JPS6014606A - Circuit for combining two flows - Google Patents

Abstract

PURPOSE:To attain effective utilization of surplus oil, by adding a bypass type pressure compensating valve to a hydraulic system having a throttle changeover valve which closes the pump port at the neutral position thereby combining a surplus flow from the pressure compensating valve to the pump fluid in another circuit. CONSTITUTION:A bypass type pressure compensating valve 8 is connected to the upstream side of a throttle changeover valve 4 which closes the pump port at its neutral position, and the bypass port of the bypass type compensating valve 8 is connected through a check valve 17 with a second circuit 2a. By the described arrangement, the surplus oil from the pump 1 can be combined to the fluid of another pump 2 when the throttle changeover valve 4 is at the neutral position, or when the same is changed over to the direction for operating the actuator. Thus, the effective utilization of the surplus oil can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION In a fluid circuit equipped with two fluid pumps, when a large flow rate is required for a predetermined actuator, the present invention combines the fluids of the two fluid pumps and supplies the fluid. The present invention relates to an improvement of such a two-flow merging circuit.

Conventionally, as this kind of two-flow merging circuit, for example, one shown in FIG. 3 has been known. This thing connects one fluid pump system (a) and the other fluid pump system (b),
Connect at the oil line (d > with check valve (C) interposed,
Each switching valve (e), (f
), (When both (1) are in the neutral position, i, fluid from one fluid pump (11) is transferred to the oil path (d'
), and when the switching valve (j) of the other fluid pump system <b> is in the neutral position, the combined fluid is transferred to the tank ( k), and when the switching valve (J) is switched, the combined fluid is supplied to a predetermined actuator.

However, in the above conventional system, when the switching valve (j > of the other fluid pump system (b) is in the neutral position,
The total flow rate from both fluid pumps (h) and (+) is transferred to the switching valve (
Since the fuel is returned to the tank (k) via the fuel tank (k), the neutral unloading pressure increases, which has the disadvantage of increasing power loss.

Therefore, Japanese Patent Publication No. 51-48231 discloses a circuit that suppresses the neutral unloading pressure to a low level while allowing two flow rates to merge when necessary. As shown in Figure 4, this device consists of two pumps (Q),
(+11>) and one pump (ill
) is a fluid circuit in which a switching valve (n) that wishes to merge is provided in the fluid system of the other pump (ri), and a bypass port (Oo) of the switching valve (O+) and (Oz) belonging to the fluid system of the other pump (ri).
are connected to the inflow pipe (r) of the pump (m) through an outlet pipe (q) provided with a check valve (P) so that they can merge, and the outlet pipe <q ), an unloading valve (S) is connected in the middle of the unloading valve (S), and the pylon 1 to the passage (1) communicating with the spring chamber of the unloading valve (S) is connected to the switching valve (n) of the switching valve (n) where the above-mentioned merging is desired. (U) is connected to the tank return pipe (V), and the switching valve (0+)
, (02) switching valve that desires merging at the neutral position <n)
is in the neutral position, the spring chamber of the unload valve (S) is communicated with the tank return pipe (V) via the switching valve (u), thereby directing fluid from the pump (9) to the unload valve. (S) is unloaded with a low pressure equal to the spring pressure of the spring (W>) placed in the spring chamber, and when the switching valve (n) that desires merging is switched to the actuating direction of the actuator, the associated cutting switching valve (11) closes the pilot flow path (1) of the unload valve (S,) and closes the unloader valve (S), thereby closing the pump (5).
The fluid is pumped (Ill) through the outlet line (q).
The water is supplied to the inflow pipe (r) and merged with the inflow pipe (r).

However, in this case, when the switching valves (for example, (02) and (n)) belonging to the fluid system of each pump (1, (III)) are operated simultaneously, the bypass port (00) is closed. ) to the pump (n), and the fluid in the pump (11) has a predetermined flow rate when the switching valve (0
2), and if there is a surplus flow in the discharged fluid, the surplus flow is not used effectively and is wastedly relieved from the relief valve (X) for the pump (It). was there.

The present invention has been made in view of these points, and the switching valve belonging to the fluid system of one of the pumps is configured with a cut-off switching valve that closes the pump port when in the neutral position, and the fluid system equipped with the throttle switching valve is configured. By adding a bypass type pressure compensation valve to
By allowing the surplus flow from the pressure compensating valve to join the fluid of the other pump, it is possible to avoid this problem at least when the switching valves belonging to the fluid system of one pump are all in the neutral position. The purpose of this invention is to effectively utilize the surplus fluid present in one pump by merging it with the fluid in the other pump even when one of the pumps is turned in the direction of actuator operation.

