JP2015132168A - Power control device for cargo handling vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power control device for a cargo handling vehicle capable of improving fuel economy while preventing an engine stall at engine idling.SOLUTION: A power control device 14 includes an accelerator opening sensor 15 for detecting an accelerator opening, a main control unit 18, and an engine ECU 19. The main control unit 18 has a torque limit value setting section 21 for setting an engine torque limit value for controlling torque of an engine 5. The torque limit value setting section 21 sets the engine torque limit value to be a torque limit value A so that an engine stall can be prevented with respect to a cargo handling load of a maximum load when an accelerator is turned off, and changes the engine torque limit value to be a torque limit value B lower than the toque limit value A when the accelerator is depressed, and returns the engine torque limit value to the torque limit value A when the accelerator is returned. The engine ECU 19 controls engine torque with the usage of the engine torque limit value.

Description

  The present invention relates to a power control device for a cargo handling vehicle equipped with an engine.

  As a conventional power control device for a cargo handling vehicle, for example, as described in Patent Document 1, a control command for obtaining an engine speed corresponding to an accelerator pedal depression operation amount is generated, and the control command is It is known to control engine output torque. In such a cargo handling vehicle, realization of fuel saving is strongly desired. In some hybrid vehicles, as described in Patent Document 2, for example, by pressing an eco switch, the required torque during normal operation is switched to the required torque during energy saving to improve fuel efficiency.

JP 2012-56763 A JP 2008-105532 A

  In the hybrid vehicle as described in Patent Document 2, the engine output is supplemented with the motor output in the eco mode to improve the fuel efficiency while maintaining the vehicle performance (required torque). In an engine-type cargo handling vehicle in which a motor is not mounted as described in Patent Document 1, fuel efficiency may be improved by limiting the engine torque in the eco mode. However, if the engine torque limit is increased in order to improve fuel efficiency, the engine may lose output due to a sudden change in the cargo handling load when the cargo handling device has a heavy load in the engine idle state, and engine stall may occur. There may be a problem specific to cargo handling vehicles.

  An object of the present invention is to provide a power control device for a cargo handling vehicle capable of improving fuel efficiency while preventing engine stall at engine idling.

  The present invention relates to a power control device for a cargo handling vehicle having a cargo handling device that is operated by hydraulic oil from a hydraulic pump driven by an engine, an accelerator opening detection means that detects an accelerator opening of the cargo handling vehicle, an accelerator opening Torque limit value determining means for determining an engine torque limit value for limiting the engine torque based on the accelerator opening detected by the degree detection means, and an engine torque limit value determined by the torque limit value determining means And an engine torque control means for controlling the engine torque, and the torque limit value determining means determines the engine torque limit value as the first torque limit value when the accelerator depression is not detected by the accelerator opening detection means. When the accelerator depression is detected by the accelerator opening detection means, the engine torque is Those characterized by setting a limit value to a second torque limit value is lower than the first torque limit value.

  Thus, in the power control device of the present invention, the opening degree of the accelerator of the cargo handling vehicle is detected, the engine torque limit value for limiting the engine torque is determined based on the opening degree of the accelerator, and the engine The torque of the engine is controlled using the torque limit value. At this time, when the depression of the accelerator is not detected, the engine torque limit value is set to the first torque limit value. For example, the first torque limit value is a value that does not cause an engine stall with respect to the maximum load handling load. As a result, engine stall due to sudden changes in cargo handling load in the engine idle state is suppressed. On the other hand, when depression of the accelerator is detected, the engine torque limit value is set to a second torque limit value that is lower than the first torque limit value. As a result, when the accelerator is depressed and the engine speed is high and engine stall is unlikely to occur, the engine torque is strongly limited, thus reducing fuel consumption. As described above, fuel efficiency can be improved while preventing engine stall at the time of engine idling.

  The torque limit value determining means may set the engine torque limit value to the first torque limit value when the return of the accelerator is detected by the accelerator opening detecting means.

  In this case, if the engine speed decreases by returning the accelerator, the engine torque limit value returns from the second torque limit value to the first torque limit value. Can be deterred.

  At this time, the torque limit value determining means determines the engine torque limit value when the accelerator opening degree detecting means detects that the accelerator is depressed and the accelerator opening is equal to or greater than the first predetermined value. When the accelerator opening is detected by the accelerator opening detection means and the accelerator opening is detected to be equal to or less than a second predetermined value lower than the first predetermined value, The torque limit value may be set to the first torque limit value.

