JP2018028357A - Hydraulic system for construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic system that has an open-center type directional control valve and that can reduce load on an engine while maintaining good operability of bleeding-off function.SOLUTION: A hydraulic system for a construction machine according to the present invention comprises: center bypass cut valves 120, 121 which are arranged at the furthest downstream side of an SW valve 21, a BM2 valve 26 arranged in center bypass passages 9, 10, and can block the center bypass passages 9, 10; and a pump flow rate control unit 70 which is arranged on a vehicle body control device 60, and outputs a signal for operating the center bypass cut valves 120, 121 in response to switching of the SW valve 21, the BM2 valve 26 or the like, and outputs a signal for setting target flow rates of fluid pumps 2, 3 to flow rates equal to original supply flow rates of the fluid pumps 2, 3 minus a bleed-off flow rate by calculation when the center bypass passages 9, 10 are closed by the center base part cut valves 120, 121.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a hydraulic system for a construction machine such as a hydraulic excavator provided with an open center type directional control valve.

  Patent Document 1 discloses a hydraulic system for a construction machine such as a hydraulic excavator provided with an open center type directional control valve. In a hydraulic system having an open center type directional control valve and a center bypass passage in which the directional control valve is disposed as disclosed in Patent Document 1, a bleed-off flow rate is usually generated. Energy corresponding to the flow rate is required.

JP 2001-84210 A

  A hydraulic system equipped with an open center type directional control valve as shown in Patent Document 1 employs a bleed-off function in order to reduce vibration and shock at the start of operation of the actuator and to smooth the operation. Yes. The bleed-off function is to discharge a part of the working fluid supplied from the fluid pump to the actuator to the tank via the bleed-off circuit. The working fluid that is discarded from the bleed-off circuit to the tank is not used for the work of the actuator, and causes an increase in engine load. As a result, conventionally, the fuel consumption tends to increase.

  In order to solve the above problems, an object of the present invention is a hydraulic system including an open center type directional control valve, which reduces engine load while maintaining good operability of a bleed-off function. The object is to provide a hydraulic system for construction machinery.

  In order to solve the above-described problems, a hydraulic system for a construction machine according to the present invention is a variable displacement fluid pump driven by an engine and capable of adjusting a supply flow rate by an operation signal from a vehicle body control device, and the fluid pump. Hydraulics of a construction machine comprising: an actuator that is operated by a working fluid supplied from a fluid; and a directional control valve that is provided in a center bypass passage connected to the fluid pump and controls the flow rate and direction of the working fluid supplied to the actuator In the system, a center bypass cut valve provided at the most downstream side of the direction control valve provided in the center bypass passage and capable of blocking the center bypass passage, and provided in the vehicle body control device, the direction control valve A signal for operating the center bypass cut valve is output along with switching of the A pump flow rate control unit configured to calculate a target supply flow rate of the fluid pump by subtracting a bleed-off flow rate from an original supply flow rate of the fluid pump by calculation when the center bypass passage is closed by a bypass cut valve; It is characterized by that.

  A hydraulic system for a construction machine according to the present invention is a hydraulic system including an open center type directional control valve, and can reduce engine load while maintaining good operability of a bleed-off function. . Thereby, this invention can reduce the fuel consumption of an engine compared with the past, and can improve fuel consumption efficiency.

1 is a side view showing a hydraulic excavator cited as an example of a construction machine provided with a first embodiment of a hydraulic system according to the present invention. 1 is a circuit diagram illustrating a hydraulic drive device provided in a hydraulic system according to a first embodiment. FIG. It is a figure which shows the control system with which the hydraulic system which concerns on 1st Embodiment was equipped. It is a figure which shows the pump flow control part with which the control system shown in FIG. 3 was equipped. It is a figure which shows the bleed-off flow volume calculation system with which the pump flow volume control part shown in FIG. 4 was equipped. It is a figure which shows another bleed-off flow volume calculation system with which the pump flow volume control part shown in FIG. 4 was equipped. It is a figure which shows the calculation formula of a well-known bleed-off opening area, and the calculation formula of a pump discharge flow rate. It is the flowchart which showed a part of calculation processing procedure in 1st Embodiment. It is a flowchart following the flowchart shown in FIG. 10 is a flowchart following the flowchart shown in FIG. 9. FIG. 5 is a hydraulic circuit diagram showing a hydraulic drive device provided in a second embodiment of the hydraulic system according to the present invention. It is a hydraulic circuit diagram which shows the hydraulic drive unit with which 3rd Embodiment of the hydraulic system which concerns on this invention was equipped.

  Embodiments of a hydraulic system for construction machines according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a side view showing a hydraulic excavator cited as an example of a construction machine provided with a first embodiment of a hydraulic system according to the present invention.

