JP2794677B2 - Lifting cylinder proportional control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a proportional control circuit for raising and lowering a cylinder of an agricultural tractor, and more particularly to reducing the number of valves for controlling the direction and flow rate of a main line and the number of proportional valves for proportionally controlling the valves. The present invention relates to a lifting / lowering cylinder proportional control circuit in which a control block is simplified and compact, and at the same time, an electrical relationship for controlling the block is also simplified.

[0002]

2. Description of the Related Art As a conventional lift cylinder proportional control circuit of an agricultural tractor, for example, there is a circuit shown in FIG. In this case, the ascending speed of the single-acting cylinder 4 is controlled by the main valve 29 and the proportional pressure regulating valve 25 for proportionally controlling the same when the ascending is performed. The lowering speed control of the single-acting cylinder 4 is performed by the main valve 26 for use and the proportional throttle valve 24 for proportionally controlling the same. In this circuit configuration, two of the main valve 26 for controlling the flow rate returning the main valve 29 for controlling the flow rate of the flow during rise of the cylinder from the falling time the cylinder is necessary, and proportional control the respective main valve Also, two proportional valves 24 and 25 are required. Further, there is a problem that many main valves for flowing a large capacity require a space including a larger pipe. Real
The circuit disclosed in Japanese Unexamined Patent Publication No. 2-54901 is a similar circuit.
In the Japanese Patent Publication No. 58-25163,
The ascending main valve 29 and the descending main valve 26 are one three-position switching valve, and a control chamber is provided at both ends of the switching valve, and pressure oil from the proportional valve is introduced into the control chamber. In this way, the number of main valves is reduced.

[0003]

However, also in this case, two proportional valves are required. Further, if the pump is lowered while the pump is operating, wasteful energy is generated because the pump is not unloaded, and a separate unload circuit is required. In addition, it was necessary to operate the electromagnetically operated check valve and the proportional valve when descending. On the other hand, JP HirakiAkira 64-46
In the 001 publication, the pilot line of the unload valve is opened to the tank at the main valve lowering position in order to unload the pump even when the pump is lowered, although it is not a proportional valve . However, the main valve is also disclosed in Japanese Patent Publication No. 58-25163.
When a 3-position switching valve is used and a proportional valve is used
Again requires two. Further, when the pump is lowered when the pump is stopped, it is still necessary to operate the two valves of the main valve and the switching valve, and further, there is a problem that the number of valves connected to the cylinder line increases and leakage increases. As described above, each of the conventional devices has advantages. However, as common problems, not only two expensive proportional valves are required, but also the circuit becomes complicated, and a constant current control (not shown) for proportional valve control is performed. Two amplifiers were required, which was very costly.

SUMMARY OF THE INVENTION An object of the present invention is to reduce the number of main valves that flow a large amount of capacity in a lifting / lowering cylinder proportional control circuit, simplify the control block and reduce the size of the control block to reduce the space including piping, and further increase the cost of the proportional valve. To provide an ascending and descending cylinder proportional control circuit which has advantages such as a constant current control amplifier for proportional valve control, which is very costly, and each of the advantages of the conventional example such as operability at the time of descent and a leak amount. It is in.

[0005]

