Hydraulic system for working machine

A hydraulic system for a working machine includes a hydraulic actuator having a first fluid chamber and a second fluid chamber, an accumulator, an outputting fluid tube to output an operation fluid, and a switching valve to be switched between a first position and a second position. The first position allows the first fluid chamber and the second fluid chamber to be communicated with the outputting fluid tube and thereby allowing a floating operation. The second position allows the first fluid chamber and the accumulator to be communicated with each other, allows the second fluid chamber and the outputting fluid tube to be communicated with each other, and thereby allows an anti-vibration operation.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2016-255460, filed Dec. 28, 2016. The contents of these applications are 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 such as a skid steer loader, a compact track loader, and the like.

Discussion of the Background

Japanese Unexamined Patent Application Publication No. 2007-186942 previously discloses a hydraulic system for a working machine. The working machine disclosed in Japanese Unexamined Patent Application Publication No. 2007-186942 includes a boom, a bucket, a boom cylinder configured to move the boom, a bucket cylinder configured to move the bucket, a first control valve configured to control the stretching and shortening of the boom cylinder, and a second control valve configured to control the stretching and shortening of the bucket cylinder. An operation fluid outputted from a pump is supplied to the first control valve and the second control valve.

The hydraulic system disclosed in Japanese Unexamined Patent Application Publication No. 2007-186942 is a hydraulic system configured to perform a ride control of the working machine. The ride control suppresses fluctuation of the pressure in the boom cylinder and thereby suppresses the traveling vibrations of the working machine, that is, performs an anti-vibration operation of a machine body. In addition, a hydraulic system disclosed in Japanese Unexamined Patent Application Publication No. 2010-84784 outputs an operation fluid of a boom cylinder and thereby performs a floating operation.

SUMMARY OF THE INVENTION

A hydraulic system for a working machine of the present invention, includes a hydraulic actuator having a first fluid chamber and a second fluid chamber, an accumulator, an outputting fluid tube to output an operation fluid, and a switching valve to be switched between a first position and a second position. The first position allows the first fluid chamber and the second fluid chamber to be communicated with the outputting fluid tube and thereby allowing a floating operation. The second position allows the first fluid chamber and the accumulator to be communicated with each other, allows the second fluid chamber and the outputting fluid tube to be communicated with each other, and thereby allows an anti-vibration operation.

Another hydraulic system for a working machine of the present invention, includes a hydraulic actuator having a first fluid chamber and a second fluid chamber, a first accumulator, a second accumulator, an outputting fluid tube to output an operation fluid, and a switching valve to be switched between a first position and a second position. The first position allows the first fluid chamber and the second fluid chamber to be communicated with the outputting fluid tube and thereby allows a floating operation. The second position allows the first fluid chamber and the first accumulator to be communicated with each other, allows the second fluid chamber and the second accumulator to be communicated with each other, and thereby allows an anti-vibration operation.

Further another hydraulic system for a working machine of the present invention, includes a hydraulic actuator, a float switching valve to perform a floating operation of the hydraulic actuator, an anti-vibration switching valve to perform an anti-vibration operation of the hydraulic actuator, and a control valve to stop the anti-vibration operation performed by the anti-vibration switching valve when the float switching valve performs the floating operation.

Further another hydraulic system for a working machine of the present invention, includes a hydraulic actuator, a float switching valve to perform a floating operation of the hydraulic actuator, an anti-vibration switching valve to perform an anti-vibration operation of the hydraulic actuator. The float switching valve or the anti-vibration switching valve includes a solenoid valve to which the operation fluid serving as a pilot fluid is supplied, a pressure-receiving portion to receive a pressure of the pilot fluid supplied to the solenoid valve, an inner fluid tube to connect the solenoid valve to the pressure-receiving portion, and an outputting fluid tube to output the operation fluid of the inner fluid tube.

Further another hydraulic system for a working machine of the present invention, includes a hydraulic actuator, a float switching valve to perform a floating operation of the hydraulic actuator, an anti-vibration switching valve to perform an anti-vibration operation of the hydraulic actuator. The float switching valve or the anti-vibration switching valve includes a solenoid valve to which the operation fluid serving as a pilot fluid is supplied, a pressure-receiving portion to receive a pressure of the pilot fluid supplied to the solenoid valve, and a spool including an outputting portion to connect the pressure-receiving portion to an outputting port of the switching valve.

DESCRIPTION OF THE EMBODIMENTS

Referring to drawings, the embodiments of the present invention, a hydraulic system for a working machine and the working machine having the hydraulic system, will be described below.

First Embodiment

A working machine will be explained below.

FIG. 6illustrates a side view of a working machine1according to embodiments of the present invention.FIG. 6illustrates a Skid Steer Loader (SSL) as an example of the working machine1. However, the working machine1according to the embodiments is not limited to the Skid Steer Loader. The working machine1may be other types of the loader working machine such as a Compact Track Loader (CTL). In addition, the working machine1may be other types of working machine other than the loader working machine.

The working machine1includes a machine body (a vehicle body)2, a cabin3, an operation device4, and traveling devices5A and5B.

The cabin3is mounted on the machine body2. An operator seat8is disposed on a rear portion inside the cabin3. Hereinafter, in explanations of all the embodiments of the present invention, a forward direction (a left side inFIG. 6) corresponds to a front side of an operator seated on an operator seat8of the working machine1, a backward direction (a right side inFIG. 6) corresponds to a back side of the operator, a leftward direction (a front surface side of the sheet ofFIG. 6) corresponds to a left side of the operator, and a rightward direction (a back surface side of the sheet ofFIG. 6) corresponds to a right side of the operator. Additionally in the explanations, a machine width direction corresponds to a horizontal direction (a lateral direction) perpendicular to the front to rear direction. A machine outward direction corresponds to a direction from a center portion of the machine body2to the right portion of the machine body2and to the left portion of the machine body2.

