JP4936514B2 - Industrial vehicle hydraulic system - Google Patents

Description

  The present invention relates to a hydraulic system for an industrial vehicle that operates a steering actuator by hydraulic pressure, and more particularly to a hydraulic system that can supply hydraulic oil from a pump that supplies hydraulic oil to a steering actuator to other actuators.

  Conventionally, in a vehicle equipped with a hydraulic steering device, hydraulic oil is supplied to actuators of other hydraulic devices using a pump that supplies hydraulic oil to a steering actuator provided in the steering device, and the device is operated. In this way, the system is simplified and reduced in weight. For example, as shown in Patent Document 1, hydraulic oil is supplied to a steering actuator (steering cylinder) and a hydraulic cylinder of a tilling device in a tractor, and in a forklift, for example, a steering actuator is used in a forklift. The hydraulic oil is supplied to a (steering cylinder) and a hydraulic cylinder (lift cylinder or the like) that performs cargo handling.

JP 2000-85598 A JP 2002-19627 A

  Now, for example, as shown in Patent Document 1, when switching between supplying hydraulic oil from a pump to a steering actuator or supplying to another actuator using a switching valve, the hydraulic oil is supplied to both actuators simultaneously. In this case, the switching valve is frequently switched. For this reason, there is a problem that the efficiency is deteriorated and a shock occurs at the time of switching. However, simply supplying a sufficient amount of hydraulic fluid to both actuators eliminates the shock caused by switching, but if the actuator is not operated, the hydraulic fluid is returned to the tank as it is. Not right.

  Further, in order to change the direction of the steered wheels as desired according to the operation of the steering wheel, it is necessary to supply an appropriate amount of hydraulic oil to the steering actuator. In particular, when hydraulic fluid is supplied from the same pump to other actuators, the amount of oil discharged from the pump is limited, so it is important to secure the hydraulic fluid supplied to the steering actuator. Become.

  It is an object of the present invention to be able to supply hydraulic oil to a steering actuator and other actuators simultaneously and satisfactorily and to operate the steering actuator with good responsiveness to a steering operation.

  In order to achieve the above object, the present invention is an industrial vehicle hydraulic system in which hydraulic oil is supplied to other actuators by a pump that supplies hydraulic oil to a steering actuator that operates in response to a steering operation. The supply path for supplying hydraulic oil from the pump to both actuators includes a first supply path for supplying hydraulic oil to the steering actuator and a first supply path for supplying hydraulic oil to the other actuators. And is divided into two supply paths, and is provided on the first supply path, and is switched between an open state allowing flow from the pump to the steering actuator and a closed state preventing flow. A possible first valve, a second valve provided in parallel with the first valve on the first supply path and always allowing a predetermined amount of flow, and connected to the first supply path; Up And a third valve for controlling the flow from the first and second valves to the steering actuator. The first valve is switched to the open state when the handle is operated, and the handle is When not operated, the third valve is switched to the closed state, and when the handle is operated, the third valve is switched to a state allowing flow from the first and second valves to the steering actuator. When the handle is not operated, it is switched to a state in which the flow is blocked.

  According to the present invention, since the first valve is switched to the closed state when the handle is not operated, the hydraulic oil from the pump is supplied through the second valve. However, since the flow to the steering actuator is blocked by the third valve, the hydraulic oil is not supplied to the steering actuator and the steering actuator does not operate. On the other hand, since the hydraulic oil is supplied to the other actuators through the second supply path branched from the first supply path, the other actuators operate. When the handle is operated, the first valve is switched to the open state, and hydraulic oil from the pump is supplied through the first valve and the second valve. At this time, since the third valve allows a flow to the steering actuator, a necessary amount of hydraulic oil can be supplied to the steering actuator to operate the steering actuator. Note that when the first valve is opened, the hydraulic oil supplied to the other actuators is reduced by the amount passing through the first valve, and the hydraulic oil is preferentially supplied to the steering actuator. Become.

