JP6544285B2 - Industrial vehicle - Google Patents

Description

  The present invention relates to an industrial vehicle.

  As an industrial vehicle which drives hydraulic equipment with an engine and a motor generator, it describes in patent document 1, for example. The industrial vehicle described in Patent Document 1 includes a variable displacement pump driven by a drive unit having an engine and a motor generator, and a variable displacement pump driven only by a motor. Hydraulic equipment is supplied with hydraulic fluid from two variable displacement pumps. The variable displacement pump is a swash plate type whose capacity is changed according to the inclination angle of the swash plate.

Re-issued patent WO 2011/04061

  By the way, as a variable displacement pump, the inclination angle of the swash plate may be changed according to the pilot hydraulic pressure, and the capacity may be changed accordingly. This type of variable displacement pump has a maximum displacement when the pilot hydraulic pressure is not applied by the hydraulic fluid. Therefore, when starting the drive unit, the variable displacement pump has the maximum displacement, and the load on the drive unit is large.

  An object of the present invention is to provide an industrial vehicle capable of reducing the load of a drive unit having an engine and a motor generator.

  An industrial vehicle that solves the above problems includes a hydraulic device, a variable displacement pump that supplies hydraulic fluid with a discharge amount corresponding to the pilot hydraulic pressure to the hydraulic device, an engine and a motor generator, and driving the variable displacement pump A drive unit serving as a source, a fixed displacement pump for supplying hydraulic fluid to the hydraulic device, a motor serving as a drive source for the fixed displacement pump, and discharge of hydraulic fluid from the fixed displacement pump when starting the drive unit And a control unit for starting the drive unit in a state where the variable displacement pump has a minimum displacement with a pilot hydraulic pressure applied by the hydraulic fluid.

  According to this, since it is possible to start the drive unit after setting the variable displacement pump to the minimum displacement using the hydraulic fluid discharged from the fixed displacement pump, the load on the drive unit is reduced.

For the industrial vehicle, the control unit maintains the variable displacement pump at the minimum displacement at the time of idling stop of the engine.
During idling stop, the engine can be started again for a short time. For this reason, at the time of idling stop, the load of the drive unit at the time of idling stop cancellation can be reduced by maintaining a variable displacement pump at minimum capacity.

  According to the present invention, it is possible to reduce the load of a drive unit having an engine and a motor generator.

The schematic block diagram of a forklift. The figure for demonstrating the process which a control apparatus performs. The flowchart which shows the process which a control apparatus performs at the time of starting of a drive unit.

Hereinafter, an embodiment of an industrial vehicle will be described.
As shown in FIG. 1, a forklift 10 as an industrial vehicle includes a cargo handling device 11. The cargo handling apparatus 11 includes a multistage mast 14 composed of a pair of left and right outer masts 12 and an inner mast 13. A hydraulic tilt cylinder 15 is connected to the outer mast 12. A hydraulic lift cylinder 16 is connected to the inner mast 13. The mast 14 performs a forward or backward tilting operation in the front-rear direction of the vehicle body by supplying and discharging the hydraulic oil to the tilt cylinder 15. The inner mast 13 vertically raises and lowers the vehicle body by supplying and discharging the hydraulic oil to the lift cylinder 16. Further, the inner mast 13 is provided with a fork 18 via a lift bracket 17. The fork 18 moves up and down together with the lift bracket 17 as the inner mast 13 moves up and down along the outer mast 12 by the operation of the lift cylinder 16.

  The forklift 10 includes a tilt lever 19 operated by a driver and a lift lever 20. The mast 14 tilts in response to the operation of the tilt lever 19. The mast 14 moves up and down according to the operation of the lift lever 20. The forklift 10 includes a tilt sensor 21 for detecting an operation amount of the tilt lever 19, a lift sensor 22 for detecting an operation amount of the lift lever 20, and a control device 23 for outputting detection results of the tilt sensor 21 and the lift sensor 22. And. The control device 23 as a control unit performs control of the forklift 10 in an integrated manner. The control device 23 may be configured by a plurality of ECUs (Electronic Control Units) and a command unit that gives commands to the ECUs.

  The forklift 10 includes a hydraulic mechanism 31 that supplies hydraulic fluid to various hydraulic devices such as the lift cylinder 16 and the tilt cylinder 15 described above, a hydraulic power steering device, and a brake device. The hydraulic mechanism 31 is controlled by the control device 23 to supply and discharge the hydraulic oil to each hydraulic device.

