JPH0343801A - Hydraulic pressure control circuit for work device - 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 provides an electromagnetic proportional control mechanism for controlling pressure oil to a hydraulic actuator for controlling the position of a working device, and
The present invention relates to a hydraulic control circuit for a working device equipped with a PWM drive device that pulse-drives the electromagnetic proportional control mechanism. Here, the electromagnetic proportional control mechanism is mainly composed of an electromagnetic proportional control valve, and the electromagnetic proportional control valve is a current-driven control valve that drives and controls the spool by electromagnetic force.
The pressure of the pressure oil can be finely adjusted by sensitively responding to changes in the current value, and furthermore, the operating speed of the hydraulic actuator can be smoothly switched from low speed to high speed.

[Conventional technology]

Since the electromagnetic proportional control valve described above is used, if the actual drive current value is larger or smaller than the expected value, it will affect the pressure control, so it is difficult to control the current. This is an important element.

However, since the oil temperature rises for a certain period after the start of controlled operation, the impedance of the electromagnetic coil changes, and the current value may not be output as expected. Therefore, in order to compensate for the current value, conventionally, in order to apply current feedback, either (1) a hard tank bottom using a current amplifier is used, or (
2) A configuration was adopted in which the current feedback value was calculated on the controller side equipped with a CPU.

[Problem to be solved by the invention]

When adopting the above configuration, (1) requires a current amplifier, which makes the configuration that much more complicated, and (2) requires high-speed calculation, which makes the equipment configuration expensive. There was a drawback.

The purpose of the present invention is to drive the electromagnetic proportional control mechanism using PWM, and while operating the electromagnetic proportional control mechanism as expected,
The aim is to provide equipment that can simplify the configuration and reduce the cost.

[Means to solve the problem]

The characteristic configuration according to the present invention is such that the smaller the actual drive current of the electromagnetic proportional control mechanism is due to the predetermined drive current necessary to control the pressure oil, the larger the drive gain for the electromagnetic proportional control mechanism in the PWM drive device. A correction control means is provided, and its effects are as follows.

[For production]

In other words, for example, as shown in Figure 4, the pulse width and current caused by PWM driving are in a relationship where the current increases from (I,) to (■1) as the pulse width (W2) increases (Wl). be. Therefore, as shown in Figure 3, the actual driving current value of the electromagnetic proportional control valve is sampled and compared with the desired current value (■1) for the electromagnetic proportional control valve necessary to drive the actuator at the desired speed. Suppose that the actual drive current value drops to (1,) due to an increase in the impedance of the electromagnetic coil f, then the duty ratio is made larger than (D+) and the current value (1,) becomes (■1). can be maintained.

〔Effect of the invention〕

Therefore, the equipment configuration is as shown in Figure 1.
A controller that does not require a current amplifier can be configured simply using software, and it also provides high functionality to the controller by correcting the current value by changing the drive gain instead of directly controlling the current value. There's no need to request it.

Moreover, if the drive gain is corrected intermittently as described in claim 2, there is no need to increase the control capacity of the controller, which can contribute to cost reduction.

〔Example〕

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

FIG. 2 shows a working device for raising and lowering an agricultural tractor, and
A hydraulic circuit for rolling the work equipment is shown, in which a hydraulic pump (2) is driven by an engine (1).
The pressure oil from the flow priority valve (3) is supplied to the flow priority valve (3), and the control flow from the flow priority valve (3) is passed through the electromagnetic control valve (4) to the rolling cylinder (5) as an actuator for controlling the position of the work equipment. The surplus flow from the flow priority valve (3) is supplied to the pilot pressure operated rise control valve (6) and the oil line (7).
) is supplied to the lift cylinder (8) as an actuator for controlling the position of the working equipment, and furthermore, this oil passage (7
) The system is configured such that a pilot pressure-operated lowering control valve (lO) is interposed in the drain oil passage (9) which is branched into the oil discharge path (9).

As shown in the figure, an electromagnetic proportional control valve (11) is provided to adjust the pilot pressure to the ascending control valve (6), and an electromagnetic proportional control valve (11) is provided to regulate the pilot pressure to the descending control valve (10). A control valve (12) is provided;
Combining the rise control valve (6) and the electromagnetic proportional control valve (11),
In addition, the descending control valve (10) and the electromagnetic proportional control valve (12) are collectively referred to as the electromagnetic proportional control mechanism (A), (A), and these are designed to increase their opening in proportion to the control current value. Operate.

As shown in FIG. 1, each electromagnetic proportional control valve (12),
(12) is driven and controlled by the following controller (13).

In other words, the tilling depth setting device (which sets the tilling depth of the working device)
15) and a controller (13) equipped with an A/D converter (17) and a CPU (18) that process the detected value from the cover sensor (1G) for the work device that detects the plowing depth position of the work device, The controller (13) is operated by intermittent pulse signals from the controller (13);
13) outputs an intermittent pulse signal at a constant cycle (S) of about 70-100 Hz, and drives the lift cylinder (8) by so-called PWM control, which adjusts the pulse width. The controller (13) is a PWM drive device.

