JPH07117175B2 - Hydraulic lifting device for mobile farms - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydraulic lifting device for a mobile agricultural machine such as a tractor.

[Prior Art] In recent years, in a power agricultural machine such as a tractor, a hydraulic lifting device for lifting a working machine is controlled by a proportional solenoid valve.

[Problems to be Solved by the Invention] FIG. 5 is a graph showing the characteristics of an example of this kind of proportional solenoid valve. As is clear from the figure, a control current is applied to the solenoid of the proportional solenoid valve. However, the pressure oil does not start flowing until the amount of current exceeds a certain amount after the certain time t has elapsed. Further, when the current amount is increased and when the current amount is decreased, the flow rate of the pressure oil is different even if the current amount is the same. This characteristic is a result of the combined effect of the hysteresis phenomenon of the solenoid itself and the hysteresis phenomenon of the valve itself.

For example, if a proportional solenoid valve having the characteristics shown in FIG. 5 is used in a hydraulic device for raising and lowering a working machine of a tractor, pressure oil does not start flowing even if the position operating lever for operating the working machine is moved a little. The working machine remains stopped, but if it is moved a little further from this position (at the point A in the figure), pressure oil begins to flow, and the working apparatus suddenly starts operating. Therefore, the working machine lifting device equipped with such a proportional solenoid valve has a problem that it is difficult to finely adjust the vertical position of the working device.

Especially when finely adjusting the elevation height of a ground work machine such as a rotary tiller connected to a tractor, smoothly,
In addition, it is necessary to operate without shock, the operation speed at the beginning of movement is low, and it is necessary to increase gradually.

[Means for Solving the Problem] The present invention provides a device for driving a hydraulic lifting device in a stopped state, starting the driving as quickly as possible, and precisely controlling the operating speed of the hydraulic lifting device. To do.

Therefore, the present invention takes the following technical means.
That is, the work machine is connected to the machine body 2 through the link mechanism 3 so as to be lifted and lowered, and the hydraulic lifting mechanism 19 is operated so that the lift arm 17 is positioned at the position set by the position operation lever 24. In the hydraulic lifting device for agricultural machines, the hydraulic lifting mechanism 19 is not controlled by the ascending proportional solenoid valve 20 and the descending proportional solenoid valve 21, and the control is performed according to the deviation between the position set value and the actual detected value. By changing the pulse width of the pulse signal and flowing a current corresponding to the pulse width,
When driving the hydraulic lifting mechanism 19 from the non-driving state, at least one pulse of a fixed pulse signal having a width larger than the pulse signal width for obtaining a predetermined opening degree to the proportional solenoid valves 20 and 21 is output. A hydraulic lifting device for a mobile agricultural machine, which is characterized in that a control device 31 is provided.

[Operation] At the start of driving, the proportional solenoid valve is controlled so as to output one or more fixed pulse signals having a width larger than the width of the pulse signal with which the desired opening is obtained. As a result, a relatively large current is applied to the proportional solenoid valve, and as a result, the proportional solenoid valve can be actuated in the opening direction early against the inertia force of the spool of the proportional solenoid valve or the viscosity of the hydraulic oil. It is possible to prevent a delay in operation at the start of driving and obtain a smooth operation state.

[Embodiment] Next, an embodiment of the present invention will be described with reference to the drawings. First
FIG. 1 shows an embodiment of a power farming machine equipped with a hydraulic device according to the present invention, taking a tractor as an example. A three-point link device 3 is provided at the rear of the body 2 of the tractor 1, and a rotary tiller 5 is connected to the three-point link device 3.

The three-point link device 3 is provided with one top link 10 and a pair of left and right lower links 11, 11; the top link 10 is attached to the mast 13 of the rotary tiller 5, and the lower links 11, 11 are attached to the rotary tiller 5. Each is attached to the frame 14. The lower links 11, 11 are suspended on the hydraulic lift arm 17 of the tractor 1 by lift rods 16, 16 connected to the middle portions thereof.

The tractor 1 is a hydraulic lifting mechanism for vertically moving the three-point link device 3.
The lift arm 17 is provided with 19 and is configured to rotate the lift arm 17 up and down by the hydraulic pressure of the hydraulic lifting mechanism 19.

Vertical operation of the rotary tiller 5 is performed by a position operation lever 24 provided on a side portion of the cockpit 23. A lift arm angle sensor 27 for detecting the rotation angle of the lift arm 17 is provided at the base of the lift arm 17. As the control valve of the hydraulic lifting mechanism 19, a proportional solenoid valve whose pressure oil flow rate changes in proportion to the energization amount by a pulse is used. This proportional solenoid valve is a lifting proportional solenoid that drives the rotary tiller 5 up and down. It is composed of a valve 20 and a descending proportional solenoid valve 21. Lift arm 17 When raising and rotating, lift proportional solenoid valve 20
To release the hydraulic pressure to the extension side cylinder chamber of the drive hydraulic cylinder, and to lower the proportional solenoid valve 21.
And pressure oil is circulated in the tank.

Conversely, when lowering the lift arm 17, the raising proportional solenoid valve 20 is closed and the lowering proportional solenoid valve 21 is opened.

