JPH03254104A - Device for protecting electrically-driven type actuator - Google Patents

Abstract

PURPOSE:To prevent malfunction and damage of circuit parts due to eddy current by providing a means for turning on or off a power supply of an actuator accompanied by operation of a switch for controlling switching of the actuator. CONSTITUTION:A drive circuit 33 which supplies drive current to actuators 27 and 28 is constituted to be switched to a drive state and a non-drive state by operation of a switch 26. Also, a circuit switching means 38 is provided to switch the power supply current to a supply state and a stop state for the actuators 27 and 28 accompanied by switching operation of the switch 26. Therefore, when the switch 26 is set to OFF state, the circuit switching means 38 stops supply of the power supply current to the actuators 27 and 28. Thus, even if the drive circuit 33 results in conduction failure due to short-circuiting failure of connection wiring for the actuators 27 and 28 in reference to a machine body, no current can be supplied to the actuators, thus preventing malfunction of the actuators 27 and 28 regardless of conduction failure of a final drive part and preventing damage to circuit parts.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a protection device for an electrically driven actuator such as an electromagnetic hydraulic control valve installed in, for example, an agricultural tractor.

[Conventional technology]

As a drive structure for the above-mentioned actuator, for example, there is a structure previously filed by the present applicant (Japanese Patent Laid-Open No. 1183914). In other words, driving power is supplied to the actuator by directly supplying current from the power supply device via the power transistor. Further, the electric circuit portion was installed in a control box located near the operator's hand, and the actuator was installed at a location away from the control box near the hydraulic piping.

[Problem to be solved by the invention]

With the above conventional structure, no problems occur during normal operation, but for example, problems may occur in the wiring from the control box to the actuator due to vibration of the aircraft, contact with external objects, or aging. The coating may be damaged and cause a contact short circuit with the aircraft. If such a short circuit occurs, an overcurrent will flow through the power transistor, causing
The wiring within this power transistor may melt and remain in an on state. In such a case, problems arise, such as the electromagnetic solenoid operating regardless of the presence or absence of a control signal from the control device.

An object of the present invention is to prevent malfunction of the actuator and damage to circuit components even if there is a conduction failure in the final drive unit due to a short-circuit failure or the like as described above.

[Means to solve the problem]

A characteristic configuration of the present invention is that a drive circuit that supplies a drive current to an electrically driven actuator is controlled to be switched between a drive state and a non-drive state by a switching operation of a human operation switch, and The present invention is characterized in that a circuit opening/closing means is provided which can switch freely between a state in which power supply current is supplied to the actuator and a state in which supply is stopped in response to a switching operation.

[For production]

When the operation switch for changing the drive state of the actuator is set to the OFF state, the circuit opening/closing means stops supplying power supply current to the actuator, so the final output stage of the drive circuit will fail due to a short-circuit failure of the connecting wiring to the actuator, etc. Even if this happens, no current will be supplied to the actuator and no malfunction will occur. Further, even in normal operation, since the drive circuit is in a non-driving state when the operating switch is turned off, the final output stage is in an off state, no power supply current is required, and there is no problem in operation.

〔Effect of the invention〕

Therefore, according to the present invention, by making effective use of the operation switch required for switching control of the actuator and making reasonable improvements, malfunction can be prevented and damage to circuit components caused by overcurrent can be prevented. Now I can do it.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 3 shows a machine body travel transmission system for switching forward and backward movement of an agricultural tractor. A running latch (2) and an external clutch (3) are provided to which the power from the engine (1) is transmitted, and the power from the running latch (2) is transferred to a cylindrical input shaft (4) for the running system. The power from the external clutch (3) is also transmitted to a transmission shaft (6) fitted inside the input shaft (4) for driving an external power shaft (5).

As shown in the figure, a clutch case (8) is externally fitted and fixed to the input shaft (4) via a key (7), and
The output gear (9) is fitted externally in a reversed state, and the human power shaft (4)
) A human power gear (11) is externally fitted and fixed to a cylindrical intermediate shaft (lO) disposed coaxially with the shaft.

Moreover, an idle gear (12) and two gears (13), (14) are located between the output gear (9) and the input gear (11).
A gear transmission system for reverse movement is formed, and the clutch case (8) transfers power from the input shaft (4) to the output gear (9).
) and the input shaft (4).
) and a second hydraulic clutch (CL2) that directly transmits the power from the input gear (11) to the input gear (11).
15)..., (16)... and hydraulic piston (17)
.

(18), each hydraulic clutch (CL
Both I) and (CL2) can be set to a transmission state by supplying pressure oil.

