JPH06107199A - Power steering device - Google Patents

Abstract

PURPOSE:To provide a power steering that is made up so as to reduce any effect on the startability of an engine due to a power steering pump. CONSTITUTION:A flow control valve 14, controlling the extent of pressure oil to be fed to a steering system from a pump 2 into a constant flow rate according to a pressure differential in front and in the rear of a metering orifice 9, is made so as to be operated by way of opening a solenoid valve 18 installed in a bypass passage 17 bypassing the pressure oil, flowing an inlet passage 16 connecting a lower stream of the metering orifice 9 and the flow control valve 14, to the low pressure side at the time of engine starting, whereby engine load due to the pump 2 at the enginestarting is thus reducible.

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 in which power consumption of a starter motor and a pump, which is a load on an engine at the time of starting the engine, is reduced.

[0002]

2. Description of the Related Art In a power steering apparatus that assists a steering wheel operation with hydraulic pressure, a pump is driven by an engine 1 as shown in FIG. That is, FIG. 4 is a block diagram of a power steering apparatus that employs a hydraulic steering assist system. A pump 2 is connected to the engine 1 by, for example, belt coupling, and the pump 2 supplies pressure oil via a hydraulic circuit 3. Feed to gearbox 4. The gear box 4 has a rack and a pinion, a steering rod 5 is connected to the pinion, and the rack is provided with a cylinder that assists the operation of the rack by acting the pressure oil.
A reservoir tank 6 is connected to the pump 2.

In such a system, the pump 2 is driven by the rotation of the engine 1, and the cylinder is operated by the pressure oil discharged from the pump 2 to assist the handle operation. Therefore, the pump 2 always supplies the pressure oil to the gear box 4, and the operation of the pump 2 is performed by the engine 1.
It is a considerable load for us. By the way, a starter motor 7 is connected to the engine 1 via an overrunning clutch (not shown) and is started by the starter motor 7. At this time, the pump 2 is also rotated by the starter motor and discharges pressure oil. . At this time, the pump 2 attempts to discharge the oil against the resistance of the gear box 4 and the conduit of the conduit communicating with the gear box. Therefore, the pump 2 consumes the starting output of the engine 1.

[0004]

The power steering apparatus of FIG. 4 has a construction in which the starter motor 7, the engine 1 and the pump 2 are directly connected to each other. Therefore, when the engine is started, the engine 1 is rotated via the starter motor 7. When starting, the pump 2 consumes the engine output, deteriorating the engine startability.

An object of the present invention is to solve the above problems, to reduce the power consumption of the pump at the time of starting the engine, and to provide a power steering apparatus in which the influence of the pump on the engine startability is small.

[0006]

SUMMARY OF THE INVENTION The present invention comprises a flow control valve for controlling a constant flow rate of pressure oil supplied from a pump driven by an engine to a power steering apparatus according to a pressure difference across a metering orifice. In the power steering apparatus described above, a bypass flow passage for bypassing the oil flowing through the introduction flow passage connecting the downstream side of the metering orifice and the flow control valve to the low pressure side is provided, and the bypass flow passage is opened at engine startup. A solenoid valve is provided.

[0007]

In the power steering system equipped with the flow control valve,
Due to the flow of pressure oil from the pump started by the start of the engine, a pressure difference is generated before and after the metering orifice immediately after the engine is started. The introduction flow path connecting to the flow rate control valve is directly connected to the low pressure side such as atmospheric pressure through the bypass flow path whose opening area is maximized by the electromagnetic valve that is fully opened at the time of engine startup. Therefore, the above pressure difference occurs from the time of engine start. As a result, the flow control valve allows the pressure oil in the pump supply passage to escape to the reservoir tank to lower the hydraulic pressure when the engine is started, and the influence of the pressure loss that the pump receives from the feed line to the gear box at the time of startup is affected. It is possible to reduce the consumption of engine output by the pump.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the power steering apparatus according to the present invention will be described in detail below with reference to FIG. FIG. 1 shows blocks of the pump 2, the tank 6 and the hydraulic circuit in FIG. The pump 2 is a constant capacity pump driven by an engine, and the pressure oil discharge port of the pump 2 is connected to a supply flow path 8 via a metering orifice 9 and a flow control valve 14. There is. This flow control valve 14
Is slidably bypass valve 14a to the valve chamber 14 ₀ is inserted, the pressure before the passage of the metering orifice 9 to one of the pressure chambers 14b of the compartmented valve chamber 14 ₀ by the bypass valve 14a is introduced An introduction passage 16 connected to the supply passage 8 is connected to the other pressure chamber 14c via a damping orifice 15.

