JPH099410A - Induction motor controller - Google Patents

Abstract

PURPOSE: To let a minimum current flow even if accelerator is not operated so that it does not go down a slope immediately, by operating an inverter immediately and letting a current flow to an induction motor, by the switch signal being issued when releasing a brake pedal while a forward-reverse changeover switch is on. CONSTITUTION: The power lines 2 and 3 of a battery 1 are connected to an inverter 4, and the delta connection coil terminal of a three-phase induction motor 5 is connected to the inverter 4. The motion of an accelerator 8 is converted into an electric signal, connecting it to an input circuit 6. A forward- reverse changeover switch 9 and a brake switch 10 are connected likewise to the input circuit 6, and the signal processed with the input circuit 6 is applied to a control circuit 12 for processing. The switching element of an inverter 4 is turned on or turned off by the signal transmitted to a gate drive circuit 13. As a result, the drop of the forklift is prevented, and the start in the middle of a slope can be made by operating the accelerator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control for allowing an appropriate current to flow from an inverter to a three-phase induction motor so as not to descend when climbing in the middle of a slope, and particularly to an induction motor suitable for a battery forklift. Regarding the control device.

[0002]

2. Description of the Related Art Conventionally, as a control for preventing a descending slope when climbing in the middle of a slope without using a tachometer, Japanese Patent Publication No. 56-22
There is a 203 bulletin. This is for detecting a downhill even if it does not have a rotation sensor, is a downhill detection method suitable for a DC motor, and relates to a control circuit for preventing a downhill.

It is difficult to apply this to an induction motor that does not have a rotation sensor.

[0004]

When a battery forklift driven by an induction motor having no rotation sensor as a drive source climbs up in the middle of a slope, it is necessary to control so as not to descend.

[0005]

A switch signal that is activated when the brake pedal is released while the forward / reverse selector switch is turned on to immediately activate the inverter and supply current to the induction motor. The minimum current value is taken as the creep current (current at slow speed operation) on a flat road. When the accelerator is being operated, a current corresponding to the operation amount is passed.

The voltage frequency applied to the induction motor is increased to some extent to stabilize the control. Further, the current is intermittently applied and the increase in voltage is not suddenly changed.

It is also assumed that the mechanical switch such as a contactor has completed its operation when the forward / reverse selector switch is turned on.

[0008]

Since the mechanical switch is not used, the inverter can be operated in 50 milliseconds or less by the switch signal that operates when the brake pedal is released.

Even if the accelerator is not operated, the minimum current value flows, and therefore the vehicle does not descend immediately. If it is a steep slope, you can continue to stop or climb if you operate the accelerator during that time.

It is not necessary to make the applied voltage low because the low frequency is not used for controlling the motor restraint current. Further, the minimum current value can be changed by changing the time interval (cycle) in which the current is intermittently applied. It allows stable control.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIG.

FIG. 1 shows a block diagram of a control device according to the present invention.

The (+) power source line 2 and the (-) power source line 3 of the battery 1 are connected to the inverter 4. The terminal of the delta connection coil of the three-phase induction motor 5 is connected to the inverter 4, the terminal voltage line is connected to the filter circuit 7 of the input circuit 6, and the output line of the one-phase current sensor is also connected to the filter circuit 7. Connected.

The accelerator 8 is converted into an electric signal by an operation amount of an accelerator pedal or an accelerator lever and connected to the input circuit 6.

The forward / backward changeover switch 9 and the brake switch 10 are also connected to the input circuit 6. The signal processed by the input circuit 6 is applied to a control circuit 12 including a microcomputer 11 (hereinafter referred to as a microcomputer) and processed by a control algorithm. Then, the switching element of the inverter 4 is turned on and off by the signal transmitted to the gate drive circuit 13.

The protection circuit 15 determines whether the rotation direction according to the order of the three-phase voltage applied to the three-phase induction motor 5 and the rotation direction designated by the forward / reverse switching switch 9 are matched, or the three-phase induction motor 5 receives an overcurrent. Is to detect whether or not the current has flowed, and to protect the gate signal by blocking it, etc. It is a circuit that matches the interface of the microcomputer.

A commonly used power supply circuit 14 will be described with reference to FIG.

The (+) power supply line 2 is connected to the input of the three-terminal regulator 16 via the resistor R0. Capacitor C0
The capacitor C1 absorbs noise and surge voltage.
The output of the three-terminal regulator 16 becomes the power supply VC17 of the microcomputer 11 and peripheral circuits.

The field effect transistor FET1, the inductance L1, the diode D1, and the capacitor C2 constitute a step-down power supply circuit, and the voltage divided by the resistors R1 and R2 is connected to the A / D converter terminal of the microcomputer. Similarly, the field effect transistor FET2, the inductance L2, the diode D2, and the capacitor C3 constitute a (-) power supply circuit, and the positive voltage divided by the resistors R3 and R4 is A / D of the microcomputer.
(+) V18, (-) V1 connected to converter terminals
A constant voltage of 9 is used as the power supply for the current sensor.

