JP5342293B2 - Hydraulic circuit for construction machinery - Google Patents

Description

  The present invention relates to a hydraulic circuit of a construction machine.

  A hydraulic excavator, which is a construction machine, includes a plurality of operating parts such as a lower traveling body (base), an upper swing body, a boom, an arm, and a bucket, and is widely used for construction work and the like.

  Often, these multiple actuation sites of a hydraulic excavator are actuated simultaneously. For example, when performing excavation work, which is a general work of a hydraulic excavator, simultaneous operation (combined operation) in which a boom and an arm are simultaneously operated is often performed. In order to smoothly perform such simultaneous operation, a tandem hydraulic circuit is used.

  Here, when performing leveling work especially during excavation work, the total amount of oil required to drive the boom cylinder is usually smaller than the total amount of oil required to drive the arm cylinder, but the boom cylinder is driven. The drive pressure required to do this is greater than the drive pressure required to drive the arm cylinder.

  As a technique corresponding to this, in FIG. 8 of Patent Document 1 and Patent Document 2, a fixed throttle 116 is provided in the bypass bypass oil passage 114 as in the hydraulic circuit 100 shown in FIG. A technique is described in which the pressure oil flowing into the oil passage 114 is limited, the driving pressure required to drive the boom cylinder 102 is ensured, and the combined operability is ensured.

  On the other hand, in the latter half of the excavation work, the boom lever 118A of the boom remote control lever device 118 is returned to the neutral position direction, and the spool of the boom switching valve 120 moves in the neutral position direction and is supplied to the boom cylinder 102. However, the pressure oil supplied from the first hydraulic pump 122 to the arm cylinder 104 increases.

  Here, the opening degree of the tandem passage 120T of the boom switching valve 120 is limited to ensure the driving pressure required to drive the boom cylinder 102, and the tandem passage 120T is supplied to the arm cylinder 104 through the tandem passage 112. The pressure oil from the first hydraulic pump 122 passes through a portion where the opening degree of the tandem passage 112 is not large (the tandem passage 120T of the boom switching valve 120). Further, the pressure oil from the first hydraulic pump 122 supplied to the arm cylinder 104 through the bypass bypass oil passage 114 also passes through the fixed throttle 116 where the opening degree is not large.

  For this reason, when pressure oil is supplied from the first hydraulic pump 122 to the arm cylinder 104, a throttle loss occurs and energy loss occurs (fuel consumption deteriorates).

  In FIG. 4, reference numeral 106 denotes a boom, 108 denotes an arm, 110 denotes a bucket, 124 denotes an arm remote control lever device, 126 denotes a second hydraulic pump, 128 denotes an arm switching valve, and 130 denotes from the first hydraulic pump 122. This is a merging switching valve for merging the pressure oil and the pressure oil from the second hydraulic pump 126.

  In contrast to the fact that energy loss occurs in the hydraulic circuit 100 shown in FIG. 4, in FIG. 1 of Patent Document 2, as shown in the hydraulic circuit 200 shown in FIG. A technique is described in which the opening of the flow rate adjustment valve 202 is adjusted according to the pilot pressure P1 that drives the spool of the arm switching valve 128 in the arm closing (retraction) direction to suppress energy loss. Has been. In FIG. 5, reference numeral 204 is a proportional solenoid valve, 206 is a pilot hydraulic pump, 208 is a controller, and 210 is a pilot pressure sensor.

  In FIG. 1 of Patent Document 3, a flow rate adjusting valve 302 is provided in the bypass bypass oil passage 114 instead of the fixed throttle 116 as in the hydraulic circuit 300 shown in FIG. A technique is described in which the adjustment is performed according to the discharge pressure P2 of the first hydraulic pump 122 to suppress energy loss. In FIG. 6, reference numeral 304 is a proportional solenoid valve, 306 is a pilot hydraulic pump, 308 is a controller, and 310 is a discharge pressure sensor.

  5 and 6, the same components as those in FIG. 4 are denoted by the same reference numerals.

JP-B-2-16416 Japanese Patent No. 3183815 Japanese Patent No. 3142864

  However, neither the technique shown in FIG. 1 of Patent Document 2 nor the technique shown in FIG. 1 of Patent Document 3 takes into account the operating state of the boom. For this reason, when the boom and the arm are simultaneously operated, the opening degree is adjusted against the operator's intention, and the operability may be impaired. In addition, there is a possibility that a problem that the energy loss is increased due to being kept more than necessary when the arm is operated alone is caused.

