KR100225963B1 - Method and apparatus for controlling a steering system of an engine driven forklift truck - Google Patents

Abstract

The present invention provides a method and apparatus for controlling a steering system of an engine forklift that can differentiate the sensitivity of a steering wheel in high speed driving and low speed driving.

The steering control system according to the present invention installs an electromagnetic proportional valve on the supply path of the hydraulic oil between the priority valve and the power steering cylinder, and controls the electromagnetic proportional valve in association with the vehicle speed.

The present invention has the effect of differentiating the sensitivity of the steering wheel at high speed and low speed to ensure driving stability at high speed and to reduce driving fatigue at low speed.

Description

Steering system control method and apparatus for engine forklift

The present invention relates to a steering system of an engine forklift, which is a kind of industrial vehicle. More specifically, the driving direction of the vehicle in the engine forklift which is supplied with the power required at the time of operation by appropriately supplying and controlling the pressure oil generated from the hydraulic pump operated by the hydraulic drive motor driven by the engine to each operation part. The present invention relates to a steering system control method and apparatus for controlling hydraulic pressure supplied according to a traveling speed.

Forklifts are widely used throughout the industry as they are effectively used to load or unload cargo. The forklift distributes the pressure oil generated by the hydraulic pump along a predetermined path, for example, to a steering unit for driving a power steering cylinder and a control unit for driving a lift cylinder or a tilt cylinder. Adjust

1 shows a hydraulic circuit diagram of an engine forklift that has been carried out so far. Looking at this, the hydraulic pump 50 is driven by the engine 20 to pump the oil in the oil tank 10 to supply the pressure oil (priority) to the priority valve 60 (priority valve) along a predetermined path Is installed.

The hydraulic pump 50 supplies the pressure oil to the priority valve 60 along a predetermined path. At this time, the pump discharge amount is a value obtained by multiplying the engine revolutions per minute by the pump discharge amount during one revolution as shown in [Equation 1].

Q _p = N _e × q _th / 1000 ---------------------------- [Equation 1]

Q _p : Pump Output Per Minute [LPM]

N _e : Engine revolutions per minute [RPM]

q _th : Pump discharge amount in one rotation [cc / rev]

The priority valve 60 supplies the hydraulic oil supplied from the hydraulic pump 50 to the steering unit 70 controlled by the steering wheel 72 while simultaneously lifting the lift cylinder 112 and the tilt. Dispensing is carried out to the control unit 110 (control unit) consisting of a plurality of valves for controlling the cylinder (114). In this case, the priority valve 60 first supplies pressure oil to the steering unit 70 to sufficiently supply pressure oil necessary for the operation of the steering unit 70, and then supplies the pressure oil to the control unit 110.

The hydraulic oil supplied to the steering unit 70 moves to the left or the right side according to the rotational direction of the steering wheel 72 and power steering via the three-position valve 74 and the steering pump 76 which switch the discharge passage of the hydraulic oil. Supplied to a cylinder 90 (power steering cylinder). At this time, the amount of pressure oil supplied to the power steering cylinder 90 is controlled by the number of revolutions of the steering wheel 72, the rotational force of the steering pump 76 helps the rotation of the steering wheel (72).

Here, the flow rate supplied from the steering unit 70 to the power steering cylinder 90 is determined by multiplying the rotational speed of the steering wheel 72 by the discharge amount per one rotation of the steering unit as shown in [Equation 2]. The flow rate supplied to the cylinder 90 becomes below the said pump discharge amount per minute.

Q _p ≥ Q _m = N × q _th1 / 1000 ---------------------- [Formula 2]

Q _m : Flow rate supplied to the power steering cylinder by the steering unit [LPM]

q _th1 : _Discharge amount of the steering unit [cc / rev]

N: Rotational Speed of Steering Wheel [RPM]

The power steering cylinder 90 rotates the steering wheel 98 in the selected direction according to the movement direction of the piston 92 moving to the left or the right side according to the inflow direction of the hydraulic oil. Steering will be achieved.

At this time, the feed speed of the power steering cylinder rod 91 is represented by the area ratio between the flow rate supplied to the power steering cylinder 90 and the power steering cylinder hydraulic pressure unit as shown in [Equation 3].