To achieve this objective, the configuration of the present invention provides a fluid bomb 1
In a fluid circuit comprising a pair of circuits configured to supply fluid to an actuator via a switching valve, the first circuit has a pump port 1 closed in a neutral position, and a tank in a neutral position. A throttle switching valve having a pilot port 1- which communicates with the throttle switching valve and closes when in the switching position, and a bypass type pressure compensating valve that maintains the differential pressure before and after the throttle switching valve at a predetermined pressure are provided. for,
A switching valve is provided with a pilot port that communicates with the tank when in the neutral position and closes when at least the final switching position, and the bypass port of the bypass type pressure compensating valve is provided with:
A bypass passage provided with a check valve communicates with the switching valve of the second circuit, and a spring chamber is connected to the switching valve of the first circuit via a shuttle valve on the discharge boat side of the bypass type pressure compensation valve. and an unload valve that communicates with each pilot boat of the switching valve of the second circuit, and when the switching valve of the first circuit is switched in the operating direction, By opening and closing the pilot boat of the switching valve, the unload valve is closed, and a predetermined flow rate of the fluid from the first pump is supplied to the switching valve through the bypass type pressure compensation valve, and the surplus flow is transferred to the bypass type pressure compensation valve. The second circuit is connected to the second circuit via a bypass passage.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a hydraulic circuit of a truck crane, in which (1) is a first fluid pump, (2) is a second fluid pump, (3) is an elevation switching valve, ( 4) is a switching valve for expansion and contraction, and (5) is a switching valve for hoisting that may require the supply of a large flow m, and each switching valve (3) is for the downward direction 1111 and for expansion and contraction.

In response to the switching operation (4), the fluid from the first fluid pump (1) is supplied to each actuator (not shown) for elevation and extension via the can switching valves (3) and (4), respectively. The first circuit (A) is configured to supply fluid from the second fluid pump (2) to the hoisting switching valve (5) in accordance with the switching operation of the hoisting switching valve (5). J supplied to the hoisting actuator (not shown) via valve (5):
A second circuit (B) is constructed in which the hoisting operation accompanying the switching operation of the hoisting switching valve (5) is controlled by the elevating and extending/contracting operations by fluid supply from a dedicated fluid pump (2). I try to make them independent by burning them.

The respective switching valves (3), <4) for elevation and expansion/contraction of the first circuit <A) are in neutral positions (3a), (4a), respectively.
It consists of a throttle switching valve that closes the pump boats (3p) and (4p) at the same time, and the can switching valves (3) and (4) are each in a neutral position (3a).

Switching positions (3b) located above and below in the figure (4a).

A load pressure detection port (3d>, (4d)) that detects the load pressure at the times of (3c)', (4b), and (4c);
At the neutral position (3a>, (4a), the pilot passage (2
8) communicates with the tank (6) via 85 and the tank return passage (13), while switching positions (3b), (3c
A pilot boat (3e>, (4e) that closes when >, (4b), <4c) is formed, and each of the load pressure detection ports (3'd).

(4d) is configured to communicate with the tank (6) via the pilot passage (7) when in the neutral position (3a), (4a).

In addition, the discharge path (
A preferential expansion pressure compensation valve (8) is interposed in the middle of 1a). The preferential expansion pressure compensation valve (8) is connected to a pump boat (8a) that receives pressure oil supply from the first fluid pump (1), and the above-mentioned elevation and expansion/contraction switching valves (3) and (4). has a priority port (discharge boat) (8b) and a non-priority port (bypass port) (8c) connected in parallel,
The maximum pressure P of the elevation load pressure point and the extension/contraction load pressure is introduced into the spring chamber (8d) at one end, while both the elevation and extension switching valves (3) and (4) are in the neutral position (3a). , (4
When in position a), a pilot passage (9) for selectively introducing atmospheric pressure is opened.

On the other hand, the pilot chamber (8C) opposing the spring chamber (8d)
is connected to the priority port (8b) via the pilot passage (10).
) The pressure of the first place is acting. And the pump boat (
8a) is first made to flow out from the priority port (8b) to the downstream side, and the pressure on the downstream side becomes [maximum load pressure P
+B of the spring (8f) in the spring chamber (8d)] Force (PS+
)], the amount of oil flowing out downstream of J, that is, the priority port (8b), is transferred to each of the elevation and extension switching valves (3),
(4) When the flow rate corresponding to the throttle limit is reached, the surplus oil flows out from the non-priority bow 1-(8C) to the downstream side thereof, and each switching valve (3) of the first circuit (A) .

