JPH03239189A - Motor lock protective circuit - Google Patents

Abstract

PURPOSE:To protect an FET for driving a motor by voltage-converting a motor driving current by a resistor, comparing its voltage level by a comparator, deciding conduction stopping time to the motor by a first timer, and deciding conducting time to the motor by a second timer. CONSTITUTION:If a motor driving current is increased as compared with that at the normal time, a voltage value across a resistor 4 is supplied to a comparator 5. A first timer 6 which receives a detecting voltage level day, triggers the signal, and sends an ON signal to a second timer 7 for predetermined time. The timer 7 triggers the signal and sends an ON signal to a gate 8 for predetermined time. This ON signal is set to sufficiently short time as compared with the time of the timer 6. That is, an FET 3 is switched to suppress continuous flow of an overcurrent.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to drive control of a motor that drives a wiper of an automobile.

BACKGROUND OF THE INVENTION In recent years, automobiles have become increasingly computerized, as seen in electronic control by microcomputers.

However, as in wipers, electronic circuits and mechanical parts (motors) are used together, and the burden on the electronic circuits in driving the mechanical parts is heavy, and reliability has been required.

The conventional technology will be explained below.

An example of a conventional technique will be explained with reference to FIG.

In the figure, 1 is an interval switch (hereinafter referred to as INTSW), which starts the intermittent operation of a wiper (not shown). 2 is a motor that drives the wiper. 3 is a power FET (hereinafter referred to as FET), and I
Motor 2 depending on the 0N10 FF status of NT-3WI
to drive.

Next, the specific operations of the wiper will be explained regarding normal operation and abnormal operation when the wiper is locked due to snow or frost.

First, a wiper driving method in normal (normal) operation will be explained. Start the wiper ■Turn on NT-3WI and turn on the gate terminal of FET3. FET3
The gate signal A from INT-5WI supplies the motor drive TI current B to the source 1, the source of FET3, and the motor drive taB to the drain of FET3 to drive the wiper motor 2. Although not shown in Figure 3,
There is a contact within the motor that detects rotation, and the motor is configured to receive motor drive current B' from FET 3 only when the contact is in an ON state.

Next, an abnormal operation in which the wiper is locked will be explained.

First, in the same way as the normal operation above, start the wiper I NT-3W I ONL, turn on the gate terminal of FET3
T3 supplies motor drive current B by gate signal A from INT-3WI. Power supply ■8, source of FET3, motor drive current B' is passed through the drain of FET3 to drive wiper motor 2, but when the wiper is covered with snow. A state occurs in which the motor 2 is locked due to frost, etc., and the motor does not rotate even if the motor drive current B° is supplied to the motor 2. In this situation, the contacts that detect the rotation inside the motor 2 will not operate, and the F
A large current (approximately several tens of amperes flows during boat fishing) constantly flows through the ET3, and the FET3 is destroyed.

Problems to be Solved by the Invention As described above, the configuration in the conventional technology has had problems such as destruction of the FET 3 that drives the motor and abnormal heating of the motor 2 when the motor is locked.

The present invention solves the above-mentioned conventional problems, and is aimed at solving the above-mentioned conventional problem.
The purpose is to protect the current control means such as ET3 and reduce the burden on the motor 2.

Means for Solving the Problems To achieve this object, the present invention provides a motor, a current control means for controlling the drive current to the motor, and a resistor connected in series with these for converting the motor drive current value into a voltage level. a comparator that compares the voltage level with a reference voltage level; a first timer circuit that operates based on the comparison result of the comparator; and a second timer circuit that operates from the end of the first timer circuit. , a gate circuit gates the output of the second timer circuit and an interval switch signal supplied from the outside to drive and control the current control means.

Function: With this configuration, the motor drive current flowing through the motor is converted into voltage using the resistor. When the motor cannot rotate, the voltage level of the resistor is compared by a comparator, the first timer circuit determines the time to stop energizing the motor, and the second timer circuit determines the time to energize the motor. In this way, the motor is energized intermittently, thereby preventing damage to the motor and the like.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of a specific embodiment of the present invention. FIG. 2 shows signal timing for a specific embodiment of the present invention.

In Figure 1, 1 is an interval inch (hereinafter referred to as I
(referred to as NT-3W), and is used to operate a wiper (not shown) intermittently. 2 is a motor for driving the wiper. , 3 are FETs used as an example of current control means, which supply the motor drive current necessary for the motor 2 to drive the wiper. A resistor 4 converts the current flowing toward the FET 3 when the motor 2W4 is in operation into a voltage level. A comparator 5 compares the voltage level converted by the resistor 4 with its own reference voltage level (not shown), and drives the first timer circuit 6. This first timer circuit 6 sends out a signal for a predetermined time. 7
is a second timer circuit which sends out a predetermined time signal after the time set by the first timer circuit 6 has expired. 8 is a gate circuit in which 1NT-SWI is ONL and gates the time signal from the second timer circuit 7 to control FET 3 (
0N10FF of motor 2).

