JP5984079B2 - Industrial vehicle regenerative hydraulic system - Google Patents

Description

  The present invention relates to a regenerative hydraulic device for an industrial vehicle.

  As a conventional forklift regenerative hydraulic device, the energy of hydraulic oil discharged from the hydraulic actuator when the fork is lowered is secured when the fork load exceeds a predetermined weight while ensuring the fork descending speed when the fork load is light. Some are recovered as electrical energy.

Japanese Patent Laid-Open No. 11-165959

  However, in the above-described conventional forklift regenerative hydraulic system, the flow rate of hydraulic oil passing through the directional control valve for lift control differs between when the fork load is light and when it is heavy. There was a problem that the descent speed of the terrain was different.

  The present invention has been made paying attention to such problems, and the operation of discharging from the hydraulic actuator according to the weight of the load while controlling the descending speed of the fork constant regardless of the weight of the load. It aims at recovering the energy of oil as electric energy.

The present invention relates to a regenerative hydraulic device for an industrial vehicle, which includes an actuator driven by a working fluid supplied from a pump, a direction control valve for switching supply and discharge of the working fluid to and from the actuator, and a working fluid discharged from the actuator. A cylinder line that leads to the directional control valve, a hydraulic motor driven by the working fluid discharged from the actuator, a generator that is driven by the hydraulic motor to generate power, a capacitor that stores the power generated by the generator, and the cylinder line In accordance with the pressure of the regenerative switching valve that controls the supply amount of the working fluid to the hydraulic motor, the return line that guides the working fluid that has been discharged from the actuator and passed through the direction control valve to the regenerative switching valve, and is discharged from the actuator. A regenerative line for guiding the working fluid that has passed through the regenerative switching valve to the hydraulic motor; A check valve and a pressure control valve for controlling a constant pressure difference between the pressure in the pressure and return lines of the cylinder line, provided on the cylinder line, the working fluid discharged from the actuator to regulate to be guided to the directional control valve And comprising. The pressure control valve guides the working fluid discharged from the actuator to the direction control valve so that the pressure difference between the cylinder line pressure and the return line pressure is constant, and the regenerative switching valve It has a spring that presses in the direction opposite to the cylinder line pressure acting on the regenerative pressure receiving part of the valve, and when the pressing force due to the cylinder line pressure becomes larger than the pressing force of the spring, the working fluid to the hydraulic motor The supply amount is increased.

  According to the present invention, the amount of working fluid supplied to the hydraulic motor is controlled in accordance with the cylinder line pressure while the pressure difference between the cylinder line pressure and the return line pressure is controlled to be constant. Regardless of this, the energy of the hydraulic oil discharged from the hydraulic actuator can be recovered as electric energy in accordance with the weight of the load while controlling the descending speed of the fork to be constant.

1 is a schematic configuration diagram of a regenerative hydraulic control device for a battery-type forklift according to a first embodiment of the present invention. It is a schematic block diagram of the regeneration hydraulic control apparatus of the battery-type forklift by 2nd Embodiment of this invention. It is a schematic block diagram of the regeneration hydraulic control apparatus of the battery-type forklift by 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic configuration diagram of a regenerative hydraulic pressure control device 100 for a battery-type forklift according to a first embodiment of the present invention.

  A regenerative hydraulic control device 100 for a battery-type forklift includes a hydraulic pressure generating unit 1, a lift cylinder 2, a lift control unit 3, a regenerative unit 4, and a controller 5.

  The hydraulic pressure generator 1 includes a battery 11, an electric motor 12, and a hydraulic pump 13.

  The battery 11 stores electric power for driving the battery-type forklift, and supplies the stored electric power to various electric components as necessary. As the battery 11, a lithium ion secondary battery or a high-capacity capacitor that can be charged from the outside can be used.

  The electric motor 12 is a three-phase AC synchronous motor in which a plurality of permanent magnets are embedded in a rotor and a stator coil is wound around a stator. The electric motor 12 is supplied with electric power from the battery 11 and is driven to rotate.

