JPH03271801A - Protection device for electrically driven actuators - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a protection device for an electrically driven actuator such as an electromagnetic hydraulic control valve that is installed in, for example, an agricultural tractor. A control device is provided with a current detection means for detecting a supplied current value on a downstream side of the actuator in the current direction, and changes and controls a drive current for the actuator so that the detected value by the current detection means matches a set value. The present invention relates to a protection device for an electrically driven actuator.

[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.

[Problem 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 the coating of this connection cord may be damaged due to aging, vibration of the aircraft, contact with external objects, etc. Although there is a possibility that the wiring may be short-circuited with the aircraft body, if such a short-circuit failure occurs midway, only a small amount of current will flow to 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]

The characteristic configuration of the present invention is that, in the protection device for an electrically driven actuator described at the beginning, after a predetermined time has elapsed from the start of driving of the actuator, it is detected that the detected value by the current detection means is equal to or less than a predetermined value. Then, the actuator is provided with current stopping means for stopping the current supply to the actuator.

[For production]

If a wiring short circuit occurs between the control device and the actuator, most of the drive current will pass through the short circuit, so the current detection means will normally detect a current that is significantly lower than the current value in the control area. When the current flow becomes less than a predetermined value, the current stop means determines this and stops the current supply.

Furthermore, since the current value detected by the current stop means is determined after a predetermined period of time has elapsed from the start of the drive, even if there is a delay in the rise of the current to the actuator at the start of the drive, the current can be stopped immediately after the start of the drive as described above. There is no inconvenience that the operation is executed.

〔Effect of the invention〕

As a result, if a short-circuit failure occurs during the connection wiring to the actuator, the drive current is automatically stopped, preventing excessive current from continuing to flow and preventing damage to the actuator and other electrical circuit components. This can be prevented. Furthermore, in order to maintain the drive current at an appropriate value, the existing current detection means is effectively used, so that the structure does not become significantly complicated.

Furthermore, this type of actuator is generally an inductive load, which can reliably prevent malfunctions due to delays in current rise during startup, and ensure that the correct current value can always be determined. .

〔Example〕

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

As shown in Figure 6, an engine (4) is placed at the front of a car body (3) equipped with front and rear wheels (1) and (2), and a transmission case (5) is placed at the rear of the car body (3). A pair of left and right lift arms (6) are mounted on the top of the transmission case (5).
A lift cylinder (7) is provided to drive 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 connected to the rear end of this agricultural tractor via a two-point link mechanism (10), and the two-point link mechanism (10) and the lift arm (6) and a pair of left and right lift rods (12)
By supporting the rotary tiller (11) in a suspended state, the rotary tiller (11) is moved up and down by the drive of the lift cylinder (7), and furthermore, one of the pair of lift rods (12) is equipped with a double-acting rolling cylinder. (13), the rotary tiller (11) is configured to roll around the longitudinal axis (X) by driving the rolling cylinder (13).

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). 18), 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 Rokuri 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. , control handle position) (38) is provided with a lift switch (29) for performing forced lift control.

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

As shown in FIG.
) is equipped with a rotary backup switch (3
5) and a lift arm upper limit setting dial (36) are arranged side by side. The backup switch (35) is configured to forcibly raise the tilling device (11) to the upper limit position set by the setting dial (36) when the aircraft is set in reverse, and to release it. This is for switching to . .

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 configured to be fed back to the control device (31) via the feedback path (34) and the A/D converter (30), respectively.

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, after a predetermined time has elapsed from the start of driving the solenoids (18a), (20a), when it is detected that the detection value by the resistor (R) is less than or equal to a predetermined value, the solenoid (18a), (20a) ) is provided with current stopping means (A) for stopping the current supply to. In other words, the solenoid (18a) at the start of driving,
As shown in Fig. 2, the current flowing through (20a) does not reach the predetermined average current that follows the drive signal from the power transistors (32) and (32) due to the rise delay caused by the inductance immediately after the start of driving, but several tens of A predetermined steady-state value is reached after milliseconds. Therefore, the determination of the current value as described above is performed after a predetermined time (tl) of approximately several tens of milliseconds has elapsed from the start-up time (To) to prevent measurement errors in transient conditions. To be more specific, the current stopping means (A) is provided as a program stored in advance in the control device (31), and a flowchart thereof is shown in FIG. First, the solenoid (18a)
, When the drive for (20a) is started, it is determined whether a predetermined time (tl) has elapsed from the start point (step S,), and when the predetermined time (tl) has elapsed, the detection from the resistor (R) is performed. The value (vR) is read (step 32). Next, it is determined whether the detected value (VR) is smaller than the predetermined value (v, h) below the steady operation level (step S3), and the detected value (VR) is smaller than the predetermined value (vt
h) If the above is the case, the feedback automatic control as described above is executed. If the detected value (VR) is smaller than the predetermined value (v, h), the power transistor (3
2), the drive signal output for (32) is forcibly switched off (step 34), and the main switch (37) is turned off (step 34).
) remains off until it is turned off (step S
,).

With this configuration, the control box (22)
Even if a short-circuit failure occurs with the aircraft due to breakage of the insulation during the connection wiring from the to the solenoids (18a) and (20a), the current detection value (VR) will become extremely small, resulting in the current supply being interrupted. Since the operation is stopped, damage to the power transistors (32) and (32) can be prevented.

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 timing chart, Fig. 3 is a control flow chart, Fig. 4 is a hydraulic circuit diagram, and Fig. 4 is a hydraulic circuit diagram. FIG. 5 is a perspective view of the lift switch, and FIG. 6 is an overall side view of the agricultural tractor. (31)...Control device, (A)...Current stop means, (R)...Current detection means, (V)
...actuator.

Claims (1)

[Claims] A current detection means (R) for detecting the supply current value to the electrically driven actuator (V) is connected to the actuator (V).
) on the downstream side in the current direction, and includes a control device (31) that changes and controls the drive current for the actuator (V) so that the detected value by the current detecting means (R) matches the set value. A protection device for an electrically driven actuator, when a detection value by the current detection means (R) is detected to be less than or equal to a predetermined value after a predetermined time has elapsed from the start of driving of the actuator (V), A protection device for an electrically driven actuator, comprising current stopping means (A) for stopping current supply to the actuator (V).