JP5370331B2 - Vehicle integrated control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle integrated control device which accurately restrains steering torque change associated with left-right wheel differential limiting mechanism operation, and can satisfy both of a running-through performance and stability. <P>SOLUTION: A control means 122 controls a left-right wheel differential limiting mechanism 81, and computes restraining torque Te according to drive torque of an engine with left-right wheel differential limiting effect by the left-right wheel differential limiting mechanism 81 as a torque responsive characteristic portion, then, if a rotation speed difference between a left front wheel 11 and a right front wheel 12 exceeds a threshold, computes restraining torque Tn according to the rotation speed difference with the left and right wheel differential limiting effect as a rotation speed responsive characteristic portion, and subsequently, computes assist torque according to steering torque change estimated from the rotation speed difference. The control means further controls the restraining torque to a total value of proportional restraining torque Te proportional to the drive torque of the engine and the restraining torque Tn, and controls the assist torque according to the proportional restraining torque Te proportional to the rotation speed difference and the rotation speed difference. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to vehicle steering under a situation where the posture of the vehicle becomes unstable, for example, steering by a steering torque change when the right and left wheel differential limiting mechanism is operated on a rough road where the road surface friction coefficient of the right front wheel and the left front wheel is different. The present invention relates to a vehicle integrated control device that suppresses the occurrence of a phenomenon and improves the running performance and stability of the vehicle.

2. Description of the Related Art In recent years, electric power steering, which is a steering assist device capable of controlling a steering force by applying a steering assist force by the force of an electric motor, has been adopted in power steering of vehicles.
This electric power steering has a larger friction than the hydraulic power steering etc. due to the resistance of the electric motor, etc., and the steering is difficult to return to the neutral position. There has been proposed a technique for controlling the electric power steering so that a steering assist force is applied in the direction of returning to the initial position.
In vehicles equipped with a left and right wheel differential limiting mechanism for the purpose of improving the vehicle's driving performance, if the left and right wheel differential limiting mechanism is activated during turning or when traveling on a split road where the road surface friction differs between the left and right tires, There is a concern that the driver may feel uncomfortable during the steering operation.
Therefore, as a steering force control device in a vehicle using such a left and right wheel differential limiting mechanism, an electric power steering which is a steering assist device according to the steering angle and the restraint torque when the left and right wheel differential limiting mechanism is operated is used. There is a control system that suppresses the occurrence of a steering wheel phenomenon due to a change in steering torque and eliminates a sense of incongruity at the time of steering operation by the driver (see Patent Document 1).

Japanese Patent No. 3401336

However, since the actual steering torque change is proportional to the driving force difference between the left and right wheels instead of the restraining torque, when the control proportional to the restraining torque is performed as in the prior art, the control amount becomes excessive, Or it will be insufficient. Further, in the locked state of the left and right wheel differential limiting mechanism, that is, the right and left direct connection state, the steering torque change direction and amount are unknown, and it becomes difficult to control by the electric power steering as a steering assist device. There was a problem that it was insufficient to eliminate the uncomfortable feeling during operation.
In addition, it is difficult to estimate a change in steering torque using a general mechanical left and right wheel differential limiting mechanism, and at the same time, it is difficult to suppress the change in steering torque with electric power steering.
On the other hand, assuming an electronically controlled front left and right wheel differential limiting mechanism that can freely control the restraining torque, the control logic of the left and right wheel differential limiting mechanism that can easily estimate the steering torque change by the left and right wheel differential limiting mechanism By applying this, it is possible to accurately estimate the steering torque change.
General mechanical left and right wheel differential limiting mechanisms include “torque-sensitive” and “rotation speed-sensitive”, and the right and left wheel differential limiting mechanism can be used in different situations. The dynamic limiting mechanism can bring out both merits by control.
It is also conceivable that the “rotational speed sensitive type” is applied to the front electronically controlled left and right wheel differential limiting mechanism to suppress the steering torque change accompanying the operation of the left and right wheel differential limiting mechanism with the additional torque of the electric power steering.
However, this device cannot provide the effect of torque-sensitive left and right wheel differential limiting.
Therefore, it is conceivable to incorporate “torque-sensitive” control into this device, but if torque-sensitive control works strongly, the left and right wheels will be in a direct connection state, and it will be difficult to properly control the additional torque of the electric power steering. Become.

  The present invention has been made in view of such circumstances, and the left and right wheel differential that can accurately suppress the steering torque change associated with the operation of the left and right wheel differential limiting mechanism and eliminate the uncomfortable feeling during the steering operation of the driver. An object of the present invention is to provide a vehicle integrated control device for a limiting mechanism and a steering force control mechanism.

