JPH0124404Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a control circuit for an actuator.

What is shown in FIG. 1 shows a conventional actuator control circuit. In this device, 1 and 2 are first and second pumps that discharge oil from a tank 3, respectively. 4 supplies discharged oil from the first pump 1 to the first actuator 5 via an oil passage 5' or 5'', and supplies discharged oil from the first actuator 5 to a tank 3 via an oil passage 5'' or 5'. This is a 5-position directional valve that allows the flow to flow back. This 5-position directional control valve 4 has a neutral position 8 where its P port 6 is blocked and its bypass port 7 is communicated, and a neutral position 8 where its bypass port 7 is communicated and its P port 6 is communicated with the oil passages 5', 5''. 2 positions 9 and 10 are connected to either one of the oil passages 5' and 5'', and the bypass port 7 is blocked and the P port 6 is connected to either one of the oil passages 5' and 5''. The first actuator 5 is switched between two positions 11 and 12 for forward and reverse rotation, and in the two positions 9 and 10, the oil supplied from the P port 6 is throttled by a throttle 13. 14 supplies discharge oil from the second pump 2 to the second actuator 15 via an oil passage 15' or 15'', and also supplies the oil discharged from the second pump 2 to the second actuator 15.
This is a three-position directional switching valve that allows discharged oil from to flow back into the tank 3 via an oil path 15'' or 15'.The three-position directional switching valve 14 has its P port 16 blocked and its bypass port 17 blocked. The neutral position 18 is in communication with the bypass port 17, and the P port 16 is connected to the oil passage 1.
5', 15'' to rotate the second actuator 15 in the forward and reverse directions.
It is configured to be connected to 0. 21 is a 3-position directional switching valve provided before the 3-position directional switching valve 14, and is connected to a third actuator 22 such as a cylinder.
I like to drive. This three-position directional switching valve 21 has a neutral position 25 in which its P port 23 is blocked and its bypass port 24 is communicated, and a neutral position 25 in which its P port 24 is blocked and its P port 23 communicates with the third actuator 22 in forward and reverse directions. It is configured to be connected to two positions 26 and 27 for actuation in the direction. 28 is a discharge oil passage 29 connecting the first pump 1 and the 5-position directional switching valve 4, and the second pump 2 and the 3-position directional switching valve 14.
This is a bypass path that connects the discharge oil path 30 to the latter stage of the three-position directional switching valve 21. 31
is a flow control valve provided in the bypass passage 28, which takes out the pressure oil from either of the oil passages 5', 5'' on the high pressure side via the high pressure communication valve 32, and this pressure oil passes through the pilot passage 33 to the spring. 34 in the valve closing direction, and the pressure oil in the discharge oil passage 29 acts in the valve opening direction via the pilot passage 35.Therefore, this flow control valve 31 acts on the oil in the discharge oil passage 29 in the valve opening direction through the pilot passage 35. It opens when the pressure becomes higher than a certain level compared to the hydraulic pressure of the oil supply/discharge oil passages 5', 5'' to the first actuator 5. 36
connects the discharge oil passage 30 between the 3-position directional control valves 14 and 21 and the connection path 37 connecting the bypass port 17 of the 3-position directional control valve 14 and the bypass port 7 of the 5-position directional control valve 4. This is a bypass road. Reference numeral 38 designates a flow control valve provided in the bypass passage 36, which takes out the pressure oil from either of the oil passages 15', 15'' on the high pressure side via the high pressure communication valve 39, and allows this pressure oil to flow through the pilot passage 40. The flow control valve 38 acts in the valve closing direction together with the spring 41, and the pressure oil in the discharge oil passage 30 acts in the valve opening direction through the pilot passage 42.
It opens when the hydraulic pressure of 0 becomes higher than a certain level compared to the hydraulic pressure of the supply/discharge oil passages 15' and 15'' to the second actuator 15. 43 indicates the flow of the connecting passage 37 and the bypass passage 28. This is a bypass path that connects the front stage of the control valve 31. 44 is a check valve provided in the bypass path 28, and the discharge oil path 3
This prevents oil from flowing in from 0. Reference numeral 45 denotes a check valve provided in the bypass passage 43, which prevents oil from flowing in from the discharge oil passage 29. 46 is provided in the bypass passage 28 between the flow control valve 31 and the check valve 44 and the bypass passage 47 connected to the bypass passage 36 downstream of the flow control valve 38, which is normally kept closed by a spring; This is an on-off valve that opens when the hydraulic pressure becomes high. The first actuator 5 is driven to drive the main winch drum for heavy loads via a clutch (not shown) in the case of a crane, and the second actuator 15 is driven to drive the main winch drum for heavy loads via a clutch (not shown). The auxiliary winch drums for small loads are individually driven.