  The present invention has been made in view of such problems, and is a construction machine that is less susceptible to operability even during simultaneous operation of a boom and an arm, and that can reduce aperture loss more than in the past. It is an object of the present invention to provide a hydraulic circuit.

The present invention is connected to a first hydraulic pump, connected to a boom switching valve for switching the direction and flow rate of pressure oil supplied to the boom cylinder, and connected to a second hydraulic pump, and supplied to the arm cylinder. An arm switching valve for switching the direction and flow rate of pressure oil, and a merging unit for tandemly connecting the first hydraulic pump to the downstream side of the boom switching valve and for joining the pressure oil supplied to the arm cylinder In the hydraulic circuit of a construction machine comprising a switching valve for bypassing, bypass bypass oil for bypassing connection between a passage for supplying pressure oil to the boom switching valve and a passage for supplying pressure oil to the switching valve for merging The bypass bypass oil passage has a first switching position and a second switching position, and the pressure oil passage is throttled at a predetermined opening at the first switching position. In the second switching position No passage of the hydraulic fluid is throttled, provided the first opening adjustable auxiliary switching valve as opening degree increases as the switching position switches on the second switching position, the auxiliary switching valve Corresponding to a magnitude relationship between a command value for causing the arm switching valve to perform an arm closing operation and a command value for causing the boom switching valve to perform a boom raising operation. If the command value for controlling and performing the arm closing operation does not exceed a preset value more than the command value for performing the boom raising operation, the auxiliary switching valve is moved to the first switching position. controlled to be the command value for causing the arm closing operation in accordance with relatively large Kunar for a command value for causing the boom raising operation, the opening degree of the auxiliary switching valve becomes larger To control Ri is obtained by solving the above problems.

  In the present invention, the opening degree of the auxiliary switching valve provided in the bypass bypass oil passage is set to the command value for causing the arm switching valve to perform the arm closing operation and the boom switching operation to the boom switching valve. As the command value for performing the boom raising operation becomes relatively smaller than the command value for performing the arm closing operation, The opening of the auxiliary switching valve is controlled to be larger.

  For this reason, even if an operation for closing the arm is performed during the operation of raising the boom, the opening degree of the auxiliary switching valve is not easily increased, and it is easy to ensure the driving pressure required to drive the boom cylinder. Even during the simultaneous operation of the boom and arm, it is difficult to adjust the opening degree against the intention of the operator, and the operability is not easily impaired.

  That is, in the present invention, the opening degree of the auxiliary switching valve is controlled in consideration of not only the state of the arm closing operation but also the state of the boom raising operation, so that the operation can be performed even during the simultaneous operation of the arm closing and the boom raising. In addition, it is possible to reduce the throttle loss more appropriately than in the prior art during simultaneous operation of closing the arm and raising the boom, and to suppress the discharge pressure of the first and second hydraulic pumps accordingly. Energy loss can be suppressed as compared with the conventional case.

  The control performed in accordance with the magnitude relationship is, for example, a command for causing the boom switching valve to perform a boom raising operation from a command value for causing the arm switching valve to perform an arm closing operation. The control can be performed in accordance with the difference obtained by subtracting the value.

  Further, for example, a command value for causing the arm switching valve to perform an arm closing operation is a pilot pressure for commanding the arm switching operation to the arm switching valve, and The command value for performing the boom raising operation may be a pilot pressure for commanding the boom raising operation to the boom switching valve.

  Further, a pressure sensor for detecting the pilot pressure may be provided, the magnitude relationship may be calculated from the detected value of the pressure sensor, and the opening degree of the auxiliary switching valve may be controlled based on the magnitude relationship. .

  According to the present invention, the opening of the auxiliary switching valve (opening of the bypass bypass oil passage) is controlled in consideration of not only the state of the arm closing operation but also the state of the boom raising operation. Even at the time, the operability is not easily lost, and the aperture loss can be reduced as compared with the conventional case.

