Hydraulic system for working machine

A hydraulic system includes a control device to reduce a first movement speed to be lower than a second movement speed, the first movement speed being a speed at which a spool of a first control valve moves from a first supply position to a first stop position under a state where a second control valve is in the second supply position, the second movement speed being a speed at which the spool moves from the first supply position to the first stop position under a state where the second control valve is in the second stop position. The first supply position allows operation fluid to be supplied to a hydraulic actuator. The first stop position prevents the operation fluid from being supplied to the hydraulic actuator. The second stop position prevents the operation fluid from being supplied to a first fluid tube coupling a hydraulic pump to the hydraulic actuator.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2018-150738, filed Aug. 9, 2018. The content of this application is incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a hydraulic system for a working machine and a hydraulic control method for the working machine such as a skid steer loader, a compact truck loader, and a backhoe, for example.

Description of Related Art

Japanese Unexamined Patent Application Publication No. 2009-293631 is previously known as a technique for increasing the flow rate of operation fluid to be supplied to a hydraulic actuator in a working machine. The hydraulic system for the working machine includes a main pump configured to supply the operation fluid to the hydraulic actuator, a sub pump configured to increase the flow rate of the operation fluid to be supplied to the hydraulic actuator, a control valve configured to control the flow rate of the operation fluid to be supplied from the main pump to the hydraulic actuator, an increment fluid tube configured to supply the operation fluid to the operation fluid flow tube supplying the operation fluid from the control valve to the hydraulic actuator, the operation fluid being outputted from the sub pump, and a high flow valve provided in the increment fluid tube and configured to control the flow rate of the operation fluid to be supplied to the operation fluid flow tube, the operation fluid being outputted from the sub pump.

SUMMARY OF THE INVENTION

A hydraulic system for a working machine according to one aspect of the present invention, includes a first hydraulic pump to output an operation fluid, the first hydraulic pump being constituted of a constant displacement pump, a second hydraulic pump to output the operation fluid, the second hydraulic pump being constituted of a constant displacement pump, a hydraulic actuator, a first fluid tube coupling the first hydraulic pump to the hydraulic actuator, and a first control valve including a spool, the spool having a first supply position allowing the operation fluid to be supplied to the hydraulic actuator, the operation fluid being outputted from the first hydraulic pump to the first fluid tube and a first stop position preventing the operation fluid from being supplied to the hydraulic actuator, the operation fluid being outputted to the first fluid tube. The spool is configured to be moved between the first supply position and the first stop position and thereby to change a flow rate of the operation fluid to be supplied to the first fluid tube. The hydraulic system includes a second fluid tube coupling the second hydraulic pump to the first fluid tube, a second control valve having a second supply position allowing the operation fluid to be supplied to the first fluid tube, the operation fluid being outputted from the second hydraulic pump to the second fluid tube, and a second stop position preventing the operation fluid from being supplied to the first fluid tube actuator, the operation fluid being outputted to the second fluid tube, the second control valve being configured to be switched between the second supply position and the second stop position, The hydraulic system further includes a control device to reduce a first movement speed to be lower than a second movement speed, the first movement speed being a speed at which the spool moves from the first supply position to the first stop position under a state where the second control valve is in the second supply position, the second movement speed being a speed at which the spool moves from the first supply position to the first stop position under a state where the second control valve is in the second stop position.

A hydraulic control method for a working machine according to one aspect of the present invention, configured to control a hydraulic system including a first hydraulic pump to output an operation fluid, the first hydraulic pump being constituted of a constant displacement pump, a second hydraulic pump to output the operation fluid, the second hydraulic pump being constituted of a constant displacement pump, a hydraulic actuator, a first fluid tube coupling the first hydraulic pump to the hydraulic actuator, a first control valve including a spool. The spool has a first supply position allowing the operation fluid to be supplied to the hydraulic actuator, the operation fluid being outputted from the first hydraulic pump to the first fluid tube, and a first stop position preventing the operation fluid from being supplied to the hydraulic actuator, the operation fluid being outputted to the first fluid tube, the spool being configured to be moved between the first supply position and the first stop position and thereby to change a flow rate of the operation fluid to be supplied to the first fluid tube. The hydraulic system includes a second fluid tube coupling the second hydraulic pump to the first fluid tube, a second control valve having a second supply position allowing the operation fluid to be supplied to the first fluid tube, the operation fluid being outputted from the second hydraulic pump to the second fluid tube, and a second stop position preventing the operation fluid from being supplied to the first fluid tube actuator, the operation fluid being outputted to the second fluid tube, the second control valve being configured to be switched between the second supply position and the second stop position; and a control device. The hydraulic control method includes steps of judging whether the second control valve is in the second supply position, judging whether a request to move the spool from the first supply position to the first stop position has been issued, and reducing a first movement speed to be lower than a second movement speed when control device determines that the second control valve is in the second supply position and that the request has been issued, the first movement speed being a speed at which the spool moves from the first supply position to the first stop position under a state where the second control valve is in the second supply position, the second movement speed being a speed at which the spool moves from the first supply position to the first stop position under a state where the second control valve is in the second stop position.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described below with reference to the drawings as appropriate.

