JPS60258336A - Joining circuit for construction vehicle - Google Patents

Abstract

PURPOSE:To simplify a piping, by a method wherein joining control valves, the one of which allows one-way flow only during lifting of a boom and the other of which allows a reverse flow during non-lifting of the arm are located in a line through which boom control valves, being the one valve group, and the upperstream of arm control valves being the other valve group are intercommunicated with each other. CONSTITUTION:Plural control valves 7 and 8, including a boom control valve 9, are connected in parallel to a variable volumn pump P1, and plural control valves 10 and 11, including an arm control valve 12, are connected in parallel to a variable volume pump P2. The control valves 7-12 are controlled by means of a pilot pressure, and regulators 40 and 41 of a pump are also controlled by means of the pilot pressure. Further, the upperstream of the boom control valve is communicated with that of the arm control valve through a communicating passage 50, and 2 joining control valves 51 and 52 are situated in the communicating passage 50. The one joining control valve 51 is opened only during lifting of the boom, and the flow to the arm is throttled by the other joining control valve 52 during non-lifting of the boom.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention connects a pump to each of a plurality of circuit systems, and connects the pump discharge fluid of one circuit system to the discharge fluid of the pump of the other circuit system. This invention relates to a merging circuit for a construction vehicle that supplies the actuator with the merging circuit of the construction vehicle.

(Conventional merging circuit) Figure 4 shows a conventional merging circuit for power excavators.
A travel motor, a bucket cylinder 2, and a boom cylinder 3 are connected to one circuit system, and a travel motor 4, a swing motor 5, and an arm cylinder 6 are connected to the other circuit system.

Closed center type switching valves 7 to 9 and 10 to 12 are connected to each of the actuators, and a variable displacement pump P1 is connected to one circuit system, and a variable displacement pump P1 is connected to the other circuit system. P2 is connected.

A main relief valve 14 is connected to the pump passage 13 of the variable displacement pump P of one circuit system, and the switching valves 7 to 9 are connected in parallel via a parallel passage 15 connected to this pump passage 13. Connected.

Similarly, a main relief valve 17 is connected to the pump passage 16 of the variable displacement pump P2 in the other circuit system, and a parallel passage 1 connected to this pump passage 18 is connected.
The switching valves 10 to 12 are connected in parallel via 8.

Pilot operation mechanisms 19-21 and 22-24 corresponding to each switching valve are provided in both circuit systems as described above. These pilot operating mechanisms generate a pilot pressure proportional to the amount of operation at the secondary port of the pressure reducing valve 28, 27 by operating the operating lever 25.

The switching valve is configured to switch in proportion to this pilot pressure.

Furthermore, in the passage connecting each pilot operation mechanism and the pilot chamber of the switching valve, shuttle valves 28 to 30, 31 to
33, and the pilot pressure via these shuttle valves is further connected to the shuttle valves 34 to 36, 37 to
38 to lead to -6 regulator 40.41. Therefore, the variable displacement pumps P, , P2 are:
The discharge amount is controlled in proportion to this pilot pressure.

Further, the shuttle valve 30 provided in the pilot passage of the pilot operating mechanism 21 that controls the boom cylinder 3 is connected to the shuttle valve 39 of the other circuit system via the low pressure relief valve 42. Therefore, when the pilot pressure when operating the pyro return operation mechanism 21 exceeds the set pressure of the low pressure relief valve 42, it is transmitted from the shuttle valve 38 to the regulator 41.

Furthermore, the shuttle valve 33 provided in the pilot passage of the pilot operating mechanism 24 that controls the arm cylinder 6 also
It is connected to a shuttle valve 36 of one circuit system via a low pressure relief valve 43, so that the pilot pressure is transmitted from the shuttle valve 36 to the regulator 40.

The arm merging control valve 44 is installed at the most downstream side of the parallel passage 15 in one of the circuit systems, and the boom merging control valve 45 is installed at the same downstream position in the other circuit system.
It is connected to the switching valve on the upstream side.

