JP2507584B2 - Drive wheel slip prevention device for electrically propelled vehicle - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive wheel slip prevention device for an electric propulsion vehicle such as a reach type forklift truck.

(Prior Art) Conventionally, as a drive wheel slip prevention device for an electrically propelled vehicle, for example, a device as shown in FIG. 6 has been known.

In this conventional device, when an electric output is obtained from the accelerator unit (2) in response to a depression operation of the accelerator pedal (1), and when the accelerator pedal opening is suddenly fully opened by sudden depression of the accelerator pedal (1). Is converted by the soft start device (3) so that the output from the accelerator unit (2) changes gently as in the case of gentle depression of the accelerator pedal (1), and a command is given to the travel motor controller (4). The feeding traveling motor (5) is gradually activated.

As described above, the occurrence of drive wheel slip at the time of starting is prevented.

(Problems to be Solved by the Invention) However, in such a conventional device, the soft start constant of the soft start device (3) is fixed, and in general, the road surface friction coefficient on a dry road and the empty vehicle Since the constant is set based on the driving wheel load under the condition, when the actual road surface friction coefficient changes with respect to the road surface friction coefficient reference value or when the actual driving wheel load or change with respect to the driving wheel load reference value In such a case, there is a problem that there is no responsiveness to these changes and the occurrence of drive wheel slip is allowed due to changes in road surface conditions and vehicle conditions.

Incidentally, in a drive wheel slip prevention device for a passenger car equipped with an internal combustion engine, a vehicle speed and a wheel speed of each drive wheel are detected by a sensor, a slip ratio and a slip ratio are obtained, and this calculated value exceeds a set value. In this case, there is known a device that prevents the drive wheels from slipping by reducing the driving force or applying the braking force.

However, in this case, a special drive wheel slip detection system using a vehicle body speed sensor, a wheel speed sensor, etc. is required.

(Object of the Invention) The present invention has been made by focusing on the above-mentioned problems, and it is possible to respond to a change in road surface condition or a change in vehicle condition without requiring a special drive wheel slip detection system. It is an object of the present invention to provide a drive wheel slip prevention device for an electrically propelled vehicle that can effectively prevent the occurrence of slip.

(Means for Solving the Problem) In order to achieve the above object, the drive wheel slip prevention device for an electrically propelled vehicle of the present invention detects the occurrence of drive wheel slip based on the current value of a power steering motor or a traveling motor. However, a means for correcting the soft start constant of the soft start device to an optimum value when driving wheel slip is predicted or when driving wheel slip occurs.

That is, in the apparatus according to claim 1, the steering motor control system that controls the current of the power steering motor according to the torque applied to the steering wheel, and the accelerator command to the traveling motor is gently changed in response to the sudden depression of the accelerator pedal. In an electric propulsion vehicle equipped with a traveling motor control system having a soft starter for
Drive wheel load calculation means for calculating a drive wheel load based on a current value of the power steering motor or a torque value applied to the steering and a conduction ratio for controlling the power steering motor is provided, and the drive wheel load is also provided. It is characterized in that soft start constant correcting means for correcting the soft start constant of the soft start device to an optimum value according to the calculated value is provided.

The electric propulsion vehicle according to claim 2, further comprising: a travel motor control system having a soft starter that gently changes an accelerator command to the travel motor in response to a sudden depression of an accelerator pedal. Drive wheel slip detection means for detecting drive wheel slip based on the current value when the control current falls to the traveling motor or the time until the control current falls is provided, and when the drive wheel slip is detected, the soft start is performed. A soft start constant correcting means for correcting the soft start constant of the container to an optimum value is provided.

(Operation) <Operation of the device according to claim 1> At the time of starting, the drive wheel load computing means controls the current value of the power steering motor or the torque value applied to the steering and the duty ratio for controlling the power steering motor. The drive wheel load is calculated based on

That is, since the driving wheel load has a value corresponding to the steering resistance during steering, this value is obtained as a value including both the road surface friction coefficient element and the driving wheel load element.

When the drive wheel load calculation value is obtained, the soft start constant correcting means corrects the soft start constant of the soft starter to an optimum value according to the drive wheel load calculation value.

Therefore, at the time of starting, the accelerator command that is gently changed by the optimum soft start constant that does not cause the drive wheel slip is output from the soft start device to the travel motor.

<Operation of the device according to claim 2> At the time of starting, the drive wheel slip detection means detects the drive wheel slip based on the current value at the time of the fall of the control current to the traveling motor or the time until the control current falls. .