In other words, the machine outward direction corresponds to the machine width direction, especially corresponds to a direction separating from the machine body2. In the explanation, a machine inward direction corresponds to a direction opposite to the machine outward direction. In other words, the machine inward direction corresponds to the machine width direction, especially corresponds to a direction approaching the machine body2from the outside of the machine body2.

The cabin3is mounted on the machine body2. The operation device4is constituted of a device configured to perform the working, the operation device4being attached to the machine body2. The traveling device5A is constituted of a device configured to allow the machine body2to travel, the traveling device5A being disposed on the left side of the machine body2. The traveling device5B is constituted of a device configured to allow the machine body2to travel, the traveling device5A being disposed on the right side of the machine body2. A prime mover (an engine or an electric motor)7is mounted on a rear portion of the machine body2internally. The prime mover7is constituted of a diesel engine (that is, an engine). Meanwhile, the prime mover7is not limited to the engine, and may be constituted of an electric motor or the like.

A travel lever9L is disposed on the left side of the operator seat8. A travel lever9R is disposed on the right side of the operator seat8. The travel lever9L on the left side is used for operating the traveling device5A on the left side. The travel lever9R on the right side is used for operating the traveling device5A on the right side.

The operation device4includes booms10, a bucket (a working tool)11, lift links12, control links13, boom cylinders14, and bucket cylinders17. The operation device4includes two booms10; one of the booms10is provided on a right side of the cabin3(referred to as the right boom10) and is capable of freely swinging upward and downward, and the other one of the booms10is provided on a left side of the cabin3(referred to as the left boom10) and is capable of freely swinging upward and downward. The working tool11is a bucket (hereinafter referred to as a bucket11), for example. The bucket11is disposed on tip portions (front end portions) of the booms10and is capable of being freely swung upward and downward. The lift link12and the control link13support a base portion (a rear portion) of the boom10such that the boom10is capable of being freely swung upward and downward. The boom cylinder14is capable of being stretched and shortened to move the boom10upward and downward. The bucket cylinder15is capable of being stretched and shortened to swing the bucket11.

In particular, the operation device4includes two lift links12, two control links13, and two boom cylinders14. One of the lift links12(the right lift link12), one of the control links13(the right control link13), and one of the boom cylinders14(the right boom cylinder14) are disposed on a right side of the machine body2, corresponding to the right boom10. And, the other one of the lift links12(the left lift link12), the other one of the control links13(the left control link13), and the other one of the boom cylinders14(the left boom cylinder14) are disposed on a left side of the machine body2, corresponding to the left boom10. The lift link12is vertically disposed on a rear portion of the base portion of the boom10. The lift link12is pivotally supported at an upper portion (one end side) of the lift link12by an upper portion of a base portion of the boom10. In addition, the lift link12is pivotally supported at a lower portion (the other end side) of the lift link12by a side portion of the rear portion of the machine body2. The control link13is arranged forward from the lift link12. One end of the control link13is pivotally supported by a lower portion of the base portion of the boom10. The other end of the control link13is pivotally supported by the machine body2.

The boom cylinder14is constituted of a hydraulic cylinder configured to move the boom10upward and downward. The boom cylinder14is pivotally supported at an upper portion of the boom cylinder14by a front portion of the base portion of the boom10. The boom cylinder14is pivotally supported at a lower portion of the boom cylinder14by the side portion of the rear portion of the machine body2. When the boom cylinder14is stretched and shortened, the boom10is swung upward and downward by the lift link12and the control link13. The bucket cylinder17is constituted of a hydraulic cylinder configured to swing the bucket11.

The bucket cylinder17connects the boom on the left to a left portion of the bucket11between the boom on the left and the left portion of the bucket11, and connects the boom on the right to a right portion of the bucket11between the boom on the right and the right portion of the bucket11. Not only the bucket11, other working tools can be attached to the tip end (the front portion) of the boom10. The following attachments (spare attachments) are exemplified as the other working tools; for example, a hydraulic crusher, a hydraulic breaker, an angle broom, an earth auger, a pallet fork, a sweeper, a mower, a snow blower, and the like.

In the embodiment, each of the travel device5A and the travel device5B employs a wheeled travel device having a front wheel5F and a rear wheel5R. However, each of the travel device5A and the travel device5B may employ a crawler travel device (including a semi-crawler travel device).

Next, a working hydraulic circuit (a working hydraulic system) disposed on the skid steer loader1will be described below.

The working hydraulic system is constituted of a system configured to operate the boom10, the bucket11, an auxiliary attachment, and the like, and, as shown inFIG. 1, includes a plurality of control valves20and a hydraulic pump (a first hydraulic pump) P1for the working hydraulic system. In addition, the working hydraulic system includes a second hydraulic pump P2other than the first hydraulic pump P1. And, the working hydraulic system is provided with a tank (a hydraulic operation fluid tank)15configured to store a hydraulic operation fluid (also referred to as an operation fluid).

The first hydraulic pump P1is a pump configured to be operated by the power of the prime mover7, and specifically is constituted of a constant-displacement type gear pump. The first hydraulic pump P1is configured to output the operation fluid stored in the tank (the hydraulic operation fluid tank)15. The second hydraulic pump P2is a pump configured to be operated by the power of the prime mover7, and specifically is constituted of a constant-displacement type gear pump.

The second hydraulic pump P2is configured to output the hydraulic fluid stored in the tank (the hydraulic fluid tank)15. Meanwhile, in the hydraulic system for the working machine1, the second hydraulic pump P2outputs the hydraulic fluid for signals and the hydraulic fluid for control. The hydraulic fluid for signals and the hydraulic fluid for control are referred to as a pilot fluid.

The plurality of control valves20are valves configured to control various types of hydraulic actuators disposed on the working machine1. The hydraulic actuator is constituted of a device configured to be operated by the operation fluid, such as a hydraulic cylinder, a hydraulic motor, or the like. In this embodiment, the plurality of control valves20include a first control valve20A, a second control valve20B, and a third control valve20C.

