JP3600877B2 - Power steering device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power steering apparatus in which an oil pump that supplies pressure oil to a power steering cylinder is driven by an electric motor. More particularly, the present invention relates to a power steering device with excellent responsiveness, which can obtain power assist corresponding to the steering operation at the time of steering operation.
[0002]
Problems to be solved by the prior art and the invention
Conventionally, as a power steering device, for example, a device described in Japanese Patent Publication No. 63-54590 has been widely used. In this power steering device, an oil pump that supplies pressure oil to a power steering cylinder built in a steering gear box is driven by an electric motor.
[0003]
However, in this power steering device, the electric motor is driven only when the steering wheel is operated to rotate the oil pump in order to reduce the wear amount of the brush portion of the electric motor or to save energy of the entire system. When shifting from non-operation to steering operation, there is a problem that the discharge amount of the oil pump is insufficient in the initial stage of the start and the response is poor.
[0004]
Therefore, a power steering apparatus for improving the response is proposed in Japanese Utility Model Publication No. 1-115787. In this power steering device, the electric motor is driven at a low rotation even when the steering wheel is not operated, so that the rise in the discharge amount of the oil pump is advanced by the pre-rotation of the electric motor when shifting to the steering wheel operation. I have.
[0005]
However, in this power steering device, when the pressure in the circuit rises to a preset value, the pressure switch detects the pressure for the first time, so that the shift from the non-operation of the steering wheel (standby) to the operation of the steering wheel. Therefore, it takes some time from the operation of the steering wheel to the activation of the pump. For this reason, at the time of operating the steering wheel, there is a problem that power assist corresponding to this operation cannot be obtained.
[0006]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a power steering device with excellent responsiveness that can obtain power assist corresponding to the steering wheel operation at the time of operation. .
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention relates to a power steering apparatus 100 in which an oil pump 4 for supplying pressure oil to a power steering cylinder 9 via a power steering valve 8 is driven by an electric motor 7. The flow rate difference between the two is detected by flow rate sensors 10a and 10b provided between the power steering valve 4 and the power steering valve and between the power steering cylinder 9 and the oil tank 6, and the rotation speed of the electric motor 7 is controlled based on the detection signal. The gist of the present invention is a power steering device 100 characterized by performing the above operation.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of a power steering device 100 (hereinafter, referred to as a PS device 100) of the present invention will be described with reference to the drawings.
As shown in FIG. 2, a power steering cylinder 9 (hereinafter, referred to as PS cylinder 9) and a steering gear box 3 (hereinafter, referred to as gear box 3) having a built-in steering gear are connected to the tip of the input shaft 2 of the handle 1. Have been. The input shaft 2 is connected to a PS cylinder 9 via a torsion bar, a ball screw, and the like, and at the same time, is linked to a power steering valve 8 (hereinafter, referred to as a PS valve 8), and switches the PS valve 8 according to the rotation direction of the handle 1. It is designed to work.
[0009]
An oil pump 4 for supplying pressure oil to a PS cylinder 9 built in the gear box 3 is arranged at a predetermined position in an engine room.
Then, the high oil pressure generated by the oil pump 4 is sent to the PS cylinder via the high pressure hose 5A, and the returned oil is returned to the oil tank 6 of the oil pump 4 via the low pressure hose 5B.
[0010]
The oil pump 4 is a vane pump, and an electric motor 7 is coaxially coupled to the pump shaft, and the oil pump 4 is driven by rotation of the electric motor 7.
The electric motor 7 is driven and controlled by an output signal from a control circuit (ECU) disposed in an engine room or a vehicle interior, and an oil pump 4 is provided so that an optimal power assist can be obtained according to a driving state of a vehicle or the like. Is variably controlled.
[0011]
The ECU receives detection signals from flow sensors 10a and 10b, which will be described later, and also receives an engine speed signal from a power distribution unit of the engine body, a vehicle speed signal and a load signal from a transmission unit, and the like. The ECU converts these input signals into current values or voltage values as appropriate, compares them, and then outputs them to the electric motor 7 as a control current or control voltage to variably rotate them.
[0012]
The flow rate sensors 10a and 10b are features of the present invention, and are provided between the oil pump 4 and the PS valve 8 and between the PS cylinder 9 and the oil tank 6, respectively. Is detected.
[0013]
As shown in FIG. 2, the PS cylinder 9 is operated by operating the handle 1, and when this is displaced, the flow from the oil pump 4 to the PS valve 8 and the flow from the PS cylinder 9 to the oil tank 6 There will be a difference between this and the flow rate. In particular, when the steering wheel 1 is suddenly operated, the amount of oil flowing out of the PS cylinder 9 is larger than that of oil flowing into the PS cylinder 9, and the flow rate between the two flow rate sensors 10a and 10b is extremely short. A difference will occur. The difference between the flow rates due to the operation of the PS cylinder 9 is detected by the two flow rate sensors 10a and 10b, and the rotation speed of the electric motor 7 is controlled based on the detection signals. That's it.
