JP2629796B2 - Differential limit torque control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a differential limiting torque control device capable of variably controlling differential limiting torque of left and right driving wheels by controlling engagement force of a differential limiting clutch.

(Prior Art) Conventionally, as a differential limiting torque control device, a hydraulic clutch is used as a differential limiting clutch, and the clutch pressing pressure is variably controlled by an external hydraulic control means, so that a proportional relationship with the clutch pressing pressure is obtained. (For example, Japanese Patent Application Laid-Open Nos. 62-103226 and 62-103227).

(Problems to be Solved by the Invention) However, such a conventional differential limiting torque control device has a configuration in which the clutch pressing pressure is controlled in an open loop with respect to the engagement force control of the differential limiting clutch. Therefore, for example, when the characteristic of the differential limiting torque (hereinafter, ΔP−ΔT characteristic) with respect to the clutch pressing pressure of the differential limiting clutch changes due to aging or deterioration of oil, the control accuracy of the differential limiting torque is increased. There was a problem of lowering.

To describe a specific example, the turning radius R and the centripetal acceleration Yg
When the differential limiting torque is controlled by the following, the relationship between the magnitude of the turning radius R, the magnitude of the centripetal acceleration Yg, and the differential limiting torque target value ΔT ^* is set in advance. When the value of the centripetal acceleration Yg is obtained, and based on the value, the differential limiting torque target value ΔT ^* is determined from the set relationship, a clutch pressing pressure command signal that can obtain the differential limiting torque target value ΔT ^* is obtained. It will be output unilaterally.

That is, the detected value ΔT ₀ of the differential limiting torque ΔT actually generated between the left and right driving gap wheels is taken as input information,
Since the control is not such that this detected value ΔT ₀ matches the differential limiting torque target value ΔT ^* , the ΔP-ΔT characteristic of the differential limiting clutch changes due to aging or oil deterioration as described above. In this case, a large difference occurs between the actual differential limiting torque ΔT and the differential limiting torque target value ΔT ^* due to the effect of the characteristic change, and a desired differential limiting effect cannot be obtained.

(Means for Solving the Problems) The present invention solves the above problems, that is,
An object of the present invention is to provide a differential limiting torque control device that improves the control accuracy of the differential limiting torque by introducing feedback control under predetermined conditions.

To achieve the above object, the differential limiting torque control device of the present invention, as shown in the conceptual diagram of the claim of FIG. 1, controls the differential force of the left and right driving wheels 2 and 3 by controlling the engagement force of the differential limiting clutch 1. In a vehicle provided with a differential limiting torque control means capable of variably controlling the torque, a differential limiting torque detecting means 5 for detecting the differential limiting torque and a differential detecting a differential rotational speed of the left and right driving wheels 2 and 3 are provided. Dynamic rotational speed detecting means 6 is provided, and the differential limiting torque control means 4 feeds back the differential limiting torque detected value when the differential rotational speed detected value exceeds a predetermined fixed value. This is means for performing the dynamic limiting clutch engagement force control, and performing the differential limiting clutch engagement force control in an open loop without feeding back the differential limiting torque detection value when the differential rotation speed detection value is equal to or less than a predetermined value. It is characterized by things.

(Operation) When the differential rotation speed detection value exceeds a predetermined value, the differential limiting torque control means 4 takes in the differential limiting torque detection value as input information, and outputs the differential limiting torque. Until the detected value matches the differential limit torque target value, the differential limit clutch engagement force control is performed in a closed circuit, that is, while circulating the signal in a feedback loop.

When the differential rotation speed detection value is equal to or less than a predetermined value, the differential limiting torque control means 4 does not feed back the differential limiting torque detection value, but an open loop so that the differential limiting torque target value can be obtained. , The differential limiting clutch engagement force control is performed.

Here, when the differential rotation speed detection value is below a certain value,
Open-loop control, instead of feedback control, is a function of differential limiting. When there is no differential rotation speed between the left and right driving wheels, the differential limiting is actually performed even if the clutch engagement force is applied from outside. If feedback control is performed using the detected differential limiting torque value as input information without generating torque, the differential limiting torque detection value becomes zero, and the value of the differential limiting torque target value diverges, which is not preferable. .

Therefore, by selectively using feedback control and open-loop control depending on whether the differential rotation speed detection value exceeds or falls below a certain value, the control system can quickly set the target value even if the target value changes or disturbance is applied. A stable control system converges to the value, and the control accuracy of the differential limiting torque that always obtains the desired differential limiting performance can be ensured regardless of the change in the ΔP-ΔT characteristic of the differential limiting clutch.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

 First, the configuration will be described.

As shown in FIG. 2, a rear-wheel drive vehicle to which the differential limiting torque control device of the embodiment is applied includes an engine 10, a transmission 11, a propeller shaft 12, a differential
13, drive shafts 14,15, rear wheels 16,17, front wheels 18,19.