The conventional actuator control circuit configured as described above had the following drawbacks.

When the flow control valve 31 controls oil, the P port 6 is blocked in the neutral position 8 of the 5-position directional switching valve 4, so when the 5-position directional switching valve 4 is located at the neutral position 8, This occurs when the position is in two positions 9 and 10, forward and reverse. In either case, since the bypass port 7 is in communication, the oil discharged from the second pump 2 side is returned to the tank 3 via the bypass port 7, so that the flow control valve 31 eventually controls the oil. The maximum amount of oil is the total amount of oil discharged from the first pump 1. On the other hand, when the 3-position directional control valve 14 is driven independently, the entire amount of oil discharged from the first pump 1 side is supplied via the flow control valve 38 as described above, so this discharge oil and the second pump 2 side are The three-position directional switching valve 14 needs to control the oil that merges with the discharge oil.

Therefore, the flow control valve 38
The position direction switching valve 14 is switched between its neutral position 18 and forward/reverse position 2.
When controlling the oil passing through the three-position directional control valve 14 by placing it between positions 19 and 20,
It is necessary to control the excess oil in the combined oil.

Since this excess oil may exceed the total amount of oil discharged from the first pump 1, the flow control valve 38 is designed as a large flow control valve with a larger maximum control oil amount than the flow control valve 31. The disadvantage is that it needs to be manufactured. In addition, the 3-position directional control valve 14 is positioned between its neutral position 18 and the two forward and reverse positions 19 and 20, and while the oil passing through the 3-position directional control valve 14 is throttled, only the second actuator 15 is driven at a slow speed. At this time, as described above, the oil controlled by the 3-position directional control valve 14 is not only the discharge oil from the second pump 2 but also the combined oil with the discharge oil from the first pump 1, so the 3-position directional control valve 14 Due to the slight difference in the amount of tilt of the lever that operates the second
There was a drawback that the movement of the actuator 15 varied greatly.

The present invention provides a novel actuator control circuit that does not have the drawbacks mentioned above.

Next, a specific embodiment of the present invention will be described in detail with reference to FIG.

2 is different from FIG. 1 in that a 5-position directional control valve 50 is provided in place of the 3-position directional control valve 14 in FIG.
Bypass passages 51 and 52 are newly provided which branch off at the discharge oil passages 29 and 30 at the front stage of the 5-position directional control valves 4 and 50, and these bypass passages 51,
52 are provided with flow control valves 31 and 38, and a check valve 5 is provided downstream of these flow control valves 31 and 38 in these bypass paths 51 and 52.
3 and 54 are provided, and flow control valves 31 and 3 are provided.
After passing through these check valves 53 and 54, the oil that has passed through 8 passes through the bypass port 7 of the 5-position directional control valve 4 and the check valve 55, and flows into the first connecting path 56 connected to the discharge oil path 29. In this way, the connection path 37 is eliminated and the bypass port 7 of the 5-position directional control valve 4 is removed.
5 is connected to the tank path 48 in the communication state through the newly provided second connection path 57.
Bypass port 6 of the position direction switching valve 50 to be described later
The point connected to the discharge oil passage 30 connected to the P port 59 of the 5-position directional control valve 50 via the 0 and check valve 58, the bypass port 60 is connected to the tank passage 61.
The other points are the same as in FIG. 1.