An embodiment of a hydraulic system for a working machine and the working machine having the hydraulic system according to the present invention will be described below with reference to the drawings.

FIG. 5shows a side view of a working machine according to an embodiment of the present invention. InFIG. 5, a skid steer loader is shown as an example of the working machine. However, the working machine according to the present invention is not limited to the skid steer loader, and may be, for example, another type of loader working machine such as a compact track loader. In addition, a working machine other than the loader working machine may be employed.

As shown inFIG. 5, the working machine1includes a machine body2, a cabin3, a working device4, and a traveling device5.

In the embodiment of the present invention, the front side (the left side inFIG. 5) of the operator seated on the operator seat8of the working machine1is referred to as the front, the rear side (the right side inFIG. 5) of the operator is referred to as the rear, the left side of the operator is referred to as the left, and the right side of the operator is referred to as the right.

Moreover in the explanation of the embodiment, the horizontal direction which is a direction orthogonal to the front-rear direction is referred to as a machine width direction. The direction extending from the central portion of the machine body2to the right portion or the left portion will be described as a machine outward direction.

In other words, the machine outward direction corresponds to the machine width direction and is the direction separating away from the machine body2. A direction opposite to the machine outward direction will be described as a machine inward direction. In other words, the machine inward direction corresponds to the machine width direction and is the direction approaching the machine body2.

The cabin3is mounted on the machine body2. The cabin3is provided with an operator seat8. The working device4is attached to the machine body2. The traveling device5is provided on the outside of the machine body2. A prime mover32is mounted at the rear portion of the machine body2. The prime mover32is constituted of an electric motor, an engine, and the like. In the embodiment, the prime mover32is constituted of the engine.

The working device4includes a boom10, a working tool11, a lift link12, a control link13, a boom cylinder14, and a bucket cylinder15.

The boom10is provided on the right side of the cabin3, and another boom10is provided on the left side of the cabin3. The booms10is configured to be swung upward and downward. The working tool11, for example, is a bucket, and the bucket11is provided at the tip end portions (the front end portions) of the booms10so as to be swung upward and downward. The lift link12and the control link13support the base portion (the rear portion) of each of the booms10so that the boom10can be swung upward and downward.

The boom cylinder14is stretched and shortened to move the boom10upward and downward. The bucket cylinder15is stretched and shortened to swing the bucket11.

The front portions of the left boom10and the right boom10are coupled to each other by a deformed connecting pipe. The base portions (the rear portions) of the booms10are coupled to each other by a cylindrical connecting pipe.

A pair of the lift link12, the control link13and the boom cylinder14is provided on the left side of the machine body2corresponding to the boom10arranged on the left side, and another pair of the lift link12, the control link13and the boom cylinder14is provided on the right side of the machine body2corresponding to the boom10arranged on the right side.

The lift link12is provided vertically at the rear portion of the base portion of each of the booms10. The upper portion (one end side) of the lift link12is supported rotatably about a lateral axis by a pivot shaft16(a first pivot shaft) near the rear portion of the base portion of each of the booms10.

In addition, the lower portion (the other end side) of the lift link12is supported rotatably about the horizontal axis by a pivot shaft17(a second pivot shaft) near the rear portion of the machine body2. The second pivot shaft17is provided below the first pivot shaft16.

An upper portion of the boom cylinder14is supported rotatably about the lateral axis by a pivot shaft18(a third pivot Shaft). The third pivot shaft18is provided at the base portion of each of the booms10and particularly at the front portion of the base portion.

The lower portion of the boom cylinder14is supported rotatably about the lateral axis by a pivot shaft19(a fourth pivot shaft). The fourth pivot shaft19is provided near the lower portion of the rear portion of the machine body2and below the third pivot shaft18.

The control link13is provided in front of the lift link12. One end of the control link13is supported rotatably about the lateral axis by a pivot shaft20(a fifth pivot shaft). The fifth pivot shaft20is provided at a position corresponding to the front of the lift link12in the machine body2.

The other end of the control link13is supported rotatably about the lateral axis by a pivot shaft21(a sixth pivot shaft). The sixth pivot shaft21is provided in front of the second pivot shaft17and above the second pivot shaft17in the boom10.

