JPH0442705A - Electric vehicle drive control method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an electric vehicle that runs using the driving force of a motor, and the motor is subject to abnormal heat generation due to an overload operating condition such as continuous driving on a steep slope. This invention relates to a drive control method that prevents this from occurring.

(Prior Art) Electric vehicles include wheelchair types for physically disabled people and work vehicle types such as forklifts. These electric vehicles are equipped with a DC motor and a battery, and use relays and microcomputers to control the rotational speed of the motor so that they run at a desired speed.

In addition, electric vehicles have a safety function that detects abnormal heat generation in the control circuit that controls the motor rotation speed and reduces the motor rotation speed or stops driving, as described in Japanese Patent Publication No. 56-4081. There are some that have.

(Problem to be Solved by the Invention) The safety function of the electric vehicle described above is to detect overload of the motor due to abnormal heat generation in the control circuit, but since the temperature of the control circuit is strongly influenced by the outside temperature, In winter, the temperature of the control circuit is difficult to rise, and by the time the control circuit reaches an abnormal temperature, the temperature inside the motor may rise and cause burnout. To prevent this, it would be possible to provide a sensor that directly detects the internal temperature of the motor, but it is difficult to provide a sensor inside the rotating motor.

Therefore, in the present invention, focusing on the fact that the internal temperature of the motor is related to the temperature rise of the control circuit and the environmental temperature around the vehicle body, that is, the outside air temperature, the following steps are taken to prevent abnormal heat generation of the motor. did.

(Means for Solving the Problems) Therefore, in the present invention, the rotation of the wheel drive motor 1 is controlled by changing the duty ratio, which is the output ratio of the drive signal, and the electric vehicle is controlled to run at a set speed. A circuit temperature sensor 2 that detects the temperature of electronic components for use in the computer and an outside air temperature sensor 3 that detects the outside air temperature are provided, and both sensors 2.
A motor temperature calculation means 4 is provided for calculating the internal temperature of the motor 1 from the detected temperature of No. 3, and when the motor temperature Z calculated by this means exceeds a predetermined temperature of 20, the duty ratio is appropriately decreased.

(Operations and Effects of the Invention) The circuit temperature sensor 2 that detects the temperature of control electronic components is designed to prevent electronic components and control boards from malfunctioning due to heat generation in the control electronic components due to overload operation such as continuous driving on steep slopes. This prevents the car from running out of control or becoming inoperative, and the outside temperature detected by the outside temperature sensor 3 is used to control battery charging time.

In this invention, the motor 1 is difficult to provide with a sensor.
Instead of directly detecting the internal temperature of the motor 1, the internal temperature of the motor 1 is calculated from the temperatures detected by the circuit temperature sensor 2 and the outside temperature sensor 3, which are used for other controls, which greatly reduces manufacturing costs. The motor temperature calculation means 4 can calculate the temperature inside the motor according to the change in the outside temperature without any trouble, and when the calculated temperature Z reaches a predetermined temperature 21 or higher, the duty ratio is decreased, so the rotation of the motor 1 is decreased. Thus, burnout of the motor 1 due to overload operation can be prevented.

(Example) Next, an example of the present invention will be described with reference to the drawings.

First, the drive control circuit is the remainder shown in the electrical circuit diagram of FIG. That is, the central arithmetic unit CPU 5 turns on the field-effect drive transistor 6 and the braking transistor 7 that control the wheel drive motor 1 at the running speed set by the speed command signal generator 31. ,
○It is designed for FF control. 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 +2
It is connected to the 4V power supply (+ 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 1 is connected between the intermediate connection point of the transistors 6 and 7 and the ground side via the contacts 13 and 14 of the forward/reverse switching relays 11 and 12 and a current detector 15. . The relay contacts 13 and 14 each have two terminals ab and terminals c and d. The current value detected by the current detector 15 is sent to the arithmetic unit 5 through the amplifier 32, and if current flows through the current, the main relay 22 is turned off. In addition, in Fig. 3, 16
Tightens the rotating shaft of the wheel drive motor to decelerate and stop it! It is magnetic damping. The electromagnetic brake 16 releases the rotating shaft of the motor 1 in an energized state, and tightens the rotating shaft of the motor 1 by a spring force in a non-energized state.

