JP3711475B2 - Power steering device - Google Patents

Description

[0001]
BACKGROUND 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 specifically, the present invention relates to a power steering device with excellent responsiveness capable of obtaining power assist that responds immediately to the steering operation.
[0002]
[Prior art and problems to be solved by the invention]
Conventionally, as a power steering device, for example, the one described in Japanese Patent Publication No. 63-54590 has been generally 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, this power steering device is designed to rotate the oil pump by driving the electric motor only during the steering operation in order to reduce the amount of wear of the brush portion of the electric motor or to save energy of the entire system. When shifting from the non-operating time to the steering wheel operating time, there was a problem in that the oil pump discharge amount was insufficient at the initial start-up and the responsiveness was poor.
[0004]
Therefore, a power steering device aimed at improving the response is proposed in Japanese Utility Model Publication No. 1-18787. In this power steering device, the electric motor is driven at a low speed even when the steering wheel is not operated, and the rise of the discharge amount of the oil pump is accelerated by the pre-rotation of the electric motor when shifting to the steering wheel operation. Yes.
[0005]
However, in this power steering device, when the pressure in the circuit rises to a preset value, it is detected for the first time by the pressure switch, so that the transition from the time when the steering wheel is not operated (during standby) to the time when the steering wheel is operated is performed. Therefore, it still took some time from handle operation to pump activation. For this reason, there is a problem in that power assist corresponding to this cannot be obtained at the time of steering operation.
[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 capable of obtaining power assist in response to the steering operation. There is.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is 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 power steering valve 8 is assembled in a bridge circuit shape, and the power steering cylinder 9 is disposed on the Wheatstone bridge side of the power steering valve 8 assembled in a bridge circuit shape. 8 is detected by a detecting means 10 provided in series with the power steering cylinder 9 to detect a change in the flow rate of the pressure oil due to the operation of the power steering cylinder 9, and based on this detection signal, the rotation of the electric motor 7 is detected. The number of parameters is characterized by controlling the number. The Steering device 100 has its gist.
[0008]
The invention according to claim 2 is characterized in that the detection means 10 includes a diaphragm 10c and a differential pressure sensor 10b which is provided in parallel with the diaphragm 10c and detects a differential pressure before and after the diaphragm 10c. The power steering device 100 according to claim 1 is the gist thereof.
[0009]
The gist of the power steering device 100 according to claim 3 is that a pilot operation check valve 10d is provided in parallel with the throttle 10c.
[0010]
According to a fourth aspect of the present invention, in the power steering device 100 in which the oil pump 4 that supplies pressure oil to the power steering cylinder 9 via the power steering valve 8 is driven by the electric motor 7, On the other hand, the detecting means 10 provided in series with the power steering cylinder 9 detects a change in the flow rate of the pressure oil passing therethrough, and controls the rotational speed of the electric motor 7 based on this detection signal. The gist of the power steering apparatus 100 is characterized by the above.
According to a fourth aspect of the present invention, the detection means 10 includes a diaphragm 10c and a differential pressure sensor 10b that is provided in parallel with the diaphragm 10c and detects a differential pressure before and after the diaphragm 10c. The gist of the power steering device 100 is as follows.
Further, the gist of the invention of claim 4 is a power steering device 100 characterized in that a pilot operation check valve 10d is provided in parallel with the throttle 10c.
[0011]
The gist of the power steering apparatus 100 according to any one of claims 1 to 4, wherein the detecting means 10 is a flow rate sensor 10a.
[ 0012 ]
DETAILED DESCRIPTION OF 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 FIGS. 1 and 2, a steering gear box 3 (hereinafter referred to as a gear box 3) having a power steering cylinder 9 (hereinafter referred to as a PS cylinder 9) and a steering gear incorporated therein is provided at the tip of the input shaft 2 of the handle 1. ) Are connected. The input shaft 2 is coupled to the PS cylinder 9 via a torsion bar, a ball screw, etc., and simultaneously linked to a power steering valve 8 (hereinafter referred to as a PS valve 8), and the PS valve 8 is switched according to the rotation direction of the handle 1. It is designed to operate.
[ 0013 ]
