Working machine

Abstract

To provide a work machine capable of harmonizing the movements of a boom and a member to be driven by another hydraulic actuator.SOLUTION: The work machine includes a machine body, the boom supported on the machine body in an up-and-down swingable manner, a boom cylinder for swinging up and down the boom, a boom control valve for controlling the boom cylinder, a control device for controlling the boom control valve, and another hydraulic actuator than the boom cylinder. When performing combined control of another hydraulic actuator and the boom cylinder, the control device further reduces a change in the flow amount of working oil to be supplied from the boom control valve to the boom cylinder with a change in the operation amount of the boom cylinder, than when performing independent control of the boom cylinder.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a working machine such as a backhoe.

Background Art

[0002] Conventionally, a working machine disclosed in Patent Document 1 is known. The working machine disclosed in Patent Document 1 has a boom that is supported by the machine body so as to be vertically swingable. The boom is driven by a boom cylinder.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the boom cylinder and another hydraulic actuator different from the boom cylinder are operated in combination, the movement of the boom and the member driven by the other hydraulic actuator may not be coordinated. In view of the above problems, an object of the present invention is to provide a working machine capable of coordinating the movement of the boom and the member driven by another hydraulic actuator.

Means for Solving the Problems

[0005] A working machine according to an aspect of the present invention includes a machine body, a boom supported by the machine body so as to be vertically swingable, a boom cylinder that vertically swings the boom, an operation member that operates the boom cylinder, a boom control valve that changes the flow rate of the hydraulic oil supplied to the boom cylinder, and a control device that controls the operation of the boom control valve according to the operation amount of the operation member. On the tip side of the boom, an arm swingably connected in the direction approaching the boom, which is the arm cloud direction, and in the direction moving away from the boom, which is the arm dump direction; an arm cylinder for swinging the arm; a bucket swingably connected to the tip side of the arm; and is provided with the Arm cylinderWhen the boom cylinder is operated alone without driving, the flow rate of the hydraulic oil supplied from the boom control valve to the boom cylinder is controlled by proportionally controlling the operation of the boom control valve according to the operation amount of the operation member. Furthermore, when performing a combined operation of raising the boom while swinging the arm in the arm cloud direction or lowering the boom while swinging the arm in the arm dump direction to level the ground by horizontally moving the bucket, or when operating the boom cylinder alone with the same operation amount as the operation amount of the operation member on the boom cylinder in the case of the combined operation, a boom flow rate suppression unit is provided that reduces the flow rate of the hydraulic oil supplied from the boom control valve to the boom cylinder compared to the case of operating the boom cylinder alone. 。

Advantages of the Invention

[0006] According to the above working machine, when the boom cylinder and other hydraulic actuators are operated in combination, the movement of the boom and the members driven by other hydraulic actuators can be coordinated.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Modes for Carrying Out the Invention

[0008] Hereinafter, an embodiment of the present invention will be described with appropriate reference to the drawings. FIG. 1 is a schematic side view showing the overall configuration of the work machine 1 according to this embodiment. FIG. 2 is a schematic plan view of the work machine 1. In this embodiment, a backhoe which is a swing work machine is exemplified as the work machine 1. As shown in FIGS. 1 and 2, the work machine 1 includes a machine body (swing base) 2, a traveling device 3, and a working device 4. A cabin 5 is mounted on the machine body 2. Inside the cabin 5, a driver's seat 6 where an operator (driver) sits is provided.

[0009] In this embodiment, the direction facing the front side of the operator sitting on the driver's seat 6 of the work machine 1 (the direction of arrow A1 in FIGS. 1 and 2) is referred to as the front (front of the machine body), and the direction facing the rear side of the operator (the direction of arrow A2 in FIGS. 1 and 2) is referred to as the rear (rear of the machine body). Also, the direction of arrow K1 in FIGS. 1 and 2 is referred to as the front-rear direction (front-rear direction of the machine body). Further, the direction facing the left side of the operator (the front side in FIG. 1, the direction of arrow A3 in FIG. 2) is referred to as the left side, and the direction facing the right side of the operator (the back side in FIG. 1, the direction of arrow A4 in FIG. 2) is referred to as the right side. Also, the horizontal direction which is perpendicular to the front-rear direction (front-rear direction of the machine body) K1 is referred to as the machine body width direction K2 (see FIG. 2).

[0010] As shown in FIGS. 1 and 2, the traveling device 3 is a device that supports the machine body 2 so as to be able to travel. This traveling device 3 has a traveling frame 3A, a first traveling device 3L provided on the left side of the traveling frame 3A, and a second traveling device 3R provided on the right side of the traveling frame 3A. The first traveling device 3L and the second traveling device 3R are crawler-type traveling devices. The traveling device 3 is driven by a traveling motor M1 constituted by a hydraulic motor (hydraulic actuator). Specifically, the first traveling device 3L is driven by a first traveling motor ML, and the second traveling device 3R is driven by a second traveling motor MR.

[0011] At the front of the traveling device 3, a dozer device 7 is mounted. The dozer device 7 is driven by a dozer cylinder C1. Specifically, the dozer cylinder C1 is constituted by a hydraulic cylinder (hydraulic actuator), and by extending and contracting the dozer cylinder C1, the blade 7A of the dozer device 7 is raised and lowered. As shown in FIG. 1, the machine body 2 is supported on a traveling device 3 (traveling frame 3A) so as to be rotatable about a turning axis X1 via a slewing bearing 8. The turning axis X1 is an axis (vertical axis) extending in the vertical direction passing through the center of the slewing bearing 8.

[0012] As shown in FIG. 2, the cabin 5 is mounted on one side (left side) in the width direction K2 of the machine body 2. This cabin 5 is disposed closer to one side (left side) in the width direction K2 of the machine body than a center line Y1 passing through the turning axis X1 and extending in the front-rear direction K1. As shown in FIG. 2, a prime mover E1 is mounted on the other side (right side) in the width direction K2 of the machine body 2. The prime mover E1 is mounted vertically on the machine body 2. Being vertically mounted means that the axis of the crankshaft of the prime mover E1 is arranged in a state of extending in the front-rear direction K1. The prime mover E1 is a diesel engine. Note that the prime mover E1 may be a gasoline engine, an electric motor, or a hybrid type having an engine and an electric motor.

[0013] At the rear of the prime mover E1, a pressure oil supply unit 18 is provided. The pressure oil supply unit 18 is driven by the power of the prime mover E1 and pressurizes and discharges hydraulic oil used for a hydraulic drive unit. The hydraulic drive unit is, for example, a hydraulic actuator or the like equipped on the working machine 1. In front of the prime mover E1, a radiator R1, an oil cooler O1, and a capacitor CD are arranged and mounted on the machine body 2. The radiator R1 is a cooling device for cooling the cooling water (fluid) of the prime mover E1, and the oil cooler O1 is a cooling device for cooling the hydraulic oil (fluid). Also, the capacitor CD is a cooling device (condenser) for cooling the refrigerant (fluid) of an air conditioner equipped on the working machine 1.

[0014] A cooling fan F1 for generating cooling air for cooling the prime mover E1 is provided between the radiator R1 and the prime mover E1. The cooling fan F1 is driven by the power of the prime mover E1 to generate cooling air that flows from the front to the rear. As shown in FIG. 1, the machine body 2 has a base plate (hereinafter referred to as a swivel base plate) 9 that swivels around a swivel axis X1. The swivel base plate 9 is formed of a steel plate or the like and constitutes the bottom of the machine body 2. On the upper surface of the swivel base plate 9, vertical ribs 9A, which are reinforcing members, are provided from the front to the rear. In addition to the vertical ribs 9A, members for supporting loads such as equipment mounted on the machine body 2 are provided on the swivel base plate 9, thereby forming a swivel frame that serves as the skeleton of the machine body 2. The periphery of the swivel frame in the horizontal direction is covered by a swivel cover.

[0015] A weight 10 is provided at the rear of the machine body 2. The weight 10 is disposed at the rear of the machine body 2 and its lower part is attached to the swivel base plate 9. As shown in FIG. 2, a fuel tank T1 and a hydraulic oil tank T2 arranged side by side along the machine body width direction K2 are mounted at the rear of the machine body 2. The fuel tank T1 is a tank for storing fuel for the prime mover E1. The hydraulic oil tank T2 is a tank for storing hydraulic oil.

[0016] As shown in FIG. 2, a swivel motor MT is disposed at the front part of the swivel base plate 9 (machine body 2) and at the center in the machine body width direction K2. The swivel base plate 9 is swivel-driven around the swivel axis X1 by this swivel motor MT. The swivel motor MT is a hydraulic motor (hydraulic actuator). A swivel joint S1 is provided at the position of the swivel axis X1. The swivel joint S1 is a hydraulic device for circulating hydraulic oil and is a rotary joint (rotary joint) for circulating hydraulic oil between the hydraulic device on the machine body 2 side and the hydraulic device on the traveling device 3 side. A control valve (hydraulic device) CV is disposed behind the swivel joint S1. The control valve CV is a sectional type composite control valve (hydraulic device) having a plurality of control valves stacked and coupled in the vertical direction. A control device U1 is provided below the cabin 5.