When the boom cylinder14is stretched and shortened, each of the booms10is swung upward and downward around the first pivot shaft16while the base portion of each of the booms10is supported by the lift link12and the control link13. In this manner, the tip end portion of each of the booms10moves upward and downward.

The control link13is swung upward and downward around the fifth pivot shaft20in accordance with the upward and downward swinging of each of the booms10. The lift link12is swung backward and forward around the second pivot shaft17in accordance with the upward and downward swinging of the control link13.

Instead of the bucket11, another working tool can be attached to the front portion of the boom10, Another working tool is, for example, an attachment (an auxiliary attachment) such as a hydraulic crusher, a hydraulic breaker, an angle broom, an earth auger, a pallet fork, a sweeper, a mower, a snow blower, or the like.

A connecting member50is provided at the front portion of the boom10arranged on the left side. The connecting member50is a member to which a tube member such as a pipe is connected, the tube member being connected to the auxiliary actuator attached to the auxiliary attachment.

Each of the bucket cylinders15is respectively arranged near the front portion of each of the booms10. When the bucket cylinder15is stretched and shortened, the bucket11is swung.

In the present embodiment, wheel-type traveling devices5A and5B each having front wheels5F and rear wheels5R are adopted as the traveling device5arranged on the right and the traveling devices5arranged on the left. The traveling devices may employ crawler type traveling devices (including semi-crawler type traveling devices) for the traveling devices5A and5B.

As shown inFIG. 1, the hydraulic system for the working machine includes a first hydraulic pump P1, a second hydraulic pump P2, and a third hydraulic pump P3.

The first hydraulic pump P1, the second hydraulic pump P2, and the third hydraulic pump P3are pumps to be driven by the power of the prime mover32, and are constituted of the constant displacement gear pumps (also referred to as the fixed displacement gear pumps). The first hydraulic pump P1is configured to output the operation fluid stored in the operation fluid tank22.

The first hydraulic pump P1outputs the operation fluid mainly used for operating a hydraulic actuator. A first fluid tube40is provided at an outlet port (an output port) for outputting the operation fluid in the first hydraulic pump P1.

The second hydraulic pump P2is also a pump configured to output the operation fluid stored in the operation fluid tank22and to increase the operation fluid to the hydraulic actuator. A second fluid tube41is provided at an outlet port (an output port) for outputting the operation fluid in the second hydraulic pump P2.

The third hydraulic pump P3is also configured to output the operation fluid stored in the operation fluid tank22. A third fluid tube43is provided at an outlet port (an output port) for outputting the operation fluid in the third hydraulic pump P3.

In particular, the third hydraulic pump P3outputs the operation fluid mainly used for control. For convenience of the explanation, the operation fluid outputted from the third hydraulic pump P3is referred to as a pilot fluid, and the pressure of the pilot fluid is referred to as a pilot pressure.

A boom control valve56A, a bucket control valve (a working tool control valve)56B, and an auxiliary control valve56C are arranged on the first fluid tube40. The boom control valve56A is a valve configured to control a hydraulic cylinder (a boom cylinder)14that controls the boom. The bucket control valve56B is a valve configured to control a hydraulic cylinder (a bucket cylinder)15that controls the bucket.

The auxiliary control valve56C is a valve for controlling an auxiliary actuator (a hydraulic cylinder, a hydraulic motor) mounted on an auxiliary attachment such as a hydraulic crusher, a hydraulic breaker, an angle broom, an earth auger, a pallet fork, a sweeper, a mower, a snow blower, or the like.

The boom control valve56A and the bucket control valve56B each are direct-acting spool three-position switching valves actuated by the pilot fluid. The boom control valve56A and the bucket control valve56B are configured to be switched by the pilot pressure between a neutral position, a first position different from the neutral position, and a second position different from the neutral position and the first position.

The boom cylinder14is coupled to the boom control valve56A by a fluid tube, and the bucket cylinder15is coupled to the bucket control valve56B by a fluid tube.

The boom10and the bucket11can be operated by an operation lever58arranged around the operator seat8. The operating lever58is supported so as to be tilted from the neutral position in the front-rear direction (the longitudinal direction), the left-right direction (the lateral direction), and the diagonal directions (directions between the longitudinal direction and the lateral).

When the operating lever58is tilted, it is possible to operate a plurality of pilot valves (the operation valves)59A,59B,59C, and59D provided at the lower portion of the operating lever58.

The pilot valves59A,59B,59C, and59D is coupled to the third hydraulic pump P3by a third fluid tube43.

The plurality of pilot valves (operation valves)59A,59B,59C, and59D are respectively coupled to the boom control valve56A and the bucket control valve (the working tool control valve)56B by a plurality of fluid tubes45a,45b,45c, and45d.