The invention according to claim 1 detects an electronically controlled left and right wheel differential limiting mechanism that controls the restraining torque of the left and right front wheels, a steering force control mechanism that adds a steering assist force, and a difference in rotational speed between the left and right front wheels. A vehicle integrated control apparatus for a vehicle including a wheel speed difference detecting means, wherein the restraint torque of the electronically controlled left and right wheel differential restriction mechanism is a drive torque proportional restraint torque proportional to an engine drive torque, and the left and right front wheels controls the sum of the rotational speed difference proportional restraining torque proportional to the rotational speed difference, the steering assist force, comprising a control means for adding in response to the rotational speed difference between the left and right front wheels, said control means, When the difference between the rotational speeds of the left and right front wheels is equal to or smaller than a predetermined threshold, the rotational speed difference proportional restraint torque is set to 0 and the steering assist force is not added, and the rotational speed difference between the left and right front wheels is a predetermined threshold. If it exceeds, wherein the rotational speed difference proportional restraining torque to calculate a value proportional to the rotational speed difference between the left and right front wheels, is added in accordance with the steering assist force to the rotational speed difference between the left and right front wheels, it And

According to the present invention, the left and right wheel differential limiting effect can be enhanced by applying two controls in combination to the electronically controlled left and right wheel differential limiting mechanism.
Further, by limiting the maximum value of the drive torque proportional restraint torque, it is possible to suppress the influence on the change in the steering torque.
In addition, the steering torque change due to the rotational speed difference proportional restraint torque can be accurately suppressed by the auxiliary steering force of the electric power steering.

1 is a schematic configuration diagram illustrating a configuration of a vehicle to which a left and right wheel differential limiting mechanism and a steering force control mechanism according to an embodiment of the present invention are applied. It is a flowchart which shows operation | movement of the left-right wheel differential limiting mechanism and steering force control mechanism of embodiment of this invention. It is a characteristic view which shows the torque sensitivity characteristic of the electronically controlled front left and right wheel differential limiting mechanism of the embodiment of the present invention. It is a characteristic view which shows the rotation speed sensitivity characteristic of the electronically controlled front left and right wheel differential limiting mechanism of the embodiment of the present invention. It is explanatory drawing which shows the binding force table TBL of embodiment of this invention.

Hereinafter, a first embodiment of the present invention will be described.
FIG. 1 is a schematic configuration diagram showing a configuration of a vehicle 1 provided with a steering force control device of this embodiment. The vehicle 1 includes a left front wheel 11, a right front wheel 12, a left rear wheel 13, and a right rear wheel 14.
The left front wheel 11 and the right front wheel 12 are steering wheels of the vehicle 1 and are connected to an electric power steering 22 via a tie rod 21.

The electric power steering 22 includes a steering gear box 31, a steering shaft 32, a steering wheel 33, and an electric motor 34.
A steering wheel 33 is connected to the steering gear box 31 via a steering shaft 32.
The operation of the steering wheel 33 by the driver is transmitted to the steering gear box 31 via the steering shaft 32.
Further, the tie rod 21 is operated via the steering gear box 31 to change the directions of the left front wheel 11 and the right front wheel 12.
In other words, the steering system for steering the steering wheels (the left front wheel 11 and the right front wheel 12) includes the steering gear box 31, the steering shaft 32, and the steering wheel 33.

The electric motor 34 is provided in the steering gear box 31, and the rotation of the electric motor 34 is input to the steering gear box 31 to generate a steering assist force for the operation of the steering wheel 33.
In other words, the steering assist force is applied to the steering system by the electric motor 34.

The left front wheel 11, the right front wheel 12, the left rear wheel 13, and the right rear wheel 14 are provided with brakes 41, 42, 43, and 44 for applying a braking force to each wheel.
The brake 41 applies braking force to the left front wheel 11, the brake 42 applies braking force to the left front wheel 12, the brake 43 applies braking force to the left rear wheel 13, and the brake 44 applies braking force to the left rear wheel 14. Is granted.
The brakes 41, 42, 43, 44 control the braking force applied to the left front wheel 11, the right front wheel 12, the left rear wheel 13, and the right rear wheel 14 by the hydraulic pressure supplied from the brake hydraulic unit 51 mounted on the vehicle. Is done.