  The hydraulic excavator shown in FIG. 1 includes a traveling body 100, a turning body 101, and a front work machine 102. A left traveling motor 111 and a right traveling motor 112 are disposed on the traveling body 100, and the crawler 106 is rotationally driven by these traveling motors 111 and 112 to travel forward or backward. A turning motor 110 is mounted on the turning body 101, and the turning body 101 turns the turning body 101 rightward or leftward with respect to the traveling body 100. The front work machine 102 includes a boom 103, an arm 104, and a bucket 105. The boom 103 is moved up and down by the boom cylinder 107, the arm 104 is moved up and down by the arm cylinder 108 to the dump side (opening side) or the cloud side (scraping side), and the bucket 105 is moved to the dump side or cloud side by the bucket cylinder 109. Move up and down.

  FIG. 2 is a circuit diagram showing a hydraulic drive device provided in the hydraulic system according to the first embodiment.

  As shown in FIG. 2, the hydraulic system according to the first embodiment is a parallel type, and includes an engine 1, a variable displacement fluid pump (P1) 2 driven by the engine 1, and a variable displacement fluid. A pump (P2) 3, a pilot pump 4, a P1 regulator 5 for determining the capacity of the fluid pump (P1) 2 by a P1 control pressure (hereinafter referred to as Pc1) and a torque control pressure (hereinafter referred to as Tc). , A P2 regulator 6 for determining the capacity of the fluid pump (P2) 3 by a P2 control pressure (hereinafter referred to as Pc2) and a torque control pressure (hereinafter referred to as Tc), and a circuit connected to the fluid pump (P1) 2. A P1 relief valve 7 for determining an upper limit pressure and a P2 relief valve 8 for determining an upper limit pressure of a circuit connected to the fluid pump (P2) 3 are provided.

  A P1 center bypass passage 9 connected to the fluid pump (P1) 2, a P1 center bypass cut valve 120 including a hydraulic valve capable of shutting off the P1 center bypass passage 9, and a P2 center bypass connected to the fluid pump (P2) 3. A passage 10 and a P2 center bypass cut valve 121 composed of a hydraulic valve capable of blocking the P2 center bypass passage 10 are provided.

  Further, the boom cylinder 107 and the arm cylinder 108 driven by the working fluid supplied from the fluid pump (P1) 2 and the fluid pump (P2) 3 and the working fluid supplied from the fluid pump (P1) 2 are driven. The aforementioned turning motor 110 and the left traveling motor 111, and the aforementioned bucket cylinder 109 and the right traveling motor 112 driven by the working fluid supplied from the fluid pump (P2) 3 are provided.

  Further, the P1 center bypass passage 9 connected to the fluid pump (P1) 2 is provided to control the flow rate and direction of the working fluid supplied from the fluid pump (P1) 2 to the turning motor 110. Direction control valve or SW valve 21, directional control valve or AM2 valve 22 for controlling the flow rate and direction of the working fluid supplied to the arm cylinder 108, and directional control for controlling the flow rate and direction of the working fluid supplied to the boom cylinder 107 A valve or BM1 valve 23 and a direction control valve or TRL valve 24 for controlling the flow rate and direction of the working fluid supplied to the left traveling motor 111 are provided.

  Further, of the working fluids provided in the P2 center bypass passage 10 connected to the fluid pump (P2) 3 and supplied from the fluid pump (P2) 3, the flow rate and direction of the working fluid supplied to the arm cylinder 108 are controlled. A control valve or AM1 valve 25, a direction control valve or BM2 valve 26 for controlling the flow rate and direction of the working fluid supplied to the boom cylinder 107, and a BK valve 27 for controlling the flow rate and direction of the working fluid supplied to the bucket cylinder 109. And a directional control valve or TRR valve 28 for controlling the flow rate and direction of the working fluid supplied to the right traveling motor 112.

  Further, the working fluid is supplied from the pilot pump 4 and the working fluid having a pressure corresponding to the operation amount in each operation direction is supplied to the BM1 valve 23, the BM2 valve 26, and the BK valve 27 to operate each valve, and the boom cylinder 107 and the bucket are operated. An operation command device 41 for operating the cylinder 109, and a working fluid having a pressure corresponding to the operation amount in each operation direction is supplied to the AM2 valve 22, the AM1 valve 25, and the SW valve 21 to operate each valve to operate the arm cylinder 108 and the swing motor. An operation command device 42 for operating 110, an operation command device 43 for operating the left traveling motor 111 by operating the TRL valve 24 by supplying a working fluid having a pressure corresponding to the operation amount in each operation direction to the TRL valve 24, and And an operation command device 44 that operates the TRR valve 28 by operating the TRR valve 28 by supplying a working fluid having a pressure corresponding to the operation amount in each operation direction to the TRR valve 28.

