Hydraulic control circuit

Abstract

The present invention provides a fluid control circuit, a hydraulic control circuit, and a construction machine. The fluid control circuit of the present invention comprises: a first circuit that uses a first operating switching valve to deliver a first fluid discharged from a first pump to a first actuator; a second circuit that uses a second operating switching valve to deliver a second fluid discharged from a second pump to a second actuator; and a merging circuit that merges a second excess fluid in the second circuit with the first fluid, thereby merging the first excess fluid in the first circuit with the second fluid.

Description

Technical Field

[0001] The invention relates to a fluid control circuit, a hydraulic control circuit and a construction machine. Background Art

[0002] Among construction machines such as mobile cranes, there are known construction machines that include, for example, a hydraulic control circuit comprising a first circuit (hoisting circuit), a second circuit (boom circuit), and a merging valve. This hydraulic control circuit allows the merging valve to automatically merge excess oil in the second circuit with the hydraulic oil in the first hydraulic pump while supplying the hydraulic oil to the first actuator via a first operating switching valve in the first circuit, thereby increasing the driving speed of the first actuator (see, for example, Patent Document 1).

[0003] Another known hydraulic control circuit includes a merging control pilot switching valve arranged in series between a first hydraulic circuit (boom circuit) and a second hydraulic circuit (winch circuit), and an additional pilot pressure guide circuit (merging circuit). When no pilot pressure is supplied, the merging control pilot switching valve is held in a position that discharges the hydraulic oil flowing in the first hydraulic circuit directly to the return line. When pilot pressure is supplied, the merging control pilot switching valve switches to a position that supplies hydraulic oil to the hydraulic supply side of the second hydraulic circuit, merging this hydraulic oil with the hydraulic oil from the second hydraulic pump.

[0004] When pilot pressure is supplied to at least one of the main hoist drive pilot selector valve and the auxiliary hoist drive pilot selector valve in the second hydraulic circuit, the pilot pressure guide circuit delivers pilot pressure to the confluence control pilot selector valve. This automatically increases the hydraulic oil used to drive the main hoist and auxiliary hoist winches, thereby increasing the drive speed (see, for example, Patent Document 2).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-349304

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 6-346904 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] However, when the hydraulic control circuit of Patent Document 1 uses the hydraulic fluid of the second hydraulic pump to drive the first actuator in the second circuit, it is unable to merge the residual fluid in the first circuit with the hydraulic fluid of the second hydraulic pump to increase the driving speed of the second actuator. Furthermore, it is believed that when the hydraulic control circuit of Patent Document 1 uses the merging valve to merge the residual fluid in the second circuit with the hydraulic fluid of the first hydraulic pump, the residual fluid in the first circuit also merges with the residual fluid in the second circuit. Therefore, if the load pressure of the first actuator decreases, the bypass merging flow rate increases, which may deteriorate the pressure compensation characteristics of the first actuator.

[0011] Furthermore, the hydraulic control circuit of Patent Document 2 cannot merge the hydraulic oil of the second circuit (the hoisting circuit) with the hydraulic oil from the first hydraulic pump to increase the boom drive speed when driving the boom of the first circuit. Furthermore, the hydraulic control circuit of Patent Document 2 requires a pilot switching valve for merging control in order to merge the hydraulic oil of the first circuit with the hydraulic oil from the second hydraulic pump when driving the hoist, resulting in a complex structure.

[0012] The present invention provides a fluid control circuit, a hydraulic control circuit, and a construction machine capable of suppressing deterioration of pressure compensation characteristics of an actuator.

[0013] Solutions for solving problems

[0014] A fluid control circuit according to one embodiment of the present invention includes: a first circuit for conveying a first fluid ejected from a first pump to a first actuator using a first operating switching valve; a second circuit for conveying a second fluid ejected from a second pump to a second actuator using a second operating switching valve; and a merging circuit for merging a second residual fluid in the second circuit with the first fluid, thereby merging the first residual fluid in the first circuit with the second fluid.

[0015] With this configuration, the merging circuit can automatically merge the second excess fluid in the second circuit with the first fluid of the first pump. This allows the first fluid, after merging with the second excess fluid, to be delivered to the first actuator, increasing the driving speed of the first actuator.

[0016] Furthermore, by merging only the second excess fluid in the second circuit with the first fluid of the first pump, it is possible to suppress an excessive amount of excess fluid from merging with the first fluid of the first pump. Consequently, during throttle-off control under low load conditions of the first actuator, an increase in the bypass merging flow rate can be suppressed, thereby maintaining favorable pressure compensation characteristics.

[0017] Another embodiment of a hydraulic control circuit of the present invention includes: a first circuit that utilizes a first operating switching valve to deliver a first working oil ejected from a first hydraulic pump to a first actuator; a second circuit that utilizes a second operating switching valve to deliver a second working oil ejected from a second hydraulic pump to a second actuator; and a merging circuit that merges the second residual oil in the second circuit with the first working oil, and merges the first residual oil in the first circuit with the second working oil.

[0018] With this configuration, another aspect of the hydraulic control circuit of the present invention can automatically merge the second residual oil in the second circuit with the first hydraulic oil of the first hydraulic pump using the merging circuit. Thus, the hydraulic control circuit of another aspect of the present invention can deliver the first hydraulic oil, resulting from the merging of the second residual oil, to the first actuator, thereby increasing the driving speed of the first actuator.

[0019] Furthermore, another aspect of the hydraulic control circuit of the present invention prevents excessive excess oil from merging with the first hydraulic oil of the first hydraulic pump by merging only the second residual oil in the second circuit. This prevents excessive merging of the bypass merging flow rate during throttle-by control under low load conditions on the first actuator, thereby maintaining favorable pressure compensation characteristics.

