JP2005231412A - Power steering system - Google Patents

Abstract

An object of the present invention is to provide a power steering system capable of generating an appropriate assist force in accordance with the rotational position of a knob.
When a steering wheel is rotated, a control unit adjusts the opening of a priority valve in accordance with the rotational position of a knob detected by a rotational position sensor, whereby the flow rate of hydraulic oil supplied to a power steering cylinder is determined. To change the magnitude of the assist force. As a result, an appropriate assisting force according to the rotation position of the knob is exhibited, and the rotation operation of the steering wheel by the operator's knob is appropriately assisted.
[Selection] Figure 3

Description

  The present invention relates to a power steering system.

  For example, Patent Document 1 discloses a power steering system in which an assist force is increased when a load pressure of a power cylinder exceeds a predetermined value during operation of a steering wheel.

JP 11-115785 A

  By the way, in an industrial vehicle such as a forklift, there is a type in which a knob is fixed to a steering wheel, and a user rotates the steering wheel with the knob. Such a steering wheel with a knob has a position that is easy for the user to operate depending on the rotation position of the knob, and a position that is difficult for the user to operate.Therefore, the magnitude of the assist force is changed appropriately according to the rotation position of the knob. It is desirable to generate a strong assist force.

However, since the power steering system of Patent Document 1 is configured to increase and maintain the assist force to a predetermined value when the load pressure of the power cylinder exceeds a predetermined value, An appropriate assist force cannot be exhibited by changing the magnitude of the assist force in accordance with the rotational position of the knob.
The present invention has been made to solve such a problem, and an object thereof is to provide a power steering system capable of generating an appropriate assist force in accordance with the rotational position of the knob.

  A power steering system according to the present invention is fixed to a steering wheel of a vehicle and rotates a steering wheel, a rotational position sensor for detecting the rotational position of the knob, and rotation of the steering wheel by the knob. Assist means for generating assist force during operation and assisting its rotation, and a controller for adjusting the magnitude of the assist force by the assist means according to the rotational position of the knob detected by the rotational position sensor.

  When rotating the steering wheel, the control unit changes the magnitude of the assisting force by the assisting means in accordance with the rotational position of the knob detected by the rotational position sensor. Assist power is demonstrated.

  According to the present invention, the magnitude of the assisting force by the assist means is adjusted according to the rotational position of the knob detected by the rotational position sensor when the steering wheel is rotated by the knob. Appropriate assist force can be generated.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 shows an overall configuration of a power steering system according to Embodiment 1 of the present invention. This system is applied to a forklift and has a steering wheel 1 for steering a wheel (not shown). A knob 2 is attached to the surface of the wheel 1, and an operator can rotate the steering wheel 1 with the knob 2. A steering shaft 3 is connected to the lower center portion of the steering wheel 1. The steering shaft 3 is rotatably held by a steering post 4 and its lower end is connected to a steering valve 5. Further, a rotational position sensor 6 for detecting the rotational position of the knob 2 is attached to the steering shaft 3.

  The steering valve 5 is connected to a power steering cylinder 9 via a first pipe 7 and a second pipe 8, and the steering valve 5 is connected to the steering valve 5 via the first pipe 7 and the second pipe 8. Inflow and discharge of hydraulic oil are performed between the left chamber 9a and the right chamber 9b of the power steering cylinder 9. Further, a piston 9c connected to a wheel steering device (not shown) is movably disposed in the power steering cylinder 9, and when the steering wheel 1 is rotated, the hydraulic oil in the left chamber 9a and the right chamber 9b The piston 9c is moved leftward or rightward in the power steering cylinder 9 by the pressure difference to generate assist force, thereby assisting the steering of the wheel, that is, assisting the rotation operation of the steering wheel 1 by the knob 2. It has become.