  The pressure sensor 130 measures the pressure of the working fluid supplied from the fluid pump (P1) 2 (hereinafter referred to as P1 pressure), and the pressure of the working fluid supplied from the fluid pump (P2) 3 (hereinafter referred to as P2). Pressure sensor 131 that measures the pressure of the working fluid in the P1 center bypass passage 9 (hereinafter referred to as T pressure) provided downstream of the P1 center bypass cut valve 120, A pressure sensor 133 that measures the BMu (boom raising) operation of the command device 41, a pressure sensor 134 that measures the BMd (boom lowering) operation pressure of the operation command device 41, and a BKc (bucket cloud) operating pressure of the operation command device 41 A pressure sensor 135 for measuring the pressure, a pressure sensor 136 for measuring the BKd (bucket dump) operating pressure of the operation command device 41, and an AMc (arm cloud) operating pressure of the operation command device 42. A pressure sensor 137 for measuring, a pressure sensor 138 for measuring an AMd (arm dump) operating pressure of the operation command device 42, a pressure sensor 139 for measuring a SWL (turn left) operating pressure of the operation command device 42, and an operation command device 42, a pressure sensor 140 that measures the SWR (turning right) operating pressure, a pressure sensor 141 that measures the TRLF (traveling leftward advance) operating pressure of the operation command device 43, and a TRLR (traveling leftward) operation of the operation command device 43. A pressure sensor 142 that measures the pressure, a pressure sensor 143 that measures the TRRF (traveling rightward forward) operation pressure of the operation command device 44, and a pressure sensor 144 that measures the TRRR (traveling rightward reverse) operation pressure of the operation command device 44 It has.

  Here, the valves 21 to 28 constituting the direction control valve are valves that return to the neutral position by the force of the built-in spring when the working fluid is not supplied from the operation command devices 41 to 44. The P1 center bypass cut valve 120 and the P2 center bypass cut valve 121 are normally open valves that maintain an open position by the force of a built-in spring when the control working fluid is not supplied.

  FIG. 3 is a diagram illustrating a control system provided in the hydraulic system according to the first embodiment.

  The control system provided in the first embodiment includes a vehicle body control device 60, an engine speed command device 53 that designates a rotation speed command (hereinafter referred to as NRO) of the engine 1, and an engine supplied from the vehicle body control device 60. An engine control device 65 that receives a target rotation speed (hereinafter referred to as NR) and controls the rotation speed of the engine 1 is provided. Inside the engine control device 65, an input unit 66 that receives an input signal, a storage unit 67 that stores information necessary for calculation in advance, a signal received by the input unit 66, and a storage unit 67 are stored in advance. A calculation control unit 68 for calculating a control amount necessary for controlling the engine rotation speed based on the information, and an output unit 69 for outputting the control amount calculated by the calculation control unit 68. In addition, an electronic governor 55 that adjusts the fuel injection amount of the engine 1 according to an operation signal input from the engine control device 65, and a rotation speed sensor 54 that measures the rotation speed (hereinafter referred to as NE) of the engine 1 are provided. I have.

  Inside the vehicle body control device 60, an input unit 61 that receives an input signal, a storage unit 62 that stores information necessary for calculation in advance, a signal received by the input unit 61, and a storage unit 62 are stored in advance. A calculation control unit 63 that calculates a control amount necessary for controlling the vehicle body based on the information, and an output unit 64 that outputs the control amount calculated by the calculation control unit 63.

  Further, in the vehicle body control device 60, the flow rate of the fluid pump (P1) 2 is calculated from the values of the pressure sensors 130 to 144 supplied from the arithmetic control unit 63 and the NE value, which is a characteristic function of the present invention. (Hereinafter referred to as Q1) and a pump flow rate controller 70 for calculating the flow rate of the fluid pump (P2) 3 (hereinafter referred to as Q2).

  Further, an electromagnetic valve that supplies a pressure for controlling the opening and closing of the P1 center bypass cut valve 120 in response to an operation signal input from the vehicle body control device 60 upon receiving a supply of working fluid from the pilot pump 4, that is, a P1 center bypass cut control valve. 122 and an electromagnetic valve that supplies pressure for controlling the opening and closing of the P2 center bypass cut valve 121 in response to an operation signal received from the vehicle body control device 60 upon receiving a working fluid from the pilot pump 4, that is, a P2 center bypass cut control. A valve 123, an electromagnetic valve that receives a supply of working fluid from the pilot pump 4 and supplies Pc1 pressure in response to an operation signal input from the vehicle body control device 60, that is, a P1 control pressure control valve 124, and a working fluid from the pilot pump 4 Valve that supplies Pc2 pressure in response to an operation signal input from the vehicle body control device 60 in response to the supply of That is, a P2 control pressure control valve 125 and a torque control pressure control valve 126 that receives a supply of working fluid from the pilot pump 4 and supplies a Tc pressure according to an operation signal input from the vehicle body control device 60 are provided.

