JP2002095113A - Controller of forklift - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller which can avoid the sudden acceleration of a forklift in a no-load state while the responsiveness in the full-load state is maintained satisfactorily. SOLUTION: This controller controls a forklift in such a manner that a target current value corresponding to an acceleration value sensed by an acceleration value sensing unit is produced (S1 and S2), a current value outputted from a travelling chopper to a travelling motor is to be the target current value (S4) if an acceleration detected by an acceleration detection unit is not larger than a 1st upper limit (NO of S3), or if the detected acceleration is larger than the 1st upper limit and an output current value is larger than the target current value (YES of S3 and NO of S5), and the outputted current value is to be reduced if the detected acceleration is not smaller than a 2nd upper limit larger than the 1st upper limit (YES of S6).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a forklift, which uses a battery mounted on the body of the forklift as a drive source and drives a traveling motor by a motor drive unit.

[0002]

2. Description of the Related Art Conventionally, in a forklift using a battery as a driving source, a maximum output torque of a traveling motor is set so that a hill can be climbed when a full (maximum) load is loaded. The traveling motor is supplied with a current from a battery via a motor driving unit including a chopper circuit. The maximum output from the motor driving unit to the traveling motor is determined based on the maximum output torque generated by the traveling motor. The current value is set. Further, a target current value corresponding to the depression amount of the accelerator pedal (almost proportional) is set, and the motor drive unit is controlled by the control unit such that the output current value of the motor drive unit becomes the target current value at that time.

In the case of a light-weight forklift, in particular, the total weight of the vehicle body at full load, that is, the sum of the vehicle's own weight and load, and the total weight of the vehicle body under no load, that is, the vehicle's own weight are greatly different. There is. Therefore, when the accelerator pedal is depressed to the maximum when there is no load, there is a problem that the acceleration of the vehicle body becomes too large because the total weight of the vehicle body is light.

Therefore, conventionally, when the output current value of the motor drive unit is controlled so as to be equal to the target current value, the following of the output current value to the target current value is slowed down and the method of blunting at that time is controlled. Is adjusted appropriately. Specifically, FIG.
As shown in the figure, when the accelerator pedal is depressed to the maximum, the output current value is controlled so that it does not immediately respond to the depression of the accelerator pedal, gradually increases with a delay in response, and eventually reaches the target current value. You. In this way, by delaying the response time until the output current value reaches the target current value, sudden acceleration of the forklift, particularly when there is no load, is prevented.

[0005]

However, in the acceleration control as described above, the rapid acceleration of the forklift is suppressed when there is no load, but the time until the output current value reaches the target current value when the load is full is delayed. As shown in FIG. 6, the responsiveness of acceleration at the time of load decreases,
In particular, there is a problem that the acceleration at the full load becomes very poor, and the working efficiency is reduced.

In view of the above, the present invention has been made in view of the above-mentioned problems, and has a control for preventing a sudden acceleration at no load while maintaining a good acceleration responsiveness at full load of a forklift. It is intended to provide a device.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a control apparatus for a forklift, which supplies power from a battery mounted on a vehicle body and drives a traveling motor by a motor drive unit. A current value deriving unit that detects a target current value according to the accelerator amount, an acceleration detecting unit that detects an acceleration of the vehicle body, and an output current that is supplied to the traveling motor from the motor driving unit. An output current detecting unit for detecting a value, and a detected acceleration detected by the acceleration detecting unit is a predetermined first.
When not more than the upper limit value, the motor drive unit is controlled such that the output current value becomes the target current value, the detected acceleration is larger than the first upper limit value, and the output current value is larger than the target current value. The motor drive unit is controlled so that the output current value becomes the target current value when the value is large, and the output current value is decreased when the detected acceleration is equal to or more than a second upper value that is larger than the first upper value. And a control unit for controlling the motor drive unit as described above.

According to such a configuration, when the acceleration detected by the acceleration detecting section is equal to or more than the second upper limit, the motor driving section is controlled by the control section so as to reduce the output current value. Excessive acceleration of the forklift in the state can be prevented. On the other hand, when the detected acceleration is equal to or less than the first upper limit, the motor drive unit is controlled so that the output current value becomes the target current value.
Even in the full load state, the forklift can be accelerated with good responsiveness.

Therefore, an appropriate acceleration can be obtained according to the load condition of the forklift such as at full load or no load, and the output of the motor drive unit is controlled to suppress the acceleration at no load as in the related art. Without degrading acceleration at full load, as in the case of delaying the response time of current,
Good acceleration characteristics can be maintained even at full load.

In the present invention, when the output current value is decreased when the detected acceleration is equal to or more than the second upper limit value, the control unit may set the detected acceleration to be smaller than the second upper limit value. The output current value is reduced.