That is, monitoring the falling of the control current to the traveling motor means monitoring the back electromotive force generated in the traveling motor after the motor is started according to the traveling resistance received by the driving wheels. It is obtained as a value that includes both the friction coefficient element and the driving wheel load element.

Then, when the drive wheel slip is detected, the soft start constant correcting means corrects the soft start constant of the soft starter to an optimum value for ensuring the start while suppressing the occurrence of the drive wheel slip.

Therefore, at the time of starting, the accelerator command that is gently changed by the optimum soft start constant that does not cause the drive wheel slip is output from the soft start device to the travel motor.

(Example) Hereinafter, the Example of this invention is described based on drawing.

FIG. 1 shows a drive wheel slip prevention device for a reach type forklift truck according to a first embodiment of the invention. First, the structure will be described.

The reach type forklift truck is an electrically propelled vehicle in which the rear wheels are the driving wheels and the steered wheels, and the steering motor control system 1 that controls the current of the power steering motor 14 according to the torque applied to the steering wheel and the sudden pedal of the accelerator pedal 21. A travel motor control system 2 having a soft starter 23 that gently changes an accelerator command to the travel motor 25 in response to a pedaling operation, and a drive wheel slip prevention device that prevents drive wheel slip in relation to both systems 1 and 2. 3 is installed.

The steering motor control system includes a steering torque sensor 11 for detecting a torque applied to steering, a target current calculator 12 for setting a target current to be supplied to the power steering motor 14 by calculation, and a command from the target current calculator 12. Value and the feedback current value from the power steering current sensor 15 are controlled so as to increase or decrease the flow rate, and a power steering motor 14 that applies a steering assist force to the steering wheel.
And a power steering current sensor 15 for detecting an actual current value applied to the power steering motor 14.

The traveling motor control system 2 includes an accelerator pedal 21 as an accelerator operating means, and an accelerator unit 22 that obtains an electric output according to a depression operation on the accelerator pedal 21.
And a soft start device that converts the accelerator command from the accelerator unit 22 so as to change gently when the accelerator opening is suddenly fully opened by suddenly pressing the accelerator pedal 21.
23, and a travel motor controller 24 that applies a control current to the travel motor 25 in response to an accelerator command from the soft starter 23.
And a traveling motor 25 that applies a rotational driving force to the drive wheels in accordance with the current applied from the traveling motor controller 24.

The drive wheel slip prevention device 3 includes a predicted conduction ratio calculator 31 for calculating and setting a predicted conduction ratio according to the output from the steering torque sensor 11, and an output from the predicted conduction ratio calculator 31 and the communication ratio. A duty ratio comparator 32 that calculates a difference from the output from the flow rate calculator 13, and a drive wheel load according to the difference from the duty ratio comparator 32, and according to the drive wheel load. And a soft start constant calculator 33 for calculating the optimum value of the soft start constant and changing the soft start constant of the soft start device 23.

That is, the predicted flow rate calculator 31, the flow rate comparator 32, and a part of the soft start constant calculator 33 constitute driving wheel load calculating means, and the soft start constant calculator 33 constitutes soft start constant correcting means. Has been done.

 Next, the operation will be described.

For example, when the load applied to the rear wheels, which are both steering wheels and driving wheels, or the road surface friction coefficient decreases, the steering resistance also decreases accordingly, so that the power steering motor 14 obtains the same motor current. Need to give.

That is, when the driving wheel load is obtained based on the torque value applied to the steering wheel and the conduction ratio controlling the power steering motor 14, the value of this driving wheel load is the road surface friction coefficient element and the driving wheel load element. Is obtained as a value including both, and this is utilized in the apparatus of the first embodiment.

FIG. 2 is a flow chart showing the flow of operation in the steering motor control system 1 (two-dot chain line) and the flow of operation in the drive wheel slip prevention device 3 (solid line), and the flow of operation will be described based on this flow chart. .

In the steering motor control system 1, the power steering motor is controlled according to the output from the steering torque sensor 11 and the output from the power steering current sensor 15.
It controls the current flowing to 14.

That is, in step a, the steering torque sensor 11
The target current calculator 12 sets the target current according to the output from the power steering current sensor 15 in step b.
The current power steering current is detected by, and in step c, it is compared whether the difference between the current value and the target current value is less than or equal to a specified value.

When it is determined in step c that the difference between the current values exceeds the specified value, the process proceeds to step d, and the conduction ratio calculator 13 determines whether or not the current current value is equal to or more than the target current value. In the case of YES, the process proceeds to step e, where the flow rate is reduced by a prescribed amount, and in the case of NO, the process proceeds to step f, where the flow rate is increased by the prescribed amount.

