JPS5826282B2 - Lifting control device for work equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lifting and lowering control device for a working machine in a tractor, and uses an actuating device interposed in a feedback mechanism to operate a control valve according to engine load fluctuations, thereby keeping the engine load approximately constant. It is something that can be controlled.

When plowing a field with a rotary or other working implement attached to the rear of the tractor body, the tractor body sinks in soft ground, which causes the implement to plow deeper and the engine speed to decrease. do.

Conventionally, the driver manually operated the control lever of the control valve and changed the plowing depth while judging the situation in order to recover the engine speed, but this operation differs greatly depending on individual differences. Furthermore, since it is difficult to judge the situation, especially for beginners, the engine may stall or the working machine may be raised too high, resulting in a significant drop in work efficiency.

The present invention eliminates such conventional drawbacks, and is characterized by being equipped with a hydraulic device that raises and lowers the work equipment by operating a control valve, and which operates the control valve in conjunction with the lifting and lowering operations of the work equipment. In a lift control device for a work machine equipped with a feedback mechanism to return to neutral, a load fluctuation detection device for detecting engine load fluctuation is provided, and the feedback mechanism includes a
An actuating device is provided to operate the control valve, and the actuating device is actuated in the upward movement direction of the control valve when the engine load increases based on the output of the load fluctuation detection device, and the actuating device is actuated when the engine speed returns to a predetermined engine speed. The point is that a control means is provided to return the amount by that amount.

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.
In the figures and FIG. 2, reference numeral 1 denotes a mission case that constitutes a part of the tractor body, and a hydraulic device 2 for lifting and lowering the working machine is mounted at the rear of the mission case.

The hydraulic system 2 includes a cylinder body 3 fixed to the mission case 1 in the form of a lid, and a cylinder liner 4 held by the cylinder body 3.
, a piston fitted inside the liner 4 so as to be slidable in the axial direction, and a piston rod 5, the piston rod 5 being connected to a hydraulic arm 7 fixed to a hydraulic arm shaft 6,
The hydraulic arm shaft 6 is rotatably supported by the left and right side walls of the cylinder body 3 about its axis, and lift arms 8 are fixed to the left and right projecting ends of the hydraulic arm shaft 6, respectively.

Reference numeral 9 denotes a control valve for controlling the hydraulic system 2, and the spool 1 is attached to the inner lower side of the cylinder body 3, is slidable in the front and back direction, and is biased in the downward direction (arrow a) by an elastic body.
has 0.

Reference numeral 11 denotes a control lever shaft, which extends through one side wall of the cylinder body 3 and is rotatably supported around its axis parallel to the hydraulic arm shaft 6. A control lever 12 is attached to the outer end of the shaft, and a control lever 12 is attached to the inner end of the control lever shaft. An eccentric pin 14 is attached to the end via an arm 13 in parallel to the control lever shaft 11.

A spool lever 15 that contacts the rear end of the spool 10 is vertically mounted on the eccentric pin 14 so as to be able to swing relative to the spool lever 15 .

Reference numeral 16 denotes a feedback mechanism that returns the control valve 9 to neutral in conjunction with the lifting and lowering movements of the working machine, and is composed of a feedback arm 17, a feedback rod 18, a feedback lever 19, a lever shaft 20, a feedback pin 21, and the like.

The feedback arm 17 is fixedly fixed to the outer end of the hydraulic arm shaft 6 so as to be integrally rotatable, and a pivot pin 22 rotatable around an axis parallel to the hydraulic arm shaft 6 is supported at its free end. The feedback rod 18 is connected to this pivot pin 22.
It is fitted in such a way that it can only rotate freely.

The feedback rod 18 also has a threaded portion 23, which is threaded into a threaded hole of an adjustment nut 24 rotatably supported by the free end of the feedback lever 19.

The lever shaft 20 is disposed on the same axis as the control lever shaft 11 and facing the control lever shaft 11, and is rotatably supported by the other side wall of the cylinder body 3, and the feedback lever is attached to the outer end of the lever shaft 20. 19, and an arm 25 at the inner end.
Feedback pins 21 are fixedly connected to each other via the respective feedback pins 21 .

Feedback pin 21 connects eccentric pin 14 and spool 10
The spool lever 15 is configured to abut against the spool lever 15 from behind.

26 is a bevel gear fixed to the rear end of the feedback rod 18.

Reference numeral 27 denotes a motor mounting base that can rotate integrally with the rotation pin 22, and a reversible motor (actuating device) 28 is mounted on this.

The reversible motor 28 is for driving the feedback rod 18 in forward and reverse directions, and a bevel gear 30 fixed to its output shaft 29 meshes with the bevel gear 26 .

In FIG. 3, 31 is a load fluctuation detection device for detecting load fluctuation of the engine mounted on the tractor body,
It is equipped with a rotation speed setter 32, a rotation speed detector 33, and a comparator 34.
3 detects a decrease in engine speed as a voltage signal.

