JP2017186127A - Industrial vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a burden on a drive unit which includes an engine and a motor generator.SOLUTION: A fork lift 10 includes a variable capacity pump 41 and a fixed capacity pump 51 for supplying a hydraulic oil to a hydraulic apparatus through a hydraulic mechanism 31, a drive unit 42 which is a drive source for the variable capacity pump 41, and a motor 52 which is a drive source for the fixed capacity pump 51. A control device 23, when starting the drive unit 42, allows the variable capacity pump 41 to be a minimum capacity by the hydraulic oil that is discharged from the fixed capacity pump 51, and then, starts the drive unit 42.SELECTED DRAWING: Figure 1

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 documents 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 oil is supplied from two variable displacement pumps to the hydraulic equipment. The variable displacement pump is a swash plate type in which the capacity changes according to the inclination angle of the swash plate.

Re-published patent WO2011 / 034061

  By the way, there is a case where a variable displacement pump is used in which the inclination angle of the swash plate changes according to the pilot oil pressure, and the displacement changes accordingly. This type of variable displacement pump has a maximum capacity when no pilot oil pressure is applied by hydraulic oil. Therefore, when starting the drive unit, the variable displacement pump has the maximum capacity, and the load on the drive unit is large.

  The objective of this invention is providing the industrial vehicle which can reduce the load of the drive unit which has 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 oil to the hydraulic device with a discharge amount corresponding to a pilot oil pressure, an engine, and a motor generator, and drives the variable displacement pump. A drive unit that is a source, a fixed displacement pump that supplies hydraulic oil to the hydraulic device, a motor that is a drive source of the fixed displacement pump, and discharges the hydraulic oil from the fixed displacement pump when the drive unit is started And a control unit that starts the drive unit in a state where the variable displacement pump is at a minimum capacity with a pilot hydraulic pressure applied by the hydraulic oil.

  According to this, since the drive unit can be started after the variable displacement pump is set to the minimum displacement using the hydraulic oil 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 a minimum capacity when the engine is idling stopped.
When idling is stopped, the engine can be started again in 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 the variable displacement pump at the minimum capacity.

  ADVANTAGE OF THE INVENTION According to this invention, the load of the drive unit which has an engine and a motor generator can be reduced.

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 device 11 includes a multistage mast 14 including 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 tilt operation or a rear tilt operation in the front-rear direction of the vehicle body by supplying and discharging hydraulic oil to and from the tilt cylinder 15. The inner mast 13 moves up and down in the vertical direction of the vehicle body by supplying and discharging hydraulic oil to and from the lift cylinder 16. 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 when 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 according 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 that detects an operation amount of the tilt lever 19, a lift sensor 22 that detects an operation amount of the lift lever 20, and a control device 23 that outputs detection results of the tilt sensor 21 and the lift sensor 22. . The control device 23 as a control unit controls the forklift 10 in an integrated manner. In addition, the control apparatus 23 may be comprised by several ECU (Electronic Control Unit) and the command part which gives a command with respect to this ECU.

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

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

  The drive unit 42 includes a motor generator 43 and an engine 44. The motor generator 43 has both 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 an engine 44 and a motor generator 43 that supplements the output of the engine 44.

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

  The variable displacement pump 41 is a swash plate type that includes a swash plate 46 and whose capacity changes according to the inclination angle of the swash plate 46. The forklift 10 includes a hydraulic cylinder 47 having a piston connected to a 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 together 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 control device 23. Specifically, the control device 23 controls the output of the engine 44 by controlling the fuel injection amount and the like. The control device 23 controls the outputs of the motor generator 43 and the motor 52 by controlling the 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 second oil passage supplied to the first oil passage 61. And a joining oil passage 63 where the hydraulic oil supplied to 62 joins. The first oil passage 61 and the merging oil passage 63 are connected via a first check valve 64. The second oil passage 62 and the merging 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 the backflow of hydraulic oil from the merged oil passage 63 to the oil passages 61 and 62.

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

  The forklift 10 includes a control valve 68, a first pilot oil passage 67 that connects the merging oil passage 63 and the control valve 68, and a second pilot oil passage 69 that connects the control valve 68 and the hydraulic cylinder 47. . In each of the pilot oil passages 67 and 69, the hydraulic oil flowing in the merged 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 flows. Control of the control valve 68 by the control device 23 controls the supply and discharge of hydraulic oil to and from 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 a hydraulic load (necessary hydraulic oil flow rate) from the operation amount of the lift lever 20 and the tilt lever 19 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 of the hydraulic oil (oil amount) necessary for driving the hydraulic equipment can be secured by driving the fixed displacement pump 51. Hydraulic oil is discharged from 51. The amount of 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 hydraulic oil corresponding to the hydraulic equipment by increasing the output of the motor 52 in response to an increase in the hydraulic load.

  When the required oil amount cannot be secured by driving the fixed displacement pump 51, the control device 23 drives the drive unit 42 instead of the motor 52 and discharges hydraulic oil from the variable displacement pump 41. When the required amount of oil can be secured by driving the engine 44, the control device 23 drives the engine 44 to supply hydraulic oil. In addition, the control device 23 monitors the remaining capacity (charging rate) of the power storage device 32 and determines that the power storage device 32 needs to be charged. 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 cannot be secured by driving the engine 44, the control device 23 powers the motor generator 43 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 control device 23 supplies hydraulic oil corresponding to the hydraulic load by changing the output of the drive unit 42 and the inclination angle of the swash plate 46 according to the increase of the hydraulic load. The control device 23 operates from both 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 cannot be secured by driving the drive unit 42. Let the oil discharge.