  Thus, the accelerator is sufficiently depressed by making the threshold (second predetermined value) used when detecting the return of the accelerator lower than the threshold (first predetermined value) used when detecting the depression of the accelerator. When the engine torque limit value is set to the second torque limit value and the accelerator is fully returned, the engine torque limit value is set to the first torque limit value. Therefore, in a state where the engine speed is not sufficiently reduced because the accelerator is not sufficiently returned, the engine torque limit value remains set at the second torque limit value, thereby further improving fuel efficiency. be able to.

  The torque limit value determining means is set to continuously change the engine torque limit value from the first torque limit value to the second torque limit value when accelerator depression is detected by the accelerator opening detecting means. When the accelerator opening is detected by the accelerator opening detecting means, the engine torque limit value may be set to continuously change from the second torque limit value to the first torque limit value.

  In this case, when the accelerator is depressed, the engine torque limit value gradually changes from the first torque limit value to the second torque limit value, and when the accelerator is returned, the engine torque limit value is the second torque limit value. The torque limit value gradually changes from the first torque limit value. Therefore, sudden changes in the traveling speed of the cargo handling vehicle and the cargo handling speed of the cargo handling apparatus can be suppressed. In addition, the engine torque limit value can be changed without causing the driver to feel uncomfortable.

  Further, the first torque limit value may be a value obtained by using the output value of the hydraulic pump when the maximum load handling load is applied to the cargo handling device.

  By using the output value of the hydraulic pump when the maximum load handling load is applied to the cargo handling device in this way, it is possible to easily calculate the first torque limit value that does not cause an engine stall for the maximum load handling load. Can do.

  According to the present invention, it is possible to improve fuel efficiency while preventing engine stall at the time of engine idling.

1 is a configuration diagram illustrating an engine-type forklift power control device together with a schematic configuration of a forklift as an embodiment of a power control device for a cargo handling vehicle according to the present invention. It is a block diagram which shows the function of the main control unit shown in FIG. It is a flowchart which shows the detail of the torque limit value setting process procedure at the time of the eco mode by the torque limit value setting part shown in FIG. It is a time chart which shows an example of the relationship between an accelerator opening and an engine torque limit value.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a power control device for a cargo handling vehicle according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram showing a power control device for an engine-type forklift together with a schematic configuration of a forklift as an embodiment of a power control device for a cargo handling vehicle according to the present invention.

  In the drawing, a forklift 1 includes a cargo handling device 2. The cargo handling device 2 includes a mast 3, a fork 4 that is attached to the mast 3 via a lift bracket (not shown), and loads a load, and a lift cylinder (not shown) that raises and lowers the fork 4, A tilt cylinder (not shown) for tilting the mast 3 forward or backward is provided. The cargo handling device 2 may further include an attachment such as a roll clamp or a drum clamp.

  The forklift 1 includes an engine 5 serving as a driving source for traveling operation and cargo handling operation, a hydraulic pump 6 driven by the engine 5, and between the hydraulic pump 6 and a lift cylinder and a tilt cylinder of the cargo handling device 2. And a control valve 8 that controls the supply of hydraulic oil from the hydraulic pump 6 to the lift cylinder and the tilt cylinder according to the operation amount of the cargo handling lever 7. The engine 5 may be a diesel engine or a gasoline engine. The control valve 8 may be an electromagnetic valve or a mechanical valve.

  The cargo handling lever 7 is a lever for performing a cargo handling operation, and includes a lift lever and a tilt lever. When the lift raising operation is performed by the lift lever, hydraulic oil is pumped from the tank 9 by the hydraulic pump 6, and the hydraulic oil is supplied to the lift cylinder via the control valve 8, so that the fork 4 is raised. When the lift lowering operation is performed by the lift lever, the hydraulic oil from the lift cylinder is returned to the tank 9 via the control valve 8 by the weight of the fork 4. When the tilting operation is performed forward or backward by the tilt lever, the hydraulic oil is pumped from the tank 9 by the hydraulic pump 6 and is supplied to the tilt cylinder via the control valve 8 so that the mast 3 is moved forward. Tilt or tilt backward.

  An axle 12 is connected to the engine 5 via a torque converter 10 and a differential gear 11, and driving wheels 13 are attached to both sides of the axle 12. The output of the engine 5 is transmitted to the drive wheels 13 via the torque converter 10, the differential gear 11 and the axle 12. Instead of the torque converter 10, a manual mission may be provided.

  Further, the forklift 1 includes the power control device 14 of the present embodiment. The power control device 14 includes an accelerator opening sensor 15, an eco mode switch 16, a rotation speed sensor 17, a main control unit 18, and an engine ECU (Electronic Control Unit) 19.