  Further, according to the present invention, since the hydraulic oil flows through the second valve even when the handle is not operated, the hydraulic oil can be supplied to the steering actuator as soon as the handle is operated. Therefore, even if the steering wheel is suddenly operated, the steering actuator can be operated without delay, and good responsiveness to the steering wheel operation can be realized. In addition, since the operating oil does not suddenly start to flow or flow is interrupted, it is possible to prevent other actuators from being shocked when operating the handle or stopping the operation. Furthermore, even if the first valve fails and cannot be switched to the open state, the third valve allows the flow to the steering actuator when the handle is operated. The steering actuator can be operated by the supplied hydraulic oil.

  In the above configuration, the first valve is an electrically switchable electromagnetic valve, the third valve is a manual valve mechanically connected to the handle, and the first valve is operated in response to the operation of the handle. In the case of including control means for controlling one valve, the control means switches the first valve to the open state when the handle is operated, and the control means when the handle is not operated. The first valve can be switched to the closed state.

  In this way, when the handle is operated, the first valve is switched to the open state by the control means, and hydraulic oil from the pump is supplied through the first valve and the second valve. At this time, since the third valve is switched to a state in which the flow to the steering actuator is allowed according to the steering operation, the necessary amount of hydraulic oil can be supplied to the steering actuator to operate the steering actuator. it can. On the other hand, if the handle is not operated, the first valve is switched to the closed state by the control means, and hydraulic oil is not supplied through the first valve. Therefore, since the hydraulic oil only flows through the second valve, the hydraulic oil supplied to other actuators can be ensured. At this time, since the third valve is switched to a state in which the flow to the steering actuator is blocked according to the steering operation, the steering actuator does not operate.

  In addition to the above-described configuration, in the apparatus including speed detection means for detecting the operation speed of the steering wheel, the control means calculates the amount of oil supplied to the steering actuator based on the operation speed, and the oil quantity is When the predetermined amount is exceeded, the first valve can be switched to the open state.

  In this way, the amount of oil corresponding to the operation speed of the steering wheel is reliably supplied to the steering actuator, and the driver can operate the steering actuator as desired by operating the steering wheel. In addition, when the calculated amount of oil can be supplied to the steering actuator only through the second valve, the first valve is kept in the closed state, so that the hydraulic oil supplied to other actuators is unnecessary. It is not necessary to reduce it.

  In the above configuration, the opening degree of the first valve can be changed in the opened state, and the control means can control the first valve based on the calculated oil amount. It is possible to determine the opening and control the first valve so as to be the opening.

  In this way, the amount of oil corresponding to the operation speed of the steering wheel is accurately supplied to the steering actuator, and the driver can operate the steering actuator as desired by operating the steering wheel. In addition, when the calculated amount of oil is small, the opening degree of the first valve is reduced, so that the hydraulic oil supplied to other actuators need not be reduced unnecessarily.

  Note that the number of other actuators in the present invention is not limited to one, and there may be a plurality of other actuators, and the application (device operated by the actuator) is not limited to one.

As described above, according to the present invention, when the handle is operated, the first valve is switched to the open state, and the third valve is switched to the state allowing the flow to the steering actuator. Therefore, the hydraulic oil from the pump can be supplied to the steering actuator through the first valve and the second valve to operate the steering actuator.
On the other hand, if the handle is not operated, the first valve is switched to the closed state, and the third valve is switched to the state of blocking the flow to the steering actuator, so that the steering actuator does not operate. However, since the hydraulic oil flows through the second valve, the hydraulic oil can be supplied to the steering actuator as soon as the handle is operated.
Since the first supply path for supplying hydraulic oil to the steering actuator and the second supply path for supplying hydraulic oil to the other actuators are branched, regardless of whether the handle is operated or not. The hydraulic oil from the pump can be supplied to the other actuators for operation. However, when the steering wheel is operated, hydraulic oil is preferentially supplied to the steering actuator.

  Hereinafter, an embodiment in which the present invention is applied to a forklift will be described with reference to the drawings.

  As shown in FIG. 1, the forklift according to this embodiment includes a front wheel 2 as a driving wheel at a front portion of a vehicle body 1, and a rear wheel 3 as a steered wheel at a rear portion of the vehicle body 1. The rear wheel 3 is attached to a steering device provided on the vehicle body 1, and the steering device is provided with a steering cylinder 4 that turns the rear wheel 3 to change its direction. Here, the steering cylinder 4 is a double-acting double rod cylinder, and the rear wheel 3 turns with the movement of the rod. Further, a battery 5 is mounted in the front and rear center of the vehicle body 1, and a seat 6 on which a driver sits is provided on a cover that covers the battery 5.

