JP2003012290A - Electric power steering device in cargo handling vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a power steering motor and its controller from overheating and burning. SOLUTION: It is judged whether a deadman brake is operated or not based on ON or OFF condition of a limit switch (S1). If the result of judgement is YES, it is judged whether a count value of a timer counter reaches 3s which is set time or not (S4). If the result of judgement is YES, output control of the power steering motor by a motor driver is stopped (S6).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus for a cargo handling vehicle having no mechanical connecting structure between a steering handle and a steering mechanism.

[0002]

2. Description of the Related Art Conventionally, there is an electric power steering apparatus for a cargo handling vehicle such as a forklift truck which does not have a mechanical connection structure between a steering handle and a steering mechanism. The device is configured, for example, as shown in FIG.

That is, as shown in FIG. 4, the rotation angle of a steering wheel provided on a vehicle body such as a forklift is detected by an operation angle sensor 1 including a potentiometer, and the actual steering angle of a steering mechanism is detected. The target steering angle calculation unit 3 calculates the target steering angle from the rotational operation angle detected by the actual steering angle sensor 2 including a potentiometer and detected by the operation angle sensor 1. At this time, since the rotational operation angle of the steering wheel and the target steering angle are in a proportional relationship, the target steering angle can be derived by multiplying the detected rotational operation angle by a constant.

Then, the difference between the target steering angle and the steering angle detected by the actual steering angle sensor 2 is calculated by the addition / subtraction unit 4, and the difference is multiplied by a predetermined proportional coefficient by the proportional element calculation unit 5, The output of the proportional element calculation unit 5 is given to a motor driver 6 composed of a chopper circuit or an inverter circuit, and the motor driver 6 controls the output of the power steering motor 7. In this way, the steering angle by the actual steering angle sensor 2 is controlled so as to match the target steering angle.

However, since there are frictions and reaction forces between the actual road surface and the tires of the cargo handling vehicle, the power is based on the value obtained by multiplying the difference between the target steering angle and the steering angle by a proportional coefficient. When the steering motor 7 is controlled,
The actual steering angle of the steering mechanism cannot be perfectly matched with the target steering angle, and a steady deviation occurs between the actual steering angle and the target steering angle.

If such a steady deviation continuously occurs, a residual current corresponding to the steady deviation continues to flow to the motor 7 even when the steering wheel is not operated, so that the motor 7 is burned or the motor driver is not driven. This causes overheating and burnout of the controller including No. 6.

Therefore, normally, as shown in FIG. 4, the integral element calculating unit 8 calculates the time integral value of the difference between the target steering angle and the steering angle.
Is added to the calculation result of the proportional element calculation section 5 by the addition section 9 to add the integration result (integration element) of the integration element calculation section 8 to eliminate the above-mentioned steady-state deviation. 6, the power steering motor 7 is controlled to eliminate the above-mentioned problem caused by the residual current.

[0008]

However, the friction and reaction force generated between the actual road surface and the tires of the cargo handling vehicle differ depending on the type of tire and the condition of the road surface.
Since these frictions and reaction forces are greatly different between when loaded and when not loaded, it is generally difficult to find the optimum value of the integral element in consideration of all the states of such a cargo handling vehicle. Therefore, it is impossible to completely eliminate the above-mentioned steady deviation.

Further, even in vehicles other than forklifts, if the tire falls into the groove and the tire is locked and falls into the unsteerable state, the current continues to flow to the motor 7, and therefore, like the above-mentioned residual current, The controller including the motor 7 and the motor driver 6 may be overheated or burned.

Therefore, it is an object of the present invention to protect a power steering motor and its controller from overheating and burnout.

[0011]

In order to achieve the above-mentioned object, the present invention detects the rotation of a steering wheel, and the control means controls a motor for power steering based on the detected value to control a steering mechanism. In a cargo handling vehicle that steers a vehicle, a brake detection unit that detects an operation of a brake provided in the cargo handling vehicle is provided, and the control unit controls the power steering motor when the brake operation is detected by the brake detection unit. It is characterized by stopping.

