JP2007254058A - Hydraulic system and forklift provided with this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic system with a relatively simple constitution and sufficient efficiency. <P>SOLUTION: The hydraulic system is provided with a hydraulic pump mechanically connected to an electric motor on a feeding hydraulic pipe for feeding an operation oil to a hydraulic actuator and is provided with a hydraulic motor operated by feeding the operation oil from the hydraulic actuator on a recovery hydraulic pipe for recovering the operation oil from the hydraulic actuator. Here, the hydraulic motor and the electric motor are mechanically connected to each other through a clutch device capable of only transmitting torque from the hydraulic motor to the electric motor. When an operation direction of an operation member is a direction corresponding to recovery of the operation oil, a control means controls a solenoid valve provided on the recovery hydraulic pipe so as to be fully opened in the state that it allows a flow to the hydraulic motor from the hydraulic actuator, and regenerative-controls the electric motor by the instruction number of revolution determined based on an operation amount. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydraulic system for operating a hydraulic actuator, and a forklift configured to raise and lower a fork using the hydraulic system.

  Conventionally, a hydraulic system is used for a lifting device that raises and lowers a lifting tool (such as a fork of a forklift or a work platform of an aerial work platform) up and down. Attempts have been made to recover (regenerate). For example, in a forklift, a so-called lift lowering regeneration technique has been proposed in which a hydraulic system of a lifting device for cargo handling is used to convert a potential energy of a fork or a baggage into electric energy and charge a battery when the lift is lowered.

As this lift lowering regeneration technique, for example, as described in Patent Document 1, a hydraulic motor is provided in a return line from a lift cylinder, a generator is connected to the hydraulic motor, and a battery is charged from the generator. There is something like that. Further, as described in Patent Document 2 and Patent Document 3, the hydraulic pump can be used as a hydraulic motor, and the hydraulic pump is reversed by hydraulic oil pushed out from a lift cylinder for lifting when the lift is lowered (as a hydraulic motor). In some cases, an electric motor connected to a hydraulic pump is operated as a generator.
In the technique described in Patent Document 2, an electromagnetic clutch is provided between the electric motor and the hydraulic pump, and power transmission is interrupted by the electromagnetic clutch if regeneration is impossible when the lift is lowered. In the technique described in Patent Document 3, if regeneration is possible when the lift is lowered, the solenoid valve is switched, and regeneration control of the motor is performed with a torque command value corresponding to the lever operation amount.

By the way, in order to control the flow rate in the hydraulic system, a manual valve is used as in the technique described in Patent Document 1, and an electromagnetic valve may be used. In the technique described in Patent Document 4, when the fork is moved up and down according to the lever operation, the electromagnetic proportional control valve is controlled to have an opening corresponding to the operation amount, and the fork is stopped at a preset stop position. In this case, the motor is controlled after the electromagnetic proportional control valve is fully opened.
Further, for example, as described in Patent Document 1, there is one in which the flow on the supply side and the flow on the recovery side are controlled by a single valve. Some of them have valves on the recovery pipes.

JP 55-56999 A JP-A-2-169499 JP 2003-252592 A JP 2002-356300 A Japanese Utility Model Publication No. 6-10295

In the case of a hydraulic system that includes a hydraulic pump and a hydraulic motor, respectively, and an electric motor and a generator, other hydraulic actuators can be used during regeneration for a certain hydraulic actuator (for example, lift cylinder). It is possible to operate by supplying hydraulic oil. However, since a large space is required for installation of equipment and the weight increases, there is a problem in that it is disadvantageous when employed in an industrial vehicle such as a forklift.
On the other hand, if the hydraulic system uses a hydraulic pump as a hydraulic motor and uses an electric motor for driving the hydraulic pump as a generator, installation space and weight can be reduced. However, there is a problem that supply of hydraulic oil and recovery while performing regeneration cannot be performed at the same time, which is unsuitable for a hydraulic system including a plurality of hydraulic actuators.

  Further, for example, as in the technique described in Patent Document 1, regeneration is performed while adjusting the lift lowering speed with a manual valve, that is, while adjusting the amount of return oil from the lift cylinder with the manual valve. In a state where the lift lowering speed is relatively slow and the amount of return oil is small and limited, there is a problem that sufficient regeneration cannot be performed and energy is wasted.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an efficient hydraulic system with a relatively simple configuration. Moreover, it aims at providing the forklift provided with such a hydraulic system.

