JPH03190502A - Overload control method for motor car - Google Patents

Abstract

PURPOSE:To prevent reverse operation by monitoring the speed of a motor car, when the detection value of a temperature sensor is higher than a set value or when the current flowing through a motor is lower than a set value, and forcibly stopping the motor car immediately before the speed of the motor car drops below a limit speed and reverse operation takes place. CONSTITUTION:Provision of the speed of a motor car commences at a time when the temperature detected through a temperature sensor 24 exceeds a set value, and the vehicle speed is monitored. A voltage induced through idling of a wheel drive motor 5 is detected through a voltage detecting circuit 21 in order to detect the r.p.m. of the motor 5. Traveling speed of the motor car is determined based on thus detected r.p.m. and compared with a stop limit speed, and the motor car is stopped immediately before the traveling speed drops below the limit speed and reverse operation takes place. On the other hand, traveling speed is inputted when the current flowing through the motor 5 drops below a set value, and the motor car is stopped forcibly immediately before the traveling speed of the motor car drops below the stop limit speed. By such method, reverse operation can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is designed to prevent electric vehicles from continuously running up steep slopes, etc., resulting in overload operation and abnormal heat generation of electronic parts and motors. The present invention relates to a control method that prevents an electric vehicle from moving backwards during overload control operation.

[Conventional technology]

This type of electric vehicle includes a wheelchair type for physically disabled people, a tricycle type, and a work vehicle type such as a forklift. Basically, both of these systems control the driving state by intermittently controlling the rotation of the wheel drive motor in the forward and reverse directions.

The tricycle-type electric vehicle 1 shown in FIG. 2 was developed by one of the applicants and is already commercially available.

This electric vehicle 1 uses a battery installed in the space below the seat 2 to control the rotation of a wheel drive motor in forward and reverse directions, thereby driving the rear wheels 3 to move forward and backward.

The drive control circuit is as shown in the electrical circuit diagram of FIG. That is, the central calculation value vi (CPU)
4 controls ON/OFF of a field-effect drive transistor 6 and a braking transistor 7 that control the wheel drive motor 5 based on preset conditions. These transistors 6 and 7 are connected in series, and have built-in diodes 6a and 7a that operate during reverse bias. And the drain side of transistor 6 is +24V? ! !
The transistor 7 is connected to the source (+ terminal of the battery), and the source side of the transistor 7 is connected to the ground side. Further, the gate side of the transistor 6 is connected to the drain side of a field effect transistor 8.

9 and 10 are inverters that control the bias on the gate side of transistors 8 and 7.

The wheel drive motor 5 has a forward/reverse switching relay 11 between the intermediate connection point of the transistors 6 and 7 and the ground side.
and 12 through contacts 13 and 14 and a current detection section 15. The relay contacts 13 and 14 each have two terminals a, b and a terminal C2d.

In addition, in FIG. 3, 16 is an electromagnetic brake that tightens the rotating shaft of the wheel drive motor 5 to decelerate and stop it. The electromagnetic brake 16 releases the rotating shaft of the motor 5 in an energized state, and tightens the rotating shaft of the motor 5 by spring force in a non-energized state.

Further, in the same figure, 17 and 18 are the electromagnetic brake 16
This is a two-stage amplification transistor. Furthermore, 19 and 20
is an inverter that controls ON/OFF of relays 11 and 12, and 21 is a rotation speed detection section. This rotation speed detection unit 21 is for calculating the rotation speed of the motor 5 (travel speed of the electric vehicle 1) by detecting a back electromotive force generated by the wheel drive motor 5. . Furthermore, 22 is a main relay, 23 is its contact, 24 is a temperature sensor that detects the temperature of electronic components, and 25 is an inverter that controls the main relay 22 to turn on and off.

In such a drive circuit for the electric vehicle 1, the drive state is controlled by switching the outputs of terminals PCI and PC2 of CPt14 and the outputs of PCB and PC7 to L" level or "H" level. ing.