  The forklift 10 includes a variable displacement pump 41 and a fixed displacement pump 51 for supplying hydraulic fluid to hydraulic equipment via a hydraulic mechanism 31, a drive unit 42 serving as a drive source of the variable displacement pump 41, and a fixed displacement pump 51. And a motor 52 serving as a driving source. In addition, the forklift 10 includes an oil tank T in which hydraulic oil is stored.

  Drive unit 42 includes motor generator 43 and engine 44. The motor generator 43 has a function as an electric motor and a function as a generator. The drive unit 42 drives the variable displacement pump 41 by two drive sources of the engine 44 and the motor generator 43 that compensates for the output of the engine 44.

  Forklift 10 includes power storage device 32 serving as an electric power source for motor generator 43 and motor 52, inverter 45 that converts DC power of power storage device 32 into AC power and supplies the AC power to motor generator 43, and DC power of power storage device 32. And an inverter 53 for converting into AC power and supplying the same to the motor 52. Power storage device 32 is a battery in which a plurality of secondary battery cells are modularized. Power storage device 32 may be used also as a power source of a traveling motor for causing forklift 10 to travel, or may be a dedicated power source of motor generator 43 and motor 52.

  The variable displacement pump 41 is provided with a swash plate 46, and is of a swash plate type whose capacity is changed according to the inclination angle of the swash plate 46. The forklift 10 includes a hydraulic cylinder 47 having a piston connected to the swash plate 46. In the hydraulic cylinder 47, the piston moves according to the pilot hydraulic pressure, and the inclination angle of the swash plate 46 changes integrally with the piston. Therefore, the variable displacement pump 41 is a pump whose capacity (discharge amount) per rotation changes according to the pilot hydraulic pressure.

  The drive unit 42 and the motor 52 are controlled by the controller 23. Specifically, the control device 23 controls the output of the engine 44 by controlling the fuel injection amount and the like. Further, control device 23 controls the outputs of motor generator 43 and motor 52 by controlling inverters 45 and 53.

  The forklift 10 includes a first oil passage 61 connected to the variable displacement pump 41, a second oil passage 62 connected to the fixed displacement pump 51, and hydraulic oil and a second oil passage supplied to the first oil passage 61. And a combined oil passage 63 where the hydraulic oil supplied to the unit 62 merges. The first oil passage 61 and the combined oil passage 63 are connected via a first check valve 64. The second oil passage 62 and the combined oil passage 63 are connected via a second check valve 65. The first check valve 64 and the second check valve 65 are for preventing backflow of hydraulic oil from the combined oil passage 63 to the respective oil passages 61 and 62.

  The forklift 10 includes a connection oil passage 66 connecting the combined oil passage 63 and the hydraulic mechanism 31. The hydraulic oil supplied from the variable displacement pump 41 and the fixed displacement pump 51 flows through the combined oil passage 63 and the connection oil passage 66, and is supplied to the hydraulic mechanism 31. The hydraulic mechanism 31 supplies hydraulic fluid to hydraulic equipment. Thus, the hydraulic device is driven.

  The forklift 10 includes a control valve 68, a first pilot oil passage 67 connecting the combined oil passage 63 and the control valve 68, and a second pilot oil passage 69 connecting the control valve 68 and the hydraulic cylinder 47. . In each of the pilot oil passages 67 and 69, the hydraulic oil flowing through the combined oil passage 63, that is, the hydraulic oil discharged from the variable displacement pump 41 and the hydraulic oil discharged from the fixed displacement pump 51 flow. The control valve 68 is controlled by the controller 23 to control the supply and discharge of hydraulic oil to the hydraulic cylinder 47 via the pilot oil passages 67 and 69.

Next, the control performed by the control device 23 will be described together with the operation.
The control device 23 calculates the hydraulic load (flow of necessary hydraulic fluid) from the operation amount of the lift lever 20, the tilt lever 19 and the like, and controls the variable displacement pump 41 and the fixed displacement pump 51 according to the hydraulic load. .

  As shown in FIG. 2, the control device 23 drives the motor 52 to drive the fixed displacement pump when the flow rate (amount of oil) of the hydraulic oil required to drive the hydraulic device can be secured by driving the fixed displacement pump 51. Discharge the hydraulic oil from 51. The discharge amount of the hydraulic oil discharged from the fixed displacement pump 51 can be changed by changing the output of the motor 52. The control device 23 supplies the hydraulic oil according to the hydraulic device by raising the output of the motor 52 according to the increase of the hydraulic load.

