JPH0446501A - Drive control method for electric vehicle - Google Patents

Abstract

PURPOSE:To prevent useless deceleration/stoppage by varying the limit circuit temperature of a wheel drive motor, in which rotation control is performed based on the duty ratio, based on the variation of outer air temperature thereby modifying the duty ratio. CONSTITUTION:A CPU 5 changes over switches 13, 14 according to the traveling direction and speed set in a speed command signal generator 31 and rotates a motor 1 forwardly or reversely and then controls the speed of the motor 1 through control of the duty ratio D of FETs 6, 7. Temperature X of electronic components such as the FETs 6, 7 is detected through a sensor 2 and the outer air temperature Y is detected through a sensor 3 and then they are provided to a CPU 5. The CPU 5 obtains a sub-limit temperature X1 and a limit temperature X2, corresponding to the outer air temperature Y, from a ROM 30. D remains as it is if X<X1, decreases with a rate of (X2- X)/(X2- X) if X1<X<X2, and brought to zero if X2<X thus stopping the motor 1 and providing a display 26. Consequently, useless deceleration/stoppage can be prevented when the outer air temperature is low. The control method is preferably employed in a motor car or a forklift.

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 battery, and use relays and microcomputers to control the motor's rotational speed 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.

(I1! Problem to be solved by the invention) The safety function of the electric vehicle described above detects when an excessive current flows in the control circuit and generates heat in the control circuit when the motor is overloaded, and the detected control The motor rotation is reduced or stopped when the circuit temperature reaches a predetermined limit temperature, but the control circuit temperature is easily affected by the outside temperature, and in winter, the control circuit temperature does not reach the predetermined limit. The motor will overheat and burn out by the time it reaches its limit temperature, and in the summer, the control circuit temperature tends to reach its limit temperature, causing the motor to often slow down or stop even though the motor is not deenergized. Become.

(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, so that the wheel drive motor 1 runs at a set speed, and the circuit temperature sensor 2
The circuit temperature X detected at is the limit temperature XI, X! In an electric vehicle that is controlled so that the duty ratio decreases or becomes zero when the temperature becomes higher, the above-mentioned limit temperatures X+ and Xs are calculated based on the outside air temperature sensor 3 and the outside air temperature Y detected by this outside air temperature sensor 3. A limit temperature calculating means 4 is provided to change the limit temperatures X+ and X□ according to changes in the outside air temperature Y.

(Operation and effect of the invention) The outside air temperature Y detected by the outside air temperature sensor 3 is the limit temperature X
1. If it becomes lower than X2, the duty ratio is controlled so that the set speed is achieved, and the outside temperature Y reaches the limit temperature X.
If it becomes higher than +, , the limit temperatures X+, Xz are changed by the limit temperature calculation means 4 according to changes in the outside air temperature Y, and the circuit temperature X is adjusted to an appropriate limit temperature X+ depending on whether the outside air temperature is low or high.
, Xt, it is possible to accurately detect the overheating state of the motor 1 and prevent the motor 1 from frequently decelerating or stopping, while avoiding burnout due to overheating.

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

First, the drive control circuit is as shown in the electrical circuit diagram of FIG. That is, the central arithmetic unit CF'Ll 5 turns on the field-effect drive transistor 6 and the braking transistor 7 that control the wheel drive motor 1 based on the running speed set by the speed command signal generator 31. ,0
PFI411? I am supposed to do it.

These transistors 6 and 7 are connected in series, and have a diode 6a inside that operates when reverse biased.
and 7a are incorporated. And transistor 6
The drain side of the transistor 7 is connected to the voltage S of 24V (<the battery terminal G), 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 IO 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 a.

b, and terminals c and d. The current value detected by the current detector 15 is sent to the arithmetic unit W5 through the amplifier 32, and if an overcurrent flows, the main relay 22 is turned off.
Make it. In addition, in FIG. 3, 16 is an electromagnetic brake that tightens the rotating shaft of the wheel drive motor 1 to decelerate and stop it. This 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 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 and OFF of relays 11 and 12. 21 is a rotation speed detector.

This rotation speed detector 21 is for calculating the rotation speed of the motor 1 (travel speed of the electric vehicle) by detecting a back electromotive force generated by the wheel drive motor 1. Furthermore, 22 is a main relay, 23 is its contact, 2 is a circuit temperature sensor that detects the temperature of electronic components, and 3
25 is an inverter that controls the main relay 22 to turn ON and 0FFffil+; 26 is a display device that displays the pantry voltage using, for example, five LEDs; and 31 is a speed command signal generator.

The ROM 30 stores the outside air temperature Y and the circuit temperature X shown in Fig. 2.
Data indicating the relationship between the quasi-limit temperature X and the limit temperature X is stored. Note that this data was obtained through experiments.