[0020] Another aspect of the hydraulic control circuit of the present invention utilizes a merging circuit to automatically merge the first residual oil in the first circuit with the second hydraulic oil from the second hydraulic pump. This allows the second hydraulic oil, resulting from the merging of the first residual oil, to be delivered to the second actuator, thereby increasing the drive speed of the second actuator.

[0021] Furthermore, by merging only the first residual oil in the first circuit with the second hydraulic oil of the second hydraulic pump, another aspect of the hydraulic control circuit of the present invention can suppress excessive residual oil from merging with the second hydraulic oil of the second hydraulic pump. Consequently, during throttle-off control under low load conditions of the second actuator, an increase in the bypass merging flow rate can be suppressed, thereby maintaining favorable pressure compensation characteristics.

[0022] As described above, according to the hydraulic control circuit of another aspect of the present invention, the first circuit and the second circuit can be automatically merged in both directions, and deterioration of the pressure compensation characteristic of the actuator can be suppressed.

[0023] In the above structure, the merging circuit may also have: a first connecting passage, which includes a first neutral fully open passage for merging the second residual oil with the first working oil; and a second connecting passage, which includes a second neutral fully open passage for merging the first residual oil with the second working oil.

[0024] In the above structure, the hydraulic control circuit may also be provided with: a first flow regulating valve, which is connected between the first hydraulic pump and the first operating switching valve, and controls the flow of either the first working oil or the first residual oil delivered to the first operating switching valve; and a second flow regulating valve, which is connected between the second hydraulic pump and the second operating switching valve, and controls the flow of either the second working oil or the second residual oil delivered to the second operating switching valve.

[0025] 18. The hydraulic control circuit of claim 17, wherein the first circuit includes a first hydraulic pump, a first operation switching valve connected to the first hydraulic pump, and a first flow regulating valve connected between the first operation switching valve and the first hydraulic pump to control the flow rate of either a first working oil or a first residual oil supplied to the first operation switching valve. The second circuit includes a second hydraulic pump, a second operation switching valve connected to the second hydraulic pump, and a second flow regulating valve connected between the second operation switching valve and the second hydraulic pump to control the flow rate of either a second working oil or a second residual oil supplied to the second operation switching valve. The merging circuit includes a first connecting passage including a neutral fully open passage for merging the second residual oil with the first working oil, and a second connecting passage including a neutral fully open passage for merging the first residual oil with the second working oil.

[0026] With this configuration, the merging circuit can automatically merge the second residual oil in the second circuit with the first hydraulic oil of the first hydraulic pump. Thus, the first hydraulic oil after merging with the second residual oil can be delivered to the first actuator, thereby increasing the driving speed of the first actuator.

[0027] Furthermore, by merging only the second excess oil in the second circuit with the first hydraulic oil of the first hydraulic pump, it is possible to prevent excessive excess oil from merging with the first hydraulic oil of the first hydraulic pump. Consequently, during throttle-off control under low load conditions of the first actuator, it is possible to prevent the bypass merging flow rate from increasing, thereby maintaining favorable pressure compensation characteristics.

[0028] Furthermore, the merging circuit can automatically merge the first excess oil in the first circuit with the second hydraulic oil of the second hydraulic pump, thereby delivering the second hydraulic oil after merging with the first excess oil to the second actuator, thereby increasing the driving speed of the second actuator.

[0029] Furthermore, by merging only the first residual oil in the first circuit with the second hydraulic oil of the second hydraulic pump, it is possible to prevent excessive residual oil from merging with the second hydraulic oil of the second hydraulic pump. Consequently, during throttle-off control under low load conditions of the second actuator, it is possible to prevent the bypass merging flow rate from increasing, thereby maintaining favorable pressure compensation characteristics.

[0030] In this manner, according to the hydraulic control circuit, the first circuit and the second circuit can be automatically merged in both directions, and deterioration of the pressure compensation characteristic of the actuator can be suppressed.

[0031] Furthermore, for example, the first residual oil of the first hydraulic pump can be automatically merged with the second working oil of the second hydraulic pump, and the second residual oil of the second hydraulic pump can be automatically merged with the first working oil of the first hydraulic pump, without using the confluence control pilot switching valve required in Patent Document 2. Thus, the residual oil of one of the first and second hydraulic pumps can be merged with the working oil of the other using a simple structure.

[0032] Another form of the hydraulic control circuit of the present invention comprises: a hydraulic circuit and a merging circuit, the hydraulic circuit having: a hydraulic pump; an operating switching valve connected to the hydraulic pump to perform drive control of the hydraulic actuator; and a flow regulating valve arranged between the hydraulic pump and the operating switching valve to control the supply amount of working oil to the operating switching valve, the merging circuit connecting the part of the hydraulic circuit located downstream of the flow regulating valve with other hydraulic circuits.

[0033] This configuration allows excess oil in the hydraulic circuit to flow to other hydraulic circuits via the merging circuit. This allows good pressure compensation characteristics to be maintained by throttle control during low load conditions on the hydraulic actuator.

[0034] In the above configuration, the merging circuit may include a connecting passage, and the connecting passage may include a neutral fully open passage.

[0035] A construction machine according to another aspect of the present invention includes a vehicle body on which the above-mentioned hydraulic control circuit is mounted.

[0036] With this configuration, it is possible to provide a construction machine including a hydraulic control circuit that can automatically merge the first circuit and the second circuit in both directions with a simple structure and suppress deterioration of the pressure compensation characteristics of the actuator.

[0037] Effects of the Invention

[0038] The above-described fluid control circuit, hydraulic control circuit, and construction machine can suppress deterioration of the pressure compensation characteristic of the actuator. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic configuration diagram of a construction machine in the first embodiment of the present invention.

[0040] Figure 2 This is a circuit diagram showing a hydraulic control circuit in the first embodiment.

[0041] Figure 3 It is magnified Figure 2 Circuit diagram of the combining valve.

