JP2534732B2 - Drive force distribution controller for four-wheel drive vehicle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a drive force distribution control device for a four-wheel drive vehicle used for a drive force distribution clutch of a transfer device for a four-wheel drive vehicle.

(Prior Art) As a conventional driving force distribution control device for a four-wheel drive vehicle, there is known a device described in, for example, Japanese Patent Laid-Open No. 62-61829.

This conventional device sets a plurality of control characteristics according to the front-rear wheel rotation speed difference, and at least two control characteristics are set in the control characteristics.
It includes a control characteristic showing a wheel drive tendency (suitable for sports running) and a control characteristic showing a four wheel drive tendency (suitable for normal running), and a driver's favorite mode is selected by a manual switching operation by the mode selection means. I can.

(Problems to be Solved by the Invention) However, in such a conventional device, since the mode is manually switched, the operation becomes complicated,
Similar to the case of a part-time four-wheel drive vehicle, there were many mistakes due to forgetting to switch, and it was difficult to drive.

For example, in the case of running like a race competing on a course in which a control characteristic showing a two-wheel drive tendency suitable for sports running is selected, it is not always possible to exhibit satisfactory performance because the course is diverse. Not limited.

Further, if the mode selection means is automatically switched to a level close to the driver's judgment level, it is necessary to obtain a lot of judgment information such as road surface condition, running condition, driving condition, etc., and adjustment of the switching timing. Becomes complicated.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above problems, and in order to achieve the object, the present invention has the following solution means. did.

The solution means of the present invention will be explained with reference to the conceptual diagram of the claims shown in FIG. 1. The solution torque is provided in the middle of an engine drive system for distributing and transmitting the engine drive force to the front and rear wheels, and the transmission torque can be changed by an external clutch engagement force. A four-wheel drive vehicle including a drive system clutch means 1 and a clutch control means 3 which outputs a control signal for increasing or decreasing the engagement force of the drive system clutch means 1 based on a detection signal from a predetermined detection means 2. In the driving force distribution control device, the detection means 2 includes front and rear wheel rotation speed detection means 201 and brake operation detection means 202, and the clutch control means 3 is provided with a plurality of control characteristics according to front and rear wheel rotation speed differences. And setting the clutch control means 3 to select a control characteristic showing a two-wheel drive tendency when the brake is operated and a control characteristic showing a four-wheel drive tendency when the brake is released. And characterized in that it was.

(Operation) When the brake is operated, the control characteristic showing the two-wheel drive tendency is automatically selected by the brake operation signal from the brake operation detection means, and when the brake is released, the four wheels are driven by the brake release signal from the brake operation detection means. The control characteristic showing the tendency is automatically selected. That is, the selection and timing of the control characteristic indicating the two-wheel drive tendency and the control characteristic indicating the four-wheel drive tendency can be easily performed depending on whether the driver can express his / her intention and whether or not the brake operation, which is one of the driving operations, is performed. Become.

Therefore, for example, when the brake operation is performed at the corner entrance during turning from a straight traveling state without the brake operation, the control characteristic showing the four-wheel drive tendency is automatically changed to the control characteristic showing the two-wheel drive tendency. Power slide control becomes possible, and at the corner exit that releases the brake, the control characteristics are changed again to show a four-wheel drive tendency.
You can get out of the corner with a sharp acceleration.

Further, in the vehicle equipped with the anti-skid brake system, the control characteristic showing the two-wheel drive tendency is selected when the brake is operated, so that the distribution of the braking force to the four wheels is suppressed and the interference with the anti-skid brake system can be reduced. .

(Examples) Hereinafter, examples of the present invention will be described in detail with reference to the drawings. In describing this embodiment, a driving force distribution control device for a four-wheel drive vehicle based on rear wheel drive will be described as an example.

 First, the configuration of the embodiment will be described.

As shown in FIG. 2, a four-wheel drive vehicle to which the driving force distribution control device D of the embodiment is applied includes a transfer device 10, an engine 11, a transmission 12, a transfer input shaft 13,
The vehicle includes a rear wheel drive shaft 14, a multi-plate friction clutch (drive system clutch means) 15, a rear differential 16, a rear wheel 17, a front differential 18, a front wheel 19, a gear train 20, and a front wheel drive shaft 21.