The pressure chamber 14b has a reservoir tank 6 in it.
Alternatively, a bypass hole 14e communicating with the suction side of the pump 2 is formed. The bypass hole 14e is formed in the pressure chamber 14b,
The opening area is controlled by the pressure difference of 14c and the urging force of the spring 14d inserted in the pressure chamber 14c, so that the excess flow is returned to the pump side and the flow rate to the supply flow path 8 is always constant. .

The supply channel 8 is, as described above, the introduction channel 16
By-pass control valve 1
It is connected to a gear box (not shown) via 0. The bypass control valve 10 includes the supply passage 8
There is formed a pressure chamber 10d to which is connected and another pressure chamber 10c partitioned by the control valve 10a. The pressure chamber 10c communicates with the reservoir tank 6 through the bypass hole 10f, and is also connected with a bypass passage 17 that communicates with the introduction passage 16 via an electromagnetic valve 18 having a variable throttle opening.

The solenoid valve 18 is configured so that the opening degree of its aperture 18b is controlled based on a speed signal 21a from a vehicle speed sensor 21 and a switching signal 20a generated by operating an ignition switch 20. Specifically, the solenoid 18a is driven by a control signal 19a from an ECU (electric control unit) 19 which inputs the vehicle speed signal 21a and the switching signal 20a, and the opening of the aperture 18a is controlled. The control signal 19a output from the ECU 19 is output as a current output by D / A conversion.

The control valve 10a is a pressure chamber 10c.
The spring 10b inserted into the pressure chamber 10d presses the locking member 10e provided in the pressure chamber 10d. The locking member 10e prevents the control valve 10a from blocking the flow to the gear box side. The control valve 10a controls the opening area of the bypass hole 10f by the pressure difference between the pressure chambers 10d and 10c.

The present power steering apparatus is constructed as described above, and its operation will be described below with reference to the flow chart of FIG. Before the engine is started, the bypass valve 14a of the flow control valve 14 is on the pressure chamber 14b side and closes the bypass hole 14e, as shown in FIG. Also, the ECU
Reference numeral 19 keeps the solenoid valve 18 closed.

[0014] Now, when the ignition switch 20 is operated, ECU 19 recognizes the switching signal 20a, carry out a command to the maximum Imax of control current to the solenoid 18a by the control signal 19a (see step S _1). As a result, the solenoid 18a fully opens the throttle 18b of the solenoid valve 18, and the pressure chamber 14c of the flow rate control valve 14, together with the introduction passage 16, the bypass passage 17-the throttle 18b of the solenoid valve 18-the pressure chamber 10c of the control valve 10. −
The pressure in the reservoir tank 6 is reduced to, for example, the atmospheric pressure through the bypass hole 10f.

Therefore, a flow q ₂ due to leakage of pressure oil is generated from the supply flow passage 8 on the downstream side of the metering orifice 8 through the introduction flow passage 16 to the bypass flow passage 17, and the pressure oil at the discharge port of the pump 2 is discharged. Pressure P ₀ and pressure chamber 14c of flow control valve 14
There is a pressure difference between the pressure P ₂ and the pressure P ₂ of the pressure oil.
In the flow control valve 14 of the present embodiment, the bypass valve 14a causes the pressure chamber 14c due to the pressure difference P ₀ -P ₂ due to the leakage.
Is pushed to the side, the pressure oil from the supply flow path 8 side is pushed to the pressure chamber 14b.
-Reservoir tank 6 or pump 2 through bypass hole 14e
A flow Q _B of the pressure oil that returns to the suction side of is generated. The engine 1 starts to rotate in this state, and the pump 2
When the engine is about to start, the pump 2 reduces the pressure loss by reducing the pressure oil supply flow rate Q _A to the gear box side due to the above-mentioned recirculation, and reduces the power consumption.
Can be avoided.

Further, in this embodiment, after the pump 2 is started, the solenoid valve 18 is temporarily operated for a while by step S _2.
Is fully open. In this way, by maintaining the solenoid valve 18 fully open even immediately after the pump 2 starts slightly, the pressure difference P ₀ -P ₂ is further increased by the discharge action of the pump 2, and the flow Q due to the bypass hole 14e. By increasing _B , the supply flow rate Q _A to the gear box side is continuously reduced, and the engine 1 is started smoothly in a stable rotation state.
The solenoid valve 18 is fully opened until, for example, the rotation of the engine 1 is stabilized for a predetermined time.

