JPH04347015A - Short circuit protection device for clutch control circuit - Google Patents

Abstract

PURPOSE:To improve the capacity of a clutch control circuit against short- circuiting, by using a field effect transistor as an output transistor for clutch control circuit and connecting a current detecting resistor to the output side thereof, and providing a constant voltage diode for suppressing the gate voltage of the field effect transistor element. CONSTITUTION:Instead of a conventional output transistor for clutch current control circuit, a field effect transistor 101 is used. The drain of the field effect transistor 101 is connected to an output terminal 21 and the source is grounded through a current detecting resistor 13. Clutch current return signals SF from the source of the field effect transistor 101 are applied to an input terminal of a current deviation detector 14. In addition, a constant voltage diode 102 is connected between the gate of the transistor 101 and the earth according to the polarity shown in the figure.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power fault protection device for a clutch control circuit which is intended to improve the power fault resistance of a clutch control output transistor.

0002

2. Description of the Related Art A known clutch control device of this type is disclosed in Japanese Unexamined Patent Publication No. 63-05732. FIG. 3 is a circuit diagram of this conventional clutch control device.

Reference numeral 1 in FIG. 3 indicates clutch current control means. In this clutch current control means 1, a clutch current calculation means 2 is provided. The clutch current calculation means 2 has an interface 23 and a computer 24.

[0004] This clutch current calculation means 2 has an interface 2 that provides driving control information SD and engine control information SE.
3 to the computer 24. From this travel control information SD and engine control information SE, the computer 24 of the clutch current calculation means 2 calculates a clutch current digital command signal SID, and the D/A
The signal is output to a (digital/analog) converter 25.

This D/A converter 25 inputs the clutch current digital command signal SID, outputs the clutch current analog command signal SIA as an analog signal, and applies it to the (+) input terminal of the current deviation detector 14. It looks like this. A clutch current feedback signal SF from one end of a current detection resistor 13 serving as current detection means is input to the (-) input terminal of the current deviation detector 14.

Thereby, the current deviation detector 14 detects the deviation between the clutch current analog command signal SIA and the clutch current feedback signal SF, and outputs a deviation signal. This deviation signal is applied to the base of the output transistor 11 via a PWN (pulse width modulation) modulator 15 and a resistor 51.

The emitter of the output transistor 11 is connected to a power supply line. The positive pole of the power supply 3 is connected to the power supply line, and the negative pole of the power supply 3 is grounded.

The collector of the output transistor 11 is grounded via a free wheel diode 16. The freewheeling diode 16 and the reverse excitation resistor 18 are connected in parallel via a reverse excitation power supply control transistor 60. Further, the collector of the output transistor 11 is connected to the output terminal 20.

A clutch 4 is connected between the output terminals 20 and 21. This clutch 4 has a slip ring 42
, 43 and a clutch coil 41. Clutch current is supplied to the clutch coil 41 via the slip rings 42 and 43.

Further, the clutch current calculation means 2 outputs a clutch release signal SO. This clutch release signal SO is connected to the base of the output transistor 12 via a base resistor 52.

The collector of the output transistor 12 is connected to the output terminal 21 and to the power supply via a quick-cut diode 17 for overvoltage prevention, and is connected to the reverse excitation power supply control transistor 61 via a reverse excitation resistor 19. connected to the collector. The emitter of the output transistor 12 is grounded via the current detection resistor 13. This current detection resistor 13 is a resistor for detecting clutch current.

A reverse excitation command signal is supplied from the clutch current calculation means 2 via resistors 62 and 63 to the respective bases of reverse excitation power supply control transistors 60 and 61. The emitter of this reverse excitation power supply control transistor 60 is grounded, and the reverse excitation power supply control transistor 61
The emitter of is connected to the power supply.

Next, the operation will be explained. A control device (not shown) calculates the vehicle speed, and this control device calculates the engine rotation speed, and travel control information SD is input to the clutch current calculation means 2 from these vehicle speed and engine rotation speed.

