JPH0569844A - Power steering system controller - Google Patents

Abstract

PURPOSE:To provide a power steering system controller which is simple in structure and inexpensive. CONSTITUTION:A detected value of a steering angular velocity sensor 3 is put into a CPU 6c through a steering angular velocity input circuit 6b. A current detecting circuit 6f detects a current supplied from a motor driving circuit 6d to a motor 7, and the detected value is supplied to the CPU 6c. As this current detected value is in proportion to steering input torque, the size of the steering input torque can be known from this current detected value. The CPU 6c executes unloader control when the current detected value becomes more than a predetermined current value and the steering angular velocity is less than a predetermined value. By this, a torque sensor provided at a conventional device is made unnecessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering system control device, and more particularly to a power steering system control device that drives a hydraulic pump with an electric motor to obtain an assist force.

[0002]

2. Description of the Related Art An example of a conventional power steering system control device will be described with reference to FIG. In the figure,
Reference numeral 1 is a steering wheel, 2 is a steering shaft, 3 is a steering angular velocity sensor, 4 is a torque sensor provided for unloader control, and 5 is an oil passage switching mechanism. An electric control unit (ECU) 6 is composed of a torque input circuit 6a, a steering angular velocity input circuit 6b, a CPU 6c and a motor drive circuit 6d. 7 is a motor, 8 is a hydraulic pump, 9 is a hydraulic cylinder, 10 is a rack, and 11 is a wheel.

The hydraulic pump 8, the oil passage switching mechanism 5 and the hydraulic cylinder 9 are connected to the pipe 8 as shown.
They are connected by a, 8b, 8c and 8d. In Figure 5,
A specific example of the oil passage switching mechanism 5 will be shown. In the figure, 5
Reference numerals a to 5d denote rotary valves connected to the steering shaft 2, and other reference numerals are the same as or equivalent to those in FIG.

The rotary valves 5a-5d are in the open state when no load is applied. When the steering wheel 1 is turned in one direction, the rotary valves 5b and 5c are closed and 5a and 5d are opened, as shown in FIG.
Therefore, the hydraulic pressure A from the hydraulic pump 8 is transmitted to the pipe 8c through the pipe 8a and the rotary valve 5a, and acts on the hydraulic cylinder 9. Further, the hydraulic pressure B generated in the pipe 8d is transmitted to the pipe 8b through the rotary valve 5d and returns to the hydraulic pump 8.

When the steering wheel 1 is turned in the other direction,
As shown in FIG. 3B, the rotary valves 5b and 5c are opened and 5a and 5d are closed. Therefore, the hydraulic pressure A from the hydraulic pump 8 is transmitted to the pipe 8d through the pipe 8a and the rotary valve 5b, and acts on the hydraulic cylinder 9. The hydraulic pressure B generated in the pipe 8c is transmitted to the pipe 8b through the rotary valve 5c and returns to the hydraulic pump 8.

Next, the unloader control of the power steering system control device having the above-mentioned configuration, that is, when the steering input torque exceeds a preset value and the steering rotation is small, the current flowing to the motor 7 is reduced, An operation for preventing wasteful energy loss will be described.

The rudder angular velocity data detected by the rudder angular velocity sensor 3 shown in FIG. 4 is sent to the CPU 6c via the rudder angular velocity input circuit 6b.
Entered in. Further, the torque data detected by the torque sensor 4 is sent to the CP via the torque input circuit 6a.
Input to U6c.

The CPU 6c determines the pulse width modulation duty (hereinafter referred to as PWM duty) D using the steering angular velocity data and the torque data as parameters. FIG. 6 shows the steering angular velocity (horizontal axis) and the PWM duty D (vertical axis).
The PWM duty D gradually increases as the steering angular velocity increases. Also, the PWM duty D
Also depends on the vehicle speed, and the maximum is when the vehicle is stopped (vehicle speed = 0), and is smaller at high speeds to enable smooth steering. Here, V1 is a preset steering angular velocity.

FIG. 7 shows the relationship between the input torque (horizontal axis) and the PWM duty D (vertical axis). The PWM duty D increases almost proportionally until the input torque reaches the set value T2, and the set value T2 is changed. When it exceeds, it gradually decreases.

FIG. 8 shows an outline of the operation of the CPU 6c. When the input torque ≧ T2 is not satisfied (step S
1 is negative), or when the steering angular velocity ≤ V1 is not established (step S2 is negative), the routine proceeds to step S4 and normal control is performed.

On the other hand, input torque ≧ T2 and steering angular velocity ≦ V
1 is satisfied, that is, the input torque is equal to or higher than a predetermined value T2 and the steering angular velocity is a predetermined value V1.
In the following cases, the PWM duty D is gradually reduced to deactivate the motor 7, that is, unloader control is performed. The unloader control is not released until the input torque becomes T1 (see FIG. 7), which is a small predetermined value, and the motor 7 is maintained in the inoperative state.