V _r = Q _m / A _r --------------------------------- (Equation 3)

= N × q _th1 / {[π × (D ² −d ² ) / 4 × 6000]}

= N × q _th1 / [1500 × π × (D ² -d ² )]

V _r : Feedrate of the power steering cylinder rod

A _r : Area of power steering cylinder hydraulic part

D: inner diameter of power steering cylinder

d: outer diameter of power steering cylinder rod

Accordingly, the degree of rotational resistance of the steering wheel felt by the driver (hereinafter, abbreviated as 'sensitivity of the steering wheel') is determined by the feed speed of the power steering cylinder 90 and the rotation speed of the steering wheel 72 as shown in [Equation 4]. It can be expressed as rain.

_R V _r / N = q _th1 / [1500 × π × (D ² -d ² )] ------------- [Equation 4]

V _r / N: sensitivity of the steering wheel

However, the conventional steering system having such a configuration has a problem of increasing the fatigue of the driver during work because the sensitivity of the steering wheel 72 at a low or high speed is kept constant.

That is, in general, the forklift truck considers two factors in determining the sensitivity of the steering wheel. First of all, in case of low speed driving, the sensitivity of steering wheel should be made as large as possible in consideration of worker's fatigue. In contrast, in case of high speed driving, sensitivity should be smaller than low speed in consideration of vehicle stability. However, since the sensitivity at low speed and high speed cannot be different in the related art, the sensitivity at high speed is reduced by designing with an emphasis on stability. Therefore, since the sensitivity at the low speed becomes small, the rotational resistance of the steering wheel increases during steering, and the rotational resistance of the steering wheel increases during steering, which increases the driver's fatigue.

Accordingly, the present invention has been made to solve the above problems, the object of which is to change the sensitivity of the steering wheel in high-speed driving and low-speed driving to maintain the driving stability at high speed while at the same time the driver fatigue The present invention provides a control method and apparatus for controlling a steering system of an engine forklift.

1 is a hydraulic circuit diagram showing a configuration of a conventional engine forklift steering system

2 is a block diagram showing a control method of the engine forklift steering system according to the present invention.

3 is a hydraulic circuit diagram showing a configuration of an engine forklift steering system according to the present invention.

Figure 4 is a graph comparing the steering characteristic curve showing the relationship between the sensitivity and the vehicle speed of the steering wheel according to the prior art and the present invention

♣ Explanation of symbols for the main parts of the drawing ♣

10: oil tank 20: engine

40: controller 50: hydraulic pump

60: priority valve 70: steering unit

90: power steering cylinder 91: rod

92: piston 94: first chamber

96: second chamber 98: steering wheel

100: vehicle speed sensor 102: propulsion shaft

110: control unit 120: first detection sensor

130: second detection sensor 140: electronic proportional control valve

150: transmission 160: drive shaft

The object of the method of the present invention is from a hydraulic pump operated by an engine, a priority valve supplied with hydraulic oil generated by the hydraulic pump and distributed to a steering unit or a control unit, and a steering unit controlled by a steering wheel. A steering system comprising a power steering cylinder supplied with hydraulic oil and moving in a selected direction according to a rotation direction of a steering wheel and rotating a steering wheel, the steering system comprising: setting a target value of sensitivity to a change in vehicle speed; Sensing the movement speed of the power steering cylinder, the rotation speed of the steering wheel, and the vehicle speed; Calculating the sensitivity of the current steering wheel by comparing the moving speed of the power steering cylinder and the rotational speed of the steering wheel; Calculating an error value by comparing the calculated current sensitivity with the target value; Controlling the amount of pressure oil supplied from the steering unit to the power steering cylinder based on the calculated error value to maintain the sensitivity of the steering wheel to the target value can be achieved by the steering system control method comprising a.

The method of the present invention determines the sensitivity of the steering wheel by gradually reducing the amount of pressure oil supplied from the steering unit to the power steering cylinder as the vehicle speed increases.

The method of the present invention drains the pressure oil supplied from the steering unit to the selected chamber of the first or second chamber of the power steering cylinder as the vehicle speed increases.