The figure which shows the structure of the hydraulic circuit of the hydraulic shovel which concerns on 1st Embodiment of this invention. The graph which shows typically the relationship between the opening degree (opening area S) of the auxiliary switching valve 24, and differential pressure | voltage (DELTA) P. The figure which shows the structure of the hydraulic circuit of the hydraulic shovel which concerns on 2nd Embodiment of this invention. The figure which shows the structure of the hydraulic circuit of the conventional hydraulic shovel (FIG. 8 of patent document 2) The figure which shows the structure of the hydraulic circuit of the conventional hydraulic shovel (FIG. 1 of patent document 2) The figure which shows the structure of the hydraulic circuit of the conventional hydraulic shovel (FIG. 1 of patent document 3)

  Hereinafter, an example of a preferred embodiment of a hydraulic circuit of a hydraulic excavator (construction machine) according to the present invention will be described in detail based on the drawings.

  FIG. 1 is a diagram showing a configuration of a hydraulic circuit of a hydraulic excavator according to the first embodiment of the present invention.

  The hydraulic circuit 10 includes a first hydraulic pump 12, a second hydraulic pump 14, a tandem passage 16, a boom switching valve 18, a merging switching valve 20, a bypass bypass oil path 22, and an auxiliary switching valve 24. And an arm switching valve 26, supplying pressure oil to the boom cylinder 80 and the arm cylinder 82, operating the boom 84 and the arm 86, and causing the excavator 70 to perform various operations such as excavation work. . Reference numeral 88 denotes a bucket.

  The first hydraulic pump 12 and the second hydraulic pump 14 are arranged in parallel. A tandem passage 16 is connected to the first hydraulic pump 12, and pressure oil supplied from the first hydraulic pump 12 is supplied to the boom cylinder 80 and the arm cylinder 82 via the tandem passage 16. The tandem passage 16 is provided with a boom switching valve 18 on the upstream side and a merging switching valve 20 on the downstream side.

  The boom switching valve 18 is a three-position six-port switching valve, and includes three switching positions A, B, and C, and controls the direction and flow rate of pressure oil from the first hydraulic pump 12 toward the boom cylinder 80. To do. Pilot ports 18a and 18b are respectively provided at both ends of the spool of the boom switching valve 18, and pilot pressure is supplied from the pilot oil passages 32a and 32b, respectively.

  The spool of the boom switching valve 18 moves when the operator operates the boom remote control lever device 32, and controls the direction and flow rate of hydraulic oil supplied to the boom cylinder 80. The pressure oil supplied from the first hydraulic pump 12 to the boom cylinder 80 is supplied from the tandem passage 16 through the boom switching valve 18 to the boom cylinder 80 through the boom oil passages 90a and 90b.

  The arm switching valve 26 is a three-position six-port switching valve, and has three switching positions D, E, and F, and controls the direction and flow rate of pressure oil from the second hydraulic pump 14 toward the arm cylinder 82. To do. Pilot ports 26a and 26b are respectively provided at both ends of the spool of the arm switching valve 26, and pilot pressure is supplied from the pilot oil passages 36a and 36b, respectively.

  The spool of the arm switching valve 26 moves when the operator operates the arm remote control lever device 34, and controls the direction and flow rate of the pressure oil supplied to the arm cylinder 82. The pressure oil supplied from the second hydraulic pump 14 to the arm cylinder 82 is supplied to the arm cylinder 82 through the arm switching valve 26 and the arm oil passages 92a and 92b.

  The bypass bypass oil passage 22 has a role of bypassing the pressure oil discharged from the first hydraulic pump 12 to the supply port p1 of the merging switching valve 20 without passing through the boom switching valve 18. When the spool of the boom switching valve 18 is in the switching position B (neutral position), the pressure oil from the first hydraulic pump 12 is not supplied to the boom cylinder 80 and joins through the tandem passage 18T of the boom switching valve 18. In addition to being supplied to the supply port p <b> 1 of the switching valve 20 for use, it is supplied to the supply port p <b> 1 of the switching valve 20 for joining through the bypass bypass oil passage 22. When the spool of the boom switching valve 18 is at the switching positions A and C, the pressure oil discharged from the first hydraulic pump 12 is supplied to the boom cylinder 80 through the tandem passage 16 and also passes through the bypass bypass oil passage 22. And then supplied to the arm cylinder 82.

  The auxiliary switching valve 24 is a two-position / two-port switching valve provided in the middle of the bypass bypass oil passage 22, and has two switching positions J and K, and switches for merging through the bypass bypass oil passage 22. It has a role of controlling the amount of pressure oil supplied to the supply port p1 of the valve 20. A throttle 25 is provided in the passage at the switching position J, and no throttle is provided in the passage at the switching position K. As the switching position J is switched to the switching position K, the opening degree (opening area S) is increased. It is getting bigger.