According to this structure, the output current value is reduced so that the detected acceleration becomes smaller than the second upper limit value. Therefore, the acceleration of the forklift at the time of no load is suppressed, and the sudden acceleration is reliably prevented. be able to.

Also, in the present invention, the current value deriving unit may include an accelerator amount detecting unit for detecting the accelerator amount, and a calculation for calculating a target current value corresponding to the accelerator amount detected by the accelerator amount detecting unit. And a unit.

According to such a configuration, since the target current value is calculated by the calculating unit based on the accelerator amount detected by the accelerator amount detecting unit, the relation between the accelerator amount and the target current value is preset in the calculating unit. By doing so, for example, a target current value proportional to the accelerator amount can be derived.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment in which the present invention is applied to a counterbalance type forklift.
This will be described with reference to FIG. 1 is a side view of a forklift according to an embodiment of the present invention, FIG. 2 is a partial connection diagram, FIG. 3 is a block diagram of a control device, FIG. 4 is a flowchart for explaining operation, and FIG. It is an explanatory timing chart.

As shown in FIG. 1, the forklift travels by supplying power to a traveling motor 3 by a battery 2 mounted on a vehicle body 1. At this time, the transmission means (not shown) for transmitting the driving force of the traveling motor 3 to the wheels is operated by operating a directional lever (or a directional switch) 4 for setting one of forward and backward or a neutral state. Switching to the neutral state when the means is moving forward or backward and when parking is performed, and steering is performed by the steering wheel 5. In FIG. 1, reference numeral 6 denotes a mast provided on a front portion of the vehicle body 1, reference numeral 7 denotes a lift bracket provided on the mast 6, reference numeral 8 denotes a pair of forks provided on the lift bracket 7, and reference numeral 9 denotes an accelerator pedal.

The traveling motor 3 is constituted by, for example, a DC series motor which is a DC motor. As shown in FIG. 2, when the main switch 11 is turned on, the output DC power of the battery 2 is smoothed by the smoothing capacitor 12. At the same time, the power is converted into DC power of an arbitrary voltage by a traveling chopper 13 composed of, for example, one field-effect transistor R1, a flywheel diode D1, a plugging braking diode D2, and a contactor MC for forward / reverse switching. Power is supplied to the motor 14.
Here, the traveling chopper 13 corresponds to the motor drive unit of the present invention.

Next, the configuration of the control device will be described.
As shown in FIG. 3, when the depression amount (acceleration amount) A of the accelerator pedal 9 is detected by the accelerator amount detection unit 21, a detection signal proportional to the depression amount A of the accelerator pedal 9 is output to the calculation unit 22. The target current value It proportional to the output of the detection signal is derived by the calculation unit 22.
Thus, the target current value deriving unit 23 is configured by the accelerator amount detecting unit 21 and the calculating unit 22. It should be noted that a target current table in which the depression amount A of the accelerator pedal 9 and the target current value It corresponding to each depression amount A are tabulated is created and stored in a memory. The target current value It corresponding to the depression amount A based on the detection signal may be read from the target current table by the reading unit. In this case, the target current value deriving unit 23 includes the accelerator amount detecting unit 21, the memory storing the target current table, and the reading unit that reads the target current value It from the target current table.

As shown in FIG. 2, a vehicle speed sensor 24 composed of, for example, a rotary encoder is provided on the rotating shaft 15 of the DC series motor 14, and the speed of the vehicle body detected by the vehicle speed sensor 24 is detected. The acceleration G of the vehicle body is derived from the temporal change by the calculation unit 25 and is taken into the control unit 26. Here, the vehicle speed sensor 24 and the calculation unit 25 constitute an acceleration detection unit 27.

Further, a first upper limit G1 serving as a reference when determining the acceleration of the forklift and a second upper limit G1 which is larger than the first upper limit G1.
An acceleration setting unit 30 for inputting the upper limit value G2 is provided, and the upper limit values G1 and G2 input to the acceleration setting unit 30 are taken into the control unit 26. If the upper limit values G1 and G2 can be variably set by the acceleration setting unit 30, the acceleration characteristics according to the forklift use situation and other situations can be obtained.

Further, a control pulse is output from the output command unit 33 to the gate of the transistor R1 of the traveling chopper 13 based on the calculation results of the acceleration comparison calculation unit 31 and the current value comparison calculation unit 32 constituting the control unit 26. The output current to the traveling motor 3 is controlled. At this time, the output current output from the traveling chopper 13 to the traveling motor 3 is detected by the output current detecting unit 34, and the detected output current value I is taken into the current value comparing / calculating unit 32 of the control unit 26. The output current value I output from the traveling chopper 13 to the traveling motor 3 is controlled so as to become the target current value It described above.

