JP4565759B2 - Hydraulic control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic control device used in a construction vehicle such as a hydraulic excavator, and more particularly to a hydraulic control device including a plurality of circuit systems to which a pump is connected.
[0002]
[Prior art]
The conventional apparatus shown in FIG. 3 includes first to third pumps P1 to P3, and first to third circuit systems a to c are connected to each of the first to third pumps P1 to P3. ing.
In the first circuit system a, open center type first to third switching valves 11 to 13 are connected in parallel to a first supply flow path 1 connected to a first pump P1. The first to third switching valves 11 to 13 communicate the first pump P1 and the tank flow path 10 via the first neutral flow path 2 when they are in the neutral position shown in the figure. When one of the switching valves is switched, the pressure oil is supplied to the actuator (not shown) connected to the switching valve via the first parallel flow path 3.
Note that the maximum discharge amount of the first pump P1 is set based on the maximum required flow rates of the three actuators connected to the first to third switching valves 11 to 13.
[0003]
In the second circuit system b, open center type fourth to sixth switching valves 14 to 16 are connected in parallel to the second supply flow path 4 connected to the second pump P2. These fourth to sixth switching valves 14 to 16 also communicate the second pump P2 and the tank passage 10 via the second neutral passage 5 when in the illustrated neutral position. When one of the switching valves is switched, the pressure oil is supplied via the second parallel flow path 6 to an actuator (not shown) connected to the switching valve.
[0004]
The sixth switching valve 16 is a preliminary switching valve. The spare switching valve 16 is prepared in advance for a construction vehicle using a special actuator. That is, when only two actuators are controlled by the second circuit system b, the standby switching valve 16 is not used, but there are special actuators and a total of three actuators connected to the second control system b. In such a case, a special actuator is connected to the spare switching valve 16. A special actuator is controlled by the auxiliary switching valve 16.
Since a special actuator is rare, the maximum discharge amount of the second pump P2 is set based on the maximum required flow rates of the two actuators connected to the fourth and fifth switching valves 14 and 15. ing.
[0005]
On the other hand, in the third circuit system c, open center type seventh to ninth switching valves 17 to 19 are connected in parallel to the third supply flow path 7 connected to the third pump P3. These seventh to ninth switching valves 17 to 19 communicate with the third pump P3 and its downstream side via the third neutral flow path 8 to switch any switching valve when in the illustrated neutral position. Then, pressure oil is supplied to the actuator (not shown) connected to the switching valve via the third parallel flow path 9.
The maximum discharge amount of the third pump P3 is set based on the maximum required flow rates of the three actuators connected to the seventh to ninth switching valves 17-19.
[0006]
Further, the downstream side of the third neutral flow path 8 is connected to the second neutral flow path 5 of the second circuit system b, and the flow that connects the third neutral flow path 8 and the second neutral flow path 5 is established. A junction switching valve 20 is provided on the road. When this confluence switching valve 20 is in the open position shown in the figure, the third neutral flow path 8 and the second neutral flow path 5 communicate with each other, and the discharge oil of the third pump P3 is supplied to the second circuit system b. . When switched to the closed position, the third neutral flow path 8 communicates with the tank flow path 10 while the communication with the second neutral flow path 5 is blocked, and the discharge oil of the third pump P3 is discharged to the second circuit. It is no longer supplied to the system b.
[0007]
The reason why the flow paths to be joined as described above are provided is to prevent the flow rate supplied to the special actuator connected to the auxiliary switching valve 16 from being insufficient. That is, the auxiliary switching valve 16 is supplied with the discharge oil of the second pump P2. The maximum discharge amount of the second pump P2 is the actuator connected to the fourth and fifth switching valves 14, 15. Therefore, the flow rate supplied to the special actuator connected to the auxiliary switching valve 16 is not taken into consideration. Therefore, when this special actuator is operated, the supply flow rate may be insufficient.
Therefore, as described above, the shortage of the supply flow rate is compensated by joining the discharge oil of the third pump P3.
Note that the inflow of the pressure oil from the third pump P3 can be cut by the merging switching valve 20 because the flow rate from the second pump P2 depends on the type of the special actuator connected to the standby switching valve 16. This is because it may be sufficient.
[0008]
[Problems to be solved by the invention]
As described above, in the conventional example, a sufficient flow rate can be supplied to the actuator connected to the auxiliary switching valve 16.
However, in this conventional example, the maximum supply amount supplied to the actuator can be set only in two stages, that is, the single supply by the second pump and the total supply by the second and third pumps. Moreover, the two-stage flow rate is also almost determined by the maximum discharge amount of each pump. That is, the maximum supply amount to the actuator connected to the standby switching valve cannot be set finely.