In the drive wheel slip prevention device 3, the drive wheel load is calculated based on the torque value applied to the steering wheel and the conduction ratio controlling the power steering motor 14, and the soft start is performed according to the drive wheel load. The soft start constant of the device 23 is corrected to the optimum value.

That is, if YES is determined in step c, the process proceeds to step g, and in step g, the steering torque sensor is
The predicted flow rate is set according to the output value from 11. Then, in step h, the drive wheel load is calculated from the map data based on the difference between the predicted flow rate and the current flow rate, and in step i, the traveling soft start constant is set from the map data according to the drive wheel load.

Therefore, the soft start constant is corrected to the optimum value corresponding to the load applied to the steered wheels and the drive wheels and the road surface friction coefficient based on the calculated value of the drive wheel load, and the drive wheel slip is effectively prevented at the start. It

As described above, in the drive wheel slip prevention device for the reach type forklift truck of the first embodiment, by using the step motor control system 1,
Without the need for a special drive wheel slip detection system
It is possible to effectively prevent the occurrence of drive wheel slip in response to changes in road surface conditions and vehicle conditions.

As a result, it is possible to improve the power consumption rate and extend the life of the tire.

FIG. 3 shows a drive wheel slip prevention device for a reach type forklift truck according to a second embodiment of the present invention. The structure will be described first.

When the accelerator pedal 21 is pressed suddenly, the drive motor 25
A travel motor control system 2 having a soft starter 23 for gently changing an accelerator command to the drive motor and a drive wheel slip prevention device 4 for preventing drive wheel slip are mounted in association with the travel motor control system 2.

Since the traveling motor control system 2 has the same configuration as that of the first embodiment, its explanation is omitted.

The drive wheel slip prevention device 4 detects a current detector 41 that detects a current flowing to the traveling motor 25, and a current value when the detected current from the current detector 41 falls or a time until the current falls. The current fall detector 42 (driving wheel slip detecting means) that performs the slip determination based on the current value or time, and when the slip occurs, the accelerator command is decreased by a certain amount and the soft start constant (time constant) of the soft start device 23 is set. A soft start corrector 43 (soft start constant correcting means) for correcting to an optimum value is provided.

 Next, the operation will be described.

Since the motor is initially locked when the motor is started, the charging current flows as the starting current as shown in FIG.

At this time, a torque corresponding to the current value is generated, and the traveling motor 25 rotates from the time when this torque becomes equal to or higher than the torque at which the drive wheels can operate.

Then, since the back electromotive force is generated in the traveling motor 25 by the rotation of the traveling motor 25, the motor current decreases from this point.

In other words, when the drive wheel slip occurs, the falling current value of the motor current and the fall time become small, and the drive wheel slip can be detected by detecting at least one of them. This is the device of the second embodiment.

FIG. 5 is a flow chart showing the flow of operation in the drive wheel slip prevention device 4 (solid line) and the flow of operation in the traveling motor control system 2 (two-dot chain line), and the flow of operation will be explained based on this flow chart. To do.

In step j, it is judged whether or not the vehicle is starting. If it is not starting, the process proceeds to step k, the soft start constant is reset, and the judgment in step j is repeated.

If it is determined in step j that the vehicle has started, the previous and current motor currents are stored in the memory in steps 1 and m.

Whether or not the condition that the motor current increase amount is less than the specified value (step n) and the condition that the current motor current is less than the current value when the drive wheels are not slipping (step o) are satisfied are determined. Drive wheel slip is detected.

When the drive wheel slip is detected, it is determined in step p whether or not the correction flag is set, the correction flag is set in step q, and the flow rate is reduced to a specified value in step r. At s, the soft start constant is reduced by a specified amount.

If the drive wheel slip does not occur at the time of starting, the process proceeds from step n to step t. If the flag during correction is set, this is cleared, and further, step u
In step v, the target flow rate is set according to the accelerator opening. In step v, it is determined whether the current flow rate is greater than or equal to the target flow rate. If NO, in step w the flow rate is set according to the soft start constant. The process of increasing the rate is performed.

Therefore, at the time of starting, in the drive wheel slip detection means, the drive wheel slip is detected by the current value when the control current to the traveling motor 25 falls, and when the drive wheel slip is detected, the soft start corrector 43 causes The accelerator command is reduced by a certain amount and the soft start constant of the soft starter 23 is corrected to an optimum value, so that the drive wheel slip is effectively prevented at the time of starting.