  The P1 center bypass cut control valve 122 and the P2 center bypass cut control valve 123 are two-position switching valves that move to a position where the downstream of the valve communicates with the tank by the force of a built-in spring when no operation signal is input. It is.

  FIG. 4 is a diagram illustrating a pump flow rate control unit provided in the control system illustrated in FIG. 3.

  As shown in FIG. 4, the pump flow rate control unit 70 determines whether the P1 center bypass cut valve 120 is opened or closed and calculates an operation signal (hereinafter referred to as SCBC1) of the P1 center bypass cut control valve 122. Valve control unit 71, P1 bleed-off flow rate calculation system 80 for calculating the bleed-off flow rate (hereinafter referred to as Qb1) of the fluid pump (P1) 2, and fluid pump supplied from the calculation control unit 63 of the vehicle body control device 60 (P1) A P1 flow rate selection unit 72 that selects either the original P1 flow rate of the working fluid from 2 (hereinafter referred to as Q1org) or a value obtained by subtracting Qb1 from Q1org according to SCBC1 and Q1; The capacity of the fluid pump (P1) 2 is determined from Q1 selected by the P1 flow rate selection unit 72 and NE supplied from the input unit 61 of the vehicle body control device 60, and an operation signal of the P1 control pressure control valve 124 (hereinafter referred to as SPc1). ) A P1 capacity command value calculation unit 73 for calculation is provided.

  Further, the pump flow rate control unit 70 determines the opening / closing of the P2 center bypass cut valve 121 and calculates an operation signal (hereinafter referred to as SCBC2) of the P2 center bypass cut control valve 123; A P2 bleed-off flow rate calculation system 90 that calculates a bleed-off flow rate (hereinafter referred to as Qb2) of the fluid pump (P2) 3 and a fluid pump (P2) 3 that is supplied from the calculation control unit 63 of the vehicle body control device 60 P2 flow rate selection unit 75 that selects either the original P2 flow rate of the working fluid (hereinafter referred to as Q2org) or the value obtained by subtracting Qb2 from Q2org according to SCBC2 and this P2 flow rate selection The volume of the fluid pump (P2) 3 is determined from Q2 selected by the unit 75 and NE supplied from the input unit 61 of the vehicle body control device 60, and an operation signal (hereinafter referred to as SPc2) of the P2 control pressure control valve 125 is calculated. And a P2 capacity command value calculation unit 76.

  That is, the pump flow rate control unit 70 switches each of the SW valve 21, AM2 valve 22, BM1 valve 23, TRL valve 24, AM1 valve 25, BM2 valve 26, BK valve 27, and TRR valve 28 that constitute the direction control valve. Accordingly, a signal for operating the P1 center bypass cut valve 120 and the P2 center bypass cut valve 121 is output, and the P1 center bypass passage 9 and the P2 center bypass are respectively output by the P1 center bypass cut valve 120 and the P2 center bypass cut valve 121. When each of the passages 10 is closed, the target supply flow rate of the fluid pump (P1) 2 and the fluid pump (P2) 3 is calculated to be a flow rate obtained by subtracting the bleed-off flow rate from the original supply flow rate of the fluid pump. A process of outputting a signal that virtually reproduces the off state is performed.

  FIG. 5 is a diagram showing a bleed-off flow rate calculation system provided in the pump flow rate control unit shown in FIG.