The transmission 12 shifts the rotational driving force from the engine 11 according to the gear position selected by the shift operation, and in the embodiment, a type in which two parallel shafts are provided with a gear set having different gear ratios. I use the one.

The transfer input shaft 13 is a shaft that inputs the rotational driving force from the transmission 12 to the multi-plate friction clutch 15 in the transfer device 10.

The rear wheel side drive shaft 14 is directly connected concentrically with the transfer input shaft 13, and the rotational driving force from the transfer input shaft 13 is transmitted as it is.

The multi-plate friction clutch 15 is a clutch whose transmission torque can be changed to the front wheel side by the clutch hydraulic pressure, and includes a clutch drum 15a fixed to the transfer input shaft 13 and the rear wheel side drive shaft 14, and the clutch drum 15a. Friction plates 15b rotationally engaged with each other, a clutch hub 15c rotatably supported on the outer peripheral portion of the input shaft 13, and friction discs 15d rotationally engaged with the clutch hub 15c are alternately arranged. Friction plate 15b
A clutch piston 15e provided at one end of the friction disk 15d, and a cylinder chamber 15f formed between the clutch piston 15e and the clutch drum 15a.
It has.

The rear differential 16 and the front differential 18 include left and right rear wheels 17, 17 and left and right front wheels 19, 19
This is a differential device that distributes and transmits the driving force while allowing the differential to occur.

The gear train 20 includes a first gear 20a provided on the clutch hub 15c, a second gear 20c provided on the intermediate shaft 20b, and a third gear 20d provided on the front wheel drive shaft 21.
And means for transmitting the driving force to the front wheel side by the engagement of the multi-plate friction clutch 15.

The front wheel-side drive shaft 21 is a shaft that transmits rotational driving force to the front wheels 19 of the vehicle.

FIG. 4 shows a specific example of the transfer device 10, in which the multi-plate friction clutch 15, gears and shafts are housed in a transfer case 22.

In FIG. 4, 15g is a dish plate, 15h is a return spring, 24 is a clutch pressure oil input port, 25 is a clutch pressure oil passage, 26 is a rear wheel output shaft, 27 is a lubrication oil passage, and 28 is a pinion for a speedometer. , 29 is an oil seal, 30 is a bearing, 31
Is a nidol bearing, 32 is a thrust bearing, and 33 is a joint flange.

Next, the driving force distribution control device D of the embodiment, as shown in FIG. 3, is a hydraulic pressure generation device 50 as an external device that generates hydraulic pressure for engaging the multi-plate friction clutch 15.
And a hydraulic control device 40 for controlling the hydraulic pressure from the hydraulic pressure generation device 50 to a predetermined clutch hydraulic pressure P.

The hydraulic pressure generating device 50 includes an oil pump 51, a pump pressure oil passage 52, a clutch pressure oil passage 53, a branch drain oil passage 54, a reserve tank 55, and a suction oil passage 56.

The hydraulic control device 40 includes a front wheel rotation speed sensor 41, a rear wheel rotation speed sensor 42, and a brake pedal switch 43 as detection means, and a control unit as a control circuit.
45, and the electromagnetic proportional relief valve 46 (provided in the branch drain oil passage 54) having a valve solenoid 46a and a check oil passage 46b is provided as a control actuator.

The front wheel rotation speed sensor 41 and the rear wheel rotation speed sensor 42 are
They are provided in the middle of the front wheel side drive shaft 21 and the rear wheel side drive shaft 14 and at the positions of the left and right front wheels 19 and 19, etc., and are arranged in proximity to the sensor rotor fixed to the shaft and the sensor rotor to change the magnetic force. A rotation speed sensor or the like is used for detecting the pickup sensor, and the rotation speed sensor 41 or 42 outputs a rotation signal (n
f) and (nr) are output.