[0017] Inside the cabin 5, a control device 1B for operating the working machine 1 is provided. The control device 1B is installed in front of the driver's seat 6. The driver's seat 6 and the control device 1B constitute the operation unit 1C. As shown in FIG. 2, the aircraft body 2 has a support bracket 13 at the front part, slightly to the right of the center in the aircraft body width direction K2. The support bracket 13 is fixed to the front part of the vertical rib 9A and is provided so as to protrude forward from the aircraft body 2. As shown in FIGS. 1 and 2, a swing bracket 14 is swingably attached around a swing axis X2, which is the axis extending in the vertical direction, to the front part (the part protruding from the aircraft body 2) of the support bracket 13 via a swing shaft 14A. Therefore, the swing bracket 14 is rotatable in the aircraft body width direction K2 (horizontally around the swing shaft 14A). As shown in FIG. 1, a working device 4 is supported by the swing bracket 14 (aircraft body 2).

[0018] The working device 4 includes a boom 15 swingably supported (swingable in the vertical direction) by the aircraft body 2, an arm 16 swingably pivotally connected to the boom 15, and a working tool (bucket) 17 swingably pivotally connected to the arm 16. The base of the boom 15 is pivotally supported on the upper part of the swing bracket 14 via a pivot. Specifically, the base of the boom 15 is pivotally attached to the upper part of the swing bracket 14 around a horizontal axis (axis extending in the aircraft body width direction K2) in a state where the boom 15 faces the front of the aircraft body. As a result, the boom 15 is swingable in the vertical direction. The arm 16 is pivotally supported on the tip side of the boom 15 via a pivot. Specifically, the arm 16 is pivotally attached to the boom 15 around a horizontal axis in a state where the boom 15 faces the front of the aircraft body. As a result, the arm 16 is swingable in the front-rear direction K1 or the vertical direction. Also, the arm 16 is swingable in the arm crowding direction D1, which is the direction approaching the boom 15, and the arm dump direction D2, which is the direction moving away from the boom 15.

[0019] The working implement 17 is pivotally supported at the tip end side of the arm 16 via a pivot. Specifically, the working implement 17 is pivotally attached to the arm 16 so as to be rotatable about a horizontal axis in a state where the boom 15 faces the front direction of the machine body. Accordingly, the working implement 17 can swing in a direction approaching the arm 16 (bucket crowd direction) and a direction separating from the arm 16 (bucket dump direction). Further, the bucket as the working implement 17 is provided on the arm 16 so as to be capable of a squeeze operation and a dump operation. The squeeze operation is an operation of swinging the working implement 17 in a direction approaching the boom 15, for example, an operation when scooping up earth and sand or the like. The dump operation is an operation of swinging the working implement 17 in a direction moving away from the boom 15, for example, an operation when dropping (discharging) the scooped earth and sand or the like.

[0020] Note that as the working implement 17, instead of the bucket, working implements (attachments) such as a pallet fork and a manit fork, and working implements having hydraulic actuators such as a grapple, a hydraulic crusher, an angle boom, an earth auger, a snow blower, a sweeper, a mower, and a hydraulic breaker (hydraulic attachments) can be attached. The swing bracket 14 can swing by the extension and contraction of a swing cylinder C2 provided in the machine body 2. The boom 15 can swing vertically by the extension and contraction of a boom cylinder C3. The arm 16 can swing in an arm crowd direction D1 and an arm dump direction D2 by the extension and contraction of an arm cylinder C4. The working implement 17 can swing in a bucket crowd direction and a bucket dump direction by the extension and contraction of a working implement cylinder (bucket cylinder) C5. The swing cylinder C2, the boom cylinder C3, the arm cylinder C4, and the working implement cylinder C5 are constituted by hydraulic cylinders (hydraulic actuators).

[0021] Next, a hydraulic system for operating various hydraulic actuators ML, MR, MT, C1 to C6 provided in the working machine 1 will be described with reference to FIGS. 3 to 7. As shown in Fig. 3, the hydraulic system includes a control valve CV, a pressure oil supply unit 18, and a flow control unit 19. The control valve CV is configured by aggregating, in one direction, control valves V1 to V10 for controlling various hydraulic actuators ML, MR, MT, C1 to C6, an inlet block B2 for taking in pressure oil, and a pair of outlet blocks B1, B3 for discharging pressure oil.

[0022] As shown in Fig. 3, in this embodiment, the control valve CV includes a first outlet block B1, a work implement control valve V1 for controlling the work implement cylinder C5, a boom control valve V2 for controlling the boom cylinder C3, a first dozer control valve V3 for controlling the dozer cylinder C1, a second travel control valve V4 for controlling the travel motor MR of the second travel device 3R, an inlet block B2, a first travel control valve V5 for controlling the travel motor ML of the first travel device 3L, a second dozer control valve V6 for controlling the dozer cylinder C1, an arm control valve V7 for controlling the arm cylinder C4, a swing control valve V8 for controlling the swing motor MT, a swing control valve V9 for controlling the swing cylinder C2, an SP control valve V10 for controlling an attachment actuator (hydraulic actuator) C6 equipped on the hydraulic attachment when the hydraulic attachment is attached as the work implement 17, and a second outlet block B3, which are arranged in order (arranged in order from the right in Fig. 3) and connected to each other.

[0023] As shown in FIGS. 4 to 7, each of the control valves V1 to V10 is configured by incorporating direction switching valves DV1 to DV10 and a pressure compensation valve (compensator valve) V11 in a valve body. The direction switching valves DV1 to DV10 are valves that switch the direction of the hydraulic oil with respect to the hydraulic actuators ML, MR, MT, C1 to C6 to be controlled. The pressure compensation valve V11 is disposed on the downstream side of the pressure oil supply to the direction switching valves DV1 to DV10 and on the upstream side of the pressure oil supply to the hydraulic actuators ML, MR, MT, C1 to C6 to be controlled. The pressure compensation valve V11 functions as an adjustment of the load among the hydraulic actuators ML, MR, MT, C1 to C6 when a plurality of the control valves V1 to V10 are used.

[0024] A first relief valve V12 and a first unloading valve V13 are incorporated in the first outlet block B1, and a traveling independent valve V14 is incorporated in the inlet block B2. The first relief valve V12 is a main relief valve that defines the pressure of the hydraulic oil discharged from a first pressure oil discharge port P1, which will be described later. The traveling independent valve V14 is composed of a direct-acting spool type switching valve and is also composed of a pilot-operated switching valve that is switched by a pilot control pressure. A second relief valve V15 and a second unloading valve V16 are incorporated in the second outlet block B3. The second relief valve V15 is a main relief valve that defines the pressure of the hydraulic oil discharged from a second pressure oil discharge port P2, which will be described later.

[0025] Each of the direction switching valves DV1 to DV10 is constituted by a direct-acting spool type switching valve. Also, each of the direction switching valves DV1 to DV10 is a control valve that is electrically controlled by the control device U1. Specifically, for example, a pilot type proportional solenoid valve is adopted for each of the direction switching valves DV1 to DV10. The pilot type proportional solenoid valve is a valve that controls the direction and flow rate of the working oil by moving the spool with a pilot control pressure controlled by a proportional solenoid. Specifically, the pilot type proportional solenoid valve is a two-stage direction and flow rate control valve that employs a proportional solenoid pressure reducing valve having two proportional solenoids in the pilot section. The flow rate is controlled by changing the input current to the proportional solenoid, and the direction is controlled by applying current to either one of the two proportional solenoids.

[0026] As shown in FIG. 4, the hydraulic pump as a pressure oil supply source in this hydraulic system is equipped with a first pump 21 for supplying working oil to operate the hydraulic actuators ML, MR, MT, C1 to C6, and a second pump 22 for supplying signal pressure oil such as a pilot control pressure and a detection signal. These first pump 21 and second pump 22 are provided in the pressure oil supply unit 18 and are driven by the prime mover E1.

[0027] The first pump 21 is a variable displacement type pump, and in this embodiment, it is a swash plate type variable displacement axial pump having a function of an equal flow double pump that discharges an equal amount of working oil from two independent pressure oil discharge ports P1 and P2. Specifically, the first pump 21 employs a split flow type hydraulic pump having a mechanism that alternately discharges working oil from one piston-cylinder barrel kit to discharge grooves formed inside and outside the valve plate.

[0028] One of the pressure oil discharge ports discharged from the first pump 21 is referred to as the first pressure oil discharge port P1, and the other pressure oil discharge port is referred to as the second pressure oil discharge port P2. In this embodiment, the pressure oil discharge ports discharged from the hydraulic pump having two pump functions are the first and second pressure oil discharge ports P1 and P2. However, the pressure oil discharge port of one of the two separately formed hydraulic pumps may be the first pressure oil discharge port, and the pressure oil discharge port of the other hydraulic pump may be the second pressure oil discharge port. The pressure oil supply unit 18 is equipped with a pressing piston 23 that presses the swash plate of the first pump 21 and a flow compensation piston 24 that controls the swash plate of the first pump 21.

[0029] The first pump 21 is configured such that the swash plate is pressed in the direction of increasing the pump flow rate via the pressing piston 23 by the self-pressure of the first pump 21, and a force that counteracts the pressing force of the pressing piston 23 is applied to the swash plate by the flow compensation piston 24. By controlling the pressure acting on the flow compensation piston 24, the discharge flow rate of the first pump 21 is controlled. Therefore, when the pressure acting on the flow compensation piston 24 leaks, the first pump 21 discharges the maximum flow rate with the swash plate angle being MAX.