  Pilot ports 24a and 24b are provided at both ends of the spool of the auxiliary switching valve 24, respectively. A pilot pressure (command value for causing the arm closing operation) to drive the arm 86 in the closing (withdrawing) direction is transmitted to the pilot port 24a via the pilot oil passage 36a and the pilot oil passage 24a1. The pilot pressure (command value for performing the boom raising operation) that drives the boom 84 in the raising direction is transmitted through the pilot oil passage 32a and the pilot oil passage 24b1. Therefore, the position of the spool of the auxiliary switching valve 24 is switched based on the differential pressure (magnitude relationship) between the pilot pressure that drives the arm 86 in the closing direction and the pilot pressure that drives the boom 84 in the upward direction.

  Further, a spring 24c is provided at the end on the switching position J side. The spool of the auxiliary switching valve 24 is biased to the switching position J by the spring 24c. Therefore, in order for the spool of the auxiliary switching valve 24 to switch from the switching position J to the switching position K, the differential pressure ΔP obtained by subtracting the pilot pressure that drives the boom 84 from the pilot pressure that drives the arm 86 in the closing direction. However, it is necessary to exceed the urging force of the spring 24c. Therefore, by adjusting the urging force by the spring 24c, the differential pressure ΔP0 (threshold value) at the start of switching when the spool of the auxiliary switching valve 24 switches from the switching position J to the switching position K can be set. . As shown in FIG. 2, until the pressure difference ΔP0 is reached, the opening degree (opening area S) of the auxiliary switching valve 24 is Smin, and this opening degree is the opening degree of the throttle 25. When the differential pressure ΔP exceeds the differential pressure ΔP0, the opening degree (opening area S) of the auxiliary switching valve 24 increases as the differential pressure ΔP increases. When the differential pressure ΔP reaches a predetermined differential pressure ΔP1, the maximum value Smax is reached. Thereafter, even when the differential pressure ΔP increases, the opening degree (opening area S) of the auxiliary switching valve 24 remains at the maximum value Smax.

  The merging switching valve 20 is a three-position six-port switching valve, and includes three switching positions G, H, and I. The flow direction and flow rate of pressure oil from the first hydraulic pump 12 to the boom cylinder 80 are controlled. Control. Pilot ports 20a and 20b are respectively provided at both ends of the spool of the merging switching valve 20, and pilot pressure is supplied from the pilot oil passages 36a and 36b, respectively.

  The merging switching valve 20 is provided downstream of the boom switching valve 18 in the tandem passage 16 and is tandemly connected to the boom switching valve 18. Ports p2 and p3 on the downstream side of the merging switching valve 20 are connected to arm oil passages 92a and 92b.

  When the operation lever 34A of the arm remote control lever device 34 is tilted to the left in FIG. 1 and the pilot pressure is supplied to the pilot oil passage 36a, the pilot pressure is supplied to the pilot port 26a of the arm switching valve 26. The switching valve for arm 26 is set to the switching position D and the switching valve 20 for merging is set to the switching position G. Thereby, the pressure oil is supplied from the second hydraulic pump 14 to the arm oil passage 92a, and the pressure oil from the first hydraulic pump 12 is also supplied to the arm oil passage 92a. As a result, the bottom chamber of the arm cylinder 82 is supplied with a sufficient amount of pressure oil, and the arm 86 is closed.

  When the operation lever 34A of the arm remote control lever device 34 is tilted to the right and the pilot pressure is supplied to the pilot oil passage 36b, the pilot pressure is supplied to the pilot port 26b of the arm switching valve 26, and It is supplied to the pilot port 20b of the merging switching valve 20, and the arm switching valve 26 is set to the switching position F and the merging switching valve 20 is set to the switching position I. Thereby, the pressure oil is supplied from the second hydraulic pump 14 to the arm oil passage 92b, and the pressure oil from the first hydraulic pump 12 is also supplied to the arm oil passage 92b. As a result, the rod chamber of the arm cylinder 82 is supplied with a sufficient amount of pressure oil, and the arm 86 opens.