The pilot chamber of this arm merging control valve 44 is communicated with the pilot chamber of the switching valve 12 that switches the arm cylinder 6. Therefore, if the pilot operating mechanism 24 is operated to switch the switching valve 12, this arm merging control valve 44 will also be switched.

As described above, when the pilot pressure becomes equal to or higher than the set pressure of the low pressure relief valve 43, that pilot pressure is selected by the shuttle valve 36 and acts on the regulator 40, so that any of the seven actuators in this one circuit system is Even if it is not operating, the variable displacement pump P1 discharges the flow rate required by the arm cylinder 6.

Therefore, the discharge fluid of one variable displacement pump Pl passes through the pump passage 13 → parallel passage 15 → arm merging control valve 44 → passage 4B or 47, and joins with the discharge fluid of the other variable displacement pump P2. and flows into the arm cylinder 6.

On the other hand, the pilot chamber of the boom merging control valve 45 is communicated with the pilot chamber of the switching valve 9 for switching the boom cylinder 3. Therefore, if the pilot operation mechanism 18 is operated to switch the switching valve 9, this boom merging control valve 45 is also switched.

In this case as well, when the pilot pressure becomes equal to or higher than the set pressure of the low pressure relief valve 42, the pilot pressure acts on the regulator 41, so that the variable displacement pump P2 operates even if the actuator of the other circuit system is activated. Even if the boom cylinder 3 is not used, the flow rate required by the boom cylinder 3 is discharged.

Therefore, the fluid discharged from the other variable displacement pump P2 passes through the passage 48 or 49, merges with the fluid discharged from the one variable displacement pump P1, and is supplied to the boom cylinder 6.

(Problems to be Solved by the Invention) In the conventional merging circuit as described above, two merging control valves 44 and 45 are required for each circuit system, and this increases the number of pipes. However, there was a drawback that the overall structure became larger and the cost increased.

For example, when the arm cylinder 6 is driven and the arm 5 confluence control valve 44 is switched, if the load on this arm cylinder is low, the pump P of one circuit system
Since all of the discharged fluid flows to the arm cylinder side via the merging control valve 44, there is a drawback that the actuator of one circuit system does not operate. This also applies to the case where the boom cylinder 3 is driven.

This invention eliminates the drawbacks of the above-mentioned prior art. It does not require a merging control valve in each circuit system, reduces the number of piping, reduces the overall size, reduces costs, and reduces the need for simultaneous operation. The purpose of the present invention is to provide a merging circuit for construction vehicles that allows each actuator to operate reliably.

(Means for Solving the Problems) In order to achieve the above object, the present invention has a plurality of closed center type variable displacement pumps connected to each of a pair of circuit systems via parallel passages. Connect the switching valves, connect a boom cylinder to the specified switching valve of one circuit system, connect an arm cylinder to the specified switching valve of the other circuit system, and connect it to the specified switching valve of the above circuit system. In a confluence circuit for a construction vehicle that is equipped with a pilot operating mechanism and is configured to guide the pilot pressure generated when the pilot operating mechanism is operated to the regulator of the variable displacement pump, the parallel passages of the two circuits are connected to a communicating path. A pair of merging control valves are arranged in series in this communication path, and one merging control valve is
When raising the boom cylinder, maintain a position with a check valve that only allows flow from one circuit system to the other, allowing flow from one circuit system to the other, except when the boom cylinder is raised. The other merging control valve is held in a position that allows flow to the circuit system, and the other merging control valve is held in a restricting position when any actuator in one circuit system is operated, except when the boom cylinder is raised. However, when the boom cylinder is raised and when neither actuator of one circuit system is operated, a configuration is adopted in which a free flow position is maintained in either direction with respect to both circuit systems.

(Effect of the present invention) Therefore, when the arm cylinder of the other circuit system is operated without operating the 7-actuator of one circuit system, the discharge fluid of the variable displacement pump of one circuit system is Flows into the arm cylinder.

In addition, when raising the boom cylinder, one of the merging control valves maintains the check valve position to prevent pressure fluid from one circuit system from flowing into the other circuit system. of pressurized fluid can join the boom cylinder.