(4) The differential pressure before and after the throttle is expressed as the biasing force (PS) of the spring (8f).
The preferential pressure compensation valve (8) constitutes a bypass pressure compensation valve provided in the first circuit (A).

On the other hand, the hoisting switching valve (5) of the second circuit (B) is the switching valve (3) of the first circuit (Δ).

Similar to (4), when in the neutral position (5a), the pump boat (5
It consists of a throttle switching valve that closes the hoisting switching valve (
5) are intermediate switching positions (5c'), (5) located above and below the neutral position fi (5a) in the figure and positioned when the operating lever (511) is within the range up to the predetermined stroke position.
d), and the final switching position (5c) and (5d), which are located above and below in the figure and are positioned when the operating lever (51)) is within the range from the predetermined stroke position to the maximum stroke position. 5e>, (5f), and therein is formed a load pressure detection boat (5g>) that detects the load pressure during intermediate and final switching positions 5C) to (5F). (5g)
is configured to communicate with the tank (6) via the pilot passage (11) when the neutral position 1a (5a>>).

Furthermore, inside the hoisting switching valve 5), there is a neutral position (
5a) and midway switching position (5b), (5c) sometimes communicates with the tank (6) through the pilot, and the final switching position (5
0).

(5f) A pilot boat (5h) is formed whose communication is sometimes blocked.

Further, a bypass type pressure compensating valve (14) is connected in the middle of the discharge path (2a) of the second fluid pump 2). The spring chamber (1=!) of the bypass type pressure compensation valve (14)
1. The load pressure detection boat (5g) of the hoisting switching valve (5) is communicated with a) via a pilot passage (15), and a pilot chamber (14a) opposing the spring chamber (14a) is connected to The discharge pressure of the second fluid pump (2) acts on the pilot passage (16), and when the hoisting switching valve (5) is in the neutral position (5a), the load pressure detection boat (59 ) to the tank (6) J: Resilient chamber (
14, 8) to the atmosphere and the second fluid pump (2)
While unloading the pressure oil from the spring chamber (14a) at a low pressure equal to the biasing force (PS2) of the spring (14C), the hoisting switching valve (5) is unloaded at each switching position (5G) to (5[
) At times, the pressure (load pressure) after the hoisting switching valve (5) is introduced into the spring chamber (14a) by the load pressure detected by the load pressure detection boat (5g), and the hoisting switching valve (5) is introduced into the pilot chamber (14b). The pressure in front of the valve (5) (discharge pressure of the second fluid pump (2)) is introduced, and the differential pressure before and after the hoisting switching valve (5) is controlled by the spring (
By maintaining the pressure equal to the urging force (PS2) of 14G>, a flow rate corresponding to the throttle opening of the hoisting switching valve (5) is supplied to the hoisting actuator, and at the same time, excess oil is transferred to the tank return passage ( 13) to the tank (6).

Then, the non-priority boat (
8C) is a discharge path (2) of the second fluid pump (2) via a bypass passage (18) with a check valve (17) interposed therebetween.
2a), and is connected to the middle of the first fluid pump (1
) is configured to combine the excess flow from the fluid pump (2) of M2 with the fluid from the fluid pump (2) of M2.

Then, the priority boat (8) of the priority expansion pressure compensation valve (8)
b) has an unload passage 19 communicating with the tank (6);
) is connected, and an unload valve (20) is interposed in the middle of the unload passage (19). The unload valve (20) allows and prevents communication of the unload passage (19) with the valve body (20a) seated on the m seat, and inside the valve body (20a) there is a primary side and spring chamber (
A communication path (20d) is formed which communicates with the spring chamber (20b) and has a throttle (2(M) interposed therebetween).
A spring (20e) with a predetermined spring pressure (PS3) that biases the valve body (208) in the seating direction (=I) is compressed in the shuttle valve (22) through the pilot passage (21). ) is connected to the shuttle valve (22).
is the pilot boat (5h) of the hoisting switching valve (5)
The pressure of the pilot passageway (23) communicating with - A high pressure is selected among the pressures in the passage (24).

In addition, (25) is a pilot relief valve that regulates the maximum pressure acting on the spring chamber (14a) of the bypass type pressure compensation valve (14), and (26) is the spring chamber (26) of the preferential expansion pressure compensation valve (8).
8d> is a pilot relief valve that regulates the maximum pressure acting on the valve.