PCI and PC2 are contacts a of relay contacts 13 and 14.
.

This is for switching between b, c, and d to rotate the wheel drive motor 5 in the forward or reverse direction, or to hold it in the neutral position. This is done by operating the forward/reverse selector switch of the electric vehicle 1.

When switching between terminals a and terminal C and rotating in the normal direction, the motor moves forward, and when switching between terminals A and D and causing the motor to rotate in reverse, the motor moves backward. Moreover, PC6 and PC7 are wheel drive motors 5
By controlling the energization time to
The 0 energization time control, which is used to determine the traveling speed of the vehicle, is determined according to the opening degree of the throttle lever and the state of the speed changeover switch (high speed, medium speed, low speed).

The specific energization time is controlled as follows. That is, for example, as shown in FIG.
The time for one cycle of tis is further divided into 50 sections, during which the accelerator signal A, brake signal B, and neutral signal N are
and is output at a predetermined ratio according to each driving condition. In a state where the accelerator signal A is output, +24V power is supplied to the wheel drive motor 5, and the rotation speed of the electric tricycle 1 increases according to the power supply time.

Further, while the brake signal B is being output, the wheel drive motor 5 functions as a generator, and the generated electricity is returned to the motor 5 through the transistor 7, so that dynamic braking is performed. Note that the neutral signal N is arranged for about 2 to 3 pulses at the end in one cycle, and is used to detect the back electromotive force of the motor 5 at that time and to detect the running speed of the electric vehicle 1.

When setting the state of accelerator signal A, both terminals PCB and PC7 of CI'U 4 are outputted at "I(" level). When PCB is at "H" level, inverter 9 lowers the gate voltage of transistor 8. Then, the transistor 8 turns OFF.Therefore, the gate side voltage of the transistor 6 becomes high, and the driving transistor 6 turns ON.Furthermore, when PC7 is at the "H" level, the gate voltage of the transistor 7 is changed by the inverter IO. In this state, the accelerator signal is applied, and the +24V power supplied from the battery is supplied to the wheel drive motor 5 via the relay contact 13 or 14. The current then flows to the ground side through the current detection section 15. Therefore, the wheel drive motor 5 is rotationally driven.

When setting the brake signal B, both the outputs of the PCB of the CPU 4 and the output of the PC 7 are set to "L" level. When PC6 is at the "L" level, transistor 8 is turned on and driving transistor 6 is turned off.

Further, when PC7 is at the "L" level, the braking transistor 8 is turned on. Therefore, power from the battery is no longer supplied to the wheel drive motor 5 through the drive transistor 6, and the motor 5 functions as a generator due to rotation due to inertia.

The generated electricity is returned to the motor 5 through the relay contact 13 or 14 and the braking transistor 7, applying a load to the motor 5 to perform dynamic braking.

To set the neutral signal N, the terminal PCB of CPII 4 is set to "L" level, and the terminal PC7 is set to 'H' level. In other words, both driving and braking transistors 6 and 7 are turned off. As a result, the wheel drive motor 5 is in a state where no load is applied, and by detecting the voltage generated by inertial rotation with the voltage detection unit 21,
The rotation speed of the motor 5 is detected and the running speed of the electric vehicle 1 is determined. Then, the generated electricity is accumulated in the battery side through reverse bias transistors 6a and 7a, and so-called regenerative braking is performed.

[Problem to be solved by the invention]

When such an electric vehicle 1 continuously travels up a steep slope, etc., the wheel drive motor 5 becomes overloaded, and the motor 5 burns out due to heat, and the drive transistor 6 of the drive control circuit is damaged. Accidents may also occur, such as electronic components such as the braking transistor 7 overheating abnormally and breaking down, resulting in a short circuit. In such a short circuit accident, the accelerator signal A may continue to be sent to the wheel drive motor 5, causing the motor to run out of control and must be avoided. (see figure), and if the value exceeds a reference value such as 47°C, it is determined that an overload operation is occurring, and the proportion of the accelerator signal A output to the wheel drive motor 5 is reduced, and the In order to reduce this, overload control is performed to reduce the average current value by M order.

