JP2011247365A - Hydraulic circuit of construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic circuit of a construction machine which employs a two-pump system, and which is excellent in combined operability.SOLUTION: The hydraulic circuit includes straight traveling valve adjusting means 72, 24, 46 for adjusting a switching position of a straight traveling valve 34. When a travel operation is not carried out and a work actuator 82 is operated by a first work control valve 16, the switching position of the straight traveling valve 34 is adjusted to supply a hydraulic oil from a second hydraulic pump 32 to the first work control valve 16. The hydraulic circuit is excellent in combined operability.

Description

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

  2. Description of the Related Art In a hydraulic circuit of a construction machine such as a hydraulic excavator, a hydraulic circuit of a two-pump system is used in which discharge oils of two hydraulic pumps are merged as necessary and supplied to a hydraulic actuator that requires a large flow rate.

  FIG. 3 shows an example of such a hydraulic circuit (see FIG. 7 of Patent Document 1).

  The first group of control valves (the left traveling hydraulic motor control valve 104, the first boom cylinder control valve 106, the second arm cylinder control valve 108, and the bucket cylinder control valve 110) are supplied from the first hydraulic pump 102. The hydraulic oil supplied to and discharged from each actuator (left traveling hydraulic motor, first boom cylinder, second arm cylinder, bucket cylinder 112) is controlled, and each control valve of the second group (control valve for right traveling hydraulic motor) 124, the first arm cylinder control valve 126, the second boom cylinder control valve 128, and the swing hydraulic motor control valve 130 are hydraulic actuators supplied from the second hydraulic pump 122 (right traveling hydraulic motor, Controls the supply and discharge to and from the 1-arm cylinder, the second boom cylinder, and the swing hydraulic motor. Further, a merging switching valve 140 is provided, and when the merging switching valve 140 is switched to the merging position b, the discharge oil of the second hydraulic pump 122 merges with the discharge oil of the first hydraulic pump at the merging point K, and the bucket cylinder 112 The cylinder can be operated at high speed.

  On the other hand, in the hydraulic circuit of FIG. 3, since the maximum discharge amount of the second hydraulic pump 122 is always merged with the discharge oil of the first hydraulic pump 102 at the time of merging, in the case (machine, work type, operator preference, etc. ), The flow rate was excessive and the bucket acted too fast, and on the contrary, the operability deteriorated.

  On the other hand, Patent Document 1 discloses a hydraulic circuit shown in FIG. 4 (the same reference numerals are assigned to the same parts as in FIG. 3), and at the time of merging, merging control means (controller 150, electromagnetic The proportional valve 152) controls the combined oil amount of the discharge oil of the second hydraulic pump 122 in accordance with the command speed for the bucket cylinder 112, and this combined oil amount increases as the command speed increases and decreases as the command speed decreases. The method of changing the speed of the bucket cylinder 112 can be adapted to the operator's request.

  In the hydraulic circuit shown in FIG. 4, at least one of the control valves 126, 128, and 130 (boom, arm, or swivel) other than the control valve 124 for the right traveling hydraulic motor of the second group is operated during merging. If the remote control pressure Pa or Pt is input to the controller 150, the signal output to the electromagnetic proportional valve 152 is stopped, and the operation of the boom arm and the turning operation can be performed without any trouble.

Japanese Patent No. 3961123

  However, at least one of the control valves 126, 128, and 130 excluding the control valve 124 for the right traveling hydraulic motor of the second group (boom, arm, etc.) even during merging where the merging oil is being supplied to the bucket cylinder 112. (Or swiveling) is released, the merging is canceled. Therefore, in the combined operation in which the boom, arm and swiveling operation is performed in addition to the operation of the bucket, the supply of hydraulic oil to the bucket cylinder 112 is insufficient and the smooth combining is performed. Operation may not be possible.

  This invention is made | formed in view of this problem, and makes it a subject to provide the hydraulic circuit which is excellent in composite operativity in the hydraulic circuit of the construction machine of a 2 pump system.