Next, the operation of the above embodiment will be explained. First, selector valves (3), (4) for hoisting, elevating, and telescoping
When all <5> are in the neutral position (3a), (4a), (5a), the pump port (5p,
) closed state and load pressure detection port (5g) tank (
6), the entire fluid of the second fluid pump (2) is unloaded from the bypass pressure compensation valve (14) with a low pressure equal to the biasing force (PS2) of its spring (14c). ing. In addition, the three switching valves (3) mentioned above.

Each pilot port (3e) of (4) and (5).

(4e) and (511) are tank return passages (13), respectively.
), so the unload valve (20) connects the spring chamber <20b) to the tank (6).
When fluid flows to the spring chamber (20b') from the primary side through the communication path (20d), the pressure is applied to the spring chamber (20b') through the throttle (20d).
The pressure is reduced at 0c), and the pressure difference before and after the throttle (20C) is reduced by the pressure reducing action at the throttle (20c).
When the spring pressure (1]sa) becomes greater than the spring pressure (1]sa) of 0e), the valve body (20a) is unseated, the unloading valve (2o) is closed, and the unloading passage (19) is communicated.

Therefore, the entire fluid M of the first fluid pump (1) is unloaded from the priority port (81) of the priority expansion pressure compensation valve (8) to the tank (6) via the unload passage (one). are doing.

In this state, if only the hoisting switching valve (5) is operated independently and switched to the intermediate switching position 5c) or (5d), the pressure difference before and after the hoisting switching valve (5) is bypassed. Since the pressure compensation valve (14) maintains the force (PS2) of the spring (14c), the pressure oil of the second fluid pump (2) is throttled open by the hoisting switching valve (5). A flow rate corresponding to the amount of oil is supplied to the hoisting actuator, and excess oil is bypassed from the bypass type pressure compensation valve (14) to the tank (6). At this time, the pilot boat (511> of the hoisting switching valve (5) is still connected to the tank (6), so the unloading valve (20) remains closed and the unloading passage (19) is closed. As mentioned above, the entire amount of fluid from the first fluid pump (1) is transferred from the priority boat (8b) of the priority expansion pressure compensation valve (8) to the tank (6) via the unload passage (19). The unloaded hoisting actuator operates with relatively slow build-up.

In addition, the hoisting switching valve (5) is at the intermediate switching position (5C).
Or further from (5d) to the final switching position (5e) or (5
f), i.e., when it is necessary to speed up hoisting by merging two flow rates), the entire amount of pressure oil in the second fluid pump (2) passes through the hoisting switching valve (5). It is then supplied to the hoisting actuator. At this time, the pilot boat (5h) of the hoisting switching valve (5) is closed and communication with the tank (6) is cut off, so the unloading valve (2
A shuttle valve (2) is installed in the spring chamber of
The pressure in the pilot passage (23) acts due to the high pressure selection action in (2), and when the pressure in the pilot passage (23) becomes equal to the primary side pressure, the valve body (20a) is moved by the spring (20e).
The unloading passage (19) is closed by being biased by the unloading passage (19). As a result, the entire amount of fluid in the first fluid pump (1) is transferred from the non-priority port (8C) of the priority expansion pressure compensation valve (8) to the second fluid pump (2) via the bypass passage (18).
After merging with the fluid, the fluid is supplied from the hoisting switching valve (5) to the hoisting actuator. At that time, confluence 111A
When the flow rate is higher than the set flow rate of the hoisting switching valve (5), the excess oil is bypassed from the bypass type pressure compensation valve (14) to the tank (6).

In this state, for example, when the telescopic switching valve (4) is switched and enters a combined operation state with the hoisting switching valve (5), the first Out of the fluid from the fluid pump 1), the flow rate corresponding to the throttle polishing of the expansion/contraction switching valve (4) is transferred from the priority port (8b) of the priority expansion pressure compensation valve (8) to the expansion/contraction switching valve (4). At the same time, the surplus flow is supplied to the expansion/contraction actuator through the bypass passage (18) from the non-priority ports 1 to (8G) of the priority expansion pressure compensation valve (8) to the fluid of the second fluid pump (2). The flow merges and is supplied to the hoisting actuator from the hoisting switching valve (5). Therefore, 9J exchange valve for hoisting (
5) Even if J5 is selected during the composite switching of two or more switching valves including Therefore, the surplus flow can be used effectively compared to the conventional system in which two flow rates cannot be combined when switching the switching valve of the first circuit.