In particular, the pilot valve59A is coupled to the boom control valve56A by the fluid tube45a. The pilot valve59B is coupled to the boom control valve56A by the fluid tube45b.

The pilot valve59C is coupled to the bucket control valve56B by the fluid tube45c. The pilot valve59D is coupled to the bucket control valve56B by the fluid tube45d.

The pilot valves (operation valves)59A,59B,59C, and59D are respectively configured to determine an output pressure of the operation fluid to be outputted in accordance with the operation of the operation lever58.

In particular, when the operation lever58is tilted forward, the pilot valve (operation valve)59A for downward movement is operated to determine the pilot pressure of the pilot fluid to be outputted from the lowering pilot valve59A for downward movement.

The pilot pressure is applied to the pressure receiving portion of the boom control valve56A, then the boom cylinder14is shortened, and thereby the boom10is moved downward.

When the operation lever58is tilted backward, the pilot valve (operation valve)59B for upward movement is operated to determine the pilot pressure of the pilot fluid to be outputted from the pilot valve59B for upward movement.

The pilot pressure is applied to the pressure receiving portion of the boom control valve56A, then the boom cylinder14is stretched, and thereby the boom10is moved upward.

When the operation lever58is tilted rightward, the pilot valve (operation valve)59C for bucket dumping movement is operated to determine the pilot pressure of the pilot fluid to be outputted from the pilot valve59C.

The pilot pressure is applied to the pressure receiving portion of the boom control valve56B, then the bucket cylinder15is stretched, and thereby the bucket11performs the dumping operation.

When the operation lever58is tilted leftward, the pilot valve (operation valve)59D for bucket shoveling movement is operated to determine the pilot pressure of the pilot fluid to be outputted from the pilot valve59D.

The pilot pressure is applied to the pressure receiving portion of the boom control valve56B, then the bucket cylinder15is shortened, and thereby the bucket11performs the shoveling operation.

The hydraulic system for the working machine is provided with a first control valve configured to control the flow rate of the operation fluid to be supplied from the first fluid tube40to the hydraulic actuator.

In the embodiment, the first control valve is an auxiliary control valve56C, and the hydraulic actuator is an auxiliary actuator. Hereinafter, the description will be made assuming that the first control valve is the auxiliary control valve56C.

The first fluid tube40includes a first section40acoupling the first hydraulic pump P1to the auxiliary control valve56C, and at least two second sections40band40cconnected to the auxiliary control valve56C.

The auxiliary control valve56C includes an input port (a first input port)70, an input port (a second input port)100, an output port71, a tank port (a first tank port)72, and a tank port (a second tank port)101.

The input port70is a port to Which the first section40aof the first fluid tube40is connected and to which the operation fluid outputted from the first hydraulic pump P1is supplied. Similarly to the input port70, the input port100is a port to which the first section40aof the first fluid tube40is connected and to which the operation fluid outputted from the first hydraulic pump P1is supplied, and the input port100is different from the input port70.

The output port71is a port to which the second sections40band40cof the first fluid tube40are connected, and the output port71is configured to supply the operation fluid to the auxiliary actuator. The tank port72is a port for discharging the operation fluid, and is a port for discharging the operation fluid that has returned from the auxiliary actuator to the auxiliary control valve56C.

A discharge fluid tube54is connected to the tank port72b. The discharge fluid tube54is connected to the operation fluid tank22, and is configured to discharge, to the operation fluid tank22, the operation fluid that is discharged at least from the tank port72of the auxiliary control valve56C.

The tank port101is a port for discharging the operation fluid, and is a port for discharging at least a part of the operation fluid introduced from the input port100to the auxiliary control valve56C. The tank port101is connected to the discharge fluid tube54.

In addition, the auxiliary control valve56C is a switching valve having a spool, and is, for example, a direct-acting spool three-position switching valve configured to be activated by the pilot fluid. The spool of the auxiliary control valve56C has a first supply positions62aand63band a first stop position (a neutral position)62cand is configured to be switched between the first supply positions62aand63band the first stop position62c. The first supply positions62aand62ballow the operation fluid to be supplied to the auxiliary actuator. The first stop position62cstops supplying the operation fluid to the auxiliary actuator.

The spool of the auxiliary control valve56C is moved to either one of the first supply positions62aand62b, and thereby the moving of the spool changes the flow rate of the operation fluid to be outputted from the output port71of the first fluid tube40of the auxiliary control valve56C.

Pilot fluid tubes86aand86bare respectively connected to the pressure receiving portions61aand61bof the auxiliary control valve56C. Proportional valves (a first proportional valve60A and a second proportional valve60B) are respectively connected to the pilot fluid tubes86aand86b.