It is also an object of the device of the present invention to provide an engine and a transmission for providing a driving force and speed of a vehicle, a hydraulic pump driven by the engine to generate hydraulic pressure, and a first chamber and a second chamber separated by a piston. A power steering cylinder and a priority valve receiving hydraulic pressure pumped from a hydraulic pump and supplying hydraulic pressure to a selected one of the first chamber and the second chamber according to the operation of a steering wheel are used to control the vehicle. A steering control system, comprising: a first sensing sensor configured to sense a rotational speed of a steering wheel and output an electrical signal; A second detection sensor which detects a moving speed of the power steering cylinder and outputs an electrical signal; A vehicle speed sensor for sensing a vehicle speed and outputting an electrical signal; A controller for comparing the respective sensing signals and outputting a control signal; It can be achieved by the steering system control apparatus of the engine forklift, which is composed of adjusting means for varying the amount of pressure oil supplied to the power steering cylinder in accordance with the control signal of the controller.

The adjusting means is characterized in that to gradually reduce the amount of pressure oil supplied to the power steering cylinder as the vehicle speed increases.

Preferably, the adjustment means uses an electromagnetic proportional control valve for draining the hydraulic oil supplied from the steering unit to the power steering cylinder.

The adjusting means drains the pressure oil supplied from the steering unit to the selected chamber of the first or second chamber of the power steering cylinder according to the rotation direction of the steering wheel.

Hereinafter, a preferred embodiment of a steering control system for an engine forklift according to the present invention will be described in detail with reference to the accompanying drawings. (The same components as in the prior art will be described with the same reference numerals.)

2 shows a control block diagram of the steering system according to the present invention, in which the steering unit 70 controlled by the steering wheel 72 and the hydraulic oil controlled by the steering wheel are operated. Power steering cylinder 90, the first detection sensor 120 for detecting the rotational direction and speed of the steering wheel, the second detection sensor 130 for detecting the speed of the power steering cylinder, and the driving speed of the vehicle With the vehicle speed sensor 100. A flow control valve for regulating the amount of pressure oil supplied from the steering unit 70 to the power steering cylinder 90 by the controller 40 receiving the sensing signal from each sensing unit and the control signal of the controller 40 ( 140).

3 is a hydraulic circuit diagram of an engine forklift steering system according to the present invention. According to this, the supplied hydraulic oil is supplied to the steering unit 70 (steering unit) controlled by the steering wheel 72 and at the same time the lift cylinder 90 and the tilt cylinder 90 and the like. A priority valve 60 for distributing to a control unit 110 (control unit) including a plurality of valves for controlling the valve is installed. In this case, the priority valve 60 first supplies pressure oil to the steering unit 70 to sufficiently supply pressure oil necessary for the operation of the steering unit 70, and then supplies the pressure oil to the control unit 110.

The steering unit 70 includes a steering wheel 72 operated by a driver and 3 moving left or right according to the rotational direction of the steering wheel 72 to switch the discharge passage of the hydraulic oil supplied to the steering unit 70. Position valve 74 is provided. The pressure oil discharged through the selected discharge passage of the 3-position valve 74 is supplied to the power steering cylinder 90 via the steering pump 76. At this time, the steering pump 76 is to rotate the steering wheel 72 to double the steering.

The power steering cylinder 90 moves to the left or the right according to the inflow direction of the hydraulic oil, and rotates the steering wheel 98 in the selected direction to achieve steering as intended by the driver, and The rod 91 connected to this piston 92 is provided.

According to the present invention, a first sensing sensor 120 for outputting an electrical signal by detecting a rotational speed and a direction of the steering wheel 72 is installed at the rotating part of the steering wheel, and a rod (on the power steering cylinder 90). By detecting the longitudinal movement of the 91, a second detection sensor 130 for detecting the movement speed thereof and outputting an electrical signal is provided.

On the propulsion shaft 102 connecting the transmission 150 and the drive shaft 160 of the vehicle, a vehicle speed sensor 100 for detecting the vehicle speed by the rotation speed of the propulsion shaft 102 and outputting an electrical signal is installed.

On the other hand, the controller 40 for receiving the signals output from each of the first sensor 120, the second sensor 130 and the vehicle speed sensor 100, compares them and outputs a control signal.

An electronic proportional control valve 140 is provided between the steering unit 70 and the power steering cylinder 90 to vary the amount of pressure oil supplied to the power steering cylinder 90 according to the control signal of the controller 40. It is.