Next, specific operations will be explained with reference to FIGS. 1 and 2. Operation is normal (motor not locked LJi)
The condition is divided into abnormal condition (state in which the motor is locked and the wiper does not operate, in other words, the state in which the WINO < - is unable to move back and forth on the glass surface due to snow, frost, or foreign objects on the wiper). explain.

First, normal operation will be explained in detail.

Turn I NT-3W1 to O to operate the wiper intermittently.
N (contact connection). At this time, if the Wynomer is not affected by snow or frost and operates normally, the gate circuit 8 supplies the gate signal B to the gate terminal of the FET 3. FET3, which has received the gate signal B, has a power supply V m
The motor drive current C° supplied from the motor drive current C° is supplied to the motor 2 through a switching operation to rotate the motor 2. This motor rotation causes a mechanical part (not shown) to convert the rotation into reciprocating motion. to operate the wiper.

Next, abnormal operation will be explained.

IN to operate the wiper intermittently as it is open during normal operation.
T-3WI to ONL interval signal A to gate circuit 8
(state of timing chart 1-A in Figure 2),
The gate circuit 8, which has received the interval signal A, supplies the gate signal B for switching to the gate terminal of the FET 3.

FET3 receives the supply of this gate signal B.
Then, the motor drive current C'' supplied through the resistor 4 is switched to supply the motor drive current C'' to the motor 2 to rotate the motor 2.

However, since the wiper is locked, the motor 2 does not rotate. In such a locked state, the load on the motor 2 becomes large, and from ti Rv * the resistor 4 and FET 3
Further, a large current is supplied to the motor 2 via. Then, the motor drive current C flowing through the resistor 4 also increases compared to the normal state. As the current increases, the voltage across the resistor also increases. This voltage value (detected voltage level D) is supplied to the comparator 5.

First timer circuit 6 supplied with detection voltage level D
uses this signal as a trigger and turns ON for a predetermined period of time (timer 2
Starting signal F, condition of timing chart F in Figure 2 LIi)
is sent to the second timer circuit 7. The second timer circuit 7 uses this signal as a trigger to generate an ON signal (
The timer 2 output signal G (state shown in the timing chart G in FIG. 2) is sent to the gate circuit 8. This ON signal is the first
The time is set to be sufficiently shorter than the time of the timer circuit 6.

The gate circuit 8 gates this signal and the interval signal A from the INT-3WI, and then supplies the gate signal B (the state shown in the timing chart B in FIG. 2) to the gate terminal of the FET 3. FET3 supplied with gate signal B
is switched only for a short period of time set by the second timer circuit 7 to supply the motor drive current C'' to the motor 2 (In the state of timing chart C'' in Figure 2, the motor 2 operates only when it is ON) When the FET 3 switches, the resistor 4 supplies the detection voltage level D to the comparator H5 in the same manner as described above.At this time, the detection voltage level D
If it is below the reference level set value (not shown), the motor lock is released (state LQ in which foreign objects such as snow and frost have been removed by nature or people and the wiper drive can operate normally), and the first timer circuit is activated. 6 and the second timer circuit 7 do not operate, but if still in the locked state, the first timer circuit 6 and the second timer circuit 7
operates in the same manner as described above, switches FB and T3, supplies motor drive current C'''' to motor 2, and drives the motor. This operation is repeated until the motor lock is released. When the motor lock is released, as described above, the operation of the first timer circuit 6 and the second timer circuit 7 is stopped and normal operation is resumed. It works like this.

As described above, according to this embodiment, when the motor is locked, the FE
By switching T3, overcurrent can be reduced to FET3.
and the FET
3 and the motor 2 can be prevented from deterioration and destruction.

Effects of the Invention As described above, the present invention provides a current control means for supplying drive current to the motor by controlling the drive current to the motor when the wiper does not move due to snow or frost, so-called motor lock; It is possible to minimize the continuous overcurrent flowing into the motor that drives the wiper, thereby preventing their deterioration and destruction.

[Brief explanation of drawings]

FIG. 1 is a diagram of one embodiment of the present invention. FIG. 2 is a timing chart diagram of one embodiment of the present invention. FIG. 3 is a conventional block diagram. l...INT-3W, 2...Motor,
3...FET, 4...Resistance, 5...
...Comparator, 6...First timer circuit, 7
...Second timer circuit, 8...Gate circuit, 9...Motor control section, IO...
・FET control section.

Claims (1)

[Claims] a current control means for controlling a motor and a drive current to the motor; a resistor connected in series with these for converting a motor drive current value into a voltage level; and a comparator for comparing the voltage level with a reference voltage level; a first timer circuit that operates based on the comparison result of the comparator; a second timer circuit that operates from the end of the first timer circuit; and an interval switch that is supplied from the output of the second timer circuit and an external source. A motor lock protection circuit comprising a gate circuit that gates a signal and controls the drive of the current control means.