The proportional valves (the first proportional valve60A and the second proportional valve60B) are electromagnetic valves configured to be magnetized to change the pilot pressure applied to the pressure receiving portions61aand61bof the auxiliary control valve56C. The third fluid tube43is connected to the first proportional valve60A and the second proportional valve60B. The pilot fluid is supplied from the third hydraulic pump P3to the first proportional valve60A and the second proportional valve60B.

The first proportional valve60A and the second proportional valve60B change the pilot pressure applied to the pressure receiving portions61aand61bof the auxiliary control valve56C. In this manner, the spool of the auxiliary control valve56C is moved in an arbitrary direction.

For example, when the first proportional valve60A is opened, the pilot fluid is applied to the pressure receiving portion61aof the auxiliary control valve56C through the pilot fluid tube86a, and then the pilot pressure to be applied to (given to) the pressure receiving portion61ais determined depending on the opening aperture of the first proportional valve60A.

When the pilot pressure applied to the pressure receiving portion61areaches a pressure equal to or higher than a predetermined pressure, the spool of the auxiliary control valve56C moves from the first stop position62cto the first supply position62aside.

In addition, when the second proportional valve60B is opened, the pilot fluid is applied to the pressure receiving portion61bof the auxiliary control valve56C through the pilot fluid tube86b, and then the pilot pressure to be applied to (given to) the pressure receiving portion61bis determined depending on the opening aperture of the second proportional valve60B.

When the pilot pressure applied to the pressure receiving portion61breaches a pressure equal to or higher than a predetermined pressure, the spool of the auxiliary control valve56C moves from the first stop position62cto the first supply position62bside.

The control device90controls magnetization and the like of the proportional valves60(the first proportional valve60A and the second proportional valve60B). The control device90is constituted of a CPU and the like. An operation member93is connected to the control device90. An operation extent (for example, a slide amount, a swing amount, and the like) of the operation member93is inputted to the control device90.

The operation member93is constituted of, for example, a seesaw switch configured to be swung, a slide switch configured to be slid, or a push switch configured to be pushed. When the operation member93is operated in one direction, an operation extent (a first operation extent) in one direction is inputted to the control device90, and then the control device90changes the opening aperture of the first proportional valve60A in accordance with the first operation extent.

Meanwhile, when the first operation extent is the maximum, the opening aperture of the first proportional valve60A is the maximum. And, when the first operation extent is the minimum, the opening aperture of the first proportional valve60A is the minimum. That is, the first operation extent and the opening aperture of the first proportional valve60A are in a substantially proportional relationship each other.

In addition, when the operation member93is operated in the other direction, the operation extent (a second operation extent) in the other direction is inputted to the control device90, and then the control device90changes the opening aperture of the second proportional valve60B in accordance with the second operation extent.

When the second operation extent is the maximum, the opening aperture of the second proportional valve60B is the maximum, And, when the second operation extent is the minimum, the opening aperture of the second proportional valve60B is the minimum. That is, the second operation extent and the opening aperture of the second proportional valve60B are in a substantially proportional relationship each other.

As described above, according to the hydraulic system for the working machine, the spool of the auxiliary control valve56C is moved by the operation of the proportional valves60(the first proportional valve60A and the second proportional valve60B), and thereby the flow rate of the operation fluid to be supplied to the auxiliary actuator is changed.

Now, in the hydraulic system for the working machine, the operation fluid to be supplied to the auxiliary actuator can be increased. That is, the operation fluid outputted from the first hydraulic pump P1and the operation fluid outputted from the second hydraulic pump P2can be supplied together to the auxiliary actuator.

The hydraulic system for the working machine includes a second control valve (a high flow valve)65and a switching valve (a high flow switching valve)66. The high flow valve65is arranged in the middle portion of the second fluid tube41that couples the first hydraulic pump P1to the first fluid tube. The high flow valve65is a valve configured to determine the flow rate of the operation fluid flowing in the second fluid tube41.

The end portion of the second fluid tube41is connected to the second section40bof the first fluid tube40. In addition, a check valve47is provided in a section between the high flow valve65and the coupling portion (a coupling portion between the first fluid tube40and the second fluid tube41)44. The check valve47is configured to allow the operation fluid to flow toward the coupling portion44and to prevent the operation fluid from flowing toward the high flow valve65.

The high flow valve65is constituted of a two-position switching valve configured to be operated by the pilot pressure. The high flow valve65is configured to be switched between two switching positions (a second stop position65aand a second supply position65b) by the pilot pressure.