[0030] As shown in FIG. 4, the flow control unit 19 controls the swash plate of the first pump 21. The swash plate control of the first pump 21 is performed by controlling the pressure acting on the flow compensation piston 24 by controlling the flow compensation valve V17 provided in the flow control unit 19. The pressure oil supply unit 18 is provided with a spring 25 and a spool 26 for controlling the pump horsepower (torque) of the first pump 21. When the discharge pressure of the first pump 21 reaches a preset pressure, the horsepower (torque) absorbed by the first pump 21 from the prime mover E1 is restricted. The second pump 22 is constituted by a fixed displacement gear pump, and the discharged oil of the second pump 22 is discharged from the third pressure oil discharge port P3.

[0031] The first pressure oil discharge port P1 is connected to the inlet block B2 via the first discharge path a, and the second pressure oil discharge port P2 is connected to the inlet block B2 via the second discharge path b. The first discharge path a is connected to the first pressure oil supply path d, and the first pressure oil supply path d is formed to reach the first outlet block B1 from the inlet block B2 through the valve body of the second travel control valve V4 → the valve body of the first dozer control valve V3 → the valve body of the boom control valve V2 → the valve body of the work implement control valve V1. At the first outlet block B1 (at the flow path end side), it is branched and connected to the first relief valve V12 and the first unloading valve V13. Hydraulic oil can be supplied from the first pressure oil supply path d to the direction switching valves DV4, DV3, DV2, DV1 of the second travel control valve V4, the first dozer control valve V3, the boom control valve V2, and the work implement control valve V1 through the pressure oil branch path f.

[0032] The first relief valve V12 and the first unloading valve V13 are connected to the drain oil path g. The drain oil path g is formed to reach the second outlet block B3 from the first outlet block B1 through the valve body of the work implement control valve V1 → the valve body of the boom control valve V2 → the valve body of the first dozer control valve V3 → the valve body of the second travel control valve V4 → the inlet block B2 → the valve body of the first travel control valve V5 → the valve body of the second dozer control valve V6 → the valve body of the arm control valve V7 → the valve body of the swing control valve V8 → the valve body of the swing control valve V9 → the valve body of the SP control valve V10. The hydraulic oil flowing through the drain oil path g is discharged from the second outlet block B3 to the hydraulic oil tank T2.

[0033] The second discharge path b is connected to the second pressure oil supply path e. The second pressure oil supply path e is formed so as to reach the second outlet block B3 from the inlet block B2 through the valve body of the first travel control valve V5 → the valve body of the second control valve V6 for the dozer → the valve body of the arm control valve V7 → the valve body of the swing control valve V8 → the valve body of the swing control valve V9 → the valve body of the SP control valve V10, and is branched at the second outlet block B3 (on the flow path end side) and connected to the second relief valve V15 and the second unloading valve V16.

[0034] Hydraulic oil can be supplied from the second pressure oil supply path e to the direction switching valves DV5, DV6, DV7, DV8, DV9, DV10 of the first travel control valve V5, the second control valve V6 for the dozer, the arm control valve V7, the swing control valve V8, the swing control valve V9, and the SP control valve V10 via the pressure oil branch path h. The hydraulic oil supplied to each control valve V1 - V10 is supplied and discharged to each hydraulic actuator ML, MR, MT, C1 - C6. That is, the hydraulic system has a hydraulic circuit that supplies and discharges hydraulic oil to each hydraulic actuator ML, MR, MT, C1 - C6.

[0035] The second relief valve V15 and the second unloading valve V16 are connected to the drain oil path g. The first pressure oil supply path d and the second pressure oil supply path e are connected to each other via a communication path j that crosses the travel independent valve V14 within the inlet block B2. The travel independent valve V14 is switchable between an independent position 27 that blocks the pressure oil flow in the communication path j and a confluence position 28 that allows the pressure oil flow in the communication path j.

[0036] When the traveling independent valve V14 is switched to the independent position 27, the hydraulic oil from the first hydraulic oil discharge port P1 can be supplied to the direction switching valves DV4 and DV3 of the second traveling control valve V4 and the first control valve V3 for the dozer, and the hydraulic oil from the second hydraulic oil discharge port P2 can be supplied to the direction switching valves DV5 and DV6 of the first traveling control valve V5 and the second control valve V6 for the dozer. The hydraulic oil from the first hydraulic oil discharge port P1 is not supplied to the first traveling control valve V5 and the second control valve V6 for the dozer, and the hydraulic oil from the second hydraulic oil discharge port P2 is not supplied to the second traveling control valve V4 and the first control valve V3 for the dozer.

[0037] Also, when the traveling independent valve V14 is switched to the confluence position 28, the hydraulic oil from the first hydraulic oil discharge port P1 and the hydraulic oil from the second hydraulic oil discharge port P2 are confluent and can be supplied to the direction switching valves DV1 to DV10 of the control valves V1 to V10. The third hydraulic oil discharge port P3 is connected to the inlet block B2 via the third discharge path m. The third discharge path m is branched into a first branch oil path m1 and a second branch oil path m2 on the way and is connected to the inlet block B2.

[0038] The first branch oil path m1 is connected to the pressure receiving portion 14a on one side of the traveling independent valve V14 via the first signal oil path n1, and the second branch oil path m2 is connected to the pressure receiving portion 14b on the other side of the traveling independent valve V14 via the second signal oil path n2. A first detection oil path r1 is connected to the first signal oil path n1, and a second detection oil path r2 is connected to the second signal oil path n2.

[0039] The first detection oil path r1 is connected to the drain oil path g via the direction switching valve DV6 of the second control valve V6 for the dozer → the direction switching valve DV5 of the first traveling control valve V5 → the direction switching valve DV4 of the second traveling control valve V4 → the direction switching valve DV3 of the first control valve V3 for the dozer from the first signal oil path n1. The second oil drain passage r2 is connected to the drain passage g via the direction switching valves DV10 of the SP control valve V10, DV9 of the swing control valve V9, DV8 of the slewing control valve V8, DV7 of the arm control valve V7, DV6 of the dozer second control valve V6, DV5 of the first travel control valve V5, DV4 of the second travel control valve V4, DV3 of the dozer first control valve V3, DV2 of the boom control valve V2, and DV1 of the work implement control valve V1 from the second signal passage n2.

[0040] When the direction switching valves DV1 to DV10 of the respective control valves V1 to V10 are in the neutral position, the travel independent valve V14 is held at the merging position 28 by the force of a spring. When any one of the direction switching valves DV of the second travel control valve V4, the first travel control valve V5, the dozer first control valve V3, and the dozer second control valve V6 is operated from the neutral position, pressure builds up in the first oil drain passage r1 and the first signal passage n1, and the travel independent valve V14 is switched from the merging position 28 to the independent position 27.

[0041] Therefore, when only traveling, when using the dozer device 7 while traveling, or when only using the dozer device 7, the hydraulic oil from the first hydraulic oil discharge port P1 is supplied to the direction switching valves DV of the second travel control valve V4 and the dozer first control valve V3, and the hydraulic oil from the second hydraulic oil discharge port P2 is supplied to the direction switching valves DV of the first travel control valve V5 and the dozer first control valve V3.

[0042] At this time, when any one of the direction switching valves DV10, DV9, DV8, DV7, DV2, DV1 of the SP control valve V10, the swing control valve V9, the slewing control valve V8, the arm control valve V7, the boom control valve V2, and the work implement control valve V1 is operated from the neutral position, pressure builds up in the second oil drain passage r2 and the second signal passage n2, and the travel independent valve V14 is switched from the independent position 27 to the merging position 28.

[0043] Also, when the direction change valves DV1 to DV10 of the control valves V1 to V10 are in the neutral position, even when any of the direction change valves DV10, DV9, DV8, DV7, DV2, DV1 of the SP control valve V10, the swing control valve V9, the slewing control valve V8, the arm control valve V7, the boom control valve V2, and the work implement control valve V1 is operated from the neutral position, the travel independent valve V14 is in the merging position 28.

[0044] Therefore, simultaneous operation of the boom 15, the arm 16, the work implement 17, the swing bracket 14, the machine body 2, and the dozer device 7 is enabled during non-travel or travel. Further, in this hydraulic system, an auto-idling control system (AI system) for automatically operating the accelerator device of the prime mover E1 is provided. This AI system includes an AI switch (pressure switch) 29 connected to the first branch oil passage m1 and the second branch oil passage m2 of the third discharge oil passage m via a sensing oil passage s and a shuttle valve V18, an electric actuator for controlling the governor of the prime mover E1, and a control device for controlling this electric actuator, and the AI switch 29 is connected to the control device.

[0045] In this AI system, when the direction change valves DV1 to DV10 of the control valves V1 to V10 are in the neutral position, no pressure builds up in the first branch oil passage m1 and the second branch oil passage m2, so the AI switch 29 does not operate due to pressure sensing. In this state, the governor is automatically controlled by an electric actuator or the like to decelerate the accelerator to a preset idling position.

[0046] Also, when any one of the direction change valves DV1 to DV10 of the control valves V1 to V10 is operated, pressure builds up in the first branch oil passage m1 or the second branch oil passage m2, and this pressure is sensed by the AI switch 29 and the AI switch 29 operates due to pressure sensing. Then, a command signal is sent from the control device to an electric actuator or the like, and the governor is automatically controlled by the electric actuator or the like to accelerate up to the set accelerator position.