  In order to achieve the above object, a hydraulic system according to the present invention is mechanically connected to an electric motor in a first supply hydraulic pipe that supplies hydraulic oil from a tank that stores hydraulic oil to a first hydraulic actuator. A hydraulic pump that is driven by the electric motor and sucks hydraulic oil from the tank and discharges the hydraulic oil to the first hydraulic actuator, and collects the hydraulic oil from the first hydraulic actuator to the tank. The recovery hydraulic pipe is provided with a hydraulic motor that operates when hydraulic oil is supplied from the first hydraulic actuator, and a second supply that supplies hydraulic oil from the hydraulic pump to the second hydraulic actuator. A hydraulic system comprising: a hydraulic pipe for operation and a second recovery hydraulic pipe for recovering hydraulic oil from the second hydraulic actuator to the tank And an electromagnetic valve provided in the first recovery hydraulic pipe for controlling the flow of hydraulic oil between the first hydraulic actuator and the hydraulic motor, and for operating the first hydraulic actuator. A first operating member operated by the operator, an operation detecting means for detecting an operating direction and an operation amount of the first operating member, and a second operated by the operator to operate the second hydraulic actuator. An operation determining means for determining whether or not the second operating member is operated, a rotation detecting means for detecting a rotation direction and an actual rotational speed of the electric motor, and a control for controlling the electromagnetic valve and the electric motor. And the hydraulic motor and the electric motor rotate the motor when driving the hydraulic pump via a clutch device capable of transmitting torque only from the hydraulic motor to the electric motor. The electric motor is mechanically coupled to rotate in the same direction as the direction by the torque generated by the hydraulic motor when the hydraulic motor is operated, and the electromagnetic valve is connected to the hydraulic pressure from the first hydraulic actuator. It can be switched between a recovery state that allows the flow of hydraulic oil toward the motor and a supply state that blocks the flow, and its opening can be changed until it is fully opened in the recovery state. The control means is configured so that when the operation direction of the first operation member is a direction corresponding to the recovery of the hydraulic oil from the first hydraulic actuator, and the second operation member is not operated, The electromagnetic valve is controlled to be fully opened in the recovery state, the instruction rotational speed of the electric motor is determined based on the operation amount, the electric motor is controlled to rotate at the instruction rotational speed, If there is an operation of the second operating member, an instruction opening degree of the electromagnetic valve is determined based on the operation amount, the electromagnetic valve is controlled so as to become the instruction opening degree in the recovery state, and a predetermined rotation The electric motor is controlled to rotate by a number.

According to such a hydraulic system, the hydraulic motor is actuated (rotated) with return oil from the first hydraulic actuator, torque is transmitted from the hydraulic motor to the electric motor via the clutch device, and the electric motor is rotated. it can. Accordingly, when the second operating member is not operated at this time and it is not necessary to supply hydraulic oil to the second hydraulic actuator, the control unit can regenerate the electric motor to recover energy. When the second operating member is operated and hydraulic oil is supplied to the second hydraulic actuator, the electric pump is driven by controlling the power of the electric motor, but the torque from the hydraulic motor can be used as the assist torque. Energy consumption for rotating the motor by the amount can be suppressed.
When the second operating member is not operated, the motor rotates at the indicated rotational speed determined based on the operating amount of the first operating member after the electromagnetic valve is fully opened. In addition, the first hydraulic actuator can be operated at a desired operation speed, and the efficiency in the case of regenerative control of the electric motor is increased. When the second operating member is operated, the electromagnetic valve is opened at the indicated rotational speed determined based on the operating amount of the first operating member. In this case as well, a desired operation corresponding to the operating amount is performed. The first hydraulic actuator can be operated at speed.
In addition, although a hydraulic motor is provided separately from the hydraulic pump, the motor can be used as a generator by controlling the regeneration, so less space is required for installation than when a generator is provided separately from the motor, and the weight Can be suppressed to some extent.
In addition, since torque transmission from the electric motor to the hydraulic motor is not performed by the clutch device, it is possible to rotate the electric motor at a speed equal to or higher than the number of rotations by the torque from the hydraulic motor, and to the second hydraulic actuator, the desired oil Quantity can be supplied.

  In the above configuration, the control means operates the second operating member when the operating direction of the first operating member is a direction corresponding to the supply of hydraulic oil to the first hydraulic actuator. If there is no, the electromagnetic valve is controlled to be in the supply state, the electric motor is controlled to rotate at a first predetermined rotational speed set corresponding to the first hydraulic actuator, and the second When the operation member is operated, the electromagnetic valve is controlled so as to be in the supply state, and the second predetermined rotation set in correspondence with the first predetermined rotation speed and the second hydraulic actuator. The electric motor can be controlled so as to rotate at a predetermined rotational speed having a smaller value among the numbers.

  In this way, when supplying hydraulic oil only to the first hydraulic actuator, the electric motor rotates at the first predetermined rotation speed, so that a desired amount of oil can be supplied. In addition, even when the first predetermined rotation speed and the second predetermined rotation speed are different when supplying hydraulic oil to the first and second hydraulic actuators at the same time, the electric motor is operated at a predetermined rotation speed with a smaller value. Rotates. Therefore, it is possible to prevent excessive supply of hydraulic oil to one side.

  In the above configuration, the control means may be configured such that when the operation direction of the first operation member is a direction corresponding to the recovery of the hydraulic oil from the first hydraulic actuator, If the actual rotational speed of the electric motor is less than or equal to a predetermined value, the instruction opening of the electromagnetic valve is determined based on the operation amount, and the instruction opening is set to the instruction opening in the recovered state. The electromagnetic valve is controlled so that the electric motor can freely rotate.When the electric motor exceeds the predetermined value, the electromagnetic valve is controlled to be fully opened in the recovery state, and based on the operation amount, the electromagnetic valve is controlled. The designated rotational speed of the electric motor is determined, and the electric motor can be controlled to rotate at the designated rotational speed.