The left front wheel 11, the right front wheel 12, the left rear wheel 13 and the right rear wheel 14 are provided with wheel speed sensors for detecting the wheel speed of each wheel.
The wheel speed sensor 61 is a sensor for detecting the wheel speed (number of rotations) of the left front wheel 11. The wheel speed sensor 62 is a sensor for detecting the wheel speed (rotation speed) of the right front wheel 12. The wheel speed sensor 63 is a sensor for detecting the wheel speed (rotational speed) of the left rear wheel 13. The wheel speed sensor 64 is a sensor for detecting the wheel speed (number of rotations) of the right rear wheel 14.

  A driving force is transmitted to the left front wheel 11 and the right front wheel 12 through a front differential 82 provided with a left and right wheel differential limiting mechanism 81. The left front wheel 11 is connected to the drive shaft 83, and the right front wheel 12 is connected to the drive shaft 84. The left front wheel 11 and the right front wheel 12 are driven to rotate by the driving force transmitted to the drive shaft 83 and the drive shaft 84 via the front differential 82 provided with the left and right wheel differential limiting mechanism 81.

The left and right wheel differential limiting mechanism 81 is an electronically controlled front left and right wheel differential limiting mechanism that can freely control the restraining torque. The left and right wheel differential limiting mechanism 81 generates a torque that restrains the relative rotation of the left and right drive shafts 83 and 84 in accordance with the state of engagement of a built-in electromagnetic clutch (not shown). A differential limiting force is applied to the right front wheel 12. The left and right wheel differential limiting mechanism 81 is also a left and right wheel differential limiting mechanism having a torque sensitivity characteristic or a right and left wheel differential limitation having a rotation speed sensitivity characteristic under the control of a controller 90 forming a part of the control means 122. As a mechanism, it is possible to switch or combine the left and right wheel differential limiting effects.
The controller 90 controls the restraining torque by the left and right wheel differential limiting mechanism 81 by adjusting the excitation current of the engagement state of the electromagnetic clutch. The effect of the left and right wheel differential limiting mechanism 81 by the left and right wheel differential limiting mechanism 81 can be switched to or combined with the torque sensitive characteristic or the rotational speed sensitive characteristic.

The control means 122 also includes a steering ECU 71, a braking system ECU 72, and a control system ECU 73. The steering ECU 71 has a general basic function of adding a steering assist force by the electric power steering 22 for reducing the steering torque of the driver to the steering system by the electric motor 34 as a steering force control function. The control unit 122 also includes a wheel speed difference detection unit 121 that detects a difference in rotational speed between the left front wheel 11 and the right front wheel 12. The control means 122 is proportional to the restraining torque of the electronically controlled left and right wheel differential limiting mechanism 81 in proportion to the driving torque proportional restraining torque proportional to the driving torque from the engine and the rotational speed difference between the left front wheel 11 and the right front wheel 12. While controlling to a total value of the rotational speed difference proportional restraint torque, the steering assist force of the electric power steering 22 is controlled according to the rotational speed difference proportional restraint torque and the rotational speed difference.
The restraint torque Tn1 corresponding to the rotational speed difference Vd1 between the left front wheel 11 and the right front wheel 12 is read from the restraint force table TBL shown in FIG. Then, the steering torque change S1 is estimated from the restraining torque Tn1.
As described above, the control means 122 uses the restraining torque Tn when controlling the differential limiting force by the left and right wheel differential limiting mechanism 81 as information corresponding to the difference in the rotational speeds of the drive shaft 83 and the drive shaft 84, for example. It is provided as a binding force table TBL.

The braking system ECU 72 realizes an ABS (Anti-lock Bracket System) function when braking the vehicle 1 by controlling the brake hydraulic unit 51.
In the ABS function realized by the braking system ECU 72, the lock state of each wheel on the low μ road surface is determined based on the wheel speed detected by the wheel speed sensors 61, 62, 63, 64 when the vehicle 1 is suddenly braked. Then, the brake hydraulic unit 51 is controlled so that an optimal braking force is applied to the wheels by the brakes 41, 42, 43, and 44 while avoiding such a locked state.
The control system ECU 73 performs efficient engine control.

The steering ECU 71, the braking system ECU 72, and the control system ECU 73 are computers, and include a storage device such as a RAM and a ROM, a central processing unit, an input / output device such as a timer and an I / O port, and various interfaces. Wheel speed sensors 61, 62, 63, 64 are connected to the steering ECU 71 and the braking system ECU 72 via the input / output device.
Further, a communication function for transmitting and receiving various data among the steering ECU 71, the braking system ECU 72, and the control system ECU 73 is provided.