  The hydraulic pump 13 is a fixed displacement pump. The hydraulic pump 13 is driven by the electric motor 12 and discharges hydraulic oil at a flow rate corresponding to the rotational speed of the electric motor 12.

  The lift cylinder 2 is divided into a rod-side fluid chamber 22 and a bottom-side fluid chamber 23 by a piston rod 21 that moves slidably in the lift cylinder 2. The lift cylinder 2 is a single-action cylinder that supplies and discharges hydraulic oil only to the bottom side fluid chamber 23 (hereinafter referred to as “supply / discharge”), and is a hydraulic pressure for raising and lowering the fork of the battery-type forklift. Functions as an actuator.

  The lift control unit 3 includes an elevation switching valve 31, a check valve 32, a first pilot line 33, a second pilot line 34, and a pressure control valve 35. The lift control unit 3 controls the raising and lowering operation of the fork by controlling the supply amount and discharge amount (hereinafter referred to as “supply / discharge amount”) of hydraulic oil to the bottom side fluid chamber 23 of the lift cylinder 2. Hereinafter, each structure of the lift control part 3 is demonstrated.

  The up / down switching valve 31 includes three ports, a pump port 311, a return port 312, and a cylinder port 313, and three direction switching positions of an ascending control position (A), a holding control position (B), and a descending control position (C). These are manual three-port directional switching valves. The raising / lowering switching valve 31 is switched to any one of the raising control position (A), the holding control position (B), and the lowering control position (C) by operating the manual lever 314.

  When the raising / lowering switching valve 31 is switched to the raising control position (A), the hydraulic oil discharged from the hydraulic pump 13 is supplied to the bottom side fluid chamber 23 of the lift cylinder 2 and the fork rises together with the piston rod 21.

  When the up / down switching valve 31 is switched to the holding control position (B), the supply and discharge of the hydraulic oil to the bottom side fluid chamber 23 of the lift cylinder 2 is stopped, and the fork is held at an arbitrary height.

  When the raising / lowering switching valve 31 is switched to the lowering control position (C), the piston rod 21 is lowered together with the fork by the weight of the load and the fork, and the hydraulic oil is discharged from the bottom side fluid chamber 23 of the lift cylinder 2.

  The pump port 311 of the elevation switching valve 31 is connected to the discharge port of the hydraulic pump 13 by the pump line 6. The pump line 6 is a line through which the hydraulic oil discharged from the hydraulic pump 13 flows.

  A return port 312 of the up / down switching valve 31 is connected to an inlet port 411 of a regeneration switching valve 41 described later by a return line 7. The return line 7 is a line through which the hydraulic oil discharged from the bottom side fluid chamber 23 of the lift cylinder 2 flows.

  The cylinder port 313 of the elevation switching valve 31 is connected to the bottom side fluid chamber 23 of the lift cylinder 2 by the cylinder line 8. The cylinder line 8 includes a supply cylinder line 8a through which hydraulic oil supplied to the bottom fluid chamber 23 flows when the elevation switching valve 31 is switched to the elevation control position (A), and a lowering control position ( And a discharge cylinder line 8b through which the hydraulic oil discharged from the bottom side fluid chamber 23 flows.

  The check valve 32 is provided in the supply cylinder line 8a. The check valve 32 restricts the flow of the hydraulic oil in one direction and prevents the hydraulic oil discharged from the bottom side fluid chamber 23 from flowing through the supply cylinder line 8a and returning to the up / down switching valve 31.

  The first pilot line 33 generates pressure (hereinafter referred to as “first pilot pressure”) P1 acting on the discharge cylinder line 8b between the pressure control valve 35 and the elevation switching valve 31 as a pressure control valve 35 and a regeneration which will be described later. This is a line for guiding to the switching valve 41.