  The present invention includes a first hydraulic pump and a second hydraulic pump, and a first traveling control valve for one traveling hydraulic motor is disposed in a first center oil passage of the first hydraulic pump, and the first hydraulic pump is provided. A first work control valve for the work actuator is disposed downstream of the travel control valve in the first center oil passage, and a travel straight valve is disposed in the second center oil passage of the second hydraulic pump. A second travel control valve for the other travel hydraulic motor is disposed downstream of the second center oil passage, and a second work control valve for another work actuator is disposed downstream of the second center oil passage of the second travel control valve. In the hydraulic circuit of the construction machine provided with a travel straight travel valve adjusting means for adjusting the switching position of the travel straight travel valve is provided, the travel operation is not performed, and the work actuator is operated by the first work control valve Adjusts the switching position of the straight travel valve. Te, hydraulic fluid from the second hydraulic pump to the first working control valve by which as supplied, is obtained by solving the above problems.

  In the present invention, since it is configured as described above, the hydraulic oil from the second hydraulic pump is used as the first work control valve in the combined operation state by utilizing the straight traveling valve when the traveling operation is not performed. Accordingly, the combined operability can be improved without adding a configuration in the hydraulic circuit of the construction machine of the two-pump system.

  In the hydraulic circuit, a cut valve that is provided downstream of the second work control valve in the second center oil passage and switches between communication and shut-off, and a second valve between the cut valve and the second work control valve. When a bypass oil passage that connects a point of the two center oil passages to a point of the first center oil passage between the first travel control valve of the first center oil passage and the first work control valve is provided, When the hydraulic fluid from the second hydraulic pump is supplied to the first work control valve by adjusting the switching position of the straight travel valve, the hydraulic fluid from the first hydraulic pump The entire amount can be used for the operation of the actuator operated by the first work control valve.

  In the hydraulic circuit, the switching position of the straight travel valve may be adjusted based on a pilot pressure supplied to the first work control valve and a pilot pressure supplied to the second work control valve.

  The switching position of the traveling straight valve may be adjusted based on the switching amount from the neutral position of the first work control valve and the switching amount from the neutral position of the second work control valve.

  ADVANTAGE OF THE INVENTION According to this invention, the hydraulic circuit excellent in composite operativity can be provided in the hydraulic circuit of the construction machine of a 2 pump system.

The figure which shows the whole structure of the hydraulic circuit which concerns on embodiment of this invention In the embodiment, an opening diagram schematically showing the relationship between the switching amount of the travel straight valve 34 in the switching position B direction and the opening of the four oil passages p, q, r, and s of the travel straight valve 34. The figure which shows an example of the hydraulic circuit of the conventional 2 pump system The figure which shows an example of the hydraulic circuit of the conventional 2 pump system by which adjustment of merging oil amount is made

  Hereinafter, an example of a preferred embodiment of a hydraulic circuit for a construction machine according to the present invention will be described in detail with reference to the drawings.

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

  The hydraulic circuit 10 is disposed downstream of the first hydraulic pump 12 and the first center oil passage 56 of the first hydraulic pump 12, and each actuator of the first group (the left traveling hydraulic motor 80, the specific actuator 82, the turning use). Each control valve (control valve for left travel hydraulic motor (first travel control valve) 14) for controlling supply and discharge of hydraulic fluid to and from the hydraulic motor 84, the second boom cylinder 86, and the first arm cylinder 88), Specific actuator control valve (first work control valve) 16, turning control valve 18, second boom control valve 20, first arm control valve 22), second hydraulic pump 32, and second hydraulic pump 32 The second center oil passage 60 is actuated on each actuator of the second group (right traveling hydraulic motor 90, bucket cylinder 92, first boom cylinder 94, second arm cylinder 96). Control valves (second traveling hydraulic motor control valve (second traveling control valve) 36, bucket control valve (second working control valve) 38, first boom control valve 40, which control the supply and discharge of The second arm control valve 42), the traveling straight valve 34, the cut valve 44 provided on the downstream side (the most downstream side) of the second center oil passage 60 with respect to the second arm control valve 42, the first Merge switching valve 24, second merge switching valve 46, pressure sensors 48, 50, 52, first center oil passage 56, first parallel oil passage 58, second center oil passage 60, and second parallel. An oil passage 62, a bypass oil passage 64, and a controller 72 are provided. The specific actuator 82 is an actuator added according to the type and application of the construction machine.

