JP5831263B2 - Hydraulic control device for forklift - Google Patents

Description

  The present invention relates to a hydraulic control device for a forklift, and more particularly to a hydraulic control device for controlling a hydraulic cylinder.

  Conventionally, in a forklift, a hydraulic cylinder is employed as a mechanism for operating a cargo handling member such as a fork or a mast. For example, in the hydraulic device of Patent Document 1, a lift cylinder for operating a fork and a tilt cylinder for operating a mast are connected to a hydraulic pump, and hydraulic oil is supplied from the hydraulic pump to these cylinders. The fork and mast are operated.

JP 2006-124145 A

  By the way, in a hydraulic device in which a hydraulic pump is connected to a plurality of cylinders, when the fork operation and the mast operation are performed independently, the electric motor is controlled in accordance with the instructed speed in order to operate the operation target. Thus, the operation target can be operated at the indicated speed. However, in the above hydraulic device, when the fork operation and the mast operation are performed simultaneously, the motor is controlled in accordance with the instructed speed in order to operate either one of the operation objects. It was difficult to operate at the indicated speed.

  The present invention has been made paying attention to such problems existing in the prior art, and its purpose is to make each operation target operate well when operating a plurality of operation objects simultaneously. An object of the present invention is to provide a hydraulic control device for a forklift.

In order to solve the above-described problems, the invention according to claim 1 is a first hydraulic cylinder that raises or lowers a fork by supplying and discharging hydraulic oil by operating a lifting instruction member, and a cargo handling instruction member. A hydraulic control device for a forklift, comprising: a second hydraulic cylinder that carries out a cargo handling operation of another cargo handling member by supplying and discharging hydraulic oil by an operation of the first hydraulic cylinder and the second hydraulic cylinder A hydraulic pump motor connected to the hydraulic oil via a supply oil path, a first oil path for flowing the hydraulic oil discharged from the first hydraulic cylinder to the hydraulic pump motor, and the first A second oil passage through which hydraulic oil discharged from the hydraulic cylinder flows to the drain side, an electromagnetic switching valve disposed in the first oil passage, and an electromagnetic ratio disposed in the second oil passage A control unit that controls a flow rate of hydraulic oil that flows through the solenoid switching valve and the electromagnetic proportional valve, and the control unit is configured to perform the elevation instruction when the fork is lowered by a single operation. Controlling the flow rate of the electromagnetic switching valve so that the flow rate of hydraulic oil corresponding to the amount of operation of the member is circulated, to the simultaneous operation of adding the cargo handling operation of the cargo handling member to the fork lowering operation by a single operation In the case of transition, the electromagnetic switching valve and the electromagnetic proportional valve are configured to increase the flow rate of the hydraulic oil flowing through the electromagnetic proportional valve with time and to distribute the hydraulic oil at a flow rate corresponding to the operation amount of the lift instruction member. and controlling the flow rate flowing through the valve, and the flow rate of the hydraulic fluid that flows the hydraulic pump motor via a first oil passage when the transition to the power running from the regeneration to the hydraulic pump motor is And summarized in that for controlling the flow rate of hydraulic fluid flowing through the electromagnetic switching valve so as to.

  According to this, as the oil passage through which the hydraulic oil discharged from the first hydraulic cylinder flows, the first oil passage provided with the electromagnetic switching valve, and the second oil passage provided with the electromagnetic proportional valve Was established. Thereby, when the fork descending operation is performed by a single operation, the regenerative operation can be performed by operating the hydraulic pump motor as a hydraulic motor by controlling the flow rate of the working oil flowing through the electromagnetic switching valve. . On the other hand, in the case where a simultaneous operation for loading and unloading other cargo handling members is performed in addition to the fork lowering operation, the fork lowering operation is controlled by controlling the flow rate of the hydraulic fluid flowing through the electromagnetic switching valve and the electromagnetic proportional valve. It is possible to shift from single operation to simultaneous operation while satisfying the above speed. Therefore, when operating a plurality of operation objects simultaneously, each operation object can be operated favorably.

According to a second aspect of the invention, in the hydraulic control apparatus of a forklift according to claim 1, wherein the electromagnetic switching valve is a proportional solenoid valve, to each of the second oil passage and said first oil passage The gist is that an electromagnetic proportional valve is provided.

  According to this, since the proportional valves are disposed in the first oil passage and the second oil passage, respectively, the target for controlling the flow rate becomes the same proportional valve, and the control becomes easy. That is, it is easy to synchronize the flow rates of both proportional valves, and the control can be simplified.

According to a third aspect of the present invention, in the hydraulic control device for a forklift according to the first aspect , the electromagnetic switching valve is an ON-OFF valve, and the control unit is connected to the hydraulic pump via the ON-OFF valve. The gist is to control the flow rate flowing to the motor. According to this, the cost of an apparatus can be suppressed by making the electromagnetic switching valve arrange | positioned in a 1st oil path into an ON-OFF valve.

According to a fourth aspect of the present invention, in the hydraulic control device for a forklift according to any one of the first to third aspects, the control unit lowers the fork by the single operation from the simultaneous operation. When shifting to, the gist is to control the flow rate through the electromagnetic switching valve and the flow rate through the electromagnetic proportional valve so that the flow rate of the hydraulic oil corresponding to the operation amount of the elevation instruction member is circulated.

  According to this, even in the case of shifting from the simultaneous operation to the single operation, the hydraulic pressure is controlled by controlling the flow rates respectively flowing through the electromagnetic switching valve and the electromagnetic proportional valve as in the case of shifting from the single operation to the simultaneous operation. The regenerative operation can be performed by operating the pump motor as a hydraulic motor.

  According to the present invention, when a plurality of operation objects are operated simultaneously, each operation object can be operated favorably.