The CPU 6c operates as described above, and outputs the PWM duty D according to the values of the steering angular velocity and the input torque to the motor drive circuit 6d. Motor drive circuit 6
When the PWM duty D is input, d supplies the electric power corresponding to this to the motor 7. The hydraulic pump 8 generates hydraulic pressure in accordance with the driving force of the motor 7, whereby
The hydraulic cylinder 9 is activated. As a result, an assist force is exerted on the steering drive during normal control.

[0013]

However, according to the above-mentioned conventional device, since the torque sensor 4 is used, the structure of the device is complicated and the cost is increased.

An object of the present invention is to eliminate the above-mentioned problems and to provide a power steering system control device which is simple in construction and inexpensive.

[0015]

In order to achieve the above object, the present invention provides a hydraulic cylinder for generating an assist force for power steering, a hydraulic pump for supplying hydraulic pressure to the hydraulic cylinder, and the hydraulic pump. Current detecting means for detecting a current flowing through a motor for driving the motor, means for detecting a steering angular velocity of the steering wheel, and a current value detected by the current detecting means is equal to or more than a first predetermined value and the steering angular velocity is It is characterized in that it is provided with control means for performing unloader control when the value is equal to or less than the second predetermined value.

[0016]

According to the present invention, the current detecting means detects a current proportional to the steering input torque. Then, when the current value detected by the current detecting means is equal to or higher than the first scheduled value and the steering angular velocity is equal to or lower than the second scheduled value, the unloader control is performed.

As a result, unlike the conventional apparatus, it is possible to manufacture using inexpensive parts without using a torque sensor.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 shows a block diagram of one embodiment of the present invention. In the figure, 6f is a current detection circuit, which detects the current supplied from the motor drive circuit 6d to the motor 7 and supplies the detection data to the CPU 6c. Note that the other reference numerals indicate the same or equivalent parts as those in FIG.

The principle of the present invention is that as the steering input torque increases, the generated pressure of the hydraulic pump 8 increases.
It is noted that the current supplied to the motor 7 that drives the hydraulic pump 8 increases in proportion to the steering input torque.

In this embodiment, the CPU 6c controls the PWM duty D so as to change the detected current I by the current detection circuit 6f in the relationship as shown in FIG. Then, when the detected current I exceeds a predetermined value I1, the data from the steering angular velocity input circuit 6b is referred to, and when the data is smaller than the predetermined value V1 (see FIG. 6), the PWM
The duty D is gradually reduced to gradually reduce the current flowing through the motor 7 and finally to zero.

The operation of the CPU 6c of this embodiment will be described with reference to the flowchart of FIG. In step S1,
It is determined whether the detected current I by the current detection circuit 6f is I1 or more. If the determination is negative, the process proceeds to step S4 and normal control is performed. On the other hand, in the affirmative case, the process proceeds to step S2, and it is determined whether or not the data from the steering angular velocity input circuit 6b is the predetermined value V1 or less.

When this judgment is negative, the routine proceeds to step S4, where normal control is performed. On the other hand, when the determination in step S2 is affirmative, the process proceeds to step S3, and the unloader control is executed.

According to the present embodiment, since the above-described operation is performed, the unloader control similar to the conventional one can be performed without using an expensive torque sensor as in the conventional device, resulting in unnecessary energy loss. Can be prevented. Further, there is an advantage that excessive heat generation in the motor drive circuit 6d and the motor 7 can be prevented and the heat radiation structure of these can be downsized.

[0024]

As is apparent from the above description, according to the present invention, the current detecting circuit is used instead of the torque sensor used in the conventional device, so that the structure is simple and inexpensive. There is an effect that unloader control can be performed by.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a detection current I and a PWM duty.

FIG. 3 is a flowchart for explaining the operation of the embodiment of the present invention.

FIG. 4 is a block diagram showing an example of a conventional device.

FIG. 5 is a detailed explanatory diagram of an oil passage switching mechanism.

FIG. 6 is a diagram showing a relationship between a steering angular velocity and a PWM duty.

FIG. 7 is a diagram showing a relationship between an input torque T and a PWM duty.

FIG. 8 is a flowchart for explaining the operation of the conventional device.

[Explanation of symbols]

1 ... Steering, 3 ... Rudder angular velocity sensor, 5 ... Oil passage switching mechanism, 6 ... Electric control unit (ECU), 6f ... Current detection circuit, 7 ... Motor, 8 ... Hydraulic pump, 9 ... Hydraulic cylinder

Claims (1)

[Claims] 1. A hydraulic cylinder for generating an assisting force for power steering, a hydraulic pump for supplying hydraulic pressure to the hydraulic cylinder, a current detecting means for detecting a current flowing through a motor for driving the hydraulic pump, and a steering wheel. And a control means for performing unloader control when the current value detected by the current detection means is equal to or higher than a first planned value and the steering angular speed is equal to or lower than a second planned value. A power steering system control device comprising: