JP2010084784A - Float control system for working machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a float control system for a working machine capable of smoothly and surely operating a float when controlling the float in an arm. <P>SOLUTION: A float mode switch 78 for making a float mode 76 valid or invalid it is connected to a controller 75. The float mode 76 of the controller 75 operates a switching device 65 so that the arm 22 is floated when the arm 22 is lowered at a predetermined value or more of operating speed and the tip height of the arm 22 comes down to a predetermined value or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a float control system for a work machine.

2. Description of the Related Art Conventionally, in a working machine that performs various work, it is common to operate a work attachment with a hydraulic actuator. The hydraulic actuator is designed to extend and retract according to the pressure of the hydraulic oil discharged from the pump, etc., but has a float control that allows the hydraulic actuator to expand and contract freely by releasing the pressure acting on the hydraulic actuator. A working machine has been developed (for example, Patent Document 1).
In the working machine of Patent Document 1, in the hydraulic supply path of the working hydraulic actuator of the working attachment provided at the tip of the arm supported so as to be swingable up and down on the machine frame, the bottom side flow path and the top side flow path Is provided, and a float valve that opens and closes the hydraulic oil communication passage is provided on the hydraulic oil communication passage, and the float valve is operated to perform the float control.
US Pat. No. 6,389,952

In the working machine of Patent Document 1, when the operation member that operates the work attachment is in the neutral position (the work attachment is stopped), the operation of the work hydraulic actuator is switched from the normal control state to the float control. ing.
However, the actual situation is that the technique for switching the float control disclosed in Patent Document 1 cannot be applied to the arm of the working machine. That is, the working attachment (working hydraulic actuator) operates on the tip side of the arm, while the arm swings up and down with respect to the machine frame. Due to the difference, the condition for switching from the normal control state to the float control must be newly established separately from the working hydraulic actuator in the arm float control.

  In view of the above problems, an object of the present invention is to provide a float control system for a working machine that can perform the float operation smoothly and reliably when performing the float control in the arm.

  The technical means of the present invention for solving this technical problem includes an arm that is supported by a machine frame so as to be swingable up and down, and an attachment is detachable on the tip side, and an arm hydraulic pressure that operates the arm with hydraulic oil. An actuator, an arm control valve that controls the flow rate of hydraulic oil supplied to the arm hydraulic actuator, and a bottom hydraulic supply path of the arm hydraulic actuator and a top hydraulic supply path of the arm hydraulic actuator communicate with each other. A hydraulic fluid communication passage, a switching device provided on the hydraulic fluid communication passage for opening and closing the hydraulic fluid communication passage, and a controller capable of controlling the switching device to float the arm. Is connected to a float mode switch for enabling or disabling the float mode, and the controller Float mode, together with the arm is moved down at the operating speed of a predetermined value or more, the arm is in that operating the switching device to operate the float when the height of the tip of the arm is equal to or less than a predetermined value.

  A sensor for detecting an arm angle is connected to the controller, and the float mode calculates the height of the arm based on the arm angle detected by the sensor and detects the operating speed of the arm based on the angular speed of the arm angle. Is preferred.

  According to the present invention, when performing the float control in the arm, the float operation can be performed smoothly and reliably.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First embodiment]
1 and 2, a work machine 1 (track loader) according to the present invention includes a machine frame 2, a work device 3 attached to the machine frame 2, and a pair of left and right traveling devices 4 that support the machine frame 2. The cabin 5 (driver protection device) is mounted on the upper front side of the body frame 2.
The body frame 2 is made of an iron plate or the like, and includes a bottom wall 6, a pair of left and right side walls 7, a front wall 8, and a support frame 9 provided at the rear of each of the left and right side walls 7. A space between the pair of left and right support frames 9 is provided at the rear end of the machine body frame 2 so as to be openable and closable.

The cabin 5 has a front and lower end abuttingly mounted on an upper edge portion 8a of the front wall 8 of the body frame 2, and a vertical middle portion on the back is attached to the support bracket 11 of the body frame 2 in the horizontal direction. It is supported so as to be swingable around 12 and is configured so that maintenance or the like in the body frame 2 can be performed by swinging the cabin 5 upward around the support shaft 12.
A driver's seat 13 is provided in the cabin 5, and a driving operation member for operating the traveling device 4 is arranged on one side (for example, the left side) of the driver's seat 13. A work operation member 15 for operating the work device 3 is disposed on the side (for example, the right side). A display device (meter) 14 is provided on the front side of the driver's seat 13 for displaying the rotation speed, water temperature, oil temperature, etc. of the engine 29 of the work machine 1 and displaying various warnings.

