JPS61261532A - Controller for vertical movement of boom of working machine - Google Patents

Abstract

PURPOSE:To vary the vertical moving speeds of the boom of a working machine by selectively opening an electromagnetic valve in a fully opening or half way opening manner by a switcher by a method in which switching elements are each connected to solenoids for raising and lowering the electromagnetic valve and the switcher is operated by drive signals given to each switching element. CONSTITUTION:A control circuit consists of solenoids 13, 14, 16, and 17 to control an electromagnetic valve, switchers 2-23, switching elements 26-29, a pulse generating circuit 31, and a switcher 35. When a boom is lowered for example, since the element 26 is on ON side when the switcher 35 is on the contact (b) side, the solenoid 14 is excited when the lowering switcher 21 is turned On and the electromagnetic valve is fully opened to the lowering side. When the switcher 35 is set to the contact(a) side, an intermittent pulse signal is sent out of the circuit 31, and on-off operations of the element 26 are repeated. When the lowering switcher 21 is turned ON, since the excitation and demagnetization of the solenoid 14 are repeated, the electromagnetic valve becomes to a halfway opened state on the lowering side, and the lowering of the boom is delayed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a boom elevation control device for a working machine.

(Prior Art) Some working machines, such as front loaders, which are mounted on a tractor and used, have a boom that can be raised and lowered by a boom cylinder, and the boom cylinder is controlled by an open/close type solenoid valve.

In this case, a switch linked to the operation of the control lever is closed, and a predetermined value of excitation current flows through the solenoid of the solenoid valve, and the spool of the solenoid valve reaches the fully open position when the excitation current flows through the solenoid. It is a working structure.

(Problems to be Solved by the Invention) Therefore, in the past, when a solenoid valve was used, it was very difficult to change the lifting and lowering speed of the boom, and there was a drawback that the boom always moved impulsively.

Also, when lowering the boom and installing a packet at the tip, it is better for operation to slow down the lowering speed halfway through and slowly lower the boom, but this type of control cannot be performed when using a solenoid valve. Ta.

The present invention was provided for the purpose of solving such conventional problems.

(Means for Solving the Problems) As a means for solving the above-mentioned problems, the present invention includes a boom that can be raised and lowered by a boom cylinder,
In a work machine in which a boom cylinder is controlled by an open/close type solenoid valve, a switch element for flowing an excitation current of a predetermined value is connected to the ascending solenoid and descending solenoid of the solenoid valve, respectively, and a continuous drive signal and a circuit that generates an intermittent drive signal, a changeover switch for selectively applying the re-drive signal from these circuits to each switch element, and a circuit that detects the lifting and lowering operation of the boom. A position detection switch element is provided for applying the intermittent drive signal to the lowering switch element when the boom is below a predetermined height.

(Function) In FIG. 1, when the changeover switch 35 is on the contact side, the switch element 27 is on, so when the lowering switch 21 is turned on, the solenoid 14 is energized and the solenoid valve 12 is on the lowering side. Fully open. When the changeover switch 35 is switched to the contact a side, the pulse generation circuit 31 generates an intermittent pulse signal, and the switch element 27 repeats on/off operations. Therefore, if the lowering switch 21 is turned on at this time, the solenoid 14 will repeat energization and demagnetization.
The solenoid valve 12 is in a half-open state on the descending side. That is, by operating the changeover switch 35, the solenoid valve 12 can be fully opened or half-opened, and the lifting speed of the boom 4 can be changed as desired.

When the boom 4 is lowered below a predetermined height position, the position detection switch 46 switches to the contact a side, and the switch element 27 repeats on/off operations. Therefore, in the same way as described above, the solenoid valve 12 is half-opened, and the descending speed of the boom 4 is slowed down.

(Example) The invention will now be described in detail with reference to the illustrated embodiments.

FIG. 2 shows a packet-type front loader for mounting on a tractor, where 1 is the tractor, 2 is the front wheel, and 3 is the rear wheel. Reference numeral 4 denotes a pair of left and right booms, which are attached to the tractor 1 via a mounting frame 5 and can be raised and lowered by a pair of left and right boom cylinders 6. A packet 7 is pivotally supported at the tip of the boom 4 and can be rotated by a pair of left and right packet cylinders 8.