[0014]
Since this flow rate difference occurs almost simultaneously with the steering of the steering wheel 1, the responsiveness is significantly improved as compared with the conventional example in which the pump is not started unless the pressure in the circuit rises to a predetermined pressure. Can be.
[0015]
In this embodiment, the flow sensors 10a and 10b are provided in the gear box 3 in this embodiment. In addition, when the steering operation is slow, that is, when the steering is slow, a difference in flow rate between the two flow rate sensors 10a and 10b is difficult to appear. Is not always necessary.
[0016]
Next, the operation of the power steering device 100 configured as described above will be described. In FIG. 3 (a graph showing the relationship between the vehicle speed and the rotation speed of the electric motor 7) used in the description of the operation of the power steering device 100, the rotation speed of the electric motor 7 when the steering wheel is not operated is indicated by a dotted line in FIG. The rotation speed of the electric motor 7 at the time of operating the steering wheel is shown by a solid line in FIG.
[0017]
First, the case where the steering wheel is not operated will be described. As shown in FIG. 1, the electric motor 7 starts with the start of the engine. As shown in FIG. 3, the electric motor 7 rotates at an arbitrarily set rotation speed, for example, about 300 rotations.
[0018]
Next, as shown in FIGS. 1 and 2, the oil pump 4 driven to rotate by the electric motor 7 sends a required amount of pressure oil to the PS cylinder 9 via the high-pressure hose 5A. The return oil is returned to the oil tank 6 of the oil pump 4 via the low pressure hose 5B.
That is, the oil supplied from the oil pump returns to the oil tank 6 via the flow rate sensor 10a, the PS valve 8, and the flow rate sensor 10b. At this time, the flow rates passing through the two flow rate sensors 10a, 10b are the same. Therefore, the ECU controls the electric motor 7 to rotate at a preset rotation speed.
[0019]
Until the vehicle speed reaches an arbitrarily set speed, for example, 60 km / h, the electric motor 7 keeps rotating at the set 300 rpm. When the vehicle speed exceeds 60 km / h, the ECU controls the rotational speed of the electric motor 7 to gradually decrease in proportion to the vehicle speed based on a signal from the vehicle speed sensor that detects the speed.
[0020]
Further, when the vehicle speed exceeds an arbitrarily set speed, for example, 100 km / h, the ECU operates with a signal from the vehicle speed sensor that detects the speed, and stops the rotation of the electric motor 7.
[0021]
Next, the operation at the time of operating the steering wheel will be described. The PS cylinder 9 is operated by operating the handle 1, and a flow difference immediately occurs between the oil pump 4 and the PS valve 8 and between the PS cylinder 9 and the oil tank 6.
[0022]
This flow difference is detected by the two flow sensors 10a and 10b, and the detection signal is input to the ECU. The ECU increases the rotation speed of the electric motor 7 to a higher rotation speed than when it is not operated, for example, 3000 rotations, based on the detection signals from the flow rate sensors 10a and 10b. As a result, the steering wheel 1 is subjected to power assist by pressure oil, and the steering wheel 1 can be easily steered.
[0023]
Thereafter, when the pressure switch 11 detects that the operation of the steering wheel has been completed and the inside of the circuit has reached a predetermined pressure, or detects that the flow rate difference between the two flow rate sensors 10a and 10b has disappeared, the ECU sets the electric motor 7 Is controlled to decrease the number of rotations of the above from 3000 rotations to 300 rotations.
[0024]
【The invention's effect】
In the power steering apparatus of the present invention, the flow rate difference caused by the operation of the PS cylinder is detected by the two flow rate sensors, and the rotation speed of the electric motor is controlled based on the detection signals. The transition from the time to the time of steering operation can be instantaneously sensed, and the power assist corresponding to this at the time of steering wheel operation can be obtained.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of a power steering device according to the present invention.
FIG. 2 is a schematic configuration diagram of a power steering device of the present invention.
FIG. 3 is a graph showing a relationship between a vehicle speed and a rotation speed of an electric motor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Handle 2 ... Input shaft 3 ... Gear box 4 ... Oil pump 5 ... Hose 6 ... Oil tank 7 ... Electric motor 8 ... PS valve 9 ... PS cylinders 10a, 10b Flow sensor 11 Pressure switch 100 Power steering device

Claims (1)

In a power steering device in which an oil pump that supplies pressure oil to a power steering cylinder via a power steering valve is driven by an electric motor,
The flow rate difference between the oil pump and the power steering valve and between the power steering cylinder and the oil tank is detected by a flow rate sensor provided between the oil pump and the power steering valve, and the rotation speed of the electric motor is controlled based on the detection signal. A power steering device, comprising:

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