JPH03271802A - Protective device for electric driving type actuator - Google Patents

Abstract

PURPOSE:To prevent the damage of electric parts at the time of short circuit of wiring by detecting a duty ratio of a pulse current, and stopping the current supply to an actuator, when a detection value becomes outside a set range. CONSTITUTION:A duty ratio detecting means A and a current stopping means B are provided as a control program stored in advance in a controller 31. In such a state, in the feedback control for maintaining a driving current of solenoids 18a, 20a in a correct value, its controlled duty ratio is detected, and when a measured duty ratio is within a set range, the feedback control is executed continuously. On the other hand, when it is judged that the measured duty ratio is outside a set range, an output signal to power transistors 32, 32 is switched forcibly to a turn-on state and the turn-off state is maintained until a main switch 43 is subjected to disconnecting operation. In such a way, the circuit protection at the time of short circuit fault can be executed without adding an exclusive overcurrent protective device.

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. A current detection means for detecting the average current value of the supplied pulse current is provided on the downstream side of the actuator in the current direction, and the detection result of this current detection means is fed back, and the current detection means is arranged so that the detected current matches the set current. The present invention relates to a protection device for an electrically driven actuator, which includes a control device that changes and controls the duty ratio of a pulse current within a set range to drive the actuator at an appropriate value.

[Conventional technology]

Conventionally, the drive structure of the above-mentioned electrically driven actuator has been proposed, for example, by the present applicant (Japanese Patent Application No. 1-1839).
No. 14).

In other words, the configuration is such that a power transistor is controlled on/off based on a signal from a control device to supply current to a solenoid of an electromagnetic proportional valve as an actuator.
It is configured to detect the voltage value across a load current detection resistor installed on the lower current side of the solenoid, and feed back the detection signal to the control device to maintain the drive current at an appropriate value. The electric circuit parts such as the power transistor and the like were placed in a control box located near the operator's hand, and the solenoid was placed near the hydraulic piping and away from the control box.

C Problems to be Solved by the Invention] In the above conventional structure, it is necessary to electrically connect the control box and the actuator via a connection cord, and this connection cord is susceptible to aging, vibration of the aircraft, or external objects. There is a risk that the coating may be damaged due to contact with the fuselage, resulting in a short circuit between the wire and the fuselage, but if a short circuit failure occurs midway, only a small amount of current will flow through the current detection resistor. As a result, the feedback signal to the control device becomes small, and the control operates to increase the output current, increasing the risk that excessive current will flow through the power transistor or solenoid and damage them.

An object of the present invention is to provide a protection device for an electrically driven actuator that can prevent damage to electrical components even if a short-circuit failure occurs during wiring.

[Means to solve the problem]

A characteristic configuration of the present invention is that in the protection device for an electrically driven actuator described at the beginning, there is provided a duty ratio detection means for detecting a duty ratio of the pulse current, and a detection value of the duty ratio detection means is outside a set range. The actuator is further provided with current stopping means for stopping the current supply to the actuator when the actuator is detected.

[For production]

If a short-circuit failure occurs during the wiring from the control device to the actuator, only a small amount of current will flow through the current detection means, so the control device will control the duty ratio of the drive current to the large side. Even if the duty ratio is increased beyond that, a corresponding current will not flow through the current detection means, so the control device tries to further increase the duty ratio, that is, the average drive current, but the duty ratio detection means When such a state is detected, the current stopping means stops the current supply to the actuator.

〔Effect of the invention〕

Therefore, according to the present invention, by effectively utilizing the existing duty ratio changing configuration provided for changing and controlling the drive current for the actuator, wiring shorts can be easily improved without using a special overcurrent protection device or the like. We were able to obtain something that can prevent damage to electrical parts at times.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 5, an engine (4) is placed at the front of a vehicle body (3) equipped with front and rear wheels (1) and (2), and
A transmission case (5) is arranged at the rear of the vehicle body (3), and a pair of left and right lift arms (6) are mounted on the upper part of this transmission case (5).
, and a lift cylinder (7) for driving the lift arm (6) up and down, and a driver's seat (9) is provided between the left and right rear fenders (8) at a position above the lift cylinder (7). Configure the tractor.

A rotary tiller (11) (an example of a ground work device) is detachably connected to the rear end of this agricultural tractor via a two-point link mechanism (10).
) and the lift arm (6) are supported in a suspended state by a pair of left and right lift rods (12), this rotary tiller (11) is raised and lowered by the drive of the lift cylinder (7), and further, A double-acting rolling cylinder (13) is interposed in one of the pair of lift rods (12), so that this rotary tiller (11) is driven by the rolling cylinder (13) to rotate the longitudinal axis ( X)
It is configured to operate by rolling around.

The hydraulic system for performing this lifting and lowering operation and rolling operation is shown in FIG.
), a flow priority valve (15) for controlling the flow rate, and a controlled flow from the flow priority valve (15) to the rolling cylinder (
13), an electromagnetic proportional control as an actuator that supplies surplus flow from the flow priority valve (15) to the lift cylinder (7), or discharges hydraulic oil from the lift cylinder (7). The control valves (V) each include a first valve (17) for controlling the rise, and a second valve (17) for controlling the pilot pressure that opens and closes the first valve (17). I8), a third valve (19) for descending control, a fourth valve (20) for pilot pressure control that opens and closes this third valve (19), and a relief valve (21). When controlling the device (11) to the rising side, a current is supplied to the solenoid (18a) of the second valve (18), and by adjusting this current value, the pilot pressure corresponds to this current value. As a result, the opening degree of the valve is proportional to this current value, and when controlling the rotary tiller (11) to the downward side, the solenoid ( By adjusting the current value of the current supplied to 20a), the opening degree of the valve can be obtained in proportion to this current value.

