JP2001139295A - Control device for fork lift truck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To go down a slope at a speed desired by an operator. SOLUTION: The output pulse of a rotation detecting part is counted by a counter, and the speed and acceleration of a fork lift truck are led out by a CPU 27 from the count value. The CPU 27 shifts to a neutral mode when detecting accelerator OFF by an accelerator detecting part, and sets the speed at the moment of shifting to the neutral mode, as the target speed. On the basis of the target speed and the led-out speed and acceleration, the CPU 27 computes the output command value of an induction motor by proportional plus derivative(PD) control to maintain the target speed when the speed of the fork lift truck becomes the target speed or higher. On the basis of the computed output command value, the CPU 27 controls a PWM pulse output part 28 to control the rotating speed of the induction motor and to perform regenerative control of the induction motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forklift for converting output DC power of a battery mounted on a body of a forklift into AC power by an inverter and feeding the AC power to a power induction motor, and driving the motor by a drive unit. The present invention relates to a control device for a forklift that performs power running and regeneration.

[0002]

2. Description of the Related Art Generally, a forklift driven by a battery travels by supplying power to a traveling DC motor 3 by a battery 2 mounted on a vehicle body 1 as shown in FIG. At this time, the transmission means (not shown) for transmitting the driving force of the 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 switching to a neutral state. The vehicle is switched to a neutral state when the vehicle travels forward or backward and when the vehicle is parked, and steering is performed by the steering wheel 5. In FIG. 8, reference numeral 6 denotes a mast provided on the front portion of the vehicle body 1, 7 denotes a lift bracket provided on the mast 6, 8 denotes a pair of forks provided on the lift bracket 7, and 9 denotes an accelerator pedal.

Recently, a forklift using an induction motor, which is an AC motor, as a power source instead of the DC motor 3 described above has been proposed. In the case of this induction motor type, for example, as shown in FIG. When the switch 11 is turned on, the output DC power of the battery 2 is smoothed by the smoothing capacitor 12 and converted into AC power by the three-phase bridge inverter 13 formed by connecting six field effect transistors T1 to T6 in full bridge. Power is supplied to the three-phase induction motor 14, and power running control and regeneration control are performed by utilizing the characteristic of regenerative braking of the induction motor 14.

As described above, in the forklift using the induction motor 14 as a power source, when the vehicle moves from a flat road to a slope, the operator stops depressing the accelerator pedal during the travel immediately before entering the slope. As a control in the case of shifting to a so-called neutral mode, a method of performing regenerative control to limit a speed during a descending slope to a predetermined speed or less can be considered.

[0005]

When regenerative control is not performed, the speed gradually increases due to the gravity of the forklift as it goes down the hill, so that the load may collapse during the descent or the operator may predict during braking. There is a problem that an extra braking distance is required.

When the downhill speed is limited to a predetermined speed or less, when the forklift starts to go downhill even though the worker has adjusted to the desired running speed immediately before approaching the slope, the forklift lifts the desired speed. Since the vehicle descends at a predetermined speed different from the speed, the vehicle cannot descend at a speed desired by the operator, which may cause a problem that the operator feels inconvenience.

An object of the present invention is to enable a worker to go down a slope at a desired speed.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention converts an output DC power of a battery mounted on a body of a forklift into an AC power by an inverter to produce an induction motor for power. In a forklift control device that supplies power and drives the motor by the driving unit to perform power running and regeneration, when the accelerator is turned off during traveling to shift to the neutral mode, the speed at the time of shifting to the neutral mode is set as a target speed. When the speed is equal to or higher than the target speed, an output command value of the motor by proportional differential control is calculated based on the target speed and the speed and acceleration of the forklift to maintain the target speed.

According to such a configuration, when the accelerator is turned off during traveling and the vehicle shifts to the neutral mode, the output command value of the motor is calculated based on the target speed at the time of the neutral mode transition and the speed and acceleration of the forklift. By controlling the motor in accordance with the calculated output command value, the speed of the forklift thereafter is maintained at or below the target speed.