According to this structure, when the brake operation is detected by the brake detecting means, it is not necessary to drive the power steering motor to perform power assist while the brake is operating. The control of the power steering motor is stopped by the means. Therefore, by stopping the control of the power steering motor while the brakes are operating, it is possible to prevent the motor and its controller from overheating and burning due to the continuous flow of current to the motor during that period. it can.

Further, according to the present invention, a timer counter for counting a preset time from the brake operation detection by the brake detection means is provided, and when the control means finishes counting the set time by the timer counter. The control of the power steering motor is stopped.

According to such a configuration, depending on whether or not the counting of the set time by the timer counter is completed,
Whether or not the vehicle body has stopped can be reliably determined, and when it can be determined that the vehicle body has stopped, the control of the power steering motor by the control means is stopped. By shutting off the current of 1, it is possible to more reliably prevent the motor and its controller from being overheated and burnt out.

Further, the present invention is characterized in that the brake is a deadman brake which is activated when the driver is not driving. With such a configuration, when the deadman type brake is operated, the control of the power steering motor by the control means is stopped, so that the current to the power steering motor is shut off when the deadman brake is stopped. As a result, overheating and burnout of the motor and its controller can be prevented more reliably.

Further, the present invention is characterized in that the cargo handling vehicle is a forklift equipped with a brake that operates when the steering wheel is erected substantially vertically and tilted substantially horizontally.

According to this structure, when the deadman brake is operated with the steering wheel standing upright vertically and tilted substantially horizontally, the current to the power steering motor when the deadman brake is stopped is stopped. It is possible to more reliably prevent the motor and its controller from being overheated and burnt out. As a forklift equipped with a brake that operates in a state in which the handle is erected in a substantially vertical position and a state in which the handle is tilted in a substantially horizontal state, for example, a low lift truck in which a person walks to a car and operates the handle, or a step attached to a vehicle body There is a low-lift truck that operates the steering wheel by getting on.

Further, the present invention is characterized in that the cargo handling vehicle is a reach type forklift, and the brake operates in a state in which the depression of the brake pedal is released.

According to this structure, when the deadman type brake is activated by releasing the depression of the brake pedal of the reach type forklift, the current to the power steering motor is cut off when the deadman brake is stopped. It is possible to more reliably prevent overheating and burnout of the motor and its controller.

According to the present invention, the cargo handling vehicle is a counterbalance type forklift, and the brake is
It is characterized in that it is a foot brake or a side brake that operates when the brake pedal is depressed.

According to this structure, when the brake pedal of the counterbalanced forklift is depressed to operate the foot brake or the side brake, the current to the power steering motor at the time of stopping due to the operation of these brakes Is cut off,
It is possible to more reliably prevent overheating and burning of the motor and its controller.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention applied to a low lift truck which is a cargo handling vehicle.
Or, it demonstrates with reference to FIG. However, FIG. 1 is a side view of a low lift truck according to an embodiment of the present invention, FIG. 2 is a block diagram of a control system of a walkie forklift,
FIG. 3 is a flowchart for explaining the operation.

As shown in FIG. 1, the low lift truck 11 according to this embodiment includes a vehicle body 12 and a vehicle body 1.
A pair of forks 13 arranged at the front of the vehicle 2 and movable in the vertical direction, a steering handle 14 arranged on the upper surface of the vehicle body 12 for steering the low lift truck 11, and arranged at the rear of the vehicle body 12. Step section 1 where the driver can ride
5 and 5.

The steering handlebar 14 is composed of a handlebar shaft 18 which is tiltably disposed on the upper surface of the rear portion of the vehicle body 12, and an operating portion 19 which is provided at the tip of the handlebar shaft 18. Further, the handle 14 is biased by a spring (not shown) so as to stand substantially vertically. For example, when the handle 14 is not operated,
It is held in a vertical standing position.

Further, an accelerator lever (not shown) is provided in the operating portion 19 of the handle 14, and when the accelerator lever is tilted back and forth from the neutral position, the tilt direction and tilt angle from the neutral position are changed. A traveling motor (not shown) is driven at a corresponding direction and speed to move the low lift truck 11 forward or backward. In addition, the operation unit 19
An elevating button (not shown) for driving the fork 13 in the up-down direction is provided in the.