[0014] Next, the clutch current calculation means 2 inputs the engine control information SE. Based on the engine running control information SD and the engine control information SE, the clutch current calculation means 2 calculates clutch torque and outputs a clutch current digital command signal SID.

This clutch current digital command signal SI
D is input to the D/A converter 25, where it is converted to an analog signal, and the clutch analog command signal SIA is input to the (+) input terminal of the current deviation detector 14. A clutch current feedback signal SF is inputted from one end of the current detection resistor 13 to the (-) input terminal of the current deviation detector 14 . Therefore, the current deviation detector 14 obtains a deviation signal between the clutch current analog command signal SIA and the clutch electrical feedback signal SF.

This deviation signal is sent to the PWM modulator 15. As a result, the PWM modulator 15 converts the deviation signal into PWM
It is modulated and applied to the base of output transistor 11 via resistor 51. That is, the deviation signal is transmitted to the PWM modulator 15.
The output transistor 11 is controlled to be turned on or off according to the PWM modulated pulse width. Depending on whether the output transistor 11 is turned on or off, a clutch current flows through the clutch 4 from the output terminal 20 or is cut off. When the clutch 4 is connected, the reverse excitation power supply control transistors 60 and 61 are both turned off.

On the other hand, the output transistor 12 is controlled by the clutch current release signal SO output from the clutch current calculation means 2 in order to turn it on during normal clutch engagement.

In addition, when both transistors 11 and 12 are turned off, in order to supply a reverse excitation current flowing in a direction opposite to the illustrated clutch current IC when the clutch is released, the clutch current calculating means 2 A reverse excitation command signal is output and applied to reverse excitation power supply control transistors 60 and 61 via resistors 62 and 63, respectively.

As a result, the reverse excitation power supply control transistors 60 and 61 are turned on, and the reverse excitation current flows through the reverse excitation resistor 1.
A reverse excitation current is supplied from the power source to the electromagnetic clutch 4 through 8 and 19 in a direction opposite to the clutch current IC. Thereby, the clutch residual torque when the clutch is released can be corrected, the residual magnetic torque of the clutch torque is reduced, and dragging rotation of the clutch 4 is prevented. and,
The output transistors are protected by detecting the element currents of the output transistors 11 and 12 or by detecting an abnormality in the element voltage and feeding back a signal to the current calculation means 2.

[0020]

[Problems to be Solved by the Invention] Since the conventional clutch current control device is configured as described above, there is no current suppression function of the output transistor 12, and the C/U (clutch/
In the event of a short-circuit to the power supply (unit) terminal, etc., a short-circuit current determined by the element performance flows, leading to the destruction of the output transistor in a short period of time, making it difficult to guarantee system reliability.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to improve the short circuit resistance of the clutch control circuit by improving the short circuit resistance and the reliability of the output transistor for clutch control. The purpose is to obtain a protective device.

[0022]

[Means for Solving the Problems] A short circuit protection device for a clutch control circuit according to the present invention includes a field effect transistor used as an output transistor for clutch control and having a current detection resistor connected to the output side, and the field effect transistor. A constant voltage diode is provided to suppress the element gate voltage of a type transistor.

[0023]

[Operation] The drain current changes depending on the voltage between the source and gate of the field effect transistor in this invention, and the voltage between the source and gate is the value obtained by subtracting the voltage drop of the current detection resistor from the gate voltage. The voltage is suppressed by the constant voltage provided by the constant voltage diode and the short-circuit current flowing through the current detection resistor.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the power short circuit protection device for a clutch control circuit according to the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of one embodiment. In FIG. 1, parts that are the same as those in FIG. 3 are given the same reference numerals to avoid redundant explanation, and the parts that are different from FIG. 3 will be mainly described.