  The traveling straight valve 34 is provided in a second center oil passage 60 between the second hydraulic pump 32 and the right traveling hydraulic motor control valve 36. Two switching positions A and B are provided, and the switching position A is used when the operation of the work actuators 82, 84, 86, 88, 92, 94, 96 used for work and the traveling by the traveling hydraulic motors 80, 90 are not performed simultaneously. Correspondingly, the switching position B corresponds to the case where the operation of the work actuators 82, 84, 86, 88, 92, 94, 96 used for work and the travel by the travel hydraulic motors 80, 90 are performed simultaneously (hereinafter referred to as simultaneous operation). ).

  In other words, at the switching position A, the hydraulic oil discharged from the first hydraulic pump 12 is supplied to the left traveling hydraulic motor 80 and the work actuators 82, 84, 86, 88 of the first group and discharged from the second hydraulic pump 32. The hydraulic oil thus supplied is supplied to the right traveling hydraulic motor 90 and the work actuators 92, 94, 96 of the second group.

  On the other hand, at the switching position B, the hydraulic oil discharged from the first hydraulic pump 12 is supplied to both the left and right traveling hydraulic motors 80 and 90, and the hydraulic oil discharged from the second hydraulic pump 32 is used for work actuators 82 and 84 used for work. , 86, 88, 92, 94, 96. That is, since the first hydraulic pump 12 is in charge of the traveling hydraulic motors 80, 90 and the second hydraulic pump 32 is in charge of the work actuators 82, 84, 86, 88, 92, 94, 96, the work actuators 82, 84, Independent running is possible without being affected by the load of 86, 88, 92, 94, 96.

  Further, the traveling straight valve 34 includes a pilot port 34a at one end of the spool and a pilot port 34b at the other end so that the energizing direction opposes. The pilot port 34a is supplied with a traveling straight travel signal Pst (hydraulic signal supplied during simultaneous operation) when the first merging switching valve 24 is at the switching position C, and the first merging switching valve 24 is at the switching position D. The pilot pressure Pa supplied to the specific actuator control valve 16 is sometimes supplied. The pilot pressure Pb supplied to the bucket control valve 38 is supplied to the pilot port 34b when the second merge switching valve 46 is in the switching position F. The switching position of the traveling straight valve 34 is determined by the magnitude relationship of the urging force determined by the pilot pressure supplied to the pilot ports 34a and 34b. In this embodiment, the straight travel signal Pst is a signal for detecting the switching state of the travel hydraulic motor control valves 14 and 36 and the work control valves 16, 18, 20, 22, 38, 40, 42. This is a hydraulic signal that is issued when the controller 72 determines that simultaneous operation is performed based on a signal for detecting the switching state, but is generated based on mechanical control without the determination of the controller 72. You may do it.

  When the straight travel valve 34 is in the switching position A, the hydraulic oil discharged from the second hydraulic pump 32 is supplied only to the second group of actuators 90, 92, 94, 96, and the first group of actuation actuators 82, 84, 86 is supplied. 88, but at the switching position B, the hydraulic oil from the second hydraulic pump 32 passes through the passage r (see FIG. 2) of the traveling straight valve, the oil passage 68, and the first parallel oil passage 58. Supplyed to a group of actuating actuators 82, 84, 86, 88.

  Further, the straight traveling valve 34 is continuously switched from the switching position A to the switching position B, and can take a switching position between the switching position A and the switching position B. As shown in FIG. The opening degree increases continuously as the switching amount from the switching position A to the switching position B increases. For this reason, as the switching amount from the switching position A to the switching position B increases, the amount of hydraulic oil (divided oil) supplied from the second hydraulic pump 32 to the first group of operating actuators 82, 84, 86, 88. (Amount) increases.