The side view of a forklift. 1 is a circuit diagram of a hydraulic control apparatus according to a first embodiment. (A) is explanatory drawing which shows transition of the control flow volume when changing from single operation to simultaneous operation, (b) is explanatory drawing which shows transition of motor rotation speed. (A) is explanatory drawing which shows transition of the control flow volume when changing to simultaneous operation from simultaneous operation, (b) is explanatory drawing which shows transition of motor rotation speed. The circuit diagram of the hydraulic control apparatus of 2nd Embodiment. (A) is explanatory drawing which shows transition of the control flow volume when changing from single operation to simultaneous operation, (b) is explanatory drawing which shows transition of motor rotation speed.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, a body frame 12 of a battery-type forklift 11 is provided with a mast 13 at the front thereof. The mast 13 includes a pair of left and right outer masts 13a supported so as to be tiltable with respect to the vehicle body frame 12, and an inner mast 13b equipped inside the mast 13 so as to be movable up and down. A lift cylinder 14 as a first hydraulic cylinder is fixed to the rear side of both outer masts 13a in parallel with the outer mast 13a, and the tip of the piston rod 14a of the lift cylinder 14 is connected to the upper part of the inner mast 13b.

  A lift bracket 15 is mounted inside the inner mast 13b so as to be movable up and down along the inner mast 13b. A fork 16 is attached to the lift bracket 15. A chain wheel 17 is supported on the upper part of the inner mast 13b, and a chain 18 having a first end connected to the upper part of the lift cylinder 14 and a second end connected to the lift bracket 15 is hung on the chain wheel 17. ing. Then, the fork 16 is moved up and down together with the lift bracket 15 via the chain 18 by the expansion and contraction of the lift cylinder 14.

  A base end of a tilt cylinder 19 as a second hydraulic cylinder is rotatably supported on both the left and right sides of the vehicle body frame 12, and the tip of the piston rod 19a of the tilt cylinder 19 is substantially at the center in the vertical direction of the outer mast 13a. It is connected so that it can rotate. Then, the mast 13 is tilted by the expansion and contraction of the tilt cylinder 19.

  A steering wheel 21, a lift lever 22 as a lift instruction member, and a tilt lever 23 as a cargo handling instruction member are provided at the front of the cab 20. By operating the lift lever 22, the lift cylinder 14 is expanded and contracted and the fork 16 is moved up and down. Further, the tilt cylinder 19 is expanded and contracted by the operation of the tilt lever 23, and the mast 13 is tilted.

  The mast 13 can be tilted between a predetermined last tilt position and a most forward tilt position. When the position of the mast 13 shown in FIG. 1 is a vertical position, an operation that tilts in a direction approaching the cab 20 is a backward tilt operation, and an operation that tilts in a direction away from the cab 20 is a forward tilt operation. In the configuration of the forklift 11 according to the present embodiment, the mast 13 tilts forward when the tilt cylinder 19 operates in the extending direction, while the mast 13 tilts backward when the tilt cylinder 19 operates in the contracting direction.

Hereinafter, the hydraulic control apparatus of this embodiment will be described with reference to FIG.
The hydraulic control device controls operations of the lift cylinder 14 and the tilt cylinder 19. As shown in FIG. 2, the hydraulic control apparatus according to this embodiment includes a mechanism (hydraulic circuit) that operates the lift cylinder 14 and the tilt cylinder 19 by a single pump and a single motor that drives the pump. It is composed. In other words, the hydraulic control apparatus of this embodiment operates a plurality of hydraulic cylinders by a single pump and motor.

  A motor (rotating electrical machine) 31 that functions as an electric motor and a generator is connected to the hydraulic pump motor 30 that functions as a hydraulic pump and a hydraulic motor. In the present embodiment, the motor 31 is an electric motor when the hydraulic pump motor 30 is operated as a hydraulic pump, and is a generator when the hydraulic pump motor 30 is operated as a hydraulic motor. The hydraulic pump motor 30 of the present embodiment is configured to be rotatable in both directions.

  An oil passage for supplying or discharging hydraulic oil is connected to the first inlet / outlet 30 a of the hydraulic pump motor 30. The hydraulic pump motor 30 is connected to the bottom chamber 14b of the lift cylinder 14 via an oil passage. A rising proportional valve 32 that controls the flow rate of the working oil flowing through the oil passage K1 is provided in an oil passage K1 as a supply oil passage for flowing the working oil discharged from the hydraulic pump motor 30 to the bottom chamber 14b of the lift cylinder 14. Is arranged. The ascending proportional valve 32 can take a first position 32a as a closed state that does not allow the flow of hydraulic oil, and a second position 32b that can be arbitrarily changed in its opening degree as an open state. The raising proportional valve 32 is controlled in opening degree in order to adjust the flow rate of the working oil flowing to the bottom chamber 14b when the fork 16 is raised.

  Further, the oil passage K2 serving as the first oil passage through which the hydraulic oil discharged from the bottom chamber 14b of the lift cylinder 14 flows to the first inlet / outlet 30a of the hydraulic pump motor 30 is circulated through the oil passage K2. An electromagnetic switching valve that controls the flow rate of oil and a proportional valve 33 for lowering during regeneration are provided as an electromagnetic proportional valve. The regenerative lowering proportional valve 33 can take a first position 33a as a closed state that does not allow the flow of hydraulic oil, and a second position 33b as an open state in which the opening degree can be arbitrarily changed. The regenerative descending proportional valve 33 has an opening degree for adjusting the flow rate of hydraulic fluid flowing to the hydraulic pump motor 30 side when the hydraulic pump motor 30 performs a regenerating operation in accordance with the descending operation of the fork 16. Be controlled.

  Further, the lift cylinder 14 is connected with an oil passage K3 as a second oil passage through which the hydraulic oil discharged from the bottom chamber 14b flows to the oil tank T on the drain side. The oil passage K3 is provided with a simultaneous operation descending proportional valve 34 as an electromagnetic proportional valve that controls the flow rate of the hydraulic oil flowing through the oil passage K3. The simultaneous operation descending proportional valve 34 can take a first position 34a as a closed state that does not allow the flow of hydraulic oil, and a second position 34b in which the opening degree can be arbitrarily changed as an open state. The simultaneous operation means that the fork 16 is moved up and down and the mast 13 is tilted back and forth, that is, the lift cylinder 14 and the tilt cylinder 19 are operated simultaneously. The opening of the proportional lowering valve 34 during simultaneous operation is controlled in order to adjust the flow rate of the hydraulic oil when the fork 16 and the mast 13 are operated simultaneously.