[0042] Figure 4 This is a graph showing the relationship between the excess oil flowing through the first connecting passage and the load pressure of the auxiliary hoisting motor in a comparative example.

[0043] Figure 5 This is a circuit diagram showing a hydraulic control circuit in a second embodiment of the present invention.

[0044] Description of Reference Numerals

[0045] 1. 80. Hydraulic control circuit (fluid control circuit); 2. First circuit; 3. Second circuit; 4. Merging circuit; 10. 11. First operating switching valve; 12. 13. First flow regulating valve; 20. 21. 22. Second operating switching valve; 23. 24. 25. Second flow regulating valve; 35. Merging valve; 53. First connecting passage; 54. Second connecting passage; 82. Second merge valve; 100. Construction machinery; 101. Rotating body (vehicle body); 102. Traveling body (vehicle body); 111. First actuator; 115. Second actuator; P1. First hydraulic pump (first pump); P2. Second hydraulic pump (second pump). DETAILED DESCRIPTION

[0046] Next, embodiments of the present invention will be described with reference to the drawings.

[0047] [First embodiment]

[0048] <Construction machinery>

[0049] Figure 1 This is a schematic diagram of the construction machine 100 . Figure 2 1 is a circuit diagram showing the hydraulic control circuit 1 .

[0050] like Figure 1 、 Figure 2As shown, construction machine 100 is a self-propelled crane, such as a rough-terrain crane. Construction machine 100 includes, for example, a revolving body (equivalent to a vehicle body in the claims) 101 and a traveling body (equivalent to a vehicle body in the claims) 102. Revolving body 101 is rotatably mounted on traveling body 102. A hydraulic control circuit (also including a fluid control circuit in the claims) 1 is mounted on revolving body 101.

[0051] The rotating body 101 includes: a cab 103 in which an operator can sit; a boom 105, which is connected to a base 104 in a freely swinging manner; a main lifting hook 106, which hangs down from the top of the boom 105; a cantilever 107, which is connected to the top of the boom 105 in a freely swinging manner; and an auxiliary lifting hook 108, which hangs down from the top of the cantilever 107.

[0052] The revolving structure 101 is equipped with a hydraulic control circuit 1. The main hoisting and winding motor 113 and the auxiliary hoisting and winding motor 112 are driven by first hydraulic oil (working fluid) delivered from a first hydraulic pump (an example of a first pump or a first hydraulic pump in the claims) P1 of the hydraulic control circuit 1. Hereinafter, the main hoisting and winding motor 113 and the auxiliary hoisting and winding motor 112 may be referred to as the first actuator 111.

[0053] Furthermore, the boom extension / retraction cylinder 116, the boom raising / lowering cylinder 117, and the arm swing cylinder 118 are driven by the second hydraulic oil discharged from the second hydraulic pump (an example of the second pump in the claims) P2 of the hydraulic control circuit 1. Hereinafter, the boom extension / retraction cylinder 116, the boom raising / lowering cylinder 117, and the arm swing cylinder 118 may be referred to as the second actuator 115.

[0054] Hydraulic control circuit

[0055] The hydraulic control circuit 1 includes a first circuit 2 to which first hydraulic oil is mainly delivered from a first hydraulic pump P1 , a second circuit 3 to which second hydraulic oil is mainly delivered from a second hydraulic pump P2 , and a merging circuit 4 connecting the first circuit 2 and the second circuit 3 .

[0056] The first circuit 2 is a first hydraulic pump system comprising two first operation switching valves 10 and 11, which primarily deliver first hydraulic fluid from a first hydraulic pump P1, and first flow control valves (pressure compensation valves) 12 and 13 corresponding to the first operation switching valves 10 and 11. The first flow control valve 12 is connected midway between the first hydraulic pump P1 and the first operation switching valve 10. The first flow control valve 13 is connected midway between the first hydraulic pump P1 and the first operation switching valve 11.

[0057] The first operating switching valves 10 and 11 are hydraulically piloted valves with pilots provided at both ends. The first operating switching valves 10 and 11 are switched using the first hydraulic oil supplied to and discharged from the pilots. The first operating switching valves 10 and 11 have ports for the first actuators 111, which supply and discharge the first hydraulic oil to and from the corresponding first actuators 111.

[0058] Specifically, the first operation switching valve 10 has ports A1 and B1 for the auxiliary hoisting motor 112 for supplying and discharging the first hydraulic oil to and from the auxiliary hoisting motor 112. The first operation switching valve 11 has ports A2 and B2 for the main hoisting motor 113 for supplying and discharging the first hydraulic oil to and from the main hoisting motor 113.

[0059] The first operating switching valve 10 is connected to a first load pressure detection passage 15 for detecting the load pressure of the auxiliary hoisting hoisting motor 112 during operation. The first operating switching valve 11 is connected to a first load pressure detection passage 16 for detecting the load pressure of the main hoisting hoisting motor 113 during operation. The first flow regulating valve 12 is controlled based on the load pressure detected by the first load pressure detection passage 15. The first flow regulating valve 13 is controlled based on the load pressure detected by the first load pressure detection passage 16.

[0060] That is, the first circuit 2 is a hoisting circuit that operates the first operation switching valves 10 and 11 by pilot pressure to drive the auxiliary hoisting motor 112 and the main hoisting motor 113 by the first hydraulic oil discharged from the first hydraulic pump P1.

[0061] The second circuit 3 is a second hydraulic pump system comprising three second operation switching valves 20, 21, and 22, which primarily deliver the second hydraulic oil from the second hydraulic pump P2, and second flow control valves (pressure compensation valves) 23, 24, and 25 corresponding to the second operation switching valves 20, 21, and 22. The second flow control valves 23, 24, and 25 are connected midway between the second hydraulic pump P2 and the second operation switching valves 20, 21, and 22.