[0010] Therefore, for example, when the forklift tries to run on a hill with the speed at which the forklift enters the hill from a flat road, if the accelerator is turned off immediately before the hill is entered, the speed at that time is set as a target speed. The vehicle will travel on a slope with the speed kept below the target speed, and if the operator adjusts the speed of the forklift to a desired speed immediately before entering the slope, the operator can travel down the slope at that speed. Can be.

The present invention also provides a rotation detector for detecting the number of rotations of the motor, a derivation unit for deriving the speed and acceleration of the forklift from a value detected by the rotation detector.
An accelerator detecting unit for detecting ON or OFF of an accelerator; and a shift to a neutral mode by detecting the OFF of the accelerator by the accelerator detecting unit. When the speed at the time of the neutral mode shift exceeds a target speed as a target speed. A control unit that calculates an output command value of the motor by proportional differential control based on the target speed and the speed and acceleration of the forklift by the deriving unit to maintain the target speed. I have.

According to this configuration, when the accelerator detecting section detects that the accelerator is OFF and shifts to the neutral mode, the motor output command is set based on the target speed at the time of shifting to the neutral mode and the speed and acceleration of the forklift by the deriving section. Since the value is calculated, the speed of the forklift can be maintained at or below the target speed at the time of shifting to the neutral mode by controlling the motor in accordance with the calculated output command value.

Further, the present invention is characterized in that the control unit calculates the output command value in the forward direction and the output command value in the reverse direction in accordance with the direction of the speed by the deriving unit. I have.

According to such a configuration, it is possible to calculate the motor output command value in consideration of the rotation direction of the motor, depending on whether the vehicle body is traveling forward or backward.

[0015]

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 block diagram of a control device according to an embodiment of the present invention, and FIGS. 2 to 7 are flowcharts for explaining the operation of FIG.

Here, the configuration of the counterbalance type forklift is the same as that shown in FIG. 8 except that the DC motor 3 is an induction motor, so that FIG. 8 is also referred to in the following description. In the present embodiment, a three-phase induction motor is used similarly to the induction motor 14 shown in FIG. 9, and the inverter used for driving the same has the same configuration as the three-phase bridge inverter 13 shown in FIG. In the description, reference is also made to FIG.

As shown in FIG. 1, an accelerator pedal detector (not shown) proportional to the amount of depression of an accelerator pedal 9
Is converted into a digital signal by an analog / digital (A / D) conversion unit 21,
Thus, ON and OFF of the accelerator and the amount of depression thereof are detected. Also, as shown in FIG.
The rotation shaft 4 is provided with a rotation detection unit 15 composed of a rotary encoder. The output pulse from the rotation detection unit 15 is counted by a counter 22, and from the count value, the CPU of the induction motor 14 The rotation speed is detected.

Further, the switching state of the directional lever 4 as a switching unit for setting the transmission means (not shown) for transmitting the driving force of the induction motor 14 to the wheels to either forward or backward or to a neutral state is parallel. Input unit (PI)
The signal is input to a CPU, which will be described later, via 23, and the CPU determines whether the directional lever 4 is set to the forward direction, the backward direction, or the neutral state.

Data such as the amount of depression of the accelerator pedal 9, the number of rotations of the motor and the switching state of the directional lever 4 are temporarily stored in the RAM 25, and according to a predetermined control program stored in the ROM 26 in advance. Pulse width modulation (PW
M: Pulse Width Modulation) From the pulse output unit 28,
A PWM control pulse is output to the control terminals of the transistors T1 to T6 of the inverter 13, the output current of the induction motor 14 is controlled, and power running control or regenerative control is performed.

By the way, the CPU 27 controls the rotation detecting unit 15.
The speed and acceleration of the forklift are derived from the motor speed detected by Further, when the accelerator detecting unit detects that the accelerator is OFF, the CPU 27 shifts to the neutral mode, and sets the speed at the time of shifting to the neutral mode as a target speed, based on the target speed and the derived speed and acceleration. In order to maintain the target speed when the speed of the forklift becomes equal to or higher than the target speed, an output command value of the induction motor 14 is calculated by proportional differential (PD) control.

Then, based on the calculated output command value, the PWM pulse output unit 28 is controlled and the induction motor 1 is controlled.
4 is controlled, and the regeneration control of the induction motor 14 is performed.