The comparator 34 subtracts the rotation speed detection value B detected by the rotation speed detector 33 from the rotation speed setting value A set in the rotation speed setting device 32, and detects the load fluctuation at that time. .

35 is a load fluctuation discriminator, which includes a first discriminator 36 that discriminates, for example, the range from the set rotation speed to 200 rpm;
Second discrimination section 37 that discriminates the range of 200 to 300 rpm
and a third discrimination section 38 that discriminates the range of 300 to 500 rpm.

Note that the load fluctuation discriminator 35 is configured so that the third discriminator 38, the second discriminator 37, and the first discriminator 36 operate in this order.

Reference numeral 39 designates a control circuit for the reversible motor 28, which includes a reversing circuit 40 that issues a reversal command based on the operation of the first discrimination unit 36, a stop circuit 41 that issues a stop command based on the operation of the second discrimination unit 37, and a third discrimination circuit 40 that provides a stop command based on the operation of the second discrimination unit 37. The normal rotation circuit 42 provides a normal rotation command according to the operation of the section 38.

43 is a pulse detector which generates a pulse signal by the rotation of the reversible motor 28.

44 is an addition/subtraction counter that adds and counts the pulse signal from the pulse detector 43 when the reversible motor 28 rotates in the normal direction, and subtracts and counts when the reversible motor 28 rotates in the reverse direction.

45 is a memory circuit that stores the count value of the addition/subtraction counter 44, and when the count value becomes zero, the stop circuit 4 is activated.
1.

46 is a reset circuit.

The control circuit 39 is provided with a forward rotation switch and a reverse rotation switch for manual operation.

Next, the operation of the above configuration will be explained.

FIG. 1 shows the working machine in a lowered state, but when lowering the working machine in this way, the control lever 12 in the raised position is operated by a predetermined angle in the direction of arrow b about the control lever shaft 1F.

Then, the position of the eccentric pin 14 supporting the spool lever 15 rotates in the direction indicated by the arrow b, and the spool 10 presses the spool lever 15 backward by the elastic force of the elastic body, and then moves downward in the direction indicated by the arrow a. The control valve 9 is switched to the drain side.

Therefore, the hydraulic oil in the cylinder liner 4 is compressed by the control valve 9 because the piston is pushed in the direction of contraction by the weight of the work equipment.
The working machine gradually descends.

At this time, the hydraulic arm 7 rotates in the direction of arrow C as the work machine descends, and rotates the feedback lever 19 around the lever shaft 20 in the direction of arrow D via the feedback arm 17 and feedback rod 18. Lever shaft 20
A feedback pin 21 provided around the arm 25 of
If the spool lever 15 is pushed back in the direction of the arrow d using the eccentric pin 14 as a fulcrum and the control lever 12 is fixed at a predetermined position, then when the work machine is lowered to the set position, the spool lever 15 is pushed back by the feedback pin 21. By pushing back the lever 15, the spool 10 moves in the direction of arrow C without resisting the elastic body, the control valve 9 is returned to the neutral position as shown in the figure, and the position of the working machine is controlled.

In plowing work under such conditions, if the engine is rotating at high speed according to the set value, the rotation speed setting value A set in the rotation speed setting device 32 and the rotation speed detector will be adjusted in conjunction with the accelerator lever. Since the detected rotational speed values B detected by 33 substantially match and the output of the comparator 34 is zero, the work implement is maintained at the predetermined plowing depth.

Next, when field conditions change due to localized soft ground, etc.
Since the tractor body and the working equipment sink and the plowing depth becomes deeper, the load on the engine increases and the engine speed decreases significantly.

As a result, the rotation speed detection value B of the rotation speed detector 33 becomes small, and the comparator 34 detects the rotation speed detection value B from the rotation speed setting value A.
Compare and subtract to detect load fluctuations.

The engine speed at this time is 300-500 rpm.
If the resistance has decreased to a certain extent, the third discriminator 38 of the load fluctuation discriminator 35 operates, and the forward rotation circuit 42 of the control circuit 39 issues a forward rotation command to the reversible motor 28. It starts rotating in the forward direction.

When the reversible motor 28 rotates forward, the bevel gear 30.26
The feedback rod 18 rotates normally through the threaded portion 2.
3 and the adjustment nut 24 are screwed together, the adjustment nut 24 is screwed in the direction of the arrow f, the feedback rod 18 is relatively extended, and the feedback lever 19 is moved in the direction of the arrow d.
It is rotated in the direction of the arrow.

That is, since the feedback arm 17 is in a fixed state, when the feedback rod 18 relatively extends, the feedback lever 19 rotates together with the lever shaft 20 in the direction of arrow d, and the feedback pin 21 presses the spool lever 15. Then, the spool 10 is moved in the direction of arrow C, and the control valve 9 is switched to the upward direction, and the extending operation of the hydraulic device 2 causes the working machine to rise via the lift arm 8, gradually reducing the load. To go.

