JPH0468413B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a control circuit for a construction vehicle or the like, in which each of a pair of circuit systems includes a travel motor and a work equipment system actuator.

(Prior art) This type of construction vehicle, etc., which has been known in the past,
The actuators of specific work equipment systems are connected in parallel to the travel motor, so that the actuators of the specific work equipment systems can be operated simultaneously while the vehicle is running.

(Problems to be Solved by the Invention) In the above circuit, when the parallel-connected travel motor and work equipment actuator are operated simultaneously, the supply flow rate to the travel motor is higher than the supply flow rate when the drive motor is operated alone. It becomes less, and by that much,
The operating speed of the travel motor becomes slower.

If the operating speed of one of the traveling motors becomes slow in this way, a speed difference will occur between the two traveling motors and the other traveling motor, resulting in a problem that the vehicle will be unable to travel in a straight line.

Further, when the actuator of the work equipment system is under a light load, the hydraulic oil is preferentially supplied to the actuator of the work equipment system, and there is also a problem that a sufficient flow rate is not supplied to the travel motor.

This invention maintains the conventional parallel connection between the travel motor and the actuator of a specific work equipment system, guarantees the straightness of the vehicle, and even when the work equipment actuator is under a light load, the travel motor This ensures that a sufficient flow rate is supplied to the

(Means for Solving the Problems) In order to achieve the above object, the present invention connects a pump to each of a pair of circuit systems, and the most upstream of both circuit systems has a switch for controlling a traveling motor. The switching valve that controls the travel motor and the switching valve that controls the actuator of the work equipment system located downstream of the switching valve that controls the actuator of the work equipment system are connected in tandem, and among the switching valves that control the actuator of the work equipment system, The required switching valves are connected via parallel passages, while a control circuit for a construction vehicle or the like is provided with a selector valve between both pumps and both circuit systems, and the selector valve is connected to both pumps independently. and the position where the discharged oil is led to each circuit system, the discharged oil of one pump is diverted to the above-mentioned switching valve at the most upstream of both circuits, and the discharged oil of the other pump is routed to both circuits or either circuit system. The control position leads to the parallel path of the circuit system.

(Operation of the present invention) According to the present invention, when both pumps are connected to their respective circuit systems independently, the travel motor can be driven preferentially, and the travel motor is not driven. In some cases, the actuator of the work equipment system can also be driven.

Then, when the selector valve is switched to the control position, the oil discharged from one pump is supplied to both travel motors, and the oil discharged from the other pump is supplied to the actuator of the work equipment system. actuators can be driven at the same time.

(Embodiment of the present invention) Pumps P ₁ and P ₂ of the first embodiment shown in FIG.
Via the selector valve V, the switching valves 11 to 1
4, 15 to 18 are connected to each circuit system.

That is, one circuit system includes, from the upstream side, a switching valve 11 that controls the travel motor, a switching valve 12 that controls the bucket cylinder, a switching valve 13 that controls the boom cylinder, and a switching valve that controls the arm merging. It is connected to the valve 14. The most upstream switching valve 11 and the other switching valves 12 to 14 are connected in tandem, and the switching valves 12 and 13 are connected to a parallel passage 19.
The switching valves 13 and 14 are connected in tandem.

When each of the switching valves 11 to 14 as described above is in the neutral position shown, the center bypass passage 20 is opened and the pump P ₁ is connected to the tank T via the center bypass passage 20. Stay loaded.

In addition, the other circuit system described above includes, from the upstream side, a switching valve 15 that controls the travel motor, a switching valve 16 that controls the swing motor, a switching valve 17 for increasing boom speed, and a switching valve 17 that controls the arm cylinder. It is connected to the switching valve 18.

In this other circuit system, the most upstream switching valve 15 and the switching valve 16 located downstream thereof are connected in tandem, while the switching valve 16 is connected in tandem.
18 are connected in parallel via a parallel path 21.

When each of the switching valves 15 to 18 is in the illustrated neutral position, the center bypass passage 22 is opened to maintain the unloaded state.