  The P1 bleed-off flow rate calculation system 80 shown in FIG. 5 is obtained by multiplying the BMu operation pressure measured by the pressure sensor 133 supplied from the calculation control unit 63 and the BMd operation pressure measured by the pressure sensor 134 by −1. BM1 bleed-off area calculation unit 81 that calculates AbBM1 based on the relationship between the bleed-off area (hereinafter referred to as AbBM1) of the BM1 valve 23 with respect to the BM operating pressure stored in advance in the storage unit 62 as the operation pressure, The AM operation pressure measured by the pressure sensor 137 supplied from the control unit 63 and the AM operation pressure measured by the pressure sensor 138 multiplied by −1 is set as the AM operation pressure, and the AM operation stored in the storage unit 62 in advance. The AM2 bleed-off area calculation unit 82 that calculates AbAM2 based on the relationship between the bleed-off area of the AM2 valve 22 with respect to pressure (hereinafter referred to as AbAM2) and the pressure sensor 139 supplied from the calculation control unit 63 The SW operation pressure obtained by multiplying the SWL operation pressure and the SWR operation pressure measured by the pressure sensor 140 by −1 is used as the SW operation pressure, and the SW operation pressure stored in advance in the storage unit 62 and the bleed-off area of the SW valve 21 (hereinafter, referred to as “SW operation pressure”). The SW bleed-off area calculation unit 83 for calculating AbSW based on the relationship of AbSW), the TRLF operation pressure measured by the pressure sensor 141 supplied from the calculation control unit 63, and the TRLR operation pressure measured by the pressure sensor 142 A TRL bleed that calculates AbTRL based on the relationship between the TRL operating pressure stored in advance in the storage unit 62 and the bleed-off area of the TRL valve 24 (hereinafter referred to as AbTRL). An off-area calculating unit 84, a P1 equivalent bleed-off area calculating unit 85 for calculating an equivalent area of AbBM1, AbAM2, AbSW, and AbTRL (hereinafter referred to as Ab1), and a pressure sensor supplied from Ab1 and the calculation control unit 63 P1 measured by 130 And a P1 bleed-off flow rate calculation unit 86 for calculating the bleed-off flow rate (hereinafter referred to as Qb1) of the fluid pump (P1) 2 from the T pressure measured by the pressure sensor 130 supplied from the calculation control unit 63. .

  FIG. 6 is a diagram showing another bleed-off flow rate calculation system provided in the pump flow rate control system shown in FIG.

  The P2 bleed-off flow calculation system 90 shown in FIG. 6 is obtained by multiplying the BMu operation pressure measured by the pressure sensor 133 supplied from the calculation control unit 63 and the BMd operation pressure measured by the pressure sensor 134 by −1. BM2 bleed-off area calculating unit 91 for calculating AbBM2 based on the relationship of the bleed-off area (hereinafter referred to as AbBM2) of the BM2 valve 26 to the BM operating pressure stored in advance in the storage unit 62 as the operating pressure; The BK operating pressure stored in advance in the storage unit 62 is obtained by multiplying the BKc operating pressure measured by the pressure sensor 135 supplied from the control unit 63 and the BKd operating pressure measured by the pressure sensor 136 by −1. BK bleed-off area calculation unit 92 that calculates AbBK based on the relationship of the bleed-off area (hereinafter referred to as AbBK) of BK valve 27 with respect to the pressure, and pressure sensor 137 supplied from calculation control unit 63 measures The AM operating pressure and the AM operating pressure measured by the pressure sensor 138 multiplied by −1 are used as the AM operating pressure. The AM operating pressure stored in the storage unit 62 in advance and the bleed-off area of the AM1 valve 25 (hereinafter referred to as AbAM1) The AM1 bleed-off area calculation unit 93 that calculates AbAM1 based on the relationship of the above-mentioned relationship), the TRRF operation pressure measured by the pressure sensor 143 supplied from the calculation control unit 63, and the TRRR operation pressure measured by the pressure sensor 144 TRR bleed-off that calculates AbTRR based on the relationship between the TRR operating pressure stored in advance in the storage unit 62 and the bleed-off area of the TRR valve 28 (hereinafter referred to as AbTRR). An area calculation unit 94, a P2 equivalent bleed-off area calculation unit 95 for calculating an equivalent area of AbBM2, AbBK, AbAM1, and AbTRR (hereinafter referred to as Ab2), and a pressure sensor 131 supplied from Ab2 and the calculation control unit 63 P2 pressure measured by And a P2 bleed-off flow rate calculation unit 96 that calculates the bleed-off flow rate (hereinafter referred to as Qb2) of the fluid pump (P2) 3 from the T pressure measured by the pressure sensor 132 supplied from the calculation control unit 63. .

  FIG. 7 is a diagram showing a known formula for calculating the bleed-off opening area and a formula for calculating the pump discharge flow rate.

  In FIG. 7, Expression (1) represents an arithmetic expression of the P1 equivalent bleed-off area arithmetic unit 85. Formula (2) shows the calculation formula of the P1 bleed-off flow rate calculation unit 86. Formula (3) shows a calculation formula of the P2 equivalent bleed-off area calculation unit 95. Formula (4) shows the calculation formula of the P2 bleed-off flow rate calculation unit 96. In Equations (2) and (4), α1 is a coefficient that is arbitrarily set in advance for Qb1 adjustment, C is a flow coefficient generally accepted in the fluid dynamics world, and ρ is a density based on the physical properties of the working fluid. , Α2 is a coefficient that is arbitrarily set in advance for Qb2 adjustment. α1, C, ρ, and α2 are numerical values stored in the storage unit 62 in advance. Expressions (1) to (4) are expressions generally used in the fluid dynamics world.