  In this way, when recovering the hydraulic oil from the first hydraulic actuator, the second operating member is not operated, and the actual rotational speed of the motor is a predetermined value (for example, battery charging by regenerative control is not possible). If the rotation speed is less than or equal to the upper limit value), the electromagnetic valve is opened at the indicated rotation speed determined based on the operation amount of the first operation member, and if not, the operation amount of the first operation member The motor rotates at the indicated rotational speed determined based on the above. Therefore, the first hydraulic actuator can be operated at a desired operation speed corresponding to the operation amount regardless of whether or not the actual rotational speed of the electric motor is equal to or less than a predetermined value. In particular, when the predetermined value is the upper limit value of the rotation speed that cannot be regenerated, the motor is reliably regeneratively controlled at the rotation speed that can be regenerated, and the speed that is controlled even if regeneration is impossible. Thus, the first hydraulic actuator can be operated.

  In order to achieve the above object, a forklift according to the present invention is a forklift provided with the hydraulic system according to the present invention, wherein the first hydraulic actuator is a hydraulic pressure that operates a fork provided to be movable up and down. The cylinder is extended by supplying hydraulic oil to raise the fork, and is shortened by collecting hydraulic oil to lower the fork.

  According to such a forklift, the fork can be raised at a desired rising speed, and the fork can be lowered at a desired lowering speed. Further, when the fork is lowered, the hydraulic motor can be operated with the return oil from the hydraulic cylinder, and the electric motor can be rotated with the torque from the hydraulic motor. Therefore, the electric motor can be regeneratively controlled to recover energy, or the torque from the hydraulic motor can be used as an assist torque for the power running control of the electric motor. Thus, since the efficiency of the hydraulic system is good, the efficiency of the forklift as a whole can be increased.

  As described above, according to the hydraulic system according to the present invention, the hydraulic motor can be operated by the return oil from the first hydraulic actuator to rotate the electric motor. It can be recovered. In particular, when the second operating member is not operated, the electromagnetic valve is fully opened and the return oil from the first hydraulic actuator is supplied to the hydraulic motor, so that the efficiency when the electric motor is regeneratively controlled is increased.

  Further, according to the forklift according to the present invention, the fork can be raised and lowered at a desired speed, and the electric motor can be rotated by operating the hydraulic motor with the return oil from the hydraulic cylinder when the fork is lowered. Therefore, the efficiency of the forklift as a whole is increased.

  Hereinafter, an embodiment in which the present invention is applied to a counterbalance forklift (hereinafter simply referred to as a forklift) will be described with reference to the drawings.

As shown in FIG. 1, the forklift according to the first embodiment includes a mast 2 supported at the front portion of a vehicle body 1 so as to be tiltable back and forth, and a fork 3 is supported on the mast 2 so as to be movable up and down. Has been. The mast 2 is provided with a lift cylinder 4 for raising and lowering the fork 3, and a tilt cylinder 5 for tilting the mast 2 between the vehicle body 1 and the mast 2.
The lift cylinder 4 is composed of a single-acting single rod type hydraulic cylinder, which extends when the hydraulic oil is supplied and raises the fork 3, and shortens and lowers the fork 3 when the hydraulic oil is recovered. The tilt cylinder 5 is composed of a double-acting single rod type hydraulic cylinder. When the tilt cylinder 5 is extended, the mast 2 is tilted forward (inclined forward) with respect to the vehicle body 1, and when it is shortened, the mast 2 is moved rearward with respect to the vehicle body 1. Tilt (backward tilt) is made. The hydraulic system in the forklift is a general term for various devices and controls related to expansion and contraction of both cylinders including the lift cylinder 4 and the tilt cylinder 5.

  As shown in FIG. 1, a battery 6 is provided at the center in the front-rear direction of the vehicle body 1, and a driver seat 7 on which a driver sits is provided on a cover that covers the upper side of the battery 6. . A handle, lever, and switches for driving the forklift are provided at a position facing the driver's seat 7 at the front of the vehicle body 1, and a lift lever 8 for raising and lowering the fork 3 among these, There is a tilt lever 9 for tilting the mast 2. Both levers are provided so as to be able to swing in the driver's front and back directions, the lift lever 8 is provided with an angle sensor 8a for detecting an operation angle, and the tilt lever 9 is turned on when operated. A switch 9a is attached.

  The angle sensor 8a detects the angle of the lift lever 8 with reference to a predetermined position, and the detection result is input to the control device 10 provided at the rear position of the battery 6, and the motor 13 described later is provided by the control device 10. And the lift valve 17 is controlled. The switch 9a is turned on when the tilt lever 9 is operated at a predetermined angle or more in either the direction in which the mast 2 is tilted forward (the driver's back direction) or the direction in which the tilt lever 9 is tilted backward (the driver's front direction). The signal from the switch 9 a is also input to the control device 10.

  Now, the hydraulic device provided in the vehicle body 1 in this forklift mainly includes a tank 11 for storing hydraulic oil, a hydraulic pump 12, an electric motor 13 mechanically connected to the hydraulic pump 12, a hydraulic motor 14, It comprises a one-way clutch 15 that connects the hydraulic motor 14 and the electric motor 13, a control valve 16 and a lowering valve 19 that control the flow of hydraulic oil, and hydraulic piping that connects the devices.

  As shown in FIG. 1, the tank 11 is provided at a front position of the battery 6 and stores hydraulic oil to be supplied to the lift cylinder 4 and the tilt cylinder 5. An electric motor 13 that is electrically connected to the battery 6 via the control device 10 is provided at a side position of the tank 11, and power is supplied from the battery 6 to the electric motor 13 when the electric power control is performed on the electric motor 13. When the electric motor 13 is regeneratively controlled, electric power is supplied from the electric motor 13 to the battery 6.