In addition, the selector valve V described above has 2 positions and 5
It is a port valve, and the first port 2 on the upstream side
Connect to one pump P ₁ of 3 and the second port 24
is connected to the other pump P ₂ . Further, the third and fourth ports 25, 26 on the downstream side are connected to the switching valve 11, the most upstream port, via the pump passages 27, 28.
Connected to 15. And the fifth port 29
is connected to the parallel paths 19 and 21 of both circuit systems via a connecting path 30.

The selector valve V configured as described above is normally maintained at the left position (normal position) shown in the figure by the action of the spring 31. Then, when the selector valve V maintains the above left position,
1st port 23, 3rd port 25, 2nd port 2
4 and the fourth port 26 communicate with each other, and the fifth port 29
closes.

Also, when the operating lever 32 is operated to switch the selector valve V to the right side position, which is the control position, the third and fourth ports 25 and 26 are connected to the first port 23.
The fifth port 29 communicates with the second port 24 .

Therefore, only when the selector valve V is in the right-hand position, the hydraulic oil from the other pump _P2 is
Both parallel passages 19, 2 via the connection passage 30
1. In this connection passage 30, check valves 33 and 34 are provided on both sides of the connection point x with the fifth port 29. , 21 only.

Further, the parallel passages 19 and 21,
A check valve 3 is located closer to the center bypass passages 20, 22 than the introduction passages 35, 36 of the switching valves 12, 16.
7, 38 are provided, but this check valve 37,
38 allows flow only from the center bypass passages 20, 22 to the parallel passages 19, 21.

Note that reference numerals 39 to 41 and 42 to 44 in the figure are load check valves provided on the inlet side of the switching valves 12 to 14 and 16 to 18.

Therefore, when driving the travel motor and the actuator of the working machine system separately, the selector valve V is held at the left position as shown in the figure.

If the selector valve V is held in the left position as shown in the figure, the oil discharged from each pump P ₁ and P ₂ is separately supplied to each circuit system. In other words,
The oil discharged from one pump P ₁ is supplied to the pump passage 27 of one circuit system, and the oil discharged from the other pump P ₂ is supplied to the pump passage 28 of the other circuit system.

In this state, each switching valve 11-14, 15-18
If the pumps P 1 and P 2 are in the neutral position shown in the figure, the oil discharged from the pumps P ₁ and P ₂ will flow into the center bypass passage 2, as described above.
It returns to tank T via 0 and 22 and becomes unloaded.

Then, when the most upstream switching valves 11 and 15 are switched to either the left or right side, communication between the switching valves downstream of this switching valve and the pump is cut off, so that the total discharge amount of the pumps P ₁ and P ₂ is reduced. , are supplied to their corresponding travel motors. That is, in this case, if the travel motor is driven, the other actuators cannot be driven, resulting in a so-called travel priority state.

In addition, with the most upstream switching valves 11, 15 held at the neutral position shown and the travel motor stopped, any switching valve 12, 13, 16, 18 downstream of the switching valves 11, 15 By switching the switching valve, the actuator of the working machine system corresponding to the switching valve can be driven.

When the actuators of the actuator systems of both circuit systems are driven simultaneously, the check valves 33 and 34
Without this, the total discharge amount of both pumps P ₁ and P ₂ would be preferentially supplied to the lightly loaded actuator.
For example, when switching the switching valve 12 to drive the bucket cylinder and switching the switching valve 16 to drive the swing motor, if the bucket cylinder has a lighter load, the total discharge of pumps P ₁ and P ₂ will be The quantity is supplied to the lightly loaded bucketed cylinder through the following route:

That is, the discharge amount of one pump _P1 is supplied to the bucket cylinder via the pump passage 27→switching valve 11→check valve 37→introduction passage 35→load check valve 39→switching valve 12. Also,
The discharge amount of the other pump _P2 is as follows: pump passage 28→
The pressure oil supplied to the parallel passage 21 is supplied to the parallel passage 21 via the switching valve 15 → check valve 38, but if the check valve 34 is not provided as described above, the pressure oil supplied to this parallel passage 21 will be transferred to the connecting passage 30 and the parallel passage. 1
9 and is supplied to the bucketed cylinder with a light load.