  FIG. 8 is a flowchart showing a part of the arithmetic processing procedure in the first embodiment, FIG. 9 is a flowchart following the flowchart shown in FIG. 8, and FIG. 10 is a flowchart following the flowchart shown in FIG. Next, based on these FIGS. 8 to 10, the arithmetic processing directly related to the first embodiment will be described.

[Step 200] The input unit 61 of the vehicle body control device 60 acquires the pressures and NEs of the pressure sensors 130 to 144. Next, the process proceeds to step S210.

[Step S210] The calculation control unit 63 calculates Q1org and Q2org from the operation amount of the operation command devices 41 to 44, P1 pressure, P2 pressure, NE, and information stored in the storage unit 62 in advance. Next, the process proceeds to step S220.

[Step S220] As shown in FIG. 5, the P1 bleed-off flow rate calculation system 80 calculates AbBM1, AbAM2, AbSW, and AbTRL. Next, the process proceeds to step S230.

[Step S230] The P1 equivalent bleed-off area calculation unit 85 calculates Ab1 using the equation (1) in FIG. Next, the process proceeds to step S240.

[Step S240] The P1 bleed-off flow rate calculation unit 86 calculates Qb1 using equation (2) in FIG. Next, the process proceeds to step S250.

[Step S250] As shown in FIG. 6, the P2 bleed-off flow rate calculation system 90 calculates AbBM2, AbAM1, AbBK, and AbTRR. Next, the process proceeds to step S260.

[Step S260] The P2 equivalent bleed-off area calculation unit 95 calculates Ab2 using equation (3) in FIG. Next, the process proceeds to step S270.

[Step S270] The P2 bleed-off flow rate calculation unit 96 calculates Qb2 using equation (4) in FIG. Next, the process proceeds to step S280.

[Step S280] As shown in FIG. 4, the P1 center bypass cut valve control unit 71 selects the maximum value among BMu pressure, BMd pressure, AMc pressure, AMd pressure, SWL pressure, SWR pressure, TRLF pressure, and TRLR pressure. To do. Next, the process proceeds to step S290.

[Step S290] The pump flow rate controller 70 determines whether or not the maximum value selected in Step S280 is equal to or greater than a predetermined threshold value. When it is determined that the maximum value selected in step S280 is equal to or greater than the threshold value, the process proceeds to step S300.

[Step S300] The P1 center bypass cut valve control unit 71 sets SCBC1 to 5. Next, the process proceeds to step S320.

  On the other hand, when it is determined in step S290 that the maximum value selected in step S280 is less than the threshold value, the process proceeds to step S310.

[Step S310] The P1 center bypass cut valve control unit 71 sets SCBC1 to 0, and then proceeds to step S320.

[Step S320] As shown in FIG. 4, the P2 center bypass cut valve control unit 74 selects the maximum value among the BMu pressure, BMd pressure, AMc pressure, BKc pressure, BKd pressure, TRRF pressure, and TRRR pressure. Next, the process proceeds to step S330.

[Step S330] The pump flow rate controller 70 determines whether or not the maximum value selected in Step S320 is equal to or greater than a predetermined threshold value. When it is determined that the maximum value selected in step S320 is greater than or equal to the threshold value, the process proceeds to step S340.

[Step S340] The P2 center bypass cut valve control unit 74 sets SCBC2 to 5. Next, the process proceeds to step S360.

  On the other hand, when it is determined in step S330 that the maximum value selected in step S320 is less than the threshold value, the process proceeds to step S350.

[Step S350] The P2 center bypass cut valve control unit 74 sets SCBC2 to zero. Next, the process proceeds to step S360.

[Step S360] The pump flow rate controller 70 determines whether SCBC1 is equal to or greater than a predetermined threshold value. When it is determined that SCRC1 is equal to or greater than the threshold value, the process proceeds to step S370.

[Step S370] The P1 flow rate selection unit 72 selects a value obtained by subtracting Qb1 from Q1org as Q1.

  On the other hand, when it is determined in step S360 that SCBC1 is less than the threshold value, the process proceeds to step S380.

[Step S380] The P1 flow rate selection unit 72 sets Q1org to Q1. Next, the process proceeds to step S390.

[Step S390] The pump flow rate controller 70 determines whether SCBC2 is equal to or greater than a predetermined threshold value. When it is determined that SCBC2 is equal to or greater than the threshold value, the process proceeds to step S400.

