JPH022748B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic oil flow rate control device for power steering of an automobile.

2. Description of the Related Art Power steering devices are known that use hydraulic pressure to power assist steering operations in order to reduce steering force.

This power steering device is a vehicle speed-sensitive type that reduces the flow rate of hydraulic fluid for power assist as the speed increases, in order to improve steering stability by reducing wheel turning resistance when driving at high speeds. For example, the flow control device of
It is proposed as No.-70972.

This is shown in Fig. 1. 1 is a hydraulic pump that is driven in synchronization with engine rotation, 2 is a flow control device that increases or decreases the flow rate according to the vehicle speed, and 3 is interlocked with the steering system according to the rotation of the handle 4. The switching valve 5 switches while there is a rotational phase difference between the switching valve 3 and the output shaft, and the switching valve 5 is a power cylinder that power-assists the steering operation in response to pressure oil selectively sent in by switching the switching valve 3.

The flow control device 2 uses a signal from a control circuit 7 based on the output of a vehicle speed sensor 6 to control an electromagnetic throttle valve 9 that throttles an orifice 8 and a pressure difference between the throttle valve 9 so that the differential pressure across the orifice becomes constant. and a pressure compensating spool 10 that responds to the pressure.

Therefore, when driving at low speeds with large wheel switching resistance, the electromagnetic throttle valve 9 opens the orifice 8 to a large extent, and therefore, the power cylinder 5 is operated by the switching valve 3 as the steering wheel is operated. A large flow of pressurized oil is delivered, generating a large power assist force and ensuring light steering operation.

On the other hand, when driving at high speeds, the electromagnetic throttle valve 9 throttles the orifice 8 based on the signal from the vehicle speed sensor 6, so most of the hydraulic oil from the pump 1 drains to the reservoir side due to the movement of the pressure compensation spool 10. As a result, the amount of power supplied to the power cylinder 5 is significantly reduced.

For this reason, the steering wheel 4 becomes rather heavy in a high vehicle speed range, which prevents the steering wheel 4 from wobbling or oversteering, thereby improving steering stability.

By the way, in this case, in order to ensure proper operation of the electromagnetic throttle valve 9, the pulse generated from the vehicle speed sensor 6 is converted into frequency and voltage to determine the drive current for the electromagnetic throttle valve 9, and based on this drive current. The generated voltage change of the electromagnetic throttle valve 9 is compared with the voltage generated according to the vehicle speed to perform feedback control.

However, although this is referred to as feedback control, it merely detects the correspondence of the opening degree of the electromagnetic throttle valve 9 to the output of the vehicle speed sensor 6. Strictly speaking, it is a feedback control of the actual flow rate supplied to the power cylinder 5. It's different from what you're controlling.

As a result, even though these devices control the supply flow rate according to the vehicle speed, they cannot escape from the realm of so-called open-loop control, making it difficult to determine whether the actual supply flow rate is being controlled according to the target value. Control accuracy is greatly affected by the performance of the electrical equipment, the accuracy of the parts of the device, and the assembly accuracy, making it difficult to control the accuracy of the entire system and causing many problems in terms of productivity and production costs.

The present invention was proposed in order to solve such problems, and includes a sensor that detects the flow rate actually supplied to the power cylinder, and an electromagnetic throttle valve that increases or decreases the flow rate based on the sensor output. The aim is to accurately control the flow rate in response to vehicle speed, providing accurate power assist at low speeds and improving maneuverability at high speeds.

Embodiments of the present invention will be described below based on the drawings.

In Fig. 2, 9 is an electromagnetic throttle valve that forms a variable throttle, and 11 is a pressure compensation valve (11) that drains a portion of the pump discharge oil in response to the pressure before and after the variable throttle to keep the differential pressure constant. A flow rate sensor 12 for measuring the flow rate supplied to the power cylinder 5 is installed in the wake of this flow control valve (flow control valve).

The flow rate sensor 12 outputs a voltage signal proportional to the flow rate, and feeds back the detected value to a control circuit 13 composed of, for example, a microcomputer.