  An oil passage K4 is connected to the first inflow / outlet port 30a of the hydraulic pump motor 30 as a supply oil passage for flowing hydraulic oil to the bottom chamber 19b or the rod chamber 19r of the tilt cylinder 19. The tilt cylinder 19 is connected to an oil passage K5 through which hydraulic oil discharged from the bottom chamber 19b or the rod chamber 19r flows to the oil tank T. In the oil passages K4 and K5, a tilt proportional valve 35 for controlling the flow rate of the working oil flowing through these oil passages K4 and K5 is disposed. The tilt proportional valve 35 has a first position 35a in a closed state that does not allow the flow of hydraulic oil, a second position 35b in which the opening degree can be arbitrarily changed in the open state, and an opening degree in the open state. And a third position 35c that can be changed to. The tilt proportional valve 35 is controlled in opening degree in order to adjust the flow rate of the working oil flowing to the bottom chamber 19b or the rod chamber 19r when the mast 13 is tilted forward or backward. When the tilt proportional valve 35 is in the second position 35b, the working oil flows into the bottom chamber 19b while the working oil is discharged from the rod chamber 19r, whereby the tilt cylinder 19 extends and the mast 13 tilts forward. Operate. When the tilt proportional valve 35 is in the third position 35c, the operating oil flows into the rod chamber 19r while the operating oil is discharged from the bottom chamber 19b, so that the tilt cylinder 19 contracts and tilts backward. To do.

  In addition, a relief valve 36 for preventing a pressure increase is disposed in the oil passage K6 between the first inlet / outlet port 30a of the hydraulic pump motor 30 and the oil tank T. Further, hydraulic oil discharged from the first inlet / outlet 30a of the hydraulic pump motor 30 flows back to the oil tank T side in the oil passage K7 between the first inlet / outlet 30a of the hydraulic pump motor 30 and the oil tank T. A check valve (check valve) 37 to prevent is provided. Further, a check valve 38 that allows hydraulic oil discharged from the second inflow / outlet 30b to flow to the oil tank T in the oil path K8 between the second inflow / outlet 30b of the hydraulic pump motor 30 and the oil tank T. Is arranged. The hydraulic oil returned to the oil tank T flows into the oil tank T through the filter 39. Further, an oil passage K <b> 9 through which hydraulic oil pumped up from the oil tank T is circulated is connected to the second inlet / outlet 30 b of the hydraulic pump motor 30. In the oil passage K9, a check valve 40 that allows the hydraulic oil in the oil tank T to flow to the second inlet / outlet 30b of the hydraulic pump motor 30 is disposed.

Next, the configuration of the control unit S of the hydraulic control device will be described.
A potentiometer 22a for detecting the operation amount of the lift lever 22 and a potentiometer 23a for detecting the operation amount of the tilt lever 23 are electrically connected to the control unit S. The control unit S controls the rotation of the motor 31 based on the detection signal from the potentiometer 22a based on the operation amount of the lift lever 22, and the ascending proportional valve 32, the regenerative descending proportional valve 33, and the simultaneous operation. The opening degree of each proportional valve of the hourly descending proportional valve 34 is controlled. Further, the control unit S controls the rotation of the motor 31 and the opening degree of the tilt proportional valve 35 based on the detection signal from the potentiometer 23a based on the operation amount of the tilt lever 23.

  In addition, an inverter S1 is electrically connected to the control unit S. The electric power of the battery BT is supplied to the motor 31 via the inverter S1. The electric power generated by the motor 31 is stored in the battery BT via the inverter S1. The battery-type forklift 11 travels using the electric power stored in the battery BT as a drive source.

Hereinafter, the operation of the hydraulic control apparatus of the present embodiment will be described with reference to FIGS.
First, the case where the fork 16 is raised by a single operation will be described. The single operation means that the mast 13 is not tilted forward or backward when the fork 16 is operated, and the fork 16 is not lifted or lowered when the mast 13 is operated.

  When the fork 16 is moved up, hydraulic oil is supplied to the bottom chamber 14 b of the lift cylinder 14. And the control part S controls the rotation speed of the motor 31 and the valve opening degree of the proportional valve 32 for a raise so that the hydraulic fluid of the flow volume (target flow volume) according to the operation amount of the lift lever 22 may distribute | circulate. When the target flow rate is [Q], the rotation speed is [n], and the discharge volume of the hydraulic pump motor 30 is [V], the target flow rate “Q” is calculated by the following equation (1).

Q = n × V (1)
Therefore, the control unit S sets the rotation speed of the motor 31 so as to satisfy the expression (1), and rotates the motor 31 at the rotation speed. Moreover, the control part S controls the flow volume of the hydraulic fluid which distribute | circulates by setting the valve opening degree of the proportional valve 32 for a raise so that (1) Formula may be satisfy | filled.

  Accordingly, the hydraulic pump motor 30 functions as a hydraulic pump by the rotation of the motor 31, thereby sucking the hydraulic oil in the oil tank T and discharging the hydraulic oil from the first inflow / outlet 30a. The hydraulic oil flows through the ascending proportional valve 32 and is supplied to the bottom chamber 14 b of the lift cylinder 14. As a result, the fork 16 moves up by extension of the lift cylinder 14. In addition, the control part S makes the raising proportional valve 32 the 1st position 35a, when complete | finishing raising operation | movement.

Next, a case where the fork 16 is lowered by a single operation will be described.
When lowering the fork 16, the hydraulic oil is discharged from the bottom chamber 14 b of the lift cylinder 14. And the control part S controls the rotation speed of the motor 31 and the valve opening degree of the proportional valve 33 for the fall at the time of regeneration so that the hydraulic fluid of the target flow volume according to the operation amount of the lift lever 22 may distribute | circulate. That is, the control unit S sets the rotational speed of the motor 31 so as to satisfy the above expression (1), and rotates the motor 31 at the rotational speed. Moreover, the control part S controls the flow volume of the hydraulic fluid which distribute | circulates by setting the valve opening degree of the proportional valve 33 for the fall | descendment at the time of regeneration so that Formula (1) may be satisfy | filled. Further, the controller S sets the ascending proportional valve 32, the descending proportional valve 34, and the tilting proportional valve 35 at the time of the descending operation by the single operation to the first positions 33a, 34a, and 35a, respectively.