FIG. 3 shows a hydraulic circuit, where 9 is a hydraulic pump, which is driven by an engine 10. 11 is a relief valve. 12
is an open/close type solenoid valve for the boom cylinder, and has a solenoid 13 for raising and a solenoid 14 for lowering. Reference numeral 15 denotes an open/close type electromagnetic valve for the packet cylinder, which has a dumping solenoid 16 and a scooping solenoid 17. A pressure switch 18 is connected to detect the oil pressure on the side of the hydraulic pump 9 rather than the solenoid valve 13. This pressure switch 13 is set to a set pressure pt that is higher than the pressure P1 of the nine hydraulic pumps when the boom 4 is raised in a no-load state. Reference numeral 19 denotes a control device for a hydraulic system for lifting and lowering the working machine.

Figure 1 shows the control circuit of the solenoid valve 12.15.
The ascending solenoid 13 of No. 2 is connected to the ascending switch 20 and the contact a of the pressure switch 18, and the descending solenoid 14 is connected to the descending switch 29 and the contact point a of the pressure switch 18. The pressure switch 18 closes a contact a when the detected oil pressure is higher than a set pressure P, and closes a contact A when the detected oil pressure is lower than a set pressure P2. A dump switch 22 is connected to the dump solenoid 16 of the solenoid valve 15, and a scoop switch 23 is connected to the scoop solenoid 17, respectively. Reference numeral 24 denotes a floating changeover switch, which has two contacts a and b for selectively selecting manual control by switches 20 and 21 and floating control by pressure switch 18.

Switch elements 26 to 29 are connected to each of the solenoids 13 to 17, respectively, for causing current of a predetermined value to flow therein. The switch elements 26 to 29 are composed of two Darlington-connected transistors Tr1. It is composed of Tr2. 30 is a transistor Tr of the switch elements 26 to 29;
, is a resistor for continuously applying a base drive signal to. 31 is a pulse generation circuit for applying an intermittent base drive signal to the transistor Trl via a resistor 32, and is configured such that the number of pulses can be adjusted by a variable resistor 33 and the pulse width can be adjusted by a variable resistor 34. There is.

The duty ratio of the pulse signal generated by this pulse generation circuit 31 is adjusted by resistors 33 and 34 as appropriate so that the spool can maintain a neutral position between fully closed and fully open, taking into account the delay in the operation of the solenoid valves 12 and 15. . Reference numeral 35 denotes a changeover switch for selecting a base drive signal to be applied to the transistor Tr+, and has a contact point connected to the resistor 30 and a contact point a connected to the resistor 32. A position detection switch 46 has a contact b1 connected between the changeover switch 35 and the switch element 27, and a contact a connected between the resistor 32 and the switch element 27, and has a position detection switch 46 when the boom 4 is below a predetermined height. The contact a is turned on when the voltage drops to , and the pulse signal from the pulse generating circuit 31 is applied to the switch element 27 . That is, as shown in FIG. 4, the position detection switch 46 is attached to the cylinder 46 side of the cylinder 47 and the rod 48 which are attached to the boom cylinder 6 and are telescopically fitted together. It is operated by a cam 49 at the tip of 48. In the embodiment, the cylinder body 47 is pivotally supported 51 on the boom 4 together with the piston rod 50, and the rod 48 is attached to the cylinder body 52.

5 and 6 show the control lever 36 and each switch 20,
21.22.23.24.35 is shown. The control lever 36 is attached to the top plate of the control box 37 via a spherical pivot 38 so as to be operable back and forth and left and right, and is resiliently supported at the center by a spring (not shown).