  The control device 23 drives the drive unit 42 instead of the motor 52 to discharge the hydraulic oil from the variable displacement pump 41 when the required displacement can not be secured by the driving of the fixed displacement pump 51. The controller 23 drives the engine 44 to supply the hydraulic oil when the required amount of oil can be secured by driving the engine 44. In addition, when the control device 23 monitors the remaining capacity (charging rate) of the storage device 32 and determines that the storage device 32 needs to be charged, the output of the engine 44 is higher than that required to drive the hydraulic device. The output is increased to cause the motor generator 43 to generate power. The remaining capacity of power storage device 32 is calculated from the current and voltage of power storage device 32 detected by a current sensor and a voltage sensor (not shown).

  When the required amount of oil can not be secured by the driving of the engine 44, the control device 23 causes the motor generator 43 to perform powering to assist the engine 44. The discharge amount of the hydraulic oil discharged from the variable displacement pump 41 can be changed by changing the output of the drive unit 42 and the inclination angle of the swash plate 46. The controller 23 changes the output of the drive unit 42 and the inclination angle of the swash plate 46 according to the increase of the hydraulic load to supply the hydraulic oil according to the hydraulic load. The controller 23 operates the motor 52 from the fixed displacement pump 51 and the variable displacement pump 41 by driving the motor 52 in addition to the drive unit 42 when the required amount of oil can not be secured by the drive of the drive unit 42. Discharge the oil.

  By the way, when the pilot hydraulic pressure is not applied to the hydraulic cylinder 47, the variable displacement pump 41 has the maximum displacement. That is, in the state where the hydraulic oil is not supplied to the merging oil passage 63, the variable displacement pump 41 has the maximum displacement. In addition, when the environmental temperature is low, such as in winter, the temperature of the hydraulic oil decreases in accordance with the environmental temperature, and the viscosity increases. Furthermore, when the environmental temperature is low, the output of the power storage device 32 may be reduced. These factors can cause the drive unit 42 to be overloaded when starting the drive unit 42. In the present embodiment, when starting the drive unit 42, the load of the drive unit 42 is reduced by performing the following control.

  As shown in FIG. 3, when the drive unit 42 is started, the control device 23 first causes the fixed displacement pump 51 to discharge hydraulic oil by driving the motor 52 (step S11). The hydraulic oil discharged from the fixed displacement pump 51 flows into the combined oil passage 63 via the second oil passage 62.

  Next, the control device 23 controls the control valve 68 to introduce hydraulic fluid to the hydraulic cylinder 47 and apply pilot hydraulic pressure so that the variable displacement pump 41 has a minimum displacement (step S12).

  Next, the control device 23 discharges the hydraulic oil from the variable displacement pump 41 by starting the drive unit 42 (step S13). That is, by driving the pumps in the order of the fixed displacement pump 51 → the variable displacement pump 41, the variable displacement pump 41 having the minimum displacement is driven by using the hydraulic oil supplied from the fixed displacement pump 51. . Here, the minimum capacity indicates a capacity (minimum load capacity) at which the load of the drive unit 42 is minimized.

  Next, the control device 23 determines whether the release condition is satisfied (step S14). The controller 23 maintains the variable displacement pump 41 at the minimum displacement until the release condition is satisfied. As the release condition, for example, the rotation speed of the engine 44 may reach a predetermined rotation speed. The predetermined rotational speed is, for example, the rotational speed at the time of idling. When the release condition is satisfied, the control device 23 sets the displacement of the variable displacement pump 41 to a displacement corresponding to the hydraulic load (step S15), and ends the processing.

  In addition, at the time of idling stop where the engine 44 is temporarily stopped, the engine 44 can be restarted for a short time. If the variable displacement pump 41 is set to the minimum displacement by using the hydraulic fluid discharged from the fixed displacement pump 51 every time the engine 44 is restarted, it takes time to restart the engine 44. Therefore, the control device 23 controls the control valve 68 to maintain the variable displacement pump 41 at the minimum displacement when the engine 44 is started after the start of the engine 44 under the control shown in FIG. . At this time, the control device 23 causes the fixed displacement pump 51 to discharge the hydraulic fluid by driving the motor 52, and a pilot hydraulic pressure is applied by the hydraulic fluid.

  When the engine 44 can be restarted in a short time, maintaining the variable displacement pump 41 at the minimum displacement can reduce the time required for restarting the engine 44 and can also reduce the load on the motor 52. it can.

Note that the determination as to whether or not the engine 44 is to be stopped by idling is determined by the control device 23 based on, for example, the hydraulic load, the temperature of the engine 44 and the like.
Therefore, according to the above embodiment, the following effects can be obtained.