[0062] The second operating switching valves 20, 21, and 22 are hydraulic pilot-type valves similar to the first operating switching valves 10 and 11, and are provided with pilot parts on both ends. The second operating switching valves 20, 21, and 22 perform switching operations using the second working oil supplied and discharged relative to the pilot parts. The second operating switching valves 20, 21, and 22 have ports for the second actuator 115 for supplying and discharging the second working oil relative to the corresponding second actuator 115. Specifically, the second operating switching valve 20 has ports A3 and B3 for the boom extension cylinder 116. The second operating switching valve 21 has ports A4 and B4 for the boom lifting cylinder 117. In addition, the second operating switching valve 22 has ports A5 and B5 for the cantilever swing cylinder 118.

[0063] Furthermore, the second operation switching valve 20 is connected to a second load pressure detection passage 26 for detecting the load pressure during operation of the boom extension / extension cylinder 116. The second operation switching valve 21 is connected to a second load pressure detection passage 27 for detecting the load pressure during operation of the boom raising / lowering cylinder 117. The second operation switching valve 22 is connected to a second load pressure detection passage 28 for detecting the load pressure during operation of the boom swing cylinder 118.

[0064] The second flow regulating valve 23 is controlled based on the load pressure detected by the second load pressure detection passage 26. The second flow regulating valve 24 is controlled based on the load pressure detected by the second load pressure detection passage 27. The second flow regulating valve 25 is controlled based on the load pressure detected by the second load pressure detection passage 28.

[0065] Furthermore, based on the load pressure detected by the second load pressure detection passages 26, 27, 28, the high-pressure selector valves 31 and 32 select the maximum load pressure in the second operation switching valves 20, 21, and 22. The maximum load pressure selected by the high-pressure selector valves 31 and 32 is used to control the merging valve 35.

[0066] That is, the second circuit 3 is a boom circuit that operates the second operation switching valves 20 , 21 , 22 by pilot pressure, thereby driving the boom extension cylinder 116 , the boom raising / lowering cylinder 117 , and the arm swing cylinder 118 by the second hydraulic oil discharged from the second hydraulic pump P2 .

[0067] The merging circuit 4 is a merging system including a merging valve 35 , first check valves 37 and 38 , and second check valves 41 , 42 , and 43 .

[0068] The merging valve 35 is a flow control valve that combines the second residual oil (excess fluid) of the second hydraulic oil of the second hydraulic pump P2 with the first hydraulic oil of the first hydraulic pump P1, depending on the situation. Specifically, the merging valve 35 is a spool-type valve, with a spool 36 supported at both ends for movement by an axial force. The merging valve 35 is designed so that the opening of the spool 36 gradually changes between a blocked position and an open position, thus providing both opening and closing functions and variable throttling.

[0069] The flow of residual oil will be discussed in detail later. Residual oil refers to the hydraulic oil discharged from the first hydraulic pump P1 or the second hydraulic pump P2 that is not delivered to the first actuator 111 or the second actuator 115 or is not consumed by the first actuator 111 or the second actuator 115 and therefore flows back. In other words, the first residual oil refers to the remaining hydraulic oil resulting from the difference between the flow rate of the first hydraulic oil discharged from the first hydraulic pump P1 and the flow rate of the hydraulic oil actually delivered to the first actuator 111. Furthermore, the second residual oil refers to the remaining hydraulic oil resulting from the difference between the flow rate of the second hydraulic oil discharged from the second hydraulic pump P2 and the flow rate of the hydraulic oil actually delivered to the second actuator 115.

[0070] Figure 3 It is magnified Figure 2 In the following description, the left and right directions are the same as Figure 3 The left and right directions are consistent.

[0071] like Figure 3 As shown, the hydraulic pressure acting on the left end of the spool 36 of the converging valve 35 acts as follows: the hydraulic pressure of the second hydraulic pump P2 is transmitted to the pressure chamber 46 via the passage 45, causing the spool 36 to move to the right. In addition, the spring 47 contacts the right end of the spool 36, and the high pressure selector valve 31 is connected to the spring chamber 48 via the passage 49 (see Figure 2 The rightward force acting on the right end of the spool 36 is determined by the spring force generated by the spring 41 and the output pressure from the high-pressure selector valve 31.

[0072] The merging valve 35 changes the opening between a passage 52 connected to the supply passage 51 of the second hydraulic pump P2 and a first connecting passage 53 connected to the first operational switching valves 10 and 11 by movement of the spool 36. The first connecting passage 53 is a neutral, fully open passage (series passage) that connects the first operational switching valves 10 and 11 to the tank T. The first connecting passage 53 is provided upstream of the second flow control valves 23, 24, and 25.

[0073] like Figure 2 As shown, first check valves 37 and 38 are provided upstream of first operational switching valves 10 and 11 and are respectively connected to first connecting passages 53. Second check valves 41, 42, and 43 are provided upstream of second operational switching valves 20, 21, and 22 and are respectively connected to second connecting passages 54. Second connecting passage 54 is a neutral fully open passage (series passage) that connects second operational switching valves 20, 21, and 22 to tank T. Second connecting passage 54 is provided downstream of first flow control valves 12 and 13.

[0074] <Hydraulic control circuit control>

[0075] Next, control of the hydraulic control circuit 1 will be described.

[0076] First, based on Figure 2 An example in which the second excess oil in the second circuit 3 is joined to the first circuit 2 will be described.

[0077] like Figure 2 As shown, when the first operation switching valves 10 and 11 and the second operation switching valves 20, 21, and 22 are not operated (in a neutral position), for example, the first operation switching valve 10 is operated. In this case, the first flow regulating valve 12 supplies the first hydraulic oil of the first hydraulic pump P1 to the first operation switching valve 10 according to the switching amount of the first operation switching valve 10. The first residual oil in the first hydraulic oil of the first hydraulic pump P1 flows downstream.