The electromagnetic proportional control valve 140 selects one chamber of the first chamber 94 or the second chamber 96 of the power steering cylinder 90 from the steering unit 70 according to the rotational direction of the steering wheel. It is configured to drain the oil pressure supplied to the selected chamber to the oil tank (10).

Hereinafter will be described a control operation state of the forklift steering system according to the present invention.

The hydraulic pump 50 driven by the engine 20 compresses and pumps the oil in the oil tank 10 to supply the pressurized oil to the priority valve 60 along a predetermined path. At this time, the pump discharge amount per minute is a value obtained by multiplying the engine revolutions per minute by the pump discharge amount per one revolution as shown in [Equation 1].

Q _p = N _e × q _th / 1000 ---------------------------- [Equation 1]

Q _p : Pump Output Per Minute [LPM]

N _e : Engine revolutions per minute [RPM]

q _th : Pump discharge amount in one rotation [cc / rev]

Priority valve 60 supplies the hydraulic oil supplied from the hydraulic pump 50 to the steering unit 70 (steering unit) controlled by the steering wheel 72 and at the same time lift cylinder 90 and tilt Dispensing is carried out to the control unit 110 (control unit) consisting of a plurality of valves for controlling the cylinder (90) (tilt cylinder). In this case, the priority valve 60 first supplies pressure oil to the steering unit 70 to sufficiently supply pressure oil necessary for the operation of the steering unit 70, and then supplies the pressure oil to the control unit 110.

The hydraulic oil supplied to the steering unit 70 is supplied to the power steering cylinder 90 via a three-position valve 74 that moves left or right in accordance with the rotational direction of the steering wheel 72 and switches the discharge passage of the hydraulic oil. Done. At this time, the amount of pressure oil supplied to the power steering cylinder 90 is variably controlled by the motor 76 which is variable according to the rotational speed of the steering wheel 72.

In addition, the controller 40 determines the rotation direction of the steering wheel 72 by determining the signal applied from the first detection sensor 120, and moves the electromagnetic proportional control valve 140 in the selected direction to move the first chamber ( 94) or the pressure oil is withdrawn from the selected chamber of the second chamber (96) and drained to the oil tank (10). At this time, the amount of pressure oil drained is proportional to the detection signal of the vehicle speed sensor 100 applied to the controller 40.

Therefore, the flow rate finally supplied from the steering unit 70 to the power steering cylinder is the flow rate drained to the tank through the electromagnetic proportional control valve 140 at the flow rate supplied to the power steering cylinder by the steering unit as shown in [Equation 5]. Minus

Q _a = Q _m -Q _b (V _r ) ---------------------------- [Equation 5]

Q _a : The flow rate finally supplied to the power steering cylinder [LPM]

Q _b (V _r ): Flow rate drained to tank through electronic proportional control valve [LPM] depending on vehicle speed

The power steering cylinder 90 rotates the steering wheel 98 in the selected direction according to the movement direction of the piston 92 moving to the left or the right side according to the inflow direction of the hydraulic oil. Steering will be achieved.

At this time, the moving speed of the power steering cylinder rod 91 is an area ratio between the flow rate finally supplied to the power steering cylinder 90 and the power steering cylinder hydraulic pressure unit as shown in [Equation 6].

V _r = Q _a / A _r --------------------------------- [Formula 6]

= (Q _m -Q _b (V _r )) / A _r

= N × q _th1 / {[π × (D ² -d ² ) / 4 × 6000]}-Q _b (V _r ) / A _r

= N × q _th1 / [1500 × π × (D ² -d ² )]-Q _b (V _r ) / A _r

V _r : Movement speed of the power steering cylinder rod [m / sec]

A _r : Area of power steering cylinder hydraulic part [cm ² ]

D: inner diameter of power steering cylinder [cm]

d: outer diameter of power steering cylinder rod [cm]

Therefore, the sensitivity of the steering wheel according to the present invention can be represented by the ratio of the rotational speed of the steering wheel 72 to the moving speed of the power steering cylinder 90 as shown in [Equation 6].