The differential limiting torque of the left and right rear wheels 16 and 17 is variably controlled by controlling the engagement force of the differential limiting clutch 20 (such as a wet multi-plate friction clutch) built in the differential 13 similar to the above-described known technology. Differential torque control is
The pressurized oil from the external hydraulic pressure source 30 is set to a predetermined clutch pressing pressure ΔP via the differential limit control valve
It is performed by leading to 20.

A control 32 that outputs a valve drive signal (i) to the differential limiting control valve 31 includes a control unit 33,
A differential amplifier 34, a PI controller 35, a changeover switch 36, a differential rotation speed detector 37, and a valve drive circuit 38 are provided.

The detection signals from the accelerator opening sensor 40, the lateral G sensor 41, the turning radius sensor 42, the right rear wheel speed sensor 43, and the left rear wheel speed sensor 44 are input to the control unit 32. 34, detection signals from the right torque sensor 45 and the left torque sensor 46 are input, and the differential rotation speed detector 37 includes a right rear wheel speed sensor 43 and a left rear wheel speed sensor 44.
Is input.

 Next, the operation will be described.

First, the flow of the differential limiting control operation in the controller 32 will be described with reference to the flowcharts shown in FIGS.

FIG. 3 is a flow chart showing the flow of the switching operation between feedback control and open loop control which are always performed while monitoring the differential rotation speed ΔNrl. FIG. 4 is a flowchart showing the feedback operation which is performed every predetermined control cycle. FIG. 5 is a flowchart showing the flow of the control operation, and FIG. 5 is a flowchart showing the flow of an open-loop control operation performed every predetermined control cycle.

In step a, the right rear wheel speed NRR and the left rear wheel speed NRL are read by the differential rotation speed detector 37.

In step b, the differential rotational speed detector 37 calculates the differential rotational speed ΔNrl from the right rear wheel speed NRR and the left rear wheel speed NRL.

 The equation for calculating ΔNrl is as follows.

ΔNrl = | NRR + NRL | In step c, the differential rotational speed detector 37 determines whether or not the differential rotational speed ΔNrl exceeds a predetermined value α (for example, a small value close to zero).

When ΔNrl> α, the process proceeds from step c to step d, and a command for selecting the contact point a is output from the differential speed detector 37 to the changeover switch 36.

By selecting the contact a, the differential limiting torque detection value ΔT ₀
Is performed as input information (step e).

When ΔNrl ≦ α, the process proceeds from step c to step f, and a command for selecting the contact point b is output from the differential rotation speed detector 37 to the changeover switch 36.

Open loop control is performed by selecting the contact b (step g).

 Next, the feedback control will be described.

In step 100, the control unit 33 reads the input information of the accelerator opening A, the lateral acceleration Yg, the turning radius R, the right rear wheel speed NRR, and the left rear wheel speed NRL.

In step 101, the differential limiting torque target value ΔT ^* is obtained in the control unit 33 based on the input information (see Japanese Patent Application No. 62-244565).

The control unit 33 has a memory circuit
A RAM, a ROM, a CPU as an arithmetic processing circuit, and the like are included.

In step 102, the differential amplifier 34 outputs the differential limiting torque detection value ΔT ₀ based on the input signals from the left and right torque sensors 45 and 46.

In step 103, the differential limiting torque target value ΔT ^*
The PI controller 35 obtains a differential limiting torque target correction value ΔΔT ^** by PI control based on input information of the differential limiting torque detection value ΔT ₀ and the differential limiting torque detection value ΔT ₀ .

The PI control means that the proportional operation (P operation) and the integral operation (I operation) are used together in accordance with the value of (ΔT ^* −ΔT ₀ ), that is, the proportional operation of the deviation and the integral of the deviation. The PI controller 35 itself forms a closed-loop feedback circuit by a kind of feedback control that corrects the command value so that the remaining deviation is canceled by the integration operation.

In step 104, a valve drive signal (i) for obtaining the differential limiting torque target correction value ΔT ^** obtained in step 103 is output.

 Next, the open loop control will be described.

In step 200, the control unit 33 reads the input information of the accelerator opening A, the lateral acceleration Yg, the turning radius R, the right rear wheel speed NRR, and the left rear wheel speed NRL.

In step 201, the control unit 33 obtains a differential limiting torque target value ΔT ^* based on the input information.

In step 202, a valve drive signal (i) for obtaining the differential limiting torque target value ΔT ^* obtained in step 201 is output.

 Next, the operation during traveling will be described.

When the differential rotation speed detection value ΔNrl exceeds a predetermined constant value α, the changeover switch 36 is switched to the contact a side, so that the controller 32 sets the differential limiting torque detection value ΔT ₀ The engagement force control of the differential control clutch 20 is performed by the feedback control taken in as input information.

