JPH05345573A - Flow rate control device - Google Patents

Abstract

PURPOSE:To stabilize the maneuverability in a high speed running, and to secure a constant flow rate to a power steering device, by providing a bypass solenoid valve to convert the opening area of a bypass passage according to the car speed, and a bypass control valve to reduce the opening area from the bypass according to the increase of the pressure difference. CONSTITUTION:In a flow rate control device which has a flow rate control valve 15 to control the pressure oil to a power steering device from a pump 10 at a constant flow rate according to the pressure difference at the front side and the rear side of a measuring orifice 13, a bypass passage 23 to bypass the oil flowing through a leading-in passage 22 combining the downstream of the measuring orifice 13 and the flow rate control valve 15, to the lower pressure side, is provided. And the system is composed that the opening area of the bypass passage 23 is to be controlled by a bypass solenoid valve 25 according to the car speed, and the opening area from the bypass passage 23 to the lower pressure side is controlled by a bypass control valve 30 to reduce according to the increase of the pressure difference of the oil pressure at the bypass solenoid valve 25 and at the downstream of the measuring orifice 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle speed response flow rate control device for reducing a flow rate delivered from a pump in response to an increase in vehicle speed, and particularly to a flow rate delivered from an engine driven pump to a power steering device. The present invention relates to a flow rate control device for controlling the constant.

[0002]

2. Description of the Related Art A conventional flow control device is disclosed in Japanese Examined Patent Publication No. 54-5.
571 is shown. According to this one, a flow path that bypasses the oil in the flow path connecting the downstream of the metering orifice and the flow control valve to the oil tank is provided, and the solenoid valve installed in this flow path causes the power steering device to respond to the increase in vehicle speed. Is decreasing the flow rate.

[0003]

However, in the above-mentioned one, since the load pressure in the power steering device rises as the steering wheel is steered, the flow rate per unit time passing through the solenoid valve increases and the surplus from the flow control valve increases. The flow will increase. Therefore, since the flow rate to the power steering device is reduced, the assisting force of the power steering device is reduced, which may impair the steering feeling of the steering wheel.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, in which oil flowing in an introduction flow path connecting a downstream side of a metering orifice and a flow control valve is directed to a low pressure side. Depending on the increase in the pressure difference between the bypass solenoid valve that provides a bypass flow passage for bypassing and changes the opening area of this bypass flow passage according to the vehicle speed, and the oil pressure downstream of this bypass solenoid valve and the oil pressure downstream of the metering orifice. And a bypass control valve for changing the opening area from the bypass flow path to the low pressure side to reduce the opening area.

[0005]

The pressure oil discharged from the pump is supplied to the power steering apparatus after being controlled to a constant flow rate by the metering orifice and a flow rate control valve which operates according to the pressure difference across the metering orifice. As the opening area of the bypass flow passage is increased by the bypass solenoid valve in response to the increase in vehicle speed, the flow rate to the low pressure side increases and the surplus flow from the flow control valve increases. It Then, when the load pressure in the power steering apparatus rises, the pressure downstream of the metering orifice rises and the pressure difference from the pressure downstream of the bypass solenoid valve increases. Therefore, the bypass control valve is operated so as to reduce the opening area toward the low pressure side so as to keep this pressure difference constant, and the flow rate to the power steering apparatus does not decrease due to the load pressure, and a uniform flow rate can be secured.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, 10 is a pump driven by an automobile engine. The discharge port of the pump 10 is connected to the supply passage 21 via the metering orifice 13 and the flow control valve 15. In this flow control valve 15, a bypass valve 17 is slidably inserted in a valve hole 18, and one pressure chamber 11 of the valve hole 18 defined by this bypass valve 17 has a pressure before passing through the metering orifice 13. Is introduced, and an introduction flow path 22 connected to a supply flow path 21 is connected to the other pressure chamber 12 via a damping orifice 20.

The pressure chamber 11 has a reservoir tank 45.
Alternatively, a bypass hole 14 communicating with the suction side of the pump 10 is formed. This bypass hole 14 is provided in the pressure chambers 11, 1
The opening area is controlled by the pressure difference of 2 and the urging force of the spring 16 inserted into the pressure chamber 12, so that the excess flow is returned to the pump suction side and the flow rate to the supply flow path 21 is always constant. There is.

The supply flow passage 21 is connected to the introduction flow passage 22 as described above, and communicates with a servo valve of a power steering device (not shown) through a bypass control valve 30. This bypass control valve 30 has
A pressure chamber 41 to which the supply passage 21 is connected and another pressure chamber 42 defined by the control valve 31 are formed. The pressure chamber 42 communicates with the reservoir tank 45 from a bypass hole 36, and an introduction flow path is provided via a bypass solenoid valve 25 whose throttle opening degree is controlled by an ECU (electric control unit) 26 to which a vehicle speed signal is input. It is connected to a bypass flow path 23 communicating with 22.