  The accelerator opening sensor 15 is a sensor (accelerator opening detecting means) that detects the amount of depression of the accelerator pedal 20 (accelerator opening). As the accelerator opening sensor 15, for example, a potentiometer is used. The accelerator opening degree detecting means may detect the depression speed of the accelerator pedal 20 and integrate the depression speed to obtain the accelerator opening degree. The eco mode switch 16 is a switch for switching between a normal mode for performing normal operation and an eco mode for performing energy saving (eco) operation. The rotation speed sensor 17 is a sensor that detects the actual rotation speed of the engine 5.

  As shown in FIG. 2, the main control unit 18 includes a torque limit value setting unit 21, a target rotation number setting unit 22, and a storage unit 23. The torque limit value setting unit 21 sets an engine torque limit value for limiting the torque of the engine 5 (engine torque) based on the operation signal of the eco mode switch 16 and the detected value of the accelerator opening sensor 15. The processing function of the torque limit value setting unit 21 will be described in detail later. The target rotational speed setting unit 22 sets a target rotational speed of the engine 5 according to the accelerator opening detected by the accelerator opening sensor 15.

  The storage unit 23 stores torque limit values (torque limit rates) A and B as data used for the engine torque limit value setting process by the torque limit value setting unit 21. Here, the unit of the torque limit values A and B is%.

  The torque limit value A (first torque limit value) is a value that limits the engine torque so that an engine stall is not generated even when the maximum load is applied to the cargo handling device 2 when the engine 5 is in an idle state. is there. The torque limit value A can be calculated from the load of the cargo handling device 2 and the vehicle structure of the forklift 1. The torque limit value A is calculated from the following formula, for example.

Hydraulic pump pressure [Pa] = ((maximum load [kg] + cargo handling equipment weight [kg]) x gravity acceleration [m / s ² ]
÷ Lift cylinder pressure receiving area [m ² ]) + Loss [Pa]
Hydraulic pump flow rate [m ³ / s] = Engine idle speed [rps] x Hydraulic pump capacity [m ³ / rev]
× Hydraulic pump volumetric efficiency [%] ÷ 100
Hydraulic pump output value [W] = Hydraulic pump pressure [Pa] x Hydraulic pump flow rate [m ³ / s]
Torque limit value A * [N] = Hydraulic pump output value [W] ÷ Hydraulic pump overall efficiency [%] × 100
÷ (engine idle speed [rps] x 2 x π) + margin [N]
Torque limit value A [%] = Torque limit value A * [N] ÷ maximum torque [N] × 100

  In the above formula, the loss is a value that takes into account the piping resistance and the pressure loss of each device. The margin is a value that takes into account the load of the engine accessory.

  The torque limit value B (second torque limit value) is a value that limits the engine torque so that the acceleration performance of the forklift 1 is maintained and work efficiency is not lowered. The torque limit value B is a value lower than the torque limit value A (see FIG. 4). The torque limit value B is determined by experiment, for example. The torque limit value A may be determined not by the above calculation but by experiments or the like.

  The torque limit value setting unit 21 sets the engine torque limit value to 100% when the normal mode is selected by the eco mode switch 16. That is, when the normal mode is selected, torque limitation of the engine 5 is not performed.

  The torque limit value setting unit 21 sets the engine torque limit value according to the accelerator opening detected by the accelerator opening sensor 15 when the eco mode is selected by the eco mode switch 16. The details of the torque limit value setting processing procedure in the eco mode by the torque limit value setting unit 21 are shown in FIG. Note that at the start of the torque limit value setting processing procedure, the engine torque limit value is set to the torque limit value A in advance.

  In the figure, first, based on the detected value of the accelerator opening sensor 15, it is determined whether or not the depression of the accelerator pedal 20 is detected (step S101). When depression of the accelerator pedal 20 is detected, it is determined whether or not the accelerator opening detected by the accelerator opening sensor 15 is greater than or equal to a depression threshold (first predetermined value) P (step S102). The stepping-in threshold value P is, for example, 90%. When the accelerator opening is not greater than or equal to the depression threshold P, step S101 is executed again.

  When the accelerator opening is equal to or larger than the depression threshold P, the engine torque limit value is changed from the torque limit value A to the torque limit value B (step S103). At this time, the engine torque limit value is set so as to decrease linearly (continuously) from the torque limit value A to the torque limit value B according to the time change (see FIG. 4).