  When the regenerative descending proportional valve 33 is opened, the hydraulic oil discharged from the bottom chamber 14b of the lift cylinder 14 flows to the hydraulic pump motor 30 side via the regenerative descending proportional valve 33. At this time, when the hydraulic pump motor 30 operates using the hydraulic oil discharged from the bottom chamber 14b as a driving force, the output torque becomes a negative value and the motor 31 performs a regenerative operation. That is, the hydraulic pump motor 30 operates at the number of revolutions for causing the motor 31 to descend at an instruction speed corresponding to the operation amount of the lift lever 22 without performing the power running operation of the motor 31. Further, in the regenerative operation, the speed of the descent operation is controlled by the flow rate of the working oil flowing through the opened regenerative descending proportional valve 33. The motor 31 functions as a generator when the hydraulic pump motor 30 functions as a hydraulic motor. For this reason, the electric power generated by the motor 31 operating as a generator is stored in the battery BT via the inverter S1. In addition, the control part S makes the proportional valve 33 for the fall | descendment at the time of regeneration into the 1st position 33a, when complete | finishing a downward movement.

  Next, a case where the mast 13 is tilted forward or backward when the fork 16 is lowered by a single operation, that is, a case where simultaneous operation is performed during the downward movement of the fork 16 will be described.

  In the hydraulic control apparatus of this embodiment, as shown in FIG. 2, the lift cylinder 14 and the tilt cylinder 19 are operated by a single hydraulic pump motor 30 and motor 31. For this reason, when the mast 13 is tilted forward or backward while the fork 16 is being lowered, the motor 31 is caused to perform a power running operation so that hydraulic oil flows through the tilt cylinder 19. In the hydraulic control apparatus according to the present embodiment, control is performed to smoothly shift from the regenerative operation of the motor 31 accompanying the lowering operation of the fork 16 to the power running operation for the forward tilting operation or the backward tilting operation of the mast 13. Specifically, the flow rate is controlled so that the lowering proportional valve 33 at the time of regeneration and the lowering proportional valve 34 at the time of simultaneous operation are opened at the same time so that the lowering speed according to the operation amount of the lift lever 22 is satisfied. The motor 31 is shifted from the regenerative operation to the power running operation.

  FIG. 3 (a) shows the control flow rate (solid line in the figure) of the regenerative lowering proportional valve 33 when the tilt lever 23 is operated during the lowering operation of the fork 16 by a single operation, and the lowering proportionality during the simultaneous operation. Changes in the control flow rate of the valve 34 (dashed line in the figure) and the control flow rate of the hydraulic pump motor 30 (broken line in the figure) are shown. In FIG. 3A, the control flow rate of the regenerative lowering proportional valve 33 is controlled by [α] more than the pump flow rate so that the regeneration efficiency does not decrease with respect to the target flow rate corresponding to the operation amount of the lift lever 22. The control flow rate of the regenerative lowering proportional valve 33 in the case of regeneration is shown. The target flow rate [Q] in this case is expressed by the following equation (2).

Q = n × V + α (2)
Then, the controller S sets the valve opening degree of the regenerative descending proportional valve 33 so that the target flow rate [Q] represented by the above equation (2) is obtained during the descending operation of the fork 16 by the single operation. More specifically, the control unit S controls the flow rate [Qa] flowing through the regenerative descending proportional valve 33 by control of the target flow rate [Q] shown in Expression (2) by setting the valve opening. On the other hand, the flow rate [Qb] flowing through the proportional valve 34 for simultaneous operation is set to [0 (zero)]. When the flow rate through the proportional valve is set to [0], the valve is fully closed. In FIG. 3A, the control flow rate of the regenerative descending proportional valve 33 during time t1 is [Qa (= n × V + α)]. Further, the motor 31 during the time t1 performs a regenerative operation at a constant rotational speed, as shown in FIG. The control flow rate is a control flow rate and is different from the flow rate actually flowing through the proportional valve. That is, in the present embodiment, as shown in FIG. 3A, the control flow rate of the regenerative descending proportional valve 33 is [n × V × α] as described above, but the control of the hydraulic pump motor 30 is performed. The flow rate is [n × V]. Therefore, the flow rate that actually flows through the regenerative lowering proportional valve 33 is [n × V] corresponding to the control flow rate of the hydraulic pump motor 30.

  When the control unit S detects the operation of the tilt lever 23 at the elapse of time t1, in order to perform the simultaneous operation, the control unit S supplies the hydraulic oil for the regenerative lowering proportional valve 33 and the simultaneous lowering proportional valve 34. The flow rates [Qa] and [Qb] are controlled. By this control, the motor 31 is shifted from the regenerative operation to the power running operation. Specifically, the control unit S determines that the regenerative lowering proportional valve 33 and the following equation (3) are satisfied until the motor 31 shifts from the regenerative operation to the power running operation (time t2 in the figure). The control flow rate of the descending proportional valve 34 is controlled during simultaneous operation.

Qa + Qb = n × V + α (3)
That is, as shown in FIG. 3 (a), the control unit S sets the valve opening so that the flow rate through the regenerative descending proportional valve 33 decreases with time, while the simultaneous operation decreases. The valve opening is set so that the flow rate through the proportional valve 34 increases with time. That is, while decreasing the control flow rate of the regenerative descending proportional valve 33, while increasing the control flow rate of the simultaneous operation descending proportional valve 34, the flow rate through the regenerative descending proportional valve 33 is changed over time. At the same time, the flow rate is decreased and the flow rate through the lowering proportional valve 34 is increased with time. According to this control, in order to control the flow rate so as to satisfy the above equation (3), the decrease in the flow rate flowing through the regenerative lowering proportional valve 33 is equal to the flow rate flowing through the simultaneous operation lowering proportional valve 34. It becomes an increase.

  As shown in FIG. 2, the hydraulic oil flowing through the regenerative descending proportional valve 33 flows into the first inlet / outlet 30 a of the hydraulic pump motor 30. Therefore, when the flow rate flowing through the regenerative descending proportional valve 33 is reduced by the above control, as shown in FIG. 3B, the rotational speed of the motor 31 performing the regenerative operation is reduced, and the motor 31 decelerates. To do. On the other hand, the hydraulic oil flowing through the proportional lowering valve 34 during simultaneous operation flows into the oil tank T as shown in FIG.