The field effect transistor FET3 and the primary coil 21 of the insulating transformer 20 are connected in series to the (+) power source line 2 and the (-) power source line 3. Secondary coil 22, diode bridge 23, three-terminal regulator 24, resistor R
5, Zener diode ZD1, capacitors C4, C5
Constitute a gate power supply circuit 25.

The gate power supply circuit 26 and the gate power supply circuit 27 formed by using the same circuit element are used for the switching element connected to the (+) power supply line 2 of the inverter 4.

The tertiary coil 28 of the insulating transformer 20, the diode bridge 29, the resistor R6, the resistor R7, the resistor R8,
The gate power supply circuit composed of the Zener diode ZD2 and the capacitors C6 and C7 is a circuit used as the gate power supply of the switching element connected to the (−) power supply line 3 of the inverter 4.

The field effect transistors FET1, FET2, FET3 used in the above power supply circuit are from terminals having a PWM function of the microcomputer 11, and output voltage feedback is from AD1, AD2, AD3 to analog / digital conversion terminals. Connected. Therefore, the output voltage is controlled to a predetermined constant voltage.

FIG. 3 shows a circuit for detecting the voltage applied to the induction motor.

The battery forklift uses a motor for traveling and for lifting. The terminals U1, V1, W1 of the three-phase induction motor 5 are connected to the inverter 4, the terminals U2, V2, W2 of the three-phase induction motor 30 are connected to the inverter 31, and the terminal voltage line is composed of resistors R9, R10 and a capacitor C8. Is connected to the filter circuit 7. This signal is input to the microcomputer 11 via the input circuit 6.

The current sensor 32 and the current sensor 33 are connected to the microcomputer 11 by the circuit shown in FIG.

The absolute value circuit 34 makes a negative voltage positive and is composed of resistors R11, R12 and a capacitor C9 (the resistors R11, R12 and the capacitor C9 have the time constants shown in the filter circuit 7 of FIG. 3). Connected to filter circuit 7.

The polarity detection circuit 35 is the positive / negative of the current sensor 32.
It distinguishes negative voltages.

By detecting the voltage, it is possible to check whether the three phases are balanced or not based on the magnitude of the change. If the battery voltage is also detected, the neutral voltage can be detected, so that the malfunction of the switching element forming the arm of the inverter 4 can also be detected.

Sensorless vector control is possible by detecting the input voltage and current of the three-phase induction motor 5 and calculating from the characteristic constants of the motor to obtain the rotation speed.

Without a rotation sensor, it is difficult to detect a downhill.

Therefore, when the vehicle is stopped on the way uphill, the procedure is as shown in FIG. 5 so as not to go downhill. Immediately (within 50 milliseconds) the induction motor when the forward / reverse selector switch 9 is turned on (either of the switches is connected) and the brake switch 10 returns from the operating state to the original state (when the brake petal is released). Apply current to. When there is no accelerator operation amount or when the accelerator operation amount is minimum, electricity is supplied as shown in FIG.

(A) shows an enlarged view of the energization waveform, (b)
Indicates a state where electricity is actually applied. Processed by a control circuit that includes a microcomputer so that the frequency is several hertz, the beginning and end are small, and the middle is large, and the energization time (t) is zero seconds and the current flows intermittently (cycle T) to the motor. Then, the gate drive circuit applies the current to the inverter 4 to supply the motor current.

[0034]

Since the mechanical brake is released and the inverter is operated at the same time, the battery forklift is prevented from being lowered, and the accelerator can be operated to start the hill halfway.

[Brief description of drawings]

FIG. 1 is a block diagram of a control device according to the present invention.

FIG. 2 is a power supply circuit diagram used in FIG.

FIG. 3 is a voltage detection circuit diagram.

FIG. 4 is a current detection circuit diagram.

FIG. 5 is an explanatory diagram of operating conditions when climbing a slope.

6 is an operation waveform diagram of FIG.

[Explanation of symbols]

1 ... Battery, 2 ... (+) power supply line, 3 ... (-) power supply line,
4 ... Inverter, 5 ... Three-phase induction motor, 6 ... Input circuit,
7 ... Filter circuit, 8 ... Accelerator, 9 ... Forward / backward changeover switch, 10 ... Brake switch, 11 ... Microcomputer, 12
... control circuit, 13 ... gate drive circuit, 14 ... power supply circuit, 15 ... protection circuit.

Claims (1)

[Claims] 1. A battery, an inverter energized by a gate drive circuit, a three-phase induction motor, a control circuit including a microcomputer, an accelerator, a forward / reverse selector switch,
Three-phase induction in which the signals of the input circuit including the processing such as the brake switch, the power supply circuit, the circuit for detecting the three-phase voltage and the signal for detecting the one-phase current are applied from the filter circuit having the same filter characteristics to the control circuit In the motor drive circuit, a means for detecting the release of the brake depression, a means for detecting that the forward / reverse selector switch has been turned on, and a microcomputer for supplying a current intermittently to the motor at a frequency of several hertz with these signals. An induction motor control device comprising a control circuit including a control circuit and a circuit for applying a processed signal to a gate drive circuit.