The first control valve20A is constituted of a valve configured to control the hydraulic actuator (the boom cylinder)14that moves the boom10. The first control valve20A is constituted of a direct-acting spool type three-position switching valve. The first control valve20A is switched to a neutral position20a3, a first position20a1other than the neutral position20a3, and the second position20a2other than the neutral position20a3and the first position20a1. In the first control valve20A, the spool is moved by operation of the operation member, and thereby the first control valve20A is switched between the neutral position20a3, the first position20a1, and the second position20a2.

Meanwhile, the operating member is manually operated to directly move the spool, and thereby the first control valve20A is switched. However, it is also possible to move the spool in the hydraulic operation (the hydraulic operation with a pilot valve or the hydraulic operation with a proportional valve), it is possible to move the spool in the electric operation (the electric operation by magnetically exciting the solenoid), or it is possible to move the spool in other methods.

The first control valve20A and the first hydraulic pump P1are connected to each other by an outputting fluid tube27. The operation fluid outputted from the first hydraulic pump P1passes through the outputting fluid tube27and then is supplied to the first control valve20A. In addition, the first control valve20A and the boom cylinder14are connected to each other by a first fluid tube21.

More specifically, the boom cylinder14includes a cylinder body14a, a piston14cdisposed inside the cylinder body14a, and a rod14bconnected to the piston14c. The piston14cis configured to be movable in the axial direction in the cylinder body14a. The piston14cpartitions the inside of the cylinder body (the cylinder tube)14ainto a first fluid chamber14fand a second fluid chamber14g. The first fluid chamber14fis an fluid chamber disposed on the bottom side of the cylinder body14a(on the side opposite to the rod14bside). The second fluid chamber14gis a fluid chamber disposed on the rod side of the cylinder body14a.

A first port14dis disposed on a base end portion (the side opposite to the rod14bside) of the cylinder body14a, the first port14dbeing constituted of a port configured to supply and output the operation fluid and communicating with the first fluid chamber14f. A second port14eis disposed on the tip end (on the rod14bside) of the cylinder body14a, the second port14ebeing constituted of a port configured to supply and output the operation fluid and communicating with the second fluid chamber14g.

The first fluid tube21has a first supplying tube21aand a second supplying tube21b, the first supplying tube21aconnecting the first port31and the first port14dof the first control valve20A each other, the second supplying tube21bconnecting the second port14eand the second port32of the first control valve20A each other.

Thus, when the first control valve20A is set to the first position20a1, the operation fluid is supplied from the first supplying tube21ato the first port14d(the first fluid chamber14f) of the boom cylinder14, and the operation fluid is supplied from the second port14e(the second fluid chamber14g) of the boom cylinder14to the second supplying tube21b.

In this manner, the boom cylinder14is stretched, and thus the boom10moves upward. When the first control valve20A is set to the second position20a2, the operation fluid is supplied from the second supplying tube21bto the second port14e(the second fluid chamber14g) of the boom cylinder14, and the operation fluid is outputted from the first port14dof the boom cylinder14to the first supplying tube21a. In this manner, the boom cylinder14is shortened, and the boom10moves downward.

In addition, the first control valve20A has a first outputting port33and a second outputting port34. The first outputting port33and the second outputting port34are connected to an outputting fluid tube24, the outputting fluid tube24being connected to the operation fluid tank15.

The second control valve20B is constituted of a valve constituted to control the hydraulic actuator (the bucket cylinder)17, the hydraulic actuator17being configured to move the bucket11. The second control valve20B is constituted of a direct-acting three-position switching valve having a spool. The second control valve20B is switched to a neutral position20b3, to a first position20b1other than the neutral position20b3, and to a second position20b2other than the neutral position20b3and the first position20b1. In the second control valve20B, the spool is moved by operation of the operation member, and thereby the second control valve20B is switched between the neutral position20b3, the first position20b1, and the second position20b2.

Meanwhile, the operating member is manually operated to directly move the spool, and thereby the second control valve20B is switched. However, it is also possible to move the spool in the hydraulic operation (the hydraulic operation with a pilot valve or the hydraulic operation with a proportional valve), it is possible to move the spool in the electric operation (the electric operation by magnetically exciting the solenoid), or it is possible to move the spool in other methods. For convenience of explanation, the hydraulic actuator (the bucket cylinder)17may be referred to as a second hydraulic actuator17.

The second control valve20B and the first control valve20A are connected to each other by a first supplying-outputting fluid tube28aand a second fluid supplying-outputting fluid tube28b. When the first control valve20A is in the neutral position20a3, the operation fluid is supplied to the second control valve20B through the first fluid supplying-outputting fluid tube28a. In addition, when the first control valve20A is in the first position20a1or the second position20a2, the operation fluid is supplied to the second control valve20B through the second supplying-outputting fluid tube28b.

The second control valve20B and the second hydraulic actuator17are connected to each other by a second fluid tube22. In particular, the second hydraulic actuator (the bucket cylinder)17includes a cylinder body17a, a piston17c, and a rod17b, the piston17cbeing disposed on the cylinder body17aso as to be movable in the axial direction, the rod17bbeing connected to the piston17c. The piston17cpartitions the inside of the cylinder tube17ainto a first fluid chamber17fand a second fluid chamber17g.

The first fluid chamber17fis a fluid chamber disposed on the bottom side of the cylinder body17a(on the side opposite to the rod17bside). The second fluid chamber17gis a fluid chamber disposed on the rod side of the cylinder body17a. A first port17dis disposed on the base end portion of the cylinder body17a(on the side opposite to the rod17bside), the first port17dbeing a port configured to supply and output the operation fluid and communicating with the first fluid chamber17f. A second port17eis disposed on the tip end of the cylinder body17a(on the side of the rod17b), the second port17ebeing a port configured to supply and output the operation fluid and communicating with the second fluid chamber17g.

The second fluid tube22includes a first supplying tube22aand a second supplying tube22b, the first supplying tube22aconnecting the second port17eand the first port35of the second control valve20B to each other, the second supplying tube22bconnecting the first port17dand the second port36of the second control valve20B to each other.