[0009]
Therefore, depending on the type of actuator connected to the standby switching valve, the maximum supply amount that is optimal for the actuator cannot be set, and the operating speed is too fast or too slow, making it difficult for the operator to control. There was a thing.
An object of the present invention is to provide a hydraulic control device capable of setting a maximum supply amount to an actuator connected to a standby switching valve to an uninterrupted floor.
[0010]
[Means for Solving the Problems]
The first invention is provided with a circuit system including a plurality of pumps, an open center type switching valve connected to each pump, a confluence channel that merges the most downstream of these circuit systems, and the confluence channel. A preliminary switching valve, a flow rate control throttle provided in a flow path for supplying pressure oil to the actuator of the preliminary switching valve, a discharge flow path communicating the merging flow path and the tank, and provided in the discharge flow path A flow rate control valve, a pressure setting mechanism for setting the pressure on the upstream side of the flow rate control valve, and a pressure control mechanism for guiding the pressure generated on the upstream side of the flow rate control throttle to one pilot chamber of the flow rate control valve. A pilot line, a second pilot line that guides the pressure generated downstream of the flow control throttle to the other pilot chamber of the flow control valve, and the auxiliary switching valve shuts off the communication between the actuator and the junction flow path. A pressure release mechanism that opens the confluence channel to the tank, and when the pressure oil is supplied to the actuator by the auxiliary switching valve, the differential pressure generated before and after the flow control throttle is kept constant by the flow control valve On the other hand, when the preliminary switching valve is neutral, the merging flow path is opened to the tank by a pressure release mechanism.
[0011]
The second invention is characterized in that the pressure release mechanism in the first invention is composed of a flow control valve and a control cylinder for controlling the elastic force of a spring provided in the flow control valve.
According to a third invention, the pressure release mechanism according to the first invention includes a pilot check valve connected to the merging flow path so as to bypass the flow control valve, and a pilot line that guides the pilot pressure to the pilot check valve. It is characterized by comprising.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The first embodiment shown in FIG. 1 includes first to third pumps P1 to P3, and first to third circuit systems A to C are connected to each of the first to third pumps P1 to P3. is doing.
In the first circuit system A, open center type first to third switching valves 21 to 23 are connected in parallel to a first supply flow path 30 connected to a first pump P1. These first to third switching valves 21 to 23 communicate the first pump P1 and the tank flow path 40 via the first neutral flow path 31 when in the neutral position shown in the figure. When one of the switching valves is switched, the pressure oil is supplied via the first parallel flow path 32 to an actuator (not shown) connected to the switching valve.
The maximum discharge amount of the first pump P1 is set based on the maximum required flow rate in the three actuators connected to the first to third switching valves 21 to 23.
[0013]
In the second circuit system B, open center type fourth and fifth switching valves 24 and 25 are connected in parallel to the second supply flow path 33 connected to the second pump P2. When the fourth and fifth switching valves 24 and 25 are in the illustrated neutral position, the second neutral flow path 34 is opened and any one of the switching valves is switched. Pressure oil is supplied to the actuator via the second parallel flow path 35.
The maximum discharge amount of the second pump P2 is set based on the maximum required flow rate in the two actuators connected to the fourth and fifth switching valves 24 and 25.
[0014]
Further, the downstream side of the second neutral channel 34 connects the discharge channel 41 and the third neutral channel 37 of the third circuit system B. A flow rate control valve 42 is connected to the discharge channel 41.
The function of the flow control valve 42 will be described later.
[0015]
On the other hand, in the third circuit system C, open center type seventh to ninth switching valves 27 to 29 are connected in parallel to the third supply flow path 36 connected to the third pump P3.
When the seventh to ninth switching valves 27 to 29 are also in the neutral position shown in the figure, the third neutral flow path 37 is opened and any one of the switching valves is switched. Pressure oil is supplied to the actuator via the third parallel flow path 38.
Further, the maximum discharge amount of the third pump P3 is set based on the maximum required flow rates of the three actuators connected to the seventh to ninth switching valves 27 to 29.
[0016]
A standby switching valve 26 is connected to the third neutral flow path 37 downstream of the ninth switching valve 29. The spare switching valve 26 is used to connect the actuator when there is a special actuator in the construction vehicle. When the switching valve 26 is switched to either one, the spare switching valve 26 passes through a flow control throttle 43 provided in the internal flow path. Supply pressure oil to the actuator. The flow control throttle 43 is composed of a variable orifice that keeps its opening according to the valve stroke of the auxiliary switching valve 26.
Further, the standby switching valve 26 blocks the actuator port and opens the third neutral flow path 37 at the neutral position shown in the figure. At this time, the pressure oil guided to the third neutral channel 37 is guided to the flow rate control valve 42 via the discharge channel 41.