  Here, if the pressure acting on the discharge cylinder line 8b between the lift cylinder 2 and the pressure control valve 35, that is, the load pressure acting on the lift cylinder 2 (hereinafter referred to as “lift load pressure”) is Pload, The 1 pilot pressure P1 is a pressure obtained by subtracting the passage pressure loss of the pressure control valve 35 from the lift load pressure Pload, and is very close to the lift load pressure Pload. The lift load pressure Pload is a load applied to the lift cylinder 2 when the fork is moved up and down, and is a pressure in the bottom side fluid chamber 23 of the lift cylinder 2. Accordingly, the heavier fork load, the higher the lift load pressure Pload and the first pilot pressure P1.

  The second pilot line 34 is a line for guiding pressure (hereinafter referred to as “second pilot pressure”) P <b> 2 acting on the return line 7 to the pressure control valve 35.

  The pressure control valve 35 is provided in the discharge cylinder line 8b. The pressure control valve 35 includes a spring 351 that constantly presses the valve body in the pressure control valve 35 toward the valve opening side. The pressure control valve 35 includes a valve opening side pressure receiving portion 352 to which a second pilot pressure P2 that presses the valve body in the pressure control valve 35 to the valve opening side is guided, and a first pilot pressure P1 that presses the valve body to the valve closing side. And a valve-closing pressure receiving portion 353 to which is guided.

  The pressure control valve 35 is configured in this way, and the pressing force (product of the first pilot pressure P1 and the area A of the valve closing side pressure receiving portion 353) P1A acting on the valve closing side pressure receiving portion 353 is the pressing force of the spring 351. When the pressure is greater than the resultant force of Fset1 and the pressing force acting on the valve-opening pressure receiving portion 352 (the product of the second pilot pressure P2 and the area B of the valve-opening pressure receiving portion 352) P2B, the valve is gradually closed. That is, the pressure control valve 35 has the first pilot pressure so that the difference between the pressing force P1A acting on the valve closing side pressure receiving portion 353 and the pressing force P2B acting on the valve opening side pressure receiving portion 352 becomes the pressing force Fset1 of the spring 351. P1 is controlled so that the differential pressure (= P1-P2) across the elevation switching valve 31 is constant.

  The regeneration unit 4 includes a regeneration switching valve 41, a hydraulic motor 42, and a generator 43. The regenerative unit 4 drives the hydraulic motor 42 with hydraulic oil discharged from the bottom side fluid chamber 23 of the lift cylinder 2 as necessary to rotate the generator 43 and charge the battery 11 with the generated power. Hereinafter, each structure of the regeneration part 4 is demonstrated.

  The regenerative switching valve 41 includes three ports, an inlet port 411, a tank port 412, and a regenerative port 413, and a three-port direction switch that includes two redirection control positions (D) and a reversion control position (E). It is a valve.

  The inlet port 411 of the regeneration switching valve 41 is connected to the return port 312 of the elevation switching valve 31 by the return line 7.

  The tank port 412 of the regeneration switching valve 41 is connected to the oil tank 60 by the tank line 9. The tank line 9 is a line for returning hydraulic oil to the oil tank 60.

  The regeneration port 413 of the regeneration switching valve 41 is connected to the tank line 9 by the regeneration line 10. The regeneration line 10 is provided with a hydraulic motor 42. The hydraulic motor 42 is driven by hydraulic oil flowing through the regeneration line 10 to rotate the generator 43, and the generator 43 charges the battery 11 with the generated power.

  In addition, the regeneration switching valve 41 has a spring 414 that always presses the regeneration switching valve 41 toward the return control position (E), and a first pilot pressure P1 that presses the regeneration switching valve 41 toward the regeneration control position (D). And a regenerative pressure receiving part 415 to which is guided. The regenerative switching valve 41 regenerates when the pressing force (product of the first pilot pressure P1 and the area C of the regenerative pressure receiving portion 415) P1C acting on the regenerative pressure receiving portion 415 becomes larger than the pressing force Fset2 of the spring 414. It is switched to the control position (D).