  According to such control, the speed of the lowering operation when the fork 16 is lowered by the single operation is such that the hydraulic oil discharged from the bottom chamber 14b of the lift cylinder 14 flows through the proportional valve 33 for lowering during regeneration. Then, by flowing into the hydraulic pump motor 30, the flow rate through the proportional valve 33 for lowering during regeneration is satisfied. When the simultaneous operation starts, at the stage where the motor 31 shifts from the regenerative operation to the power running operation (time t2 in the figure), both the regenerative lowering proportional valve 33 and the simultaneous lowering proportional valve 34 are activated. Oil will circulate. Therefore, the speed of the lowering operation is satisfied by the combined flow rate of the flow rate flowing through the lowering proportional valve 33 during regeneration and the flow rate flowing through the lowering proportional valve 34 during simultaneous operation. Further, the speed of the lowering operation when the motor 31 shifts to the power running operation is satisfied by the flow rate flowing through the lowering proportional valve 34 during the simultaneous operation. In the present embodiment, the oil passage through which the hydraulic oil flows into the oil tank T via the proportional lowering valve 34 during simultaneous operation functions as a bypass passage through which the hydraulic oil flows to satisfy the lowering operation.

  Then, when the motor 31 shifts to the power running operation, the control unit S determines the rotational speed of the motor 31 and the valve opening degree of the tilt proportional valve 35 so that hydraulic oil having a flow rate corresponding to the operation amount of the tilt lever 23 flows. Set. As a result, the hydraulic oil discharged from the hydraulic pump motor 30 flows into the tilt cylinder 19 via the tilt proportional valve 35. Specifically, the hydraulic oil flows into the bottom chamber 19b of the tilt cylinder 19 when the mast 13 is tilted forward, while the hydraulic oil flows into the rod chamber 19r of the tilt cylinder 19 when the mast 13 is tilted backward. To do. Further, when the motor 31 shifts to a power running operation, the control unit S sets the valve opening degree of the simultaneous operation descending proportional valve 34 according to the operation amount of the lift lever 22 and controls the flow rate. At this time, the control unit S sets the opening degree of the regenerative descending proportional valve 33 to “0 (zero)” and controls the flow rate to “0 (zero)”.

  Next, a case will be described where the fork 16 descending operation and the mast 13 in the forward tilting operation or the backward tilting operation are simultaneously performed to return to the state in which the fork 16 descending operation is independently operated. In this case, after returning from the simultaneous operation to the single operation, the regenerative lowering proportional valve 33 and the simultaneous lowering proportional valve 34 are controlled so that the motor 31 performs the regenerative operation again.

  As shown in FIG. 4 (a), at the time of simultaneous operation (time t3 in the figure), the control flow rate [Qb (dotted line in the figure)] of the descending proportional valve 34 at the time of simultaneous operation is [n × V + α]. The flow rate [Qa (solid line in the figure)] flowing through the regenerative descending proportional valve 33 is [0 (zero)]. Then, when the control unit S no longer detects the operation of the tilt lever 23, the control unit S ends the control of the motor 31. Thereby, as shown in FIG.4 (b), the rotation speed of the motor 31 decreases and it decelerates. Thereafter, when the rotational speed of the motor 31 becomes “0 (zero)”, the control unit S sets the flow rate [Qa] of hydraulic oil flowing through the proportional valve 33 for lowering during regeneration and the proportional valve 34 for lowering simultaneously. By controlling [Qb], the motor 31 is shifted to the regenerative operation. Specifically, the control unit S controls the control flow rates of the regenerative lowering proportional valve 33 and the simultaneous operation lowering proportional valve 34 so as to satisfy the above expression (3).

  That is, as shown in FIG. 4A, the control unit S sets the valve opening so that the flow rate through the simultaneous operation descending proportional valve 34 decreases with time, while the regeneration unit descends. The valve opening is set so that the flow rate through the proportional valve 33 increases with time. That is, while decreasing the control flow rate of the descending proportional valve 34 at the time of simultaneous operation, increasing the control flow rate of the descending proportional valve 33 at the time of regeneration, the flow rate flowing through the descending proportional valve 34 at the time of simultaneous operation is reduced. While decreasing with progress, the flow volume which distribute | circulates the proportional valve 33 for the fall | descending at the time of regeneration is increased with progress of time. According to this control, in order to control the flow rate so as to satisfy the above equation (3), the decrease in the flow rate flowing through the simultaneous operation descending proportional valve 34 is the amount of the flow rate flowing through the regeneration descending proportional valve 33. It becomes an increase.

  As shown in FIG. 2, the hydraulic oil flowing through the regenerative descending proportional valve 33 flows into the first inlet / outlet 30 a of the hydraulic pump motor 30. For this reason, if the flow volume which distribute | circulates the proportional valve | bulb 33 for the fall at the time of regeneration increases by the said control, as shown to FIG. That is, the motor 31 performs a regenerative operation.

  According to such control, even when the simultaneous operation is shifted to the single operation, the motor is controlled by controlling the flow rate flowing through the regenerative lowering proportional valve 33 and the flow rate flowing through the simultaneous operating lowering proportional valve 34. 31 starts the regenerative operation again. The speed of the lowering operation is the flow rate of the hydraulic oil flowing through the proportional lowering valve 33 during regeneration and the flow rate of the hydraulic oil flowing through the lowering proportional valve 34 during simultaneous operation during time t4 shown in FIG. It is satisfied by the combined flow rate. Further, the speed of the lowering operation after the elapse of time t4 is circulated through the lowering proportional valve 33 at the time of regeneration when the flow rate of the hydraulic oil flowing through the lowering proportional valve 34 at the time of simultaneous operation becomes “0 (zero)”. It is satisfied by the flow rate of hydraulic oil.