An oil pump 4 that supplies pressure oil to the PS cylinder 9 built in the gear box 3 is disposed at a predetermined position in the engine room. The high hydraulic pressure generated in the oil pump 4 is sent to the PS cylinder 9 via the high pressure hose 5A, and the return oil is returned to the oil tank 6 of the oil pump 4 via the low pressure hose 5B. .
[ 0014 ]
The oil pump 4 is a vane pump. An electric motor 7 is coaxially coupled to the pump shaft, and the oil pump 4 is driven by the 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 the engine room or the vehicle compartment, and the oil pump 4 can obtain optimum power assist according to the driving state of the vehicle or the like. The number of rotations is variably controlled.
[ 0015 ]
The ECU receives a detection signal from a detection means 10 to be described later, and also receives an engine speed signal from a distributor of the engine body, a vehicle speed signal and a load signal from a transmission unit, and the like. In the ECU, these input signals are appropriately converted into current values or voltage values, compared with each other, and then output to the electric motor 7 as a control current or control voltage, which is variably rotated.
[ 0016 ]
Detection means 10, which form a feature of the present invention is provided in series with the power steering cylinder 9 to the front Symbol power steering valve 8, the flow rate fluctuation of the pressure oil by the operation of the PS cylinder 9 It comes to detect. For example, when the flow sensor 10a is used as the detecting means 10 as in the first embodiment shown in FIG. 1, the PS cylinder 9 is operated by operating the handle 1 and a displacement occurs in the PS cylinder 9 immediately. The flow rate from 8 to the PS cylinder 9 varies. In particular, when the handle 1 is suddenly operated, a large flow rate difference occurs in a very short time. The power steering according to the present invention is such that the flow rate fluctuation caused by the operation of the PS cylinder 9 is detected by the flow rate sensor 10a (detection means 10), and the rotational speed of the electric motor 7 is controlled based on this detection signal. The device 100. Since these occur almost simultaneously with the steering of the steering wheel 1, the responsiveness can be remarkably improved as compared with the conventional example in which the pump is not started unless the pressure in the circuit rises to a preset pressure.
[ 0017 ]
The detection means 10 is the flow rate sensor 10a in the case of the first embodiment, but a combination of a throttle 10c and a differential pressure sensor 10b provided in parallel thereto as in the second or third embodiment described later. The configuration is not particularly limited as long as the flow rate variation of the pressure oil between the PS valve 8 and the PS cylinder 9 can be detected immediately.
[ 0018 ]
Next, the operation of the power steering apparatus 100 configured as described above will be described. Note that in FIG. 5 (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 apparatus 100, the rotation speed of the electric motor 7 when the handle is not operated is indicated by a dotted line in FIG. The number of rotations of the electric motor 7 when operating the handle is shown by a solid line in FIG.
[ 0019 ]
First, the operation when the handle 1 is not operated will be described. As shown in FIG. 1, the electric motor 7 starts when the engine starts. At that time, as shown in FIG. 5, the electric motor 7 rotates at an arbitrarily set number of rotations, for example, 300 rotations. That is, the oil supplied from the oil pump 4 returns to the oil tank 6 via the PS valve 8, but at this time there is no change in the flow rate passing through the flow rate sensor 10a (no flow of pressure oil), so the ECU Controls the electric motor 7 to rotate at a preset number of rotations.
[ 0020 ]
Next, as shown in FIGS. 1 and 2, the oil pump 4 that is rotationally driven by the electric motor 7 sends the required amount of pressure oil to the PS cylinder 9 via the high-pressure hose 5 </ b> A. The return oil is returned to the oil tank 6 of the oil pump 4 through the low pressure hose 5B.
[ 0021 ]
Until the vehicle speed reaches an arbitrarily set speed, for example, 60 km / h, the electric motor 7 continues to rotate at the set 300 rpm. When the vehicle speed exceeds 60 km / h, the ECU controls the speed of the electric motor 7 to gradually decrease in proportion to the vehicle speed based on the signal from the vehicle speed sensor that detects this. Further, when the vehicle speed exceeds an arbitrarily set speed, for example, 100 km / h, the ECU is operated by a signal from the vehicle speed sensor that detects this, and the rotation of the electric motor 7 is stopped.
[ 0022 ]
Next, the operation of the handle 1 will be described. When the handle 1 is operated, the PS cylinder 9 is activated, and accordingly, the flow rate of the pressure oil flowing between the PS valve 8 and the PS cylinder 9 is changed.
[ 0023 ]
This variation is detected by the flow sensor 10a, and the detection signal is input to the ECU. Based on the detection signal from the flow sensor 10a, the ECU increases the number of rotations of the electric motor 7 to a higher number of rotations than when not operated, for example, 3000 rotations. As a result, power assist by pressure oil is performed on the handle 1, and the handle 1 can be easily steered. Thereafter, when the flow rate sensor 10a detects that the handle operation is finished and the flow rate fluctuation is eliminated, the ECU controls the electric motor 7 to reduce the rotation speed from 3000 to 300 rotations.