At this time, the CPU 27 simultaneously derives the positive and negative directions of the speed depending on whether the traveling direction of the vehicle body 1 is forward or backward, and according to the direction of the speed, the positive and negative directions of the induction motor 14 are determined. The output command value of the induction motor 14 in the reversing direction (when moving forward) or in the reversing direction (when moving backward) is calculated. The process of deriving the speed and acceleration by the CPU 27 corresponds to a deriving unit, and the CPU 27
Corresponds to the control unit.

The CPU 27 calculates the output command value by setting the target speed at the time of transition to the neutral mode to Vt, the input speed and the acceleration derived from the output of the rotation detector 15 by the CPU 27 to V and G, respectively. Assuming that the gains (coefficients) are k1 and k2 and the output command value Mf of the induction motor 14 when the traveling direction is forward and the output command value Mb of the induction motor 14 when the traveling direction is backward, Mf = k1 × (V−Vt) + K2 × G (for forward movement) Mb = −k1 × (V−Vt) −k2 × G (for backward movement) Here, the first term on the right side of each of the above equations represents a proportional (P) control component in proportional differential (PD) control, and the second term on the right side represents a differential (D) control component.

Next, the operation will be described with reference to the flowcharts of FIGS.

First, the main routine will be described. As shown in FIG.
Initialization of the device is performed, starting with CP25.
A mode flag composed of a built-in register or the like in U27 is set to "neutral" (S1), a signal proportional to the amount of depression of the accelerator pedal 9 is taken from the accelerator detection unit (S2), and the directional lever 4 is set via PI23. (S3), the count value of the counter 22 is fetched (S4), and it is determined whether or not the mode flag is "forward" (S3).
5).

If the result of this determination is YES,
The forward control process described later is performed (S6), and the determination result is N
If O, it is determined whether or not the mode flag is "reverse" (S7). If the determination result is YES, a reverse control process described later is performed (S8), and the determination result is NO.
If it is, it is determined whether or not the mode flag is "regeneration at the time of forward descent" (S9), and the result of this determination is YE
If S, control processing for forward deceleration regenerative braking control described later is performed (S10). If the determination result is NO, whether or not the mode flag is "retreating backward descent deceleration regeneration" is determined. Is determined (S11), and if the result of this determination is YES, a control process of slowing down regenerative operation during retreat, which will be described later, is performed (S1).
2) If the determination result is NO, the process shifts to the neutral mode process (S13), and thereafter, the above-described step S6,
After the processing of S8, S10 and S12, step S
Return to 2.

Next, the neutral mode processing in step S13 in FIG. 2 will be described with reference to FIG.
Now, when shifting to the neutral mode, the speed of the forklift derived from the count value of the counter 22 fetched in step S4 of FIG. 2 is set as the target speed Vt, and as shown in FIG. Is set as the input speed V (S21), and step S3 in FIG.
It is determined whether or not the accelerator is ON based on the signal from the accelerator pedal detection unit captured in (2) (S2).
2).

If the result of this determination is YES, a determination is made as to whether the switching state of the directional lever 4 is forward, backward or neutral (S23). If it is determined that the directional lever 4 is forward, the mode flag is set to "forward". Is set to ("S
24) If it is determined that the vehicle is retreating, the mode flag is set to "reverse" (S25). If it is determined that the vehicle is neutral, the process proceeds to step S26 together with when the determination result of step S22 is NO. It is determined whether or not the input speed V is positive (S26).

If the result of the determination in step S26 is YES, it can be determined that the vehicle was in the forward traveling state when shifting to the neutral mode, so that the mode flag is set to "forward slowdown regeneration during downhill" (S27). If the determination result is NO, it is determined whether or not the input speed V is negative (S28). If the determination result is YES, it can be determined that the vehicle is in the retreating state at the time of shifting to the neutral mode. It is set to "reverse slowdown regeneration during descending slope" (S29).

On the other hand, if the decision result in the step S28 is NO, the steps S24, S25, S27, S
After the process of step 29, the process shifts to step S30, where the output of the induction motor 14 is controlled to be off (S31).
Thereafter, the process returns to the main routine of FIG.