[0017]
The flow rate control valve 42 has one pilot chamber 42 a connected to the discharge passage 41 via the first pilot line 45, and the other pilot chamber 42 b provided with the spring 47 is connected via the second pilot line 46. Connected to the flow path 44.
A rod of the control cylinder 50 is connected to one end of the spring 47. A pilot pressure is introduced into the bottom chamber of the control cylinder 50 from the outside via a pilot line 51.
A branch line 52 is connected to the pilot line 51, and this branch line 52 is connected to the pilot port of the standby switching valve 26. This pilot port communicates with the tank flow path 40 via the other pilot port when the auxiliary switching valve 26 is in the neutral position shown in the figure. Is done.
[0018]
When the communication between the branch line 52 and the tank flow path 40 is cut off as described above, the pressure of the pilot line 51 rises and the rod of the control cylinder 50 extends due to the pressure action. When the rod is extended, the spring 47 is contracted, and a predetermined elastic force acts on a spool (not shown) of the flow control valve 42. When a predetermined elastic force by the spring 47 acts on the spool, the flow control valve 42 performs its control function. That is, the control function of the flow rate control valve 42 is exhibited only when the auxiliary switching valve 26 is switched, and the control function of the flow rate control valve 42 is not exhibited at other times.
[0019]
For example, as shown in the figure, if all the switching valves 21 to 29 are in the neutral position, the pressure oil discharged from the second and third pumps P2 and P3 is supplied to the flow control valve 42 via the discharge passage 41. Led. At this time, since the auxiliary switching valve 26 is in the neutral position, the elastic force of the spring 47 does not act on the spool of the flow control valve 42, and the control function is not exhibited.
[0020]
Therefore, when the pressure oil is guided from the discharge flow path 41 to the pilot chamber 42a of the flow control valve 42 via the pilot line 45, the flow control valve 42 maintains the open position, and the pressure oil guided to the discharge flow path 41 is removed. It is discharged to the tank channel 40 as it is.
That is, when the special actuator connected to the spare switching valve 26 is not operated or when the special actuator is not connected to the spare switching valve 26, the pressure oil of the second and third pumps P2 and P3 is used as it is. By discharging, generation of pressure loss in the flow control valve 42 is prevented.
[0021]
On the other hand, when the auxiliary switching valve 26 is switched in any direction from the above state, the third neutral flow path 37 and the flow path 44 are changed in accordance with the opening degree through the flow control throttle 43 provided therein. Communicate. Therefore, the pressure oil guided to the third neutral flow path 37 is supplied to the actuator via the flow rate control throttle 43 → the flow path 44 formed of a variable orifice.
Here, the third neutral flow path 37 communicates with the second neutral flow path 34 of the second circuit system B. Therefore, the total flow rate of the pressure oil of the second pump P2 and the pressure oil of the third pump P3 is guided to the actuator.
[0022]
However, when a flow occurs in the flow control throttle 43 as described above, a differential pressure is generated before and after the flow control throttle 43 according to the opening degree. Then, the pressure on the upstream side of the flow control throttle 43 is guided to one pilot chamber 42a of the flow control valve 42 via the first pilot line 45, and the pressure on the downstream side of the flow control throttle 43 is changed to the second pilot. The flow rate control valve 42 provided with a spring 47 is guided to the other pilot chamber 42b via a line 46.
At this time, the flow rate control valve 42 is in a state of performing its control function because the auxiliary switching valve 26 is switched. That is, a predetermined elastic force of the spring 47 acts on the spool of the flow control valve 42.
[0023]
Therefore, the flow control valve 42 adjusts the opening degree so as to keep the differential pressure before and after the flow control throttle 43 constant. In this way, the actuator connected to the auxiliary switching valve 26 is supplied with a constant flow rate determined by the current flow path area of the flow control throttle 43 and the differential pressure corresponding to the elastic force of the spring 47. Will be.
[0024]
As described above, according to the first embodiment, the opening degree of the flow control throttle 43 provided in the internal flow path of the auxiliary switching valve 26 and the spring 47 of the flow control valve 42 provided in the discharge flow path 41 are adjusted. By adjusting the spring force, the maximum flow rate supplied to the actuator connected to the auxiliary switching valve 26 can be freely set and adjusted.
Therefore, the optimum maximum supply flow rate can be set and adjusted according to the type of actuator.
The spring 47 of the first embodiment corresponds to the pressure setting mechanism of the present invention.
Further, the second neutral flow path 34 on the downstream side of the fifth switching valve 25 and the third neutral flow path 37 on the downstream side of the ninth switching valve 29 constitute the merge flow path of the present invention. Yes.
[0025]
In the first embodiment, the control cylinder 50, the pilot line 51, and the branch line 52 constitute the pressure release mechanism of the present invention. This pressure release mechanism is constituted by the pilot check valve 54, which is shown in FIG. The second embodiment shown in FIG.
