention is the brake fluid pressure when the anti-lock brake device that maximizes the friction coefficient μ between the tire and the road surface commands the holding state, the known friction coefficient of the braking device, and the wheel. The actual road surface friction coefficient μ can be accurately estimated from the load, and the driving force control means adjusts the driving force distributed to the driven axle so as not to exceed this road surface friction coefficient μ. Can be prevented, and the control accuracy can be improved.

In the third invention, the driving force control means is
Since the gain of the pressure adjusting means is changed according to the road surface friction coefficient μ, for example, when the road surface friction coefficient μ is low, the gain is set low, and when the road surface friction coefficient μ is set high, the gain is set to be distributed to the driven axle. It is possible to set the rising of the driving force that does not exceed the value according to the road surface friction coefficient μ, and to improve the driving performance and running stability by following the changes in the road surface condition and preventing the idle axle from idling. Is possible.

According to the fourth aspect of the invention, the torque transmitted from the drive axle to the driven axle is changed according to the road surface friction coefficient μ.
When the road friction coefficient μ is high, the transmission torque increases, and when the road friction coefficient μ is low, the transmission torque also decreases. Therefore, idling of the driven axle at the time of starting or accelerating is always prevented according to the change of the road friction coefficient μ. Therefore, it is possible to improve driving performance and traveling stability.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a drive device showing an embodiment of the present invention.

FIG. 2 is a block diagram of a driving device.

FIG. 3 is a block diagram of the same ABS.

FIG. 4 is a flowchart showing an example of control similarly performed by the drive controller.

FIG. 5 is a graph showing an example of a traveling pattern and showing a relationship between vehicle speed and time.

FIG. 6 is a graph showing a relationship between a rotational speed difference between a fluid pressure pump and a fluid pressure pump motor and a drive torque or generated pressure.

FIG. 7 is a schematic diagram showing a positional relationship between a brake and wheels.

FIG. 8 is a graph showing a state of ABS operation, showing a relationship between a wheel rotation speed, a command value, a wheel cylinder pressure, and time.

FIG. 9 is a claim correspondence diagram corresponding to any one of the first to fourth inventions.

[Explanation of Codes] 1 Engine 2 Transmission 3 Front Wheel Side Differential 4 Front Wheel 5 Front Wheel 6 Fluid Pressure Pump 8H High Pressure Pipe 8L Low Pressure Pipe 10 Fluid Pressure Pump Motor 11 Rear Wheel Side Differential 12 Rear Axle 13 Rear Wheel 21 Drive controller 30 Master back 31 Master cylinder 32 Pressure control valve 33 ABS controller 34a-34d Wheel speed sensor 35a-35d Wheel cylinder 40 G sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masatsugu Yokote 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd.

Claims (4)

[Claims] 1. A drive axle driven by a prime mover, a drive side fluid pressure drive means which is driven in synchronization with the drive axle to supply a pressurized fluid, and a driven side fluid pressure drive means connected to the driven axle. And a fluid pressure drive device for a vehicle comprising a high-pressure flow passage and a low-pressure flow passage communicating the drive-side fluid pressure drive means and the driven-side fluid pressure drive means, A pressure adjusting means for adjusting the pressure of the high-pressure flow path, an antilock brake device for adjusting the braking force of the vehicle, and a road surface friction for estimating the road surface friction coefficient μ during operation of the antilock brake device. A vehicle fluid pressure drive device comprising: a coefficient estimating means; and a driving force control means for driving the pressure adjusting means according to the road surface friction coefficient μ. 2. The vehicle according to claim 1, wherein the road surface friction estimating means estimates a road surface friction coefficient μ based on a brake fluid pressure when the antilock brake device commands a holding state. Fluid pressure drive device. 3. The vehicle fluid pressure drive device according to claim 1, wherein the driving force control means changes the gain of the pressure adjusting means according to the road surface friction coefficient μ. 4. The road force friction coefficient μ
Is less than a predetermined value, the transmission torque for a preset rotational speed difference between the drive axle and the driven axle is reduced, while when the road surface friction coefficient μ exceeds a predetermined value, transmission is performed for the preset rotational speed difference between the drive axle and the driven axle. The vehicle fluid pressure drive device according to claim 1, wherein the torque is increased.