Further, in the figure, numerals 17 and 18 are two-stage amplification transistors of the magnetic damping 16. Furthermore, 19 and 20 are
An inverter 21 that controls ON/OFF of the IJ relays 11 and 12 is a rotation speed detector. This rotation speed detector 2
1 is for calculating the rotation speed of the motor 1 (travel speed of the electric vehicle) by detecting a back electromotive force when the wheel drive motor 1 generates a back electromotive force. Yet another 2
2 is the main relay, 23 is its contact, 2 is a circuit temperature sensor that detects the temperature of electronic components, 3 is an outside temperature sensor that detects the outside temperature, 25 is the main relay 22, ○N,
The inverter 26 that performs OFF control is a display device that displays the battery voltage using, for example, five LEDs, and 31 is a speed command signal generator.

In such a drive circuit for electric vehicle 1, the drive state is controlled by switching the outputs of terminals PCI and PC2 of CPt15 and the outputs of PC6 and PC7 from the "L" level to the 6H" level. ing.

pcl and pc2 are contacts a of relay contacts 13 and 14
, b, c, and d to rotate the wheel drive motor 1 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.

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. In addition, pc6 and PC7 are wheel drive motors 1
The zero energization time, which is used to determine the running speed of the electric vehicle by controlling the energization time, is determined by the opening degree of the throttle lever and the state of the speed selector switch B (high speed, medium speed, low speed). The speed is controlled to a set speed determined by the speed command signal generator 31.

The specific energization time is controlled as follows. That is, for example, as shown in FIG.
The time of one cycle of ms is further divided into 50 sections, during which the drive signal A, braking signal B, and neutral signal N are outputted at a predetermined ratio according to each running condition. Drive signal A
is being output, +2 to wheel drive motor 1
4V power is supplied, and the number of revolutions of the electric tricycle increases depending on the time the power is supplied. Further, while the braking signal B is output, the motor 1 functions as a generator, and the generated electricity is returned to the motor 1 through the transistor 7, so that dynamic braking is performed. In addition, neutral signal N
Approximately 2 to 3 pulses are placed on at in one cycle, and the counter electromotive force of the motor 5 at that time is detected to detect the running speed of the electric vehicle.

To set the state to drive signal A, connect the terminal PC of CPU 5.
Both PC 6 and PC 7 output "H" level.

When PC6 is at °H” level, the gate voltage of transistor 8 is lowered by inverter 9, and transistor 8
becomes OFF. Therefore, the voltage on the gate side of the transistor 6 becomes high, and the driving transistor 6 is turned on. Also, when PC7 is at 'H' level, inverter 1
0, the gate voltage of the transistor 7 decreases, and the transistor 7 is turned off. This state is the case of drive signal A, and the +24V power supplied from the battery is
It is supplied to the wheel drive motor 1 via a relay contact 13 or 14. The current then flows through the current detector 15 to the ground side. Therefore, the wheel drive motor 1 is rotationally driven.

To set braking signal B, PC6 and p of CPU4
Both outputs of cl are set to "H" level. When the Pc6 is at the "L" level, the transistor 8 is turned on and the driving transistor 6 is turned off. Moreover, when PC7 is "L level", the braking transistor 8 is turned on. Therefore, power from the battery is no longer supplied to the wheel drive motor 1 through the drive transistor 6, and the motor 1 is rotated by inertia. Functions as a generator.

The generated electricity is returned to the motor 1 side through the relay contact 13 or 14 and the braking transistor 7, and applies a load to the motor 1 to perform dynamic braking.

To set the neutral signal N, connect the terminal pc6 of the CPU 4 to “
"L" level and sets the terminal PC7 to "H" level. In other words, both driving and braking transistors 6 and 7 are turned OFF.
Make it FF. As a result, the wheel drive motor 1 is in a state where no load is applied, and by detecting the voltage generated by inertia rotation with the rotation detector 21, the rotation speed of the motor 1 is detected, and the running speed of the electric vehicle is determined. That's what I do. Then, the generated electricity is accumulated in the battery side through reverse bias transistors 6a and 7a, and so-called regenerative braking is performed.