  The first merging switching valve 24 includes a solenoid portion 24a at one end of the spool and a spring 24b at the other end. A straight traveling signal Pst is input to the input port 24d, and a pilot pressure Pa supplied to the control valve 16 for the specific actuator is input to the input port 24e. When a command (electrical signal: described later) from the controller 72 is not input to the solenoid unit 24a, the solenoid 24a is switched to the switching position C by the urging force of the spring 24b, the input port 24d communicates with the pilot oil passage 34e, and the straight travel signal Pst is input to the pilot port 34a and urges the straight travel valve 34 to be switched to the switching position B. When a command (electrical signal) from the controller 72 is input to the solenoid unit 24a, the solenoid unit 24a urges the spool in the switching position D direction, and the first merging switching valve 24 is switched to the switching position D. When the first merging switching valve 24 is switched to the switching position D, the input port 24e communicates with the pilot oil passage 34e, and the pilot pressure Pa supplied to the specific actuator control valve 16 is input to the pilot port 34a. The straight travel valve 34 is urged in the direction of switching to the switching position B.

  The second merging switching valve 46 includes a solenoid portion 46a at one end of the spool and a spring 46b at the other end. The pilot pressure Pb supplied to the bucket control valve 38 is input to the input port 46d. When a command (electrical signal: to be described later) from the controller 72 is not input to the solenoid unit 46a, the solenoid 46a is switched to the switching position E by the biasing force of the spring 46b, the pilot port 34b communicates with the tank, and the pilot port 34b is piloted. No pressure is supplied. When a command (electrical signal) from the controller 72 is input to the solenoid unit 46a, the solenoid unit 46a biases the spool in the switching position F direction, and the second merging switching valve 46 is switched to the switching position F. When the second merging switching valve 46 is switched to the switching position F, the input port 46d communicates with the pilot oil passage 34f, and the pilot pressure Pb supplied to the bucket control valve 38 is input to the pilot port 34b and travels. The straight valve 34 is biased in the direction of switching to the switching position A.

  The cut valve 44 is provided on the most downstream side of the second center oil passage 60 and includes two switching positions G and H. At the switching position G, the second center oil passage 60 is communicated, and at the switching position H, the second center oil passage 60 is shut off.

  The cut valve 44 includes a solenoid portion 44a at one end of the spool and a spring 44b at the other end. The solenoid 44a urges the spool in the switching position H direction when a command (electrical signal) from the controller 72 is input. The spring 44b biases the spool in the switching position G direction. Therefore, when the command (electrical signal) from the controller 72 is not input to the solenoid portion 44a, the switching position of the cut valve 44 is the switching position G, the second center oil passage 60 communicates, and the controller 72 When the command (electrical signal) from is input to the solenoid portion 44a, the switching position of the cut valve 44 is the switching position H, and the second center oil passage 60 is shut off. When the switching position of the cut valve 44 is changed to the switching position H and the second center oil passage 60 is shut off, the hydraulic oil flowing through the second center oil passage 60 to the front of the cut valve 44 passes through the bypass oil passage 64. Then, it flows into the point 56 a on the inflow side of the control valve 16 for the specific actuator in the first center oil passage 56 of the first hydraulic pump 12.

  The pressure sensor 48 has a role of measuring the pilot pressure supplied to the left traveling hydraulic motor control valve 14 via the operation lever device 14A. The pressure data measured by the pressure sensor 48 is sent to the controller 72 via the electric signal line 48a.

  The pressure sensor 50 has a role of measuring a pilot pressure supplied to the specific actuator control valve 16 via the operation lever device 16A. The pressure data measured by the pressure sensor 50 is sent to the controller 72 via the electric signal line 50a.

  The pressure sensor 52 has a role of measuring the pilot pressure supplied to the control valve 36 for the right traveling hydraulic motor via the operation lever device 36A. The pressure data measured by the pressure sensor 52 is sent to the controller 72 via the electric signal line 52a.