  Thereafter, based on the detected value of the accelerator opening sensor 15, it is determined whether or not the return of the accelerator pedal 20 is detected (step S104). When the return of the accelerator pedal 20 is detected, it is determined whether or not the accelerator opening detected by the accelerator opening sensor 15 is equal to or less than the return threshold (second predetermined value) Q (step S105). The return threshold Q is a value (for example, 50%) smaller than the depression threshold P. When the accelerator opening is not less than or equal to the return threshold Q, step S104 is executed again.

  When the accelerator opening is equal to or less than the return threshold Q, the engine torque limit value is changed from the torque limit value B to the torque limit value A (step S106). At this time, the engine torque limit value is set so as to increase linearly (continuously) from the torque limit value B to the torque limit value A according to the time change (see FIG. 4). Thereafter, step S101 is executed again.

  Returning to FIG. 2, the engine ECU 19 is set by the actual rotational speed of the engine 5 detected by the rotational speed sensor 17, the target rotational speed of the engine 5 set by the target rotational speed setting unit 22, and the torque limit value setting unit 21. The engine torque (power) is controlled based on the engine torque limit value.

  Specifically, the engine ECU 19 calculates a deviation between the target rotational speed of the engine 5 and the actual rotational speed of the engine 5, obtains an engine torque command value such that the deviation becomes zero, and calculates the engine torque command value. Correction is made with the engine torque limit value, and the corrected engine torque command value is sent to the engine 5 as a command signal.

  For example, when the normal mode is selected with the eco mode switch 16, the engine torque limit value is 100%, and therefore the engine torque command value is sent to the engine 5 as a command signal as it is. When the eco mode is selected with the eco mode switch 16 and the engine torque limit value is the torque limit value A, A% of the engine torque command value is sent to the engine 5 as a command signal. When the eco mode is selected by the eco mode switch 16 and the engine torque limit value is the torque limit value B, B% of the engine torque command value is sent to the engine 5 as a command signal.

  When the engine 5 is a diesel engine, a command signal is sent to the fuel injection valve. At this time, in the eco mode, the fuel injection amount by the fuel injection valve is limited, and as a result, the engine torque is limited. When the engine 5 is a gasoline engine, a command signal is sent to the throttle valve. At this time, in the eco mode, the opening of the throttle valve, that is, the amount of intake air to the engine 5 is limited, and as a result, the engine torque is limited.

  In the above, the torque limit value setting unit 21 and the storage unit 23 are engine torques for limiting the torque of the engine 5 based on the accelerator opening detected by the accelerator opening detecting means (accelerator opening sensor 15). Torque limit value determining means for determining the limit value is configured. The engine ECU 19 constitutes engine torque control means for controlling the torque of the engine 5 using the engine torque limit value determined by the torque limit value determination means.

Next, the operation of the power control device 14 of this embodiment will be described with reference to FIG. At time t _0, the accelerator pedal 20 is in the OFF state (accelerator opening is 0%), the engine torque limit value is set to the torque limit value A. As described above, the torque limit value A is a value that limits the engine torque so as not to stall against the maximum load handling load. As a result, when the cargo handling device 2 has a heavy load in the idle state of the engine 5 (engine idle state), the engine 5 is prevented from losing its output due to sudden fluctuations in the cargo handling load. That is, the engine stall resistance during engine idling can be maintained.

Thereafter, when the accelerator pedal 20 is depressed at time t _{1 and the} accelerator opening reaches the depression threshold P at time t ₂ , the engine torque limit value is changed from the torque limit value A to the torque limit value B. At this time, the engine torque limit value gradually decreases from the torque limit value A to the torque limit value B. When the accelerator pedal 20 is stepped on, the engine 5 becomes high in rotation speed, so that engine stall is less likely to occur. In such an area where engine stall is unlikely to occur, a stronger torque limit is applied than in engine idling, independently of engine stall resistance, so that the fuel consumption reduction effect can be maintained.

Then, the accelerator pedal 20 is returned at time t _3, when the accelerator opening degree reaches a threshold Q for return at time t _4, the engine torque limit value is returned from the torque limit value B to the torque limit value A. At this time, the engine torque limit value gradually increases from the torque limit value B to the torque limit value A. As a result, in the state where the rotational speed of the engine 5 is decreasing, when the cargo handling device 2 has a heavy load, it is prevented that the engine is stalled due to a sudden change in the cargo handling load. That is, it is possible to maintain the engine stall resistance in the region where the rotational speed of the engine 5 has decreased.