[0047] In addition, a load sensing system is adopted in this hydraulic system. The load sensing system of this embodiment includes pressure compensation valves V11 provided in each control valve V1 to V10, a flow compensation piston 24 for controlling the swash plate of the first pump 21, a flow compensation valve V17 equipped in the flow control unit 19, the first and second relief valves V12 and V15, and the first and second unloading valves V13 and V16. Further, in the load sensing system of this embodiment, an after orifice type load sensing system is adopted in which the pressure compensation valve V11 is arranged on the downstream side of the pressure oil supply to the direction switching valves DV1 to DV10.

[0048] In this load sensing system, when a plurality of hydraulic actuators ML, MR, MT, C1 to C6 equipped in the working machine 1 are simultaneously operated, the pressure compensation valve V11 functions as an adjustment of the load among the hydraulic actuators ML, MR, MT, C1 to C6, generating a pressure loss corresponding to the differential pressure from the maximum load pressure on the control valves V1 to V10 on the low load pressure side, and enabling a flow rate (distribution) corresponding to the operation amount of the spool of the direction switching valves DV1 to DV10 to flow regardless of the load magnitude. That is, the load sensing system controls the first pump 21 so that the differential pressure obtained by subtracting the maximum load pressure among the plurality of hydraulic actuators ML, MR, MT, C1 to C6 from the discharge pressure of the first pump 21 becomes a constant pressure.

[0049] In addition, the load sensing system can improve power saving and operability by controlling the discharge amount of the first pump 21 according to the load pressure of each hydraulic actuator ML, MR, MT, C1 to C6 equipped in the working machine 1 and discharging the hydraulic power required for the load from the first pump 21. The load sensing system of this embodiment will be described in more detail. The load sensing system has a PLS signal oil passage w that transmits the maximum load pressure among the load pressures of each control valve V1 to V10 as a PLS signal pressure to the flow compensation valve V17, and a PPS signal oil passage x that transmits the discharge pressure of the first pump 21 as a PPS signal pressure to the flow compensation valve V17.

[0050] The PLS signal oil passage w is provided from the first outlet block B1 to the valve body of the working tool control valve V1 → the valve body of the boom control valve V2 → the valve body of the dozer first control valve V3 → the valve body of the second travel control valve V4, and also passes across the travel independent valve V14 to the valve body of the first travel control valve V5 → the valve body of the dozer second control valve V6 → the valve body of the arm control valve V7 → the valve body of the slewing control valve V8 → the valve body of the swing control valve V9 → the valve body of the SP control valve V10 → the second outlet block B3. The PLS signal oil passage w is connected to the pressure compensation valve V11 via the load transmission line y in each control valve.

[0051] Also, this PLS signal oil passage w is connected to one side of the spool of the flow compensation valve V17 from the second outlet block B3, and the PPS signal pressure acts on one side of the spool of the flow compensation valve V17. Furthermore, the PLS signal oil passage w is connected to the first unloading valve V13 and the drain oil passage g at the first outlet block B1, and is connected to the second unloading valve V16 and the drain oil passage g at the second outlet block B3.

[0052] When the travel independent valve V14 is in the confluence position 28, the line w1 of the PLS signal oil passage w from the travel independent valve V14 to the first outlet block B1 and the line w2 from the travel independent valve V14 to the second outlet block B3 are in communication. When the travel independent valve V14 is switched from the confluence position 28 to the independent position 27, the PLS signal oil passage w is blocked by the travel independent valve V14. As a result, when the PLS signal oil passage w has the travel independent valve V14 in the independent position 27, it is divided into the line w1 on the side where the hydraulic oil is supplied from the first pressure oil discharge port P1 and the line w2 on the side where the pressure oil is supplied from the second pressure oil discharge port P2.

[0053] The PPS signal oil passage x is provided from the traveling independent valve V14 across to the other side of the spool of the flow compensation valve V17. When the traveling independent valve V14 is at the confluence position 28, the PPS signal oil passage x is communicated with the second pressure oil supply passage e through the connection oil passage z, and the PPS signal pressure (the discharge pressure of the first pump 21) acts on the other side of the spool of the flow compensation valve V17. When the traveling independent valve V14 is switched to the independent position 27, the PPS signal oil passage x is communicated with the drain oil passage g through the relief oil passage q, and is configured such that the PPS signal pressure becomes zero. Also, on one side of the spool of the flow compensation valve V17, a spring 30 and a differential pressure piston 31 that apply a control differential pressure to the flow compensation valve V17 are provided.

[0054] In the hydraulic system with the above configuration, when the direction switching valves DV1 to DV10 of each control valve V1 to V10 are in the neutral position, the traveling independent valve V14 is at the confluence position 28. At this time, the flow path end side of the first pressure oil supply passage d is blocked by the first unloading valve V13 and the flow path end side of the second pressure oil supply passage e is blocked by the second unloading valve V16. Therefore, when the discharge pressure (PPS signal pressure) of the first pump 21 rises and the difference between this PPS signal pressure and the PLS signal pressure (which is zero at this time) becomes larger than the control differential pressure, the first pump 21 is flow-controlled in the direction of decreasing the discharge amount and the first and second unloading valves V16 open to drop the discharge oil from the first pump 21 into the hydraulic oil tank T2.

[0055] Therefore, in this state, the discharge pressure of the first pump 21 becomes the pressure set by the first and second unloading valves V13 and V16, and the discharge flow rate of the first pump 21 becomes the minimum discharge amount. Next, the case of simultaneously operating any two or more of the boom cylinder C3, arm cylinder C4, work implement cylinder C5, swing cylinder C2, swing motor MT, and hydraulic attachment, or the case of simultaneously operating any one or more of these and any one or more of the left and right traveling motors ML, MR, and dozer cylinder C1 will be described.

[0056] In this case, the traveling independent valve V14 is in the merging position 28, and the maximum load pressure acting on the operated hydraulic actuators ML, MR, MT, C1 to C6 becomes the PLS signal pressure, and the discharge pressure (discharge flow rate) of the first pump 21 is automatically controlled so that the PPS signal pressure - PLS signal pressure becomes the control differential pressure (so as to maintain the difference between the PPS signal pressure and the PLS signal pressure at the set value). That is, when the unloading flow rate through the first and second unloading valves V13, V16 becomes zero, the discharge flow rate of the first pump 21 starts to increase, and the total amount of the discharged oil of the first pump 21 flows to the operated hydraulic actuators ML, MR, MT, C1 to C6 according to the operation amount of the operated control valve.

[0057] Also, by the pressure compensation valve V11, the front-rear differential pressure of the spools of the direction switching valves DV1 to DV10 of the operated control valves V1 to V10 becomes constant, and regardless of the difference in the magnitude of the load acting on the operated hydraulic actuators ML, MR, MT, C1 to C6, the discharge flow rate of the first pump 21 is divided into amounts corresponding to the operation amounts for the respective operated hydraulic actuators ML, MR, MT, C1 to C6.

[0058] When the required flow rate of the hydraulic actuators ML, MR, MT, C1 to C6 exceeds the maximum discharge flow rate of the first pump 21, the discharged oil of the first pump 21 is proportionally distributed to the respective operated hydraulic actuators ML, MR, MT, C1 to C6. In the above case, an efficient system enables simultaneous operation (compound operation). When performing earthwork by the dozer device 7 while traveling, the traveling independent valve V14 is switched to the independent position 27, and by the traveling independent valve V14, the communication passage j and the PLS signal oil passage w are blocked, and the PPS signal oil passage x communicates with the drain oil passage g via the relief oil passage q, and the PPS signal pressure becomes zero.

[0059] Therefore, the hydraulic oil from the first pressure oil discharge port P1 flows to the second travel control valve V4 and the first dozer control valve V3, and does not flow to the first travel control valve V5 and the second dozer control valve V6. Also, the hydraulic oil from the second pressure oil discharge port P2 flows to the first travel control valve V5 and the second dozer control valve V6, and does not flow to the second travel control valve V4 and the first dozer control valve V3. Further, since the PPS signal pressure is zero, the first pump 21 discharges the maximum flow rate with the swash plate angle at MAX.

[0060] As shown in FIG. 8, the proportional solenoids so1 to so10 of the direction switching valves DV1 to DV10 are connected to the control device U1. Each of the direction switching valves DV1 to DV10 (each control valve V1 to V10) is pilot-operated by a pilot control pressure corresponding to a control signal (current value supplied to the proportional solenoids so1 to so10) transmitted from the control device U1 to the proportional solenoids so1 to so10, so that the flow direction and flow rate of the hydraulic oil to the hydraulic actuators ML, MR, MT, C1 to C6 to be controlled are controlled. That is, each of the control valves V1 to V10 is pilot-operated by a pilot control pressure controlled by a control signal transmitted from the control device U1. In other words, each of the control valves V1 to V10 is controlled according to the current value supplied by the control device U1.

[0061] An operating member 41 (first operating tools 41A to seventh operating tools 41G) for operating each of the direction switching valves DV1 to DV10 (each control valve V1 to V10) is connected to the control device U1. The control device U1 supplies (transmits) a current value (control signal) corresponding to the operation amount of the operating member 41 to the proportional solenoids so1 to so10 of the direction switching valves DV1 to DV10 to be operated. The first operating tool 41A and the second operating tool 41B are provided on the operating device 1B and are constituted by, for example, a handle that is gripped and operated by an operator seated on the driver's seat 6.

