JP3820334B2 - Hydraulic circuit for construction vehicles and valve structure used therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a construction vehicle circuit that guarantees straight traveling of a vehicle when the construction vehicle travels while raising and lowering an excavator, for example, and a valve structure used for the circuit.
[0002]
[Prior art]
As this type of circuit, one shown in FIG. 5 has been conventionally known. This conventional circuit includes first to third pumps P1 to P3, and a first to third circuit system is connected to each of the first to third pumps P1 to P3.
Connected to the first circuit system connected to the first pump P1 are a traveling switching valve 1 for controlling the left traveling motor 1, a boom switching valve 2 for controlling the boom cylinder, and a bucket switching valve 3 for controlling the bucket cylinder. is doing.
The second circuit system connected to the second pump P2 includes a travel switching valve 4 for controlling the right traveling motor, an arm switching valve 5 for controlling the arm cylinder, and a swing switching valve 6 for controlling the swing cylinder. A service switching valve 7 for controlling the service actuator is connected.
The service actuator is an actuator that is attached to a construction vehicle as necessary.
[0003]
Further, a communication valve V, a blade switching valve 8 for controlling the blade cylinder, and a turning switching valve 9 for controlling the turning motor are connected to the third circuit system connected to the third pump P3 from the upstream side. .
The communication valve V forms a pump port 10 that communicates with the third pump P3, and also includes a neutral port 11, a parallel port 12, and a first merging port that communicate with the pump port 10 and block the communication. 13 and the second merging port 14 are formed.
[0004]
When the communication valve V is in the illustrated normal position, the pump port 10 communicates with the neutral port 11 and the parallel port 12. When pilot pressure is applied to the pilot chamber 15 of the communication valve V and is switched, the communication between the pump port 10 and the neutral port 11 is interrupted, while the pump port 10, the parallel port 12, The first merge port 13 and the second merge port 14 communicate with each other.
[0005]
The neutral port 11 configured as described above communicates with the neutral flow path 16. This neutral flow path 16 communicates with the switching valve 7 of the second circuit system via the third junction passage 17 when the switching valves 8 and 9 are in the illustrated neutral position. When the switching valve 7 is in the neutral position shown in the figure, the third merging passage 17 communicates with the tank flow path 18 via the switching valve 7. Therefore, if the switching valves 8 and 9 and the switching valve 7 are in the neutral position shown in the figure, the oil discharged from the third pump P3 is bleed-off via the switching valves, the neutral flow path 16 and the tank flow path 18. Will be.
[0006]
When the switching valves 8 and 9 of the third circuit system are kept in the neutral position and the service switching valve 7 of the second circuit system is switched, the discharge oil of the third pump P3 is changed to the discharge oil of the second pump P2. And then supplied to the service actuator.
[0007]
A pilot pressure is guided from an external pressure source to the pilot chamber 15 provided in the communication valve V. The pressure oil introduced into the pilot chamber 15 passes through the pilot line 19 to the pilot ports 20 to 22 of the switching valves 1 to 3 in the first circuit system and the switching valves 4 to 6 in the second circuit system. It is also led to pilot ports 23-25. These pilot ports 20 to 25 communicate with the tank flow path 18 when the switching valves 1 to 6 are in the neutral position.
[0008]
The pilot ports 20 and 23 of the travel switching valves 1 and 4 are connected in parallel. Therefore, the pilot line 19 communicates with the tank flow path 18 unless both the travel switching valves 1 and 4 are switched simultaneously and any one of the other switching valves is switched. If the pilot line 19 communicates with the tank flow path 18, no pilot pressure is generated in the pilot chamber 15. Since no pilot pressure is generated in the pilot chamber 15, the communication valve V maintains the illustrated normal position in this case.
[0009]
From the above state, the pilot line 19 is switched by switching both the switching valves 1 and 4 for traveling and any one of the switching valves 2, 3, 5 and 6 of the first circuit system and the second circuit system. Communication with the tank channel 18 is blocked. Therefore, the pilot pressure acts on the pilot chamber 15 of the communication valve V, and the communication valve V is switched to the switching position.
When the communication valve V is switched to the switching position, the communication between the pump port 10 and the neutral port 11 is blocked, while the pump port 10, the parallel port 12, the first merging port 13, and the second merging port 14 Communicate.