To further explain the 5-position directional control valve 50, the 5-position directional control valve 50 has its P port 5.
9 is blocked and its bypass port 6
A neutral position 62 where 0 is communicated, and a second position where the bypass port 60 is communicated and the P port 59 is connected to either one of the oil passages 15', 15'', causing the second actuator 15 to move forward or reverse. 63, 64, and the bypass port 60 is blocked, and its P port 59 is connected to the oil passage 15',
15'' and is switched to two positions 65 and 66 for rotating the second actuator 5 forward and reverse, and in the two positions 63 and 64, the oil supplied from the P port 59 is throttled by the throttle 67. It is configured as follows.

Next, the effect will be explained.

Regarding the case where the 5-position directional switching valve 4 is located at two positions 9 and 10, forward and reverse, and the 5-position directional switching valve 50 and the 3-position directional switching valve 21 are both located at the neutral position.

In this case, the oil discharged from the second pump 2 is
Bypass path 52, flow control valve 38, check valve 54, first connection path 56, bypass port 7,
The water passes through the second connection path 57, the bypass port 60, and the tank path 61 in order and is returned to the tank 3. On the other hand, the oil discharged from the first pump 1 is supplied to drive the first actuator 5 through the P port 6, but it is passed through the P port 6 to drive the first actuator 5.
A pressure difference occurs between before and after, and the flow control valve 31 and the on-off valve 46 are opened, whereby a part of the oil passes through the flow control valve 31 and the on-off valve 46 as surplus oil and is returned to the tank 3. It is something that will be done.

The 5-position directional control valve 50 has two positions, 63 and 6, forward and reverse.
4, and the 5-position directional control valve 4 and the 3-position directional control valve 21 are both located in the neutral position.

In this case, the oil discharged from the first pump 1 is
Bypass path 51, flow control valve 31, check valve 53, first connection path 56, bypass port 7,
The water passes through the second connection path 57, the bypass port 60, and the tank path 61 in order and is returned to the tank 3. On the other hand, the oil discharged from the second pump 2 is used to drive the second actuator 15 through the P port 59, but a pressure difference is created between the front and back of the five-position directional control valve 50 due to the throttle 67, and the flow is controlled. The valve 38 is opened, whereby a portion of the oil is transferred to the flow control valve 38 as surplus oil.
The water passes through the check valve 54, the first connection path 56, the bypass port 7, the second connection path 57, the bypass port 60, and the tank path 61 in this order and is returned to the tank 3.

Next, the 5-position directional control valve 4 is switched to the forward and reverse 2-position 11,
12, and both the 5-position directional control valve 50 and the 3-position directional control valve 21 are located at the neutral position.

In this case, the entire amount of oil discharged from the first pump 1 is supplied to the first actuator 5. On the other hand, the oil discharged from the second pump 2 flows through the bypass path 52, the flow control valve 38, the check valve 54, and the first connection path 5.
6, but since the bypass port 7 is blocked, it is not supplied to the second connection path 57, but is supplied to the discharge oil path 29 via the check valve 55, and as a result, the first actuator 5 It is driven at high speed by the combined oil of the first pump 1 and the second pump 2. At this time, the flow control valve 31 remains closed because no pressure difference is generated between the front and back of the five-position directional switching valve 4.

5 position directional control valve 50 has 2 positions of forward and reverse 65,6
6, and both the 3-position directional control valve 21 and the 5-position directional control valve 4 are located at the neutral position.

In this case, the entire amount of oil discharged from the second pump 2 is supplied to the second actuator 15. On the other hand, the first
The oil discharged from the pump 1 passes through the bypass passage 51, the flow control valve 31, the check valve 53, the first connection passage 56, the bypass port 7, and the second connection passage 57, and the bypass port 60 is blocked, so that the oil is then discharged. The oil is supplied to the oil passage 30, and the second actuator 15 is eventually driven at high speed by the combined oil of the first pump 1 and the second pump 2.