[0062] The first operating tool 41A can operate two operation targets equipped on the working machine 1. For example, the first operating tool 41A can operate the direction switching valve DV8 (swing motor MT) (enable the machine body 2 to swing) and can operate the direction switching valve DV7 (arm cylinder C4) (enable the arm 16 to swing). Also, the first operating tool 41A has a sensor (operation detection unit) 42 (first sensor 42A) that detects the operation direction and operation amount. The first sensor 42A is connected to the control device U1. The control device U1 controls the swing control valve V8 (machine body 2) and the arm control valve V7 (arm 16) based on the detection signal from the first sensor 42A.

[0063] The second operating tool 41B can also operate two operation targets equipped on the working machine 1. For example, the second operating tool 41B can operate the direction switching valve DV2 (boom cylinder C3) (enable the boom 15 to swing) and can operate the direction switching valve DV1 (tool cylinder C5) (enable the working tool 17 to swing). Also, the second operating tool 41B has a sensor (operation detection unit) 42 (second sensor 42B) that detects the operation direction and operation amount. The second sensor 42B is connected to the control device U1. The control device U1 controls the boom control valve V2 (boom 15) and the tool control valve V1 (working tool 17) based on the detection signal from the second sensor 42B.

[0064] The third operating tool 41C is provided on the operating device 1B and is constituted by, for example, a lever. The third operating tool 41C can operate the direction switching valve DV3 and the direction switching valve DV6 (dozer cylinder C1) (enable the dozer device 7 to operate). Also, the third operating tool 41C has a sensor 42 (third sensor 42C) that detects the operation direction and operation amount. The third sensor 42C is connected to the control device U1. The control device U1 controls the first control valve V3 for dozer and the second control valve V6 for dozer (dozer device 7) based on the detection signal from the third sensor 42C.

[0065] The fourth operating tool 41D and the fifth operating tool 41E are provided, for example, on the floor portion in front of the driver's seat 6 and are constituted by pedals operated by the operator's stepping operation. The fourth operating tool 41D can operate the direction switching valve DV5 (the first traveling motor ML) (can operate the first traveling device 3L). Further, the fourth operating tool 41D has a sensor 42 (the fourth sensor 42D) that detects the operating direction and the operating amount. The fourth sensor 42D is connected to the control device U1. The control device U1 controls the first traveling control valve V5 (the first traveling device 3L) based on the detection signal from the fourth sensor 42D.

[0066] The fifth operating tool 41E can operate the direction switching valve DV4 (the second traveling motor MR) (can operate the second traveling device 3R). Further, the fifth operating tool 41E has a sensor 42 (the fifth sensor 42E) that detects the operating direction and the operating amount. The fifth sensor 42E is connected to the control device U1. The control device U1 controls the second traveling control valve V4 (the second traveling device 3R) based on the detection signal from the fifth sensor 42E.

[0067] The sixth operating tool 41F is constituted by, for example, a switch (such as a toggle switch or a slide switch) provided on the first operating tool 41A or the second operating tool 41B. The sixth operating tool 41F can operate the direction switching valve DV9 (the swing cylinder C2) (can operate the swing bracket 14). Further, the sixth operating tool 41F has a sensor 42 (the sixth sensor 42F) that detects the operating direction and the operating amount. The sixth sensor 42F is connected to the control device U1. The control device U1 controls the swing control valve V9 (the swing bracket 14) based on the detection signal from the sixth sensor 42F.

[0068] The seventh operating tool 41G is constituted by, for example, a switch (such as a seesaw switch or a slide switch) provided on the first operating tool 41A or the second operating tool 41B. The seventh operating tool 41G can operate a direction switching valve DV10 (a hydraulic actuator of a hydraulic attachment) (can operate a hydraulic attachment as a working tool). Further, the seventh operating tool 41G has a sensor 42 (seventh sensor 42G) that detects an operating direction and an operating amount. The seventh sensor 42G is connected to a control device U1. The control device U1 controls an SP control valve V10 (hydraulic attachment) based on a detection signal from the seventh sensor 42G.

[0069] The configuration of the sensor 42 (first sensor 42A to seventh sensor 42G) is not particularly limited, and for example, a potentiometer or the like can be used. The spools of the respective direction switching valves DV1 to DV10 are moved in proportion to the operating amounts of the respective operating members 41 that operate the respective direction switching valves DV1 to DV10 (respective control valves V1 to V10), and are configured to supply a hydraulic oil in an amount proportional to the amount by which the respective direction switching valves DV1 to DV10 are moved to the hydraulic actuators ML, MR, MT, C1 to C6 to be controlled. That is, the operating speed of the operation target (control target) can be changed in proportion to the operating amount of each operating member 41.

[0070] As described above, the control valves V1 to V10 are operated by operating the operating member 41, and thereby, the corresponding hydraulic actuators ML, MR, MT, C1 to C6 are operated. Then, the driving parts (airframe 2, traveling device 3, dozer device 7, boom 15, arm 16, working tool 17, hydraulic attachment) are driven by the hydraulic actuators ML, MR, MT, C1 to C6. FIG. 8 shows a first embodiment of the control system. As shown in FIG. 8, the control device U1 has a control unit Ua and a boom flow rate suppression unit Ub.

[0071] When the control unit Ua operates the boom cylinder C3 (boom control valve V2) alone (single operation), it controls the boom control valve V2. When the boom flow rate suppression unit Ub simultaneously operates (performs a combined operation) the boom cylinder C3 (boom control valve V2) and the arm cylinder C4 (arm control valve V7), it controls the boom control valve V2. Specifically, when the boom cylinder C3 (boom control valve V2) is operated while the arm cylinder C4 (arm control valve V7) is being operated, the boom flow rate suppression unit Ub controls the flow rate of the hydraulic oil (hydraulic oil flow rate) supplied from the boom control valve V2 to the boom cylinder C3.

[0072] FIG. 9 is a graph showing the relationship between the operation amount of the operation member 41 and the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3, with the horizontal axis representing the operation amount of the operation member 41 (second operating tool 41B) and the vertical axis representing the flow rate of the hydraulic oil. The first line 50 in FIG. 9 shows the case where the control unit Ua controls the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 with respect to the operation amount of the operation member 41. That is, it shows the change in the hydraulic oil flow rate corresponding to the operation amount of the boom cylinder C3 when the boom cylinder C3 is operated alone.

[0073] The second line 51 in FIG. 9 shows the case where the boom flow rate suppression unit Ub controls the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 with respect to the operation amount of the operation member 41. That is, it shows the change in the hydraulic oil flow rate corresponding to the operation amount of the boom cylinder C3 when the boom cylinder C3 and the arm cylinder C4 are operated in combination. The reference numeral 52 in FIG. 9 indicates the change amount of the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 with respect to the change in the operation amount of the boom cylinder C3 when the boom cylinder C3 is operated alone. The reference numeral 53 in FIG. 9 indicates the change amount of the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 with respect to the change in the operation amount of the boom cylinder C3 when the arm cylinder C4 and the boom cylinder C3 are operated in combination.

[0074] As can be seen from FIG. 9, the second line 51 has a smaller slope than the first line 50, and the change amount 53 is smaller than the change amount 52. That is, when the control device U1 performs a combined operation of the arm cylinder C4 and the boom cylinder C3, the change amount 53 of the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 with respect to the change in the operation amount of the boom cylinder C3 is made smaller than when the boom cylinder C3 is operated alone. Also, as shown in FIG. 9, in the first embodiment, the boom flow rate suppression unit Ub reduces the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 when the arm cylinder C4 and the boom cylinder C3 are operated in combination, thereby making the change amount 53 smaller than the change amount 52.

[0075] Specifically, as can be seen from the first line 50 and the second line 51 in FIG. 9, when the operation amount of the operation member 41 (the second operation tool 41B) is the same in the case of operating the boom cylinder C3 (boom control valve V2) alone and the case of performing a combined operation of the arm cylinder C4 (arm control valve V7) and the boom cylinder C3 (boom control valve V2), compared with the case of operating the boom cylinder C3 (boom control valve V2) alone, the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 is smaller when performing a combined operation of the arm cylinder C4 (arm control valve V7) and the boom cylinder C3 (boom control valve V2). That is, when performing a combined operation of the arm cylinder C4 (arm control valve V7) and the boom cylinder C3 (boom control valve V2), the supply flow rate of the hydraulic oil to the boom cylinder C3 with respect to the operation amount of the operation member 41 (the second operation tool 41B) decreases.

[0076] That is, the boom flow rate suppression unit Ub causes the boom control valve V2 to supply the boom cylinder C3 with hydraulic oil at a flow rate less than the flow rate of the hydraulic oil controlled by the control unit Ua for the same operation amount of the operation member 41. Therefore, when the boom cylinder C3 (boom control valve V2) is operated while the arm cylinder C4 (arm control valve V7) is being operated, the boom flow rate suppression unit Ub reduces the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3. In other words, the boom flow rate suppression unit Ub causes the boom control valve V2 to supply the boom cylinder C3 with hydraulic oil at a flow rate less than the flow rate of the hydraulic oil controlled by the control unit Ua according to the operation amount of the operation member 41 (second operating tool 41B).

[0077] In this embodiment, the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 is reduced by reducing the pilot control pressure controlled by the control signal transmitted from the control device U1 to the boom control valve V2. In other words, the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 is reduced by reducing the current value supplied by the control device U1 to the boom control valve V2.