SUMMARY OF THE INVENTION Therefore, according to the present invention, a main valve and a pilot check valve are connected between a pump and a single-acting cylinder, and a main valve and a pilot check valve are connected between the pump and the main valve. A load-sensitive pressure control valve that receives the main line pressure between the pilot check valve and the load chamber is connected, and the pilot pressure of the pilot check valve is guided between the pilot check valve and the single-acting cylinder via a pilot line via a switching valve. . One end of the main valve spool is provided with a control chamber in which pressure oil is introduced so that the spool throttle can be controlled against the spring and the other end is opposed by the spring. Then, the main valve spool is the system
When pressure oil is not introduced into the chamber, it is pushed by the spring, closes the pump port, connects the main line to the tank through the throttle, and spools the throttle against the spring.
Pressure oil from the pump via the pump line to the main line
Supply or main line pressure oil to pump line, negative
The discharge to the tank can be selected via the load-sensitive pressure control valve . Furthermore, a proportional pressure regulating valve that guides the pump pressure and the pilot line pressure to its own pressure port via the shuttle valve and generates the pressure in proportion to the magnitude of the input current is provided, and the pressure oil from the proportional pressure regulating valve is supplied to the proportional pressure line. Through the control chamber of the main valve. In addition, a pilot switching valve for unloading the load-responsive pressure control valve is provided. By providing such a lifting cylinder proportional control circuit, the above-mentioned problem of the prior art has been solved. Further, it is preferable that the pilot switching valve receives the pressure of the pilot line and unloads the load-sensitive pressure control valve.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to FIGS. FIG. 1 is a hydraulic circuit diagram showing a configuration of a lift cylinder proportional control circuit according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a relationship between operation of a pilot valve and a proportional pressure regulating valve of FIG. 1 and cylinder operation. The lift cylinder proportional control circuit of the present invention includes a main valve 8 between the pump 1 and the single-acting cylinder 4.
And a pilot check valve 7 connected between the pump 1 and the main valve 8, a load-sensitive pressure control valve 9 for receiving the pressure of the main line 19 between the main valve and the pilot check valve 7 into the load chamber 31. The pilot pressure of the pilot check valve 7 is connected, and is guided from a cylinder line 21 between the pilot check valve 7 and the single-acting cylinder 4 via a pilot line 18 via the electromagnetic switching valve 11.

When there is no input current, the main valve spool of the main valve 8 is pushed by a spring 32 to close the pump port P and connect the main line 19 to the tanks T, T3 (1).
2) is communicated via a diaphragm. Further, the main valve 8, the position of the main valve spool shown, the control chamber 28 perating the Came ra over to the right position shown communicating with the pump port P via a spool stop the main line 19 against the spring 32 Is provided. The spool throttle is supplied to the control room 28.
It is made variable by the supplied pressure oil. Main line pressure
When the pressure at the pump port is higher than the
Main line side from pump port through spool throttle
And the main line pressure is higher than the pump port pressure.
When the pressure is high, the main line pressure oil
Pump line through a throttle, load-sensitive pressure control valve
9 to the tank T1 (12)
ing. The pump pressure and the pilot line 18 pressure are guided to its own pressure port 22 via the shuttle valve 16 and a proportional pressure regulating valve 10 which is generated in proportion to the magnitude of the input current is provided. Acting on the control chamber 28 via the proportional pressure line 20 ,
It can be controlled by the input current. Switching valve 1 for unloading load-sensitive pressure control valve 9
7 are provided. In the embodiment, the pilot switching valve 17 is used.
Is designed to unload the load-sensitive pressure control valve 9 by receiving the pressure of the pilot line 18. Reference numeral 2 denotes a safety valve that regulates the maximum pressure of the pump 1.

Next, the operation will be described.
Is stopped, the valve position of each valve assumes the position shown in FIG. Since there is no input current, the main valve 8 is pushed by the spring 32 to close the pump port P and connect the main line 19 to the tank 12. The electromagnetic switching valve 11 is in a non-excited state, and a pilot line 18 for guiding pilot pressure to the pilot check valve 7 is connected to the drain line 15 via the electromagnetic switching valve 11, the pilot check valve 7 is closed, and the load 5 The cylinder line 21 is connected to the pilot check valve 7 and the electromagnetic switching valve 11
, The position is held without falling by its own weight. Since the leak of the cylinder line 21 is caused only by the pilot check valve 7 and the electromagnetic switching valve 11 having almost no leak, the aforementioned Japanese Patent Publication No. 58-25163,
There is less leakage than that of Japanese Patent Application Laid-Open No. 64-46001.