[0010]
When the pump port 10 and the parallel port 12 communicate with each other, the pressure oil from the third pump P3 is supplied to the blade switching valve 8 and the turning switching valve 9 through the parallel passage 26.
When the pump port 10 and the first merging port 13 communicate with each other, the pressure oil from the third pump P3 passes through the first merging passage 27 and the boom switching valve 2 and the bucket switching valve 3 in the first circuit system. To be supplied.
If the pump port 10 and the second merging port 14 communicate with each other, the pressure oil from the third pump P3 passes through the second merging passage 28 and the arm switching valve 5 and the swing switching valve 6 in the second circuit system. To be supplied.
[0011]
That is, when simultaneously operating the actuators of the first and second circuit systems while simultaneously switching the travel switching valves 1 and 4, the first and second pumps P 1 and P 2 supply pressure oil only to the travel switching valves 1 and 4. Thus, the other actuator is supplied with pressure oil from the third pump P3 to compensate for the straight traveling of the vehicle.
[0012]
[Problems to be solved by the invention]
In the conventional hydraulic circuit as described above, when the switching valves 8 and 9 of the third circuit system are set to the neutral position and the discharge oil of the third pump P3 is returned to the tank passage 18, the pressure oil is changed over to the switching valve. There was a problem that the pressure loss inevitably increased because it had to pass through 8 and 9.
In addition, when the switching valves 8 and 9 of the third circuit system are kept at the neutral position, there is a problem that if the switch valve is mistakenly switched, the blade cylinder, the turning motor, etc. are inadvertently operated.
The object of the present invention is to minimize the pressure loss when bleed-off the discharge oil of the third pump and prevent the actuator from operating even if the switching valve of the third circuit system is inadvertently switched. To provide a hydraulic circuit for construction vehicles and a valve structure used therefor.
[0013]
[Means for Solving the Problems]
1st invention is provided with the 1st pump-the 3rd pump, and the 1st circuit system connected to the 1st pump has the change-over valve for driving which controls either the right or left traveling motor, and other than this traveling motor And one or more switching valves for controlling the actuator. In addition, the second circuit system connected to the second pump includes a travel switching valve for controlling either the left or right travel motor, and one or a plurality of switch valves for controlling actuators other than the travel motor. Provided. Further, the third circuit system connected to the third pump is provided with one or a plurality of switching valves for controlling actuators other than the traveling motor, while a communication valve is connected to the most upstream of the third circuit system. Yes.
[0014]
The pilot line for guiding the pilot pressure for switching the communication valve is communicated with the tank via the traveling switching valve in the neutral position, and when the traveling switching valve is switched, the pilot line and the tank are connected. The communication is cut off and the pilot pressure is generated. In addition, the communication valve communicates the third pump with the tank at the normal position, and communicates with the neutral flow path connecting the third pump and the predetermined switching valve to the tandem at the first switching position. The switching valve is communicated with a parallel passage connected in parallel, and at the second switching position, the third pump is connected to the parallel passage and the third pump is connected to the first circuit system or the second circuit system. It is made to communicate also with a confluence passage.
[0015]
A second invention is a hydraulic circuit for a construction vehicle in which a traveling motor is driven by a first pump and a second pump, and another actuator during traveling is operated by a third pump. A communication valve is provided in the uppermost stream of the circuit system connected to the pump. The valve body of the communication valve includes a pump port connected to the third pump, a tank port connected to the tank, a parallel port leading the pump port to the parallel passage, and a switching valve connected to the third pump. A neutral port connected to the neutral flow path, a parallel port for connecting in parallel a switching valve connected to the third pump, and a first and second merge communicating with a switching valve connected to a pump other than the third pump A first merge port and a second merge port connected to the passage are formed.
[0016]
On the other hand, a spool configured to maintain the first switching position and the second switching position in addition to the normal position is slidably incorporated in the valve body of the communication valve. The pump port and the parallel port are always communicated regardless of the movement position of the spool, and when the spool is in the normal position, the pump port and the tank port, and the pump port and the neutral port are communicated with each other. When the communication with the first merging passage is blocked and the spool is switched to the first switching position, the communication between the pump port and the tank port is blocked, while the communication between the pump port and the neutral port is maintained, and the second switching position. When switching to, the communication between the pump port and the tank port is blocked, the communication between the pump port and the neutral port is blocked, and the pump port and the first and second merging ports are communicated.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a hydraulic circuit according to an embodiment of the present invention. The greatest feature of this control circuit is that a tank port 29 is provided in the communication valve V, and the pump is operated when the communication valve V is in the illustrated normal position. The port 10 is communicated with the tank port 29. Others are the same as those of the conventional circuit shown in FIG. Therefore, the detailed description of components common to those in the past is omitted, and the same reference numerals are used for the same components.