Thus, when the second control valve20B is set to the first position20b1, the operation fluid is supplied from the first supplying tube22ato the second port17e(the second fluid chamber17g) of the bucket cylinder17, and the operation fluid is outputted from the first port17d(the first fluid chamber170of the bucket cylinder17to the second supplying tube22b. In this manner, the bucket cylinder17is shortened, and thereby the bucket11performs the shoveling operation.

When the first control valve20A is set to the second position20a2, the operation fluid is supplied from the second supplying tube22bto the first port17d(the first fluid chamber170of the bucket cylinder17, and the operation fluid is outputted from the second port17e(the second fluid chamber17g) of the bucket cylinder17to the first supplying tube22a. In this manner, the bucket cylinder17is stretched, and thereby the bucket11performs the dumping operation.

The third control valve20C is constituted of a valve configured to control the hydraulic actuator16(the hydraulic cylinder, the hydraulic motor, and the like), the hydraulic actuator16being mounted on the auxiliary attachment. The third control valve20C is constituted of a direct-acting three-position switching valve having a spool configured to be operated by the pilot fluid. The third control valve20C is configured to be switched to a neutral position the first position20c1different from the neutral position20c3and a neutral position20c3, a first position20c1other than the neutral position20c3, and the second position20c2other than the neutral position20c3and the first position20c1.

In the third control valve20C, the spool is moved by the pressure of the pilot fluid, and thereby the third control valve20C is switched between the neutral position20c3, the first position20c1, and the second position20c2. A connecting member18is connected to the third control valve20C by the supplying-outputting fluid tubes83aand83b. An fluid tube is connected to the connecting member18, the fluid tube being connected to the hydraulic actuator16of the auxiliary attachment.

Thus, when the third control valve20C is set to the first position20c1, the operation fluid is supplied from the supplying-outputting fluid tube83ato the hydraulic actuator16of the auxiliary attachment. When the third control valve20C is set to the second position20c2, the operation fluid is supplied from the supplying-outputting fluid tube83bto the hydraulic actuator16of the auxiliary attachment. In this manner, the operation fluid is supplied from the supplying-outputting fluid tube83aor the supplying-outputting fluid tube83bto the hydraulic actuator16, and thereby the hydraulic actuator16(the auxiliary attachment) is operated.

Then, the hydraulic system for the working machine1suppresses the fluctuation of the pressure of the hydraulic actuator, thereby suppressing the traveling vibration of the working machine1(carrying out the anti-vibration operation of the machine body2). That is, it is possible to carry out the ride control. Further, the hydraulic system for the working machine1outputs the operation fluid in the hydraulic actuator, and thereby the hydraulic system carries out the floating operation.

The hydraulic system for the working machine1is provided with a switching valve (an operational switching valve)50configured to switch the operation between the anti-vibration operation and the floating operation. The switching valve50is constituted of a three-position switching valve configured to be switched between a first position50a, a second position50b, and a neutral position50c. The switching valve50carries out the floating operation in the case where the switching valve50is in the first position50a, carries out the anti-vibration operation in the case where the switching valve50is in the second position50b, and stops the anti-vibration operation and the floating operation in the case where the switching valve50is in the neutral position50c.

Hereinafter, the switching valve50will be described in detail blow.

The switching valve50has a first port51, a second port52, a third port53, a fourth port54, and a fifth port55. A first communicating tube61is connected to the first port51, the first communicating tube61being connected to the first supplying tube21a. A second communicating tube62is connected to the second port52, the second communicating tube62being connected to the second supply channel21b. The third port53and the fourth port54are connected to an outputting fluid tube24, the outputting fluid tube24being connected to the operation fluid tank15. An accumulator56is connected to the fifth port55, the accumulator56serving as a pressure accumulator.

In addition, the switching valve50is constituted of a pilot type switching valve incorporating a solenoid valve (an electromagnetic proportional valve). The switching valve50is provided with a first pressure-receiving portion50A, a second pressure-receiving portion50B, a first solenoid50C, and a second solenoid50D. The first pressure-receiving portion50A is configured to receive a pressure of the operation fluid (the pilot fluid). The second pressure-receiving portion50B is configured to receive a pressure of the pilot fluid. The first pressure-receiving portion50A is arranged on one side of the spool in the longitudinal direction, and the second pressure-receiving portion50B is arranged on the other side of the spool in the longitudinal direction. An fluid tube (a pilot supplying tube)23is connected to the first pressure-receiving portion50A and to the second pressure-receiving portion50B, the fluid tube23being connected to the second hydraulic pump P2, and thereby the operation fluid (the pilot fluid) is supplied to the first pressure-receiving portion50A and to the second pressure-receiving portion50B.

When the first solenoid50C is magnetized, the pilot pressure received by the first pressure-receiving portion50A is applied to the spool, the spool is moved to one direction, and thereby the switching valve50is switched to the first position50a. When the second solenoid50D is magnetized, the pilot pressure received by the second pressure-receiving portion50B is applied to the spool, the spool is moved to the other direction, and thereby the switching valve50is switched to the second position50b. When one of the first solenoid50C and the second solenoid50D is demagnetized, the spool stays at the neutral position, and thus the switching valve50is switched to the neutral position50c.

When the switching valve50is set to the first position50a, the first port51and the fourth port54are connected to each other by a spool. In this manner, the operation fluid in the first fluid chamber14fof the boom cylinder14flows through the first supplying tube21a, the first communicating tube61, the first port51and the fourth port54, and then is outputted to the outputting fluid tube24. In addition, when the switching valve50is set to the first position50a, the second port52and the third port53are connected to each other by the spool. In this manner, the operation fluid in the second fluid chamber14gof the boom cylinder14flows through the second supplying tube21b, the second communicating tube62, the second port52, and the third port53, and then is outputted to the outputting fluid tube24.