Now, the forward control process in step S6 in FIG. 2 will be described with reference to FIG. 4. As shown in FIG. 4, by multiplying a predetermined gain (positive coefficient) and the amount of depression of the accelerator pedal, A motor output command value in forward running is calculated, and the output of the induction motor 14 is controlled according to the output command value (S41), and it is determined whether or not the accelerator is ON based on a signal from the accelerator detection unit (S42). If the result of this determination is YES, it is determined whether the switching state of the directional lever 4 is forward, backward or neutral (S43).

If the result of the determination in step S42 is NO, or if the result of determination in step S43 is retreat or neutral, the process proceeds to step S44, and the mode flag is set to "neutral" (S44). Then, the process returns to the main routine in FIG. 2 described above together with the result of the determination in step S43 indicating that the vehicle is moving forward.

The reverse control process in step S8 in FIG. 2 will be described with reference to FIG. 5. As shown in FIG. 5, a predetermined gain (negative coefficient) is multiplied by the depression amount of the accelerator pedal. A motor output command value in the reverse traveling is calculated, and the output of the induction motor 14 is controlled according to the output command value (S51), and it is determined whether or not the accelerator is on based on a signal from the accelerator detection unit (S52). If the result of this determination is YES,
It is determined whether the switching state of the directional lever 4 is forward, neutral, or backward (S53).

When the result of the determination in step S52 is NO or when the result of the determination in step S53 is forward or neutral, the process proceeds to step S54, and the mode flag is set to "neutral" (S54). Then, the process returns to the main routine in FIG. 2 described above together with when the result of the determination in step S53 is retreat.

Next, a description will be given, with reference to FIG. 6, of the control processing of the forward regenerative downhill regenerative braking control in step S10 in FIG. 2. First, as shown in FIG. It is determined whether it is larger (S6).
1) If the result of this determination is YES, the target speed V
t is set as the input speed V (S62), and after that, the determination result of step 61 is NO and step S63 is performed.
Then, the output command value Mf of the induction motor 14 when the vehicle is moving forward with respect to the target speed Vt is calculated, and the output of the induction motor 14 is controlled according to the output command value Mf (S63). When the output command value Mf <0, the output command value Mf is set to zero.

Then, based on a signal from the accelerator detecting section, it is determined whether or not the accelerator is ON (S64). If the determination result is YES, whether the switching state of the directional lever 4 is forward, backward or neutral is determined. Is determined (S65), when this determination result is neutral, the process proceeds to step S66 together with the determination result of step S64 described above being NO, and determines whether the input speed V set in step S62 is equal to or less than zero. Is determined (S6).
6).

If the result of this determination is YES, the process proceeds to step S67 together with the determination that the vehicle is moving forward or backward in step S65, and the mode flag is set to "neutral" (S67).
The process returns to the main routine of FIG. 2 described above together with the case where the determination result of step S66 is NO.

Further, a control process of the slow regenerative braking control in step S12 in FIG. In this case, since the speed is in the positive direction during forward movement, the speed is negative when moving backward.

As shown in FIG. 7, it is first determined whether the target speed Vt is lower than the input speed V (S7).
1) If the result of this determination is YES, the target speed V
t is set as the input speed V (S72), and thereafter, the case where the determination result of step 71 is NO and step S73.
Then, the output command value Mb of the induction motor 14 in the case of retreating from the target speed Vt is calculated, and the output of the induction motor 14 is controlled according to the output command value Mb (S73). When the output command value Mb> 0, the output command value Mb is set to zero.

Then, it is determined whether or not the accelerator is ON based on a signal from the accelerator detection unit (S74). If the determination result is YES, whether the switching state of the directional lever 4 is forward, backward, or neutral is determined. Is determined (S75), when the result of the determination is neutral, the process proceeds to step S76 with the result of the determination in step S71 being NO, and whether the input speed V set in step S72 is equal to or greater than zero or not. Is determined (S7).
6).

If the result of this determination is YES, the process proceeds to step S77 together with the determination that the vehicle is moving forward or backward in step S75, and the mode flag is set to "neutral" (S77).
The process returns to the main routine of FIG. 2 described above together with the case where the determination result of step S76 is NO.