[0018]
As described above, the communication valve V allows the pump port 10 to communicate directly with the tank flow path 18 via the tank port 29 of the communication valve V when it is kept in the normal position. The pressure loss when returning the oil discharged from the 3-pump P3 to the tank can be minimized.
[0019]
Incidentally, in the conventional case, when the discharge oil of the third pump P3 is returned to the tank passage 18, it must be routed through the neutral ports of the switching valves 8, 9, and 7, so that the pressure loss becomes large. I cannot help it.
However, according to this embodiment, the discharge oil of the third pump P3 is directly returned to the tank flow path 18 via the tank port 29 of the communication valve V as described above, so that there is almost no pressure loss.
[0020]
The valve structure used in the hydraulic circuit is as shown in FIGS.
In the illustrated communication valve V, a spool 31 is slidably incorporated in the valve body 30, one end of the spool 31 faces the pilot chamber 15, and the other end faces the spring chamber 32.
[0021]
Therefore, if no pilot pressure is applied to the pilot chamber 15, the spool 31 maintains the normal position shown in FIG. In this normal position, the pump port 10 and the neutral port 11 communicate with each other via a first annular groove 33 formed in the spool 31. At this time, the pump port 10 communicates with the parallel port 12 via the first flow path 34 formed in the valve body 30. However, the pump port 10 and the parallel port 12 are always in communication regardless of the switching position of the spool 31.
[0022]
When the spool 31 is in the normal position, as shown in FIG. 2, the pump port 10 has the first flow path 34 → the second flow path 35 formed in the valve body → the second annular groove formed in the spool. It communicates with the tank port 29 via 36.
Therefore, when the spool 31 is kept at the normal position, the oil discharged from the third pump P3 is returned from the tank port 29 to the tank flow path 18.
[0023]
When the spool 31 is moved to the left in the drawing against the spring in the spring chamber 32 from the above state and switched to the first switching position shown in FIG. 3, the second annular groove 36 and the second flow path 35 However, since it will be in an underlap state, the communication between the second flow path 35 and the tank port 29 is blocked. In other words, the communication between the pump port 10 and the tank port 29 is blocked.
Further, at the first switching position, the pump port 10 and the neutral port 11 remain in communication. Therefore, in the first switching position, the pump port 10 is kept in communication with both the parallel port 12 and the neutral port 11.
However, the communication between the pump port 10 and the first and second merging ports 13 and 14 remains blocked.
[0024]
When the spool 31 is further moved to the left in the drawing from the first switching position, the communication valve V is switched to the second switching position shown in FIG. At the second switching position, the second flow path 35 and the third flow path 38 communicating with the first merge port 13 communicate with each other via a third annular groove 37 formed in the spool. At the same time, the pump port 10 communicates with the fourth flow path 40 communicating with the second merge port 14 via the fourth annular groove 39 formed in the spool.
In addition, in the second switching position, communication between the pump port 10 and the neutral port 11 is blocked.
Therefore, in this second switching position, the pump port 10 communicates with the parallel port 12, the first joining port 13, and the second joining port 14.
[0025]
The spool 31 is switched to the three positions from the normal position to the second switching position as described above according to the following configuration.
That is, a pilot piston 41 is incorporated in the pilot chamber 15 facing one end of the spool 31. A collar 42 is interposed between the pilot piston 41 and one end of the spool 31. The collar 42 can stroke within the range of the step portion 43.
[0026]
In the pilot piston 41 as described above, an orifice 44 is formed, and the orifice 44 is formed in the spool through an oil passage hole 45 formed in the pilot piston and an oil passage hole 46 formed in the collar. 47 is communicated.
The pilot passage 47 is always in communication with an annular recess 48 formed on the valve body 30 side. The annular recess 48 is in communication with the pilot line 19 described above.
[0027]
Therefore, now, when the pilot pressure is applied to the pilot chamber 15 in the normal state shown in FIG. This state is the first switching position.