A voltage signal proportional to the vehicle speed is input from the vehicle speed sensor 6 to the control circuit 13, and based on this, the control circuit 13 controls the opening degree of the electromagnetic throttle valve 9 so as to control the flow rate supplied to the power cylinder 5. Outputs a drive signal to

FIG. 3 shows details of the control circuit 13, where 14 is an input interface that converts the outputs of the vehicle speed sensor 6 and the flow rate sensor 12 into digital signals, and 15 stores the supplied flow rate value according to the driving state (vehicle speed). A storage circuit (ROM) 16 selects the flow rate value stored in the ROM 15 based on the input signal, and a central processing circuit (CPU) 17 calculates the opening degree of the electromagnetic throttle valve 9 so as to obtain this flow rate. This is an output interface that converts the output into a driving current for the electromagnetic throttle valve 9.

The device is configured as described above, and its operation will be explained next.

As shown in FIG. 4, the vehicle speed sensor 6 detects the vehicle speed V.
The flow sensor 12 outputs a voltage signal proportional to the flow rate Q supplied to the power cylinder 5, as shown in FIG.

As shown in FIG. 6, the ROM 15 of the control circuit 13 stores a control target pattern for the flow rate Q according to the vehicle speed V, and the CPU 16 controls the control pattern to obtain this target flow rate characteristic based on the output of the vehicle speed sensor 6. Then, the opening degree of the electromagnetic throttle valve 9 is controlled.

power cylinder 5 in proportion to the opening degree of electromagnetic throttle valve 9.
The actual flow rate value is detected by the flow rate sensor 12, and the CPU
16 will be fed back.

Then, the CPU 16 determines the deviation (flow rate difference) between the target value and the detected value, and outputs a signal to correct the opening degree of the electromagnetic throttle valve 9 so as to eliminate this deviation.

For example, if the detected value is larger than the target value,
The opening degree of the electromagnetic throttle valve 9 is reduced, and conversely, if it is small, the opening degree is increased.

In order to control feedback in this way,
The flow rate actually sent to the power cylinder 5 is
The system now accurately matches the target value depending on the vehicle speed, and as a result, it provides appropriate power assist in low speed ranges and reliably improves steering stability in high speed ranges.

Note that the control target pattern of the supply flow rate can be freely set as necessary.

Next, in the embodiment shown in FIG. 7, a dedicated motor 21 for driving the hydraulic pump 1 is provided, and the control circuit 13 controls the rotation of this motor 21 to control the supply flow rate to the power cylinder 5. In this case as well, the control circuit 13 inputs the signal from the vehicle speed sensor 6, corrects it with the signal from the flow rate sensor 12, and performs feedback control so that the actual flow rate matches the target value. be.

As explained above, the present invention detects the flow rate actually sent to the power cylinder and performs feedback control of the supply flow rate so that the detected value matches the control target value. Regardless of parts accuracy or assembly accuracy, the flow rate can always be accurately controlled to the target according to vehicle speed, providing appropriate power assist in the low to medium speed range and ensuring stable handling in the high speed range. This has the effect of improving the performance.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration circuit diagram of a conventional device, Fig. 2 is a hydraulic circuit diagram showing an embodiment of the present invention, Fig. 3 is the same block diagram, Fig. 4 is an output characteristic diagram of the vehicle speed sensor, and Fig. 5 is a hydraulic circuit diagram showing an embodiment of the present invention. FIG. 6 is a flow rate sensor output characteristic diagram, FIG. 6 is a flow rate control characteristic diagram for the power cylinder, and FIG. 7 is a schematic configuration circuit diagram of another embodiment. DESCRIPTION OF SYMBOLS 1...Hydraulic pump, 3...Switching valve, 4...Handle, 5...Power cylinder, 6...Vehicle speed sensor, 9...Electromagnetic throttle valve, 11...Pressure compensation valve, 12
...Flow rate sensor, 13...Control circuit, 15...
ROM, 16...CPU.

Claims (1)

[Claims] 1 Vehicle speed is detected in power steering equipped with a hydraulic pump, a switching valve that switches according to the rotation of the steering wheel, and a power cylinder to which pressurized oil from the hydraulic pump is selectively fed by the switching operation of the switching valve. a means for controlling the supply flow rate to the power cylinder so as to obtain a target flow rate determined based on the vehicle speed; a means for detecting the supply flow rate; and a means for controlling the supply flow rate so that the detected flow rate matches the target flow rate. 1. A power steering flow rate control device, characterized in that it is equipped with means for feedback control.