As shown in FIG. 2, the bypass solenoid valve 25 is closed by the ECU 26 at low speed.
The opening gradually starts from the vehicle speed V1, the opening area increases as the vehicle speed increases, and the vehicle is fully opened at the vehicle speed V2. The control valve 31 includes a locking member 35 provided in the pressure chamber 41 by a spring 32 inserted in the pressure chamber 42.
Is pressed against. The locking member 35 locks the control valve 31 so as not to block the flow to the servo valve. The control valve 31 includes a pressure chamber 41,
The opening area of the bypass hole 36 is controlled by the pressure difference of 42.

The operation of the above configuration will be described below.
The pressure oil discharged from the pump 10 is the measurement orifice 13
By the action of, a pressure difference P0-P1 is generated before and after that. Due to this pressure difference P0-P1, the bypass valve 17 of the flow control valve 15 is operated against the biasing force of the spring 16, and an excess flow is made to flow from the bypass hole 14 to the suction side of the pump 10 or the reservoir tank 45. As a result, a constant flow rate of pressure oil is supplied from the supply passage 21 to the servo valve (not shown).

The bypass solenoid valve 25 provided in the bypass passage 23 is controlled by the ECU 26 so that the opening area is enlarged as the vehicle speed increases, and the flow rate to the bypass control valve 30 is controlled. That is, FIG.
Since the bypass solenoid valve 25 is closed at a low speed as shown in (3), the flow rate from the bypass solenoid valve 25 to the downstream is lost and the flow rate to the reservoir tank 45 via the bypass control valve 30 becomes zero. Therefore, the maximum flow rate Q1 is supplied to the servo valve.

Then, when the vehicle speed becomes V1, the bypass solenoid valve 25 starts to open, and the opening area increases as the vehicle speed increases. Then, the flow rate to the reservoir tank 45 increases according to the vehicle speed. Further, the pressure P of the bypass flow path 23
2 decreases, and accordingly the pressure chamber 1 of the flow control valve 15
Since the pressure of 2 is reduced, the bypass valve 17 is lowered and the excess flow flowing from the bypass hole 14 is increased. Therefore, the flow rate to the servo valve gradually decreases according to the vehicle speed. When the opening area of the bypass solenoid valve 25 becomes maximum, the flow rate to the servo valve becomes the minimum flow rate Q2.

As described above, the bypass solenoid valve 25 controls the flow rate to the servo valve according to the vehicle speed. When the load pressure PG from the servo valve increases as the steering wheel is steered, the pressure P1 in the supply passage 21 increases, so that the pressure difference P1-P2 between the pressures P1 and P2 before and after the damping orifice 20 is generated.
Occurs. Therefore, the control valve 31 is moved to the right side according to the pressure difference P1-P2, and the reservoir tank 45 is moved.
Since the opening area to the servo valve is reduced in accordance with the increase in pressure, the flow rate to the servo valve can be ensured without being reduced by the load pressure PG.

In the above embodiment, when the load pressure rises, the bypass control valve operates according to the pressure difference before and after the damping orifice. However, the bypass control valve is not limited to the damping orifice and may operate by the front and rear pressure due to the throttling effect of the bypass solenoid valve. Good. Further, the bypass control valve is connected to the reservoir tank in order to improve heat dissipation, but it may be returned to the pump suction side.

Although only the vehicle speed signal is input to the ECU 26, an oil temperature signal may be added to perform finer flow rate control.

[0016]

As described above, according to the present invention, the flow area to the low pressure side is increased by increasing the opening area of the bypass solenoid valve as the vehicle speed increases, and the pressure generated in one pressure chamber of the flow control valve is increased. Is reduced to increase the flow rate discharged to the low pressure side as a surplus flow, so that the maneuvering performance during high speed traveling is stabilized. Further, since the bypass control valve that changes the opening area to the low pressure side according to the pressure difference between the metering orifice downstream and the bypass solenoid valve downstream generated by the load pressure from the power steering device is provided, the steering wheel power It is possible to secure a constant flow rate to the power steering device even when the load pressure in the steering device increases.

[Brief description of drawings]

FIG. 1 is a hydraulic system diagram showing a flow rate control device of the present invention.

FIG. 2 is a flow rate characteristic diagram showing a change in flow rate to the power steering apparatus according to a vehicle speed.

[Explanation of symbols]

 10 Pump 13 Metering Orifice 15 Flow Control Valve 17 Bypass Valve 20 Damping Orifice 22 Introduction Flow Path 23 Bypass Flow Path 25 Bypass Solenoid Valve 30 Bypass Control Valve 31 Control Valve 45 Reservoir Tank

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Goya Kato 1-1-1, Asahi-cho, Kariya city, Aichi prefecture Toyota Koki Co., Ltd.

Claims (1)

[Claims] 1. A flow rate control device comprising a flow rate control valve for controlling a constant flow rate of pressure oil supplied from a pump to a power steering device according to a pressure difference across a metering orifice,
And a bypass solenoid valve for changing the opening area of the bypass passage according to the vehicle speed by providing a bypass passage for bypassing the oil flowing through the introduction passage connecting the downstream side of the metering orifice and the flow control valve to the low pressure side. A bypass control valve for changing the opening area from the bypass flow passage to the low pressure side in accordance with an increase in the pressure difference between the hydraulic pressure downstream of the bypass solenoid valve and the hydraulic pressure downstream of the metering orifice. A flow control device characterized by the above.