A steering handle 7 for changing the direction of the rear wheel 3 and a lift lever 8 for raising and lowering a fork 11 to be described later are provided at the front of the vehicle body 1 so as to face the driver sitting on the seat 6. A tilt lever 9 for tilting the mast 10 is provided.
The steering handle 7 is rotatably provided within a predetermined operating range, and a steering sensor 7a for detecting the rotation speed is attached to the steering handle 7. The lift lever 8 and the tilt lever 9 are both tiltable forward and backward. The lift lever 8 is provided with a lift sensor 8a for detecting the tilt angle, and the tilt lever 9 detects the tilt angle. A tilt sensor 9a is attached. Here, the lift sensor 8a is provided so as to detect a tilt angle when the lift lever 8 is operated backward (frontward as viewed from the driver) with reference to a state where the lift sensor 8a is not operated (neutral state). Yes. The tilt sensor 9a has a tilt angle when the tilt lever 9 is operated forward (backward as viewed from the driver) or rearward (frontward as viewed from the driver) with reference to an unoperated state (neutral state). It is provided to detect.

  Further, as shown in FIG. 1, a mast 10 is supported at the front portion of the vehicle body 1 so as to be tiltable, and a fork 11 is supported on the mast 10 so as to be movable up and down. The mast 10 is provided with a lift cylinder 12 formed of a single-acting single rod cylinder. The fork 11 is raised when the lift cylinder 12 is extended, and is lowered when the lift cylinder 12 is shortened. A tilt cylinder 13 composed of a double-acting single rod cylinder is provided between the vehicle body 1 and the mast 10. When the tilt cylinder 13 extends, the mast 10 tilts forward together with the fork 11 and the lift cylinder 12, and the tilt cylinder 13. When it is shortened, it tilts backward.

  The vehicle body 1 is provided with a tank 14 that stores hydraulic oil to be supplied to each cylinder. Further, a pump 15 that pressurizes and discharges hydraulic oil sucked from the tank 14, and a motor 16 that drives the pump 15. Is provided. The motor 16 is provided with a motor sensor 16a for detecting the rotational speed.

  As shown in FIG. 2, the hydraulic oil from the pump 15 is supplied through supply paths X1 and Y1 formed in a branched manner, and the lift cylinder 12 and the steering cylinder 4 are connected to the steering cylinder 4 through the supply path X1. Hydraulic oil is supplied to the tilt cylinder 13 through the supply path Y1. Further, the hydraulic oil is recovered to the tank 14 from the steering cylinder 4 by the recovery path X2 and from the lift cylinder 12 and the tilt cylinder 13 by the recovery path Y2.

  On the supply path X 1, an electromagnetic valve 17 and an orifice 18 are provided in parallel, and the supply path X 1 is connected to the steering valve 19 at a position downstream from the pump 15. The steering valve 19 is connected to the steering cylinder 4 by hydraulic piping, and the hydraulic oil that has passed through the electromagnetic valve 17 and the orifice 18 is supplied to the steering cylinder 4 via the steering valve 19, and is operated from the steering cylinder 4. Oil is recovered via the steering valve 19.

  Here, the electromagnetic valve 17 can be switched between a closed position where the flow of hydraulic oil between the pump 15 and the steering valve 19 is blocked, and an open position where the flow of hydraulic oil from the pump 15 to the steering valve 19 is allowed. There is an electromagnetic proportional control valve that can be adjusted until the opening at the open position is fully opened. When the built-in solenoid is excited, the electromagnetic valve 17 is opened at an opening degree corresponding to the exciting current, and when the excitation is stopped, the electromagnetic valve 17 is returned to the closed position by a built-in spring. The orifice 18 is a flow control valve that allows a flow of a predetermined amount Ls1 (> 0) per unit time.