The cabin 5 is covered with a roof on the upper surface, the left and right side surfaces are closed with side walls formed with a number of square holes, the upper back is covered with rear glass, and the center in the front-rear direction is closed with the bottom wall. The front side is formed in a box shape, and the front side is the entrance.
Each of the left and right traveling devices 4 includes a pair of front and rear driven wheels 16, a drive wheel 17 disposed between the front and rear driven wheels 16 and closer to the rear, and a plurality of wheels 18 disposed between the front and rear driven wheels 16. And a crawler type traveling device including an endless belt-like crawler belt 19 wound around the front and rear driven wheels 16, the drive wheels 17, and the rollers 18.

The front and rear driven wheels 16 and the wheels 18 are attached to a track frame 20 attached and fixed to the body frame 2 so as to be rotatable about a horizontal axis, and the drive wheels 17 are hydraulically driven travel motors attached to the track frame 20. 21L, 21R (foil motor) is attached to a rotating drum, and the crawler belt 19 is circulated in the circumferential direction by rotating the driving wheel 17 around the left and right axes by the traveling motors 21L, 21R. The machine 1 is configured to move forward and backward.
The working device 3 includes a pair of left and right arms 22 and a bucket 23 (working tool) attached to the tip of the arms 22.

The pair of left and right arms 22 are disposed on both the left and right sides of the body frame 2 and the cabin 5, and the left and right arms 22 are connected to each other by a connecting body at a midway portion on the front side.
Each of the left and right arms 22 has a first lift link 24 and a second lift link on the rear upper part of the body frame 2 so that the distal end side of the arm 22 moves up and down on the front side of the body frame 2. 25 and is supported so as to be swingable up and down.
Also, a lift cylinder (arm hydraulic actuator) 26 composed of a double-acting hydraulic cylinder is provided between the base side of each of the left and right arms 22 and the rear lower part of the body frame 2. The left and right arms 22 swing up and down by expanding and contracting the left and right simultaneously.

A mounting bracket 27 is pivotally connected to the front end side of each of the left and right arms 22 so as to be rotatable about a left and right axis, and the back side of the bucket 23 is attached to the left and right mounting brackets 27.
In addition, a tilt cylinder 28 composed of a double-acting hydraulic cylinder is interposed between the mounting bracket 27 and the front end side middle portion of the arm 22, and the bucket 23 swings (squeezed / squeezed) by the expansion / contraction of the tilt cylinder 28. Dump operation).
The bucket 23 is detachable with respect to the mounting bracket 27. By removing the bucket 23 and attaching various attachments (hydraulic drive work tools) to the mounting bracket 27, various operations other than excavation (or others) Excavation work).

An engine 29 is provided on the rear side on the bottom wall 6 of the body frame 2, and a fuel tank 30 and a hydraulic oil tank 31 are provided on the front side on the bottom wall 6 of the body frame 2.
A hydraulic drive device 32 that drives the left and right traveling motors 21L and 21R is provided in front of the engine 29, and first to third pumps P1, P2, and P3 are provided in front of the hydraulic drive device 32, and the right side of the body frame 2 A control valve 33 (hydraulic control device) for the working device 3 is provided in the middle of the wall 7 in the front-rear direction.
FIG. 3 is a hydraulic circuit diagram of a work system of the work machine.

  As shown in FIG. 3, the first to third pumps P <b> 1, P <b> 2, and P <b> 3 are configured by constant capacity gear pumps that are driven by the power of the engine 29. The first pump P <b> 1 (main pump) is used to drive the hydraulic actuator 34 of the attachment attached to the lift cylinder 26, the tilt cylinder 28 or the tip side of the arm 22. The second pump P2 is mainly used for supplying a control signal pressure. The third pump P3 (sub-pump) is a hydraulic pump 34 for supplying hydraulic oil to the hydraulic actuator 34 when the hydraulic actuator 34 of the hydraulic drive attachment attached to the distal end side of the arm 22 is a hydraulic actuator 34 that requires a large capacity. Used to increase the flow rate.

  Under the operation lever 15, an arm raising pilot valve 40, an arm lowering pilot valve 41, a bucket dump pilot valve 42, and a bucket squeeze pilot valve 43 are arranged. These pilot valves 40, 41, 42, 43 are operated by the operation lever 15. Pressure oil from the second pump P2 can be supplied to each pilot valve 40, 41, 42, 43 of the operation lever 15 by exciting a work lock valve 44 comprising a two-position switching valve of an electromagnetic system. By demagnetizing the lock valve 44, the pressure oil from the second pump P2 cannot be supplied, and the operation lever 15 cannot be operated. For example, a demagnetization signal is sent to the work lock valve 44 by a lock lever operated when the user gets off, and an excitation signal is sent by a release switch.

The control valve 33 for the working device 3 includes an arm control valve 45 that controls the lift cylinder 26, a bucket control valve 46 that controls the tilt cylinder 28, and an attachment hydraulic actuator 34 that is attached to the tip side of the arm 22. And a preliminary control valve 47 (which is referred to as an SP control valve). Each of the control valves 45, 46, 47 is constituted by a pilot type direct acting spool type three-position switching valve.
The arm control valve 45, the bucket control valve 46, and the SP control valve 47 are connected to the working system supply oil passage f connected to the discharge passage e of the first pump P1 from the upstream side. The control valve 46 and the SP control valve 47 are provided in this order, and the hydraulic oil from the first pump P1 is tilted to the lift cylinder 26 via the arm control valve 45 or via the bucket control valve 46. It can be supplied to the cylinder 28 or the hydraulic actuator 34 of the attachment via the SP control valve 47.

The working system supply oil passage f is connected to the drain oil passage g after passing through the SP control valve 47. One end side of the bypass oil passage h is connected to the upstream side of the work system supply oil passage f from the arm control valve 45. The other end side of the bypass oil passage h is connected to the downstream side of the SP control valve 47 of the working system supply oil passage f. The bypass oil passage h is provided with a relief valve 48 for setting the circuit pressure of the working system supply oil passage f.
The operation lever 15 can be tilted from the neutral position in an oblique direction between front and rear, left and right and front and rear, right and left. The pilot valves 40, 41, 42, 43 are operated by tilting the operation lever 15.

The pilot pressure is set in proportion to the operation amount from the neutral position of the operation lever 15, and the set pilot pressure is output from each pilot valve 40, 41, 42, 43.
Specifically, when the operation lever 15 is tilted rearward (in the direction of arrow B1 in FIG. 3), the arm raising pilot valve 40 is operated, and the pilot pressure is output from the pilot valve 40. Acts on one pressure receiving portion of the arm control valve 45 and the control valve 45 is operated, whereby the lift cylinder 26 is extended, and the arm 22 is raised at a speed proportional to the tilting amount of the operation lever 15.

When the operation lever 15 is tilted forward (in the direction of arrow B2 in FIG. 3), the arm lowering pilot valve 41 is operated to output pilot pressure from the pilot valve 41, and the pilot pressure is controlled by the arm control valve 45. When the control valve 45 is operated by acting on the other pressure receiving portion, the lift cylinder 26 is reduced, and the arm 22 is lowered at a speed proportional to the tilting amount of the operation lever 15.
When the operation lever 15 is tilted to the right (in the direction of arrow B3 in FIG. 3), the bucket dump pilot valve 42 is operated to output pilot pressure from the pilot valve 42, and the pilot pressure is used for the bucket. When the control valve 46 is operated by operating on one pressure receiving portion of the control valve 46, the tilt cylinder 28 is extended, and the bucket 23 performs a dumping operation at a speed proportional to the tilting amount of the operation lever 15.

  When the operation lever 15 is tilted to the left (in the direction of arrow B4 in FIG. 3), the bucket squeeze pilot valve 43 is operated and pilot pressure is output from the pilot valve 43, and the pilot pressure is controlled by the bucket control. When the control valve 46 is operated by acting on the other pressure receiving portion of the valve 46, the tilt cylinder 28 is contracted, and the bucket 23 is squeezed at a speed proportional to the tilting amount of the operation lever 15. Further, when the operation lever 15 is tilted in an oblique direction, a combined operation of the raising or lowering operation of the arm 22 and the squeeze or dumping operation of the bucket 23 can be performed.

FIG. 4 is a circuit diagram of a main part of the hydraulic system according to the first embodiment of the present invention.
As shown in FIG. 4, the first port P <b> 1 of the arm control valve 45 is connected to the top-side flow path 51 that reaches the top of the lift cylinder 26 via the first branching portion 50 that branches. A check valve (check valve) 52 is provided in the middle of the top channel 51. The second port P <b> 2 of the arm control valve 45 is connected to a bottom-side flow path 54 that reaches the bottom of the lift cylinder 26 through a second branching portion 53 that branches. The top side flow path 51 and the bottom side flow path 54 communicate with each other via a hydraulic fluid communication path 55.

The hydraulic fluid communication path 55 includes a first communication path 56 and a second communication path 57.
The first communication path 56 branches from the top-side flow path 51 at a third branching portion 59 provided between the check valve 52 of the top-side flow path 51 and the top coupling portion 58 of the lift cylinder 26, and It is configured to reach the first junction 61 via the fourth branch 60.
The second communication path 57 is configured to reach the first junction 61 through the fifth branch 62 from the second branch 53 provided at one end of the bottom channel 54.
That is, one end side of the first communication path 56 is connected to the top-side flow path 51 via the third branch portion 59, and one end side of the second communication path 57 is connected to the bottom side via the second branch portion 53. The other end side of the first communication path 56 and the other end side of the second communication path 57 are connected to each other via the first joining portion 61, and thereby the top side flow path 51 is connected to the flow path 54. It communicates with the bottom channel 54.

A first drain channel d1 is connected to the first junction 61, and a bypass oil path h is connected to the second branch 53. A check valve 49 urged by a spring 49a is provided in the first drain flow path d1.
The hydraulic fluid communication passage 55 is provided with a switching device (sometimes referred to as a float switching device) 65 that opens and closes the hydraulic fluid communication passage 55. That is, on the first communication path 56 and the second communication path 57, a float switching device 65 that opens and closes these is provided.
The float switching device 65 is in an open state to bring the hydraulic fluid communication passage 55 (the first communication passage 56 and the second communication passage 57) into communication, and the bottom side hydraulic fluid and the top side hydraulic fluid of the lift cylinder 26 The lift cylinder 26 can be expanded and contracted regardless of the control of the arm control valve 45. That is, the lift cylinder 26 is freely expanded and contracted by allowing the hydraulic oil to flow through both the first communication path 56 and the second communication path 57 by the opening operation of the float switching device 65, and as a result, the arm 22. Will float.

The float switching device 65 includes a first switching valve 66 provided in the first communication path 56 and switching in two directions, and a second switching valve 67 provided in the second communication path 57 and switching in two directions. .
The first switching valve 66 has a one-way position 66a for flowing hydraulic oil in the first communication path 56 in one direction toward the first junction 61, and a bidirectional position for flowing hydraulic oil in the first communication path 56 in both directions. 66b can be switched to 66b. In a state where pressure oil is not acting on the first pressure receiving path 66c of the first switching valve 66 (the differential pressure between the first pressure receiving path 66c and the second pressure receiving path 66d is substantially the same), the biasing force of the spring 66e The first switching valve 66 is switched to a one-way position 66a, and when a differential pressure is generated in the first pressure receiving path 66c and the second pressure receiving path 66d and pressure oil acts on the first pressure receiving path 66c, the first switching valve 66 is switched to the bidirectional position 66b.

  The second switching valve 67 has a one-way position 67a for flowing the hydraulic oil in the second communication passage 57 in one direction toward the first junction 61, and a bidirectional position for flowing the hydraulic oil in the second communication passage 57 in both directions. It can be switched to 67b. In a state where pressure oil is not acting on the first pressure receiving path 67c of the second switching valve 67 (the differential pressure between the first pressure receiving path 67c and the second pressure receiving path 67d is substantially the same), the biasing force of the spring 67e causes The second switching valve 67 switches to a one-way position 67a, and when a differential pressure is generated between the first pressure receiving path 67c and the second pressure receiving path 67d and pressure oil acts on the first pressure receiving path 67c, the second switching valve 67 switches to the bidirectional position 67b.