Incidentally, the detected acceleration G derived by the acceleration detecting section 27, the first upper limit G1 and the second upper limit G
A comparison operation with each of the two is performed by the acceleration comparison operation unit 31. As a result, when the detected acceleration G is smaller than the first upper limit G1, the traveling commander 33 controls the traveling chopper 13 so that the output current value I becomes the target current value It. When the detected acceleration G is equal to or greater than the first upper limit G1, the target current value It is smaller than the output current value I based on the comparison result between the output current value I and the target current value It by the current value comparison / calculation unit 32. For example, the traveling chopper 13 is controlled such that the output current value I becomes the target current value It. Further, when the detected acceleration G is equal to or greater than the second upper limit G2, the output current value I is reduced to reduce the detected acceleration G to the second upper limit G2.
The output command unit 33 sets the traveling chopper 1 to be smaller.
3 is controlled, and when the detected acceleration G is smaller than the second upper limit G2, the output current value I is maintained as it is.

Next, the operation will be described with reference to the flowchart of FIG.

As shown in FIG. 4, the accelerator amount detecting unit 21
When the depression amount A of the accelerator pedal 9 is acquired at (S1), the calculation unit 22 derives a target current value It corresponding to the depression amount A of the accelerator pedal 9 (S1).
2), the target current value It is taken into the control unit 26. At this time, the detected acceleration G detected by the acceleration detecting unit 27, the first upper limit G1 and the second upper limit G2 set by the acceleration setting unit 30, and the output current detecting unit 34
Is detected by the control unit 26, and it is determined whether or not the detected acceleration G is greater than the first upper limit G1 (S3). If the determination result is NO, that is, G ≦ G1, If there is, the traveling chopper 13 is controlled by the control unit 26 so that the output current value I becomes the target current value It (S4), and thereafter, the process returns to the start and repeats the above-described steps.

On the other hand, if the decision result in the step S3 is YES,
That is, if G> G1, it is determined whether the target current value It is equal to or greater than the output current value I (S5). If the determination result is NO, that is, if It <I, the above-described step S4 is performed.
The traveling chopper 13 is controlled so that the output current value I becomes the target current value It (S4).

The result of the determination in step S5 is YE
If S, that is, If ≧ I, it is determined whether the detected acceleration G is equal to or greater than the second upper limit G2 (S6). If the result of this determination is YES, that is, if G ≧ G2, the acceleration G is too large. Therefore, the output current value I is reduced so as to lower the acceleration G below the second upper limit value G2 (S7). On the other hand, step S
If the decision result in 6 is NO, that is, G <G2, the output current value I is maintained as it is, and the process returns to the start and repeats the above steps.

According to such a control procedure, the acceleration of the forklift is controlled, for example, as shown in FIG. Here, the case where the accelerator pedal 9 is depressed to the maximum and the target current value It is set to the maximum output current value that generates the maximum output torque will be described.

As shown in FIG. 5, when the forklift is in a no-load state, the detected acceleration G reaches the first upper limit G1 until the accelerator pedal 9 is fully depressed, that is, from the start of the depression to time T1. Therefore, the output current value I is further increased until reaching the target current value It to increase the acceleration. After the time T1, the detected acceleration G exceeds the first upper limit value G1, but the output current value I is smaller than the target current value It, so that the output current value I is maintained in this state.

After the time T2, the detected acceleration G exceeds the second upper limit G2.
By the process of FIG. 7 (see FIG. 4), the output current value I is reduced until the detected acceleration G becomes smaller than the second upper limit G2.
Thereafter, after the time T3, the detected acceleration G becomes smaller than the second upper limit value G2, so that the output current value I is maintained as it is. Subsequently, after the time T4, the detected acceleration G becomes smaller than the first upper limit G1, and the output current value I becomes too low.
), The output current value I is increased to become the target current value It, and the acceleration is increased. Further, at time T5
, The detected acceleration G exceeds the first upper limit G1, and the output current value I is maintained as it is.

On the other hand, when the forklift is in the load state including the full load, the output current value I is increased to the target current value It when the accelerator pedal 9 is depressed. Even when the current value is reached, the detected acceleration G is smaller than the first upper limit value G1, so that the output current value I is maintained at the target current value It, that is, the output maximum current value.

Therefore, according to the above-described embodiment, the predetermined first upper limit value G1 and the second upper limit value G serving as the reference of the acceleration.
2, the detected acceleration G detected by the acceleration detection unit 27 is monitored, and the first upper limit G1 and the second upper limit G2 are monitored.
While controlling the output current value I output from the traveling chopper 13 to the traveling motor 3. That is, when the detected acceleration G is equal to or greater than the second upper limit G2, the output current value I is reduced and the acceleration of the vehicle body 1 is reduced, so that excessive acceleration of the forklift in a no-load state can be prevented. On the other hand, when the detected acceleration G is equal to or less than the first upper limit value G1, the traveling chopper 13 is controlled such that the output current value I becomes equal to the target current value It. Can be accelerated with good responsiveness.