The high flow valve65is closed at the second stop position65a, and thereby the flow rate of the operation fluid flowing in the second fluid tube41is made zero. In addition, the high flow valve65is opened at the second supply position65b, and thereby the flow rate of the operation fluid flowing to the second fluid tube41is increased at a predetermined flow rate from zero.

In other words, the high flow valve65shuts off the second fluid tube41in the second stop position65a, and opens the second fluid tube41so as to be communicated in the second supply position65b.

The high flow switching valve66is a valve configured to operate the high flow valve65through the switching, and is constituted of an electromagnetic two-position switching valve. The high flow switching valve66is configured to be switched between a first position66aand a second position66b.

The high flow switching valve66is connected to the third fluid tube43. When the high flow switching valve66is in the first position66a, the pilot pressure is not applied to the pressure receiving portion65cof the high flow valve65, and thereby the high flow valve65is set to the first position66a.

When the high flow switching valve66is in the second position66b, the pilot pressure is applied to the solenoid66cof the high flow valve65, and thereby the high flow valve65is set to the second supply position65b.

The controller90conducts the switching between the first position66aand the second position66bof the high flow switching valve66. An operation member94such as a switch configured to be turned on/off is connected to the control device90. The operation member94is constituted of, for example, a seesaw switch configured to be swung, a push switch configured to be pushed, or the like.

When the operation member94is turned off, that is, when the increase mode is turned off, the controller90demagnetizes the solenoid66cof the high flow switching valve66.

When the operation member94is turned on, that is, when the increase mode is turned on, the controller90continuously magnetizes the solenoid66cof the high flow switching valve66. When the solenoid66cof the high flow switching valve66is magnetized, the high flow switching valve66is switched to the second position66b, and the pilot pressure is applied to the pressure receiving portion of the high flow valve65. In this manner, the high flow valve65is set to the second supply position65b.

As the result, the operation fluid outputted from the second hydraulic pump P2flows through the high flow valve65, and then the operation fluid flows to the coupling portion44which is the end portion of the second fluid tube41. Then, the operation fluid flowing from the second fluid tube41is confluent with the operation fluid flowing through the second section40bof the first fluid tube40at the coupling portion44, whereby the operation fluid flowing to the auxiliary actuator increases.

On the other hand, when the high flow switching valve66is set to the first position66ato stop applying the pilot pressure to the pressure receiving portion of the high flow valve65, the high flow valve65is set to the second stop position65a. As the result, the operation fluid outputted from the second hydraulic pump P2is blocked by the high flow valve65, and the operation fluid which cannot pass through the high flow valve65returns to the operation fluid tank22.

As the result, the operation fluid (the operation fluid of the second fluid tube41) outputted from the second hydraulic pump P2is not supplied to the second section40bof the first fluid tube40.

Then, the control device90changes the switching speed of the auxiliary control valve56C, that is, the movement speed of the spool in the auxiliary control valve56C in the case of the increase mode from not in the case of the increase mode.

FIG. 2shows a relation between a movement transition W1of the spool of the auxiliary control valve56C of the case where the high flow valve65is in the second supply position65b(in the increase mode) and a movement transition W2of the spool of the auxiliary control valve56C of the case where the high flow valve65is in the second stop position65a(not in the increase mode).

Prior to a time point P10inFIG. 2, the spool of the auxiliary control valve56C is moved to either one of the first supply positions62aand62bby operating the operation member93to the maximum operation extent, for example.

When the operation extent of the operation member93is reduced from the maximum to zero (when the operation of the operation member93is stopped) at the time point P10inFIG. 2, the control device90rapidly reduces, to zero, the electric currents (the electric currents for magnetization) outputted to the first proportional valve60A and the second proportional valve60B. In this manner, the spool of the auxiliary control valve56C is moved in one motion from either one of the first supply positions62aand62bto the second stop position62cas shown in the movement transition W2.

On the other hand, the control device90gradually reduces, to zero, the electric currents (the electric currents for magnetization) outputted to the first proportional valve60A and the second proportional valve60B at the time point P10in the increase mode. In this manner, the spool of the auxiliary control valve56C is gradually moved from either one of the first supply positions62aand62bto the second stop position62cas shown in the movement transition W1.

That is, assuming that a movement speed of the spool of the auxiliary control valve56C from the first supply positions62aand62bto the first stop position62cin the increase mode is referred to as a first movement speed V1and that a movement speed of the spool of the auxiliary control valve56C from the first supply positions62aand62bto the first stop position62cnot in the increase mode is referred to as a second movement speed V2, the first movement speed V1is lower than the second movement speed V2.