Regarding the case where the 5-position directional switching valve 4 and the 5-position directional switching valve 50 are used to simultaneously drive the first actuator 5 and the second actuator 15.

In the above case, the 5-position directional control valve 4, 50 has 1 of 2 positions, forward and reverse, which prevents the oil from passing through the throttle 13, 67.
1, 12 and 65, 66, each flow control valve 31, 38 remains closed, and the first actuator 5 receives the entire amount of oil discharged from the first pump 1, and the second actuator 15 receives the entire amount of oil discharged from the second pump 2. The entire amount of discharged oil is supplied respectively. Also, in the above case, the 5-position directional control valve 4 has two positions, 9 and 1, in forward and reverse directions.
65, where the directional control valve 50 is in 2 positions, forward and reverse;
67, the oil discharged from the first pump 1 passes through the P port 6 and is used to drive the first actuator 5, but the pressure between the front and back of the 5-position directional control valve 4 is reduced by the throttle 13. A difference occurs, and the water passes through the flow control valve 31 and the on-off valve 46 in order and is returned to the tank 3. On the other hand, the entire amount of oil discharged from the second pump 2 passes through the P port 59 to the second pump.
Used to drive the actuator.

In the above case, the 5-position directional control valve 4 is in the forward and reverse 2 positions 11 and 12, and the 5-position directional control valve 50 is in the forward and reverse 2 positions.
When located at positions 63 and 64, the entire amount of oil discharged from the first pump 1 passes through the P port 6 and is used to drive the first actuator 5. On the other hand, the oil discharged from the second pump 2 is
Although a pressure difference occurs between the front and rear of the position direction switching valve 50 and the flow control valve 38 opens, the discharge oil passage 29
If the generated pressure in the discharge oil passage 30 is higher than that in the discharge oil passage 30, the check valve 55 will not open and the hydraulic pressure in the discharge oil passage 30 will be reduced to a relief valve (see Fig. 2) that regulates the maximum circuit pressure of the oil passage. 70), a part of which is returned to the tank 3 via the relief valve 70, and the remainder is used to drive the second actuator 15.

Note that when an on-off valve similar to the on-off valve 46 is provided in a tank passage branched from between the flow control valve 38 and the check valve 54, and this on-off valve is opened when the pressure in the pilot passage 40 is increased like the on-off valve 46, the above-mentioned The second pump 2 without passing through the relief valve 70
A part of the oil discharged from the tank 3 can be returned to the tank 3 via the on-off valve, and when the on-off valve is provided in this way, the 3-position directional control valve 2
1 in the bypass passage 56, the 5-position directional control valve 4 or 50 can be switched between the 2-position forward and reverse directional control valves 9 and 50.
10 or 63, 64 and 3
In the simultaneous operation of operating the position direction switching valve 21 and driving the third actuator 22 at a slow speed, there is no back pressure on the rear stage side of the three position direction switching valve 21, so there is no adverse effect on the third actuator 22. play.