Therefore, when the check valves 33 and 34 hold the selector valve V in the left position as shown in the drawing and simultaneously drive the actuators of the working machine systems in both circuit systems, the check valves 33 and 34 operate as follows, regardless of the load on these actuators:
It has a function of supplying the discharge amount of the pump to the actuators of both circuit systems.

However, under the following configuration, the check valves 33 and 34 become unnecessary. That is, a sixth port is formed downstream of the selector valve V, and the fifth port is connected to the parallel passage 1 of one circuit system.
9, and the sixth port is connected to the parallel path 21 of the other circuit system. When the selector valve V is held at the left position shown in the figure, the fifth and sixth ports are closed, but when it is switched to the right position, the oil discharged from the other pump _P2 is
If you make it possible to distribute it to the 5th and 6th ports,
The check valves 33 and 34 mentioned above become unnecessary.

Further, when driving the travel motor and the actuator of the working machine system simultaneously, the selector valve V is switched from the left-hand position to the right-hand position, which is the control position.

When the selector valve V is switched in this way, the oil discharged from one pump _P1 is divided into the third port 25 and the fourth port 26, flows to the switching valves 11 and 15, and the oil discharged from the other pump _P2 flows into the connecting passage 30.

In this state, if the switching valves 11 and 15 are switched,
The oil discharged from one pump _P1 is distributed and supplied to the corresponding travel motor. Since the oil discharged from one pump is distributed in this way, if the loads on both travel motors are equal, the supply flow rates will also be equal, and straight-line travel of the vehicle is guaranteed.

In addition, as described above, the discharge oil from the other pump _P2 flows into the connection passage 30, so the switching valves 12 and 1
When any one of the switching valves 3, 16, and 18 is switched, the actuator of the work equipment connected to that switching valve is connected to the other pump via the parallel passages 19, 21.
P ₂ hydraulic oil is supplied.

In this way, one pump P ₁ is used for the traveling motor.
Since the discharge oil of the other pump _P2 is supplied to the work equipment system actuators other than the travel motor, even if the work equipment system actuators are driven at the same time while traveling, the Therefore, the flow rate supplied to the travel motor does not change. Therefore, the travel motor and other actuators can be driven simultaneously while the vehicle is running, and the straight-line performance of the vehicle is not impaired.

In addition, when the selector valve V is held in the above-mentioned right position and the actuator of the work equipment system of either circuit system is driven, the pump P ₂ will be unloaded if the check valves 37 and 38 are not present. Check valves 37 and 38 are provided to prevent this.

For example, when the selector valve V is held in the right position and only the switching valve 13 of one circuit system is switched to drive the boom cylinder, and the check valve 38 is not present, the connection passage 30 is connected from the fifth port 29. The supplied pressure oil flows from the parallel passage 21 to the other circuit system that is in the unloaded state, and is no longer supplied to the boom cylinder. However, with the check valve 38 as described above, pump _P2 will be supplied to the boom cylinder without being unloaded.

In the second embodiment shown in FIG. 2, when the travel motor and actuator of the work equipment are driven simultaneously, the selector valve V is automatically switched to the right-hand position, which is the control position. . For this purpose, the selector valve V in this second embodiment has the operating lever 3 in the first embodiment.
2, a pilot chamber 45 is provided.

Also, the most upstream switching valve 1 that controls the travel motor
1 and 15, a sub-valve 46 interlocked therewith,
There are 47. This sub-valve 46, 47
The first ports 46a, 47a are connected to a shuttle valve 50 via pilot passages 48, 49, and the shuttle valve 50 is communicated with the pilot chamber 45. Further, the second ports 46b, 47b of the sub-valve are connected to the parallel passages 19, 21, and the third ports 46c, 47b are connected to the parallel passages 19, 21.
7c is connected to tank T.