  As described above, the merging switching valve 20 has a role of supplying the pressure oil from the first hydraulic pump 12 to the arm cylinder 82 in the same direction as the pressure oil supplied from the second hydraulic pump 14 to the arm cylinder 82. .

  Next, the operation and action of the hydraulic circuit 10 according to the first embodiment configured as described above will be described.

  When excavation work is performed by the hydraulic excavator 70, first, a preparation operation is performed to tilt the boom 84 forward and open the arm 86 forward. From this state, the boom 84 is raised upward and the arm 86 is driven toward the front and closed, and the bucket 88 is pulled toward the front to perform excavation work.

  When performing the preparatory operation, the operation lever 32A of the boom remote control lever device 32 is tilted to the left in FIG. 1, and the pilot pressure is supplied to the pilot port 18b via the pilot oil passage 32b to switch the boom. Switching the spool of the valve 18 to the switching position C, supplying pressure oil to the rod chamber of the boom cylinder 80 to tilt the boom 84 forward, and tilting the operation lever 34A of the arm remote control lever device 34 to the right in FIG. The pilot pressure is supplied to the pilot port 26b through the pilot oil passage 36b to switch the spool of the arm switching valve 26 to the switching position F, and the pilot pressure is applied to the pilot port 20b through the pilot oil passage 36b. Supply and switch the spool of the merging switching valve 20 to the switching position I; To supply pressure oil to the rod chamber of Mushirinda 82 opening the arms 86 forward.

  During this preparatory operation, the operating lever 34A of the arm remote control lever device 34 is tilted to the right in FIG. 1, and no pilot pressure is supplied to the pilot oil passage 36a. Pilot pressure is not supplied to the port 24a. Further, the control lever 32A of the boom remote control lever device 32 is tilted to the left in FIG. 1, no pilot pressure is supplied to the pilot oil passage 32a, and the pilot pressure is applied to the pilot port 24b of the auxiliary switching valve 24. Is not supplied. On the other hand, the spool of the auxiliary switching valve 24 is biased toward the switching position J by the spring 24C. For this reason, the spool of the auxiliary switching valve 24 is in the switching position J, and the boom driving pressure is secured by the throttle 25.

  After performing this preparatory operation, the boom 84 is raised upward and the arm 86 is pulled toward the front and driven in the closing direction, and the bucket 88 is pulled toward the front to perform excavation work. In this excavation work, the upward raising of the boom 84 is almost completed in the first half. When the boom 84 is raised upward (the first half of the excavation work), the reaction force caused by excavating the ground acts on the boom 84 in the direction opposite to the weight of the arm 86. The required boom drive pressure is not particularly large. On the other hand, the operation of closing the arm 86 is performed throughout the excavation work, and the arm 86 needs to always resist the reaction force caused by excavating the ground, so that the driving pressure required to drive the arm 86 is large. . For this reason, in the first half of the excavation work, the drive pressure required to drive the arm 86 is greater than the drive pressure required to drive the boom 84. However, in order to return the return oil from the boom 84 to the tank, the operation lever 32A of the boom remote control lever device 32 needs to be appropriately tilted.

  Here, in the first half of the excavation work, the operation lever 32A of the boom remote control lever device 32 is tilted to the right in FIG. 1 in order to raise the boom 84 upward, and the pilot oil passage 32a is piloted. When the pressure is supplied, the spool of the boom switching valve 18 is switched to the switching position A, and the pilot pressure is supplied to the pilot port 24 b of the auxiliary switching valve 24. Further, in order to close the arm 86 at the same time, the operation lever 34A of the arm remote control lever device 34 is tilted to the left side in FIG. 1, and the pilot pressure is supplied to the pilot oil passage 36a. Pilot pressure is supplied to the pilot port 24a of the auxiliary switching valve 24 via the path 24a1.

  Therefore, in the first half of the excavation work, pilot pressure is applied to both sides of the spool of the auxiliary switching valve 24, and the differential pressure obtained by subtracting the pilot pressure supplied to the pilot port 24b from the pilot pressure supplied to the pilot port 24a. ΔP (the differential pressure obtained by subtracting the pilot pressure for instructing the boom switching valve 18 to raise the boom from the pilot pressure for instructing the arm closing operation to the arm switching valve 26) is small. In addition, a spring 24C is provided at the end on the switching position J side, and the spool of the auxiliary switching valve 24 is urged in the direction of the switching position J to apply a predetermined amount of force. For this reason, in the first half of the excavation work, the differential pressure ΔP does not exceed the differential pressure ΔP0, the spool of the auxiliary switching valve 24 becomes the switching position J, and the amount of pressure oil flowing through the bypass bypass oil passage 22 by the throttle 25 is limited. In the first half of excavation work, the boom drive pressure is secured.