In this second embodiment, instead of the control cylinder 50, a pilot check valve 54 is connected so as to bypass the flow control valve 42 at the junction of the second neutral flow path 34 and the third neutral flow path 37. . The pilot check valve 54 is kept closed when a predetermined pilot pressure is introduced from the outside through the pilot line 51.
[0026]
However, a branch line 52 is connected to the pilot line 51, and this branch line 52 is connected to the pilot port of the standby switching valve 26. When the standby switching valve 26 is in the neutral position, the pilot line 51 is communicated with the tank flow path 40 so that the pilot check valve 54 is opened.
According to the second embodiment, when the standby switching valve 26 is in the neutral position and the communication between the actuator and the third neutral flow path 37 is blocked, the pressure oil in the third supply flow path 37 is removed. Without passing through the flow control valve 42, the fuel is discharged directly to the tank flow path 40 via the pilot check valve 54.
Accordingly, it is possible to prevent occurrence of pressure loss in the flow control valve 42 when the standby switching valve 26 is in the neutral position.
[0027]
In the second embodiment, the spring 47 corresponds to the pressure setting mechanism of the present invention. The elastic force of the spring 47 is adjusted by an adjuster bolt or the like so that the elastic force acting on the flow control valve 42 can be adjusted.
However, a proportional solenoid or an external pilot pressure may be used as the pressure setting mechanism of the present invention. If a proportional solenoid or an external pilot pressure is used, the thrust applied to the flow control valve 42 can be easily adjusted from the outside even after the apparatus is incorporated in the vehicle.
[0028]
【The invention's effect】
According to this invention, the differential pressure before and after the flow control throttle provided in the flow path for supplying pressure oil to the actuator of the standby switching valve is configured to be kept constant by the flow control valve. If the pressure of the pressure setting mechanism of the flow control valve is adjusted, the maximum supply flow rate supplied to the actuator can be freely set and adjusted.
Therefore, the operation of the actuator connected to the standby switching valve can be easily controlled.
In addition, a pressure release mechanism is provided to make the junction flow path the tank pressure when the standby switching valve cuts off the communication between the actuator and the merge flow path, preventing pressure loss in the flow control valve when the actuator is not used. can do.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a first embodiment.
FIG. 2 is a circuit diagram of a second embodiment.
FIG. 3 is a circuit diagram of a conventional example.
[Explanation of symbols]
A to C Circuit systems P1 to P3 Pumps 21 to 25, 27 to 29 Switching valve 26 Preliminary switching valve 34 Second neutral flow path 37 constituting the merge flow path of the present invention The third neutral flow path constituting the merge flow path of the present invention Neutral flow path 41 Discharge flow path 42 Flow control valve 42a One pilot chamber 42b of the flow control valve The other pilot chamber 43 of the flow control valve 43 Flow control throttle 45 First pilot line 46 Second pilot line 47 Pressure setting mechanism of the present invention A spring 50 corresponding to the control cylinder 51 constituting the pressure relief mechanism of the present invention Pilot line 52 constituting the pressure relief mechanism of the invention Branch line 54 constituting the pressure relief mechanism of the invention Constituting the pressure relief mechanism of the invention Pilot check valve

Claims (3)

A circuit system comprising a plurality of pumps, an open center type switching valve connected to each pump, a merging channel that merges the most downstream of these circuit systems, and a standby switching valve provided in the merging channel; A flow control throttle provided in a flow path for supplying pressure oil to the actuator of the preliminary switching valve, a discharge flow path communicating the merge flow path and the tank, a flow control valve provided in the discharge flow path, A pressure setting mechanism for setting the pressure on the upstream side of the flow control valve; a first pilot line for guiding pressure generated on the upstream side of the flow control throttle to one pilot chamber of the flow control valve; The second pilot line that guides the pressure generated on the downstream side of the flow control throttle to the other pilot chamber of the flow control valve, and the auxiliary switching valve shut off the communication between the actuator and the merge flow path. A pressure release mechanism for opening the path to the tank, and when the pressure oil is supplied to the actuator by the spare switching valve, the differential pressure generated before and after the flow control throttle is kept constant by the flow control valve, A hydraulic control device characterized in that, when the switching valve is neutral, the confluence channel is opened to the tank by a pressure release mechanism. 2. The hydraulic control apparatus according to claim 1, wherein the pressure release mechanism includes a flow control valve and a control cylinder that controls an elastic force of a spring provided in the flow control valve. 2. The pressure release mechanism includes a pilot check valve connected to the merging flow path so as to bypass the flow control valve, and a pilot line for introducing pilot pressure to the pilot check valve. Hydraulic control device.

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