That is, when the switching valve50is in the first position50a, the first communicating tube61and the second communicating tube62communicate with the outputting fluid tube24by the spool, and the operation fluid in the first fluid chamber14fand the second fluid chamber14gis outputted to the outputting fluid tube24, thereby carrying out the floating operation.

In addition, when the switching valve50is set to the second position50b, the first port51and the fifth port55are connected to each other by the spool. In this manner, the first fluid chamber14fof the boom cylinder14passes through the first supplying tube21a, the first communicating tube61, the first port51, and the fifth port55, and then connects to the accumulator56. In addition, when the switching valve50is set to the second position50b, the second port52and the third port53are connected to each other by the spool, and thereby the operation fluid in the second fluid chamber14gof the boom cylinder14passes through the second supplying tube21b, the second communicating tube62, the second port52, and the third port53, thereby being outputted to the outputting fluid tube24.

That is, when the switching valve50is in the second position50b, the first communicating tube61communicates with the accumulator56, and the second communicating tube62is made communicate with the outputting fluid tube24by the spool (the fluid chamber14fcommunicates with the accumulator56, and the second fluid chamber14gis made communicate with the outputting fluid tube24), thereby carrying out the anti-vibration operation.

As described above, by carrying out the anti-vibration operation, even when the bucket11vibrates upward and downward while the working machine1is traveling, the accumulator56absorbs the pressure fluctuations in the first fluid chamber14fof the boom cylinder14, thereby suppressing the traveling vibrations of the working machine1.

The switching control to the switching valve50is carried out by the control device42. The control device42is constituted of a CPU or the like, and carries out the switching of the switching valve50between the floating operation and the anti-vibration operation. A first switch91and a second switch92are connected to the control device42. The first switch91and the second switch92are arranged in the vicinity of the operator seat8. An operator seated on the operator seat8can operate the first switch91and the second switch92.

The first switch91is constituted of a switch configured to be switched to be between on and off, and when switched to be on, issues a first command of the floating operation to the control device42. When the first switch91is switched to be off, the first switch91does not issue the first command to the control device42.

When the control device42obtains the first command issued from the first switch91, the control device42outputs a control signal to the first solenoid50C of the switching valve50, and thereby magnetizes the first solenoid50C. In addition, the control device42outputs a control signal to the first solenoid50C of the switching valve50under a state where the control device42has not obtained the first command of the first switch91yet (OFF), and thereby demagnetizes the first solenoid50C.

The second switch92is constituted of a switch configured to be switched to be between on and off, and when switched to be on, issues a second command of the anti-vibration operation to the control device42. When the second switch92is switched to be off, the second switch92does not issue the second command to the control device42. When the control device42obtains the second command issued from the second switch92, the control device42outputs a control signal to the second solenoid50D of the switching valve50, and thereby magnetizes the second solenoid50D. In addition, the control device42outputs a control signal to the second solenoid50D of the switching valve50under a state where the control device42has not obtained the second command of the second switch92yet, and thereby demagnetizes the first solenoid50D.

When the first switch is turned on from off during the anti-vibration operation carried out in accordance with the second switch92switched to be on, the control device42stops the anti-vibration operation, the anti-vibration operation carried out in accordance with the second switch92switched to be on. That is, when the first switch91is turned on and the first command is inputted under the state where the second solenoid50D is magnetized in accordance with the second command (the switching valve50is in the second position50b), the first command is prioritized over the second command, and then the second solenoid50D is demagnetized even when the second switch92is on. On the other hand, the first solenoid50C is magnetized, and thereby the switching valve50is switched to the first position50a.

According to the control device42, the floating operation and the anti-vibration operation can be easily switched by the first switch91and the second switch92, and additionally when the commands for both of the floating operation and the anti-vibration operation are issued, the floating operation is prioritized over the anti-vibration operation, thereby improving the efficiency of the operation carried out by the working machine1.

In addition, the hydraulic system has the configuration where either the anti-vibration operation or the floating operation is switched by the switching valve (the operational switching valve)50, and thus the switching valve50reduces the operation fluid outputted from the switching valve in comparison with the case where the switching valve for the anti-vibration operation and the switching valve for the floating operation are operated at the same time in the hydraulic circuit having the configuration where the switching valve for the anti-vibration operation and the switching valve for the floating operation are separately provided.

In addition, in a hydraulic circuit where a switching valve for the anti-vibration operation and a switching valve for the floating operation are separately provided, the switching valve leaks the operation fluid when the anti-vibration operation is stopped, and the switching valve leaks the operation fluid when the floating operation is stopped. Both of the leakings provides the amount of the leakings (the total amount of the leakings). On the other hand, since the switching valve (the operational switching valve)50is one valve configured to switch the operation between the anti-vibration operation and the floating operation, the switching valve50C reduces a leaking amount from the switching valve50in comparison with the total amount of the leakings.

In addition, in the switching valve50, it is possible to reduce the number of constituent parts as compared with the case of the configuration where the switching valve for the anti-vibration operation and the switching valve for the floating operation are provided.

Meanwhile, the switching valve50may have a configuration to warm up the pilot fluid.FIG. 2Ais a view showing a part of the inside of the switching valve50with a hydraulic circuit. That is, the switching valve50shown inFIG. 1and the switching valve50inFIG. 2Aare equivalent to each other. As shown inFIG. 2A, the pilot supplying tube23is connected to the first solenoid valve57A having the first solenoid50C and to the second solenoid valve57B having the second solenoid50D. The first solenoid valve57A and the first pressure-receiving portion50A are connected to each other by the first inner fluid path65, and the second solenoid valve57B and the first pressure-receiving portion50B are connected to each other by the second inner fluid tube66. An outputting fluid tube25A is disposed on the intermediate portion of the first inner fluid tube65, and the outputting fluid tube25A is connected to the operation fluid tank15.