  In the latter half of the excavation work after the boom 84 rises upward, the operation lever 32A of the boom remote control lever device 32 starts to return to the neutral position, and the pilot pressure is not supplied to the pilot oil passage 32a. The pilot pressure is not supplied to the pilot port 24b, and the spool of the boom switching valve 18 is switched to the switching position B, and the tandem passage 16 is communicated. On the other hand, the operation of closing the arm 86 is continued even in the latter half of the excavation work after the boom 84 rises approximately upward, and the operation lever 34A of the arm remote control lever device 34 is left to the left in FIG. The pilot pressure is continuously supplied to the pilot port 24a of the auxiliary switching valve 24. Therefore, as the operation lever 32A of the boom remote control lever device 32 is returned to the neutral position, the differential pressure ΔP obtained by subtracting the pilot pressure supplied to the pilot port 24b from the pilot pressure supplied to the pilot port 24a increases. When the differential pressure ΔP overcomes the biasing force of the spring 24c (ΔP> ΔP0), the spool of the auxiliary switching valve 24 is switched from the switching position J to the switching position K, and the opening degree of the auxiliary switching valve 24 is accordingly increased. The squeezing loss of the pressure oil flowing through the bypass bypass oil passage 22 becomes smaller as the pressure increases.

  As described above, in this embodiment, the spool of the auxiliary switching valve 24 is switched to the switching position K as the differential pressure ΔP increases, but when the operation of raising the boom 84 is being performed, the pilot pressure is applied to the pilot port 24b. Therefore, even if the operation of closing the arm 86 is performed, the differential pressure ΔP does not exceed the differential pressure ΔP 0, and the spool of the auxiliary switching valve 24 remains at the switching position J. Is secured and the operability is not easily lost.

  When the operation lever 34A of the arm remote control lever device 34 is tilted to the left in FIG. 1, the pilot pressure supplied to the pilot port 24a increases and the differential pressure ΔP increases, and the arm remote control lever When the operation lever 34A of the device 34 is in the neutral position or tilted to the right in FIG. 1, the pilot pressure supplied to the pilot port 24a is reduced and the differential pressure ΔP is reduced. When the operation lever 32A of the boom remote control lever device 32 is tilted to the right in FIG. 1, the pilot pressure supplied to the pilot port 24b is increased and the differential pressure ΔP is decreased. When the control lever 32A is in the neutral position or tilted to the left in FIG. 1, the pilot pressure supplied to the pilot port 24b decreases and the differential pressure ΔP increases. Therefore, in the present embodiment, both the operation state of the operation lever 32A of the boom remote control lever device 32 and the operation state of the operation lever 34A of the arm remote control lever device 34 are reflected in the differential pressure ΔP.

  In this embodiment, as the differential pressure ΔP increases, the amount by which the spool of the auxiliary switching valve 24 switches from the switching position J to the switching position K increases, and the amount of pressure oil that passes through the throttle 25 decreases. In this embodiment in which both the operation state of the operation lever 32A of the boom remote control lever device 32 and the operation state of the operation lever 34A of the arm remote control lever device 34 are reflected in the differential pressure ΔP, the boom 84 and the arm 86 are simultaneously operated. In excavation work or the like that is operated, the throttle loss can be appropriately reduced as compared with the prior art, and the discharge pressures of the first hydraulic pump 12 and the second hydraulic pump 14 can be suppressed correspondingly, thereby reducing the energy loss. Than can be suppressed.

  For example, during the arm closing operation, the operation lever 34A of the arm remote control lever device 34 is tilted to the left in FIG. 1, and the pilot pressure commanding the arm closing operation is supplied to the arm switching valve 26. However, when the operation lever 32A of the boom remote control lever device 32 starts to return to the neutral position, the pilot pressure supplied to the pilot port 24b decreases, the differential pressure ΔP increases, and the spool of the auxiliary switching valve 24 becomes Since the amount of pressure oil passing through the restrictor 25 is reduced and the amount of pressure oil passing through the restrictor 25 is reduced, the restrictor loss can be reduced more appropriately than in the prior art.

