JPS63255177A - Flow rate control device for power steering device in cargo working vehicle - Google Patents

Abstract

PURPOSE:To keep a steering force constant irrespective of the magnitude of a load by detecting a load applied to a steering wheel, reading the optimum flow rate of a control valve suited to said detected load and controlling a flow rate controlling means provided on the upper course side of said control valve. CONSTITUTION:The power steering device of a fork lift controls its rear wheel 7 as a steering wheel by feeding a working fluid from a hydraulic pump 10 to a power cylinder 9 via a flow divider 12 and a control valve 14. In this case, a pressure sensor 23 for detecting the pressure of a tilt cylinder 22 which is varied in accordance with a variable load is provided. Also, a variable flow rate regulating valve 19 for controlling the feeding flow rate of the working fluid to the control valve 14 is provided. And, by reading the optimum flow rate of the control valve corresponding to the detected variable load from a memory device 28 by a CPU 29, its control signal is outputted to a stepping motor 20 to control the opening of the variable flow rate regulating valve 19.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a power steering Vta in a cargo handling vehicle such as a forklift, and more particularly to flow rate control of hydraulic oil supplied to a power cylinder.

(Conventional technology) Conventional hydraulic power steering devices used in forklifts use hydraulic fluid from a hydraulic pump driven by an engine (or an electric motor in Battery City) to be connected to the power steering system and cargo handling using a flow divider. Generally, the rear wheels, which serve as steering wheels, are steered by dividing the hydraulic fluid into the power steering system and supplying the hydraulic oil sent to the power steering system to the power cylinder through a control valve operated by the steering wheel. This type of power steering device is disclosed, for example, in Japanese Utility Model Publication No. 52-57563. Furthermore, in the invention disclosed in this publication, when loading cargo, the steering is switched to manual mode by cutting off the hydraulic oil supply circuit to the power cylinder.

(Problems to be Solved by the Invention) However, in the case of conventional power steering devices, there is a problem in that the steering force becomes too light when loading luggage. In other words, when the fork is unloaded, a large load is applied to the rear wheel, which is the steering wheel, but when the fork is loaded with cargo, the rear wheel load decreases, so the steering force is less than when the fork is unloaded. It becomes lighter.

Such changes in steering force impede safe driving and are also a cause of fatigue of the A-pelleter. Note that the above publication discloses a technology for switching the steering to manual mode when loading cargo, but such a switching method destroys the characteristics of power steering and makes it difficult to obtain an appropriate steering force. Have difficulty.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a flow ω control device for a power steering device in a cargo handling vehicle that can maintain a constant steering force regardless of whether cargo is loaded or not.

(Means for Solving the Problems) The present invention for solving the above problems supplies hydraulic oil from a hydraulic pump to a power cylinder through a flow divider and a control valve for power steering, so that the steering wheel can be used as a steering wheel. In a power steering device that steers a rear wheel, a load sensor that detects the load applied to the rear wheel, a storage device that stores the relationship between the rear wheel load and the optimum flow rate of the control valve as data, and a load sensor that detects the load applied to the rear wheel. Nυ
a flow rate determining means for determining a supply flow rate suitable for the rear wheel load on the control valve based on the detected load by the controller and the data in the storage device; The gist is that the flow control device 611 of the power steering device is configured by a flow rate control means that controls the flow rate supplied to the control valve based on an instruction from the means.

(Function) In the empty fiTe1, the flow rate determining means that processes the data sent from the load sensor instructs the flow rate i+l control means to make the supply flow rate to the control valve the maximum within the set range. Therefore, at this time, the flow rate of hydraulic oil controlled by the divider is sent to the control valve.

When loading cargo, the load sensor is 8! When a loaded insect is detected, the flow rate determining means calculates the flow rate corresponding to the detected value from the load sensor based on the data in the storage device, and instructs the flow rate control means to reduce the flow rate. Therefore, at this time, the flow rate of the operating oil supplied to the control valve is reduced, and the followability of the steering operation is reduced in accordance with the extent of the reduction h1, and weight is added to the steering wheel.

(Example) Hereinafter, an example of the present invention will be specifically described based on the drawings. First, the mechanical configuration of the power steering device will be briefly explained based on FIG. 2. In the diagram, 1 is the steering wheel, 2 is the steering post, and 3 is the steering post 2.
ZM for rotation of the steering shaft (not shown) inside
I, the pitman arm that swings, 4 is a drag link, one end of which is connected to the pitman arm 3, and the other end of which is connected to the bell crank 5. 6 is a left and right tie rod, -at is connected to the bell crank 5, and the other end is connected to a rear wheel 7, which is a steering wheel, via a knuckle 8. 9 is a power cylinder, one end of which is connected to the gap side, and the other end of which is connected to the bell crank 6.

Next, the hydraulic circuit and flow control means of the power steering device will be explained based on FIG.

10 in the diagram is the engine (in the case of a battery car, it is the electric motor)
A hydraulic pump 11 is driven, and a flow divider 12 divides the hydraulic oil sent from the hydraulic pump 10 into the power steering system and the cargo handling system, and always supplies a constant amount of hydraulic oil to the power steering system. The remaining surplus oil will be supplied to the cargo handling system.