  The steering valve 19 is a manual switching valve having a metering mechanism that is mechanically coupled to the steering handle 7. The steering valve 19 is a hydraulic valve that is supplied to the steering cylinder 4 by the metering mechanism according to the operation of the steering handle 7. The amount is adjusted and its position is switched. That is, when the steering handle 7 is operated to rotate clockwise, the hydraulic oil is supplied to one oil chamber (left oil chamber) provided in the steering cylinder 4 and is recovered from the other oil chamber (right oil chamber). Switch to the swivel position. When the steering handle 7 is operated to rotate counterclockwise, the steering wheel 7 is switched to the left-turning position where hydraulic oil is collected from one oil chamber (left oil chamber) and supplied to the other oil chamber (right oil chamber). . When the operation of the steering handle 7 is stopped, it is returned to the neutral position where the flow of hydraulic oil between the steering cylinder 4 and the supply path X1 and the recovery path X2 is blocked by the built-in spring.

  On the other hand, the supply path Y1 and the recovery path Y2 are connected to the lift valve 20 and the tilt valve 21, and the supply and recovery of the hydraulic oil to the lift cylinder 12 are performed via the lift valve 20, and the operation to the tilt cylinder 13 is performed. Oil is supplied and recovered through a tilt valve 21.

The lift valve 20 is a manual switching valve that is mechanically connected to the lift lever 8. When the lift lever 8 is operated forward (backward as viewed from the driver), the lift valve 20 is switched to the lowered position, and the rear (driver) When it is operated to the front), it switches to the raised position, and when it is not operated, it switches to the neutral position by a built-in spring.
The tilt valve 21 is a manual switching valve that is mechanically coupled to the tilt lever 9. When the tilt lever 9 is operated forward (backward as viewed from the driver), the tilt valve 21 is switched to the forward tilt position, and the rear (driving) When it is operated to the front (when viewed from the person), it switches to the backward tilted position, and when it is not operated, it switches to the neutral position by a built-in spring.

  The vehicle body 1 is provided with a control device 22 for controlling the motor 16 and the electromagnetic valve 17 described above. As shown in FIG. 3, signals from the steering sensor 7a, the lift sensor 8a, the tilt sensor 9a, and the motor sensor 16a are input to the control device 22, and the control device 22 responds to these signals to rotate the motor 16 according to these signals. And the opening degree of the electromagnetic valve 17 is controlled.

  The control device 22 includes a setting unit 22A that determines a target rotation speed of the motor 16 and an opening degree of the electromagnetic valve 17 in accordance with an input signal, and the determined target rotation speed and the actual rotation speed detected. Are provided with a motor control unit 22B for controlling the motor 16 so as to coincide with each other, and a valve control unit 22C for controlling the electromagnetic valve 17 so as to achieve the determined target opening degree.

  The setting unit 22A determines whether or not the steering handle 7 is operated based on the rotational speed S of the steering handle 7 transmitted from the steering sensor 7a, and the target rotational speed of the motor 16 and the electromagnetic force are determined as follows according to the determination result. The target opening degree of the valve 17 is determined.

  When the steering handle 7 is not operated, the setting unit 22A sets the target opening V of the electromagnetic valve 17 to 0 (that is, the electromagnetic valve 17 is in the closed position), and the motor according to the signals from the lift sensor 8a and the tilt sensor 9a. Sixteen target rotational speeds are determined. That is, if the tilt angle of the lift lever 8 by the lift sensor 8a or the tilt angle of the tilt lever 9 by the tilt sensor 9a is greater than or equal to the predetermined value A0, the setting unit 22A sets the target rotational speed to a predetermined value. If any tilt angle is not greater than or equal to the predetermined value A0, the target rotational speed is set to 0 and the motor 16 is not driven.