By the way, at the base end of the handle shaft 18,
A limit switch (not shown) is provided as a brake detection means, and a tilt angle of the handlebar 14 is detected by a combination of the limit switch and a cam (not shown), and a deadman brake (illustrated by an electromagnetic brake is shown. The operation of (omitted) is detected. That is, in this example, the brake detecting means for detecting the operation of the brake described in the claims is composed of the combination of the limit switch and the cam, and detects the operation of the brake by detecting the operation of the handle 14. is there. In other words, the brake actuation is indirectly detected by detecting the operation of the steering wheel 14. As described above, the term "brake actuation detection" as used in the claims means that the actuation of the brake may be directly detected, or the actuation of the brake may be indirectly detected. As such, various sensors and technologies can be utilized.

Then, as shown in FIG. 1, while the low lift truck 11 is traveling, the handlebar 14 is tilted within the stop ranges α and β in which the handlebar 14 is erected substantially vertically or tilted substantially horizontally. And the limit switch is off
Then, the deadman brake is activated, and the vehicle body 12 is forcibly stopped.

On the other hand, when the handlebar 14 is tilted within the travelable range γ between the two stop ranges α and β, the limit switch is ON, so the deadman brake does not operate, The vehicle body 12 is ready to run. Since the handlebar 14 is biased by the spring in the direction in which the handlebar 14 stands up from the horizontal state as described above, the handlebar 14 automatically stands up when the hand is suddenly released from the handlebar 14 while traveling, for example. The deadman brake operates in a state where the deadman brake is activated, that is, in a standing state within the stop range α.

By the way, the step portion 15 is provided in the vehicle body 1.
2 is tiltably arranged around a shaft member horizontally arranged (in a direction perpendicular to the paper surface of FIG. 1) along the rear portion, and torsion springs are wound around both ends of the shaft member. One end thereof is locked to the rear portion of the vehicle body 12 and the other end thereof is locked to the step portion 15, and the step portion 15 is biased by the torsion spring in a substantially vertical standing direction. Therefore, while the step portion 15 is not loaded, the step portion 15 is held upright in the rear portion of the vehicle body 12, while when driving the low lift truck 11, the driver is The handle 15 is tilted to the horizontal state, the step portion 15 is mounted, and the handle 14 is operated.

Next, the low lift truck 11 described above
The control system of the electric power steering device of No. 1 will be described as follows.

That is, as shown in FIG. 2, an operation angle sensor 21 is provided as an operation angle detecting means for detecting the rotational operation angle of the handle 14 of the low lift truck 11, and the actual steering angle of the steering mechanism is detected. An actual steering angle sensor 22 as an actual steering angle detecting means is provided,
Both of these sensors 21 and 22 are composed of, for example, potentiometers.

Then, the target steering angle calculation unit 23 calculates the target steering angle from the rotational operation angle detected by the operation angle sensor 21. Here, since the rotation operation angle of the steering wheel 14 and the target steering angle are in a proportional relationship, the target steering angle can be derived by multiplying the rotation operation angle detected by the operation angle sensor 21 by a constant. it can.

Further, the difference between the target steering angle and the steering angle detected by the actual steering angle sensor 22 is the addition / subtraction unit 25.
The proportional element calculation unit 26 multiplies the difference by a predetermined proportional coefficient, the time integration value of the difference between the target steering angle and the steering angle is calculated by the integration element calculation unit 27, and the addition unit 28 calculates The integration result (integral element) by the integral element operation unit 27 is added to the operation result of the proportional element operation unit 26.

Then, the output of the adding section 28 is given to a motor driver 30 composed of a chopper circuit or an inverter circuit, and the output of the power steering motor 31 is controlled by the motor driver 30. Thus, the steering angle by the actual steering angle sensor 22 is changed. It is controlled so as to match the target steering angle.