In addition, an outputting fluid tube25B is disposed on the intermediate portion of the second inner fluid tube66, and the outputting fluid tube25B is connected to the operation fluid tank15. Meanwhile, the inner diameters of the outputting fluid tube25A and the outputting fluid tube25B are smaller than the inner diameters of the first inner fluid tube65and the second inner fluid tube66, and thereby the throttling portion68is formed. And,FIG. 2Aschematically shows the spool58.

In this manner, by opening at least one of the first electromagnetic valve57A and the second electromagnetic valve57B in the switching valve50, the pilot fluid flows from the first inner fluid tube65to the first pressure-receiving portion50A or from the second inner fluid tube66to the second pressure-receiving portion50B, and also is outputted to the outputting fluid tubes25A and25B.

In the case of warming up the pilot fluid, the degree of opening aperture of the first solenoid valve57A or of the second solenoid valve57B, that is, the pressure of the operation fluid applied to the first pressure-receiving portion50A and to the second pressure-receiving portion50B (a received pressure) is set to be lower than a switching pressure at which the spool58A is switched to any one of the switching positions (the first position50aand the second position50b), and then substantially the entire amount of the operation fluid supplied to the first inner fluid tube65and to the second inner fluid tube66is outputted to the outputting fluid tube25A and to the outputting fluid tube25B.

For example, a measuring device69is connected to the control device42, the measuring device69being configured to measure the temperature of the operation fluid. In the case where the temperature measured by the measuring device69is low [the temperature range where the viscosity of the operation fluid is high (for example, −10° C.)], the first solenoid valve57A or the second solenoid valve57B is opened to control the inside of the pressure-receiving portion (the inside of the inner fluid tube) to be lower than the switching pressure (performs the warm-up processing).

Under a state where the first solenoid valve57A and the second solenoid valve57B are opened for the warming up to preliminarily pressurizing the operation fluid (the pilot fluid) (under the warm-up processing), it is preferred that the control device42prohibits the floating operation or the braking operation and does not perform the switching in the switching valve50(holds the neutral position50c).

In particular, even when the control device42obtains the first command and the second command during the warm-up processing, the control device42maintains the opening apertures of the first solenoid valve57A and the second solenoid valve57B to be smaller than the opening apertures corresponding to the switching pressure. Then, when the warm-up processing is completed, the control device42fully closes the first solenoid valve57A and the second solenoid valve57B once, and outputs the operation fluid in the inner fluid tube (the first inner fluid tube65and the second inner fluid tube66) to the operation fluid tank15and the like. And then, after the first solenoid valve57A and the second solenoid valve57B are once fully closed, the control device42switches the switching valve50in accordance with the commands of the first switch91and the second switch92.

As described above, when the switching to the floating operation or to the braking operation is prohibited during the warm-up processing, the positions of the spool58A at the starts of the switchings to the floating operation and to the braking operation are set to substantially the same position (to the adequate neutral position50c) (that is, the spool58A starts to move from a constant position with suppression of the influence of hysteresis), and thus the switching valve50is switched more smoothly.

The stoppage of the warm-up processing by the control device42is carried out when the temperature of the operation fluid detected by the measuring device69reaches a predetermined temperature [a temperature range where the viscosity of the operation fluid is low (−10° C. or more or 0° C. or more)]. Additionally in the example mentioned above, the temperature of the operation fluid is measured by the measuring device69, and the warm-up processing is performed based on the measured temperature. However, the warm-up processing may be performed in accordance with a command from a switch and the like.

For example, the control device42is provided with a third switch93configured to be switched between on and off. Then, the control device42performs the warm-up processing when the third switch93is on, and when the third switch93is off, the control device42performs the normal processing, for example, performs the floating operation and the anti-vibration operation each carried out by the first switch91and the second switch92. In addition, the above-described temperature of the operation fluid is merely an example, and the present invention is not limited thereto.

In the embodiment described above, the first solenoid valve57A or the second solenoid valve57B is opened when the warm-up processing is performed. However, both of the first solenoid valve57A and the second solenoid valve57B may be opened to apply the pilot fluid to the first pressure-receiving portion50A and to the second pressure-receiving portion50B. For example, when the temperature measured by the measuring device69is low, the control device42opens the first solenoid valve57A and the second solenoid valve57B substantially at the same time, and thereby applies the pilot fluid to the first pressure-receiving portion50A and to the first pressure-receiving portion50B, thereby performing the warm-up processing.

In that case, in order to apply the pilot fluid to both the first pressure-receiving portion50A and to the second pressure-receiving portion50B, the first solenoid valve57A and the second solenoid valve57B need not to set the opening aperture to be less than the opening aperture corresponding to the switching pressure.

InFIG. 2A, the outputting fluid tubes25A and25B are disposed on the connecting fluid tube65and the second inner fluid tube66, the connecting fluid tube65connecting the pressure-receiving portions (the first pressure-receiving portion50A and the second pressure-receiving portion50B) to the solenoid valves (the first solenoid valve57A and the second solenoid valve57B). However, as shown inFIG. 2B, the pressure-receiving portions (the first pressure-receiving portion50A and the second pressure-receiving portion50B) and an outputting portion67may be disposed on the spool58A, the outputting portion67being connected to an outputting port T1that is disposed inside the switching valve50.

For example, as shown inFIG. 2B, an outputting groove67is disposed on the spool58A, the outputting groove being formed by cutting out the outer peripheral surface of the spool58A on both end portions of the spool58A in the longitudinal direction (on one end side corresponding to the first pressure-receiving portion50A and on the other end side corresponding to the second pressure-receiving portion50B). For example, when the switching valve50(the spool58A) is in the neutral position50c, the outputting port T1is connected to the pressure-receiving portion50A and the pressure-receiving portion50B by the outputting groove67. In this manner, the pilot fluid is warmed up.

Second Embodiment

FIG. 3shows a hydraulic system according to a second embodiment of the present invention. The hydraulic system for the working machine1according to the second embodiment is a system configured to perform the floating operation and the anti-vibration operation separately from each other not by a single switching valve. In the second embodiment, configurational parts similar to those of the first embodiment are denoted by the same reference numerals, and explanations thereof will be omitted. In the second embodiment, configurations different from those of the first embodiment will mainly be described.