Furthermore, except for the raising of the boom cylinder, when the actuator of either circuit system is activated, both circuit systems communicate through the converging position of the other merging control valve, so that one circuit system actuator can be activated preferentially.

(Embodiment of the present invention) FIGS. 1 to 3 are circuit diagrams showing an embodiment of the present invention, and the same reference numerals are used for the same components as in the conventional case of FIG. A detailed explanation thereof will be omitted.

In the embodiment shown in FIG. 1, the parallel passage 15 of one circuit system on the variable displacement pump P1 side and the parallel passage 18 of the other circuit system on the variable displacement pump P2 side are communicated via a communication passage 50. A pair of merging control valves 51 and 52 are provided in series in this communication path 50.

In addition, the parallel passage 15 of one circuit system is slightly upstream of the connection port of the most downstream switching valve 9, and the parallel passage 18 of the other circuit system is located slightly upstream of the connection port of the most downstream switching valve 9.
Slightly upstream of the connection port 2, check valves 53 and 54 for preventing backflow are provided.

The pilot pressure that acts on the switching valve 9 when the boom cylinder 3 is raised is guided into the pilot chamber 51a of the merging control valve 51, but when this pilot pressure is not acting, By the action of a spring 55 installed on the opposite side from 51a, the position W, which is the lower side in the drawing, is maintained, allowing free flow from at least one circuit system to the other circuit system. On the other hand, when the boom cylinder 3 is raised, the pilot pressure at that time acts on the pilot chamber 51a, and the merging control valve 51 is switched to the position X where the check valve is located on the upper side of the drawing. When this position X is held, only flow from the other circuit system to one circuit system is allowed.

The other merging control valve 52 has a pilot chamber 52a connected to the shuttle valve 36, and is further provided with a spring 56 on the opposite side of the pilot chamber 52a. It is connected to the pilot room 51.a.

When the pilot pressure is not acting on the pilot chamber 52a, the merging control valve 52 is activated by the spring 5.
6 maintains the position y where both circuit systems can flow freely in either direction. In addition, the pilot room 52
The pressure receiving areas of both chambers 52a and 52b are set so that the merging control valve 52 maintains the position y even when pilot pressure acts on both the spring chamber 52a and the spring chamber 52b.

On the other hand, when the pilot pressure acts only on the pilot chamber 52a, the merging control valve 52 is
6, the position 2 with the constriction is held, and a constriction resistance is applied to the fluid passing through the flow path.

Therefore, in a state in which none of the seven actuators of one circuit system is operated, in other words, in a state in which the pilot operating mechanism of one circuit system is not operated, pilot pressure is not applied to both pilot chambers 51a and 52a. Since there is no action, the merging control valves 51, 52 maintain the positions w, y shown.

In this state, in order to operate the arm cylinder 6, the pilot operating mechanism 24 is operated to generate pilot pressure, and in order to increase the operating speed, the pilot pressure is set to be higher than the set pressure of the low pressure relief valve 43. Then,
The pyropressure acts on the regulator 40 of one variable displacement pump P1, causing the pump PI to discharge a flow rate commensurate with the pilot pressure. The fluid discharged from this one pump P1 flows from the main passage 13 to the parallel passage 15.
→ Backflow prevention check valve 53 → Flows into arm cylinder 6 via positions W and y of merging control valve 51 and 52.

When the packet cylinder 2 is operated simultaneously while performing arm merging control as described above, this packet cylinder 2
Even if the load on the arm cylinder 6 is lower than the load on the arm cylinder 6, the check valve 53 for preventing backflow functions, so that the pressure fluid from the other circuit system does not flow into the packet cylinder 2. Therefore, the pressure fluids of both circuit systems merge into the packet cylinder, and the packet cylinder? This avoids the danger of operating at an unexpected speed.

Further, even when the swing motor 5 is operated simultaneously while performing the arm merging control, and the load on the swing motor 5 is lower than the load on the arm cylinder 6, the backflow prevention check valve 54 functions. Similarly to the above, the swing motor 5 is prevented from operating at an unexpected speed.