  The controller 72 determines whether or not a traveling operation is performed based on the pressure data sent from the pressure sensors 48 and 52. Specifically, for example, the pilot pressure supplied to the traveling hydraulic motor control valves 14 and 36 is calculated based on the pressure data sent from the pressure sensors 48 and 52, respectively. If it is below the predetermined value, it is determined that the switching positions of the traveling hydraulic motor control valves 14 and 36 are both in the neutral position, and it is determined that the traveling operation is not performed.

  Further, the controller 72 determines whether or not the specific actuator 82 is operated based on the pressure data sent from the pressure sensor 50.

  When it is determined that the traveling operation is not performed and the specific actuator 82 is operated, the controller 72 controls the first merging switching valve 24 and the second merging switching valve 46 via the electric signal lines 24c and 46c. A command (electrical signal) is sent to simultaneously switch to switching position D and switching position F, respectively. As a result, the pilot pressure Pa supplied to the specific actuator control valve 16 is input to the pilot port 34a of the straight travel valve 34, and the pilot pressure Pb supplied to the bucket control valve 38 is input to the pilot port 34b. The

  The switching position of the traveling straight valve 34 is determined by the magnitude relationship of the urging forces determined by the pilot pressures Pa and Pb input to the pilot ports 34a and 34b. As described above, the switching position of the straight travel valve 34 is continuously switched from the switching position A to the switching position B, and as the switching amount to the switching position B increases, the second hydraulic pump 32 switches to the first group. The amount of hydraulic oil (split flow rate) supplied to the actuation actuators 82, 84, 86, 88 increases.

  When the hydraulic oil from the second hydraulic pump 32 is diverted to the specific actuator 82, a command (electric signal) is sent to the solenoid 44a of the cut valve 44 via the electric signal line 44c, and the cut valve 44 is switched to the switching position. H is switched to H, the second center oil passage 60 is shut off, and the hydraulic oil flowing through the second center oil passage 60 passes through the bypass oil passage 64 to the inflow point 56a of the first center oil passage 56 of the first hydraulic pump 12. Let it flow into.

  The controller 72, the first merging switching valve 24, and the second merging switching valve 46 supply pilot pressures Pa and Pb to the two pilot ports 34 a and 34 b of the traveling straight valve 34 so that the switching position of the traveling straight valve 34 is changed. Therefore, it can be said that the straight travel valve adjusting means.

  Next, the operation and action of the hydraulic circuit 10 according to the present embodiment will be described.

  FIG. 2 is an opening diagram schematically showing the relationship between the switching amount of the traveling straight valve 34 in the switching position B direction and the opening degrees of the four passages p, q, r, and s of the traveling straight valve 34. .

  The passage p is a passage that communicates the second center oil passage 60 and guides the hydraulic oil from the second hydraulic pump 32 to the downstream side of the second center oil passage 60. The passage q is a passage that connects the oil passage 66 and the oil passage 68 to guide the hydraulic oil from the first hydraulic pump 12 to the first parallel oil passage 58 of the first hydraulic pump 12. The passage r is a passage that connects the inflow port 34 c from the second hydraulic pump 32 and the oil passage 68 to guide the hydraulic oil from the second hydraulic pump 32 to the first parallel oil passage 58 of the first hydraulic pump 12. . The passage s is a passage that communicates the inflow port 34 d from the first hydraulic pump 12 and the second center oil passage 60 and guides hydraulic oil from the first hydraulic pump 12 to the second center oil passage 60.

  Here, it is assumed that the specific actuator control valve 16 is fully switched and the bucket control valve 38 is half-switched by the combined operation of the specific actuator 82 and the bucket cylinder 92 when the traveling operation is not performed.

  The specific actuator control valve 16 is fully switched, and the pilot pressure Pa supplied to the specific actuator control valve 16 is large. On the other hand, the bucket control valve 38 is half-lever switching, and the pilot pressure Pb supplied to the bucket control valve 38 is not so large.