In summary, the present invention has a bypass port in the oil passage connecting the first pump to the first actuator, a neutral position and two forward and reverse positions where this is communicated, and two forward and reverse positions where this is blocked. A 5-position directional switching valve is provided in which the P port is blocked at the position, and a bypass port is provided in the oil passage connecting the second pump to the second actuator, and this is connected to the neutral position and two forward and reverse positions, which are blocked. A control circuit for an actuator is provided with a 5-position directional switching valve which has two forward and reverse positions, and in which the P port is blocked at the neutral position, and the control circuit includes a 5-position directional switching valve in which a discharge oil passage is provided at a stage before the former 5-position directional switching valve. A bypass passage having a flow control valve that opens when the hydraulic pressure of the discharge oil passage becomes higher than a certain level compared to the oil pressure of the oil passage connected to the first actuator after the former five-position directional control valve. In addition, the hydraulic pressure in the discharge oil passage at the front stage of the latter 5-position directional control valve is made to be branched, and the hydraulic pressure in the discharge oil passage is proportional to the hydraulic pressure in the oil passage connected to the second actuator at the rear stage of the latter 5-position directional control valve. A bypass path having a flow control valve that opens when the temperature rises above a certain level is branched, and the downstream stage of the flow control valve in these bypass paths is connected to the bypass port of the former 5-position directional control valve and The bypass port of the former 5-position directional switching valve is connected to the discharge oil passage in the previous stage of the former 5-position directional switching valve via a check valve, and the bypass port of the former 5-position directional switching valve is connected to the latter 5-position directional switching valve via the second connection path in its communicating state. The switching valve is connected to the discharge oil passage at the front stage of the latter 5-position directional switching valve via the bypass port and check valve, and when the latter 5-position directional switching valve is in communication, the bypass port is connected to the tank passage. Since the control oil amount of one of the two flow control valves is only the discharge oil amount of the first pump, the control oil path of the other flow control valve is connected to the discharge oil amount of the second pump. Since it is only the amount of oil,
Both flow control valves can be downsized, and the first and second actuators can be operated with the same feeling of operation.

[Brief explanation of drawings]

FIG. 1 shows a conventional actuator control circuit, and FIG. 2 shows an actuator control circuit according to an embodiment of the present invention. 1...first pump, 5...first actuator, 7
...Bypass port, 8...Neutral position, 9, 10...2 forward and reverse positions, 11, 12...2 forward and reverse positions, 6...P port, 4...5 position directional switching valve, 2...2nd pump, 1
5...Second actuator, 60...Bypass port, 62...Neutral position, 63, 64...Two forward and reverse positions,
65, 66...Forward/reverse 2 positions, 59...P port, 50
...5 position directional switching valve, 29...Discharge oil path, 31...Flow control valve, 51...Bypass path, 30...
Discharge oil path, 38...Flow control valve, 52...
bypass path, 56...first connection path, 55...check valve,
57...Second connection path, 58...Check valve, 61...Tank path.

Claims (1)

[Scope of utility model registration request] The oil passage connecting the first pump to the first actuator has a bypass port, and has a neutral position and two forward and reverse positions where this is communicated, and two forward and reverse positions where this is blocked, and the P port is blocked in the neutral position. A 5-position directional switching valve is provided, and a bypass port is provided in the oil passage connecting the second pump to the second actuator, and the valve has a neutral position and two forward and reverse positions where this is communicated, and two forward and reverse positions where it is blocked. A control circuit for an actuator is provided with a 5-position directional switching valve in which the P port is blocked at the neutral position, and the hydraulic pressure of the discharge oil passage is connected to a discharge oil passage at a stage upstream of the former 5-position directional switching valve. A bypass passage having a flow control valve that opens when the hydraulic pressure in the oil passage connected to the first actuator after the former 5-position directional control valve is higher than a certain level is branched, and the latter 5-position directional control valve is branched. The hydraulic pressure in the discharge oil passage in the front stage of the position directional switching valve has become higher than a certain level compared to the oil pressure in the oil passage connected to the second actuator in the latter stage of the latter 5-position directional switching valve. Bypass paths having flow control valves that open when the flow control valves are opened are branched, and the downstream stages of the flow control valves of these bypass paths are connected to the former through the bypass port and check valve of the 5-position directional control valve through the first connecting path. The bypass port of the former 5-position directional control valve is connected to the discharge oil passage at the front stage of the 5-position directional control valve, and the bypass port of the former 5-position directional control valve is connected to the bypass port of the latter 5-position directional control valve and the reverse via the second connecting path. The latter 5-position directional switching valve is connected to the discharge oil passage at the front stage of the latter 5-position directional switching valve via a stop valve, and the latter 5-position directional switching valve is characterized in that when its bypass port is in communication, the bypass port is connected to the tank passage. Actuator control circuit.