[0078] Furthermore, for example, when the second operation switching valve 21 is operated among the second operation switching valves 20, 21, and 22, the second hydraulic oil of the second hydraulic pump P2 is delivered to the second operation switching valve 21 via the second flow regulating valve 24 according to the switching amount of the second operation switching valve 21. The first residual oil of the second hydraulic pump P2 is delivered to the pressure chamber 46 (see FIG. 1 ) via the passage 52 and the passage 45. Figure 3 ) is transmitted, causing the spool 36 to move rightward. The second excess oil of the second hydraulic pump P2 is sent to the first connecting passage 53 via the merging valve 35.

[0079] The first throttle opening 56 of the first operation switching valve 10 decreases in accordance with the switching amount of the first operation switching valve 10. Specifically, during throttle control, which causes the second residual oil in the first connecting passage 53 to flow back to the tank T, the second residual oil is pressurized, causing the first check valve 37 to open. Thus, with a simple structure, the second residual oil in the first connecting passage 53 automatically merges with the first hydraulic oil of the first hydraulic pump P1 upstream of the first operation switching valve 10 via the first check valve 37.

[0080] Here, the throttle control refers to, for example, controlling the speed of the first actuator 111 by adjusting the overflow amount and performing flow rate control by bypassing a main circuit provided in the supply-side pipe to the first actuator 111 .

[0081] The combined second residual oil and the first working oil of the first hydraulic pump P1 are delivered as working oil to the auxiliary hoisting motor 112 via the first operating switching valve 10 and the passage 57. As a result, compared with the drive performed by the first hydraulic pump P1 alone, the flow rate of the working oil that drives the auxiliary hoisting motor 112 is increased, and the driving speed of the auxiliary hoisting motor 112 can be increased.

[0082] In this state, the first residual oil of the first hydraulic pump P1 that is not delivered to the auxiliary hoisting motor 112 is delivered to the passage 61 via the first flow regulating valves 12 and 13. Therefore, it is possible to prevent the first residual oil of the first hydraulic pump P1 from being guided to the first connecting passage 53. In other words, it is possible to prevent both the second residual oil of the second hydraulic pump P2 and the first residual oil of the first hydraulic pump P1 from being guided to the first connecting passage 53.

[0083] Here, as a comparative example, based on Figure 4 An example will be described in which the pressure compensation characteristic deteriorates when both the second excess oil of the second hydraulic pump P2 and the first excess oil of the first hydraulic pump P1 are fed to the first connecting passage 53 .

[0084] Figure 4 Graph G shows the relationship between the supply flow rates of the first and second excess oils passing through the first connecting passage 53 and the load pressure of the auxiliary hoisting motor 112 in a comparative example. Graph G shows the bypass confluent flow rate.

[0085] like Figure 4 As shown in FIG. 1 , when the residual oil (first residual oil and second residual oil) of both the second hydraulic pump P2 and the first hydraulic pump P1 is delivered to the first connecting passage 53, if the load pressure of the auxiliary hoisting motor 112 decreases, the bypass confluent flow rate increases as shown in FIG. Therefore, it is considered that the pressure compensation characteristic of the auxiliary hoisting motor 112 deteriorates.

[0086] In contrast, in the first embodiment, by not directing the first residual oil of the first hydraulic pump P1 to the first connecting passage 53, neither the second residual oil of the second hydraulic pump P2 nor the first residual oil of the first hydraulic pump P1 is directed to the first connecting passage 53. As a result, the residual oil volume flowing through the first connecting passage 53 can be appropriately maintained. This allows the bypass confluence flow rate to be appropriately suppressed when the load pressure of the auxiliary hoisting motor 112 decreases. Consequently, deterioration of the pressure compensation characteristics can be suppressed.

[0087] Furthermore, the second residual oil of the second hydraulic pump P2 and the first residual oil of the first hydraulic pump P1 are not introduced into the first connecting passage 53, thereby appropriately maintaining the amount of residual oil passing through the first connecting passage 53. This allows the flow rate of the hydraulic oil passing through the first connecting passage 53 to be appropriately suppressed, minimizing the pressure loss of the hydraulic oil passing through the first connecting passage 53, and maintaining good consumption performance.

[0088] Then, based on Figure 2 An example in which the first excess oil in the first circuit 2 is merged with the second circuit 3 will be described.

[0089] like Figure 2As shown, while the first operation switching valves 10 and 11 and the second operation switching valves 20, 21, and 22 are not operated (in a neutral position), for example, the second operation switching valve 21 is operated. In this case, the second flow regulating valve 24 supplies the second hydraulic oil of the second hydraulic pump P2 to the second operation switching valve 21 according to the switching amount of the second operation switching valve 21. The second residual oil in the second hydraulic oil of the second hydraulic pump P2 flows downstream.

[0090] In addition, for example, when the first operating switching valve 10 of the first operating switching valves 10 and 11 is operated, the first working oil of the first hydraulic pump P1 is delivered from the first hydraulic pump P1 to the first operating switching valve 10 via the first flow regulating valve 12 according to the switching amount of the first operating switching valve 10.

[0091] The first excess oil of the first hydraulic pump P1 is sent to the passage 61 via the first flow regulating valves 12 and 13. The first excess oil sent to the passage 61 is sent to the second connecting passage 54 via the passage 61.

[0092] The second throttle opening 58 of the second operation switching valve 21 decreases in accordance with the switching amount of the second operation switching valve 21. Specifically, during throttle control to return the first residual oil in the second connecting passage 54 to the tank T, the first residual oil pressure increases, causing the second check valve 42 to open. Thus, with a simple structure, the first residual oil in the second connecting passage 54 automatically merges with the second hydraulic oil of the second hydraulic pump P2 upstream of the second operation switching valve 21 via the second check valve 42.