However, when the average current value to the motor 5 is reduced to a certain level, the climbing force becomes insufficient on steep slopes, etc., and the electric vehicle 1 may fall into a dangerous situation in which it moves backwards. In a system in which the running speed of the electric vehicle is controlled by directly detecting and controlling the rotation speed of the wheel drive motor 5, the detection of this backward state is performed by
This is extremely simple as it is only necessary to detect the rotational speed of the engine. However, in the case of an electric vehicle 1 that employs a control method other than control based on the rotational speed, it is extremely difficult to detect the above-mentioned reverse state, and the number of rotations based on the driver's judgment of the situation is extremely difficult.
We had to rely on TI work, which was an insufficient safety measure.

[Means to solve the problem]

The present invention improves and eliminates the above-mentioned conventional problems, and provides a control method that monitors the speed during overload control operation and stops the electric vehicle immediately before it begins to reverse. This is what I am trying to do.

Therefore, the means adopted by the present invention to solve the above problem is to use a temperature sensor that detects the temperature of electronic components in an electric vehicle that controls the driving state by controlling the forward and reverse rotation of the wheel drive motor. When the signal value is equal to or higher than the reference value, overload control is performed to limit the drive current to the motor, and when the signal value of the temperature sensor becomes equal to or higher than the set value during the overload control operation, or when the drive current to the motor is The speed of the electric vehicle is input and monitored from the time when the drive current value becomes less than the set value, and the electric vehicle is stopped when the speed becomes less than the stop limit speed.

[For production]

According to the present invention, when an electric vehicle is operating under overload control on a steep slope or the like, a detection signal value of a temperature sensor or a current value flowing to a wheel drive motor is compared with a set value.

If the detected value of the temperature sensor is equal to or higher than the set value, the electric vehicle is still operating under overload, and there is a risk that the speed will decrease and the vehicle will go backwards. Furthermore, if the current value flowing to the motor is less than the set value, there is a possibility that the climbing force will be poor and the ball will go backwards. Therefore, in the present invention, when the above-mentioned state is reached, the speed of the electric vehicle is monitored, and the electric vehicle is forcibly stopped just before the speed of the electric vehicle falls below the stopping limit speed and the electric vehicle is about to go backwards, thereby preventing the backward movement. I try to do that.

〔Example〕

The control method of the present invention will be explained below based on the flowchart shown in FIG.

The drive control circuit for the electric vehicle is the same as the one shown in FIG. 3 developed earlier by Betsuto Motoyama.

As shown in FIG. 1, in this embodiment, first, it is detected whether the electric vehicle 1 is in an overload operating state. Detection of overload operation is performed using transistors 6 and 7.
A temperature sensor 24 measures the temperature T near the electronic components, and compares it with a reference value of, for example, 47°C. If the measured temperature T of the electronic component is 47°C or higher, it means that the electronic component is abnormally generating heat, and at the same time, the motor 5 is also generating heat.
It is determined that the system is in an overload operation state. If this state is left unattended, it may lead to damage to electronic parts or burnout of the motor 5, so the CPU 4 performs overload control. The control operation of 0 or more, which is performed by gradually decreasing the motor 5 in one cycle and reducing the load on the motor 5, is the same as in the conventional case.

Note that the detection of whether or not an overload operation is occurring is determined by the value of the current flowing through the wheel drive motor 5! By measuring , it is also possible to predict and determine the temperature T of the electronic component from a predetermined current-temperature characteristic curve.

Therefore, in this embodiment, it is detected that there is a risk that the electric vehicle l will move backward in the operating state where the overload control is performed, and from that point on, the speed input is monitored and the backward movement occurs. The electric vehicle 1 is stopped just before. The temperature sensor 24 detects whether there is a risk of the electric vehicle moving backwards.
Or the measured value T or I obtained by the current detection unit 15 is sent to the CPU.
4 and compare the respective values T and I with the set values.