In the vehicle integrated control device of this embodiment, the control means 122 executes the software program shown in the flowchart of FIG. 2 to accurately suppress the steering torque change caused by the operation of the left and right wheel differential limiting mechanism. It achieves posture stabilization control that eliminates discomfort during steering operations and improves running performance and stability.
In this attitude stabilization control, when the left and right wheel differential limiting mechanism is activated in a specific driving situation where the attitude of the vehicle 1 becomes unstable, steering accompanying the operation of the left and right wheel differential limiting mechanism is performed. Torque change is accurately estimated to eliminate the driver's uncomfortable feeling during steering operation.

  In the ABS function in the braking system ECU 72, the slip ratios of the left front wheel 11, the right front wheel 12, the left rear wheel 13 and the right rear wheel 14 are determined from the wheel speeds of the respective wheels detected by the wheel speed sensors 61, 62, 63, 64. And the hydraulic pressure supplied from the brake hydraulic unit 51 to the brakes 41, 42, 43, and 44 is controlled so that the calculated slip ratio becomes an optimum value.

Next, the operation will be described.
FIG. 2 is a flowchart showing the operation of the vehicle integrated control apparatus of this embodiment. The operation will be described below according to this flowchart.
First, the control means 122 calculates the driving torque output from the engine. Further, the wheel speed difference detecting means 121 calculates a difference in rotational speed between the left front wheel 11 and the right front wheel 12 from the rotational speeds of the left front wheel 11 and the right front wheel 12 detected by the wheel speed sensor 61 and the wheel speed sensor 62 (step). S1).
Next, the control means 122 controls the left and right wheel differential limiting mechanism 81, and outputs the left and right wheel differential limiting effect by the left and right wheel differential limiting mechanism 81 from the engine as a torque sensitive characteristic as shown in FIG. The restraint torque Te corresponding to the drive torque is calculated (step S2).
Then, it is determined whether or not the rotational speed difference between the left front wheel 11 and the right front wheel 12 exceeds a predetermined threshold β (step S3), and the rotational speed difference between the left front wheel 11 and the right front wheel 12 exceeds the threshold β. Further, calculation for controlling the front left and right wheel differential limiting mechanism is performed (step S4). In this front left and right wheel differential limiting mechanism control, the difference between the rotational speeds of the left front wheel 11 and the right front wheel 12 is determined by using the right and left wheel differential limiting effect by the left and right wheel differential limiting mechanism 81 as a rotational speed sensitive characteristic as shown in FIG. The restraint torque Tn according to the above is calculated.
Subsequently, the control unit 122 performs EPS addition control (step S5). In this EPS addition control, the EPS assist torque Teps is calculated according to the steering torque change estimated from the rotational speed difference between the left front wheel 11 and the right front wheel 12. The steering torque change is estimated by calculating the steering torque change from the rotational speed difference between the left front wheel 11 and the right front wheel 12.
And the control means 122 performs control of the left-right wheel differential limiting mechanism 81 and control of the electric power steering 22 (step S6). In the control of the left and right wheel differential limiting mechanism 81, the proportional torque is proportional to the driving torque from the engine, and the left and right wheel differential limiting mechanism is limited to the rotational speed difference between the left front wheel 11 and the right front wheel 12. In the EPS control of the electric power steering 22, the assist torque Teps of the electric power steering 22 and the steering assist force are proportional to the proportional constraint torque Te proportional to the rotational speed difference and the rotational speed difference. Control.

  On the other hand, if it is determined in step S3 that the rotational speed difference between the left front wheel 11 and the right front wheel 12 does not exceed the threshold value β, the restraining torque Tn corresponding to the rotational speed difference between the left front wheel 11 and the right front wheel 12 is set to zero. (Step S8) Further, the assist torque Teps is also set to zero (Step S9).

In addition, if it comprises further the maximum value prescription | regulation means which restrict | limits the maximum value of a drive torque proportional restraint torque, ie, a torque sensitive restraint torque, to a fixed value, the influence on steering torque can be suppressed small.
The electric power steering, that is, the steering force control mechanism is controlled by setting and controlling the steering assist force according to the rotational speed difference proportional constraint torque proportional to the rotational speed difference between the left and right front wheels. Do not consider.