  That is, when the load of the fork is heavier than a predetermined weight and the pressing force P1C acting on the regenerative pressure receiving portion 415 becomes larger than the pressing force Fset2 of the spring 414, the regenerative switching valve 41 is in the regenerative control position (D). Can be switched. When the regeneration switching valve 41 is switched to the regeneration control position (D), the hydraulic oil flowing through the return line 7 flows to the regeneration line 10 via the regeneration switching valve 41 and drives the hydraulic motor 42. Thereby, the power generation by the generator 43 is performed.

  On the other hand, when the load of the fork is equal to or less than a predetermined weight, the pressing force P1C acting on the regenerative pressure receiving portion 415 is equal to or lower than the pressing force Fset2 of the spring 414, so that the regenerative switching valve 41 is switched to the return control position (E). It is done. When the regeneration switching valve 41 is switched to the return control position (E), the hydraulic oil that has flowed through the return line 7 flows to the tank line 9 via the regeneration switching valve 41 and is directly returned to the oil tank 60.

  Thus, the regenerative operation is performed only when the pressing force P1C acting on the regenerative pressure receiving portion 415 is larger than the pressing force Fset2 of the spring 414. If the hydraulic oil flows through the regenerative line 10 when Fset2 or less, that is, the load is light and the first pilot pressure P1 is low, the pressure of the regenerative line 10 on the hydraulic oil inlet side of the hydraulic motor 42 is too low. This is because the hydraulic motor 42 may not be driven. If the hydraulic motor 42 cannot be driven, the flow of hydraulic oil is obstructed by the hydraulic motor 42, so the flow rate of the hydraulic oil passing through the up / down switching valve 31 is reduced, and this time, the fork descending speed may be reduced. There is. Therefore, the pressing force Fset2 of the spring 414 of the regenerative switching valve 41 is set in consideration of the driving load of the hydraulic motor 42, and may be set as appropriate according to the characteristics of the hydraulic motor 42.

  The controller 5 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). The controller 5 receives signals from various sensors for detecting the operating state of the battery-type forklift, and controls the rotational speed of the electric motor 12 and the like based on the input signals from the various sensors.

  Hereinafter, the operation and effect of the regenerative hydraulic control device 100 for the battery-type forklift will be described.

  First, the operation and effect of the pressure control valve 35 according to the present embodiment will be described.

  When the pressure control valve 35 is not provided in the discharge cylinder line 8b, the lift load pressure Pload acts on the discharge cylinder line 8b if the up / down switching valve 31 is switched to the lowering control position (C). The lift load pressure Pload increases as the load becomes heavier. Therefore, the front-rear differential pressure (= P1-P2) of the elevation switching valve 31 increases as the load becomes heavier.

  As described above, when the front-rear differential pressure of the up-down switching valve 31 changes, even if the opening degree of the up-down switching valve 31 (in other words, the operation amount of the manual lever 314) is the same, the front-rear differential pressure increases. The flow rate of the hydraulic oil that passes through the elevation switching valve 31 increases. As a result, even if the operation amount of the manual lever 314 is the same, the lowering speed of the fork becomes faster as the load becomes heavier, and the operability deteriorates.

  Therefore, in this embodiment, the pressure control valve 35 is provided in the discharge cylinder line 8b.

  The pressure control valve 35 according to the present embodiment has an opening degree so that when the elevation switching valve 31 is switched to the lowering control position (C), the differential pressure across the elevation switching valve 31 (= P1-P2) is constant. Is controlled. That is, in the present embodiment, the opening degree of the pressure control valve 35 is controlled so that the differential pressure across the elevation switching valve 31 is constant regardless of the lift load pressure Pload that changes depending on the weight of the load on the fork. Therefore, the flow rate of the hydraulic oil passing through the pressure control valve 35 is a constant flow rate according to the opening degree of the pressure control valve 35.