On the other hand, when the steering handle 7 is being operated, the setting unit 22A calculates an oil amount Ls to be supplied to the steering cylinder 4 based on a signal from the steering sensor 7a. That is, as shown in FIG. 4, when the rotational speed S of the steering wheel 7 is 0 ≦ S <S1, the oil amount Ls is proportional to the rotational speed S, that is, Ls = (Ls2 / S1) × S, and S1 ≦ S <S2 is a constant oil amount Ls = Ls2 regardless of the rotation speed S, and S2 ≦ S <S3 is an oil amount Ls proportional to the rotation speed S, that is, Ls = (Ls3-Ls2) / (S3- S2) × (S−S2) + Ls2, and when S ≧ S3, a constant oil amount Ls = Ls3 regardless of the rotational speed S. As shown in FIG. 4, the oil amounts Ls2 and Ls3 are set so that Ls1 <Ls2 <Ls3.
The setting unit 22A calculates the amount of hydraulic oil Ll supplied to the lift cylinder 12 through the lift valve 20 based on the signal from the lift sensor 8a, and passes through the tilt valve 21 based on the signal from the tilt sensor 9a. An oil amount Lt of hydraulic oil supplied to the tilt cylinder 13 is calculated. That is, the relationship between the tilt angle Al of the lift lever 8 and the oil amount L1 passing through the lift valve 20 and the relationship Lt between the tilt angle At of the tilt lever 9 and the oil amount passing through the tilt valve 21 are proportional to each other as shown in FIG. Therefore, the setting unit 22A calculates the oil amounts Ll and Lt by multiplying the detected tilt angles Al and At by a predetermined proportional coefficient.
Then, the setting unit 22A is based on the oil amount Ls obtained based on the rotational speed S of the steering handle 7, the oil amount Ll obtained based on the tilt angle Al of the lift lever 8, and the tilt angle At of the tilt lever 9. The oil amount Lt obtained in this way is summed, and the rotational speed when the resulting total oil amount is discharged from the pump 15 is taken as the target rotational speed.

  Further, the setting unit 22A determines a target opening degree V of the electromagnetic valve 17 based on a signal from the steering sensor 7a. That is, as shown in FIG. 6, when the rotational speed S of the steering handle 7 is 0 ≦ S <S0, the target opening V of the electromagnetic valve 17 is set to 0 (that is, the electromagnetic valve 17 is closed), and S0 ≦ S. When S <1, the target opening degree V is proportional to the rotational speed S, that is, V = V2 / (S1-S0) × (S−S0), and when S1 ≦ S <S2, it is constant regardless of the rotational speed S. The target opening V = V2, and when S2 ≦ S <S3, the target opening V proportional to the rotational speed S, that is, V = (V3−V2) / (S3−S2) × (S−S2) + V2, When S ≧ S3, a constant target opening V = V3 regardless of the rotational speed S. Here, S0 is the rotation speed when the oil amount Ls supplied to the steering cylinder 4 becomes the oil amount Ls1, V2 is the opening when the oil amount passing through the electromagnetic valve 17 becomes Ls2-Ls1, and V3. Is the opening when the amount of oil passing through the electromagnetic valve 17 is Ls3-Ls1.

  The motor control unit 22B performs drive control of the motor 16 so that the target rotation speed determined by the setting unit 22A matches the actual rotation speed detected by the motor sensor 16a. Further, the valve control unit 22C gives an excitation current corresponding to the target opening degree V determined by the setting unit 22A to the solenoid of the electromagnetic valve 17 (when the target opening degree V is 0, no excitation current is given). The valve 17 is controlled.

Accordingly, when the steering handle 7 is not operated, the electromagnetic valve 17 is in the closed position, so that the hydraulic oil from the pump 15 is supplied through the orifice 18. However, since the flow to the steering cylinder 4 is blocked by the steering valve 19, no hydraulic oil is supplied to the steering cylinder 4 and the steering cylinder 4 does not operate. If the lift lever 8 or the tilt lever 9 is operated, the lift cylinder 12 and the tilt cylinder 13 operate.
When the steering handle 7 is operated, the electromagnetic valve 17 is opened at the target opening V, and the motor 16 is driven at the target rotational speed. Therefore, the hydraulic oil from the pump 15 is supplied through the electromagnetic valve 17 and the orifice 18. At this time, the steering valve 19 allows the flow to the steering cylinder 4, so that the steering cylinder 4 operates. If the lift lever 8 or the tilt lever 9 is operated, the motor 16 is accelerated in accordance with the operation to secure the amount of oil to be supplied, and the lift cylinder 12 and the tilt cylinder 13 operate.