  A hydraulic pump 12 is connected to the steering valve 5 via a steering pipe 10 and a priority valve 11. A hydraulic oil tank 13 is connected to the hydraulic pump 12, and when the motor 12 a of the hydraulic pump 12 is operated, the hydraulic oil stored in the hydraulic oil tank 13 is discharged to the priority valve 11 by the hydraulic pump 12. It is configured as follows. The hydraulic oil tank 13 and the steering valve 5 are connected to each other by a discharge pipe 14. Furthermore, the control part 15 is electrically connected to the rotational position sensor 6, the priority valve 11, and the motor 12a of the hydraulic pump 12, respectively. The steering valve 5, the first and second pipes 7 and 8, the power steering cylinder 9, the steering pipe 10, the priority valve 11, the hydraulic pump 12 and its motor 12a, the hydraulic oil tank 13, and the discharge pipe 14 The assist means of the present invention is configured.

  Here, the priority valve 11 has a structure capable of adjusting the opening, and an electric signal is sent from the control unit 15 to the priority valve 11 to adjust the opening of the valve 11 to be supplied to the steering pipe 10. It is possible to control the flow rate of the hydraulic oil. That is, it is possible to control the flow rate of the hydraulic oil supplied from the hydraulic pump 12 to the power steering cylinder 9 via the steering pipe 10 and the steering valve 5 when the steering wheel 1 is rotated. Can be adjusted.

Here, when the operator rotates the steering wheel 1 with the knob 2, there are a position that is easy to operate and a position that is difficult to operate depending on the rotational position of the knob 2. As shown in FIG. 2, in general, a force F1 for pushing and pulling the knob 2 in the front-rear direction is easy to produce, and conversely, a force F2 for moving the knob 2 in the left-right direction is difficult to produce. Therefore, when the rotational position of the knob 2 as shown by the solid line in FIG. 2 is set as the origin position O, the magnitude of the rotational force by the operator depends on the rotational position of the knob 2 as shown by the broken line in FIG. Will change periodically. Therefore, it is preferable to generate an assist force having such a magnitude as to make up the force Fo required in the rotation direction by compensating the rotation force by the operator. For example, when the rotational force by the operator is Fmin, an assist force of Fmax is desired, and when the rotational force by the operator is Fmax, an assist force of Fmin is desired.
Therefore, in the power steering system of the present invention, the control unit 15 adjusts the opening degree of the priority valve 11 according to the rotational position of the knob 2 detected by the rotational position sensor 6 when the steering wheel 1 is rotated, so that the knob The assist force that changes as shown by the solid line in FIG.

  Next, the operation of the power steering system according to Embodiment 1 of the present invention will be described. When the steering wheel 1 is rotated to the right by the knob 2, the steering pipe 5 communicates with the steering pipe 10 and the first pipe 7, and the discharge pipe 14 and the second pipe 8. As a result, the motor 12 a of the hydraulic pump 12 is driven, and the hydraulic oil in the hydraulic oil tank 13 is supplied to the steering valve 5 via the hydraulic pump 12, the priority valve 11 and the steering pipe 10. Further, the hydraulic oil is supplied to the left chamber 9a of the power steering cylinder 9 through the first pipe 7, and the hydraulic oil in the right chamber 9b of the cylinder 9 is supplied to the second pipe 8, the steering valve 5 and the discharge valve. The oil is discharged to the hydraulic oil tank 13 through the pipe 14. As a result, the piston 9c moves to the right in the power steering cylinder 9 to assist the steering of the wheel in the right direction.

  On the other hand, when the steering wheel 1 is rotated to the left by the knob 2, the steering pipe 10 and the second pipe 8, and the discharge pipe 14 and the first pipe 7 are communicated by the steering valve 5. The motor 12 a of the hydraulic pump 12 is driven by the section 15, and the hydraulic oil in the hydraulic oil tank 13 is supplied to the steering valve 5 via the hydraulic pump 12, the priority valve 11 and the steering pipe 10. Further, the hydraulic oil is supplied to the right chamber 9b of the power steering cylinder 9 via the second pipe 8, and the hydraulic oil in the left chamber 9a of the cylinder 9 is supplied to the first pipe 7, the steering valve 5 and the discharge valve. The oil is discharged to the hydraulic oil tank 13 through the pipe 14. As a result, the piston 9c moves to the left in the power steering cylinder 9, and the steering of the wheel in the left direction is assisted.