Therefore, an appropriate acceleration can be obtained according to the load condition of the forklift such as at full load or no load, and the output of the motor drive unit is suppressed in order to suppress the acceleration at no load as in the related art. Without degrading acceleration at full load, as in the case of delaying the response time of current,
Good acceleration characteristics can be maintained even at full load.

In the above-described embodiment, a DC series motor is used as the traveling motor. However, the traveling motor is not limited to this. For example, a DC motor of a shunt type or separately excited type may be used. In other words, the present invention can be similarly applied to a forklift using a DC motor driven by passing a current from a battery through a motor drive unit, and the present invention can be applied in the same manner as in the above-described embodiment. The effect of can be obtained.

Further, in the above-described embodiment, the case where the present invention is applied to a counterbalance type forklift is described. However, in addition to the above-mentioned counterbalance type to which the present invention can be applied, a reach type forklift and other direct current forklifts can be used. It is needless to say that the present invention can be applied to a forklift that can use a motor as a power source. In this case, the same effect as that of the above-described embodiment can be obtained.

The present invention is not limited to the above embodiment, and various changes other than those described above can be made without departing from the gist of the present invention.

[0035]

As described above, according to the first aspect of the present invention, when the acceleration detected by the acceleration detecting section is equal to or more than the second upper limit value, the motor driving is performed by the control section so as to decrease the output current value. Since the parts are controlled, excessive acceleration of the forklift in a no-load state can be prevented, accidents due to sudden acceleration can be prevented beforehand, and unnecessary current can be eliminated to reduce power consumption. . On the other hand, when the detected acceleration becomes equal to or less than the first upper limit value, the motor drive unit is controlled so that the output current value becomes the target current value. And work efficiently.

As a result, an appropriate acceleration can be obtained according to the load condition of the forklift such as at full load or no load, and the motor drive unit is controlled to suppress the acceleration at no load as in the related art. Without deteriorating acceleration at full load, as in the case of delaying the response time of output current,
Good acceleration characteristics can be maintained even at full load, and a forklift with stable acceleration characteristics can be provided.

According to the second aspect of the present invention, the output current value is reduced so that the detected acceleration is smaller than the second upper limit value. Acceleration can be reliably prevented.

According to the third aspect of the present invention, the target current value is calculated by the calculation unit based on the accelerator amount detected by the accelerator amount detection unit. By setting the relationship of the values in advance, it becomes possible to derive a target current value proportional to, for example, the accelerator amount.

[Brief description of the drawings]

FIG. 1 is a side view of a forklift according to an embodiment of the present invention.

FIG. 2 is a connection diagram of a control device according to an embodiment of the present invention.

FIG. 3 is a block diagram of a control device according to the embodiment of the present invention.

FIG. 4 is a flowchart illustrating an operation according to the embodiment of the present invention.

FIG. 5 is a timing chart for explaining an operation according to the embodiment of the present invention;

FIG. 6 is a timing chart of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Body 2 Battery 3 Traveling motor 13 Traveling chopper (motor drive part) 21 Accelerator amount detection part 22 Operation part 23 Target current value derivation part (current value derivation part) 26 Control part 27 Acceleration detection part 34 Output current detection part

Claims (3)

[Claims] 1. A forklift control device that supplies power from a battery mounted on a vehicle body and drives a traveling motor by a motor drive unit, wherein the control unit detects an accelerator amount and derives a target current value corresponding to the accelerator amount. A current value deriving unit that detects an acceleration of the vehicle body; an output current detecting unit that detects an output current value supplied to the traveling motor from the motor driving unit; When the detected acceleration is equal to or less than a predetermined first upper limit, the motor drive unit is controlled so that the output current value becomes the target current value, and the detected acceleration is larger than the first upper limit and When the current value is larger than the target current value, the motor drive unit is controlled such that the output current value becomes the target current value,
A control unit that controls the motor drive unit so as to reduce the output current value when the detected acceleration is equal to or greater than a second upper limit value that is greater than the first upper limit value. apparatus. 2. The method according to claim 1, wherein the control section controls the output current to be smaller than the second upper limit when the output current is decreased when the detected acceleration is equal to or higher than the second upper limit. The control device for a forklift according to claim 1, wherein the value is reduced. 3. The current value deriving unit includes an accelerator amount detecting unit that detects the accelerator amount, and a calculating unit that calculates a target current value corresponding to the accelerator amount detected by the accelerator amount detecting unit. The control device for a forklift according to claim 1, wherein the control is performed.