  By the way, when the pilot hydraulic pressure is not applied to the hydraulic cylinder 47, the variable displacement pump 41 has the maximum capacity. In other words, the variable displacement pump 41 has a maximum capacity in a state in which hydraulic oil is not supplied to the merged oil passage 63. 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. Due to these factors, when the drive unit 42 is started, an excessive load may be generated in the drive unit 42. In the present embodiment, when the drive unit 42 is started, the following control is performed to reduce the load on the drive unit 42.

  As shown in FIG. 3, when starting the drive unit 42, the control apparatus 23 first discharges hydraulic oil from the fixed capacity pump 51 by driving the motor 52 (step S11). The hydraulic oil discharged from the fixed displacement pump 51 flows into the merged oil passage 63 via the second oil passage 62.

  Next, the control device 23 controls the control valve 68 to introduce hydraulic oil into 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 starts the drive unit 42 to discharge the hydraulic oil from the variable displacement pump 41 (step S13). That is, by driving the pumps in the order of the fixed capacity pump 51 → the variable capacity pump 41, the variable capacity pump 41 having the minimum capacity is driven using the hydraulic oil supplied from the fixed capacity pump 51. . In addition, the minimum capacity | capacitance here shows the capacity | capacitance (minimum load capacity | capacitance) from which the load of the drive unit 42 becomes the minimum.

  Next, the control device 23 determines whether a release condition is satisfied (step S14). The control device 23 maintains the variable displacement pump 41 at the minimum capacity until the release condition is satisfied. As a cancellation condition, for example, the rotational speed of the engine 44 reaches a predetermined rotational speed. The predetermined rotational speed is, for example, the rotational speed during 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 process.

  Further, at the time of idling stop when the engine 44 is temporarily stopped, the engine 44 can be restarted in a short time. If the variable displacement pump 41 is set to the minimum capacity by using the hydraulic oil discharged from the fixed displacement pump 51 each 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 capacity when the engine 44 is idling stopped after the engine 44 is started by the control shown in FIG. . At this time, the control device 23 drives the motor 52 to discharge hydraulic oil from the fixed displacement pump 51, and pilot hydraulic pressure is applied by the hydraulic oil.

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

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

  (1) When starting the drive unit 42, the drive unit 42 is started after the variable displacement pump 41 is set to the minimum capacity by the hydraulic oil discharged from the fixed displacement pump 51. For this reason, the load of 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 capacity pump 51 has a fixed capacity (discharge amount) per rotation, and the load on the motor 52 does not become excessively large. Even when hydraulic oil is supplied using the fixed displacement pump 51 when the drive unit 42 is started, the load on the motor 52 is small. Therefore, the load on the forklift 10 as a whole is reduced as compared with the case where hydraulic oil is supplied to the hydraulic equipment only by the variable displacement pump 41.

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

  (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.

In addition, you may change embodiment as follows.
The control device 23 may use the release condition that a predetermined time elapses after the engine 44 is 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 displacement changes depending on 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 excavator. In this case, examples of hydraulic equipment 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 that described in the embodiment, and may be a hydraulic motor or the like. Moreover, when the attachment is equipped, the hydraulic cylinder which operates an attachment may be sufficient. Examples of the attachment include a shifter that moves the fork 18 in the left-right direction, a clamp that sandwiches the object, and the like.

  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 when idling is stopped. In this case, every time the engine 44 is restarted, the variable capacity pump 41 is set to the minimum capacity by using the hydraulic oil discharged from the fixed capacity pump 51.

  An upper limit may be set for the output (supplied power) [kw] to the motor 52, and this upper limit may be changed according to the remaining capacity of the power storage device 32. By setting an upper limit for the output to the motor 52, the work ratio between the variable displacement pump 41 and the fixed displacement pump 51 can be determined. When the remaining capacity of the power storage device 32 is small, it is possible to prevent the remaining capacity of the power storage device 32 from being exhausted by reducing the work rate of the motor 52.

  The motor 52 may be controlled so that pressure compensation is performed with respect to the pressure of the working oil that has joined in the joining oil passage 63. Since the variable displacement pump 41 changes its capacity according to the hydraulic load, the pressure of the hydraulic oil supplied to the hydraulic equipment is likely to fluctuate accordingly. By adjusting the rotation speed of the motor 52 in accordance with the change in the capacity of the variable displacement pump 41, it is possible to reduce fluctuations in the pressure of the hydraulic oil joined in the merged oil passage 63.

  The industrial vehicle may be driven by driving a hydraulic motor.

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

Claims (2)

Hydraulic equipment,
A variable displacement pump for supplying hydraulic oil with 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 oil to the hydraulic equipment;
A motor as a drive source of the fixed displacement pump;
At the time of starting the drive unit, a control unit that discharges hydraulic oil from the fixed displacement pump and starts the drive unit in a state where the variable displacement pump is at a minimum capacity with a pilot hydraulic pressure applied by the hydraulic oil; Industrial vehicle equipped with.   The industrial vehicle according to claim 1, wherein the control unit maintains the variable displacement pump at a minimum capacity when the engine is idling stopped.

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