[0093] The combined first residual oil and the second working oil of the second hydraulic pump P2 are delivered as working oil for operating the boom lift cylinder 117 via the second operation switching valve 21 and the passage 59. As a result, the flow rate of the working oil for driving the boom lift cylinder 117 is increased compared to the drive by the second hydraulic pump P2 alone, and the driving speed of the boom lift cylinder 117 can be increased.

[0094] In this state, the second residual oil of the second hydraulic pump P2 that is not delivered to the boom lift cylinder 117 is delivered to the first connecting passage 53 via the merging valve 35. As a result, the second residual oil of the second hydraulic pump P2 can be prevented from being introduced to the second connecting passage 54. In other words, both the first residual oil of the first hydraulic pump P1 and the second residual oil of the second hydraulic pump P2 can be prevented from being introduced to the second connecting passage 54.

[0095] Therefore, the amount of residual oil flowing through the second connecting passage 54 can be appropriately maintained. Consequently, when the load pressure of the boom raising / lowering cylinder 117 decreases, the bypass confluence flow rate can be appropriately suppressed. Consequently, deterioration of the pressure compensation characteristics can be suppressed.

[0096] Furthermore, the first residual oil of the first hydraulic pump P1 and the second residual oil of the second hydraulic pump P2 are not introduced into the second connecting passage 54, thereby appropriately maintaining the amount of residual oil passing through the second connecting passage 54. This allows the flow rate of the hydraulic oil passing through the second connecting passage 54 to be appropriately suppressed, minimizing the pressure loss of the hydraulic oil passing through the second connecting passage 54, and maintaining good consumption performance.

[0097] exist Figure 2 In the description, an example is described in which the first operation switching valve 10 of the first operation switching valves 10 and 11 of the first circuit 2 is operated, and the second operation switching valve 21 of the second operation switching valves 20, 21, and 22 of the second circuit 3 is operated. However, the operation of the operation switching valves is not limited to this. As another example, the same effect can be obtained even when any one of the first operation switching valves 10 and 11 or any one of the second operation switching valves 20, 21, and 22 is operated.

[0098] As described above, the hydraulic control circuit 1 can automatically merge the first circuit 2 and the second circuit 3 in both directions with a simple structure, thereby suppressing deterioration of the pressure compensation characteristics of the first actuator 111 and the second actuator 115 .

[0099] Furthermore, in the hydraulic control circuit 1, a merging valve 35 is provided in the merging circuit 4, and the merging valve 35 is used to transfer the excess pressure of the second circuit 3 to the first circuit 2. Thus, when either the first operation switching valves 10 and 11 of the first circuit 2 is operated or either the second operation switching valves 20, 21, or 22 of the second circuit 3 is operated, the condition for transferring the excess pressure of the second circuit 3 to the first circuit 2 can be prioritized over the condition for transferring the excess pressure of the first circuit 2 to the second circuit 3.

[0100] Furthermore, in the hydraulic control circuit 1, the first connecting passage 53 is configured as a neutral fully open passage (serial passage) connecting the first operation switching valves 10 and 11 to the tank T. The second connecting passage 54 is configured as a neutral fully open passage (serial passage) connecting the second operation switching valves 20, 21, and 22 to the tank T. Therefore, the excess oil in the first operating oil and the second operating oil from the hydraulic pumps P1 and P2 can be easily returned to the tank T.

[0101] Furthermore, the hydraulic control circuit 1 includes first flow control valves 12 and 13 connected midway between the first hydraulic pump P1 and the first operating switching valves 10 and 11. Therefore, the first flow control valves 12 and 13 can be used to control the first residual oil in the first hydraulic pump P1 and deliver it to the second connecting passage 54. As a result, the first residual oil in the first hydraulic pump P1 and the second hydraulic oil in the second hydraulic pump P2 can be automatically merged. In this state, the second residual oil in the second hydraulic pump P2 can be delivered to the first connecting passage 53. This prevents the bypass merging flow from increasing during throttle-off control of the first actuator 111 under low load, thereby maintaining favorable pressure compensation characteristics.

[0102] Furthermore, the hydraulic control circuit 1 includes second flow control valves 23, 24, and 25 connected midway between the second hydraulic pump P2 and the second operating switching valves 20, 21, and 22. Therefore, the second flow control valves 23, 24, and 25 can be used to control the second residual oil in the second hydraulic pump P2 and deliver it to the first connecting passage 53. As a result, the second residual oil in the second hydraulic pump P2 can be automatically merged with the first hydraulic oil in the first hydraulic pump P1. In this state, the first residual oil in the first hydraulic pump P1 can be delivered to the second connecting passage 54. This prevents the bypass merging flow from increasing during throttle-off control of the second actuator 115 under low load, thereby maintaining favorable pressure compensation characteristics.

[0103] Furthermore, for example, without using a conventionally required pilot switching valve for merging control, the first residual oil of the first hydraulic pump P1 can be automatically merged with the second hydraulic oil of the second hydraulic pump P2, and the second residual oil of the second hydraulic pump P2 can be automatically merged with the first hydraulic oil of the first hydraulic pump P1. Thus, the residual oil of one of the first hydraulic pump P1 and the second hydraulic pump P2 can be merged with the hydraulic oil of the other using a simple structure.

[0104] [Second embodiment]

[0105] Hydraulic control circuit

[0106] Then, based on Figure 5 A hydraulic control circuit 80 according to a second embodiment will be described. Components identical to those of the hydraulic control circuit 1 according to the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0107] Figure 5 1 is a circuit diagram showing a hydraulic control circuit 80 according to the second embodiment.

[0108] like Figure 5As shown, the hydraulic control circuit 80 is provided with a second merging valve 82 in the merging circuit 4. This point is different from the first embodiment described above. The rest of the structure of the hydraulic control circuit 80 of the second embodiment is the same as that of the hydraulic control circuit 1 of the first embodiment. The second merging valve 82 is constructed similarly to the merging valve 35 of the first embodiment.