As is clear from comparing FIG. 1 with FIG. 3, in FIG. 1, a field effect transistor 101 is used in place of the clutch current control output transistor 12 of FIG. That is, field effect transistor 1
The drain of 01 is connected to the output terminal 21, and the source is grounded via the current detection resistor 13.

Furthermore, this field effect transistor 101
A clutch current feedback signal SF is applied from the source to the (-) input terminal of the current deviation detector 14. A constant voltage diode 102 is connected between the gate of the field effect transistor 101 and the ground with the polarity shown. The other configurations are the same as in FIG. 3.

Next, the operation will be explained. In explaining this operation, we will omit the explanation of the parts that perform the same operation as in FIG. I will now discuss the current suppression effect.

FIG. 2 is an explanatory diagram when the field effect transistor 101 is used as the output transistor. The gate-source voltage and drain current characteristics of the field effect transistor 101 are shown.

As is clear from FIG. 2, by increasing the gate-source voltage, the drain current increases. When the normally used current ISD is 10A, it is necessary to ensure at least the gate-source voltage VG-S to be 3V or higher.

This gate-source voltage VG-S is determined by the following (1
) is as follows. VG-S=VG-ID・RS...
(1)

As an example, if the resistance value RS of the current detection resistor 13 is 0.1Ω, the voltage regulator diode 10
2, by setting the gate voltage VG = 4V, the drain current of the field effect transistor 101 is 10V.
Power cannot be supplied above A.

As described above, in the event of a short-circuit to power supply, the current flowing through the current detection resistor 13 and the constant voltage diode 102 suppress the voltage between the gate and source of the field effect transistor 102, so that it can be used as an output transistor. Short circuit current of the field effect transistor 101 can be suppressed.

[0033]

As described above, according to the present invention, a field effect transistor is used as an output transistor for clutch control, and its gate-source voltage is controlled by a constant voltage diode and a current flowing through a current detection resistor. Since the voltage is suppressed, the gate-source voltage of the field effect transistor can be suppressed, and in turn, the short-circuit current can be suppressed.

Therefore, since the element breakdown withstand capacity is expressed as the product of the short-circuit power expressed as the maximum rated voltage and the maximum rated current and its cumulative time, the short-circuit current can be suppressed, and the element breakdown capacity can be improved. A highly reliable system can be constructed.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of a short circuit protection device for a clutch control circuit according to an embodiment of the present invention.

FIG. 2 is a drain current characteristic diagram of the field effect transistor in the embodiment of FIG. 1;

FIG. 3 is a circuit diagram showing the configuration of a conventional clutch control device.

[Explanation of symbols]

1 Clutch current control means 2 Clutch current calculation means 3 Power supply 4 Clutch 11 Output transistor 13 Current detection resistor 14 Current deviation detector 15 PWM modulator 16 Free wheel diode 17 Early cutting diode 18 Reverse excitation resistor 19 Reverse excitation resistor 20 Output terminal 21 Output Terminal 23 Interface circuit 24 Computer 25 D/A converter 60 Reverse excitation power supply control transistor 61 Reverse excitation power supply control transistor 101 Field effect transistor 102 Constant voltage diode

Claims (1)

[Claims] 1. Clutch current calculation means for outputting a clutch current command signal based on traveling control information and engine control information, and outputting a clutch release signal and a reverse excitation command signal when the clutch is released; a current deviation detector that measures the deviation from the current feedback signal;
a PWM modulator that outputs a pulse width modulation signal in response to the output of the current deviation detector; a first output transistor that operates in response to the pulse width modulation signal to control on/off of the clutch; A second output transistor is a field-effect transistor that supplies clutch current to the clutch together with the first output transistor, and detects the clutch current that flows when the second output transistor is turned on and converts the clutch current feedback signal into the clutch current. a current detection resistor for outputting to the deviation detector; means for supplying a reverse excitation current to the coil of the clutch in response to the reverse excitation command signal; A voltage-regulating diode and a clutch control circuit short circuit protection device.