When the sub-valves 46, 47 configured in this way are in the neutral position shown in the figure together with the switching valves 11, 15, the first ports 46a, 47a and the second port 46
b, 47b, and connect the first port to the tank T via the third ports 46c, 47c. And the switching valve 11,
15, the sub valves 46, 4
When 7 is switched, the first and second ports communicate with each other, and communication between the first and third ports is cut off.

Furthermore, when the switching valves 11 and 15 are switched to either the left or right side, in other words, when the travel motor is driven, a predetermined flow rate is ensured via the orifices 11a and 15a.

Further, logic valves 51 and 52 are connected to the most downstream of both circuit systems, and these logic valves 51 and 52 are operated by springs 53 and 54.
Normally, the open position shown in the figure is maintained, and when pilot pressure is applied to the pilot chambers 51a and 52a, the closed position is maintained. The pilot chamber 51a of the logic valve 51 of one circuit system
is connected to the pilot passage 49 of the other circuit system, and the pilot chamber 52a of the logic valve 52 of the other circuit system is connected to the pilot passage 48 of one circuit system.

Therefore, if only the switching valves 11 and 15 are switched, the traveling motor is driven, but at this time, the switching valve 1
Since the switching valve downstream of 1 and 15 is held at the neutral position, even if there is a bleed flow rate from the orifices 11a and 15a, the parallel passages 19 and 2
No pressure is generated in 1. Therefore, even if the first and second ports of the sub-valves 46 and 47 communicate with each other, no pilot pressure acts on the pilot chamber 45 of the selector valve V, and the selector valve V
maintains the left position in the drawing. In other words, the oil discharged from each of the pumps P ₁ and P ₂ is separately supplied to each travel motor.

Furthermore, when the switching valves 11 and 15 are maintained in the neutral position and the switching valve located downstream of the switching valve is switched to drive the actuator of the working machine system, pressure is generated in the parallel passages 19 and 21. ,
As long as the switching valves 11 and 15 are in the neutral position as described above, communication between the parallel passages 19 and 21 and the pilot passages 48 and 49 remains cut off, so that the pressure generated in the parallel passages 19 and 21 is transferred to the pilot chamber. 45 does not work. That is, even in this state, the selector valve V is held at the left position as shown.

Then, in order to drive the travel motor, the switching valves 11 and 15 are switched to either the left or right, and in order to simultaneously drive the actuator of the work equipment system, the switching valve downstream of the switching valves 11 and 15 is switched. Then, pilot pressure is generated in the parallel passages 19 and 21. For example, in one circuit system, when the switching valve 11 is switched, some bleed flow is supplied from the orifice 11a of the upstream switching valve 11 to the parallel passage 19 side. If the switching valve 12 is switched in this state, pressure will be generated in the parallel passage 19. The pressure generated in this parallel passage 19 is
It acts on the pilot chamber 45 of the selector valve V via the port 46b→first port 46a→pilot passage 48→shuttle valve 50, and switches the selector valve V to the right position in the drawing. Moreover, the pilot pressure is transferred from the pilot passage 48 to the pilot chamber 52 of the logic valve 52 in the other circuit system.
a to switch this logic valve 52 to the closed position.

For example, when the switching valves 15 and 16 in the other circuit system are switched, load pressure is generated in the parallel passage 21, and this load pressure is used as the pilot pressure to transfer the sub-valve 47 from the second port 47b to the first port. 47a → Pilot passage 49 → Shuttle valve 5
0 to the pilot chamber 4 of the selector valve V
5. Furthermore, this pilot pressure also acts on the pilot chamber 51a of the logic valve 51 of one circuit system from the pilot passage 49, switching the logic valve 51 to the closed position.

However, when switching the switching valves 11, 12 and 15, 16 of both circuit systems at the same time, the higher pilot pressure selected by the shuttle valve 50 among the pilot pressures generated in each circuit system will be used. is transmitted to the pilot chamber 45 of the selector valve V.