As shown in FIG. 2, a hydraulic pump 12 is connected to one end of the rotating shaft of the electric motor 13 and sucks and pressurizes hydraulic oil from the tank 11, and the other end is connected via a one-way clutch 15. A hydraulic motor 14 driven by receiving hydraulic oil is connected. Here, the one-way clutch 15 is connected to the rotating shaft of the electric motor 13 and the rotating shaft of the hydraulic motor 14, and can transmit torque in only one direction from the hydraulic motor 14 to the electric motor 13. In contrast, the engine rotates idly and torque is not transmitted to the hydraulic motor 14.
The rotation direction of the electric motor 13 when driving the hydraulic pump 12 and the rotation direction of the electric motor 13 when rotating by the torque from the hydraulic motor 14 are made to coincide. The electric motor 13 has a built-in rotation sensor 13a for detecting the rotation direction and the number of rotations, and a signal from the rotation sensor 13a is input to the control device 10.

  The control valve 16 includes an ascending valve 17 that controls the flow of hydraulic oil for the lift cylinder 4 and a tilt valve 18 that controls the flow of hydraulic oil for the tilt cylinder 5, and is provided at the front portion of the vehicle body 1. . As shown in FIG. 2, the control valve 16 is connected to the tank 11 via a supply pipe A and a recovery pipe E, and the lift cylinder 4 is connected to a tilt cylinder 5 via a supply pipe B and a common pipe C. And are connected via common pipes F and G. The lowering valve 19 is connected to the tank 11 via a recovery pipe D, and is connected to the lift cylinder 4 via a dual-purpose pipe C and a recovery pipe D.

  The supply pipe A is a hydraulic pipe for supplying hydraulic oil from the tank 11 to the control valve 16, and a hydraulic pump 12 is provided in the supply pipe A. The hydraulic oil from the hydraulic pump 12 is supplied to both the ascending valve 17 and the tilt valve 18. The supply pipe B is a hydraulic pipe for supplying hydraulic oil to the lift cylinder 4 via the lift valve 17, and the dual-use pipe C is connected to the supply pipe B, and the operation from the lift valve 17 is performed. The oil is supplied to the lift cylinder 4 through the supply pipe B and the common pipe C. A recovery pipe D is also connected to a connection portion between the supply pipe B and the dual-purpose pipe C. The recovery pipe D is a hydraulic pipe for recovering the hydraulic oil from the lift cylinder 4 to the tank 11, and the hydraulic oil from the lift cylinder 4 is recovered to the tank 11 through the dual-purpose pipe C and the recovery pipe D. The recovery pipe D is provided with a hydraulic motor 14. The recovery pipe E is a hydraulic pipe for recovering hydraulic oil to the tank 11 via the tilt valve 18. The dual-purpose pipes F and G are hydraulic pipes for supplying hydraulic oil to the tilt cylinder 5 via the tilt valve 18 and collecting the hydraulic oil from the tilt cylinder 5. As shown in FIG. 2, the dual-purpose pipe F is connected to the rod side of the tilt cylinder 5, and the dual-purpose pipe G is connected to the bottom side of the tilt cylinder 5.

  As shown in FIG. 2, the lift valve 17 communicates the supply pipe A and the supply pipe B, allows the hydraulic oil to flow from the hydraulic pump 12 to the lift cylinder 4, and the lift cylinder 4 Is a manually operated valve that can be switched between a lowered position where hydraulic fluid is not supplied to and recovered from the lift cylinder 4 and a neutral position where the hydraulic oil is also disconnected from the lift cylinder 4. And mechanically connected. The lift valve 17 is switched to the raised position when the driver operates the lift lever 8 in the forward direction, and is switched to the lowered position when the driver operates the lift lever 8 in the backward direction. It is returned to the neutral position by the built-in spring.

  As shown in FIG. 2, the lowering valve 19 is in a raised position that prevents the flow of hydraulic oil from the lift cylinder 4 to the hydraulic motor 14, and the lowering that allows the flow of hydraulic oil from the lift cylinder 4 to the hydraulic motor 14. It is an electromagnetic proportional control valve that can be switched to a position. The lowering valve 17 is switched to the lowered position when the built-in solenoid is excited, and is returned to the raised position by the built-in spring when the excitation of the solenoid is stopped. The opening at the lowered position can be changed by adjusting the excitation current to the solenoid, and the opening can be increased as the excitation current is increased.

  As shown in FIG. 2, the tilt valve 18 is a manually operated valve that can be switched between a forward tilt position, a rear tilt position, and a neutral position where hydraulic oil is not supplied to the tilt cylinder 5 and is not collected. The lever 9 is mechanically connected. In the forward inclined position, the supply pipe A and the dual-purpose pipe G are communicated to allow the hydraulic oil to flow from the hydraulic pump 12 to the bottom side of the tilt cylinder 5, and the recovery pipe E and the dual-purpose pipe F are communicated. The flow of hydraulic oil from the rod side of the tilt cylinder 5 to the tank 11 is allowed. In the rearward tilt position, the supply pipe A and the dual-purpose pipe F are communicated to allow the hydraulic oil to flow from the hydraulic pump 12 to the rod side of the tilt cylinder 5, and the recovery pipe E and the dual-purpose pipe G are communicated. Thus, the flow of hydraulic oil from the bottom side of the tilt cylinder 5 to the tank 11 is allowed. The tilt valve 18 is switched to the forward tilt position when the driver operates the tilt lever 9 in the rearward direction, and is switched to the rearward tilt position when the driver operates the tilt lever 9 in the forward direction. When stopped, it is returned to the neutral position by a built-in spring.