As described above, when the accelerator is turned off during traveling and the vehicle shifts to the neutral mode, the output command value of the induction motor 14 is calculated based on the target speed Vt and the forklift speed V and the acceleration G at the time of the neutral mode. The induction motor 14 is controlled in accordance with the calculated output command value. For example, when the forklift attempts to run on a hill at a speed at which the forklift enters the hill from a flat road, the accelerator is turned off immediately before the hill enters. For example, the speed at the time of entering the slope is set as the target speed Vt, and the vehicle travels on the slope without acceleration while being maintained at the target speed Vt or less.

Therefore, according to the above-described embodiment, the operator adjusts the depression amount of the accelerator pedal 9 just before entering the hill, and adjusts the speed of the forklift to a desired speed, whereby the speed is adjusted. It is possible to run down the hill on the road.

In the above embodiment, the case where the induction motor 14 is a three-phase induction motor is described. However, the present invention is not particularly limited to the three-phase induction motor, but may be a two-phase or four-phase induction motor. Of course, it may be.

Further, in the above-described embodiment, the case where the present invention is provided to the counterbalance type forklift has been described. Needless to say, the present invention can be applied to a forklift that can use a motor as a power source, and in this case, the same effect as in the above-described embodiment can be obtained.

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

[0047]

As described above, according to the first aspect of the present invention, if the accelerator is turned off, the speed at that time is set as the target speed, and then the forklift travels while being maintained at the target speed or lower. For example, when a worker enters a hill, by adjusting the speed of the forklift to a desired speed immediately before entering the hill, it is possible to travel down the hill at that speed, and the speed of the forklift is reduced. It is possible to go down the slope at an optimum speed for the worker without accelerating and becoming faster than expected by the worker.

According to the second aspect of the present invention, when the accelerator detecting section detects the accelerator OFF and shifts to the neutral mode, based on the target speed at the time of shifting to the neutral mode and the speed and acceleration of the forklift by the deriving section. Since the output command value of the motor is calculated, by controlling the motor in accordance with the calculated output command value, the speed of the forklift can be maintained below the target speed at the time of shifting to the neutral mode.

According to the third aspect of the present invention, whether the vehicle body is traveling forward or backward is determined by
It is possible to calculate the motor output command value in consideration of the rotation direction of the motor.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the embodiment of the present invention;

FIG. 3 is a flowchart for explaining the operation of the embodiment of the present invention;

FIG. 4 is a flowchart for explaining the operation of the embodiment of the present invention;

FIG. 5 is a flowchart for explaining the operation of the embodiment of the present invention;

FIG. 6 is a flowchart for explaining the operation of the embodiment of the present invention;

FIG. 7 is a flowchart for explaining the operation of the embodiment of the present invention;

FIG. 8 is a side view of a general DC motor type forklift.

FIG. 9 is a connection diagram of a control circuit of a general three-phase induction motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Body 2 Battery 4 Directional lever (switching part) 9 Accelerator pedal 13 Three-phase bridge inverter 14 Three-phase induction motor 15 Rotation detecting part 27 CPU (lead-out part, control part)

Claims (3)

[Claims] An output DC power of a battery mounted on a body of a forklift is converted into AC power by an inverter and supplied to a power induction motor, and a driving unit drives the motor to perform power running and regeneration. In the control device of the forklift, when the accelerator is turned off during traveling to shift to the neutral mode, and when the speed at the time of shifting to the neutral mode becomes a target speed and becomes higher than the target speed, the target speed is maintained. A control device for a forklift, wherein an output command value of the motor is calculated by proportional differential control based on the target speed and the speed and acceleration of the forklift. 2. A rotation detecting unit for detecting the number of rotations of the motor, a deriving unit for deriving the speed and acceleration of the forklift from a value detected by the rotation detecting unit, and an accelerator detecting unit for detecting ON or OFF of an accelerator. When the accelerator detection unit detects that the accelerator pedal has been turned off, the mode shifts to the neutral mode. When the speed at the time of the neutral mode shift exceeds the target speed as the target speed, the target speed is maintained to maintain the target speed. The control device for a forklift according to claim 1, further comprising: a control unit that calculates an output command value of the motor by proportional differential control based on a speed and a speed and an acceleration of the forklift by the derivation unit. 3. The control unit calculates the output command value in the forward direction and the output command value in the reverse direction according to the direction of the speed by the deriving unit. 4. The control device for a forklift according to claim 1.