  Thereby, the descending speed of the fork does not change depending on the weight of the load, and the descending speed of the fork can be made constant regardless of the weight of the load. Therefore, the operability when lowering the fork can be improved. The pressing force Fset1 of the spring 351 may be set as appropriate according to the purpose of use of the battery-type forklift so that a desired lowering speed can be obtained.

  Next, the operation and effect of the regeneration switching valve 41 according to this embodiment will be described.

  If hydraulic oil flows through the regenerative line 10 when the load of the fork is light and the first pilot pressure P1 is low, the flow of hydraulic oil is blocked by the hydraulic motor 42 and passes through the up / down switching valve 31. There is a risk that the fork descending speed will slow down.

  Therefore, in the present embodiment, the regenerative switching valve 41 is switched so as to switch to the regenerative control position (D) only when the pressing force P1C acting on the regenerative pressure receiving unit 415 is higher than the pressing force Fset2 of the spring 414 of the regenerative switching valve 41. The hydraulic oil that has been configured to flow through the return line 7 after passing through the elevation switching valve 31 is caused to flow to the regenerative line 10. That is, only when the load of the fork is heavier than a predetermined weight, the hydraulic oil that has passed through the up / down switching valve 31 and has flowed through the return line 7 is allowed to flow into the regenerative line 10.

  Thereby, when the load of the fork is equal to or less than the predetermined weight and the pressing force P1C acting on the regeneration pressure receiving unit 415 is equal to or less than the pressing force Fset2 of the spring 414 of the regeneration switching valve 41, the regeneration switching valve 41 is returned to the return control position (E). Since it is switched, the hydraulic oil that has passed through the regenerative switching valve 41 is returned directly to the oil tank 60 through the tank line 9. Therefore, it is possible to prevent the descending speed of the fork from becoming slow.

  On the other hand, when the load of the fork is heavier than a predetermined weight and the pressing force P1C acting on the regeneration pressure receiving portion 415 is higher than the pressing force Fset2 of the spring 414 of the regeneration switching valve 41, the regeneration switching valve 41 is in the regeneration control position ( D), the hydraulic oil that has passed through the regeneration switching valve 41 is returned to the oil tank 60 after driving the hydraulic motor 42 through the regeneration line 10.

  As described above, according to the regenerative hydraulic control device 100 for the battery-type forklift according to the present embodiment, the regenerative switching valve 41 performs regeneration only when the load of the fork is heavier than a predetermined weight, and the pressure control valve. 35, the differential pressure across the elevation switching valve 31 is made constant. Thereby, regardless of the weight of the load of the fork, it is possible to perform regeneration while controlling the descending speed of the fork to a constant speed according to the operation amount of the manual lever 314. Therefore, the operability and power consumption of the battery-type forklift can be improved at the same time.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. The present embodiment is different from the first embodiment in that the load of the generator 43 is changed according to the pressure of the first pilot line 33. Hereinafter, the difference will be mainly described. In each of the following embodiments, the same reference numerals are used for portions that perform the same functions as those of the first embodiment described above, and repeated descriptions are omitted as appropriate.

  FIG. 2 is a schematic configuration diagram of a regenerative hydraulic control device 100 for a battery-type forklift according to a second embodiment of the present invention.

  The regenerative hydraulic control device 100 for a battery-type forklift according to the present embodiment includes a pressure sensor 70 that detects the pressure of the first pilot line 33 in the first pilot line 33. Then, the controller 5 controls the power generation amount of the generator 43 according to the detection value of the pressure sensor 70.

  Specifically, when the load of the fork is heavier than a predetermined weight and the regenerative switching valve 41 is switched to the regenerative control position (D), that is, when the first pilot pressure P1 becomes higher than the predetermined pressure. Increases the power generation amount of the generator 43 as the first pilot pressure P1 (detected value of the pressure sensor 70) increases within a range in which the fork descending speed can be maintained at a constant speed.