  As described above, according to the present embodiment, when the engine is idling, the engine torque limit value is set to the torque limit value A so as not to be stalled with respect to the maximum load handling load. Can do. Further, when the accelerator pedal 20 is depressed to an opening corresponding to the depression threshold P, the engine torque limit value is changed to a torque limit value B lower than the torque limit value A, so that fuel consumption can be reduced. Further, when the accelerator pedal 20 is returned to the opening corresponding to the return threshold value Q, the engine torque limit value returns to the torque limit value A, so that engine stall due to cargo handling load can be suppressed. As described above, engine stall at the time of engine idling can be prevented, and fuel consumption can be improved without increasing costs.

  Further, since the return threshold value Q for detecting the return of the accelerator pedal 20 is lower than the threshold value P for detecting the depression of the accelerator pedal 20, when the accelerator pedal 20 is sufficiently depressed, When the torque limit value is changed to the torque limit value B and the accelerator pedal 20 is fully returned, the engine torque limit value returns to the torque limit value A. Therefore, in a state where the rotation speed of the engine 5 is not sufficiently decreased, the engine torque limit value is set to the torque limit value B with priority on fuel consumption. Thereby, the further fuel consumption improvement can be aimed at.

  When the accelerator opening is greater than or equal to the depression threshold P, the engine torque limit value gradually changes from the torque limit value A to the torque limit value B. When the accelerator opening is less than or equal to the return threshold Q, the engine torque limit value. Gradually changes from the torque limit value B to the torque limit value A. For this reason, since rapid engine torque fluctuations are suppressed, the traveling speed of the forklift 1 may change abruptly, or the handling speed of the cargo handling device 2 may change abruptly due to a sudden change in the rotational speed of the hydraulic pump 6. Is prevented. This can prevent the driver from feeling uncomfortable.

  In addition, this invention is not limited to the said embodiment. For example, in the above embodiment, when the engine torque limit value is switched between the torque limit value A and the torque limit value B, the engine torque limit value is linearly changed. If it changes continuously and gradually, the engine torque limit value may be changed nonlinearly.

  Moreover, although the said embodiment controls the engine torque of an engine type forklift, the power control apparatus of this invention is an engine type cargo handling vehicle provided with cargo handling apparatuses, such as a bucket, besides such a forklift. Is also applicable.

  DESCRIPTION OF SYMBOLS 1 ... Forklift (loading vehicle), 2 ... Loading / unloading device, 5 ... Engine, 6 ... Hydraulic pump, 14 ... Power control device, 15 ... Accelerator opening sensor (accelerator opening detection means), 18 ... Main control unit, 19 ... Engine ECU (engine torque control means), 20 ... accelerator pedal, 21 ... torque limit value setting section (torque limit value determination means), 23 ... storage section (torque limit value determination means).

Claims (5)

In a power control device for a cargo handling vehicle provided with a cargo handling device operated by hydraulic oil from a hydraulic pump driven by an engine,
Accelerator opening detection means for detecting the opening of the accelerator of the cargo handling vehicle;
Torque limit value determining means for determining an engine torque limit value for limiting the torque of the engine based on the accelerator opening detected by the accelerator opening detecting means;
Engine torque control means for controlling the torque of the engine using the engine torque limit value determined by the torque limit value determination means,
The torque limit value determining means sets the engine torque limit value to a first torque limit value when the accelerator depression detection means does not detect depression of the accelerator, and the accelerator opening degree detection means When the depression is detected, the engine torque limit value is set to a second torque limit value that is lower than the first torque limit value.   The torque limit value determining means sets the engine torque limit value to the first torque limit value when the accelerator return is detected by the accelerator opening detecting means. Power control device for cargo handling vehicles.   The torque limit value determining means detects the engine torque limit value when the accelerator opening degree detecting means detects the depression of the accelerator and detects that the accelerator opening is equal to or greater than a first predetermined value. Is set to the second torque limit value, the accelerator opening detection means detects the return of the accelerator, and the accelerator opening is equal to or less than a second predetermined value lower than the first predetermined value. 3. The power control apparatus for a cargo handling vehicle according to claim 2, wherein when detected, the engine torque limit value is set to the first torque limit value.   The torque limit value determining means continuously changes the engine torque limit value from the first torque limit value to the second torque limit value when depression of the accelerator is detected by the accelerator opening detection means. And when the return of the accelerator is detected by the accelerator opening detecting means, the engine torque limit value is continuously changed from the second torque limit value to the first torque limit value. The power control apparatus for a cargo handling vehicle according to claim 2 or 3, wherein   5. The first torque limit value is a value obtained by using an output value of the hydraulic pump when a maximum load is applied to the cargo handling device. 6. A power control device for a cargo handling vehicle as described.

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