When the power transistor (14) is driven by the intermittent pulse signal from this controller (13) as shown in FIGS. 4(A) and (C), the power transistor (14)
) and the electromagnetic proportional control mechanism (A), a solenoid (I
As shown in Fig. 4 (0) and (d), due to the action of IA), (12A) and the reactor component of this wiring (23),
Obtain control current in pulsating state.

Incidentally, corresponding to the pulse signal width (Wl) shown in FIG. 4(a), the control current of the current value (II) shown in FIG. 4(0) is obtained, and the control current shown in FIG. 4(c) is obtained. Corresponding to the pulse width (W2), a control current having a current value (I, ) shown in FIG. 4(0) is obtained.

Here, as shown in FIG. 3, as the oil temperature rises, the solenoid valve (11), (12) solenoid (IIA), (1
When the actual drive current decreases due to an increase in the impedance of the solenoid (IIA), (12A
) is increased from (Dl) to (Dt), the current value (I is corrected to (I2)), and the port openings of the solenoid valves (11) and (12) are adjusted to the desired opening. The desired pressure characteristics can be obtained at the same time.The duty ratio is shown in FIG.

Therefore, the elevating operation of the conventional device can be performed at an appropriate elevating and lowering speed.

This control method involves sampling the actual drive current of the electromagnetic valves (11) and (12) using the feedback circuit (19) in Figure 1 when turning at the edge of a ridge, etc., and determining the current value corresponding to the rise. If not, the controller (13) performs arithmetic processing to change the duty ratio and switches to a new duty ratio. In this case, the duty ratio should be corrected so that the lifting speed of the work equipment becomes a predetermined speed.
The lifting speed of the work equipment is also controlled.

In this way, the control method is to intermittently operate the solenoid valve (11).
Although the current value in (12) is sampled, a method of periodically sampling regardless of the ridge turning operation may be adopted.

The rise control valve (6) opens more widely as the pilot pressure from the solenoid valve (11) increases, and the fall control valve (6) opens more widely as the pilot pressure from the solenoid valve (11) increases.
10) operates to open the valve body more widely as the pilot pressure sent out via the electromagnetic pressure reducing valve (12) decreases.

As shown in Fig. 5, one electromagnetic proportional control valve (21 ) and forward/reverse switching solenoid valve (22
) to avoid installing electromagnetic proportional control valves (21) with the same characteristics in the forward and reverse circuits.

[Another example]

■ In addition to the embodiments described above, the present invention may also be configured such that the electromagnetic proportional control mechanism is configured using only an electromagnetic proportional pressure reducing valve, or
The PWM drive device may be configured with logic, and the hydraulic actuator to be controlled may be of any type.

(2) As a method of switching the drive gain of the electromagnetic proportional control mechanism (A), other than changing the duty ratio, other pulse width changing means may be used.

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 a hydraulic control circuit for a working device according to the present invention, in which FIG. 1 is a control circuit configuration diagram, FIG. 2 is a hydraulic circuit configuration diagram, and FIG. 3 is a correspondence between duty ratio and current value. FIG. 4 is a graph showing the relationship between the magnitude of the current and the pulse, and FIG. 5 is a configuration diagram showing the hydraulic structure of the forward/reverse switching device. (8)...Hydraulic actuator for controlling the position of working equipment, (13)...PWM drive device, (A)...
...Electromagnetic proportional control mechanism.

Claims (1)

[Claims] 1. A PWM drive device that is provided with an electromagnetic proportional control mechanism (A) that controls pressure oil for a hydraulic actuator (8) for controlling the position of a working device, and that pulse-drives the electromagnetic proportional control mechanism (A). (13) A hydraulic control circuit for a working device, wherein the PWM A hydraulic control circuit for a working device, which is provided with a correction control means for increasing a drive gain for the electromagnetic proportional control mechanism (A) in a drive device (13). 2. An electromagnetic proportional control mechanism (A) is provided to control the pressure oil to the hydraulic actuator (8) for controlling the working equipment position, and a PWM drive device (13) is provided to drive the electromagnetic proportional control mechanism (A) in pulses. A hydraulic control circuit for a working device, comprising a sampling mechanism that samples the actual drive current value of the electromagnetic proportional control mechanism (A) at predetermined intervals, and a sampling mechanism that samples the actual drive current value of the electromagnetic proportional control mechanism (A) at predetermined intervals. A hydraulic control circuit for a working device, which is provided with a correction means that increases a drive gain for the electromagnetic proportional control mechanism (A) as the drive current becomes smaller than a predetermined drive current necessary for controlling pressure oil.