As shown in FIG. 3, the control device 10 includes a lift operation detection unit 101, a tilt operation detection unit 102, and a control unit 103 that controls the electric motor 13 and the lowering valve 19.
In the first embodiment, when the lift lever 8 is lowered, the lowering valve 19 or the electric motor 13 is controlled as described later, but the lowering speed Vd of the fork 3 and the instruction of the lowering valve 19 are controlled. The relationship between the opening degree M and the relationship between the descending speed Vd of the fork 3 and the command rotational speed N of the electric motor 13 is as shown in FIG. That is, both are in a proportional relationship, and when the command opening degree M is the maximum value Mmax, the descending speed Vd is also the maximum value Vdmax, and when the command rotational speed N is the maximum value Nmax, the descending speed Vd is also the maximum value Vdmax. Become. The descending speed Vd becomes a certain value Vt (0 <Vt <Vdmax) when the commanded opening degree M = Mt (0 <Mt <Mmax) or the commanded rotational speed N = Nt (0 <Nt <Nmax). )

The lift operation detection unit 101 determines the lift lever operation amount L and the operation direction of the lift lever 8 from the angle of the lift lever 8 detected by the angle sensor 8 a, and the result is transmitted to the control unit 103.
That is, the lift operation detecting unit 101 sets the difference between the angle detected by the angle sensor 8a and the angle at the neutral position of the lift lever 8 as the lift lever operation amount L, and when the lift lever 8 is in the neutral position, the lift lever operation is performed. When the amount L = 0 and the lift lever 8 is at the position where the lift lever 8 has been operated to the limit in the front or back direction of the driver, the lift lever operation amount L = Lmax. If the angle detected by the angle sensor 8a is larger than the angle at the neutral position of the lift lever 8, the operation direction of the lift operation detection unit 101 is the direction in which the fork 3 is raised (the direction toward the driver). If it is determined that the operation direction is smaller, it is determined that the operation direction is a direction in which the fork 3 is lowered (a driver's back direction).
In order to provide a dead zone near the neutral position of the lift lever 8, the operation direction is determined when the lift lever operation amount L is equal to or greater than the predetermined value L1, and the lift operation detection unit 101 detects the lift lever operation amount L. Is less than the predetermined value L1, it is determined that the lift lever 8 is not operated.

  The tilt operation detection unit 102 receives a signal from the switch 9a, and determines that the tilt lever 9 is operated if the switch 9a is on, and determines that the tilt lever 9 is not operated if the switch 9a is off. Then, the result is transmitted to the control unit 103.

The control unit 103 controls the lowering valve 19 based on the determination result in the lift operation detection unit 101 and the determination result in the tilt operation detection unit 102.
In other words, if the operation direction of the lift lever 8 is a direction in which the fork 3 is lifted (lifting operation), the solenoid of the lowering valve 19 is not excited and maintained in the raised position. If the operation direction of the lift lever 8 is a direction for lowering the fork 3 (down operation), when the tilt lever 9 is operated, the control unit 103 determines the instruction opening M as shown in FIG. The lowering valve 19 is controlled. That is, if the lift lever operation amount L ≧ L1, the instruction opening degree M proportional to the lift lever operation amount L is calculated, and the solenoid of the lowering valve 19 is excited so as to reach the instruction opening degree M. When the tilt lever 9 is not operated, the control unit 103 determines the instruction opening M and controls the lowering valve 19 as shown in FIG. That is, if the lift lever operation amount L ≧ L1, the instruction opening M = Mmax is set, and the solenoid of the lowering valve 19 is excited so as to be fully opened.

Further, the control unit 103 determines the instruction rotation speed N based on the determination result in the lift operation detection unit 101 and the determination result in the tilt operation detection unit 102, and the actual rotation number from the rotation sensor 13a is determined as the instruction rotation number. Power running control or regenerative control of the electric motor 13 is performed so as to coincide with N.
That is, if the lift lever 8 is lifted up alone, as shown in FIG. 7, the control unit 103 sets the indicated rotational speed N = N1 if the lift lever operation amount L ≧ L1, and the actual rotational speed is the rotational speed. The electric motor 13 is subjected to power running control so as to be N1. If the tilt lever 9 is operated simultaneously with the lift operation of the lift lever 8, the rotation speed N1 corresponds to the lift operation, and the rotation speed N2 (<N1) corresponds to the tilt operation. Is used, and the motor 13 is subjected to power running control so that the actual rotational speed becomes the rotational speed N2.
If the lift lever 8 is operated to be lowered alone, as shown in FIG. 8, the control unit 103 calculates an instruction rotational speed N that is proportional to the lift lever operation amount L, and the actual rotational speed is the instruction rotational speed N. The electric motor 13 is regeneratively controlled. If the tilt lever 9 is operated simultaneously with the lowering operation of the lift lever 8, the control unit 103 controls the electric motor 13 to perform the power running so that the designated rotational speed N = N2 and the actual rotational speed becomes the rotational speed N2. Similarly, if the tilt lever 9 is operated alone, the control unit 103 performs power running control at the rotation speed N2.