On the other hand, as described above, when the limit switch 33 as a brake detecting means arranged at the base end of the handle shaft 18 of the handle 14 is turned off and the operation of the deadman brake is detected, the timer counter 34 operates. Counting starts and a preset time (for example,
3s) is counted, and when the count of the timer counter 34 is finished, the output control of the power steering motor 31 by the motor driver 30 is stopped. The process of stopping the output control of the power steering motor 31 by the motor driver 30 corresponds to the control means in the present invention. The timer counter 3
4 is cleared by deactivating the deadman brake.

Next, the operation will be described with reference to the flowchart of FIG. As shown in FIG. 3, it is determined from the ON / OFF state of the limit switch 33 whether or not the deadman brake is activated (S1). If the result of this determination is NO, the deadman brake is not activated. The timer counter 34 is cleared (S2), and the motor driver 30 causes the power steering motor 31
Output control is performed and the power steering motor 31
Is driven (S3), and then the process returns to step S1.

On the other hand, if the decision result in the above-mentioned step S1 is YES, it is decided whether or not the count value of the timer counter 34 reaches the set time 3s (S).
4) If the result of this determination is NO, the timer counter 3
The count of 4 is continued (S5), and then the process proceeds to step S3 described above.

If the decision result in the above-mentioned step S4 is YES, it can be judged that the timer counter 34 has finished (counting up) the set time of 3 s. Therefore, the routine proceeds to the next step S6, and The output control of the power steering motor 31 by the driver 30 is stopped (S6), and then the process returns to step S1.

In this way, the limit switch 33 is turned off.
When the timer counter 34 starts counting after F and finishes counting the set time, it can be determined that the deadman brake has actuated and the vehicle body 12 has definitely stopped, and while the deadman brake is actuated. Since it is not necessary to drive the power steering motor 31 to assist the power steering, the motor driver 30 stops the output control of the power steering motor 31 at the time when the vehicle body 12 surely stops.

At this time, the addition unit 28 adds the integration result (integration element) by the integral element calculation unit 27 to the calculation result of the proportional element calculation unit 26, so that a steady state between the actual steering angle and the target steering angle is obtained. Deviation can be made small to some extent but cannot be made completely zero,
The residual current based on this deviation flows to the power steering motor 31. However, while the deadman brake is operating, by stopping the output control of the power steering motor 31 by the motor driver 30 as described above, the residual current based on this deviation is kept flowing to the power steering motor 31. It can be prevented.

Therefore, according to the above embodiment, the deadman brake is stopped by stopping the output control of the power steering motor 31 by the motor driver 30 while the deadman brake is operating and the vehicle body 12 is stopped. It is possible to prevent overheating and burnout of the power steering motor 31 and the like due to continuous current (residual current) flowing to the power steering motor 31 during operation.

In the above embodiment, the output control of the power steering motor 31 by the motor driver 30 is stopped when the timer counter 34 counts up the set time (here, 3 seconds). This set time is not particularly limited to the above 3 seconds. Further, without providing such a timer counter 34,
The output control of the power steering motor 31 by the motor driver 30 may be stopped when the limit switch 33 is turned off.

Further, in the above embodiment, the case where the low lift truck 11 is provided with the step portion 15 has been described, but the present invention is also applied to the low lift truck 11 which is not provided with such a step portion 15. It is possible to obtain the same effect as that of the above-described embodiment.

Further, in the above embodiment, the case where the brake detecting means is the limit switch 33 has been described, but it goes without saying that the brake detecting means is not limited to the limit switch.

Further, in the above-described embodiment, an example of the proportional + integral control by the proportional element calculation unit 26 and the integral element calculation unit 27 is shown, but the present invention is not limited to this, and the control and the integral element by the proportional element calculation unit 26 only. The control may be performed only by the arithmetic unit 27, or may be proportional + integral + derivative control in which a differential element is also taken into consideration or other control.

Furthermore, in the above-described embodiment, the case where the present invention is applied to the low lift truck 11 has been described, but the applicable range of the present invention is not limited to this, and a reach type and other forklifts are begun. It can be applied to all cargo handling vehicles. In particular, when applied to a counterbalanced forklift, the control of the power steering motor should be stopped when the driver operates the foot brake or the side brake by depressing the brake pedal as a brake. desirable.