[0078] Incidentally, as a case of performing a composite operation (simultaneous operation) of the boom 15 (boom cylinder C3) and the arm 16 (arm cylinder C4), there is a so-called horizontal pulling operation (horizontal pulling work). The horizontal pulling work is a work of leveling the ground by horizontally moving the bucket 17 by raising the boom 15 while swinging the arm 16 in the arm cloud direction D1 with the tip claw portion 17a (see FIG. 1) of the bucket 17 in contact with the ground. In this horizontal pulling work, skill is required to finely operate the boom 15. That is, generally, when the arm 16 is moved, the balance of the machine body 2 changes greatly, and thereby the operation amount of the operation member 41 (second operating tool 41B) for operating the boom 15 fluctuates, so skill is required. The same can be said for the case of lowering the boom 15 while swinging the arm 16 in the arm dump direction D2 with the tip claw portion 17a of the bucket 17 in contact with the ground.

[0079] In the first embodiment, when operating the boom 15 while operating the arm 16, the pilot control pressure is reduced compared to the case of operating the boom 15 alone, and the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 is decreased, thereby suppressing the raising speed of the boom 15, enabling the operation of the boom 15 to be stable, and making it easier for the tip claw portion 17a of the bucket 17 to move horizontally. As a result, when raising the boom 15 while swinging the arm 16 in the arm cloud direction D1, or when lowering the boom 15 while swinging the arm 16 in the arm dump direction D2, the operation of the boom 15 can be easily performed. In the first embodiment, for example, when the operation amount for the boom cylinder C3 and the operation amount for the arm cylinder C4 are the same operation amount and the speed of the arm 16 is slower than the speed of the boom 15, and during horizontal pulling work, by reducing the speed of the boom 15, the movement of the boom 15 and the arm 16 can be coordinated, and the horizontal pulling work can be performed well.

[0080] Also, since the large swing of the boom 15 can be suppressed, the shaking of the machine body 2 can be suppressed. Further, when operating the boom 15 while operating the arm 16, by reducing the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3, the flow rate of the hydraulic oil is diverted to the arm cylinder C4 accordingly, ensuring the moving speed of the bucket 17, making the boom characteristics gentle, and stabilizing the machine body 2. Moreover, since it is equipped with a load sensing system and the intermediate flow rate characteristics are stable, even if the flow rate of the hydraulic oil is decreased by reducing the pilot control pressure to lower the speed of the boom 15, stable movement can be achieved.

[0081] In addition, in this embodiment, when the boom cylinder C3 is operated while the arm cylinder C4 is being operated, the boom flow rate suppression unit Ub controls the boom control valve V2 to reduce the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3. However, the present invention is not limited to this. When the boom cylinder C3 is operated while another hydraulic actuator AC different from the boom cylinder C3 is being operated, the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 may be configured to decrease. That is, the boom flow rate suppression unit Ub controls the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 when the boom cylinder C3 is operated while another hydraulic actuator AC different from the boom cylinder C3 is being operated (when the boom cylinder C3 and another hydraulic actuator AC different from the boom cylinder C3 are operated in combination).

[0082] Another hydraulic actuator AC different from the boom cylinder C3 may be the travel motor M1, swing motor MT, dozer cylinder C1, swing cylinder C2, work implement cylinder C5, and attachment actuator C6 in addition to the arm cylinder C4. Further, even when another hydraulic actuator AC different from the boom cylinder C3 is a hydraulic actuator other than the arm cylinder C4, that is, the travel motor M1, swing motor MT, dozer cylinder C1, swing cylinder C2, work implement cylinder C5, and attachment actuator C6, an effect that the boom characteristics become gentle and the machine body 2 becomes stable can be expected.

[0083] Also, even when the boom cylinder C3 and another hydraulic actuator AC other than the arm cylinder C4 are operated in combination, it is possible to coordinate the movement between the boom 15 and the member driven by the other hydraulic actuator AC. In the above hydraulic system, each control valve V1 to V10 (each direction switching valve DV1 to DV10) is constituted by a pilot-type proportional solenoid valve, and the control device U1 controls the current value supplied to each control valve V1 to V10 to control the pilot control pressure, thereby controlling each control valve V1 to V10. However, the present invention is not limited thereto.

[0084] For example, as shown in FIG. 10, each control valve V1 to V10 is constituted by a pilot-operated switching valve that is pilot-operated by a pilot control pressure acting on a pair of pilot pressure-receiving portions Va1 and Va2, and a pair of proportional solenoid valves V21 and V22 controlled by the control device U1 are provided. A pilot control pressure is supplied from one proportional solenoid valve V21 to one pilot pressure-receiving portion Va1, and a pilot control pressure is supplied from the other proportional solenoid valve V22 to the other pilot pressure-receiving portion Va2, so that the direction and flow rate of the hydraulic oil flowing to the hydraulic actuators MT, ML, MR, C1 to C6 may be controlled.

[0085] Also, as shown in FIG. 11, each control valve V1 to V10 may be constituted by a proportional electromagnetic direction / flow control valve that directly drives a spool by a proportional solenoid so11 to which current is supplied from the control device U1. FIG. 12 shows a second embodiment of the control system. As shown in FIG. 12, a switching switch SW is connected to the control device U1. The switching switch SW is a switch for switching to a crane mode in which a suspended load is lifted by a hook provided on the bucket 17.

[0086] The control device U1 includes a control unit Ua, a boom flow rate increasing unit Uc, and a function blocking unit Ud. The control unit Ua controls the boom control valve V2 when operating the boom cylinder C3 (boom control valve V2) alone. When the boom flow rate increasing unit Uc simultaneously operates (performs a combined operation) the boom cylinder C3 (boom control valve V2) and the arm cylinder C4 (arm control valve V7), it controls the boom control valve V2. Specifically, when the boom flow rate increasing unit Uc performs a combined operation of the arm cylinder C4 (arm control valve V7) and the boom cylinder C3 (boom control valve V2), it controls to increase the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3.

[0087] When the function blocking unit Ud operates the arm cylinder C4 (another hydraulic actuator AC different from the boom cylinder C3) while the boom cylinder C3 is being operated alone in the upward direction of the boom 15, it does not enable the function of the boom flow rate increasing unit Uc. In the present embodiment, the function blocking unit Ud functions when it is switched to the crane mode by the changeover switch SW. When the boom flow rate increasing unit Uc performs a combined operation of the boom cylinder C3 and the arm cylinder C4, it increases the flow rate of the hydraulic oil supplied to the boom cylinder C3 and increases the speed of the boom 15. However, when performing crane work, for example, when the arm 16 is operated, if the speed of the boom 15 increases, it may be difficult to perform stable crane work. Therefore, when the crane mode is selected, the boom flow rate increasing unit Uc is not enabled. Thereby, even when the arm cylinder C4 (another hydraulic actuator AC different from the boom cylinder C3) is operated during crane work, the raising speed of the boom 15 does not change, and stable lifting work can be performed.

[0088] As will be described later, when the boom cylinder C3 is being operated by fully operating the operating member 41 (second operating tool 41B) (operating the operating member 41 to the stroke end), whether the boom cylinder C3 is being operated alone or the boom cylinder C3 and the arm cylinder C4 (another hydraulic actuator AC) are being operated in a combined operation, the flow rate of the hydraulic oil supplied to the boom cylinder C3 is the same. Therefore, the function of the function blocking unit Ud can be made to occur except during the full operation of the operating member 41.

[0089] FIG. 13 is a graph showing the relationship between the operation amount of the operation member 41 (second operating tool 41B) on the horizontal axis and the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 (the current value supplied to the proportional solenoid so2 = the pilot control pressure for pilot-operating the boom control valve V2) on the vertical axis. The third line 55 in FIG. 13 shows the case where the control unit Ua controls the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 with respect to the operation amount of the operation member 41. That is, it shows the change in the flow rate of the hydraulic oil according to the operation amount of the boom cylinder C3 when the boom cylinder C3 is operated alone.

[0090] The fourth line 56 in FIG. 13 shows the case where the boom flow rate increasing unit Uc controls the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 with respect to the operation amount of the operation member 41. That is, it shows the change in the flow rate of the hydraulic oil according to the operation amount of the boom cylinder C3 when the boom cylinder C3 and the arm cylinder C4 (other hydraulic actuator AC) are operated in combination. In FIG. 13, the flow rate of the hydraulic oil increases as it moves away from the origin of the graph. Also, the operation amount of the operation member 41 is 0 (non-operated state) at the origin of the graph, and the operation amount increases as it moves away from the origin. Therefore, the origin side of the graph is the activation side 57 of the boom control valve V2.

[0091] From the operating amount G0 where the operating amount is 0 to the operating amount G1, the hydraulic oil flow rate is 0, which is a dead zone where the boom 15 does not move even if the operating member 41 is operated. At the operating amount G1, the hydraulic oil flow rate suddenly rises to H1 or H2. In the third line 55, the hydraulic oil flow rate at the operating amount G1 is H1, and in the fourth line 56, the hydraulic oil flow rate at the operating amount G1 is H2, which is higher than H1. That is, when the arm cylinder C4 (other hydraulic actuator AC) and the boom cylinder C3 are operated in combination, the setting on the activation side 57 of the boom control valve for the hydraulic oil flow rate with respect to the operating amount of the boom cylinder C3 is set higher than when the boom cylinder C3 is operated alone.