As described above, in the drive wheel slip prevention device for a reach type forklift truck of the second embodiment, by using the traveling motor control system 2, a special drive wheel slip detection system is not required, Moreover, even though the vehicle is not equipped with electric power steering, it is possible to effectively prevent the occurrence of drive wheel slip in response to changes in road surface conditions and vehicle conditions.

As a result, it is possible to improve the power consumption rate and extend the life of the tire.

Although the embodiment has been described above with reference to the drawings, the specific configuration is not limited to this embodiment.

For example, in the first embodiment, an example is shown in which only the soft start constant is corrected to the optimum value when the occurrence of the drive wheel slip is predicted and detected, but as in the second embodiment, the accelerator command is added in addition to the constant correction. The amount may be decreased by a certain amount, or conversely, in the case of the second embodiment, the control for decreasing the accelerator command by a certain amount when the occurrence of the drive wheel slip is detected may be omitted.

Further, the applicable vehicle is not limited to the reach type forklift truck, and can be applied to various electric propulsion vehicles.

(Effects of the Invention) As described above, in the drive wheel slip prevention device for an electrically propelled vehicle according to claim 1, the occurrence of drive wheel slip is predicted and detected based on the power steering motor current value. Since the soft start constant of the soft start device is corrected to the optimum value when driving wheel slip is predicted to occur, there is no need for a special driving wheel slip detection system, and changes in road surface conditions and vehicle conditions Accordingly, it is possible to effectively prevent the occurrence of the drive wheel slip.

Further, in the drive wheel slip prevention device for an electrically propelled vehicle according to claim 2, the occurrence of the drive wheel slip is detected based on the current value of the traveling motor, and when the drive wheel slip occurs, the software of the soft start device is detected. As a means for correcting the start constant to an optimum value, there is no need for a special drive wheel slip detection system, and even if the vehicle is not equipped with an electric power steering device, changes in road surface conditions and vehicle conditions Accordingly, it is possible to effectively prevent the occurrence of the drive wheel slip.

[Brief description of drawings]

FIG. 1 is an overall system diagram showing a drive wheel slip prevention device for a reach type forklift truck according to a first embodiment of the present invention, and FIG. 2 is a flow chart showing a flow of drive wheel slip prevention control operation in the first embodiment device, FIG. 3 is an overall system diagram showing a drive wheel slip prevention device for a reach type forklift truck according to a second embodiment of the present invention, and FIG. 4 is an explanatory view of the basic principle of drive wheel slip detection of the second embodiment device, and FIG. FIG. 6 is a flow chart showing a flow of drive wheel slip prevention control operation in the first embodiment device, and FIG. 6 is a diagram showing a drive wheel slip prevention device of a conventional reach type forklift truck. 1 …… Steering motor control system 11 …… Steering torque sensor 12 …… Target current calculator 13 …… Commutation ratio calculator 14 …… Power steering motor 15 …… Power steering current sensor 2 …… Travel motor control system 21… … Accelerator pedal 22 …… Accelerator unit 23 …… Soft starter 24 …… Travel motor controller 25 …… Travel motor 3 …… Drive wheel slip prevention device 31 …… Predicted flow rate calculator 32 …… Comparison of flow rate Device 33 …… Soft start constant calculator 4 …… Drive wheel slip prevention device 41 …… Current detector 42 …… Current fall detector 43 …… Soft start compensator

Claims (2)

(57) [Claims] 1. A steering motor control system for controlling a current of a power steering motor according to a torque applied to a steering wheel, and a soft starter for gently changing an accelerator command to a traveling motor in response to a sudden depression of an accelerator pedal. In an electric propulsion vehicle including a traveling motor control system having the drive wheel load based on a current value of the power steering motor or a torque value applied to the steering and a conduction ratio controlling the power steering motor. Electric propulsion, characterized in that drive wheel load calculation means for calculating is provided, and soft start constant correction means for correcting the soft start constant of the soft start device to an optimum value according to the drive wheel load calculation value. Vehicle drive wheel slip prevention device. 2. An electric propulsion vehicle including a traveling motor control system having a soft starter for gently changing an accelerator command to a traveling motor in response to a sudden depression of an accelerator pedal. A drive wheel slip detection means for detecting drive wheel slip is provided by the current value at the time of the current fall or the time until the control current falls, and when the drive wheel slip is detected, the soft start constant of the soft start device is set. A drive wheel slip prevention device for an electrically propelled vehicle, comprising a soft start constant correction means for correcting the optimum value.