In particular, in the auxiliary control valve56C, the state in which the input port100and the tank port101are closed is referred to as a PT closing state (simply referred to as PT closing), and the state in which the input port100and the tank port101are communicated with each other is referred to as a PT opening state (simply referred to as PT closing). And, a state in which the output port71and the tank port72are communicated with each other is referred to as a CT opening state (simply referred to as a CT opening), and a state in which the output port71and the tank port72are closed is referred to as a CT closing state (simply referred to as a CT closing).

In that case, in the case where the spool of the auxiliary control valve56C is in the first supply position62aor in the first supply position62b, the PT closing and the CT opening are established. And, in the case where the spool of the auxiliary control valve56C is in the first stop position62c, the PT opening and the CT closing are established.

Meanwhile, when the spool of the auxiliary control valve56C is moved from the first supply positions62aand62bto the first stop position62c, the PT closing is replaced by the PT opening at a predetermined position, and the CT opening is replaced by the CT closing at the predetermined position.

In the case of the increase mode, the controller90adjusts the electric current outputted to the first proportional valve60A and the second proportional valve60B at the time point P10, and thereby the first speed transition W1afrom the position R10for the PT opening and the CT opening to the position R11for the PT opening and the CT closing is set to be slower than the second speed transition W1bfrom the position R12for the PT closing to the position R10for the PT opening and the CI opening.

That is, the spool of the auxiliary control valve56C moves in one motion from the PT closing and the CT opening to the PT opening and the CT opening at the time point P10, and then gradually moves from the PT opening and the CT opening to the PT opening and the CT closing. That is, the slope of the first speed transition W1ais made gentler than the slope of the second speed transition W1b.

Meanwhile, as shown inFIG. 2, even after the spool is positioned at the position R11where the PT opening and the CT closing are established, a speed transition (a third speed transition) W1cafter the position R11is also may be made slower than the second speed transition W1b. For example, after the third speed transition W1cfrom the position. R11fto the position (a predetermined position) R13is made slower than the second speed transition W1b, the fourth speed transition. W1dfrom the predetermined position R13to PT opening and CT closing (first stop position) is made the same as the second speed transition W1b.

FIG. 3is a view showing the operation of the control device90and the like.

As shown inFIG. 3, in the state where the operation member93is operated in one direction or in the other direction and thereby the auxiliary actuator is in operation, the control device90judges whether the high flow valve65is at the second supply position65b, that is, whether the increase mode is established (Step S1).

In addition, the control device90judges whether there is a request for moving the spool of the auxiliary control valve56C from the first supply positions62aand62bto the first stop position62c, that is, whether the operation member93is returned to the neutral position from the state where the operation member93is moved in either one of one direction and the other direction (Step S2).

In the control device90, when the high flow valve65is in the second supply position65b(Step S1, Yes) and there is a request to move the spool from the first supply positions62aand62bto the first stop position62c(Step S2, Yes), the first movement speed V1of the spool of the auxiliary control valve56C is made slower than the second movement speed V2(Step S3: a movement process).

For example, in the movement process, the controller90adjusts the electric current to be outputted to the proportional valve, and thereby sets the movement transition of the spool of the auxiliary control valve56C to the movement transition W1shown inFIG. 2.

In the case where the high flow valve65is in the second stop position65a(Step S1, No) and a request to move the spool from the first supply positions62aand62bto the first stop position62cis issued (Step S2, Yes), the control device90quickly move the spool of the auxiliary control valve56C from the first supply positions62aand62bto the first stop position62cas shown in the movement transition W2inFIG. 2.

The hydraulic system for the working machine includes the first hydraulic pump P1constituted of a constant displacement pump (also referred to as a fixed displacement pump) configured to output the operation fluid, the second hydraulic pump P2constituted of a constant displacement pump configured to output the operation fluid, the hydraulic actuator, and the first fluid tube40coupling the first hydraulic pump P1to the hydraulic actuator.

The hydraulic system includes the first control valve (the auxiliary control valve56C) that has the spool having the first supply positions62aand62ballowing the operation fluid to be supplied to the hydraulic actuator, the operation fluid being outputted from the first hydraulic pump P1to the first fluid tube40, and the first stop position62cpreventing the operation fluid from being supplied to the hydraulic actuator, the operation fluid being outputted to the first fluid tube40, and configured to move the spool to change the flow rate of the operation fluid to be supplied to the first fluid tube40. The hydraulic system includes the second fluid tube41coupling the second hydraulic pump P2to the first fluid tube40, and the second control valve (the high flow valve65) having the second supply position65ballowing the operation fluid to be supplied to the first fluid tube40, the operation fluid being outputted from the second hydraulic pump P2to the second fluid tube41, and the second stop position65apreventing the operation fluid of the second fluid tube41from being supplied to the first fluid tube40, the operation fluid being outputted to the second fluid tube41, the second control valve being configured to be switched between the second supply position65band the second stop position65a.