  For this reason, the travel straight travel valve 34 switches to the switching position B side to some extent (the switching amount to the switching position B at this time is X), and the situation of the combined operation of the specific actuator 82 and the bucket cylinder 92 is brought about. Accordingly, the hydraulic oil from the second hydraulic pump 32 is diverted to the specific actuator 82.

  When the hydraulic oil from the second hydraulic pump 32 is diverted to the specific actuator 82, the controller 72 sends a command (electric signal) to the solenoid 44a of the cut valve 44 via the electric signal line 44c as described above. The feed and cut valve 44 is switched to the switching position H to shut off the second center oil passage 60. Therefore, in this assumption example, the cut valve 44 switches to the switching position H and blocks the second center oil passage 60.

  At this time, the state of diversion from the first and second hydraulic pumps 12 and 32 is as follows.

  The oil discharged from the first hydraulic pump 12 travels to the specific actuator 82 through the passage q. However, when the switching amount is X, the opening degree of the passage q is small (compared to the conventional case in which no branching operation is performed). On the other hand, the opening degree of the passage s increases, and the discharged oil from the first hydraulic pump 12 also flows into the second center oil passage 60. As described above, in this assumption example, the cut valve 44 is switched to the switching position H and shuts off the second center oil passage 60. Therefore, the first valve flows from the first hydraulic pump 12 into the second center oil passage 60 through the passage s. Discharged oil from the hydraulic pump 12 flows through the bypass oil passage 64 into the point 56a on the inflow side of the specific actuator control valve 16 in the first center oil passage 56 of the first hydraulic pump 12. Accordingly, the entire amount of oil discharged from the first hydraulic pump 12 is used for the operation of the specific actuator 82.

  On the other hand, the passage p for guiding the hydraulic oil from the second hydraulic pump 32 to the downstream side of the second center oil passage 60 is closed to some extent, but the discharge oil from the second hydraulic pump 32 is discharged from the traveling straight valve 34. Since it also flows into the second parallel oil passage 62 having an opening that does not depend on the switching position, each actuator (the right traveling hydraulic motor 90, the bucket cylinder 92, the first boom cylinder 94, the second arm cylinder 96) of the second group. A certain amount of hydraulic fluid is supplied. On the other hand, since the passage r is opened, the amount of hydraulic fluid supplied from the second hydraulic pump 32 to each actuator of the second group decreases, and as a result, the amount of hydraulic fluid distributed to the specific actuator 82 increases. For this reason, the specific actuator 82 becomes easier to move faster even in the combined operation with the bucket cylinder 92, and the combined operability is improved.

  Although the embodiment of the present invention has been described above, in the present invention, when the traveling operation is not performed, the hydraulic oil from the second hydraulic pump is supplied to the first group of specific actuators using the traveling straight valve. Therefore, the composite operability can be improved without adding a configuration. Further, in the present invention, the partial flow rate from the second hydraulic pump is adjusted using the traveling straight valve, but if the condition that the traveling operation is not performed is not satisfied, the partial flow rate is adjusted using the traveling straight valve. There is no adverse effect on straight running performance.

  In this embodiment, two merging switching valves (the first merging switching valve 24 and the second merging switching valve 46) are provided. However, the first merging switching valve 24 and the second merging switching valve 46 are provided as one switching valve. It may be integrated into.

  In this embodiment, the pilot pressure Pb supplied to the bucket control valve 38 is input to the input port 46d of the second merging switching valve 46. However, the control for the other work actuators of the second group is performed. The pilot pressures of the valves (the first boom control valve 40 and the second arm control valve 42) may be input to the input port 46d of the second merging switching valve 46, in which case the bucket cylinder 92, The combined operability with the first boom cylinder 94 or the second arm cylinder 96 is improved.

