JPS6185272A - Power steering device - Google Patents

Abstract

PURPOSE:To compensate insufficient supply of pump during the time required for rising of rotation of motor upon abrupt steering by arranging an accumulator in an oil circuit between a hydraulic pump and a hydraulic actuator at the steering section. CONSTITUTION:The steering section 1 is constructed with a changeover valve 1a and a hydraulic actuator 1b comprising a piston 1c and a cylinder 1d. The working oil functioning to the hydraulic actuator 1b is fed from a hydraulic pump 2 to be driven through a motor 3. Said motor 3 is rotated through a controller 8 only when required. A check valve 5 and an accumulator 4 are arranged in an oil circuit between said pump 2 and the steering section 1 while sensors 6, 7 for detecting the circuit pressure are arranged in the circuit to feed the input signals to the controller 8.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a power steering system for an automobile, particularly a power steering system that controls a hydraulic actuator of a steering section using pressure oil from a hydraulic pump using an electric motor as a drive source. Regarding equipment.

[Conventional technology]

Conventionally, power steering devices have controlled hydraulic actuators in the steering section using pressure oil from a hydraulic pump whose drive source is an engine. However, the rotational speed N and pump supply flow rate Q of a hydraulic pump driven by an engine have characteristics as shown in FIG. That is, in the rotation speed region where the pump rotation speed does not reach the control flow rate, the rotation speed and the supply flow rate are proportional, and in the low rotation speed region, the pump supply flow rate sent to the hydraulic actuator is insufficient. If the steering wheel is steered at a rapid rotation speed when the hydraulic pump is rotating at low speeds, the hydraulic oil flow rate required for the hydraulic actuator in the steering section cannot be supplied from the hydraulic pump, and the steering angle does not increase as shown in Figure 3. However, a phenomenon in which the steering force increases (range A) occurs, and the driver feels that the steering force is abnormally large. On the other hand, a drive system for a hydraulic pump using an electric motor as the drive source is also known, but the electric motor is configured to rotate for the first time when the power I@ device requires pressure oil. While it is possible to avoid energy loss due to constant rotation, it takes time for the hydraulic pump to start rotating and reach a constant supply flow rate, and within this time, the disadvantage is that the steering force is large during sudden steering as mentioned above. It was happening. For this reason, in the drive system of a hydraulic pump that uses an mc electric motor as a drive source, in order to shorten the time required to reach a constant supply flow, the pump basic discharge 1 (discharge per 11 revolutions of the pump) is increased, However, all of these methods were not desirable measures as they were contrary to miniaturization, weight reduction, and energy saving.

[Problem that the invention seeks to solve]

To compensate for insufficient pump supply flow rate at the time of start-up of an electric motor for driving a hydraulic pump, and to eliminate the problem of large steering force even when a driver makes sudden steering.

[Means for solving problems]

An accumulator is installed in the oil circuit between the hydraulic pump and the hydraulic actuator in the steering section, and an appropriate number of pressure sensors or multiple pressure switches are installed in the circuit to detect the pressure in the circuit and generate an electric power source for driving the hydraulic pump. Control the motor with a controller.

[Effect]

The pressure in the oil circuit described above is detected by a pressure sensor or a pressure switch, and if a predetermined pressure drop is detected, the electric motor is driven and the pressure is stored in an accumulator in advance. This results in
Even if the driver makes a sudden steering operation, it is possible to compensate for the insufficient pump supply flow rate when the electric motor for driving the hydraulic pump starts up.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