  Hereinafter, the control flow in the first embodiment will be further described.

  As shown in FIG. 9, the control unit 103 first determines whether or not the lift lever 8 is lifted (S1). If the lift lever 8 is lifted, whether or not the tilt lever 9 is touched. Is determined (S2). If the tilt lever 9 is not operated, the control unit 103 performs power running control of the electric motor 13 at the rotation speed N1 (S3). By doing so, the fork 3 is raised in accordance with the operation of the lift lever 8. If the tilt lever 9 is operated in S2, the control unit 103 performs power running control of the electric motor 13 at the rotation speed N2 (S4). By doing so, although the speed is slower than when the tilt lever 9 is not operated, the fork 3 rises according to the operation of the lift lever 8 and the mast 2 tilts according to the operation of the tilt lever 9. .

  If the lift lever 8 is not lifted in S1, as shown in FIG. 9, the controller 103 determines whether or not the lift lever 8 is lowered (S5). Then, it is determined whether or not the tilt lever 9 is operated (S6). If the tilt lever 9 has been operated, the control unit 103 calculates the command opening M based on the lift lever operation amount L (S7), and excites the solenoid with the excitation current corresponding to the command opening M for descending. The valve 19 is opened (S8). Further, the control unit 103 controls the power running of the electric motor 13 at the rotation speed N2 (S4). By doing so, the fork 3 descends at the descending speed Vd corresponding to the lift lever operation amount L, and the mast 2 tilts according to the operation of the tilt lever 9. At this time, the torque generated by the hydraulic motor 14 due to the return oil from the lift cylinder 4 acts as an assist torque on the electric motor 13, so that the power consumption can be suppressed compared to the case where the electric motor 13 is simply power-running at the rotational speed N2. . If the tilt lever 9 is not operated in S6, the controller 103 excites the solenoid and fully opens the lowering valve 17 at the lowered position (S9). Next, the control unit 103 calculates an instruction rotation speed N based on the lift lever operation amount L (S10), and regeneratively controls the motor 13 at the instruction rotation speed N (S11). By doing so, the fork 3 is lowered at the lowering speed Vd corresponding to the lift lever operation amount L, and the battery 6 is charged with the electric power generated by the electric motor 13.

  When the lowering operation of the lift lever 8 is not performed in S5, that is, when the lift lever 8 is not operated, the control unit 103 determines whether or not the tilt lever 9 is operated as shown in FIG. (S12) If the tilt lever 9 has been operated, the motor 13 is subjected to power running control at the rotational speed N2 (S4). By doing so, the mast 2 tilts according to the operation of the tilt lever 9, but there is no torque transmitted from the hydraulic motor 14 to the electric motor 13, and electric power is consumed by the electric motor 13 as usual.

According to the first embodiment described above, when the lift lever 8 is lowered, the hydraulic motor 14 is operated by the return oil from the lift cylinder 4, and the electric motor 13 is rotated by the torque from the hydraulic motor 14. Can do. At this time, if the tilt lever 9 is operated, the hydraulic pump 12 is driven by controlling the power running of the electric motor 13, but the electric motor 13 is rotated by the amount that the torque from the hydraulic motor 14 can be used. Power consumption can be reduced. Further, since the opening degree of the lowering valve 19 is controlled according to the operation amount L of the lift lever 8, the driver can lower the fork 3 at a desired lowering speed Vd.
On the other hand, if the tilt lever 9 is not operated, the electric motor 13 can be regeneratively controlled to charge the battery 6. Here, since the lowering valve 19 is fully opened, all the return oil from the lift cylinder 4 can be supplied to the hydraulic motor 14, and the regeneration efficiency is improved. Further, since the rotational speed of the electric motor 13 is controlled according to the operation amount L of the lift lever 8, the driver can lower the fork 3 at a desired lowering speed Vd.
Of course, when the lift lever 8 is lifted, the opening degree of the lift valve 17 is adjusted according to the operation of the lift lever 8, so that the driver can lift the fork 3 at a desired lift speed. .

  Further, according to the first embodiment, since the electric motor 13 is used as a generator, the installation space is less than when a generator is provided separately from the electric motor 13, and the weight of the entire hydraulic device provided in the vehicle body 1 is reduced. Can also be kept relatively light. Further, since torque transmission from the electric motor 13 to the hydraulic motor 14 is not performed by the one-way clutch 15, the torque from the hydraulic motor 14 is small when the lowering operation of the lift lever 8 and the operation of the tilt lever 9 are performed simultaneously. Even in this case, the electric motor 13 can be reliably rotated at the rotation speed N2, and thus the rotation of the hydraulic motor 14 is not affected. Accordingly, the working oil can be supplied to the tilt cylinder 5 with a desired amount of oil, and the mast 2 can be tilted.

  In the first embodiment, when the lift lever 8 is lowered, and the tilt lever 9 is not operated, the fork is controlled at the lowering speed Vd corresponding to the operation of the lift lever 8 by controlling the rotation speed of the electric motor 13. However, in the second embodiment, the control of the opening degree of the lowering valve 19 and the control of the rotational speed of the electric motor 13 are performed in combination. Hereinafter, the second embodiment will be described, but the other configurations are the same as those of the first embodiment, and the description thereof will be omitted.