  As described above, according to this embodiment, the driving torque output from the engine is calculated, and the rotational speeds of the left front wheel 11 and the right front wheel 12 detected by the wheel speed sensor 61 and the wheel speed sensor 62 are calculated. The wheel speed difference detection means 121 calculates the rotational speed difference between the left front wheel 11 and the right front wheel 12. The control means 122 controls the left and right wheel differential limiting mechanism 81, and uses the left and right wheel differential limiting mechanism 81 as a torque sensitive characteristic component to restrict torque according to the drive torque output from the engine. Te is calculated. If the rotational speed difference between the left front wheel 11 and the right front wheel 12 exceeds the threshold value β, the left and right wheel differential limiting mechanism 81 uses the left and right wheel differential limiting effect as a rotational speed sensitive characteristic, and the left front wheel 11 and the right front wheel The restraining torque Tn corresponding to the rotational speed difference of 12 is calculated. Subsequently, as the steering force control, an assist torque Teps is calculated according to a change in the steering torque estimated from the rotational speed difference between the left front wheel 11 and the right front wheel 12. Then, the control of the left and right wheel differential limiting mechanism 81 and the control of the electric power steering 22 are executed, and in the control of the left and right wheel differential limiting mechanism 81, the constraint torque is proportional to the drive torque from the engine, and The total torque and the restraining torque Tn proportional to the rotational speed difference between the left front wheel 11 and the right front wheel 12 are controlled. In the control of the electric power steering 22, the assist torque Teps and the steering assist force of the electric power steering 22 are set to the rotational speed difference. Is controlled in accordance with the proportional restraint torque Te proportional to the rotational speed difference and the rotational speed difference. Therefore, there is an effect that it is possible to provide a steering force control device that can accurately suppress a change in steering torque associated with the operation of the left and right wheel differential limiting mechanism and can achieve both running performance and stability.

  Further, according to this embodiment, since the maximum value defining means for limiting the maximum value of the drive torque proportional restraint torque to a constant value is further provided, the steering force control that can suppress the influence on the steering torque to a small value. There is an effect that a device can be provided.

  Further, according to this embodiment, when the rotational speed difference between the left front wheel 11 and the right front wheel 12 exceeds the predetermined threshold value β, the control means 122 calculates the restraint torque Tn that is the rotational speed difference proportional restraint torque. Since the right / left wheel differential limiting mechanism 81 is switched to the rotational speed sensitive characteristic as shown in FIG. 4, the calculation according to the rotational speed difference between the left front wheel 11 and the right front wheel 12 is performed. Therefore, there is an effect that the steering torque fluctuation due to the restraint torque Tn, which is the rotational speed difference proportional restraint torque, can be accurately suppressed by the electric power steering 22.

  Further, according to this embodiment, the control of the steering assisting force by the control means 122 is configured such that the difference in rotational speed between the left front wheel 11 and the right front wheel 12 exceeds a predetermined threshold value. Since the steering assist force is controlled when the rotational speed difference of the right front wheel 12 exceeds a certain value exceeding the threshold value, the load of the control means 122 is reduced and the restraint torque Tn which is the rotational speed difference proportional restraint torque. There is an effect that the steering torque fluctuation due to can be efficiently suppressed.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 11 ... Left front wheel, 12 ... Right front wheel, 22 ... Electric power steering (steering force control mechanism) 32 ... Steering shaft, 33 ... Steering wheel, 61, 62, 63, 64 ... Wheel speed sensor 71... Steering ECU 81. Left and right wheel differential limiting mechanism 121... Wheel speed difference detecting means 122.

Claims (2)

An electronically controlled left and right wheel differential limiting mechanism for controlling the restraining torque of the left and right front wheels, a steering force control mechanism for adding steering assist force,
A vehicle integrated control device for a vehicle comprising wheel speed difference detecting means for detecting a difference in rotational speed between the left and right front wheels,
The restraint torque of the electronically controlled left and right wheel differential restriction mechanism is a sum of a drive torque proportional restraint torque proportional to the engine drive torque and a rotational speed difference proportional restraint torque proportional to the rotational speed difference of the left and right front wheels. And a control means for adding the steering assist force according to a difference in rotational speed between the left and right front wheels ,
When the rotational speed difference between the left and right front wheels is equal to or less than a predetermined threshold, the control means sets the rotational speed difference proportional restraint torque to 0 and does not add the steering assist force, and the rotational speed of the left and right front wheels. When the difference exceeds a predetermined threshold value, the rotational speed difference proportional restraint torque is calculated as a value proportional to the rotational speed difference between the left and right front wheels, and the steering assist force is determined according to the rotational speed difference between the left and right front wheels. Add
The vehicle integrated control apparatus characterized by the above-mentioned.   2. The vehicle integrated control device according to claim 1, further comprising maximum value defining means for limiting the maximum value of the drive torque proportional restraint torque to a constant value.

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