In such a drive circuit for the electric vehicle 1, the drive state is controlled by the outputs of the terminals PCI and PC2 of the CPU 5,
The outputs of PC6 and PC7 are set to L” level or “H””
This is done by changing levels.

pct 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 Pct are wheel drive motor 1
The 0 energization time is used to determine the running speed of the electric vehicle by controlling the energization time. The speed is controlled to a set speed determined by the 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 being 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
is arranged about 2 to 3 pulses after 1 in 1 cycle, and detects the back electromotive force of the motor 5 at that time to detect the running speed of the electric vehicle.

When setting the drive signal to the state of A, both terminals PC6 and PC7 of CI'll 5 are outputted at the "■(" level).

When PC6 is at the "14" level, the gate voltage of transistor 8 is lowered by inverter 9, and transistor 8 is turned off. Therefore, the voltage on the gate side of the transistor 6 becomes high, and the driving transistor 6 is turned on. Furthermore, when I'C7 is at the "11" level, the gate voltage of transistor 7 is lowered by inverter 10,
Transistor 7 becomes OF['. This state is the case of the drive signal A, and +24V power supplied from the battery is supplied to the wheel drive motor 1 via the 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.

When using braking signal B, PC6 and pc7 of CPU4
Both outputs are set to "11" level. When the PC6 is at the "L" level, the transistor 8 is turned on and the driving transistor 6 is turned off.

Furthermore, 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 l through the drive transistor 6, and the motor 1 is rotated by inertia. Release l
It will not function as an i-machine.The generated electricity will pass through relay contact 13.
or 14, it is returned to the motor 1 side through the braking transistor 7, and a load is applied to the mole 1 to perform dynamic braking.

To set the neutral signal N, connect the terminal pc6 of the CPU 4 to “
[," level, and terminals P and C7 are set to H" level.

That is, both driving and braking transistors 6 and 7 are turned off. As a result, the wheel drive motor 1 is placed in a state where no load is applied, and the rotation detector 21 detects the voltage generated by the inertial rotation.
The system detects the rotational speed of the electric vehicle and determines the traveling speed of the electric vehicle. The generated electricity is accumulated in the battery through reverse bias transistors 6a and 7a, and so-called regenerative braking is performed.

Output ratio (%) of drive signal A in one cycle
is the duty ratio, but this duty ratio is the rotation detection! It is changed and controlled based on the deviation between the actual running speed and the set speed calculated from the detected voltage in S21.

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 set the traveling speed, the duty ratio is determined so that the vehicle travels at this set speed. This duty ratio is changed according to fluctuations in running load.

In addition, the temperature X near the electronic components such as the transistors 6 and 7 is measured by the circuit temperature sensor 2, and the outside air temperature Y is measured by the outside air temperature sensor 3 installed at a position away from the control circuit and the motor 1.
Measure.

Next, the quasi-limit temperature X+limit temperature X stored in the ROM 30 is calculated from the outside air temperature Y. This temperature X+, X*
increases as the outside air temperature Y increases.0For example, when the outside air temperature Y is 0°C, X is 37.5°C, and X is 40,
5℃, but when the outside temperature Y is 30℃, Xl is 57℃
Therefore, X is 60.5°C.

Furthermore, the circuit temperature X is compared with the semi-limit temperature X calculated before and the limit temperature X, and if the semi-limit temperature Limit temperature X, and limit temperature X! If it is within the range, the motor 1 is driven by changing the duty ratio expressed by the following equation.

Xt -X.

In other words, the closer the circuit temperature It turns out.

If the circuit temperature X becomes higher than the limit temperature X8, the duty ratio is set to zero and the motor 1 is stopped.

The state in which the motor 1 is controlled based on the changed duty ratio is an overload operating state, and this state is displayed on the display device 26 using light emitting diodes shown in FIG. When the quasi-limit temperature X1 is exceeded, the light emitting diode LED of the display device 26 is blinked to indicate that an overload operating state is present. 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 stage of overload operation.

[Brief explanation of the drawing]

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 outside air temperature and circuit temperature limit temperature, and Fig. 3 is drive control. FIG. 4 is an electric circuit diagram showing the circuit, and a time chart showing the control pattern. 1...Motor 2...Circuit temperature sensor 3...Outside air temperature sensor 4...Limit temperature calculation means X...Circuit temperature X,...Semi-limit temperature X,
...Limit temperature Y...Outside air temperature D...Duty ratio Figure 2 Outside air temperature Y ('c)

Claims (1)

[Claims] The rotation of the wheel drive motor 1 is controlled by changing the duty ratio D, which is the output ratio of the drive signal, so that it runs at the set speed, and the circuit temperature X detected by the circuit temperature sensor 2 is controlled.
In an electric vehicle that is controlled so that the duty ratio D is reduced or made zero when becomes higher than the limit temperature X_1, X_2, the above-mentioned limit temperature is X_1,
A drive control method for an electric vehicle, characterized in that limit temperature calculation means 4 for calculating X_2 is provided, and limit temperatures X_1 and X_2 are changed according to changes in outside air temperature Y.