After the engine 1 is in a stable rotation state, the control signal 19a causes the throttle 18b of the solenoid valve 18 to move.
Close. The loop of steps S ₃ to S ₆ are, E after running
This is the operation of the CU 19 and reduces the steering assist force according to the vehicle speed. This loop is executed at unit time intervals. When the vehicle speed signal 21a is read in step S _3, searches a map of characteristics of the vehicle speed vs. solenoid control current shown in FIG. 3 (Step S _4), a control signal 19a to provide a degree of opening of the solenoid valve 18 in accordance with the vehicle speed Solenoid 18
It is supplied to a (step S ₅ ), and the next vehicle speed reading is waited for the timer time of step S ₆ . During this time, the solenoid valve 18 according to the vehicle speed read in step S ₃
The opening degree of is set. The horizontal axis of FIG. 3 is the vehicle speed,
The vertical axis represents the magnitude of the control current. The magnitude of the control current is
It is assumed to be proportional to the opening degree of the solenoid valve 18.

The opening of the solenoid valve 18 thus set by the vehicle speed is proportional to the increase of the vehicle speed, as shown in the characteristic of FIG. 3, and the above-mentioned pressure with respect to the valve chamber 14 ₀ of the flow control valve 14 is increased. The difference P ₀ -P ₂ increases in proportion to the increase in vehicle speed. Therefore, as the vehicle speed increases, the supply flow rate Q _A to the gear box side is reduced, and the steering assist force is reduced by that amount to perform speed-sensitive steering.

When a certain vehicle speed V ₂ on the high speed side is read, the ECU 19 generates a control signal 19a for fully opening the solenoid valve 18, and the steering assist force at high speed becomes constant at a minimum value. In this embodiment, the flow control valve 14 is actuated by utilizing leakage of pressure oil generated from the supply passage 8 to the bypass passage 17 due to the solenoid valve 18 being fully opened almost at the same time as the operation of the ignition switch 21. A pressure difference P ₀ -P ₂ is generated, but if sufficient pressure flow cannot be ensured by the flow control valve 14 with this pressure difference, the pressure generated by the discharge pressure oil of the pump started by a slight rotation of the engine. The flow control valve 14 may be operated by the difference.

Further, the control valve 1 of the supply passage 8
In the case of 0, the control valve 10a is sucked to the pressure chamber 10c side due to the pressure difference P ₁ -P ₂ before and after the damping orifice 15 when the solenoid valve 18 is opened. As a result, when the load pressure on the gear box side increases, the pressure chamber 10d expands and the pressure chamber 10c contracts, and the control valve 1
0 indicates that the communication with the reservoir tank 6 is cut off and the pressure chamber 10
The pressure P _{2 of} c rises. Due to this increase in pressure P ₂ , the bypass valve 14a of the flow rate control valve 14 moves, the discharge flow rate Q _B decreases, the discharge flow rate Q _A to the gear box side increases, and the steering assist is enhanced.

In the above embodiment, the solenoid valve 18 that reduces the steering assist force in accordance with the vehicle speed reduces the pressure loss that the pump 2 receives when the engine is started according to the present invention. However, the present invention is not limited to this. A solenoid valve that operates only when the engine is started may be provided.

[0022]

As described above, according to the present invention, the power steering equipped with the flow rate control valve for controlling the pressure oil supplied from the pump to the gearbox to a constant flow rate according to the pressure difference across the metering orifice. In the device, a bypass passage for bypassing the pressure oil flowing through the introduction passage connecting the downstream of the metering orifice and the flow control valve to the low pressure side is provided, and a solenoid valve that is fully opened at the time of engine start is provided in this bypass passage. By providing the above, the flow rate control valve is activated at engine startup, and the pressure oil in the supply channel of the pump is made to flow to the reservoir tank side or the suction side of the pump, reducing the flow rate supplied to the gearbox side and starting the pump. Therefore, it is possible to reduce the power consumed for reducing the influence on the engine startability by the pump.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a power steering apparatus according to the present invention.

FIG. 2 is a flowchart illustrating the operation of the present invention.

FIG. 3 is a map showing the relationship between the control current to the solenoid valve and the vehicle speed according to the present invention.

FIG. 4 is a configuration diagram showing a power steering system to which the present invention can be applied.

[Explanation of symbols]

2 ... Pump, 6 ... Reservoir tank, 8 ... Supply channel, 9 ...
Throttle, 10 ... Check valve, 12 ... Supply passage, 13 ... Bypass passage, 14 ... Flow control valve, 15 ... Throttle, 16 ... Throttle passage, 17 ... Bypass passage, 18 ... Solenoid valve, 19 ... Controller, 20 ... Ignition switch, 21 ... Vehicle speed sensor.

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

Claims (1)

[Claims] 1. A power steering apparatus including a flow control valve for controlling a constant flow rate of pressure oil supplied from a pump driven by an engine to a steering gear box in accordance with a pressure difference across a metering orifice. A bypass flow path for bypassing the oil flowing through the introduction flow path connecting the downstream side of the orifice and the flow rate control valve to the low pressure side is provided, and the bypass flow path is provided with an electromagnetic valve that opens at engine startup. Power steering device that does.