The brake pedal switch 43 is provided at the brake pedal position, outputs a switch signal of ON (Bp = 1) when the brake is operated, and OFF (Bp = Bp when the brake is released).
The switch signal 0) is output.

The control unit 45 uses a control circuit centered on a microcomputer mounted on the vehicle, inputs rotation signals (nf) and (nr) from the rotation speed sensors 41 and 42, and basically drives the front and rear wheels. Rotational speed difference ΔN between shafts 21 and 14
(Nr-Nf), and as the rotation speed difference ΔN increases, the command current signal (i) that increases the transmission torque ΔT (clutch oil pressure P) to the front wheels and brings the driving force distribution closer to the four-wheel drive state is obtained. The output to the electromagnetic proportional relief valve 46, as shown in FIG. 5, includes an input interface 451, a RAM 452, a ROM 453, a CPU 454, and an output interface 455 as internal circuits.

The ROM 454 (read-only memory) is a read-only memory.
As control characteristics of the front-rear wheel rotation speed difference ΔN and the front wheel side transmission torque ΔT, Bp = 0 characteristics showing a four-wheel drive tendency and 2
The Bp = 1 characteristic indicating the wheel drive tendency is stored in advance in the form of an arithmetic expression or a map.

The electromagnetic proportional relief valve 46 has a clutch oil pressure P = 0 when the output of the command current signal (i) is the command current value I ^* = 0, but the output of the command current signal (i) is the command current value I ^*. When> 0, the valve moves in the closing direction, and the pump pressure from the oil pump 51 is set to the clutch hydraulic pressure P according to the magnitude of the command current value I ^* by the drain oil amount control (Fig. 6).

The relationship between the clutch oil pressure P and the transmission torque ΔT to the front wheels is expressed by the following equation (Fig. 7).

P = ΔT / (μ ・ S ・ 2n ・ Rm) where μ: Friction coefficient of clutch plate S; Area of pressure acting on piston n; Number of friction discs Rm; Effective radius of torque transmission of friction discs Therefore, increase clutch hydraulic pressure P Then, the transmission torque ΔT to the front wheel side also increases in proportion.

 Next, the operation of the embodiment will be described.

First, the flow of control operation in the embodiment will be described with reference to the flow chart shown in FIG.

In step 100, the front wheel rotation speed Nf and the rear wheel rotation speed Nr are read from the sensors 41, 42, 43.

In step 101, the front and rear wheel rotation speed difference Δ is determined from the front wheel rotation speed Nf and the rear wheel rotation speed Nr read in step 100.
N is calculated.

 The arithmetic expression is ΔE = Nr−Nf.

In step 102, it is determined whether the switch signal from the brake pedal switch 43 is Bp = 0.

If Bp = 0, the process proceeds to step 103, where Bp
= 0 characteristic is selected.

In step 104, the Bp = 0 characteristic and the front and rear wheel rotation speed difference Δ
The transmission torque ΔT to the front wheel side is obtained from N.

If Bp = 1, step 102 to step 1
Go to 05, Bp = 1 characteristic is selected.

In step 106, Bp = 1 characteristic and front / rear wheel rotation speed difference Δ
The transmission torque ΔT to the front wheel side is obtained from N.

In step 107, the signal (i) is output according to the command current value i ^* that obtains the transmission torque ΔT to the front wheels obtained in step 104 or step 106.

In this way, control that automatically switches different control characteristics depending on the presence or absence of brake operation is performed, so the selection and timing of the Bp = 0 characteristic and Bp = 1 characteristic can be expressed by the driver as well as the driving operation. It is easily performed depending on the presence or absence of the brake operation.

For example, when turning the corner, if the left foot is lightly placed on the brake pedal while the right foot accelerator pedal is still depressed, the Bp = 0 characteristic indicating the four-wheel drive tendency is changed to the Bp = 1 characteristic indicating the two-wheel drive tendency. Transmission torque to front wheel ΔT
The power slide control becomes possible because a large amount of driving force is distributed to the rear wheels, and if the left foot is removed at the corner exit, the transmission torque ΔT to the front wheel side increases and a sharp acceleration force can be obtained.