The hydraulic system includes the control device90to reduce the first movement speed V1to be lower than the second movement speed V2, the first movement speed V1being a speed at which the spool moves from the first supply positions62aand62bto the first stop position62cunder the state where the second control valve is in the second supply position65b, the second movement speed V2being a speed at which the spool moves from the first supply positions62aand62bto the first stop position62cunder the state where the second control valve is in the second stop position65a.

According to that configuration, in the case where the second control valve is in the second supply position65b, that is, in the increase mode, the shock generated by the switching of the first control valve (the auxiliary control valve56C) can be reduced even when the hydraulic actuator is stopped by the first control valve (the auxiliary control valve56C) from being operated (even when the first control valve is switched to the stop position).

The hydraulic system for the working machine includes the pilot fluid tubes86aand86bin which the operation fluid serving as the pilot fluid flows, and the proportional valves (the first proportional valve60A and the second proportional valve60B) connected to the pilot fluid tubes86aand86b. The first control valve has the pressure-receiving portions61aand61bconfigured to receive the pilot fluids flowing in the pilot fluid tubes86aand86b. The spool can be moved between the first supply positions62aand62band the first stop position62cby the pilot fluid supplied to the pressure-receiving portions61aand61b. The control device90changes the opening aperture of the proportional valve to reduce the first movement speed V1to be lower than the second movement speed V2.

According to that configuration, it is possible to change the opening apertures of the proportional valves (the first proportional valve60A and the second proportional valve60B), and thereby easily making the first movement speed V1of the spool lower than the second movement speed V2.

The first control valve includes the input ports70and100to which the operation fluid outputted from the first hydraulic pump P1is supplied, the input ports70and100being connected to the first fluid tube40, the output port71to supply the operation fluid to the hydraulic actuator, the output port71being connected to the first fluid tube40, and the tank ports72and101to output the operation fluid. The spool close or open the input ports70and100, the output port71and the tank ports72and101in the movement from the first supply positions62aand62bto the first stop position62c.

The state closing the input port100and the tank port101is referred to as the PT closing, the state communicating the input port100with the tank port101is referred to as the PT opening, the state communicating the output port72with the tank port72is referred to as the CT opening, and the state closing the output port72and the tank port72is referred to as the CT closing. In that case, the control device90slow the first speed transition W1aof the spool moving from a position for the PT opening and the CT opening to another position for the PT opening and the CT closing in comparison with the second speed transition W1bof the spool moving from a position for the PT closing to another position for the PT opening and the CT opening.

According to that configuration, while the flow rate of the operation fluid supplied from the first control valve is reduced in a short time by the first speed transition W1a, the shock generated by the reduction of the operation fluid can be reduced by the second speed transition W1b.

A hydraulic control method for the working machine for controlling the hydraulic system includes the control device90, and the hydraulic control method includes steps in which the control device90judges whether the second control valve is in the second supply position65b, the control device90judges whether a request to move the spool from the first supply positions62aand62bto the first stop position62chas been issued, and the control device90reduces the first movement speed V1to be lower than the second movement speed V2when the control device90determines that the second control valve is in the second supply position65band that the request has been issued.

According to that configuration, in the case where the second control valve is in the second supply position65b, that is, in the increase mode, the shock generated by the switching of the first control valve (the auxiliary control valve56C) can be reduced even when the hydraulic actuator is stopped by the first control valve (the auxiliary control valve56C) from being operated (even when the first control valve is switched to the stop position).

In the embodiment described above, the second fluid tube41for increasing the operation fluid is connected to the second section40bof the first fluid tube40. However, as shown inFIG. 4A, the second fluid tube41may be connected to the first section40aof the first fluid tube40.

In particular, as shown inFIG. 4A, the end portion of the second fluid tube41is connected between the check valve48and the input port70in the first fluid tube40. Also in that case, the second fluid tube41is provided with the check valve47.

In addition, the pressure receiving portions61aand61bof the auxiliary control valve56C are separately provided from the proportional valves (the first proportional valve60A and the second proportional valve60B). However, as shown inFIG. 4B, the pressure receiving portions61aand61bof the auxiliary control valve56C and the proportional valves (the first proportional valve60A and the second proportional valve60B) may be integrally configured.

In the above description, the embodiment of the present invention has been explained. However, all the features of the embodiment disclosed in this application should be considered just as examples, and the embodiment does not restrict the present invention accordingly. A scope of the present invention is shown not in the above-described embodiment but in claims, and is intended to include all modifications within and equivalent to a scope of the claims.