When the differential rotation speed detection value ΔNrl is equal to or smaller than the fixed value α, the changeover switch 36 is switched to the contact b side.
Without feedback of T ₀ , the differential limit torque target value ΔT
^The open-loop control that obtains ^* controls the engagement force of the differential limiting clutch 20.

Here, when the differential rotation speed detection value ΔNrl is equal to or smaller than the fixed value α, the control in the open loop instead of the feedback control is performed by the difference between the left and right drive wheels 16 and 17 due to the function of limiting the differential. When the dynamic rotational speed does not occur, the differential limiting torque ΔT is not actually generated even if the clutch engaging force is applied from the outside, and the differential control is performed by performing the feedback control using the differential limiting torque detection value ΔT ₀ as input information. Because the detected limit torque value ΔT ₀ becomes zero, the value of the differential limit torque target value ΔT ^* diverges, which is not preferable.

For example, when the turning radius R is infinite (that is, when traveling straight),
It is assumed that a predetermined clutch engagement force is applied to oppose disturbance such as a cross wind.

However, when a disturbance such as a cross wind is acting, the differential limiting torque ΔT is actually generated to correct the disturbance.
When the vehicle travels straight without disturbance such as a cross wind that causes the vehicle to yaw, the actual differential limiting torque ΔT is zero despite the fact that the clutch engagement force is given as the differential limiting torque target value ΔT ^*. Becomes At that time, (ΔT ^* −Δ
If feedback control based on T ₀ ) is performed, ΔT ₀ =
Since it is 0, the value of the differential limiting torque target value ΔT ^* diverges.

That is, performing the feedback control is meaningful at least in the region where the differential rotation speed ΔNrl> 0, that is, the region where the differential is generated and the actual differential limiting torque ΔT is generated in an attempt to limit the differential.

As described above, in the differential limiting torque control device according to the embodiment, the differential rotation speed detection value ΔNrl is equal to the constant value α.
The control system is a stable control system that quickly converges to the target value even if the target value changes or disturbance is applied, because the device uses the feedback control and the open loop control depending on whether it exceeds or is less than Therefore, regardless of the change in the ΔP-ΔT characteristic of the differential limiting clutch 20, the control accuracy of the differential limiting torque ΔT that can always obtain the desired differential limiting performance can be ensured.

As described above, the embodiments have been described based on the drawings. However, the specific configuration is not limited to the embodiments, and even if there is a design change or the like without departing from the gist of the present invention, it is included in the present invention. .

For example, in the embodiment, an example has been described in which the differential limiting torque control is controlled by the turning radius R, the centripetal acceleration Yg, and the like, but the specific control content is not limited to the embodiment.

(Effects of the Invention) As described above, in the differential limiting torque control device of the present invention, the differential limiting torque control means sets the differential rotational speed detection value to a value exceeding a predetermined constant value. When the differential limit torque detection value is fed back, the differential limit clutch engagement force control is performed, and when the differential speed detection value is less than a certain value, the differential limit torque detection value is opened without feedback. Since this is a means for controlling the engagement force of the differential limiting clutch in a loop, a desired differential limiting performance can always be obtained irrespective of a change in the ΔP-ΔT characteristic of the differential limiting clutch due to, for example, aging or deterioration of oil. The effect that the control accuracy of the differential limiting torque can be ensured.

[Brief description of the drawings]

FIG. 1 is a conceptual view of a claim showing a differential limiting torque control device of the present invention, FIG. 2 is an overall view showing a rear wheel drive vehicle to which the differential limiting torque control device of the embodiment is applied, and FIG. FIG. 4 is a flowchart showing the flow of a switching operation between feedback control and open loop control performed while monitoring the dynamic rotational speed, FIG. 4 is a flowchart showing the flow of feedback control operation, and FIG. It is a flowchart figure which shows. 1 ... differential limiting clutch 2 ... left driving wheel 3 ... right driving wheel 4 ... differential limiting torque control means 5 ... differential limiting torque detecting means 6 ... differential rotational speed detecting means

Claims (1)

(57) [Claims] 1. A vehicle having differential limiting torque control means capable of variably limiting differential limiting torque of left and right drive wheels by controlling engagement force of a differential limiting clutch, wherein differential limiting detecting the differential limiting torque is performed. A torque detection unit, and a differential rotation speed detection unit that detects a differential rotation speed of the left and right drive wheels, wherein the differential limiting torque control unit determines that the differential rotation speed detection value exceeds a predetermined value. When the differential limit torque detection value is fed back, the differential limit clutch engagement force control is performed, and when the differential speed detection value is below a certain value, the differential limit torque detection value is not fed back. A differential limiting torque control device, which is means for controlling a differential limiting clutch engagement force in an open loop.