As shown inFIG. 3, the hydraulic system for the working machine1includes an anti-vibration switching valve70and a float switching valve80.

The anti-vibration switching valve70is constituted of a two-position switching valve configured to be switched between an anti-vibration position70aand a stop position70b, the anti-vibration position70aallowing the accumulator56and the boom cylinder14to communicate with each other and thereby to perform the anti-vibration operation, the stop position70ballowing to block the communicating between the accumulator56and the boom cylinder14and thereby to stop the anti-vibration operation. In addition, the anti-vibration switching valve70is constituted of a solenoid switching valve configured to be switched to the stop position70bby a spring and switched to the anti-vibration position70aby magnetizing the solenoid70c.

The anti-vibration switching valve70has a first port71, a second port72, a third port73, and a fourth port74. The first port71is connected to the accumulator56by a fluid tube75. The second port72is connected to the outputting fluid tube76. The third port73is connected to a third communicating tube77connected to the first supplying tube21a. The fourth port74is connected to a fourth communicating tube78connected to the second supplying tube21b.

When the second switch92is turned on, the control device42outputs a control signal to the solenoid70cof the anti-vibration switching valve70, and thereby magnetizes the solenoid70c. In this manner, the anti-vibration switching valve70is switched to the anti-vibration position70a, the first fluid chamber14fof the boom cylinder14communicates with the accumulator56, and the second fluid chamber14gof the boom cylinder14communicates with the outputting fluid tube76.

In addition, the control device42outputs a control signal to the solenoid70cof the anti-vibration switching valve70under a state where the control device42does not obtain the second command issued from the second switch92(OFF), thereby demagnetizing the solenoid70c. In this manner, the anti-vibration switching valve70is switched to the stop position70b, the communicating between the first fluid chamber14fof the boom cylinder14and the accumulator56is block, and the communication between the second fluid chamber14gof the boom cylinder14and the outputting fluid tube76is blocked.

The float switching valve80includes a first float switching valve80A and a second float switching valve80B. Each of the first float switching valve80A and the second float switching valve80B is constituted of a two-position switching valve configured to be switched between a float position80aand a block position80b, the float position80aallowing the first supplying tube21aand the second supplying tube21bto communicate with the outputting fluid tube24, the block position80ballowing to block the communicating between the outputting fluid tube24and the first supplying tube21aand between the outputting fluid tube24and the second supplying tube21b. In addition, the first float switching valve80A and the second float switching valve80B are configured to be switched to the block position80bby a spring and switched to the float position80aby magnetizing the solenoid80c.

The first float switching valve80A has a first port81and a second port82. The first port81is connected to a fifth communicating tube85connected to a first supplying tube21a. The second port82is connected to the outputting fluid tube24. The second float switching valve80B has a third port83and a fourth port84. The third port83is connected to a sixth communicating tube86connected to the second supplying tube21b. The fourth port84is connected to the outputting fluid tube24.

When the first switch91is turned on, the control device42outputs a control signal to the solenoids80cof the first float switching valve80A and the second float switching valve80B, and thereby magnetizing the solenoid80c. In this manner, the first float switching valve80A and the second float switching valve80B are switched to the float position80a, and thereby the operation fluid in the first fluid chamber14fand the second fluid chamber14gof the boom cylinder14is outputted to the outputting fluid tube24.

In addition, the control device42outputs a control signal to the solenoids80cof the first float switching valve80A and the second float switching valve80B under a state where the control device42does not obtain the first command of the first switch91, thereby demagnetizing the solenoids80c. In this manner, the first float switching valve80A and the second float switching valve80B are switched to the block position80b, and thereby blocking the communicating between the outputting fluid tube24and the first fluid chamber14fand the second fluid chamber14gof the boom cylinder14.

Also in the present embodiment, in the anti-vibration operation performed by the second switch92turned on, the control device42stops the anti-vibration control performed by the turned-on second switch92when the first switch is turned on from the off state.

That is, under the state where the solenoid70cof the anti-vibration switching valve70is magnetized in accordance with the second command (the anti-vibration switching valve70is in the anti-vibration position70a), the control device42gives the first command priority over the second command when the first switch91is turned on and the first command is inputted. And, the control device42demagnetizes the solenoid70cof the anti-vibration switching valve70even when the second switch is on, and while the solenoids80cof the first float switching valve80A and the second float switching valve80B are magnetized. In this manner, the float switching valve80A and the second float switching valve80B are switched to the float position80a.

According to the description mentioned above, even when the anti-vibration switching valve70and the float switching valve80are separately provided, the float operation is given priority under the commands of both of the floating operation and the anti-vibration operation, and thereby the operation by the working machine1is efficiently performed.

In the embodiment described above, the switching valve50is provided with the fluid tube for warming up the pilot fluid. However, the anti-vibration switching valve70or the float switching valve80may be provided with the fluid tube for the warming up of the pilot fluid. Meanwhile, the warm-up processing for the anti-vibration switching valve70or the float switching valve80in the control device42is similar to that of the switching valve50, and thus the explanation thereof will be omitted.

As shown inFIG. 4A, the anti-vibration switching valve70is constituted of a pilot type switching valve in which a solenoid valve (an electromagnetic proportional valve) is incorporated. In the anti-vibration switching valve70, the electromagnetic valve95and a pressure-receiving portion96are connected to each other by an inner fluid tube97, the electromagnetic valve95having the solenoid70c, the pressure-receiving portion96being configured to receive the operation fluid are connected, and the inner fluid tube97is provided with the outputting fluid tube25C. The configurations of the solenoid valve95and the pressure-receiving portion96are similar to the solenoid valve and the pressure-receiving portion provided in the switching valve50. In this manner, by applying the pressure to the pressure-receiving portion96to such an extent that the anti-vibration switching valve70(the spool58B) is not switched to the anti-vibration position70a(to be lower than the switching pressure), the operation fluid of the inner fluid tube97is outputted to the outputting fluid tube25C.