[0109] <Hydraulic control circuit control>

[0110] Next, control of the hydraulic control circuit 80 in the second embodiment will be described.

[0111] First, based on Figure 5 An example of merging the second excess oil of the second circuit 3 with the first circuit 2 will be described. Figure 5 The left and right directions are consistent.

[0112] like Figure 5 As shown, when the first operation switching valves 10 and 11 and the second operation switching valves 20, 21, and 22 are not operated (in a neutral position), for example, the first operation switching valve 10 is operated. In this case, the first flow regulating valve 12 supplies the first hydraulic oil of the first hydraulic pump P1 to the first operation switching valve 10 according to the switching amount of the first operation switching valve 10. The first residual oil in the first hydraulic oil of the first hydraulic pump P1 flows downstream.

[0113] For example, when the second operation switching valve 21 among the second operation switching valves 20 , 21 , and 22 is operated, the second hydraulic oil of the second hydraulic pump P2 is delivered to the second operation switching valve 21 via the second flow regulating valve 24 according to the switching amount of the second operation switching valve 21 .

[0114] The second excess oil of the second hydraulic pump P2 is discharged to the pressure chamber 46 (see Figure 3 ) is transmitted, causing the spool 36 to move rightward. The second excess oil of the second hydraulic pump P2 is sent to the first connecting passage 53 via the merging valve 35.

[0115] The first throttle opening 56 of the first operation switching valve 10 decreases in accordance with the switching amount of the first operation switching valve 10. Specifically, during throttle control, which causes the second residual oil in the first connecting passage 53 to flow back to the tank T, the second residual oil is pressurized, causing the first check valve 37 to open. Thus, with a simple structure, the second residual oil in the first connecting passage 53 automatically merges with the first hydraulic oil of the first hydraulic pump P1 upstream of the first operation switching valve 10 via the first check valve 37.

[0116] The combined second residual oil and the first working oil of the first hydraulic pump P1 are delivered as working oil to the auxiliary hoisting motor 112 via the first operating switching valve 10 and the passage 57. As a result, compared with the drive performed by the first hydraulic pump P1 alone, the flow rate of the working oil that drives the auxiliary hoisting motor 112 is increased, and the driving speed of the auxiliary hoisting motor 112 can be increased.

[0117] In this state, the first residual oil of the first hydraulic pump P1 that is not delivered to the auxiliary hoisting hoisting motor 112 is delivered to the passage 84 via the passage 83 and the second merging valve 82. As a result, the first residual oil of the first hydraulic pump P1 can be prevented from being introduced into the first connecting passage 53. In other words, both the second residual oil of the second hydraulic pump P2 and the first residual oil of the first hydraulic pump P1 can be prevented from being introduced into the first connecting passage 53.

[0118] Therefore, the second residual oil from the second hydraulic pump P2 and the first residual oil from the first hydraulic pump P1 are prevented from being introduced into the first connecting passage 53. As a result, the residual oil volume flowing through the first connecting passage 53 can be appropriately maintained. This effectively suppresses the bypass confluence flow rate when the load pressure of the auxiliary hoisting motor 112 decreases. Consequently, deterioration of the pressure compensation characteristics can be suppressed.

[0119] Furthermore, the second residual oil of the second hydraulic pump P2 and the first residual oil of the first hydraulic pump P1 are not introduced into the first connecting passage 53, thereby appropriately maintaining the amount of residual oil passing through the first connecting passage 53. This allows the flow of hydraulic oil through the first connecting passage 53 to be appropriately controlled, minimizing pressure loss during the passage of the hydraulic oil through the first connecting passage 53 and maintaining good consumption performance.

[0120] Then, based on Figure 5 An example of merging the first residual oil in the first circuit 2 with the second circuit 3 will be described. Figure 5 As shown, while the first operation switching valves 10 and 11 and the second operation switching valves 20, 21, and 22 are not operated (in a neutral position), for example, the second operation switching valve 21 is operated. In this case, the second flow regulating valve 24 supplies the second hydraulic oil of the second hydraulic pump P2 to the second operation switching valve 21 according to the switching amount of the second operation switching valve 21. The second residual oil in the second hydraulic oil of the second hydraulic pump P2 flows downstream.

[0121] For example, when the first operation switching valve 10 is operated, the first hydraulic oil of the first hydraulic pump P1 is supplied to the first operation switching valve 10 via the first flow regulating valve 12 according to the switching amount of the first operation switching valve 10 .

[0122] The first excess oil of the first hydraulic pump P1 is sent to the passage 84 via the passage 83 and the second merging valve 82. The first excess oil sent to the passage 84 is sent to the second connecting passage 54 via the passage 84.

[0123] The second throttle opening 58 of the second operation switching valve 21 decreases in accordance with the switching amount of the second operation switching valve 21. Specifically, during throttle control to return the first residual oil in the second connecting passage 54 to the tank T, the first residual oil pressure increases, causing the second check valve 42 to open. Thus, with a simple structure, the first residual oil in the second connecting passage 54 automatically merges with the second hydraulic oil of the second hydraulic pump P2 upstream of the second operation switching valve 21 via the second check valve 42.

[0124] The combined first residual oil and the second working oil of the second hydraulic pump P2 are delivered as working oil to the boom lift cylinder 117 via the second operation switching valve 21 and the passage 59. As a result, the flow rate of working oil for driving the boom lift cylinder 117 is increased compared to the drive by the second hydraulic pump P2 alone, and the driving speed of the boom lift cylinder 117 can be increased.