  Further, a pressure sensor for measuring the pilot pressure Pb supplied to the bucket control valve 38 is further provided, and the pressure data measured by the pressure sensor is input to the controller 72. The operating conditions are grasped by the pilot pressures Pa and Pb, the amounts of hydraulic oil to be supplied to the specific actuator 82 and the bucket cylinder 92 are calculated according to the operating conditions, and based on the calculation results, 2 of the straight traveling valve 34 is calculated. The controller 72 directly adjusts the pilot pressure supplied to the two pilot ports 34a, 34b by an electromagnetic proportional valve, etc., adjusts the switching position of the traveling straight-advancing valve 34, and distributes the pilot pressure from the second hydraulic pump 32 to the specific actuator 82. The flow rate may be controlled.

  Further, the operation status of the specific actuator 82 and the bucket cylinder 92 is not the pilot pressures Pa and Pb, but the switching amount from the neutral position of the specific actuator control valve 16 and the bucket control valve 38 and the operation of the operation lever devices 16A and 38A. You may grasp | ascertain based on the amount of operation of a lever. Further, it may be directly grasped from the operation amounts of the specific actuator 82 and the bucket cylinder 92.

  In addition, a changeover switch for enabling or disabling the diversion / merging function in the present embodiment may be provided, and the operator may select to enable or disable this function according to preference.

  For example, the present invention can be applied to a hydraulic circuit of a construction machine of a two-pump system in which discharge oils of two hydraulic pumps are merged as necessary and supplied to a hydraulic actuator that requires a large flow rate.

DESCRIPTION OF SYMBOLS 10 ... Hydraulic circuit 12 ... 1st hydraulic pump 14 ... Left travel hydraulic motor control valve (1st travel control valve)
16 ... Control valve for specific actuator (first work control valve)
24 ... 1st confluence switching valve 32 ... 2nd hydraulic pump 34 ... Traveling straight travel valve 36 ... Control valve for right travel hydraulic motor (2nd travel control valve)
38 ... Bucket control valve (second work control valve)
44 ... Cut valve 46 ... Second merge switching valve 48, 50, 52 ... Pressure sensor 56 ... First center oil passage 58 ... First parallel oil passage 60 ... Second center oil passage 62 ... Second parallel oil passage 64 ... Bypass Oil path 72 ... Controller 80 ... Left travel hydraulic motor 82 ... Specific actuator 90 ... Right travel hydraulic motor 92 ... Bucket cylinder Pst ... Travel straight signal Pa, Pb ... Pilot pressure

Claims (4)

A first hydraulic pump and a second hydraulic pump are provided, a first travel control valve for one travel hydraulic motor is disposed in a first center oil passage of the first hydraulic pump, and the first travel control valve A first work control valve for the work actuator is disposed downstream of the first center oil passage, and a traveling straight valve is disposed in the second center oil passage of the second hydraulic pump, and the second center of the traveling straight valve is disposed. A second travel control valve for the other travel hydraulic motor is disposed downstream of the oil passage, and a second work control valve for another work actuator is disposed downstream of the second center oil passage of the second travel control valve. In the hydraulic circuit of construction machinery,
A travel rectilinear valve adjusting means for adjusting the switching position of the travel rectilinear valve is provided;
When the travel operation is not performed and the work actuator is operated by the first work control valve, the switching position of the travel straight valve is adjusted, and the second hydraulic pressure is applied to the first work control valve. A hydraulic circuit for a construction machine, wherein hydraulic fluid is supplied from a pump. In claim 1, further comprising:
A cut valve that is provided downstream of the second work control valve of the second center oil passage and switches between communication and shutoff;
A point of the second center oil passage between the cut valve and the second work control valve is defined as a first center oil passage between the first travel control valve of the first center oil passage and the first work control valve. A bypass oil passage connected to the point of
A hydraulic circuit for a construction machine, characterized by comprising In claim 1 or 2,
A hydraulic circuit for a construction machine, wherein a switching position of the straight travel valve is adjusted based on a pilot pressure supplied to the first work control valve and a pilot pressure supplied to the second work control valve. In any one of Claims 1-3,
A hydraulic circuit for a construction machine, wherein the switching position of the straight travel valve is adjusted based on a switching amount from the neutral position of the first work control valve and a switching amount from the neutral position of the second work control valve. .

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