  Further, since the amount of switching of the spool of the auxiliary switching valve 24 from the switching position J to the switching position K is based on a combined lever operation of the arm closing and boom raising by the operator, operability according to the operator's intention is ensured. You can also.

  In this embodiment, pilot pressure is used as a command value for performing the boom raising operation and a command value for performing the arm closing operation, and the opening degree of the auxiliary switching valve 24 is controlled based on the differential pressure ΔP. However, the parameter used as the command value for performing the boom raising operation and the command value for performing the arm closing operation may not be the pilot pressure. For example, the operation amount of the operation levers 32A and 34A It may be.

  Further, as the command value for performing the boom raising operation becomes relatively smaller than the command value for performing the arm closing operation, the spool of the auxiliary switching valve 24 is switched to the switching position K (auxiliary). If the configuration is such that the opening degree of the switching valve 24 is increased), for example, not the “difference” but the “size” of the command value for performing the boom raising operation and the command value for performing the arm closing operation. It is good also as a structure which performs the opening degree control of the auxiliary | assistant switching valve 24 according to "the ratio".

  Next, a hydraulic circuit 40 for a hydraulic excavator according to a second embodiment of the present invention will be described.

  FIG. 3 is a diagram showing a configuration of a hydraulic circuit 40 of a hydraulic excavator according to the second embodiment of the present invention. The same components as those of the hydraulic circuit 10 according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the hydraulic circuit 10 according to the first embodiment, the pilot pressure for instructing the arm switching operation to the arm switching valve 26 and the pilot pressure for instructing the boom switching valve 18 to raise the boom are directly applied to the auxiliary switching valve 24. Although supplied, in the hydraulic circuit 40 according to the second embodiment, as shown in FIG. 3, the pilot pressure (pilot pressure in the pilot oil passage 32a) for commanding the arm switching operation to the arm switching valve 26 is applied. In addition to providing a pressure sensor 42 for detection, a pressure sensor 44 for detecting a pilot pressure (pilot pressure in the pilot oil passage 36a) for instructing the boom switching valve 18 to raise the boom is provided, and the pressure sensors 42 and 44 measure the pressure. Based on the pressure data, the controller 48 calculates the differential pressure ΔP (or a ratio).

  Further, in the hydraulic circuit 40 according to the second embodiment, instead of the auxiliary switching valve 24 of the hydraulic circuit 10 according to the first embodiment, only one end of the spool (the end on the switching position M side described later) is provided. An auxiliary switching valve 54 provided with a pilot port 54a is provided, and a proportional solenoid valve 50 for controlling the pilot pressure supplied to the pilot port 54a of the auxiliary switching valve 54 is provided.

  The auxiliary switching valve 54 is a two-position two-port switching valve provided in the bypass bypass oil passage 22, has two switching positions L and M, passes through the bypass bypass oil passage 22, and the switching valve 20 for merging. It has a role which controls the quantity of the pressure oil supplied to the supply port p1. The passage at the switching position L is provided with a throttle 55, and the passage at the switching position M is not provided with a throttle. As the switching position L is switched to the switching position M, the opening degree (opening area S) is increased. It is getting bigger.

  The pressure data measured by the pressure sensors 42 and 44 is sent to the controller 48 via the electric signal lines 46a and 46b, respectively. The controller 48 calculates the differential pressure ΔP, and the electric signal line 46c is transmitted based on the calculated differential pressure ΔP. An electrical signal is sent from the controller 48 to the proportional solenoid valve 50 to control the opening of the proportional solenoid valve 50, and the pilot pressure input from the pilot hydraulic pump 52 to the pilot port 54a of the auxiliary switching valve 54 is controlled. The

  Specifically, the controller 48 controls the spool of the auxiliary switching valve 54 to start switching from the switching position L to the switching position M when the calculated differential pressure ΔP exceeds a predetermined value, and the differential pressure ΔP. And the opening degree (opening area S) of the auxiliary switching valve 54 are controlled so as to be as shown in FIG. 2 as in the case of the first embodiment, for example.