At this first switching position, if the pilot line 19 remains open, a flow is generated in the orifice 44, so that the pressure on the downstream side is lowered by the pressure loss. The pressure on the downstream side of the orifice 44 acts on one end of the spool 31, that is, the contact surface with the collar 42. However, at this low pilot pressure, the spool 31 does not move and maintains the first switching position.
[0028]
From the above state, when the both travel switching valves 1 and 4 are switched and one of the switching valves 2, 3, 5, 6 is switched for straight traveling, the pilot line 19 is closed. Since the pilot line 19 is closed, there is no flow before and after the orifice. As a result, the pilot pressure downstream of the orifice also increases. Due to the increased pilot pressure, the spool 31 moves again and is switched to the second switching position.
[0029]
【The invention's effect】
According to the first and second aspects of the invention, the oil discharged from the third pump is directly returned to the tank through the communication valve at the normal position of the communication valve, so that the pressure loss can be minimized. Energy loss is reduced because pressure loss can be minimized.
Further, as long as the communication valve is kept at the normal position, even if the switching valve communicated with the third pump is inadvertently operated, the danger that the actuator connected to the switching valve will be activated can be avoided.
[Brief description of the drawings]
FIG. 1 is a circuit diagram.
FIG. 2 is a cross-sectional view of a state in which a communication valve is maintained at a normal position.
FIG. 3 is a cross-sectional view of a state in which the communication valve is maintained at a first switching position.
FIG. 4 is a cross-sectional view of a state in which the communication valve is maintained at a second switching position.
FIG. 5 is a conventional circuit diagram.
[Explanation of symbols]
P1 to P3 1st to 3rd pumps 1 and 4 Switching valve for travel 5 to 9 Switching valve V Communication valve 10 Pump port 11 Neutral port 12 Parallel port 13 First merge port 14 Second merge port 16 Neutral flow channel 17 Third merge Passage 26 parallel passage 27 first joining passage 28 second joining passage 29 tank port 30 valve body 31 spool

Claims (2)

A first circuit system including a first pump to a third pump, and a first circuit system connected to the first pump for controlling a travel switching valve for controlling one of the left and right travel motors and an actuator other than the travel motor. The second circuit system connected to the second pump is provided with a travel switching valve for controlling either the left or right travel motor and an actuator other than the travel motor. The third circuit system connected to the third pump is provided with one or a plurality of switching valves for controlling actuators other than the travel motor, while the third circuit system is connected to the third pump. A communication line is connected to the uppermost stream, and a pilot line for guiding a pilot pressure for switching the communication valve is connected to the tank via the traveling switching valve in the neutral position. When the switching valve is switched, the communication between the pilot line and the tank is cut off to generate the pilot pressure. In addition, the communication valve communicates the third pump with the tank at its normal position. In the first switching position, the third pump and the predetermined switching valve are communicated with a neutral flow path connected to the tandem, and the predetermined switching valve is communicated with a parallel passage connected in parallel. A construction vehicle hydraulic circuit configured to connect three pumps to the parallel passage and to communicate with a junction passage connecting the third pump to the first circuit system or the second circuit system. A hydraulic circuit for a construction vehicle configured to drive a travel motor with the first pump and the second pump and to operate other actuators during travel with the third pump, the circuit system connected to the third pump A communication valve is provided on the most upstream side of the valve, and a valve port of the communication valve includes a pump port connected to the third pump, a tank port connected to the tank, a parallel port for guiding the pump port to the parallel passage, and a third port. A neutral port connected to the neutral flow path of the switching valve connected to the pump, a parallel port for connecting the switching valve connected to the third pump in parallel, and a switching valve connected to a pump other than the third pump. The first and second merging ports connected to the first and second merging passages are formed, while the valve body of the communication valve has a first position other than the normal position. When the spool configured to maintain the exchange position and the second switching position is slidably incorporated, and the pump port and the parallel port are always in communication regardless of the movement position of the spool, while the spool is in the normal position. When the pump port is connected to the tank port, the pump port is connected to the neutral port, the communication between the tank port and the first merging passage is blocked, and the spool is switched to the first switching position, the communication between the pump port and the tank port is established. While maintaining the communication between the pump port and the neutral port, when switching to the second switching position, the communication between the pump port and the tank port is blocked and the communication between the pump port and the neutral port is blocked. A valve structure in which the pump port and the first and second merge ports communicate with each other.

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