_R V _r / N = q _th1 / [1500 × π × (D ² -d ² )]-Q _b (V _r ) A _r / N ----- [Equation 7]

V _r / N: sensitivity of steering wheel [m / sec / RPM]

As can be seen here, the sensitivity of the steering wheel according to the present invention is related to the amount of pressure oil controlled by the electronic proportional control valve 70 controlled according to the vehicle speed, it can be seen that it varies with the change in speed.

This relationship is well illustrated in the relationship graph between the sensitivity and the vehicle speed shown in FIG. 4. In other words, a steering characteristic curve of inverse relationship is obtained when the sensitivity is the highest when the vehicle speed is the lowest, and the sensitivity gradually decreases as the vehicle speed increases. This is a relationship between the conventional sensitivity and the vehicle speed shown in FIG. .

As described above, the steering control system of the engine forklift according to the present invention installs an electromagnetic proportional valve on the supply path of the hydraulic oil between the priority valve and the power steering cylinder, and controls the electromagnetic proportional valve in association with the vehicle speed. By differentiating the sensitivity of the steering wheel at high speed and low speed, it is possible to secure driving stability at high speed and to reduce driving fatigue at low speed.

Claims (7)

A hydraulic pump 50 operated by the engine 20, a priority valve 60 supplied with the hydraulic oil generated by the hydraulic pump 50 and distributed to the steering unit 70 or the control unit 110, An engine forklift having a power steering cylinder (90) for supplying pressure oil from a steering unit (70) controlled by the steering wheel (72), moving in a selected direction according to the rotation direction of the steering wheel (72), and rotating a steering wheel. In the control method of the steering system of, Setting a target value of sensitivity to a change in vehicle speed; Sensing the movement speed of the power steering cylinder 90 and the rotation speed of the steering wheel 72 and the vehicle speed; Calculating the sensitivity of the current steering wheel by comparing the moving speed of the power steering cylinder 90 and the rotational speed of the steering wheel 72; Calculating an error value by comparing the calculated current sensitivity with a target value corresponding to the detected vehicle speed; Controlling the amount of pressure oil supplied from the steering unit 70 to the power steering cylinder 90 based on the calculated error value to maintain the sensitivity of the steering wheel 72 at the target value. Steering System Control Method. 2. The steering system control method according to claim 1, wherein the sensitivity of the steering wheel is controlled by gradually reducing the amount of pressure oil supplied from the steering unit 70 to the power steering cylinder 90 as the vehicle speed increases. . 3. The pressure oil of claim 2, wherein the hydraulic oil supplied from the steering unit 70 to the chamber selected from the first chamber 94 or the second chamber 96 of the power steering cylinder 90 according to the rotation of the steering wheel 72 is drained. Steering system control device for an engine forklift, characterized in that. An engine 20 for driving the oil pump, a power steering cylinder 90 having a first chamber 94 and a second chamber 96 separated by a piston 92, and a pump pumped from the hydraulic pump 50 An engine for steering the vehicle by providing a pressure valve 60 for receiving pressure oil and supplying pressure oil to a chamber selected from the first chamber 94 or the second chamber 96 according to an operation of the steering wheel 72. In the forklift steering control system, A first detection sensor 120 which detects a rotational speed of the steering wheel 72 and outputs an electrical signal; A second detection sensor 130 which detects a moving speed of the power steering cylinder 90 and outputs an electrical signal; A vehicle speed sensor 100 which detects a vehicle speed and outputs an electrical signal; A controller 40 for comparing the respective sensing signals and outputting a control signal; Steering system control device of the engine forklift comprising an adjusting means for varying the amount of pressure oil supplied to the power steering cylinder (90) in accordance with the control signal of the controller (40). 5. The steering system control apparatus for an engine forklift according to claim 4, wherein the adjusting means gradually reduces the amount of hydraulic oil supplied to the power steering cylinder (90) as the vehicle speed increases. 6. The steering system control apparatus for an engine forklift according to claim 5, wherein the adjusting means is an electromagnetic proportional control valve (140) for draining the hydraulic oil supplied from the steering unit (70) to the power steering cylinder (90). 7. The hydraulic oil according to claim 6, wherein the adjustment means is supplied from the steering unit 70 to the chamber selected from the first chamber 94 or the second chamber 96 of the power steering cylinder 90 in accordance with the rotation direction of the steering wheel. Steering system control apparatus for an engine forklift, characterized in that the drain.

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