[Step S400] A value obtained by subtracting Qb2 from Q2org is selected as Q2. Next, the process proceeds to step S420.

  On the other hand, in step S390, the P2 flow rate selection unit 75 sets Q2org to Q2. Next, the process proceeds to step S420.

[Step S420] The P1 capacity command value calculation unit 73 calculates SPc1 from the map of SPc1 with respect to Q1 and Q1 stored in advance in the storage unit 62. Next, the process proceeds to step S430.

[Step S430] The P2 capacity command value calculation unit 76 calculates SPc2 from the map of SPc2 with respect to Q2 and Q2 stored in advance in the storage unit 62. Next, the process proceeds to step S440.

[Step S440] The output unit 64 outputs SCBC1 to the P1 center bypass cut control valve 122, SCBC2 to the P2 center bypass cut control valve 123, SPc1 to the P1 control pressure control valve 124, and SPc2 to the P2 control pressure control valve 125, respectively. Output.

  By performing the above control process, the hydraulic system according to the first embodiment is operated by the operation command devices 41 to 44, and when the operation amount is equal to or greater than a predetermined threshold, the operation command devices 41 to 41 are operated. The P1 center bypass cut valve 120 and / or the P2 center bypass cut valve 121 corresponding to each operation of 44 are closed and the working fluid supplied from each of the fluid pump (P1) 2 and / or the fluid pump (P2) 3 Is controlled to a flow rate obtained by subtracting the bleed-off flow rate from the original flow rate. As a result, the power of the engine 1 that drives the fluid pump (P1) 2 and / or the fluid pump (P2) 3 is reduced. That is, according to the first embodiment, the load on the engine 1 can be reduced while maintaining the good operability of the bleed-off function, the fuel consumption of the engine 1 can be reduced, and the fuel efficiency can be improved. Can do.

  Further, when the electric system fails and an operation signal is not supplied to the P1 center bypass cut control valve 122 and / or the P2 center bypass cut control valve 123 which are normally open valves, the P1 center bypass cut valve 120 and Since tank pressure is supplied to the P2 center bypass cut valve 121 and the P1 center bypass cut valve 120 and / or the P2 center bypass cut valve 121 are kept in the open position, the same operation as that of the conventional hydraulic system can be performed. it can.

  FIG. 11 is a hydraulic circuit diagram showing a hydraulic drive apparatus provided in the second embodiment of the hydraulic system according to the present invention.

  The hydraulic system according to the second embodiment including the hydraulic drive device shown in FIG. 11 is also provided in a hydraulic excavator similar to that shown in FIG. 1, for example, and is connected to the fluid pump (P1) 2. Supply of the working fluid to the valve 21, the AM2 valve 22, the BM1 valve 23, the TRL valve 24, the AM1 valve 25, the BM2 valve 26, the BK valve 27, and the TRR valve 28 connected to the fluid pump (P2) 3 are all P1 center. This is a tandem hydraulic system that is performed through the bypass passage 9 and the P2 center bypass passage 10. Other configurations are the same as those of the first embodiment described above. Even in the second embodiment configured as described above in the tandem hydraulic system, the bleed-off flow rate is the same as that in the first embodiment, so that the same effects as those in the first embodiment can be obtained.

  FIG. 12 is a hydraulic circuit diagram showing a hydraulic drive apparatus provided in the third embodiment of the hydraulic system according to the present invention.

  The hydraulic system according to the third embodiment having the hydraulic drive device shown in FIG. 12 is also provided in a hydraulic excavator similar to that shown in FIG. 1, for example, and is connected to the fluid pump (P1) 2. Supply of the working fluid to the valve 21, the AM2 valve 22, the BM1 valve 23, the TRL valve 24, the AM1 valve 25, the BM2 valve 26, the BK valve 27, and the TRR valve 28 connected to the fluid pump (P2) 3 are all P1 center. This is a tandem / parallel hydraulic system that is performed through the bypass passage 9 and the P2 center bypass passage 10. Other configurations are the same as those of the first embodiment described above. Also in the third embodiment configured as described above in the tandem hydraulic system, the bleed-off flow rate is the same as that in the first embodiment, and thus the same effect as that in the first embodiment can be obtained.

  Note that the configuration of the hydraulic drive device provided in the hydraulic system according to the present invention is not limited to that of the first to third embodiments. For example, the number of fluid pumps may be one, or three or more.

  Moreover, although the 1st-3rd embodiment is equipped with the engine 1 as a motive power source of the fluid pump (P1) 2 and the fluid pump (P2) 3, it is a motive power source different from the engine 1, and a fluid pump (P1). 2. The fluid pump (P2) 3 may be driven.