FIG. 2 is a block diagram showing the control mechanism of the hydraulic lifting mechanism 19. The detection signal a of the lift arm angle sensor 27 and the signal b indicating the setting position of the rotary tiller 5 by the position control lever 24 are A / D converters. It is transmitted to the control device including the CPU 31 via 30. Here, the angle of the lift arm 17 set by the position operation lever 24 and the actual rotation angle of the lift arm 17 detected by the angle sensor 27 are compared, and the ascending proportional solenoid valve 20 and the descending proportional solenoid valve are compared. Control signals c and d are output to 21.

Then, when an open signal is output to the valves 20 and 21 by a command from the CPU 31, the solenoids of the valves 20 and 21 are
After a large current for excitation is supplied for a fixed time, a control current having a pulse width that provides a desired opening for setting the lift arm angle to a set angle is supplied.

FIG. 4 is a waveform diagram of an example of the pulse signal for energizing the solenoid. In this figure, the ratio (duty ratio) of the energizing time (ON time) and the non-energizing time (OFF time) of the exciting current at the start of driving is shown. ) Is 9: 1 and is 5: 5 in the case of exciting current. The current value corresponding to the pulse width of these pulse signals is converted into a pulsating flow signal to excite the solenoid valve.

Further, the flow rate characteristic of the proportional solenoid valve is shown in FIG. 5, but the control flow rate is increased in proportion to the value of the current supplied to the solenoid. In this embodiment, the position determined by the position control lever 24 is used. Setting value,
The control current value, that is, the duty ratio of the pulse signal is determined by the deviation from the position detection value detected by the lift arm angle sensor 27.

Further, although four pulse signals are output at the start of driving in this embodiment, the width and number of the pulse signals may be set to an optimum one according to the characteristics of the actuator or the solenoid valve.

Next, the operation of the hydraulic lifting mechanism 19 will be described based on the flowchart of FIG.

First, it is determined from the set position of the position operation lever 24 and the detection value of the lift arm angle sensor 27 whether or not to keep the rotary tiller 5 at the current position (neutral). When the neutral command is issued, both proportional solenoid valves 20 and 21 are closed and the lift arm 17 is stopped. At this time, an excitation request is issued. If there is a command to move the lift arm 17 up and down, it is judged whether it is a command to move up or down, and if it is "moving up", whether there is a command to set the exciting current at the start of driving. To judge. If there is this command, the excitation energization time for energizing the solenoid with the excitation current is set. Specifically, at the beginning of driving, four pulse signals having a preset duty ratio (90%) are set to be output.

Then, if there is no request to set the exciting current, the control current corresponding to the deviation between the position set value and the position detected value is supplied.

In either case, the lift arm 17 rises, but at the start of the rise, the excitation current, which is a relatively large current, is applied for a predetermined time, and then the regular control current is applied, so that the pressure at the start of operation and thereafter The lift arm has almost the same oil flow rate.
17 moves up smoothly. The same applies to the case of "lowering", and in the above operation, the control performed on the raising proportional solenoid valve 20 is performed on the lowering proportional solenoid valve 21. When the soft arm 17 moves to the set position, the proportional solenoid valve becomes neutral,
At the same time, the excitation request flag is reset.

[Effects of the Invention] As described above, in the hydraulic lifting mechanism according to the present invention, when the output command is issued, the proportional solenoid valve is supplied with an exciting current larger than the normal control current, and then the position setting is performed. Since the control device that energizes the control current according to the deviation between the value and the position detection value is provided, the influence of the hysteresis phenomenon of the proportional solenoid valve and the solenoid can be eliminated, and the hydraulic lifting mechanism can be quickly operated. As a result of starting the driving, it is possible to move to the target position smoothly and accurately.

For this reason, for example, when connecting a ground work machine such as a rotary tiller to a tractor to adjust the working depth, the tilling section quickly reaches the working depth set by the operator. A device for precisely controlling the operating speed of the hydraulic lifting mechanism of a mobile agricultural machine was obtained.

[Brief description of drawings]

FIG. 1 is an overall side view, FIG. 2 is a control block diagram, FIG. 3 is a flowchart showing its operation, FIG. 4 is a waveform diagram, and FIG. 5 is a graph showing flow rate characteristics of a proportional solenoid valve. Explanation of code 1 …… Tractor 2 …… Aircraft 3 …… 3-point link device 5 …… Rotary tiller 17 …… Lift arm 19 …… Hydraulic lifting mechanism 20 …… Raising proportional solenoid valve 21 …… Descent proportional solenoid Valve 24 …… Position control lever 27 …… Lift arm angle sensor

Claims (1)

[Claims] 1. A mobile agricultural machine in which a working machine is movably connected and supported to a machine body via a link mechanism, and a hydraulic lifting mechanism is operated so that a lifting arm is positioned at a position set by a position operation lever. In the hydraulic lifting device, the hydraulic lifting mechanism is controlled by an ascending proportional solenoid valve and a descending proportional solenoid valve, and the control is performed by a pulse signal pulse depending on a deviation between a position set value and an actual detected value. While changing the width, a current corresponding to the pulse width is made to flow, and when the hydraulic lifting mechanism is driven from the non-driving state, the pulse signal of the pulse signal for obtaining a predetermined opening degree to the proportional solenoid valve A hydraulic lifting device for a mobile agricultural machine, which is provided with a control device that outputs at least one pulse of a fixed pulse signal having a width larger than the width.