At this time, the operation of the lift arm 8 causes the feedback arm 17 to rotate in the direction indicated by the g arrow, but the reversible motor 2
Since the control valve 8 rotates in the normal direction and the feedback rod 18 is relatively extended in accordance with the rising speed of the lift arm 8, the control valve 9 is held in the raised position.

On the other hand, when the reversible motor 28 starts to rotate forward, the pulse detector 43 operates, and the addition/subtraction counter 44 adds and counts the pulse signal, and the count value, that is, the amount of extension of the feedback rod 18, is sequentially stored in the memory circuit 45. do.

In this way, when the work equipment rises, the plowing depth becomes shallow, and the load is gradually reduced, the engine speed gradually recovers accordingly. The stop circuit 41 operates via the 2-discriminator 37, the reversible motor 28 stops rotating, and the feedback rod 18 is restricted to its extension length, so the lift arm 8 then rotates slightly in the direction of the g arrow. At this point, the spool lever 15 escapes to the neutral position, the control valve 9 returns to the neutral position, and the work implement is held at the current plowing depth position, waiting for the engine speed to recover.

The plowing depth of the working machine at this time is slightly shallower than the initially set plowing depth.

Therefore, since the engine load has been reduced, the engine speed will recover to about 0 to 20 rpm after a while, and the reversing circuit 40 will work via the first discrimination section 36, the reversible motor 28 will now reverse, and the feedback rod 18 is reversed, the feedback lever 19 is returned to the direction indicated by arrow b, the control valve 9 is switched to the downward direction, and the working machine is lowered.

At the same time, the addition/subtraction counter 44 sequentially subtracts pulse signals from the above-mentioned addition count value, and when the count value reaches zero, the feedback rod 18 has contracted to its original length, so the stop circuit 41 is activated and the reversible Motor 28 is stopped.

Then, after a slight delay, the control valve 9 is returned to the neutral position by the feedback mechanism 16, the working machine returns to the set plowing depth, and the predetermined plowing is thereafter performed.

Note that it is convenient to use a type with a built-in speed reducer as the reversible motor 2B.

Further, the structure that allows the feedback rod 18 to extend and contract may be other than the one shown in the figure.

As described in detail in the embodiments above, the present invention includes a hydraulic system that raises and lowers a working machine by operating a control valve, and a feedback mechanism that returns the control valve to neutral in conjunction with the lifting and lowering operations of the working machine. In the lift control device for work equipment, a load fluctuation detection device is provided to detect engine load fluctuations, and an actuation device for operating the control valve is provided in the feedback mechanism, and the output of the load fluctuation detection device is used to increase the engine load. At the same time, the actuating device is actuated in the upward movement direction of the control valve,
In addition, since it is equipped with a control means that returns the operating device by the amount of operation when the engine speed returns to the predetermined speed, the engine load can be automatically maintained at the optimum state at all times. Even when the soil sinks, the working depth of the work implement can be kept approximately constant, allowing efficient tilling work.

Furthermore, when the engine load increases, the actuating device is actuated in the upward direction of the control valve, and when the engine speed returns to the predetermined speed, the actuating device is returned by the amount of actuation.
When the engine speed recovers, the feedback mechanism (including the actuating device) returns to its pre-actuating state.Therefore, when the control valve is manually operated thereafter, the work equipment can be raised and lowered as before, and the same position as before. Control is also possible.

It is also easy to improve and implement the current position control device.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is a partially cutaway side view, FIG. 2 is a partially cutaway rear view, and FIG. 3 is a block diagram of a control system. 2... Hydraulic system, 8... Lift arm, 9... Control valve, 15... Spool lever, 16... Feedback mechanism, 17... Feedback arm, 18...
...Feedback rod, 19...Feedback lever, 21...Feedback pin, 23...Screw part, 24...Adjustment nut, 28...Reversible motor,
31... Load fluctuation detection device, 32... Rotation speed setting device, 33... Rotation speed detector, 34... Comparator, 35.
...Load fluctuation discriminator, 39...Control circuit, 43...
Pulse detector, 44... Addition/subtraction counter, 45...
memory circuit.

Claims (1)

[Claims] 1. In a lift control device for a work machine, which is equipped with a hydraulic device that raises and lowers the work machine by operating a control valve, and is equipped with a feedback mechanism that returns the control valve to neutral in conjunction with the lift operation of the work machine, engine load fluctuations are detected. a load fluctuation detection device is provided in the feedback mechanism, an actuation device for operating the control valve is provided in the feedback mechanism, and the actuation device is actuated in the direction of upward movement of the control valve when the engine load increases by the output of the load change detection device; A lifting and lowering control device for a work machine, characterized in that a control means is provided for returning the actuating device by the amount of operation when the engine speed returns to a predetermined engine speed.