Furthermore, not only the left foot brake, but also the so-called heel and toe can be used for control, and the brake pedal can be turned on and off lightly to provide more controllable driving.

Also, in vehicles equipped with an anti-skid brake system, Bp = 1 that shows a two-wheel drive tendency during brake operation.
Since the characteristics are selected, the distribution of the braking force on the four wheels is suppressed, and the interference with the anti-skid brake system can be reduced.

The embodiment of the present invention has been described in detail above with reference to the drawings.
The specific configuration is not limited to this embodiment, and even if there are design changes and the like within the scope of the present invention, they are included in the present invention.

For example, in the embodiment, as the brake operation detecting means,
Although an example of the brake pedal switch is shown, a pedal touch switch that is turned on / off by simply touching the brake pedal may be used.

In addition, a function for manually switching control characteristics (manual mode)
And an automatic switching mode depending on whether or not the brake is operated according to the present invention.

Further, in the embodiment, the example in which the electromagnetic proportional relief valve is used as the hydraulic pressure control actuator has been shown, but other means, for example, a solenoid opening / closing valve structure may be used when a duty control signal is used.

Further, in the embodiment, the multi-plate friction clutch by hydraulic engagement is shown as the clutch means, but other clutches such as an electromagnetic clutch and a viscous clutch may be used.

(Effects of the Invention) As described above, in the drive force distribution control device for a four-wheel drive vehicle of the present invention, a plurality of control characteristics corresponding to front-rear wheel rotational speed differences are set in the clutch control means. Since the clutch control means is a means for selecting a control characteristic showing a two-wheel drive tendency when the brake is operated and a control characteristic showing a four-wheel drive tendency when the brake is released, it is the driver's intention. It is easy to change the driving force distribution ratio, and you can enjoy the effect that you can enjoy sports driving with sharpness.

Further, since a characteristic indicating a two-wheel drive tendency is selected when the brake is operated during sudden braking, interference with the system is reduced and safety is improved in a vehicle equipped with an anti-skid brake system.

[Brief description of drawings]

FIG. 1 is a conceptual view of claims showing a drive force distribution control device for a four-wheel drive vehicle according to the present invention, and FIG. 2 is a view showing a four-wheel drive vehicle to which a drive system clutch control device according to an embodiment is applied. Is an overall view showing a driving force distribution control device for a four-wheel drive vehicle of an embodiment, FIG. 4 is a sectional view showing a transfer device of the embodiment device, FIG. 5 is a block diagram showing a control unit of the embodiment device, FIG. 6 is a characteristic diagram of the relationship between the clutch oil pressure and the transmission torque to the front wheels, FIG. 7 is a characteristic diagram of the relationship between the command current value and the clutch oil pressure, and FIG. FIG. 9 is a control characteristic diagram of the torque transmitted to the front wheels with respect to the wheel rotation speed difference, and FIG. 9 is a flowchart showing the flow of driving force distribution control operation in the control unit of the embodiment apparatus. 1 ... Drive system clutch means 2 ... Detection means 201 ... Front / rear wheel rotational speed difference detection means 202 ... Brake operation detection means 3 ... Clutch control means

Claims (1)

(57) [Claims] 1. A drive system clutch means, which is provided in the middle of an engine drive system for distributing and transmitting the engine drive force to the front and rear wheels, and is capable of changing the transmission torque by an external clutch engagement force, and detection from a predetermined detection means. And a clutch control means for outputting a control signal for increasing or decreasing the engagement force of the drive system clutch means on the basis of a signal, and a drive force distribution control device for a four-wheel drive vehicle comprising: Including a difference detecting means and a brake operation detecting means, wherein the clutch control means is set with a plurality of control characteristics according to the front-rear wheel rotation speed difference, and the clutch control means is provided with a control characteristic showing a two-wheel drive tendency during brake operation. A drive force distribution control device for a four-wheel drive vehicle, characterized in that it is a means for selecting and selecting a control characteristic showing a four-wheel drive tendency when the brake is released.