Incidentally, the power from the intermediate shaft (10) is transmitted to the transmission device (1
A transmission system is formed in such a way that the power is transmitted to the wheels (20) via 9). In this transmission system for traveling, the first and second hydraulic clutches (CLI), (CL, 2) are designed to minimize the occurrence of shock during gear changes due to the operation of the second hydraulic clutch (CLI), (CL, 2).
, a second hydraulic clutch (CLI), (CL2).

That is, as shown in Fig. 1, the oil passages (23) and (24) that send pressure oil from the hydraulic pump (21) to the first and second hydraulic clutches (CL, ), (CL2), respectively, have electromagnetic proportional Pressure reducing valves (V1) and (Vl) are installed, and these two
The two electromagnetic proportional pressure reducing valves (Vl), (Vl) (an example of an actuator) are controlled by operation signals from a control device (25) that is equipped with a microprocessor (not shown). is the forward/forward setting changeover switch (
26) and a sensor (S) that detects the acceleration of the traveling system from the rotation of the wheels (20). ), (V2) hydraulic clutches (CLI)
), (Cl3) is controlled to have a gradual clutch pressure increase characteristic to perform automatic pressure increase control to soften the shock when the clutch is engaged.

FIG. 1 shows a control circuit diagram. Said changeover switch (
Based on the switching operation of 26), the control device (25) pulses the electromagnetic solenoids (27) and (28) of any of the electromagnetic proportional pressure reducing valves (V, ) and (V2) to achieve a preset pressure increase characteristic. Driven by current. At this time, the control range of the drive current is set in advance.

A current detection resistor (29) is connected to the lower drive current side of each electromagnetic solenoid (27) and (28).
A smoothing circuit (30) smoothes the voltage across this detection resistor (29).
The average value of the drive current is smoothed through the A/D converter (
31) is digitized and fed back to the control device (25), and the drive current is controlled so as to always maintain the drive current at an appropriate value. The electric circuit part is located in a control box (32) located near the operator's hand, and includes an electromagnetic solenoid (27).

(28) is provided at a location spaced apart from the control box (32).

Drive circuit (3) of each electromagnetic solenoid (27), (28)
3).

(33) has a power transistor (Try) in the final output stage.
) is provided, and this power transistor (Try) is controlled to be turned on or off based on a signal from the control device (25) as described above. The power transistor (Tr 1
) is connected to a detection transistor (Tr2) as short circuit detection means, and this transistor (Tr2) maintains an off state during normal operation, and the electromagnetic solenoids (27) and (28) are short-circuited. In the event of a failure, the transistor ('rrz) is turned on to detect a short circuit. In addition, a detection transistor (
A switching holding circuit ( 35
) is provided. To explain in detail, the transistor (Tr
2), the input transistor (Tr3
) is turned on, a low level signal is input to the latch circuit (36), and the output is switched from a high level signal to a low level signal. Accordingly, the AND circuit (37) outputs a low level signal, the power transistor (Tr 1) is turned off, and the current supply to the electromagnetic solenoids (27) and (28) is stopped. Note that an alarm lamp (R) is connected to the output side of the input transistor (Try).

A relay (as a circuit opening/closing means) that can freely switch between supplying power current to the electromagnetic solenoids (27) and (28) and stopping the supply according to the switching operation of the changeover switch (26). 38).

(38). In other words, the selector switch (26)
Connect the input common terminal of the relay (38) to the power supply path, and connect the switching terminal to the electromagnetic coil (38) of each relay (38).
38a) and (38a), respectively, and is also connected to the control device (25). In addition, fuses (h) and (h) are installed in the power supply path to prevent overcurrent.

With this configuration, the electromagnetic solenoids (27), (2
8), the drive current will not continue to flow even in the event of an on-failure of the power transistors (Tr r ) and (Tr + ), which will prevent unexpected aircraft runaway. No inconvenience will occur, and there is little risk of damage to circuit components.

[Another example]

As the circuit opening/closing means, relays (38), (38
) may also be used as the changeover switch (26).

Incidentally, although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of drawings]

The drawings show an embodiment of the protection device for an electrically driven actuator according to the present invention, in which FIG. 1 is a control circuit diagram, FIG. 2 is a hydraulic control system diagram, and FIG. 3 is a sectional view of a hydraulic clutch. (26)... Operation switch, (33)...
...Drive circuit, (38)...Circuit opening/closing means, (
V1), (V2)...actuator

Claims (1)

[Claims] A drive circuit (33) that supplies a drive current to the electrically driven actuators (V_1) and (V_2) is configured to be controlled to be switched between a drive state and a non-drive state by a switching operation of a human operation switch (26). When the operation switch (26) is switched, the actuator (V
_1), (V_2), the circuit opening/closing means (38
) protection device for electrically driven actuators.