Here, if the temperature value T measured by the temperature sensor 24 is larger than a set value such as 51° C., the overload operation state is still being continued despite overload control. There will be. Therefore, depending on the gradient of the slope, there is a risk that the climbing force may be insufficient and the ball may go backwards. In such a case, the speed S of the electric vehicle 1 is input and monitored from the time when the temperature value T becomes larger than the set value. The speed S is detected by the voltage detection circuit 21 described above. That is, C
While the neutral signal N is being output from the PU 4 to the drive control circuit, the voltage detection circuit 21 detects the voltage generated by the inertial rotation of the wheel drive motor 5, thereby detecting the rotation speed of the motor 5. The running speed S of the electric vehicle 1 is determined from the rotational speed. The obtained running speed S is then compared with a stop limit speed such as IKm per hour, and the electric vehicle 1 is stopped just before the running speed S becomes smaller than -1. Stopping is performed by turning on the electromagnetic brake 16 in a de-energized state and switching the relay contact 13 or 14 to the neutral position. Therefore, the electric vehicle 1 does not move backward.

On the other hand, in an overload control operating state in which the load is gradually reduced by reducing the energization time of the wheel drive motor 5,
The value of the current flowing through the motor 5! If the current is below a set value, such as 12A, for example, depending on the gradient of the slope, there is a risk that the climbing force will be insufficient and the vehicle will go backwards. Therefore, in this case as well, the traveling speed S is input in the same manner as described above, and the electric vehicle 1 is forcibly stopped just before the traveling speed S of the electric vehicle 1 reaches the stop limit speed or less, thereby preventing the electric vehicle 1 from going backwards. .

By the way, after performing a forced stop to prevent reverse movement, when restarting after the electronic components have cooled and their temperature T has decreased, move the main switch, accelerator lever, etc. to the neutral position. All you have to do is make it so that you can't start unless you set it, to prevent sudden starts.

〔Effect of the invention〕

As explained above, the present invention prevents short-circuit accidents due to abnormal heat generation of electronic components, etc. in overload driving conditions such as on slopes, and performs overload control to control runaway accidents. , the temperature of electronic components or the drive current value of the wheel drive motor are detected and compared with respective set values. Then, from the point when the measured temperature value exceeds the set value or the current value falls below the set value, the running speed of the electric vehicle is input and monitored, and when the running speed reaches the point where the electric vehicle stops. If the speed falls below the speed limit, the electric vehicle is forced to stop, thereby preventing the electric vehicle from moving backwards. That is, in an overload control operating state in which the average current flowing to the wheel drive motor is lowered to gradually reduce the load, reverse movement can be reliably prevented, which is extremely safe.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing an embodiment of overload control for preventing reverse movement of the present invention, and FIGS. 2 to 4 relate to an electric vehicle previously developed by the applicant. 3 is a perspective view showing the entire electric vehicle, FIG. 3 is an electric circuit diagram showing a drive control circuit, and FIG. 4 is a time chart showing a control pattern of a wheel drive motor. 1... Electric vehicle 4... CPU5... Wheel drive motor 15... Current detection section 21... Voltage detection section 24
···Temperature sensor

Claims (1)

[Claims] 1. In an electric vehicle that controls running conditions by controlling forward and reverse rotation of wheel drive motors, when the signal value of a temperature sensor that detects the temperature of electronic components is equal to or higher than a reference value, the drive current to the motor is reduced. Perform overload control to limit the speed of the electric vehicle from the time when the signal value of the temperature sensor exceeds the set value or from the time when the drive current value to the motor falls below the set value during the overload control operation. An overload control method for an electric vehicle, characterized in that the input speed is input and monitored, and the electric vehicle is stopped when the speed becomes equal to or less than a stop limit speed.