Therefore, according to the present embodiment, the following effects can be obtained.
(1) An oil passage K2 provided with a regenerative lowering proportional valve 33 as an oil passage through which hydraulic oil discharged from the bottom chamber 14b of the lift cylinder 14 and a lowering proportional valve 34 during simultaneous operation are provided. An oil passage K3 was provided. Thereby, when the lowering operation of the fork 16 is performed by a single operation, the motor 31 can be regenerated by controlling the flow rate of the working oil flowing through the regenerative descending proportional valve 33. On the other hand, when the simultaneous operation of moving the mast 13 forwardly or backwardly in addition to the downward movement of the fork 16 is performed, the hydraulic fluid flows through the proportional valve 33 for lowering during regeneration and the proportional valve 34 for lowering during simultaneous operation. By controlling this flow rate, it is possible to shift from the single operation to the simultaneous operation while satisfying the speed of the lowering operation of the fork 16. Therefore, when operating a plurality of operation targets (mast 13 and fork 16) simultaneously, each operation target can be operated satisfactorily.

  (2) In this embodiment, by controlling the flow rate of the hydraulic oil flowing through the proportional lowering valve 33 for regeneration and the proportional lowering valve 34 for simultaneous operation, a smooth transition from single operation to simultaneous operation is possible. Can do. That is, if the regeneration descending proportional valve 33 is immediately closed with the start of the simultaneous operation, the descending operation of the fork 16 may be stopped or a shock due to speed fluctuation may occur. However, in the present embodiment, the flow rate of the lowering proportional valve 33 during regeneration and the lowering proportional valve 34 during simultaneous operation are linearly changed while satisfying the speed of the lowering operation of the fork 16, so that the operation is stopped. And speed fluctuations are unlikely to occur.

  (3) In this embodiment, since the lift cylinder 14 and the tilt cylinder 19 are controlled using the single hydraulic pump motor 30 and the single motor 31, the hydraulic control apparatus adopting a plurality of pumps and motors. This is advantageous in terms of cost. In addition, since the mounting space for the hydraulic control device can be reduced, an increase in the size of the vehicle body can be suppressed.

  (4) Further, even when shifting from the simultaneous operation to the single operation, the regenerative descending proportional valve 33 and the simultaneous operation descending proportional valve 34 are circulated in the same manner as when the single operation is shifted to the simultaneous operation. By controlling the flow rate of the hydraulic oil, the motor 31 can perform a regenerative operation. Further, even when shifting from the simultaneous operation to the single operation, it is possible to smoothly shift.

  (5) Since the two proportional valves, the proportional valve 33 for descending during regeneration and the proportional valve 34 for descending during simultaneous operation, are provided to control the flow rate, the control is simple. That is, since the object for controlling the flow rate is the same proportional valve, it is easy to synchronize the control.

(Second Embodiment)
Next, a second embodiment embodying the present invention will be described with reference to FIGS. Note that, in the embodiments described below, the same reference numerals are given to the same configurations as those of the embodiments already described, and redundant descriptions thereof are omitted or simplified.

  As shown in FIG. 5, the hydraulic control apparatus according to the present embodiment includes a regenerative lowering switching valve 45 as an electromagnetic switching valve in the oil passage K2, instead of the regenerative lowering proportional valve 33 according to the first embodiment. It is arranged. The regenerative descent switching valve 45 can take a first position 45a as a closed state that does not allow the flow of hydraulic oil, and a second position 45b as an open state that allows the flow of hydraulic oil. The regenerative descent switching valve 45 of the present embodiment is an ON-OFF valve that can take two positions, a first position 45a and a second position 45b.

Hereinafter, the operation of the hydraulic control apparatus of the present embodiment will be described with reference to FIG.
In addition, since the control content of the raising operation of the fork 16 by the single operation is the same as that of the first embodiment, the overlapping description is omitted.

  When the fork 16 is lowered by a single operation, the control unit S sets the regenerative descent switching valve 45 to the second position 45b and sets the rotation speed of the motor 31 so as to satisfy the above expression (1). And the control part S controls the flow volume [Q] of the hydraulic fluid which flows into the hydraulic pump motor 30 by controlling the rotation speed of the motor 31. Note that the control unit S sets the ascending proportional valve 32, the descending proportional valve 34, and the tilting proportional valve 35 at the first position 33a, 34a, and 35a during the descending operation by the single operation, respectively.

  Next, a case where the mast 13 is tilted forward or backward when the fork 16 is lowered by a single operation, that is, a case where simultaneous operation is performed during the downward movement of the fork 16 will be described.

  In the hydraulic control apparatus according to the present embodiment, the flow rate proportional so as to satisfy the descending speed corresponding to the operation amount of the lift lever 22 by simultaneously opening the proportional valve 34 for lowering at the time of simultaneous operation and the switching valve 45 for lowering at the time of regeneration. While performing the control, the motor 31 is shifted from the regenerative operation to the power running operation.

  FIG. 6A shows the flow rate of hydraulic oil flowing to the hydraulic pump motor 30 when the tilt lever 23 is operated during the lowering operation of the fork 16 by a single operation (solid line in the figure), and the lowering during simultaneous operation. The transition of the flow rate of hydraulic oil flowing through the proportional valve 34 (one-dot chain line in the figure) is shown. Then, the control unit S sets the flow rate of the working oil flowing to the hydraulic pump motor 30 to the target flow rate [Q] during the lowering operation of the fork 16 by a single operation, while circulating the lowering proportional valve 34 during the simultaneous operation. The flow rate [Qb] to be set is [0 (zero)]. When the control unit S detects the operation of the tilt lever 23 at the time t5, the control unit S controls the flow rate [Qb] of the hydraulic oil flowing through the regenerative descending proportional valve 33 to perform the simultaneous operation. Thus, the motor 31 is shifted from the regenerative operation to the power running operation. More specifically, the control unit S reduces the simultaneous operation descending proportional valve 34 so as to satisfy the following expression (4) until the motor 31 shifts from the regenerative operation to the power running operation (time t6 in the figure). The flow rate [Qb] of the hydraulic oil flowing through is controlled.

Qb = (n−na) × V (4)
In the above equation (4), [n] is the number of rotations of the motor 31 for satisfying the target flow rate [Q]. [Na] is the number of rotations when the motor 31 is decelerated to shift from the regenerative operation to the power running operation. According to the above equation (4), the flow rate flowing through the descending proportional valve 34 during simultaneous operation is determined so as to be synchronized with the rotational speed of the hydraulic pump motor 30.