Further, if the pilot operation mechanism 21 is operated to switch the switching valve 3 and raise the boom cylinder 3, the pilot pressure at that time is
1a, and the pilot chamber 52a and spring chamber 52b of the merging control valve 52. For this purpose, as shown in FIG. 3, one of the merging control valves 51 is switched against the spring 55 to maintain the position
holds the position y shown.

Note that when the boom cylinder 3 is raised as described above, if other actuators are activated at the same time, the merging control valve 5
Since the pyroft pressure also acts on the spring chamber 52b of No. 2, the merging control valves 51 and 52 are moved to the position X shown in FIG.
and y remain unchanged.

When the merging control valves 51 and 52 hold positions x and y as described above, the check valve at position X functions, so
Only flow from the other circuit system to one circuit system is allowed.

Therefore, when the pilot operation mechanism 21 is operated as described above, the discharge fluid of one variable displacement pump P1 flows into the boom cylinder 3, and the discharge fluid of the other variable displacement pump P2 flows from the main passage 16 to It merges into the boom cylinder 3 via the passage 18 → backflow prevention check valve 54 → position y of the merging control valve 52 → position X of the merging control valve 51.

At this time, even if the arm cylinders 6 of the other circuit system are operated at the same time and the load on the arm cylinders 6 is low, the check valve at position X of the merging control valve 51 functions and the pressure fluid on the boom cylinder 3 side is , does not flow into the arm cylinder 6.

Note that a throttle may be provided in parallel to the check position of the merging control valve 51 so that the excess flow supplied to the boom cylinder 3 flows to the other circuit system. In this way, it is possible to prevent the occurrence of shock caused by the above-mentioned excessive flow.

Furthermore, when any pilot operating mechanism is operated, except for raising the boom cylinder 3 in one circuit system, the pilot pressure at that time is changed to the merging control valve 5.
It acts only on the second pilot chamber 52a. therefore,
As shown in FIG. 2, one merging control valve 51 maintains position W, and the other merging control valve 52 maintains position 2.

In this state, the surplus flow rate for one circuit system flows into the arm cylinder 6. In other words, the actuator of one circuit system is activated preferentially.

(Effects of the present invention) In this invention, the parallel paths of both circuit systems are communicated via a communication path, and a pair of merging control valves are provided in this communication path. Piping can be simplified.

[Brief explanation of drawings]

Drawings 1 to 3 show examples of this invention.
FIG. 1 is a circuit diagram, FIGS. 2 and 3 are partial circuit diagrams showing switching conditions of the merging control valve, and FIG. 4 is a conventional circuit diagram. Pl, P2...Variable capacity pump, 3...Boom cylinder, 6...Arm cylinder, 7-12...Switching valve, 15, 18...Parallel passage, 18-24...
Nokuirot operation mechanism, 51.52... Merging control valve. Representative Patent Attorney Yoshiyuki Shima

Claims (1)

[Claims] A variable displacement pump connected to each of a pair of circuit systems,
A plurality of closed center switching valves are connected via parallel passages, a boom cylinder is connected to a designated switching valve in one circuit system, and an arm cylinder is connected to a designated switching valve in the other circuit system. At the same time, a pilot operating mechanism is provided corresponding to each switching valve, and the pilot pressure generated when operating this pilot operating mechanism is
In a construction vehicle merging circuit configured to also lead to the regulator of the variable displacement pump, the parallel passages of both circuits are connected via a communication passage, and a pair of merging control valves are arranged in series in this communication passage. When the boom cylinder is raised, one of the merging control valves is held in a position with a check valve that only allows flow from the other circuit system to one circuit system, and when the boom cylinder is raised. The other merging control valve shall not actuate any actuator in one circuit except when the boom cylinder is raised. when the boom cylinder is raised and neither actuator in one circuit system is activated.
A construction vehicle merging circuit configured to maintain a free flow position in either direction for both circuit systems.