The control unit 103 of the control device 10 is not able to charge the battery 6 when the lift lever 8 is operated alone to lower the actual rotation number from the rotation sensor 13a to a predetermined rotation number Nt (for example, by regeneration control of the electric motor 13). It is determined whether or not it is equal to or less than the upper limit value). If the actual rotational speed exceeds the rotational speed Nt, the control unit 103 sets the instruction opening M = Mmax, excites the solenoid of the descending valve 19 so as to be fully opened, and indicates an instruction proportional to the lift lever operation amount L. The rotational speed N is calculated, and the electric motor 13 is regeneratively controlled so that the actual rotational speed becomes the indicated rotational speed N. If the actual rotational speed is equal to or lower than the rotational speed Nt, the control unit 103 calculates an instruction opening degree M proportional to the lift lever operation amount L, and excites the solenoid of the lowering valve 19 so as to become the instruction opening degree M. The motor 13 is not controlled and the motor 13 is in a freely rotatable state.
That is, assuming that the lift lever operation amount corresponding to the case where the rotation speed Nt is set to the designated rotation speed N is Lt, the control unit 103 determines that the lift lever operation amount L is L1 ≦ L ≦ Lt as shown in FIG. For example, the instruction opening degree M proportional to the lift lever operation amount L is calculated, and if the lift lever operation amount L> Lt, the instruction opening degree M = Mmax. In addition, as shown in FIG. 11, the control unit 103 sets the indicated rotational speed N = 0 (no control) if the lift lever operation amount L is L1 ≦ L ≦ Lt, and if the lift lever operation amount L> Lt. An instruction rotation speed N proportional to the lift lever operation amount L is calculated.

  Hereinafter, the control flow in the second embodiment will be further described. The case where the lift lever 8 is raised is the same as in the first embodiment, and the description thereof is omitted.

  As shown in FIG. 12, if the lift lever 8 is not lifted in S1, the control unit 103 determines whether or not the lift lever 8 is lowered (S5). Then, it is determined whether or not the tilt lever 9 is operated (S6). If the tilt lever 9 has been operated, the control unit 103 calculates the command opening M based on the lift lever operation amount L (S7), and excites the solenoid with the excitation current corresponding to the command opening M for descending. The valve 19 is opened (S8). Further, the control unit 103 performs power running control of the electric motor 13 at the rotation speed N2 (S4). By doing so, the fork 3 descends at the descending speed Vd corresponding to the lift lever operation amount L, and the mast 2 tilts according to the operation of the tilt lever 9. At this time, the torque generated by the hydraulic motor 14 due to the return oil from the lift cylinder 4 acts as an assist torque on the electric motor 13, so that the power consumption can be suppressed compared to the case where the electric motor 13 is simply power-running at the rotational speed N2. .

  If the tilt lever 9 is not operated in S6, as shown in FIG. 12, the controller 103 determines whether or not the actual rotational speed of the motor 13 exceeds the rotational speed Nt, that is, the actual rotational speed> the rotational speed Nt. It is determined whether or not there is (S9). If the actual rotational speed> the rotational speed Nt, the solenoid is excited and the lowering valve 17 is fully opened at the lowered position (S10). Further, the control unit 103 calculates an instruction rotational speed N based on the lift lever operation amount L (S11), and regeneratively controls the electric motor 13 at the instruction rotational speed N (S12). If the actual rotational speed is not greater than the rotational speed Nt in S9, the control unit 103 calculates the instruction opening degree M based on the lift lever operation amount L (S13), and excites the solenoid with the excitation current corresponding to the instruction opening degree M. The lowering valve 19 is opened (S14). By so doing, if the actual rotational speed> the rotational speed Nt and charging by regeneration is possible, the fork 3 descends at the descending speed Vd corresponding to the lift lever operation amount L, and the electric power generated by the electric motor 13 The battery 6 is charged. Further, even if the actual rotational speed> the rotational speed Nt and charging by regeneration is impossible, the fork 3 descends at the descending speed Vd corresponding to the lift lever operation amount L.

  If the lift lever 8 is not lowered in S5, that is, if the lift lever 8 is not operated at all, the control unit 103 determines whether or not the tilt lever 9 is operated as shown in FIG. Is determined (S15). If the tilt lever 9 is operated, the control unit 103 performs power running control of the electric motor 13 at the rotation speed N2 as in the first embodiment (S4).

  According to the second embodiment described above, the effects of the first embodiment can be obtained, and when only the lowering operation of the lift lever 8 is performed, the actual rotational speed of the motor 13 is relatively small, that is, the lowering. Even when the speed Vd is relatively slow, the opening degree of the lowering valve 19 is controlled according to the operation amount L of the lift lever 8, so that the driver lowers the fork 3 at a desired lowering speed Vd. Can do. In particular, by setting the rotational speed Nt to the upper limit value of the rotational speed at which the battery 6 cannot be charged, when the actual rotational speed> the rotational speed Nt and regeneration is possible, the descending valve 19 is fully opened and the electric motor 13 is regenerated. Since it is controlled, the battery 6 can be charged reliably and efficiently.