  Then, when the opening degree of the proportional lowering proportional valve 34 is set so as to satisfy the above equation (4), the flow rate [Qb] of the hydraulic oil flowing through the simultaneous proportional descending proportional valve 34 is shown in FIG. As shown in a), it increases with time. On the other hand, the flow rate of the hydraulic oil flowing to the hydraulic pump motor 30 decreases with time as shown in FIG. At this time, the flow rate of the hydraulic fluid flowing to the hydraulic pump motor 30 can be obtained by [Q−Qb]. In other words, the decrease in the flow rate flowing to the hydraulic pump motor 30 is the increase in the flow rate flowing through the descending proportional valve 34 during simultaneous operation. The flow rate flowing to the hydraulic pump motor 30 is the flow rate of the hydraulic fluid flowing through the regenerative lowering switching valve 45. Further, the control unit S controls the flow rate that flows to the hydraulic pump motor 30 by controlling the number of rotations of the motor 31.

  Then, when the motor 31 shifts to the power running operation, the control unit S sets the regeneration lowering switching valve 45 to the first position 45a at the timing (time t6 in the figure). That is, the regenerative lowering switching valve 45 is fully closed. When the regenerative descent switching valve 45 is fully closed, as shown in FIG. 6 (a), the flow rate of the working oil flowing through the regenerative descent switching valve 45 to the hydraulic pump motor 30 is [0 ( Zero)]. On the other hand, the flow rate [Qb] of the working oil flowing to the oil tank T via the proportional lowering valve 34 during the simultaneous operation becomes the target flow rate [Q (= n × V)].

  According to such control, the speed of the lowering operation when the fork 16 is moved downward by a single operation is such that the hydraulic oil discharged from the bottom chamber 14b of the lift cylinder 14 passes through the switching valve 45 for lowering during regeneration. By flowing to the hydraulic pump motor 30, the flow rate of the working oil flowing through the regenerative lowering switching valve 45 is satisfied. When the simultaneous operation starts, at the stage where the motor 31 shifts from the regenerative operation to the power running operation (from time t5 to time t6 in the figure), the regenerative lowering switching valve 45 and the simultaneous operation lowering proportional valve 34 are The hydraulic oil circulates in both. For this reason, the speed of the descent operation is determined by the combined flow rate of the flow rate flowing through the regenerative descent switching valve 45 (the flow rate of hydraulic oil flowing to the hydraulic pump motor 30) and the flow rate flowing through the descent proportional valve 34 during simultaneous operation. Satisfied. Further, the speed of the lowering operation when the motor 31 shifts to the power running operation is satisfied by the flow rate flowing through the lowering proportional valve 34 during the simultaneous operation.

  Further, when the motor 31 shifts to the power running operation, the control unit S controls the rotational speed of the motor 31 and the valve opening degree of the tilt proportional valve 35 so that hydraulic oil having a flow rate corresponding to the operation amount of the tilt lever 23 flows. Set. As a result, the hydraulic oil discharged from the hydraulic pump motor 30 flows into the tilt cylinder 19 via the tilt proportional valve 35. In addition, when the motor 31 shifts to a power running operation, the control unit S controls the flow rate by setting the valve opening degree of the proportional operation descending proportional valve 34 according to the operation amount of the lift lever 22.

  Next, a case will be described where the fork 16 descending operation and the mast 13 in the forward tilting operation or the backward tilting operation are simultaneously performed to return to the state in which the fork 16 descending operation is independently operated. In this case, after returning from the simultaneous operation to the single operation, the hydraulic pump motor 30 (the regenerative descending switching valve 45) and the simultaneous operation descending proportional valve 34 are controlled so that the motor 31 performs the regenerating operation again. To do. In this case, the change in the flow rate of the hydraulic oil flowing through the hydraulic pump motor 30 (the regenerative lowering switching valve 45) and the flow rate of the hydraulic oil flowing through the lowering proportional valve 34 during the simultaneous operation, and the rotation speed of the motor 31 are as follows. The transition of can be expressed in the same manner as in FIGS. In the case of the present embodiment, the change in the flow rate indicated by the solid line in FIG. 4A is the change in the flow rate of the hydraulic oil flowing through the hydraulic pump motor 30.

  As shown in FIG. 4A, at the time of simultaneous operation (time t3 in the figure), the flow rate [Qb (dashed line in the figure)] flowing through the proportional valve 34 for simultaneous operation is [n × V]. The flow rate through the hydraulic pump motor 30 is [0 (zero)]. Then, when the control unit S no longer detects the operation of the tilt lever 23, the control unit S ends the control of the motor 31. Thereby, as shown in FIG.4 (b), the rotation speed of the motor 31 decreases and it decelerates. Thereafter, when the rotational speed of the motor 31 reaches “0 (zero)”, the control unit S sets the regenerative lowering switching valve 45 to the second position 45 b and operates simultaneously with the flow rate of the hydraulic oil flowing through the hydraulic pump motor 30. By controlling the flow rate [Qb] of the hydraulic oil flowing through the hour descending proportional valve 34, the motor 31 is shifted to the regenerative operation. That is, the control unit S is configured such that the combined flow rate of the hydraulic fluid flowing through the hydraulic pump motor 30 and the hydraulic fluid flow rate [Qb] flowing through the lowering proportional valve 34 during simultaneous operation becomes the target flow rate [Q]. The opening degree of the proportional valve 34 for lowering during simultaneous operation is set.

  Then, as shown in FIG. 4 (a), the control unit S sets the valve opening so that the flow rate through the simultaneous operation descending proportional valve 34 decreases with time, so that the hydraulic pump motor The flow rate through 30 is increased over time. At this time, the hydraulic fluid flowing through the regenerative descending switching valve 45 flows into the first inlet / outlet 30a of the hydraulic pump motor 30 as shown in FIG. For this reason, if the flow volume which distribute | circulates the hydraulic pump motor 30 by the said control increases, as shown in FIG.4 (b), the motor 31 will increase in rotation speed and the speed will increase. That is, the motor 31 performs a regenerative operation.