In addition, as shown inFIG. 4B, each of the float switching valves80(the first float switching valve80A and the second float switching valve80B) is constituted of a pilot type switching valve in which a solenoid valve (an electromagnetic proportional valve) is incorporated. In the first float switching valve80A and the second float switching valve80B, the electromagnetic valve98having the solenoid80cand the pressure-receiving portion99receiving the operation fluid are connected to each other by an inner fluid tube100, and the inner fluid tube is provided with the outputting fluid tube25D.

The configurations of the solenoid valve98and the pressure-receiving portion99are similar to the solenoid valve and the pressure-receiving portion disposed on the switching valve50. In this manner, by applying the pressure to the pressure-receiving portion99to such an extent that the float switching valves80(the first float switching valve80A and the second float switching valve80B) are not switched to the floating position80a(to be lower than the switching pressure), the operation fluid of the inner fluid tube100is outputted to the outputting fluid tube25D, thereby warming up the pilot fluid.

In addition, as shown inFIG. 4C, in the case where the spool58B of the anti-vibration switching valve70is provided with the outputting groove67, the groove is formed by cutting off the circumference surface on the spool58B on one side of the spool58B in the longitudinal direction (on one side corresponding to the pressure-receiving portion96). Under the state where, for example, the anti-vibration switching valve70(the spool58B) is in the stop position70b, the outputting port T2and the pressure-receiving portion96are connected to each other by the outputting groove67, and thereby warming up the pilot fluid.

In addition, as shown inFIG. 4D, in the case where the outputting groove (an outputting portion)67is disposed on the spool58C of the float switching valve80(the first float switching valve80A and the second float switching valve80B), the groove is formed by cutting off the circumference surface on the spool58C on one side of the spool58C in the longitudinal direction (on one side corresponding to the pressure-receiving portion99). And, under the state where, for example, the float switching valve80(the first float switching valve80A and the second float switching valve80B) is in the block position80b, the outputting port T3and the pressure-receiving portion99are connected to each other by the outputting groove67, and thereby warming up the pilot fluid.

As described above, according to the examples described above, it is possible to easily warm up the pilot fluid with use of any one of the anti-vibration switching valve70and the float switching valve80.

FIG. 5Ashows a modified example of the switching valve50.

As shown inFIG. 5A, two accumulators, that is, a first accumulator56A and a second accumulator56B are connected to the switching valve50. In particular, the first accumulator56A is connected to the fifth port55. The second accumulator56B is connected to the third port53.

When the switching valve50is set to the first position50a, the first port51and the second port52are connected to each other, and the first port51and the second port52are connected to the fourth port54. In this manner, the operation fluid in the first fluid chamber14fof the boom cylinder14flows through the first supplying tube21a, the first communicating tube61, the first port51, and the fourth port54and is outputted to the outputting fluid tube24, and the operation fluid in the second fluid chamber14gof the boom cylinder14flows through the second supplying tube21b, the second communicating tube62, the second port52, and the fourth port54and is outputted to the outputting fluid tube24. In this manner, the floating operation is carried out.

When the switching valve50is set to the second position50b, the first port51and the fifth port55are connected to each other by a spool. In this manner, the first fluid chamber14fof the boom cylinder14is connected to the accumulator56A through the first supplying tube21a, the first communicating tube61, the first port51, and the fifth port55. In addition, when the switching valve50is set to the second position50b, the second port52and the third port53are connected to each other by a spool.

In this manner, the second fluid chamber14gof the boom cylinder14is connected to the second accumulator56B through the second supplying tube21b, the second communicating tube62, the second port52, and the third port53. That is, when the switching valve50is in the second position50b, the first communicating tube61communicates with the first accumulator56A, and the second communicating tube62communicates with the second accumulator56B through the spool (the first fluid chamber14fcommunicates with the first accumulator56A, and the second fluid chamber14gcommunicates with the second accumulator56B), thereby the anti-vibration operation is carried out.

FIG. 5Bshows a modified example of the anti-vibration switching valve70. As shown inFIG. 5B, two accumulators, that is, the first accumulator56A and the second accumulator56B are connected to the anti-vibration switching valve70. In particular, the first accumulator56A is connected to the first port71. The second accumulator56B is connected to the second port72.

When the anti-vibration switching valve70is set to the anti-vibration position70a, the first fluid chamber14fof the boom cylinder14communicates with the first accumulator56A, and the second fluid chamber fluid chamber14gof the boom cylinder14communicates with the second accumulator56B. On the other hand, when the anti-vibration switching valve70is set to the stop position70b, the communicating between the first fluid chamber14fof the boom cylinder14and the first accumulator56A is blocked, and the communicating between the second fluid chamber14gof the boom cylinder14and the second accumulator56B is blocked.

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.

In the embodiments described above, the operation fluid is outputted to an operation fluid tank. However, the operation fluid may be outputted to other components. That is, the fluid tube for outputting the operation fluid may be connected to a portion other than the operation fluid tank, and, for example, the fluid tube for outputting the operation fluid may be connected to the suction portion of the hydraulic pump (a portion for sucking the operation fluid) or may be connected to other portions. In addition, in the case where the plurality of control valves (switching valves) are provided with the warm-up circuits (the outputting fluid tubes25A to25D, the inner fluid tube, the outputting portion, and the like), it is preferred that the hydraulic pump (the pump port) is provided with the warm-up circuit in the switching valve arranged on the most downstream side.

In the embodiment described above, the switching valve50is constituted of an electromagnetic/pilot-type switching valve. However, the switching valve50may be constituted of a pilot type switching valve configured to be switched by the pilot fluid applied to the pressure-receiving portions (the first pressure-receiving portion50A and the second pressure-receiving portion50B), or may be constituted of a solenoid type switching valve (the electromagnetic switching valve) configured to be switched between on and off by a solenoid instead of the pressure-receiving portion.