In this state, the pilot switching valve 17 receives the pressure of the pilot line 18. However, since the pilot line 18 is connected to the drain line 15, the pilot switching valve 17 is in the switching position shown in FIG. It is connected to the chamber 31. However, since the main line 19 is communicated with the tank 12, an unload state is established in which the entire pressure oil of the pump 1 is released to the tank 12 at a pressure corresponding to the built-in spring of the load-sensitive pressure control valve 9. When there is no input current in the proportional pressure regulating valve 10, the proportional pressure regulating valve 10 closes the pressure port 22 through which the pump pressure and the pilot line 18 pressure are led through the shuttle valve 16, and the proportional pressure line 20 is connected to the drain line 15 It is connected to the.

When the cylinder 4 is raised, a current is applied to the proportional pressure regulating valve 10 from the state shown in FIG. 1 to generate pressure oil having a magnitude proportional to the magnitude of the input current. The main valve 8 is supplied to the control chamber 28 of the main valve 8.
9 to the right position shown in the figure to communicate with the pump port P. That is, the pump pressure is guided to the pressure port 22 of the proportional pressure regulating valve 10 via the shuttle valve 16, and pressure oil having a magnitude proportional to the magnitude of the input current is supplied via the proportional pressure regulating valve 10 and the proportional pressure line 20. It is supplied to the control room 28 and the main valve 8 is opened. The main valve spool has a spool throttle, and the main valve 8 at this time constitutes a variable throttle valve.

At this time, the pressure difference before and after the main valve 8 is kept constant by the load-sensitive pressure control valve 9 to perform pressure compensation.
From the pressure of the main line 19, the pressure of the pump line 30
It becomes high with pressure oil discharged from the pump 1 main valve 8, flow magnitude of the flow rate in proportion to the magnitude of the current supplied to the proportional regulating valve 10 to the main line 19, proportional flow control Is performed, the surplus oil amount in the pump line 30 is controlled by the pressure generated in the main line 19 plus the pressure corresponding to the built-in spring of the load-sensitive pressure control valve 9, and the tank T <b> 1 (12) ) Will be missed. The pressure oil supplied to the main line 19 opens the pilot check valve 7, enters the cylinder line 21, and raises the cylinder 4 which receives the load 5. Further, at this time, the electromagnetic switching valve 11 is de-energized at the illustrated position.

When the cylinder 4 is lowered, the electromagnetic switching valve 11 is excited from the state shown in FIG. When the electromagnetic switching valve 11 is excited, the pilot pressure of the pilot check valve 7 is guided from the cylinder line 21 between the pilot check valve 7 and the single-acting cylinder 4 by the pilot line 18 via the electromagnetic switching valve 11, and the pilot check valve 7 open the cylinder line 21 and main line 1
1 and the main valve 8 allows the pressure oil in the main line 19 to escape to the tank 12 even at the position shown in FIG. Further in this state, to generate a proportional pressure proportional to the magnitude of the input current to the proportional pressure regulating valve 10, is supplied to the control chamber 28 of the through main valve 8 the ratio Rei圧 line 20, main valve 8 is controlled, With the opening proportional to the proportional pressure, the main line 19 is connected to the pump port P
Open against .

At this time, pressure is introduced to the pilot line 18 and the pilot switching valve 17 is switched, so that the pressure oil in the load chamber 31 of the load-sensitive pressure control valve 9 is in communication with the drain line 15. The pressure oil in the pump line 30 is in an unloaded state in which the entire amount is released to the tank 12. Therefore, the pressure generated in the pump line 30
Occurs on the cylinder line 21, that is, the main line 19.
Pressure is lower than the pressure of
Main line with a flow rate proportional to the magnitude of the input current to valve 10
From the pump 19 to the pump line 30 and the pressure from the pump
Merges with the oil and passes through the load-sensitive pressure control valve 9 to the tank T1.
(12). And cylinder 4
The self-weight descent speed is controlled by the input current to the proportional pressure regulating valve 10.
Trolled.