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

[0048]

As described above, according to the first aspect of the present invention, when the brake detecting means detects the operation of the brake, the power steering motor is driven while the brake is operating. Since there is no need for power assist, the control of the power steering motor is stopped by the control means, so while the brake is operating,
By stopping the control of the power steering motor, it is possible to prevent the motor and its controller from overheating and burning due to the continuous flow of current to the motor during that time.

According to the second aspect of the present invention, whether the vehicle body is stopped can be reliably determined based on whether the timer counter has finished counting the set time, and the vehicle body is stopped. If it can be determined that the power steering motor has been stopped by the control means, the current to the power steering motor is cut off when the motor is stopped to more reliably prevent overheating and burnout of the motor and its controller. It becomes possible to prevent.

Further, according to the third aspect of the invention, when the deadman type brake is operated, the control of the power steering motor by the control means is stopped, so that the power steering motor is stopped when the deadman brake is stopped. By shutting off the current to the motor, it becomes possible to more reliably prevent overheating and burning of the motor and its controller.

According to the invention described in claim 4, when the deadman type brake is actuated with the handle of the low lift truck standing upright substantially vertically and tilted substantially horizontally, the deadman brake is actuated. It is possible to more reliably prevent overheating and burnout of the motor and its controller by shutting off the current to the power steering motor when the motor is stopped.

Further, according to the invention described in claim 5, when the deadman type brake is operated by releasing the depression of the brake pedal of the reach type forklift, the current to the power steering motor at the time of stop due to the operation of the deadman brake. Is cut off, it is possible to more reliably prevent overheating and burnout of the motor and its controller.

According to the sixth aspect of the present invention, when the foot pedal or the side brake is operated by depressing the brake pedal of the counterbalance type forklift, the power steering is stopped by the operation of these brakes. Since the current to the motor is cut off, it is possible to more reliably prevent the motor and its controller from being overheated and burnt out.

[Brief description of drawings]

FIG. 1 is a side view of a low lift truck according to an embodiment of the present invention.

FIG. 2 is a block diagram of a control system in an embodiment of the present invention.

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

FIG. 4 is a block diagram of a conventional example.

[Explanation of symbols]

21 Operation angle sensor (operation angle detection means) 22 Actual steering angle sensor (actual steering angle detecting means) 30 Motor driver (control means) 31 Power steering motor 33 Limit switch (brake detection means) 34 timer counter

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) // B62D 109: 00 B62D 109: 00 113: 00 113: 00

Claims (6)

[Claims] 1. A cargo handling vehicle in which rotation of a steering wheel is detected, and a control means controls a power steering motor based on the detected value to steer a steering mechanism, wherein a brake provided in the cargo handling vehicle is actuated. An electric power steering apparatus for a cargo handling vehicle, comprising: a brake detection unit that detects the operation of the power steering motor, wherein the control unit stops the control of the power steering motor when the brake operation is detected by the brake detection unit. 2. A power counter comprising: a timer counter that counts a preset time set by the brake operation detection by the brake detection unit; and when the control unit finishes counting the set time by the timer counter. The electric power steering device for a cargo handling vehicle according to claim 1, wherein control of the motor for a vehicle is stopped. 3. The electric power steering apparatus for a cargo handling vehicle according to claim 1, wherein the brake is a deadman brake that operates when the driver is not driving. 4. The electric vehicle in a cargo handling vehicle according to claim 3, wherein the cargo handling vehicle is a forklift including a brake that operates when the handle is vertically erected and when the handle is tilted substantially horizontally. Type power steering device. 5. The electric power steering system for a cargo-handling vehicle according to claim 3, wherein the cargo-handling vehicle is a reach-type forklift, and the brake operates in a state where the brake pedal is released. apparatus. 6. The cargo handling vehicle is a counterbalance type forklift, and the brake is a foot brake or a side brake that operates when the brake pedal is depressed.
An electric power steering device for a cargo handling vehicle according to claim 1.