  Thereby, when the load of a fork is heavy, the amount of power generation can be increased, so that the power generation efficiency can be improved.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. This embodiment is different from the first embodiment in that a pressure control valve 35 is provided in the return line 7. Hereinafter, the difference will be mainly described.

  FIG. 3 is a schematic configuration diagram of a regenerative hydraulic control device 100 for a battery-type forklift according to a third embodiment of the present invention.

  In the regenerative hydraulic control device 100 for a battery-type forklift according to the present embodiment, a pressure control valve 35 is provided in the return line 7, and a check valve 32 is provided in the pump line 6. Then, the pressure acting on the cylinder Iran, that is, the lift load pressure Pload is led as the first pilot pressure P1 to the valve-closing side pressure receiving portion 353 of the pressure control valve 35 and the regenerative pressure receiving portion 415 of the regenerative switching valve 41.

  Even in such a configuration, the differential pressure across the up-and-down switching valve 31 (= P1−P2) is controlled to be constant by the pressure control valve 35, so that the same effect as in the first embodiment can be obtained. Can do.

  Note that the present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  For example, also in the third embodiment, the pressure sensor 70 may be provided in the first pilot line 33, and the power generation amount of the generator 43 may be controlled in the same manner as in the second embodiment according to the detection value of the pressure sensor 70. .

  Moreover, in the said embodiment, although the battery-type forklift was demonstrated to the example, industrial vehicles other than this may be used.

2 Lift cylinder (actuator)
5 Controller (Power generation control means)
7 Return line 8 Cylinder line 10 Regeneration line 11 Battery (capacitor)
13 Hydraulic pump (pump)
31 Elevation switching valve (Direction switching valve)
35 Pressure control valve 41 Regenerative switching valve 42 Hydraulic motor 43 Generator 70 Pressure detection means

Claims (3)

An actuator driven by a working fluid supplied from a pump;
A direction control valve for switching supply and discharge of the working fluid to and from the actuator;
A cylinder line for guiding the working fluid discharged from the actuator to the directional control valve;
A hydraulic motor driven by the working fluid discharged from the actuator;
A generator that is driven by the hydraulic motor to generate electricity;
A battery for storing electric power generated by the generator;
A regenerative switching valve that controls the amount of working fluid supplied to the hydraulic motor in accordance with the pressure of the cylinder line;
A return line that guides the working fluid discharged from the actuator and passed through the direction control valve to the regeneration switching valve;
A regenerative line for guiding the working fluid discharged from the actuator and passing through the regenerative switching valve to the hydraulic motor;
A pressure control valve for controlling a pressure difference between the pressure of the cylinder line and the pressure of the return line to be constant;
A check valve provided in the cylinder line for restricting the working fluid discharged from the actuator from being guided to the direction control valve;
With
The pressure control valve guides the working fluid discharged from the actuator to the direction control valve so that a pressure difference between the pressure of the cylinder line and the pressure of the return line becomes the constant pressure,
The regenerative switching valve has a spring that presses in a direction opposite to the pressure of the cylinder line acting on the regenerative pressure receiving portion of the regenerative switching valve, and the pressing force by the pressure of the cylinder line is higher than the pressing force of the spring. Increasing the amount of working fluid supplied to the hydraulic motor when it becomes larger;
Industrial vehicle regenerative hydraulic system. The pressure control valve reduces the flow rate of the working fluid discharged from the actuator as the pressure difference between the pressure of the cylinder line and the pressure of the return line becomes higher than a predetermined pressure.
The regenerative hydraulic device for an industrial vehicle according to claim 1. Pressure detecting means for detecting the pressure of the cylinder line;
The power generation amount control means for increasing the power generation amount of the generator as the pressure of the cylinder line increases,
The regenerative hydraulic device for an industrial vehicle according to claim 1 or 2, characterized by comprising:

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