  When the steering wheel 1 is rotated, the control unit 15 adjusts the opening degree of the priority valve 11 according to the rotational position of the knob 2 detected by the rotational position sensor 6, thereby supplying the power steering cylinder 9. By controlling the flow rate of the hydraulic oil, an assist force as shown by a solid line in FIG. 3 is generated. As a result, an appropriate assisting force according to the rotational position of the knob 2 is exerted, the rotational operation of the steering wheel 1 by the knob 2 is appropriately assisted, and the operator can easily rotate the steering wheel 1 by the knob 2. it can. Therefore, it is possible to reduce the operator's fatigue when the steering wheel 1 is rotated by the knob 2 for a long time.

  A cargo handling pipe (not shown) is connected to the priority valve 11, and when the steering wheel 1 is rotated, the steering pipe 10 is selected by the priority valve 11 and the hydraulic oil discharged from the hydraulic pump 12 is steered. However, when the cargo handling lever or the cargo handling sensor is activated when the steering wheel 1 is not rotated, the cargo handling pipe is selected and hydraulic oil is supplied to the cargo handling pipe. The cargo handling equipment such as is driven.

Embodiment 2. FIG.
In the first embodiment, the flow rate of the hydraulic oil supplied to the power steering cylinder 9 is controlled by adjusting the opening degree of the priority valve 11 by the control unit 15, but instead, FIG. As shown in FIG. 4, the steering valve 10 is selected by the priority valve 11 when the steering wheel 1 is rotated, and the control unit 15 controls the rotational speed of the motor 12a of the hydraulic pump 12 to the power steering cylinder 9. It is also possible to control the flow rate of the supplied hydraulic oil so as to adjust the magnitude of the assist force.

Embodiment 3 FIG.
In addition, as shown in FIG. 5, it is possible to configure as a dedicated hydraulic circuit for supplying hydraulic oil to the power steering cylinder 9 without providing the priority valve 11. By controlling the rotational speed of the motor 12a of the pump 12, the flow rate of the hydraulic oil supplied to the power steering cylinder 9 can be controlled to adjust the magnitude of the assist force.

  In addition, instead of adjusting the opening degree of the priority valve 11 or controlling the rotation speed of the motor 12a of the hydraulic pump 12 as in the first to third embodiments, the opening degree can be adjusted as the steering valve 5. You may make it control the flow volume of the hydraulic fluid supplied to the power steering cylinder 9 by this steering valve 5 using a valve.

  Further, the power steering system of the present invention can be applied to both an engine vehicle and a battery vehicle. For example, in the case of a battery vehicle, an assist force is applied instead of providing a hydraulic circuit as in the above-described embodiment. An electric power steering device (EPS) may be provided as the assisting means, and the control unit 15 may adjust the magnitude of the assisting force by the power steering device according to the rotational position of the knob 2.

In the above-described embodiment, as shown by the solid line in FIG. 3, the assist force is continuously changed. However, the assist force may be changed stepwise according to the rotational position of the knob 2. .
The power steering system of the present invention can be applied to both counter type and reach type forklifts. Moreover, if it has a steering wheel rotated by a knob, it can be applied not only to forklifts but also to order pickers and other work vehicles.

It is a schematic diagram which shows the power steering system which concerns on Embodiment 1 of this invention. It is a figure which shows the mode of the force applied to a knob when rotating a steering wheel by a knob. 6 is a diagram illustrating a relationship between a rotational force and an assist force by an operator according to Embodiment 1. FIG. It is a schematic diagram which shows the power steering system which concerns on Embodiment 2 of this invention. It is a schematic diagram which shows the power steering system which concerns on Embodiment 3 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Steering wheel, 2 Knob, 3 Steering shaft, 4 Steering post, 5 Steering valve, 6 Rotation position sensor, 7 1st piping, 8 2nd piping, 9 Power steering cylinder, 9a Left chamber, 9b Right chamber, 10 Steering piping, 11 priority valve, 12 hydraulic pump, 12a motor, 13 hydraulic oil tank, 14 discharge piping, 15 control unit.

Claims (1)

A knob for rotating the steering wheel while being fixed to the steering wheel of the vehicle;
A rotational position sensor for detecting the rotational position of the knob;
Assist means for assisting the rotation by generating an assist force when the steering wheel is rotated by the knob;
A power steering system comprising: a control unit that adjusts the magnitude of the assist force by the assist means in accordance with the rotation position of the knob detected by the rotation position sensor.

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