Ratio of output to drive signal in one cycle (%)
is the duty ratio, and this duty ratio is changed and controlled based on the deviation between the actual traveling speed calculated from the detected voltage of the rotation detector 21 and the set speed.

Next, the drive control method will be explained based on the flowchart shown in FIG. 1 as follows.

When the circuit is energized and the speed command signal generator 31 is operated to start running, the circuit temperature sensor 2 measures the temperature X near the electronic components such as the transistors 6, 7, etc. The outside air temperature Y is measured by the provided outside air temperature sensor 3.

First, compare the circuit temperature
If it is higher, the circuit temperature X is further compared with the operating limit temperature X2, for example 68°C.

As a result, if the circuit temperature The motor 1 is driven by changing the output duty ratio to the duty ratio expressed by the following equation.

In other words, the closer the circuit temperature X is to the operating limit temperature It is necessary to wait until the temperature becomes lower than the limit temperature Xl.

The motor temperature calculating means 4 that calculates the motor temperature Z is as follows.

First, as shown in Fig. 2, the relational data among the circuit temperature The motor temperature Z in the ROM 30 is read from the temperature Y.

Another method is to obtain the motor temperature Z shown in Fig. 2 as a function of the circuit temperature .

The motor temperature Z obtained in this way is first determined at a quasi-limit temperature Z1 close to the motor operating limit temperature Zt, for example, 150°C.
If it is lower than this, the speed command signal generator 3
The motor 1 is driven at a duty ratio that achieves the speed set in step 1, and if it is higher than this, it is further compared with the limit temperature Z, for example 160°C. As a result, if the motor temperature Z is higher than the limit temperature Z2, the motor 1 cannot withstand it.
The motor 1 is stopped by setting the duty ratio to 0, and if the temperature is below the limit temperature Z, the motor 1 is driven by changing the duty ratio to the duty ratio expressed by the following equation.

In other words, in this case as well, the closer the motor temperature Z is to the limit temperature Z8, the smaller the duty ratio, that is, the output, will be made to run at a slower speed than the speed set by the speed command signal generator 3], and the motor temperature 2 becomes lower than the quasi-limit temperature Z1.

The state in which the motor 1 is controlled using such a changed duty ratio is an overload operating state, and this state is displayed on a display device 26 using light emitting diodes as shown in FIG. 3. When the degree X exceeds the semi-limit temperature Xl or the motor temperature Z exceeds the semi-limit temperature Z, the light emitting diode LED at the front of the display device 26 is made to blink to indicate that the motor is in an overload operating state. There is. When the value of the modified duty ratio is large, the blinking interval is increased, and when it is small, the blinking interval is decreased to display the current stage of overload operation.

[Brief explanation of drawings]

The figures show one embodiment of the present invention, in which Fig. 1 is a flowchart showing the control state, Fig. 2 is a data graph showing the relationship between circuit temperature, outside air temperature, and motor temperature, and Fig. 3 is a drive control circuit. FIG. 4 is a time chart showing the control pattern. 1...Wheel drive motor 2...Circuit temperature sensor 3...Outside air temperature sensor 4...Motor temperature compensation means X...Circuit temperature Y...Outside air temperature Z...Motor temperature Figure 2

Claims (1)

[Claims] In an electric vehicle that runs at a set speed by controlling the rotation of a wheel drive motor 1 by changing the duty ratio D, which is the output ratio of a drive signal, a circuit temperature sensor 2 that detects the temperature of control electronic components and an outside air temperature are used. an outside air temperature sensor 3 for detecting the temperature, and a motor temperature calculation means 4 for calculating the internal temperature of the motor 1 from the temperatures detected by both sensors 2 and 3.
A drive control method for an electric vehicle, characterized in that the duty ratio D is appropriately decreased when the motor temperature Z calculated thereby becomes a predetermined temperature Z_1 or higher.