In the above embodiment, the pilot boat (5b) of the hoisting switching valve (5) is communicated with the tank (6) at the neutral position (5a) and the intermediate switching positions (5c>, (5d>), and the pilot boat (5b) is connected to the tank (6) at the final switching position. (5e) and (5f) are opened, but there are also intermediate switching positions (5c) and (5d).
Needless to say, even if the valve is closed in the opposite direction, the two flow rates can be combined. However, if the intermediate switching positions (5c) and (5d) are communicated with the tank (6) as in the above embodiment, the merging or non-merging of the two flow rates can be selected depending on the operating speed of the hoisting actuator. , more preferred.

Further, in the above embodiment, the hoisting switching valve (5) is configured with a throttle switching valve, but it goes without saying that it may be configured with a normal switching valve without a throttle. However, it is better to use a throttle switching valve because the actuator operates t! It is convenient for practical use because it can be used steplessly.

In the above embodiment, a special preferential expansion pressure compensation valve (8)
Excess oil is drained from the non-priority port (8C) to the bypass passage (1
8), but in addition, as shown in Figure 2, each switching valve for elevation and expansion/contraction (3'>, (
4') A bypass type pressure compensation valve (80) may be provided to compensate for the differential pressure before and after the pressure, and the bypass am of the bypass type pressure compensation valve (80) may be made to flow out into the bypass passage (18).

In addition, in the above embodiment, the case where the present invention is applied to a hydraulic circuit of a truck crane has been described, but it goes without saying that the present invention is not limited thereto, and can be similarly applied to various other types of two-flow rate merging circuits.

As explained above, according to the present invention, in a two-flow merging circuit in which fluids from two fluid pumps are combined in response to a switching operation of a switching valve belonging to one circuit, a switching valve belonging to the other circuit Even when the valves are switched, the surplus flow from the other fluid pump is merged with the fluid from one fluid pump as needed, so that the surplus flow can be used effectively.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, FIG. 1 is a hydraulic circuit diagram when applied to a hydraulic circuit of a truck crane, and FIG. 2 is a diagram showing a modification of a bypass type pressure compensation valve.
3 and 4 are fluid circuit diagrams showing conventional examples, respectively. (A)...first circuit, (B)...second circuit, (
1)...First fluid pump, (2)...Second fluid pump, (3)...Elevation switching valve, (4)...Extension switching valve, (3a), ( 4a >-”neutral position, (
3b), (4b)...Switching position, (3c), (4
c)...Switching position, <3e), (4+1...Pilot port, (3p), (4p)...Pump port, (5)...Hoisting switching valve, (5a)...・Neutral position, (5e). (5f)...Final switching position, (5h)...Pilot port, (6)...Tank, (8)...Priority expansion pressure compensation valve (bypass type pressure Compensation valve), (8b)...priority port (discharge bow (~), (8C)...non-priority port (bypass port), (17)...check valve, (18
)...Bypass passage, (20)...Unload valve,
(2ob>...Spring chamber, (22')...Shuttle valve, (80)...Bypass type pressure compensation valve.

Claims (1)

[Claims] (1) In a fluid circuit comprising a pair of circuits configured to supply fluid from a fluid pump to an actuator via a switching valve, the first circuit (A) has a pump port (3p) when in the neutral position (3a). ) is closed, and communicates with the tank (6) when in the neutral position (3a), and communicates with the tank (6) when in the switching position (3b).
) A throttle switching valve (3) having a pilot port (3e) that is closed when closed, and a bypass type pressure compensation valve (8) that maintains the differential pressure across the throttle switching valve (3) at a predetermined pressure (PS'+).
The second circuit (B) is equipped with:
A switching valve (5) having a pilot port (511) that communicates with the tank (6) in the neutral position (5a) and closes at least in the final switching position (5e) is provided, and the switching valve (5) has a pilot port (511) that communicates with the tank (6) when in the neutral position (5a) and closes at least in the final switching position (5e). The port (8C) communicates with the switching valve (5) of the second circuit (B) through a bypass passage (18) with a check valve (17) interposed therebetween, and is connected to the discharge of the bypass type pressure compensation valve (8). On the port (8b) side, the spring chamber (20b) connects the switching valve of the first circuit (A) (3) and the second circuit CB) via the shuttle valve (22).
Each pilot port (3e), (5h) of the switching valve (5)
) is connected to an unload valve (20) that communicates with the two flow rate merging circuit.