[ 0024 ]
FIG. 3 is a system diagram showing Embodiment 2 according to the third aspect of the present invention. As the detecting means 10, a throttle 10c provided between the PS valve 8 and the PS cylinder 9 and a parallel arrangement to the throttle 10c are provided. It comprises a differential pressure sensor 10b. In the case of this embodiment, when a flow of pressure oil occurs in the throttle 10c, a pressure difference is generated before and after the throttle 10c. This pressure difference is detected by the differential pressure sensor 10b, and the detection signal is transmitted to the ECU. The ECU increases the rotational speed of the electric motor 7 to a higher rotational speed than when it is not operated.
[ 0025 ]
The throttle area of the throttle 10c needs to be determined so that the pressure loss does not increase as much as possible even when the supply flow rate from the oil pump 4 is maximum, but it is parallel to the throttle 10c as shown in FIG. If the pilot actuated check valve 10d is provided in the valve, the pressure loss can be reduced.
[ 0026 ]
That is, when pressure oil flows from the PS valve 8 into the PS cylinder 9 via the passage A in FIG. 4, when the pressure is low, it flows into the PS cylinder 9 only through the throttle 10c, and the pressure rises. When the pilot pressure of the pilot operation check valve 10d is exceeded, the pilot operation check valve 10d opens and the pressure oil flows into the PS cylinder 9 via both the throttle 10c and the pilot operation check valve 10d. Therefore, the pressure loss when the maximum supply flow rate to the vehicle passes through the throttle (during steering) can be reduced.
[0027]
On the other hand, when pressure oil flows from the PS valve 8 into the PS cylinder 9 via the passage B in FIG. 4, the return oil from the PS cylinder 9 passes through both the throttle 10c and the pilot operation check valve 10d. Then, it returns to the oil tank 6. Note that the cracking pressure of the pilot operation check valve 10d is set as low as possible to reduce the pressure loss.
[0028]
【The invention's effect】
In the power steering device of the present invention, the fluctuation of the flow rate due to the operation of the PS cylinder is detected by a detecting means such as a flow rate sensor, and the rotational speed of the electric motor is controlled based on this detection signal. The transition from the non-operating time to the steering wheel operation can be detected instantly, and power assist corresponding to this can be obtained at the time of the steering wheel operation.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of a power steering apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of a power steering apparatus according to the present invention.
FIG. 3 is a system configuration diagram of a power steering apparatus according to an embodiment of the present invention;
FIG. 4 is a system configuration diagram of a power steering apparatus according to an embodiment of the present invention;
FIG. 5 is a graph showing the relationship between the vehicle speed and the rotation speed of the 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 cylinder 10... Detection means 10a .. flow sensor 10b .. differential pressure sensor 10c .. throttle 10d.

Claims (5)

In a power steering apparatus 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 power steering valve is assembled in a bridge circuit shape,
The power steering cylinder is disposed on the Wheatstone bridge side of the power steering valve assembled in the bridge circuit shape,
By detecting means provided before Symbol power steering cylinder series, and detects the flow rate fluctuation of the pressure oil by the operation of the power steering cylinder, and to control the rotational speed of the electric motor based on the detection signal A power steering device characterized by that.   2. The power steering apparatus according to claim 1, wherein the detecting means comprises a throttle and a differential pressure sensor that is provided in parallel with the throttle and detects a differential pressure before and after the throttle. The power steering apparatus according to claim 2, wherein a pilot operation check valve is provided in parallel with the throttle. In a power steering apparatus 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 detecting means provided in series with the power steering cylinder with respect to the power steering valve detects fluctuations in the flow rate of the pressure oil passing between them, and controls the rotation speed of the electric motor based on this detection signal. And
The detection means comprises a throttle and a differential pressure sensor that is provided in parallel with the throttle and detects a differential pressure before and after the throttle;
A power steering apparatus, wherein a pilot operation check valve is provided in parallel with the throttle.   The power steering apparatus according to any one of claims 1 to 4, wherein the detection means is a flow sensor.

Images