When the selector valve V is switched to the right position in the drawing as described above, the oil discharged from one pump _P1 is distributed to both travel motors, and the oil discharged from the other pump _P2 is distributed to both drive motors, as in the first embodiment. is supplied to the actuator of the working machine system.

Note that in this second embodiment, the logic valves 51,
52, and as described above, the logic valves 51 and 52 are switched by the pilot pressure of the circuit system on the opposite side of the logic valve, so that the check valve 3 in the first embodiment is
7 and 38 are no longer needed.

For example, when the selector valve V is switched to the right position in the drawing, and the actuator of the operating machine system of one circuit system is driven and the actuator of the other work machine system is stopped, the logic valve 52 of the other circuit system is driven. switches to the closed position, so that pump P ₂
There is no unloading from the center bypass passage 22 of the other circuit system.

The third embodiment shown in FIG. 3 uses pilot pressure to switch the switching valves other than the switching valves 11 and 15 that control the travel motor, and also utilizes the pilot pressure to switch the switching valves. Accordingly, the selector valve V is switched.

That is, in one circuit system, the pilot chamber 12a of the switching valve 12 that controls the bucket cylinder,
A shuttle valve 55 selects the pressure in the pilot chamber 12b, and a shuttle valve 56 selects the pressure in the pilot chambers 13a, 13b of the switching valve 13 that controls the boom cylinder. The pilot pressure selected by the two shuttle valves 55 and 56 is selected by the shuttle valve 57, and the selected pilot pressure is led to the second port 46b of the sub-valve 46. That is, the highest pressure of the pilot pressure acting on both the switching valves 12 and 13 is guided to the second port 46b.

In addition, in the other circuit system, pilot chambers 16a, 16b, 18a,
The highest pilot pressure acting on the pilot pressure 18b is selected by the shuttle valves 58 to 60 and guided to the second port 47b of the sub-valve 47.

The other configurations are the same as those of the second embodiment.

In the fourth embodiment shown in FIG. 4, a sub-valve 47 is provided only in the switching valve 15 of the other circuit system, and the selector valve V is switched only by the pilot pressure of the switching valves 16 and 18 of the other circuit system. In addition, the fifth port 29 of the selector valve V is communicated only with the parallel passage 21 of the other circuit system, and the other configuration is the same as that of the third embodiment.

(Effects of the Present Invention) According to the present invention, the travel motor can always be driven regardless of whether or not the actuator of the working machine system is being driven.

Moreover, when driving the travel motor and the actuator of the work equipment system simultaneously, the oil discharged from one pump is supplied to both travel motors, and the oil discharged from the other pump is supplied to the actuator of the work equipment system. The motor is not affected by actuators in the work equipment system.

Furthermore, in the case of simultaneous driving, the oil discharged from one pump is distributed to both travel motors, so if the loads on the travel motors are equal, the straight-line performance of the vehicle is guaranteed.

[Brief explanation of drawings]

1 to 4 are circuit diagrams of first to fourth embodiments of the present invention. P ₁ , P ₂ ... pump, 11 to 18 ... switching valve,
19, 21... Bypass passage, V... Selector valve, 30... Connection passage, 45... Pilot chamber, 46, 47... Sub valve.

Claims (1)

[Claims] 1 A pump is connected to each of a pair of circuit systems, and the most upstream of both circuit systems is equipped with a switching valve that controls the travel motor, and the switching valve that controls the travel motor and the work machine located downstream of the switching valve The switching valves that control the actuators of the system are connected in tandem, and the required switching valves that control the actuators of the work equipment system are connected via parallel passages. In a control circuit for a construction vehicle, etc., where a selector valve is installed between the pump and A control circuit for construction vehicles, etc., consisting of a control position that distributes oil to the most upstream switching valve of both circuit systems, and directs oil discharged from the other pump to a parallel path of both circuit systems or either circuit system.