ing. The lower end of the control lever 36 is inserted through an elastic piece 41.42 into a ring-shaped operating body 39.40 provided in upper and lower stages. The actuating body 39,40 is supported slidably in all directions by a support member 43 in the control box 37, and the raising switch 20 is attached to the front of the actuating body 39.
, lower switch 21 at the rear, dump switch 22 at the left
, a scoop switch 23 is provided on the right side. Further, a changeover switch 24 is provided in front of the operating body 40. Then, the control lever 36 is moved around the pivot portion 38 to the first position.
When the tilting operation is performed in any direction forward, backward, left, or right up to the inclination angle of the step, the switch 20.21.22.2 is activated via the actuating body 39.
3 is turned on and the tilting operation is performed forward to the second stage tilt angle, the switch 24 is brought into contact via the actuating body 40, so that the switch 24 is switched to the contact point a. control lever 36
A changeover switch 35 is incorporated in the grip portion 44 at the upper end so as to be interlocked with a push button 45.
When the button is pressed, the contact is switched from contact A to contact A.

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

When excavating and loading earth and sand, operate the control lever 36 back and forth, left and right, and move the tractor 1 while positioning the boom 4 and packet 7 as shown by the solid lines in FIG. Move forward. When dirt enters the packet 7, the packet 7 is rotated upward by the contraction operation of the packet cylinder 8 to scoop it up, and the boom 4 is raised and transported by the expansion and contraction operation of the boom cylinder 6, and then the packet 7 to dump the earth and sand.

When the push button 45 of the control lever 36 is not pressed, the changeover switch 35 is on the contact side, so the transistors T of the switch elements 26 to 29 are connected from the resistor 30 through the contact.
A base drive signal is continuously applied to r+, and each of the switch elements 26 to 29 is continuously turned on.

Further, when the push button 45 of the control lever 36 is pressed, the changeover switch 35 changes from contact to contact a, and the pulse signal generated by the pulse generation circuit 31 is transmitted to the transistor Tr+ through the resistor 32 and contact a intermittently. Added as base drive signal. Therefore, each of the switches 26 to 29 repeats on/off operations in synchronization with the pulses generated by the pulse generating circuit 31.

Therefore, in normal cases, the control lever 36 is operated without pressing the push button 45. For example, if the control lever 36 is
When operated forward (arrow A) to the stage position, the actuating body 3
The lowering switch 21 is operated via the lowering switch 9, the lowering solenoid 14 is energized, the solenoid valve 12 is fully opened to the lowering side, the boom cylinder 6 is retracted, and the boom 4 is lowered. Moreover, if the control lever 30 is operated to the left (arrow B), the actuating body 3
9 activates the scoop switch 23, the scoop solenoid 17 is energized, the solenoid valve 15 is fully opened to the scoop side, the packet cylinder 8 is contracted, and the packet 7 is rotated upward. If the control lever 36 is operated rearward (arrow C), the boom 4 will similarly rise, and if operated rightward (arrow D), the packet 7 will be dumped downward.

During the lowering movement of the boom 4, the pushbutton 4 of the control lever 36
When 5 is pressed, the selector switch 35 switches to the contact a side,
Since the switch element 27 repeats on-off operations, an excitation current of a predetermined value flows intermittently through the lowering solenoid 14 as shown in FIG. 7A. For this reason, the lowering solenoid 14 repeats energization and demagnetization, and due to the delay in operation at that time, the spool maintains the half-open position as shown in FIG. The operating speed of the boom cylinder 6 is reduced. Therefore, the descending speed of the boom 4 becomes slow, and for example, the packet 7
can be lowered slowly. In other words, pushbutton 4
If you press 5, the spool of the solenoid valve 12 or 15 will be in a half-open state in any case, making it easier to control the front loader and performing more precise work compared to the conventional method of simply opening and closing. can.

While the boom 4 is moving up and down, the cylindrical body 47 and the rod 48 continue to expand and contract, and when the boom 4 descends to a predetermined height as indicated by the imaginary line P in FIG. 2, the cam 49 of the rod 48 detects the position. Since the switch 46 is operated to make contact, the contact is changed to contact a. Then, the pulse signal from the pulse generation circuit 31 is transmitted to the transistor Tr of the switch element 27 via the contact a.
, the switch element 27 repeats on/off operations, and the solenoid valve 12 becomes half-open as described above. Therefore, from then on, the descending speed of the boom 4 becomes slow, and the packet 7 can be brought into contact with the ground slowly.