  According to such control, even when shifting from the simultaneous operation to the single operation, the motor 31 is again controlled by controlling the flow rate flowing through the hydraulic pump motor 30 and the flow rate flowing through the simultaneous operation descending proportional valve 34. Regenerative operation is performed. The speed of the lowering operation is satisfied by the combined flow rate of the flow rate flowing through the hydraulic pump motor 30 and the flow rate flowing through the proportional lowering valve 34 during the simultaneous operation for the time t4 shown in FIG. The speed of the lowering operation after the elapse of time t4 is satisfied by the flow rate flowing through the hydraulic pump motor 30 when the flow rate flowing through the lowering proportional valve 34 during simultaneous operation becomes “0 (zero)”. .

  Therefore, according to this embodiment, in addition to the effects (1) to (4) of the first embodiment, the following effects can be obtained. In the present embodiment, the above effects (1) to (4) can be produced by providing a regenerative descent switching valve 45 instead of the regenerative descent proportional valve 33.

  (6) A regenerative descent switching valve 45 as an ON-OFF valve is disposed in the oil passage K <b> 2 to control the flow rate of the working oil flowing to the hydraulic pump motor 30. For this reason, the cost of the hydraulic control device can be suppressed. Moreover, the control of the solenoid valve can be simplified.

In addition, you may change this embodiment as follows.
In each embodiment, the hydraulic cylinder connected to the hydraulic pump motor 30 may be a hydraulic cylinder that causes a cargo handling member other than the mast 13 as a cargo handling member to perform a cargo handling operation. For example, the fork 16 may be a hydraulic cylinder for moving the left and right, tilting, or rotating. Moreover, it is good also as a hydraulic cylinder for operating the clamp apparatus for clamping a load. The cargo handling member is operated by a forklift driver when loading and unloading cargo.

  In the first embodiment, the flow rate flowing through the regenerative lowering proportional valve 33 and the flow rate flowing through the simultaneous lowering proportional valve 34 are such that the combined flow rate corresponds to the operation amount of the lift lever 22. For example, the change mode may be changed. For example, it may be reduced or increased stepwise (stepwise). Similarly, also in the second embodiment, the mode of change of the flow rate flowing through the hydraulic pump motor 30 and the flow rate flowing through the simultaneous operation descending proportional valve 34 may be changed.

  In each embodiment, a tolerance may be set between the flow rate (target flow rate) corresponding to the operation amount of the lift lever 22 and the actual flow rate. For example, the flow rate that actually flows with respect to the target flow rate may be increased or decreased within a tolerance range.

  In each embodiment, the hydraulic oil that has flowed through the proportional lowering valve 34 during simultaneous operation may be returned to the hydraulic pump motor that is provided separately in place of the oil tank T. For example, the hydraulic pump motor may supply hydraulic oil to a hydraulic cylinder for operating a cargo handling member other than the fork 16 and the mast 13. The hydraulic pump motor may be provided exclusively for power generation.

In the first embodiment, the flow rate [Q] corresponding to the operation amount of the lift lever 22 may be controlled as the flow rate calculated by the equation (1).
In each embodiment, the check valve 37 and the oil passage K7 may not be provided.

  DESCRIPTION OF SYMBOLS 11 ... Forklift, 14 ... Lift cylinder, 16 ... Fork, 19 ... Tilt cylinder, 22 ... Lift lever, 23 ... Tilt lever, 30 ... Hydraulic pump motor, 31 ... Motor, 33 ... Proportional valve for lowering during regeneration, 34 ... Simultaneously Proportional valve for lowering during operation, 45: switching valve for lowering during regeneration, K1 to K4: oil passage, S: control unit.

Claims (4)

The first hydraulic cylinder that raises or lowers the fork by operating the lifting / lowering instruction member to supply and discharge hydraulic oil, and the other handling member by loading and discharging the hydraulic oil by operating the cargo handling instruction member A hydraulic control device for a forklift comprising a second hydraulic cylinder to be operated;
A hydraulic pump motor connected to the first hydraulic cylinder and the second hydraulic cylinder via the hydraulic oil supply oil path;
A first oil passage for flowing hydraulic oil discharged from the first hydraulic cylinder to the hydraulic pump motor;
A second oil passage for flowing hydraulic oil discharged from the first hydraulic cylinder to the drain side;
An electromagnetic switching valve disposed in the first oil passage;
An electromagnetic proportional valve disposed in the second oil passage;
A control unit for controlling the flow rate of hydraulic oil flowing through the electromagnetic switching valve and the electromagnetic proportional valve,
When the fork is lowered by a single operation, the control unit controls the flow rate through the electromagnetic switching valve so that the flow rate of hydraulic oil corresponding to the operation amount of the lift instruction member is circulated. In the case of shifting to the simultaneous operation in which the cargo handling operation of the cargo handling member is added to the descending motion of the fork by the operation, the flow rate of the hydraulic oil flowing through the electromagnetic proportional valve is increased with time and the operation of the elevation instruction member is performed. The first oil is controlled when the flow rate of flow through the electromagnetic switching valve and the electromagnetic proportional valve is controlled so that the flow rate of hydraulic oil corresponding to the flow amount flows , and when the hydraulic pump motor shifts from regeneration to power running. forklift and controlling the flow rate of the hydraulic fluid flow rate of the hydraulic oil flowing to the hydraulic pump motor via a road flows through the electromagnetic switching valve so as to zero Hydraulic control device. 2. The forklift according to claim 1 , wherein the electromagnetic switching valve is an electromagnetic proportional valve, and an electromagnetic proportional valve is provided in each of the first oil passage and the second oil passage. Hydraulic control device. The electromagnetic switching valve is an ON-OFF valve,
The forklift hydraulic control device according to claim 1 , wherein the control unit controls a flow rate flowing to the hydraulic pump motor via the ON-OFF valve. When the control unit shifts from the simultaneous operation to the lowering operation of the fork by the single operation, the flow rate that flows through the electromagnetic switching valve to flow the hydraulic oil at a flow rate corresponding to the operation amount of the lift instruction member The hydraulic flow control device for a forklift according to any one of claims 1 to 3 , wherein a flow rate through the electromagnetic proportional valve is controlled.