  In the first to third embodiments, the P1 center bypass cut valve 120 and the P2 center bypass cut valve 121 are constituted by hydraulic valves, but these P1 center bypass cut valve 120 and P2 center bypass cut valve 121 may be configured by a solenoid valve.

  In addition, by arbitrarily controlling the opening / closing timing and / or opening / closing speed of the P1 center bypass cut valve 120 and / or the P2 center bypass cut valve 121, the shock caused by a sudden change in pressure in the hydraulic circuit is alleviated, The burden may be reduced and smoother operability may be obtained.

  The configuration of each unit is not limited to the illustrated embodiment, and various modifications can be made without departing from the gist of the present invention.

1 Engine 2 Fluid pump (P1)
3 Fluid pump (P2)
4 Pilot pump 5 P1 regulator 6 P2 regulator 7 P1 relief valve 8 P2 relief valve 9 P1 center bypass passage 10 P2 center bypass passage 21 SW valve (direction control valve)
22 AM2 valve (Directional control valve)
23 BM1 valve (Directional control valve)
24 TRL valve (Directional control valve)
25 AM1 valve (directional control valve)
26 BM2 valve (directional control valve)
27 BK valve (Directional control valve)
28 TRR valve (direction control valve)
41 to 44 Operation command device 53 Engine speed command device 54 Rotational speed sensor 55 Electronic cover 60 Vehicle body control device 61 Input unit 62 Storage unit 63 Calculation control unit 64 Output unit 65 Engine control unit 66 Input unit 67 Calculation control unit 68 Storage unit 69 Output unit 70 Pump flow rate control unit 71 P1 center bypass cut valve control unit 72 P1 flow rate selection unit 73 P1 capacity command value calculation unit 74 P2 center bypass cut valve control unit 75 P2 flow rate selection unit 76 P2 capacity command value calculation unit 80 P1 bleed OFF flow rate calculation system 81 BM1 bleed-off area calculation unit 82 AM2 bleed-off area calculation unit 83 SW bleed-off area calculation unit 84 TRL bleed-off area calculation unit 85 P1 equivalent bleed-off area calculation unit 86 P1 bleed-off flow rate calculation unit 90 P2 bleed OFF flow rate calculation system 91 BM2 bleed-off area calculation unit 92 BK bleed-off area calculation unit 93 AM2 bleed-off area calculation unit 94 TRR bleed-off area calculation unit 95 P2 equivalent bleed-off area calculation unit 96 P2 bleed-off flow rate calculation unit 100 traveling body 101 swinging body 102 front work machine 103 boom 104 arm 105 Bucket 106 Crawler 107 Boom cylinder (actuator)
108 Arm cylinder (actuator)
109 Bucket cylinder (actuator)
110 Swing motor (actuator)
111 Left travel motor (actuator)
112 Right travel motor (actuator)
120 P1 Center Bypass Cut Valve 121 P2 Center Bypass Cut Valve 122 P1 Center Bypass Cut Control Valve 123 P2 Center Bypass Cut Control Valve 124 P1 Control Pressure Control Valve 125 P2 Control Pressure Control Valve 126 Torque Control Pressure Control Valves 130-144 Pressure Sensor

Claims (4)

A variable displacement fluid pump driven by an engine and capable of adjusting a supply flow rate by an operation signal from a vehicle body control device, an actuator operated by a working fluid supplied from the fluid pump, and a center bypass connected to the fluid pump In a hydraulic system for a construction machine comprising a direction control valve provided in a passage and configured to control a flow rate and a direction of a working fluid supplied to the actuator,
A center bypass cut valve provided on the most downstream side of the directional control valve provided in the center bypass passage and capable of blocking the center bypass passage;
Provided in the vehicle body control device, and outputs a signal for operating the center bypass cut valve in accordance with the switching of the direction control valve, and when the center bypass passage is closed by the center bypass cut valve, A hydraulic system for a construction machine, comprising: a pump flow rate control unit that outputs a signal that sets a target supply flow rate of the fluid pump to a flow rate obtained by subtracting a bleed-off flow rate from an original supply flow rate of the fluid pump by calculation. . The hydraulic system for a construction machine according to claim 1,
An electromagnetic valve that operates the center bypass cut valve in response to a signal output from the pump flow rate control unit; and an electromagnetic valve that operates a regulator of the fluid pump in response to a signal output from the pump flow rate control unit. A hydraulic system for construction machinery, comprising: The hydraulic system for a construction machine according to claim 2,
The construction machine hydraulic system, wherein the center bypass cut valve comprises a hydraulic valve. The hydraulic system for a construction machine according to claim 1,
A hydraulic system for a construction machine comprising any one of a parallel type, a tandem type, and a tandem / parallel mixed type.