FIG. 2 is an explanatory diagram summarizing the relationship between the above-described cylinder stop, ascending and descending operations, and the operations of the pilot valve 11 and the proportional pressure regulating valve 8. If it is necessary to lower the cylinder 4 with the pump 1 stopped as an emergency operation, in this circuit, the pilot check valve 7 and the proportional pressure regulating valve 10
Need not be operated, and these valves are controlled by the pressure generated in the cylinder 4 by the load 5, so that the pilot valve
Change the 11 and control the cylinder 4 while controlling its own weight
Can descend. Furthermore, without operating the proportional pressure regulating valve 10
Only by opening the pilot check valve
It is controlled by the throttle of the spring pressing position of the valve spool.
Is discharged to T3 (12).
Cylinder 4 can be easily lowered by its own weight just by switching 1
Wear.

[0015]

According to the present invention as described in the foregoing, one end of the main valve spool and the other end is pushed by a spring is introduced controllably pressurized oil spool stop against the spray phosphorus <br/> grayed The control room is provided with a two-position valve, and the main valve spool is
The pump through the spool throttle
From the pump line to the main line or
Main line pressure oil is pump line, load sensitive pressure control
Selectable discharge to tank via valve, raise and lower
Sometimes, throttle the spool between the main line and the pump line.
Pressure so that pressure oil passes through it, and adjust this opening
Because it can be controlled with an example valve, the main valve that flows a large capacity is reduced or reduced in size, the control block is simplified and compacted to reduce the space including piping, and more expensive proportional valves and very expensive. The number of constant current control amplifiers for proportional valve control has been reduced from two for each of the conventional valves to one for each, and a space-saving and extremely low-cost lifting / lowering cylinder proportional control circuit has been provided. In addition, pilot valve 1
1 and proportional pressure control valve 10 enable self-weight drop control
Needless to say, the cylinder 4 can be easily lowered by its own weight simply by switching the pilot valve 11, so that it can be lowered with one valve operation regardless of whether the pump is operating or stopped. It has several advantages such as a small amount.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing a configuration of a lift cylinder proportional control circuit according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between operation of a pilot valve and a proportional pressure regulating valve of FIG. 1 and cylinder operation.

FIG. 3 is a hydraulic circuit diagram showing a configuration of a conventional lift cylinder proportional control circuit.

[Explanation of symbols]

 1. . Pump4. . Single acting cylinder 7. . 7. Pilot check valve 7 . Main valve 9. . Load-sensitive pressure control valve 10. . Proportional pressure regulating valve 11. . Switching valve 12. . Tank 16. . Shuttle valve 17. . Pilot switching valve 18. . Pilot line 19. . Main line 20. . Proportional pressure line 22. . Pressure port 28. . Control room 31. . Load chamber 32. . spring

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F15B 11/04

Claims (2)

(57) [Claims] A main valve and a pilot check valve are connected between a pump and a single-acting cylinder, and a main line pressure between the main valve and the pilot check valve is connected between the pump and the main valve. A load-sensitive pressure control valve to be applied to the load chamber is connected, and the pilot pressure of the pilot check valve is led from between the pilot check valve and the single-acting cylinder via a pilot line via a switching valve , and the main valve of the main valve is controlled. One end of the valve spool is provided with a control chamber in which pressure oil is introduced so that the spool throttle can be controlled against the spring at one end, and the main valve spool is pressurized by the control chamber.
Oil is communicated with the tank through the closed main line squeeze the pump port is pushed into the spring when not introduced, the spool is at a position against the spring
Pressure oil from the pump via the pump line
To the main line or the main line pressure oil is pumped
To the tank via the load-sensitive pressure control valve
The pump oil and the pilot line pressure are guided to the pressure chamber of the control chamber via a shuttle valve, and the pressure oil having a magnitude proportional to the magnitude of the input current is supplied to the control chamber. An elevating cylinder proportional control circuit, comprising a proportional pressure regulating valve generated and supplied through a proportional pressure line, and a pilot switching valve for unloading the load-sensitive pressure control valve. 2. The lift cylinder proportional control circuit according to claim 1, wherein said pilot switching valve receives the pressure of said pilot line and unloads said load-responsive pressure control valve.