13 is a supply pipe that sends the hydraulic oil divided by the flow divider 12 to the power steering control valve 14 operated by the handle 1; 15 is a return pipe that connects the control valve 14 and the tank 16; 17
is a hydraulic pipe line connecting the control valve 14 and the power cylinder 9. 18 is a flow rate control means for controlling the flow rate of hydraulic oil supplied to the control valve 14;
It is provided in the supply pipe line 13. Flow rate control means 18
Specifically, it consists of a variable flow rate adjustment valve 19 and a stepping motor 20 that adjusts the opening degree of this variable flow rate adjustment valve 19, and a load sensor that detects the load (including its own weight) of the fork 21 is used to adjust the degree of opening of the variable flow rate adjustment valve 19. More specifically, it is controlled by an instruction from a control circuit 26 based on a detection signal from a pressure sensor 23 that detects the pressure (holding pressure) of the tilt cylinder 22 that changes depending on the loaded load. Note that the pressure sensor 23 may be installed in the control side pipe of the hydraulic pipe 25 that connects the tilt cylinder 22 and the cargo handling control valve 24.

The control circuit 26 includes an input interface 27 including an A/D converter, a storage device 28, and a CPU 2 as a diversion determining means.
9. Consists of an output interface 30 including a drive circuit for the step motor, and a storage device 28 that stores the relationship between the holding pressure of the tilt cylinder 22 and the rear wheel load, and the relationship between the rear wheel load and the optimum flow rate of the control valve. stored as data. That is, the memory device ff128 stores the UAM flow value of the control valve 14 necessary to apply an appropriate assist force corresponding to the live load, and the CPLI 29 adjusts the output from the pressure sensor 23 based on this data. In addition to determining the optimum flow ω value corresponding to the detected value, it also instructs the drive circuit of the stepping motor 20 to drive the motor.

The present embodiment is constructed as described above, and the operation (A) will be explained below.

The hydraulic oil discharged from the hydraulic pump 10 by the drive of the engine 11 is divided into the power steering system and the cargo handling system by the flow divider 12, and the hydraulic oil for the power steering system passes through the variable flow rate adjustment valve 19 to the control valve 1.
4, and as long as the handle 1 is not rotated, it is returned to the tank 16 via the return line 15.

In the unloaded state, the holding pressure of the tilt cylinder 21 is equivalent to the weight of the fork 21 (including the mast, etc.), and a signal from the pressure sensor 23 that detects this pressure is input to the CPtJ 29 via the input interface 27. The CPU 29 determines the flow rate (maximum flow rate in this case) corresponding to the above signal based on the data in the storage device 28, and the control signal is output to the stepping motor 20 via the output interface 30. Therefore, the opening degree of the variable flow rate regulating valve 19 in this case is the maximum, and the control valve 14 is supplied with the flow M of hydraulic oil controlled by the 70-divider 12, and in this state, the same steering as in the past You can gain strength.

On the other hand, when a load is loaded on the fork 21, the pressure sensor 23 detects the tilt cylinder 22 corresponding to the loaded load.
The holding pressure of the CPU 2 is detected and the detection signal is input to the CPU 29 via the input interface 27.
9 determines the optimum flow rate for the loaded load from the detection signal and the data in the storage device 28, and controls the stepping motor 20.
Instructs to reduce the flow rate. Therefore, the opening degree of the variable flow rate regulating valve 19 is reduced to correspond to the size of the load. In this way, the hydraulic oil reduced by the variable flow rate adjustment valve 19 is supplied to the control valve 14, and accordingly, the followability of the steering operation decreases by the proportion of the reduction, and the steering wheel 1 becomes heavier. . In other words, the followability of the steering operation gradually decreases as the load increases, and the steering force remains constant both when the vehicle is unladen and when the vehicle is loaded.

Next, another embodiment not shown in FIG. 3 will be described. In this embodiment, a pressure sensor 23 detects the existence and extent of a live load, and a vehicle speed sensor 31 detects the traveling speed of the vehicle. Note that controlling the flow rate to the control valve based on the vehicle speed detection signal itself has been implemented in recent automobiles, but by combining the loaded load and the vehicle speed, it is possible to By controlling the flow rate, it is possible to obtain a constant steering force during the entire cargo handling operation, and in particular, it is possible to reduce the ability to follow sudden steering operations while driving, and to suppress the occurrence of a sense of instability.

In the illustrated example, by detecting the holding pressure of the tilt cylinder 22 with the pressure sensor 23, 1f411! Although the system indirectly detects the load on the rear wheels by detecting the presence and extent of the load, it is also possible to detect the holding pressure of the lift cylinder instead of the tilt cylinder, or directly detect the rear wheel load. Furthermore, the flow fa 1t11 til1 means 18 is not limited to the combination of the variable flow rate regulating valve 19 and the stepping motor 20, but can also be implemented using, for example, a proportional solenoid valve.

(Effects of the Invention) As described in detail above, according to the present invention, it is possible to always maintain a constant steering force regardless of the presence or absence of a live load and its degree, thereby reducing operator fatigue and ensuring safety. It is very useful for operation and also supplies the control valve 8! Since it is a system that only controls the amount, 4M Jfi is simple and easy to maintain.

[Brief explanation of drawings]

The drawings show embodiments of the present invention; FIG. 1 is a circuit diagram showing the hydraulic circuit and flow control circuit of the power steering device, FIG. 2 is a schematic plan view showing the mechanical configuration of the power steering device, and FIG. FIG. 3 is a flow control circuit diagram showing another embodiment of the present invention.

Claims (1)

[Claims] A load sensor that detects the load on the rear wheels in a power steering system that steers the rear wheels as steering wheels by supplying hydraulic oil from a hydraulic pump to the power cylinder via a flow divider and a power steering control valve. and a memory device that stores the relationship between the rear wheel load and the optimum flow rate of the control valve as data;
a flow rate determining means for determining a supply flow rate suitable for the rear wheel load on the control valve based on the load detected by the load sensor and the data in the storage device; A flow rate control device for a power steering device in a cargo handling vehicle, comprising: a flow rate control means for controlling a flow rate supplied to a control valve based on instructions from the control valve.