It is a side view of the forklift which concerns on Example 1, 2 of this invention. 1 is a hydraulic circuit diagram according to first and second embodiments of the present invention. It is a functional block diagram concerning Example 1 of the present invention. It is a control characteristic figure in Example 1, 2 of this invention, and has shown the relationship between descent | fall speed, the valve | bulb for descent | fall, and the rotation speed of an electric motor. It is a control characteristic figure of the valve for descent in Example 1 of the present invention. It is a control characteristic figure of the valve for descent in Example 1 of the present invention. It is a control characteristic figure of the electric motor in Example 1 of the present invention. It is a control characteristic figure of the electric motor in Example 1 of the present invention. It is a control flow figure in Example 1 of the present invention. It is a control characteristic figure of the valve for descent in Example 2 of the present invention. It is a control characteristic figure of the electric motor in Example 2 of the present invention. It is a control flow figure in Example 2 of the present invention.

Explanation of symbols

3 Fork 4 Lift cylinder 5 Tilt cylinder 6 Battery 8 Lift lever 8a Angle sensor 9 Tilt lever 9a Switch 10 Controller 11 Tank 12 Hydraulic pump 13 Electric motor 13a Rotation sensor 14 Hydraulic motor 15 One-way clutch 16 Control valve 17 Lifting valve 19 Lowering Valve A supply piping (shared)
B Supply piping (for lift)
C Combined piping (for lift)
D Recovery piping (for lift)
E Recovery piping (for tilt)
F Combined piping (for tilt)
G Combined piping (for tilt)

Claims (4)

An electric motor is mechanically connected to a first supply hydraulic pipe for supplying the hydraulic oil from a tank for storing the hydraulic oil to the first hydraulic actuator, and is driven by the electric motor to draw in the hydraulic oil from the tank. A hydraulic pump for discharging toward the first hydraulic actuator is provided, and the hydraulic oil from the first hydraulic actuator is connected to a first recovery hydraulic pipe for recovering the hydraulic oil from the first hydraulic actuator to the tank. A hydraulic motor that operates by being supplied, and further, a second supply hydraulic pipe for supplying hydraulic oil from the hydraulic pump to the second hydraulic actuator, and an operation from the second hydraulic actuator to the tank A hydraulic system including a second recovery hydraulic pipe for recovering oil,
An electromagnetic valve provided in the first recovery hydraulic pipe for controlling the flow of hydraulic oil between the first hydraulic actuator and the hydraulic motor, and an operator for operating the first hydraulic actuator A first operation member operated by the operator, an operation detection means for detecting an operation direction and an operation amount of the first operation member, and a second operation operated by an operator to operate the second hydraulic actuator. A member, an operation determining means for determining whether or not the second operating member is operated, a rotation detecting means for detecting a rotation direction and an actual rotational speed of the electric motor, a control means for controlling the electromagnetic valve and the electric motor, With
The hydraulic motor and the electric motor operate in the same direction as the rotation direction of the electric motor when the hydraulic pump is driven via a clutch device capable of transmitting torque only from the hydraulic motor to the electric motor. The motor is mechanically connected to rotate by torque generated by the hydraulic motor when
The electromagnetic valve can be switched between a recovery state that allows the flow of hydraulic oil from the first hydraulic actuator to the hydraulic motor and a supply state that blocks the flow, and is fully opened in the recovery state. The opening can be changed between
If the operation direction of the first operating member is a direction corresponding to the recovery of the hydraulic oil from the first hydraulic actuator, the control means may return the recovery if there is no operation of the second operating member. Controlling the electromagnetic valve to be fully open in a state, determining an instruction rotational speed of the electric motor based on the operation amount, controlling the electric motor to rotate at the instruction rotational speed, and performing the second operation If there is an operation of the member, the instruction opening of the electromagnetic valve is determined based on the operation amount, and the electromagnetic valve is controlled so as to become the instruction opening in the recovered state, and is rotated at a predetermined rotational speed. A hydraulic system characterized by controlling the electric motor.   If the operation direction of the first operation member is a direction corresponding to the supply of hydraulic oil to the first hydraulic actuator, the control means may supply the supply if there is no operation of the second operation member. The electromagnetic valve is controlled to be in a state, the electric motor is controlled to rotate at a first predetermined rotational speed set corresponding to the first hydraulic actuator, and the second operating member is operated. If present, the electromagnetic valve is controlled so as to be in the supply state, and a value is selected from the first predetermined rotation speed and the second predetermined rotation speed set corresponding to the second hydraulic actuator. 2. The hydraulic system according to claim 1, wherein the electric motor is controlled to rotate at a predetermined rotation speed of a smaller one. When the operation direction of the first operation member is a direction corresponding to the recovery of the hydraulic oil from the first hydraulic actuator, the control means, if there is no operation of the second operation member,
When the actual rotational speed of the electric motor is less than or equal to a predetermined value, the instruction opening of the electromagnetic valve is determined based on the operation amount, and the electromagnetic valve is controlled so as to become the instruction opening in the recovered state. To allow the motor to rotate freely,
When the predetermined value is exceeded, the electromagnetic valve is controlled so as to be fully opened in the recovery state, and the indicated rotational speed of the electric motor is determined based on the manipulated variable so as to rotate at the indicated rotational speed. The hydraulic system according to claim 1, wherein the hydraulic system controls the electric motor.   The first hydraulic actuator is a hydraulic cylinder that operates a fork provided so as to be movable up and down. The hydraulic cylinder is extended when hydraulic oil is supplied to elevate the fork, and is shortened when hydraulic oil is collected. 4. A forklift equipped with a hydraulic system according to claim 1, wherein the fork is lowered.

Images