  (1) When the drive unit 42 is started, the drive unit 42 is started after the variable displacement pump 41 has a minimum displacement by the hydraulic fluid discharged from the fixed displacement pump 51. Therefore, the load on the drive unit 42 can be reduced. By reducing the load on the drive unit 42, the startability of the drive unit 42 is improved. The fixed displacement pump 51 has a fixed capacity (discharge amount) per one rotation, and the load of the motor 52 does not become excessively large. Even when hydraulic oil is supplied using the fixed displacement pump 51 when starting the drive unit 42, the load on the motor 52 is light. Therefore, the load on the entire forklift 10 is reduced as compared to the case where the hydraulic fluid is supplied to the hydraulic device only by the variable displacement pump 41.

(2) Since the variable displacement pump 41 is maintained at the minimum displacement at the time of idling stop, the load on the drive unit 42 when the idling stop is canceled is reduced.
(3) In an industrial vehicle that supplies hydraulic oil by a plurality of pumps, at least one is a fixed displacement pump 51 driven by only the motor 52. Therefore, the hydraulic fluid can be supplied to the hydraulic device even if the engine 44 is stopped.

  (4) The variable displacement pump 41 and the fixed displacement pump 51 are used in combination. The fixed displacement pump 51 is cheaper and smaller than the variable displacement pump 41. Therefore, compared with the case where the variable displacement pump 41 is used instead of the fixed displacement pump 51, the manufacturing cost can be reduced and the space can be saved.

The embodiment may be modified as follows.
The control device 23 may set the cancellation condition that a predetermined time has elapsed since the engine 44 was started, instead of the engine 44 reaching the predetermined rotation speed.

The variable displacement pump 41 may be different from the swash plate type as long as the capacity is changed by the pilot hydraulic pressure.
A plurality of variable displacement pumps 41 may be provided.

  ○ The industrial vehicle may be a construction machine such as a hydraulic shovel. In this case, examples of the hydraulic device include a boom cylinder that drives a boom, an arm cylinder that drives an arm, and a bucket cylinder that drives a bucket.

  The hydraulic device is not limited to the one described in the embodiment, and may be a hydraulic motor or the like. In addition, when the attachment is equipped, it may be a hydraulic cylinder that operates the attachment. As the attachment, for example, a shifter for moving the fork 18 in the left-right direction, a clamp for holding the object, etc. may be mentioned.

  The control valve 68 may be controlled so that the pilot hydraulic pressure is not applied to the hydraulic cylinder 47 when the engine 44 is temporarily stopped, such as during idling stop. In this case, each time the engine 44 is restarted, the variable displacement pump 41 is minimized by using the hydraulic oil discharged from the fixed displacement pump 51.

  The upper limit may be set to the output (supplied power) [kw] to the motor 52, and the upper limit may be changed according to the remaining capacity of the storage device 32. By setting the upper limit to the output to the motor 52, the work ratio of the variable displacement pump 41 and the fixed displacement pump 51 can be determined. When the remaining capacity of the storage device 32 is small, the work interest rate of the motor 52 can be lowered to prevent the remaining capacity of the storage device 32 from running out.

  The motor 52 may be controlled to be pressure-compensated with respect to the pressure of the hydraulic oil merged in the merging oil path 63. Since the variable displacement pump 41 changes the displacement according to the hydraulic load, the pressure of the hydraulic oil supplied to the hydraulic device is likely to fluctuate accordingly. By adjusting the number of revolutions of the motor 52 in accordance with the change of the displacement of the variable displacement pump 41, it is possible to reduce the fluctuation of the pressure of the hydraulic oil merged in the merging oil path 63.

  The industrial vehicle may travel by driving a hydraulic motor.

  DESCRIPTION OF SYMBOLS 10 ... Forklift, 15 ... Tilt cylinder, 16 ... Lift cylinder, 23 ... Control apparatus, 41 ... Variable displacement pump, 42 ... Drive unit, 43 ... Motor generator, 44 ... Engine, 46 ... Swash plate, 47 ... Hydraulic cylinder, 51 ... fixed displacement pump, 52 ... motor.

Claims (2)

Hydraulic equipment,
A variable displacement pump that supplies hydraulic fluid of a discharge amount corresponding to a pilot hydraulic pressure to the hydraulic device;
A drive unit having an engine and a motor generator and serving as a drive source of the variable displacement pump;
A fixed displacement pump for supplying hydraulic fluid to the hydraulic device;
A motor serving as a drive source of the fixed displacement pump;
A control unit configured to discharge hydraulic fluid from the fixed displacement pump when starting the drive unit, and to start the drive unit in a state where the variable displacement pump has a minimum displacement with a pilot hydraulic pressure applied by the hydraulic fluid; Industrial vehicles equipped with   The industrial vehicle according to claim 1, wherein the control unit maintains the variable displacement pump in the minimum displacement state at the time of idling stop of the engine.

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