Further, in this agricultural tractor, the rotary tilling device (1
1) to a predetermined level with respect to the ground (G), position control to raise and lower the plow to a predetermined level with the vehicle body (3) as a reference, and longitudinal axis (X).
) three types of automatic control including rolling control that sets the tilting posture around the surroundings, and forced lift control that takes priority over these three types of automatic control and raises the rotary tiller (11) to a predetermined level relative to the vehicle body. A control device is provided to perform the following.

Of this control device, a system that performs automatic plowing depth control, position control, and forced lift control is configured as shown in FIG. 1, and in this configuration, as shown in FIG.
) The first potentiometer (24) detects the setting position of the tilling depth setting dial (23) of the control box (22) provided in Rotary tilling device (1
The second potentiometer (2) detects the ground level of (1)
5) constitutes a setting system and a feedback system for automatic plowing depth control, and a third potentiometer ( 27) and a fourth potentiometer (28) that detects the level of the rotary tiller (11) relative to the vehicle body from the amount of swing of the lift arm (6), and a position control setting system and feedback system are configured. , a lift switch (29) for performing forced lift control on the steering handle post (35) is provided.

In addition, in this forced rise control, the fourth potentiometer (
28).

The connection point of the electric cord (36) connected to the second potentiometer (25) with the vehicle body (3) is a connector (37) on the vehicle body (3) side, as shown in FIG. A permanent magnet piece (39) is provided on the joint surface of the cord (36).
) The iron piece (40) is attached to the joint surface of the connecting tool (38), and the structure is such that the contact points (41) and (42) are maintained connected by their adsorption force, and the tilling device (11) is disconnected. The structure is such that when the vehicle body (3) is started in this state, the electric cord (36) will not be accidentally torn off.

Also, the signals from the four potentiometers mentioned above are A/
Via a D-converter (30), the signal is input to a control device (31) equipped with a microprocessor (not shown), and the signal from the lift switch (29) is directly input to the control device (31). The control device (31) outputs an intermittent pulse signal to drive the power transistors (32), (32), so that the intermittent pulse current flows into the solenoid (18a).
), (20a), and further this solenoid (
A resistor (R) serving as a current detection means for converting the current value of the current supplied to 18a), (20a) into a voltage value is connected to the path (33) from the solenoid (18a), (20a).
The voltage value thus converted is fed back to the control device (31) via a feedback path (34) and an A/D converter (30).

The control device also controls the solenoid (18a) by adjusting the duty cycle of the intermittent signal.

(20a) by adjusting the current value of the current supplied to
It is configured to adjust the opening degree of the control valve (V).

In addition, the electric circuit part mentioned above is connected to the control box (2).
2) located within the solenoid (18a).

(20a) is arranged near the lift cylinder (7).

Then, the duty ratio detection means (A) detects the duty ratio of the driving pulse current of the solenoids (18a) and (20a), and detects that the detected value of this duty ratio detection means (A) is outside the set range. Then, the solenoid (
18a) and (20a). To be more specific, the duty ratio detecting means (A) and the current stopping means (B) are provided as a control program stored in advance in the control device (31), and FIG. 2 shows a control flowchart thereof.

In the feedback control that maintains the driving current of the solenoids (18a) and (20a) at appropriate values based on the feedback signal as described above, the controlled duty ratio is detected (step S1), and the detected actual duty ratio is It is determined whether (D,) is within the setting range in normal control, that is, the range from the minimum setting duty ratio (D) to the maximum setting duty ratio (D2) (step S2). Then, the actually measured duty ratio (Du
) is within the set range, the feedback control as described above is continued. Actual duty ratio (D,
) is outside the setting range, the output signals for the power transistors (32), (32) are forcibly switched to the off state (step S3), and the above-mentioned state is switched off until the main switch (43) is turned off. The off state is maintained (step S4).

In this way, by effectively utilizing the duty ratio changing configuration originally used to control the drive current, the control device (31)
This can be achieved by simply changing the control program for the microprocessor in the system, and circuit protection in the event of a short-circuit failure can be achieved without adding a dedicated overcurrent protection device.

The present invention can be applied to various actuators such as electric cylinders and electric motors in place of the electromagnetic proportional control valve (V).

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 control flowchart, Fig. 3 is a hydraulic circuit diagram, and Fig. 4 is a wiring cord connection section. FIG. 5 is an overall side view of the agricultural tractor. (3I)...Control device, (A)...Duty ratio detection means, (B)...Current stop means, (R)...Current detection means, (V)...
・Actuator.

Claims (1)

[Claims] A current detection means (R) for detecting the average current value of the pulse current supplied to the electrically driven actuator (V) is provided on the downstream side of the actuator (V) in the current direction, and the detection result of this current detection means (R) is provided. is fed back and the duty ratio of the pulse current is changed and controlled within a set range so that the detected current and the set current match, and the control device (31) drives the actuator (V) at an appropriate value.
A protection device for an electrically driven actuator comprising: a duty ratio detection means (A) for detecting the duty ratio of the pulse current; and a duty ratio detection means (A) for detecting the duty ratio of the pulse current.
A protection device for an electrically driven actuator, comprising current stopping means (B) for stopping the current supply to the actuator (V) when it is detected that the detected value in A) is outside the set range.