  In the hydraulic circuit 40 according to the second embodiment, the controller 48 controls the pilot pressure input to the pilot port 54a of the auxiliary switching valve 54 by controlling the opening of the proportional solenoid valve 50 based on the calculated differential pressure ΔP. Control other than the control in which the relationship between the differential pressure ΔP and the opening degree (opening area S) of the auxiliary switching valve 54 becomes a linear function as shown in FIG. 2 is possible. The relationship with the degree (opening area S) can be an arbitrary function, and fine control according to the situation is possible.

  In the hydraulic circuit 40 according to the second embodiment, two pressure sensors (pressure sensors 42 and 44) are provided. However, the pilot pressure (pilot oil passage) that instructs the arm switching valve 26 to perform an arm closing operation is provided. 32a) and a pilot pressure for instructing the boom switching valve 18 to raise the boom (a pilot pressure in the pilot oil passage 36a) are input to one pressure sensor, and a differential pressure ΔP is obtained by the one pressure sensor. The data may be detected.

  Although the hydraulic circuits 10 and 40 according to the first and second embodiments of the present invention have been described above, the present invention is applicable without depending on a pump control system such as a positive control, a negative control, or an open center. .

  For example, it can be suitably used for a hydraulic excavator that frequently performs simultaneous operation (combined operation) for simultaneously operating a boom and an arm.

DESCRIPTION OF SYMBOLS 10, 40 ... Hydraulic circuit 12 ... 1st hydraulic pump 14 ... 2nd hydraulic pump 16 ... Tandem passage 18 ... Boom switching valve 20 ... Junction switching valve 22 ... Detour bypass oil path 24, 54 ... Auxiliary switching valve 25, 55 ... Throttle 26 ... Switch valve for arm 32 ... Remote control lever device for boom 34 ... Remote control lever device for arm 32A, 34A ... Operating lever 42,44 ... Pressure sensor 48 ... Controller 50 ... Proportional solenoid valve 52 ... Pilot hydraulic pump 70 ... Hydraulic pressure Shovel 80 ... Boom cylinder 82 ... Arm cylinder 84 ... Boom 86 ... Arm 88 ... Bucket ΔP ... Differential pressure S ... Opening area

Claims (4)

A boom switching valve connected to the first hydraulic pump for switching the direction and flow rate of the pressure oil supplied to the boom cylinder;
An arm switching valve connected to the second hydraulic pump for switching the direction and flow rate of the pressure oil supplied to the arm cylinder;
A merging switching valve that is tandemly connected to the first hydraulic pump downstream of the boom switching valve, and for joining the pressure oil supplied to the arm cylinder;
In the hydraulic circuit of construction machinery with
While providing a bypass bypass oil passage that bypasses between a passage for supplying pressure oil to the boom switching valve and a passage for supplying pressure oil to the junction switching valve,
The bypass bypass oil passage has a first switching position and a second switching position. In the first switching position, the passage of pressure oil is throttled at a predetermined opening and the second switching position. A pressure oil passage is not throttled at the position, and an auxiliary switching valve capable of opening adjustment is provided so that the opening increases as the first switching position is switched to the second switching position ;
The magnitude of the opening of the auxiliary switching valve between a command value for causing the arm switching valve to perform an arm closing operation and a command value for causing the boom switching valve to perform a boom raising operation In response to
When the command value for performing the arm closing operation does not exceed the preset value for performing the boom raising operation, the auxiliary switching valve is set to the first switching position. Control to
Characterized in that the command value for causing the arm closing operation in accordance with relatively large Kunar for a command value for causing the boom raising operation, the opening degree of the auxiliary switching valve is controlled to be greater And the hydraulic circuit of construction machinery. In claim 1,
The control performed in accordance with the magnitude relationship is a command value for causing the boom switching valve to perform a boom raising operation from a command value for causing the arm switching valve to perform an arm closing operation. A hydraulic circuit for a construction machine, characterized in that the control is performed in response to a reduced difference. In claim 1 or 2,
The command value for causing the arm switching valve to perform the arm closing operation is a pilot pressure commanding the arm switching operation to the arm switching valve, and the boom raising operation is performed to the boom switching valve. A hydraulic pressure circuit for a construction machine, wherein the command value for performing the operation is a pilot pressure for commanding a boom raising operation to the boom switching valve. In claim 3,
A pressure sensor for detecting the pilot pressure is provided;
A hydraulic circuit for a construction machine, wherein the magnitude relationship is calculated from a detection value of the pressure sensor, and the opening degree of the auxiliary switching valve is controlled based on the magnitude relationship.

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