[0092] Also, the third line 55 and the fourth line 56 are inclined upward to the right as they go from the operating amount G1 to the operating amount G2 before full operation, and the hydraulic oil flow rate converges to H3 at the operating amount G2. That is, the flow rate H2 on the activation side 57 of the fourth line 56 is higher than the flow rate H1 on the activation side of the third line 55, and the fourth line 56 has a smaller slope than the third line 55. Therefore, as the operating amount of the boom cylinder C3 increases, the difference 58 in the hydraulic oil flow rate with respect to the operating amount of the boom cylinder C3 between the combined operation and the single operation (the interval between the third line 55 and the fourth line 56) becomes smaller.

[0093] Note that at the operating amount G2, the hydraulic oil flow rate suddenly increases from H3 to the maximum flow rate H4, and the hydraulic oil flow rate is the maximum flow rate H4 during the operation from the operating amount G2 to the operating amount G3 (the operating amount when the operating member 41 is fully operated). In the second embodiment, the third line 55 and the fourth line 56 are characteristic lines in the intermediate operation range from the operating amount G1 to the operating amount G2. The third line 55 and the fourth line 56 may be characteristic lines from the operating amount G1 to the operating amount G3. In this case, the positions of the ends of the third line 55 and the fourth line 56 are at the position of the maximum flow rate H4.

[0094] In Fig. 13, 61 indicates the change amount of the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 with respect to the change in the operation amount of the boom cylinder C3 when the boom cylinder C3 is operated alone. In Fig. 13, 62 indicates the change amount of the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 with respect to the change in the operation amount of the boom cylinder C3 when the arm cylinder C4 (other hydraulic actuator AC) and the boom cylinder C3 are operated in combination.

[0095] As can be seen from Fig. 13, the change amount 62 is smaller than the change amount 61. That is, when the control device U1 operates the arm cylinder C4 (other hydraulic actuator AC) and the boom cylinder C3 in combination, compared with when the boom cylinder C3 is operated alone, the change amount 62 of the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 with respect to the change in the operation amount of the boom cylinder C3 is made smaller.

[0096] In the second embodiment, the boom flow rate increasing section Uc, when the arm cylinder C4 (other hydraulic actuator AC) and the boom cylinder C3 are operated in combination, sets the setting at the activation side 57 of the boom control valve V2 for the hydraulic oil flow rate with respect to the operation amount of the boom cylinder C3 higher than when the boom cylinder C3 is operated alone, and as the operation amount of the boom cylinder C3 increases, the difference 58 in the hydraulic oil flow rate with respect to the change in the operation amount of the boom cylinder C3 between the combined operation case and the single operation case is made smaller, thereby making the change amount 62 smaller than the change amount 61.

[0097] As can be seen from the third line 55 and the fourth line 56 in FIG. 13, when the boom cylinder C3 (boom control valve V2) is operated alone and when the arm cylinder C4 (arm control valve V7) and the boom cylinder C3 (boom control valve V2) are operated in combination, when the operation amount of the operation member 41 (second operating tool 41B) is the same operation amount, compared with the case where the boom cylinder C3 (boom control valve V2) is operated alone, when the arm cylinder C4 (arm control valve V7) and the boom cylinder C3 (boom control valve V2) are operated in combination, the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 is larger. That is, when the arm cylinder C4 (arm control valve V7) and the boom cylinder C3 (boom control valve V2) are operated in combination, the supply flow rate of the hydraulic oil to the boom cylinder C3 with respect to the operation amount of the operation member 41 (second operating tool 41B) increases.

[0098] That is, the boom flow rate increasing section Uc causes the boom control valve V2 to supply the boom cylinder C3 with hydraulic oil having a flow rate larger than the flow rate of the hydraulic oil controlled by the control section Ua for the same operation amount of the operation member 41. Therefore, the boom flow rate increasing section Uc increases the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 when the boom cylinder C3 (boom control valve V2) is operated while operating the arm cylinder C4 (arm control valve V7). In other words, the boom flow rate increasing section Uc causes the boom control valve V2 to supply the boom cylinder C3 with hydraulic oil having a flow rate larger than the flow rate of the hydraulic oil controlled by the control section Ua according to the operation amount with respect to the operation amount of the operation member 41 (second operating tool 41B).

[0099] In the second embodiment, the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 is increased by increasing the pilot control pressure controlled by the control signal transmitted from the control device U1 to the boom control valve V2. In other words, by increasing the current value supplied by the control device U1 to the boom control valve V2, the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 is increased.

[0100] In the second embodiment, when operating the boom 15 while operating the arm 16, the pilot control pressure is increased compared to the case of operating the boom 15 alone, and the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 is increased, so that the raising speed of the boom 15 increases, the operation of the boom 15 can be performed stably, and the tip claw portion 17a of the bucket 17 can easily move horizontally. Thereby, when raising the boom 15 while swinging the arm 16 in the arm cloud direction D1, or when lowering the boom 15 while swinging the arm 16 in the arm dump direction D2, the operation of the boom 15 can be easily performed.

[0101] In the second embodiment, for example, when the operation amount for the boom cylinder C3 and the operation amount for the arm cylinder C4 are the same operation amount and the speed of the arm 16 is faster than the speed of the boom 15, and when performing horizontal pulling work, by increasing the speed of the boom 15, the movement of the boom 15 and the arm 16 can be coordinated, and the horizontal pulling work can be performed well. Specifically, when the speed of the arm 16 is set to be fast in order to increase the working ability, when performing horizontal pulling work, there is a possibility that the claw portion 17a at the tip of the bucket 17 bites into the ground (the claw portion 17a drops) when the boom 15 and the arm 16 are started. In such a case, by increasing the speed of the boom 15, the movement of the boom 15 and the arm 16 can be coordinated, and the horizontal pulling work can be performed well.

[0102] In the above-described first embodiment, for example, it is effective when the operation amount for the boom cylinder C3 and the operation amount for the arm cylinder C4 are the same operation amount and the speed of the arm 16 is slower than the speed of the boom 15, and when performing horizontal pulling work. In the second embodiment, for example, it is effective when the operation amount for the boom cylinder C3 and the operation amount for the arm cylinder C4 are the same operation amount and the speed of the arm is faster than the speed of the boom 15, and when performing horizontal pulling work.

[0103] Even in the second embodiment, when a hydraulic actuator AC other than the boom cylinder C3, which is a hydraulic actuator AC other than the arm cylinder C4, and the boom cylinder C3 are being operated in combination, the configuration may be such that the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 is increased. That is, the boom flow rate increasing section Uc controls the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 when the boom cylinder C3 and another hydraulic actuator AC different from the boom cylinder C3 are being operated in combination.

[0104] Also, even when the boom cylinder C3 and another hydraulic actuator AC other than the arm cylinder C4 are being operated in combination, it is possible to achieve harmonious movement between the boom 15 and the member driven by the other hydraulic actuator AC. Note that the control device U1 is provided with a boom flow rate suppressing section Ub and a boom flow rate increasing section Uc, and can be switched between a case where the boom flow rate suppressing section Ub functions without the boom flow rate increasing section Uc functioning according to the work machine 1 to be mounted, and a case where the boom flow rate increasing section Uc functions without the boom flow rate suppressing section Ub functioning.

[0105] Also, even in the second embodiment, as shown in FIG. 10, each control valve V1 to V10 may be configured by a pilot operation switching valve, and a pair of proportional solenoid valves V21, V22 controlled by the control device U1 may be provided, such that a pilot control pressure is supplied from one proportional solenoid valve V21 to one pilot pressure receiving section Va1 and a pilot control pressure is supplied from the other proportional solenoid valve V22 to the other pilot pressure receiving section Va2. Also, as shown in FIG. 11, each control valve V1 to V10 may be configured by a proportional electromagnetic type direction and flow rate control valve that directly drives the spool with a proportional solenoid so11 supplied with current from the control device U1.

[0106] The above-described working machine 1 includes a machine body 2, a boom 15 supported by the machine body 2 so as to be vertically swingable, a boom cylinder C3 that vertically swings the boom 15, a boom control valve V2 that controls the boom cylinder C3, a control device U1 that controls the boom control valve V2, and another hydraulic actuator AC different from the boom cylinder C3. When the control device U1 performs a composite operation of the other hydraulic actuator AC and the boom cylinder C3, the control device U1 reduces the change amounts 53 and 62 of the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 with respect to the change in the operation amount of the boom cylinder C3 as compared with when the boom cylinder C3 is operated alone.

[0107] According to this configuration, when the other hydraulic actuator AC and the boom cylinder C3 are operated in a composite manner, the movements of the boom 15 and the member driven by the other hydraulic actuator AC can be coordinated. Further, the control device U1 has a boom flow rate suppression unit Ub that reduces the change amounts 53 and 62 by reducing the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 when the boom cylinder C3 is operated while the other hydraulic actuator AC is being operated.

[0108] According to this configuration, when the boom cylinder C3 is operated while the other hydraulic actuator AC different from the boom cylinder C3 is being operated, the boom characteristics become gentle and the machine body 2 can be stabilized by reducing the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3. Further, the boom control valve V2 is pilot-operated by a pilot control pressure controlled by a control signal transmitted from the control device U1, and the boom flow rate suppression unit Ub reduces the pilot control pressure when the boom cylinder C3 is operated while the other hydraulic actuator AC is being operated.