The steering section 1 is composed of a switching valve 1a and a hydraulic actuator 1b, and the hydraulic actuator 1b is composed of a piston IC and a cylinder 1d. Hydraulic oil acting on the hydraulic actuator lb is supplied from a hydraulic pump 2, which is driven by an electric motor 3, and furthermore, a controller 8 rotates three electric motors only when necessary. A check valve 5 and an accumulator 4 are provided in the oil circuit between the hydraulic pump 2 and the steering section 10, and a pressure sensor 6.7 for detecting circuit pressure is installed in the circuit.
send an input signal to. As shown in Fig. 4, the pressure sensor 7 sends a signal to the controller 8 to stop the electric motor 3 when the relief set pressure is reached, and the pressure sensor 6 detects that the circuit is (pressure required for sudden steering + α) from kr/cd. The controller 8 starts the electric motor 3 when the
It sends a signal to Therefore, the accumulator 4 is always kept at a pressure between (pressure required for sudden steering +α) kf/- and the relief setting pressure. The controller 8 receives a vehicle speed signal, a rotational speed signal, a brake signal, and a steering signal as shown in Fig. 1 and Fig. 1-A. As shown in Figure 6, at time 1. The hydraulic pump starts operating at time t! The pump starts to rotate steadily, and steering starts at time t1, and the accumulator 4 can compensate for the lack of pump supply flow rate (shaded area B in FIG. 5) until the time required for the electric motor 3 to start rotating. That is, even if the switching valve 1a suddenly changes from the neutral position to the offset position during sudden steering,
One side chamber of the cylinder 1d and the accumulator 4 are connected,
The pressure oil accumulated in the accumulator 4 acts on one side chamber of the cylinder 1d, and the handle 9 can be operated lightly.

Similarly, in the above embodiment, the case where two pressure sensors 6.7 are provided is illustrated, but the pressure signal from a single pressure sensor may be processed by the controller, or the pressure signal may be processed in place of the pressure sensor. It is also possible to control the drive of the motor using two pressure switches.

〔Effect of the invention〕

According to the above-mentioned Toosho and the present invention, by storing 1 t of hydraulic oil and pressure f in the accumulator, 1 t of hydraulic oil is stored during sudden steering.
This can compensate for the lack of pump supply flow rate until the time required for the rotation of the motor to start up.
The discharge amount per rotation of the pump can be reduced, making it possible to downsize the pump. Moreover, since the pump is driven by an electric Tanabata system, the pump does not have to rotate all the time, resulting in energy savings.

Since the controller is used to start the pump rotation in advance using the engine speed, vehicle speed, etc. as a signal, the accumulator has to increase the amount of time it takes for the pump to reach steady rotation before the start of steering. Eliminates the need for expensive electric motors with short time constants.

[Brief explanation of drawings]

@ Figure 1 shows the oil circuit of the power steering device of the present invention.
Figure A shows a modification of Figure 1 of the signal input to the controller, Figure 2 is a diagram of the relationship between pump rotation speed and pump supply flow rate,
Fig. 3 is an explanatory diagram of abnormal steering force due to rotation speed steering when the pump supply flow rate is low, Fig. 4 shows the pressure range of the accumulator circuit of the present invention, and Fig. 5 is a diagram showing the pump rotation speed - supply flow rate characteristic diagram. An explanatory diagram showing a pump supply flow shortage range. FIG. 6 is a diagram showing the temporal relationship between the electric motor-driven hydraulic pump of the present invention and the steering force. l... Steering section, 2... Hydraulic pump, 3... Electric motor, 4... Accumulator, 6.7... Pressure sensor, 8... Controller, 9... Handle.

Claims (3)

[Claims] (1) A check valve and an accumulator are installed in the oil circuit between the steering section, which is composed of a switching valve and a hydraulic actuator, and a hydraulic pump driven by an electric motor, and the oil pressure in the oil circuit is adjusted to an appropriate pressure. It is characterized in that the detection signal is detected by a sensor or a plurality of pressure switches, and the detection signal is inputted to a controller together with a vehicle speed signal, an engine rotation speed signal, a brake signal, and a steering signal, and the controller performs operation start-stop control of the electric motor. Power steering device. (2) Some pressure switches or pressure sensors send a signal to control the controller to start the electric motor when the pressure in the oil circuit drops below (pressure required for sudden steering + α) kg/cm^2. 2. The power steering device according to claim 1, wherein (3) The power steering device according to claim 1, wherein the other pressure switch or pressure sensor sends a signal for controlling the electric motor to be stopped by the controller when the relief set pressure is reached. .