Next, after the packet 7 is placed on the ground, when running the packet 7 while following the undulations of the ground to perform leveling work, etc., the control lever 36 is moved from the first stage as shown in FIG. The tilting operation is performed further forward (arrow A) to the second stage, and the contact a of the changeover switch 24 is closed to shift to floating control. That is, when the contact a of the changeover switch 24 is closed with the packet 7 grounded, the contact a of the pressure switch 18 is closed, so the lowering solenoid 14 of the solenoid valve 12 is activated and the solenoid valve 12 is switched in the lowering direction. Then, pressure oil is supplied to the boom cylinder 6 in the contraction direction, and the pressure on the discharge side of the hydraulic pump 9 begins to rise as shown in FIG. When the pressure exceeds the set pressure Pg, the pressure switch 18 is switched to contact a, and the rising solenoid 13 of the solenoid valve 12 is energized. Therefore, as shown in FIG. 7, the solenoid valve 12 switches to the rising side after going through neutral, but the pressure increases until it becomes neutral, and then gradually decreases. That is, when the electromagnetic valve 12 is on the downward side, the boom cylinder 6 is pushing down the packet 7 so that it touches the ground, so the pressure increases. However, when it passes neutral and begins to switch to the rising side, the pressing force is released and acts in the rising direction, so the pressure decreases until it reaches the rising pressure P+ with no load. And while this pressure is decreasing,
When the pressure switch 18 switches again from the contact point a to the contact point Pt at the set pressure Pt, and the solenoid valve 12 switches from the ascending side to the descending side, the boom cylinder 6 operates in the retracting direction again in the same manner as described above. Therefore, the pressure starts to rise again, and the same operation is repeated thereafter. As a result, the boom 4 is maintained in a floating state so that the packet 7 follows the undulations of the ground, so that the desired work can be performed. During this floating control, switch 22.2
By operating 3, packet operations are also possible.

(Effects of the Invention) According to the present invention, the switching element connected in series with the solenoid is intermittently driven by a drive signal to repeatedly excite and demagnetize the solenoid. Despite this, a half-open state can be obtained and the flow rate can be controlled in stages. Therefore, the lifting and lowering speed of the boom can be arbitrarily selected as required, and the work is easy.

Further, since it is only necessary to select between continuous and intermittent drive signals to be applied to the switch elements using a changeover switch, the operation is easy to handle and can be carried out easily. Furthermore, the boom's lifting and lowering movements are detected by a position detection switch, and when the boom is below a predetermined height, an intermittent drive signal is applied to the lowering switch element, which prevents shocks when the boom is lowered. In a front loader or the like, operation at the time of packet grounding becomes easier.

[Brief explanation of drawings]

The drawings show a first embodiment of the present invention, in which Fig. 1 is an electric circuit diagram, Fig. 2 is an overall side view, Fig. 3 is a hydraulic circuit diagram, and Fig. 4 is an installation of a position detection switch. FIG. 5 is a sectional view of a part of the control lever, FIG. 6 is a switch arrangement diagram, and FIGS. 7 and 8 are operation explanatory diagrams. 4-boom, 6--boom cylinder, 7--packet, 8--packet cylinder, 12.15--electromagnetic valve, 13-17--solenoid, 18--pressure switch, 26-2 !1-switch element, 31-pulse generation circuit, 35--changeover switch, 36--control lever,
46--Position detection switch. Figure 6 jIZ diagram Figure 8

Claims (1)

[Claims] 1. In a working machine equipped with a boom that can be raised and lowered by a boom cylinder, and in which the boom cylinder is controlled by an open/close type solenoid valve, a method for passing a predetermined value of excitation current to the solenoid for raising and lowering the solenoid of the solenoid valve. The switch elements are connected to each other, and a circuit that generates a continuous drive signal and a circuit that generates an intermittent drive signal are provided,
A changeover switch for selectively applying both drive signals from these circuits to each switch element, and a switch for detecting the lifting and lowering operation of the boom and transmitting the intermittent drive signal for lowering when the boom is below a predetermined height. 1. A boom elevation control device for a working machine, characterized in that a position detection switch element is provided for applying a signal to a switch element.