[0109] According to this configuration, the flow rate control of the boom control valve V2 can be easily performed. Further, the boom control valve V2 is controlled according to the current value supplied by the control device U1, and the boom flow rate suppression unit Ub reduces the current value supplied to the boom control valve V2 when the boom cylinder C3 is operated while operating other hydraulic actuators AC. With this configuration as well, the flow rate control of the boom control valve V2 can be easily performed.

[0110] In addition, on the tip side of the boom 15, an arm 16 swingably connected in the arm cloud direction D1, which is the direction approaching the boom 15, and the arm dump direction D2, which is the direction away from the boom 15, and an arm cylinder C4 for swinging the arm 16 are provided. The other hydraulic actuator AC is the arm cylinder C4, and the boom flow rate suppression unit Ub reduces the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 when the boom cylinder C3 is operated while operating the arm cylinder C4.

[0111] According to this configuration, when the boom 15 and the arm 16 are operated in combination, the boom characteristics become gentle, the airframe 2 can be stabilized, and the speed of the arm 16 can be ensured. In addition, the boom flow rate suppression unit Ub reduces the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 when the boom 15 is raised while swinging the arm 16 in the arm cloud direction D1, or when the boom 15 is lowered while swinging the arm 16 in the arm dump direction D2.

[0112] With this configuration as well, when the boom 15 and the arm 16 are operated in combination, the boom characteristics become gentle, the airframe 2 can be stabilized, and the speed of the arm 16 can be ensured. Furthermore, it includes an operating member 41 for operating the boom cylinder C3, and the control device U1 has a control unit Ua that controls the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 according to the operation amount of the operating member 41 when the boom cylinder C3 is operated alone. The boom flow rate suppression unit Ub causes the boom control valve V2 to supply the boom cylinder C3 with hydraulic oil at a flow rate smaller than the flow rate of the hydraulic oil controlled by the control unit Ua according to the operation amount of the operating member 41, with respect to the operation amount of the operating member 41.

[0113] With this configuration as well, the boom characteristics become gentle, and the airframe 2 can be stabilized. In addition, when the control device U1 performs a combined operation of the other hydraulic actuator AC and the boom cylinder C3, compared to when the boom cylinder C3 is operated alone, the setting at the activation side 57 of the boom control valve V2 for the hydraulic oil flow rate with respect to the operation amount of the boom cylinder C3 is set higher, and as the operation amount of the boom cylinder C3 increases, the difference 58 in the hydraulic oil flow rate with respect to the operation amount of the boom cylinder C3 between the combined operation case and the single operation case is reduced, thereby reducing the change amounts 53 and 62. The control device U1 has a boom flow rate increment unit Uc.

[0114] According to this configuration, when the other hydraulic actuator AC and the boom cylinder C3 are operated in combination, the movement between the boom 15 and the member driven by the other hydraulic actuator AC can be coordinated. In addition, the boom control valve V2 is pilot-operated by a pilot control pressure controlled by a control signal transmitted from the control device U1, and the boom flow rate increment unit Uc increases the pilot control pressure when the other hydraulic actuator AC and the boom cylinder C3 are operated in combination.

[0115] According to this configuration, the flow rate control of the boom control valve V2 can be easily performed. In addition, the boom control valve V2 is controlled according to the current value supplied by the control device U1, and the boom flow rate increment unit Uc increases the current value supplied to the boom control valve V2 when the other hydraulic actuator AC and the boom cylinder C3 are operated in combination. With this configuration, the flow rate control of the boom control valve V2 can also be easily performed.

[0116] Further, on the tip side of the boom 15, an arm 16 is swingably connected in the arm cloud direction D1, which is the direction approaching the boom 15, and the arm dump direction D2, which is the direction moving away from the boom 15. An arm cylinder C4 for swinging the arm 16 is provided. The other hydraulic actuator AC is the arm cylinder C4. The boom flow rate increasing section Uc increases the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 when the boom cylinder C3 is operated while operating the arm cylinder C4.

[0117] According to this configuration, when the boom 15 and the arm 16 are operated in combination, the movements of the boom 15 and the arm 16 can be coordinated. Further, the boom flow rate increasing section Uc increases the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 when the boom 15 is raised while swinging the arm 16 in the arm cloud direction D1, or when the boom 15 is lowered while swinging the arm 16 in the arm dump direction D2. According to this configuration, for example, when performing a horizontal pulling operation by operating the boom 15 and the arm 16 in combination, the movements of the boom 15 and the arm 16 can be coordinated.

[0118] An operating member 41 for operating the boom cylinder C3 is provided. The control device U1 has a control section Ua that controls the flow rate of the hydraulic oil supplied from the boom control valve V2 to the boom cylinder C3 according to the operation amount of the operating member 41 when the boom cylinder C3 is operated alone. The boom flow rate increasing section Uc causes the boom control valve V2 to supply hydraulic oil at a flow rate higher than the flow rate of the hydraulic oil controlled by the control section Ua according to the operation amount to the boom cylinder C3 with respect to the operation amount of the operating member 41.

[0119] With this configuration as well, the movements of the boom 15 and the arm 16 can be coordinated. Also, when the control device U1 operates the boom cylinder C3 alone in the direction of raising the boom 15, if it operates another hydraulic actuator AC, the boom flow rate increment unit Uc does not function. According to this configuration, for example, stable lifting work can be performed.

[0120] Moreover, it includes a variable displacement pump 21 that discharges hydraulic oil for operating a plurality of hydraulic actuators MT, ML, MR, C1 to C6 including the boom cylinder C3 and other hydraulic actuators AC, and a load sensing system that controls the pump 21 so as to make the differential pressure obtained by subtracting the maximum load pressure among the plurality of hydraulic actuators MT, ML, MR, C1 to C6 from the discharge pressure of the pump 21 a constant pressure.

[0121] According to this configuration, since it is equipped with a load sensing system, the intermediate flow rate characteristics are stable, so stable movement can be achieved even if the flow rate of the hydraulic oil is decreased or increased. As described above, although one embodiment of the present invention has been described, the disclosed embodiments should be considered illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and it is intended that all modifications within the meaning and scope equivalent to the claims be included.

Explanation of Reference Numerals

[0122] 2 Airframe 15 Boom 16 Arm 21 Pump 41 Operating Member 57 Starting Side 58 Difference 53 Change Amount 62 Change Amount AC Other Hydraulic Actuator C3 Boom Cylinder C4 Arm Cylinder D1 Arm Crowd Direction D2 Arm Dump Direction U1 Control Device Ua control unit Ub boom flow rate suppression unit Uc boom flow rate increment unit V2 boom control valve

Claims

1. A machine body, a boom supported by the machine body so as to be vertically swingable, a boom cylinder for vertically swinging the boom, an operating member for operating the boom cylinder, a boom control valve for changing the flow rate of the hydraulic oil supplied to the boom cylinder, a control device for controlling the operation of the boom control valve according to the operation amount of the operating member, an arm swingably connected to the tip side of the boom in a direction approaching the boom (arm crowd direction) and a direction away from the boom (arm dump direction), an arm cylinder for swinging the arm, a bucket swingably connected to the tip side of the arm, comprising: The control device: When the boom cylinder is operated alone without driving the arm cylinder, the flow rate of the hydraulic oil supplied from the boom control valve to the boom cylinder is controlled by proportionally controlling the operation of the boom control valve according to the operation amount of the operating member, Furthermore, when performing a combined operation of raising the boom while swinging the arm in the arm crowd direction or lowering the boom while swinging the arm in the arm dump direction in order to level the ground by horizontally moving the bucket, the boom flow rate suppression unit reduces the flow rate of the hydraulic oil supplied from the boom control valve to the boom cylinder compared to the case where the boom cylinder is operated alone with the same operation amount of the operating member for the boom cylinder in the case of the combined operation. A working machine having such a boom flow rate suppression unit.

2. The boom control valve is pilot-operated by a pilot control pressure controlled by a control signal transmitted from the control device, The boom flow rate suppression unit reduces the pilot control pressure compared to the case where the boom cylinder is operated alone with the same operation amount of the operating member for the boom cylinder in the case of a combined operation of operating the boom cylinder while operating the arm cylinder. The working machine according to Claim 1.

3. The boom control valve is controlled according to the current value supplied by the control device, When the boom flow rate suppression unit operates the boom cylinder during the operation of the arm cylinder for a combined operation, the current value supplied to the boom control valve is lower than when the boom cylinder is operated alone with the same operation amount as the operation amount of the operating member for the boom cylinder in the case of the combined operation. The working machine according to claim 1 or 2.

4. The control device has a control unit that controls the flow rate of the hydraulic oil supplied from the boom control valve to the boom cylinder according to the operation amount of the operating member when the boom cylinder is operated alone. The boom flow rate suppression unit causes the boom control valve to supply hydraulic oil having a flow rate smaller than the flow rate of the hydraulic oil controlled by the control unit according to the operation amount to the boom cylinder with respect to the operation amount of the operating member. The working machine according to any one of claims 1 to 3.

5. A variable displacement pump that discharges hydraulic oil for operating a plurality of hydraulic actuators including the boom cylinder and the arm cylinder. A load sensing system that controls the pump so that a differential pressure obtained by subtracting the maximum load pressure among the plurality of hydraulic actuators from the discharge pressure of the pump is a constant pressure. The working machine according to any one of claims 1 to 4.

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