[0125] In this state, the second excess oil of the second hydraulic pump P2 that has not been delivered to the boom lift cylinder 117 is delivered to the first connecting passage 53 via the merging valve 35. As a result, the second excess oil of the second hydraulic pump P2 can be prevented from being introduced to the second connecting passage 54. In other words, both the first excess oil of the first hydraulic pump P1 and the first excess oil of the second hydraulic pump P2 can be prevented from being introduced to the second connecting passage 54.

[0126] Therefore, the amount of residual oil flowing through the second connecting passage 54 can be appropriately maintained. Consequently, when the load pressure of the boom raising / lowering cylinder 117 decreases, the bypass confluence flow rate can be appropriately suppressed. Consequently, deterioration of the pressure compensation characteristics can be suppressed.

[0127] Furthermore, the first residual oil of the first hydraulic pump P1 and the second residual oil of the second hydraulic pump P2 are not introduced into the second connecting passage 54, thereby appropriately maintaining the amount of residual oil passing through the second connecting passage 54. This allows the flow of hydraulic oil through the second connecting passage 54 to be appropriately controlled, minimizing pressure loss during the passage of the hydraulic oil through the second connecting passage 54 and maintaining good consumption performance.

[0128] exist Figure 5In the description, an example is described in which the first operation switching valve 10 of the first operation switching valves 10 and 11 of the first circuit 2 is operated, and the second operation switching valve 21 of the second operation switching valves 20, 21, and 22 of the second circuit 3 is operated. However, the operation of the operation switching valves is not limited to this example. As another example, the same effect can be obtained even when either the first operation switching valves 10 and 11 or the second operation switching valves 20, 21, and 22 are operated.

[0129] As described above, the hydraulic control circuit 80 of the second embodiment achieves the same effects as those of the first embodiment described above. Specifically, the hydraulic control circuit 80 can automatically merge the first circuit 2 and the second circuit 3 in both directions using a simple structure, thereby suppressing deterioration in the pressure compensation characteristics of the first actuator 111 and the second actuator 115.

[0130] Furthermore, in the hydraulic control circuit 80 of the second embodiment, a second merging valve 82 is provided in the merging circuit 4. Thus, when either the first operation switching valves 10 and 11 of the first circuit 2 is operated or either the second operation switching valves 20, 21, and 22 of the second circuit 3 is operated, the conditions for supplying the excess pressure of the second circuit 3 to the first circuit 2 and the conditions for supplying the excess pressure of the first circuit 2 to the second circuit 3 can be equalized.

[0131] In addition, the present invention is not limited to the above-described embodiment, and includes embodiments in which various modifications are added to the above-described embodiment within a scope that does not depart from the gist of the present invention.

[0132] For example, in the above-described embodiment, a self-propelled crane such as a rough terrain crane is described as an example of the construction machine 100. However, the present invention is not limited thereto, and the above-described hydraulic control circuits 1 and 80 can be employed in various construction machines.

[0133] In the above embodiment, an example is described in which two circuits, the first circuit 2 and the second circuit 3, are provided in the hydraulic control circuit 1 or 80. However, the present invention is not limited thereto, and the hydraulic control circuit 1 or 80 may be provided with two or more circuits.

[0134] In the above-described embodiment, an example is described in which the first operation switching valves 10 and 11 are provided in the first circuit 2 of the hydraulic control circuits 1 and 80, and the second operation switching valves 20, 21, and 22 are provided in the second circuit 3. However, this is not limiting, and the number of operation switching valves provided in the first circuit 2 and the second circuit 3 can be arbitrarily selected.

[0135] In the above embodiment, the first circuit 2 is used as a hoist circuit and the second circuit 3 is used as a boom circuit. However, the present invention is not limited thereto, and the first circuit 2 and the second circuit 3 can be applied to other circuits.

[0136] In addition, in the above-mentioned embodiment, the hydraulic control circuit 1, 80 using working oil is described. However, the structure of the above-mentioned hydraulic control circuit 1, 80 can be applied to various fluids. That is, a fluid control circuit can be provided to replace the hydraulic control circuit 1, 80. Examples of the fluid used in the fluid control circuit include air. In this case, an air pump can be used instead of the first hydraulic pump P1 and the second hydraulic pump P2. In addition, the first actuator 111 and the second actuator 115 can be provided as air actuators that operate using air.

Claims

1. A hydraulic control circuit comprising: a first circuit for supplying first hydraulic oil discharged from a first hydraulic pump to a first actuator via a first operation switching valve; a second circuit for supplying second hydraulic oil discharged from a second hydraulic pump to a second actuator via a second operation switching valve; and a merging circuit for merging the second residual oil in the second circuit with the first hydraulic oil by supplying only the second residual oil in the second circuit to the first operation switching valve, and for merging the first residual oil in the first circuit with the second hydraulic oil by supplying only the first residual oil in the first circuit to the second operation switching valve, The converging circuit has: a first connecting passage including a first neutral fully open passage for merging the second residual oil with the first working oil; a second connecting passage including a second neutral fully open passage for merging the first residual oil and the second working oil; a first check valve provided upstream of the first operation switching valve and connected to the first connecting passage; as well as a second check valve provided on the upstream side of the second operation switching valve and connected to the second connecting passage; The second excess oil in the first connecting passage merges with the first hydraulic oil via the first check valve. The first excess oil in the second connecting passage merges with the second hydraulic oil via the second check valve. The first connecting passage connects the first operation switching valve to the tank. The second connection passage connects the second operation switching valve to a tank.

2. The hydraulic control circuit according to claim 1, wherein: The hydraulic control circuit is provided with: a first flow regulating valve connected between the first hydraulic pump and the first operation switching valve, and controlling a flow rate of either the first hydraulic oil or the first residual oil supplied to the first operation switching valve; as well as A second flow regulating valve is connected between the second hydraulic pump and the second operation switching valve, and controls a flow rate of either the second hydraulic oil or the second residual oil supplied to the second operation switching valve.

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