  According to such an embodiment, the amount of oil corresponding to the rotational speed S of the steering handle 7 is reliably supplied to the steering cylinder 4, so that the driver operates the steering cylinder 4 as desired by operating the steering handle 7. Can be made. Further, since the motor 16 and the electromagnetic valve 17 are controlled based on the oil amount calculated in the setting unit 22A, each cylinder is operated without running out of hydraulic oil supplied to the lift cylinder 12 and the tilt cylinder 13. Can be made.

  Further, according to this embodiment, since the hydraulic oil flows through the orifice 18 even when the steering handle 7 is not operated, the steering cylinder 4 can be operated without delay even if the steering handle 7 is suddenly operated. . Furthermore, since the hydraulic oil does not suddenly start to flow or the flow is interrupted, it is not necessary to give a shock to the lift cylinder 12 and the tilt cylinder 13 when operating the steering handle 7 or stopping the operation. Furthermore, even if the electromagnetic valve 17 fails and cannot be switched to the open position, the steering cylinder 4 can be operated with the hydraulic oil supplied through the orifice 18.

1 is a side view of a forklift according to an embodiment of the present invention. It is a hydraulic circuit diagram of the Example of this invention. It is a functional block diagram of the Example of this invention. It is a control characteristic figure of the Example of this invention, and represents the relationship between the rotational speed of a steering wheel, and the oil quantity supplied to a steering cylinder. It is a control characteristic figure of the Example of this invention, and represents the relationship between the tilt angle of a lift lever and the oil amount which passes a lift valve, and the relationship between the tilt angle of a tilt lever and the oil amount which passes a tilt valve. It is a control characteristic figure of the Example of this invention, and represents the relationship between the rotational speed of a steering wheel, and the target opening degree of an electromagnetic valve.

Explanation of symbols

1 Car body 3 Rear wheel 4 Steering cylinder 7 Steering handle 7a Steering sensor 8 Lift lever 8a Lift sensor 9 Tilt lever 9a Tilt sensor 10 Mast 11 Fork 12 Lift cylinder 13 Tilt cylinder 17 Electromagnetic valve 18 Orifice 19 Steering valve 20 Lift valve 21 Tilt valve 22 control device 22A setting unit 22B motor control unit 22C valve control unit X1 supply path Y1 supply path

Claims (4)

An industrial vehicle hydraulic system that supplies hydraulic oil to another actuator by a pump that supplies hydraulic oil to a steering actuator that operates in response to a steering operation.
A supply path for supplying hydraulic oil from the pump to both actuators includes a first supply path for supplying hydraulic oil to the steering actuator, and a second path for supplying hydraulic oil to the other actuators. Formed by branching to the supply path,
A first valve provided on the first supply path and switchable between an open state allowing flow from the pump to the steering actuator and a closed state blocking flow; and the first valve A second valve that is provided in parallel with the first valve on the supply path and always allows a predetermined amount of flow, and is connected to the first supply path, and is used for the steering from the first and second valves. A third valve for controlling the flow to the actuator,
The first valve is switched to the open state when the handle is operated, and is switched to the closed state when the handle is not operated. The third valve is operated to the handle. And an industrial vehicle characterized in that it is switched to a state that allows flow from the first and second valves to the steering actuator and is blocked when the steering wheel is not operated. Hydraulic system. The first valve is an electrically switchable electromagnetic valve, the third valve is a manual valve mechanically connected to the handle, and the first valve is operated in response to the operation of the handle. A control means for controlling the valve,
The control means switches the first valve to the open state when the handle is operated, and switches the first valve to the closed state when the handle is not operated. The hydraulic system for an industrial vehicle according to claim 1, wherein the hydraulic system is an industrial vehicle. A speed detecting means for detecting the operation speed of the handle;
The control means calculates an oil amount to be supplied to the steering actuator based on the operation speed, and switches the first valve to the open state when the oil amount exceeds the predetermined amount. The hydraulic system for an industrial vehicle according to claim 2, wherein the hydraulic system is an industrial vehicle. The first valve can change its opening degree in the open state,
The said control means determines the opening degree of the said 1st valve based on the said oil amount calculated, and controls the said 1st valve so that it may become this opening degree. 4. The industrial vehicle hydraulic system according to 3.

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