When both the first switching valve 66 and the second switching valve 67 are switched in one direction, the hydraulic oil in the first communication passage 56 does not flow to the second switching valve 67 and the second communication valve 56 This is a non-communication state in which the hydraulic oil in the passage 57 does not flow to the first switching valve 66. Hereinafter, for convenience of explanation, this non-communication state is referred to as a closed state of the hydraulic fluid communication passage 55 or a closed state of the float switching device 65.
On the other hand, when both the first switching valve 66 and the second switching valve 67 are switched in both directions, the hydraulic oil in the first communication passage 56 flows to the second switching valve 67 and the second communication valve 56 In this state, the hydraulic oil in the passage 57 flows to the first switching valve 66. Hereinafter, for convenience of explanation, this communication state is referred to as an open state of the hydraulic fluid communication passage 55 or an open state of the float switching device 65.

  The float switching device 65 includes a first operating portion 69 that communicates with the first pressure receiving passage 66 c of the first switching valve 66 and a second operating portion 70 that communicates with the first pressure receiving passage 67 c of the second switching valve 67. The 1st operation part 69 switches between the closed position which makes check valve 69a provided in the closed state closed, and the open position which makes check valve 69a open. Specifically, when the first actuating part 69 has the check valve 69a in the closed position, the first differential pressure between the first pressure receiving path 66c and the second pressure receiving part 66d of the first switching valve 66 is made substantially the same. When the switching valve 66 is switched in one direction and the check valve 69a is in the open position, the hydraulic pressure in the first pressure receiving channel 66c is released to the second drain channel d2 and the first switching valve 66 is switched in both directions.

The 2nd operation part 70 switches between the closed position which makes check valve 70a provided in the closed state closed, and the open position which makes check valve 70a open. More specifically, when the second operating portion 70 has the check valve 70a in the closed position, the second pressure difference between the first pressure receiving passage 67c and the second pressure receiving passage 67d of the second switching valve 67 is made substantially the same. When the switching valve 67 is switched in one direction and the check valve 70a is in the open position, the hydraulic pressure in the first pressure receiving path 67c is released to the second drain flow path d2 and the second switching valve 67 is switched in both directions.
The float switching device 65 includes a first switching actuator 71 that switches the first operating portion 69 between a closed position and an open position, and a second switching actuator 72 that switches the second operating portion 70 between a closed position and an open position. Yes.

The first switching actuator 71 is extended by supplying pilot oil from the pilot oil passage Ps to open the first operating portion 69 and is contracted by draining pilot oil to close the first operating portion 69. Put it in a state.
The second switching actuator 72 extends by supplying pilot oil from the pilot oil passage Ps to open the second operating part 70, and contracts by exhausting pilot oil to close the second operating part 70. To.
The float switching device 65 includes a supply position 73a that supplies pilot oil to the first switching actuator 71 and the second switching actuator 72, and a non-supply position 73b that does not supply pilot oil to the first switching actuator 71 and the second switching actuator 72. A two-way float switching valve 73 is provided.

The float switching valve 73 switches to the supply position 73a by the excitation of the solenoid 73c, extends the first switching actuator 71 to switch the first switching valve 66 to the bidirectional position 66b, and switches to the supply position 73a by the excitation of the solenoid 73c. The second switching actuator 72 is extended to switch the second switching valve 67 to the bidirectional position 67b.
The float switching valve 73 is switched to the non-supply position 73b by the demagnetization of the solenoid 73c, the first switching actuator 71 is contracted to switch the first switching valve 66 to the one-way position 66a, and the non-supply position by the demagnetization of the solenoid 73c. Switching to 73b reduces the second switching actuator 72 to switch the second switching valve 67 to the one-way position 67a.

As described above, according to the float switching device 65, when the float switching valve 73 is set to the supply position 73a, the float switching device 65 is opened and the hydraulic fluid communication passage 55 is communicated. As a result, the lift cylinder 26 can be expanded and contracted regardless of the arm control valve 45, and the arm 22 performs the float operation.
On the other hand, by setting the float switching valve 73 to the non-supply position 73b, the float switching device 65 is closed, and the hydraulic fluid communication path 55 is disconnected. As a result, the lift cylinder 26 is expanded and contracted by the arm control valve 45. In this way, the arm 22 determines whether or not the float operation can be performed by controlling the float switching device 65 to open and close.

The work machine float control system of the present invention includes a controller 75 for controlling opening and closing of the float switching device 65. Hereinafter, the control of the float switching device 65 by the controller 75 and the float operation will be described in detail.
The controller 75 includes a float mode 76 configured by a program or the like. The float mode 76 includes a program for operating the arm 22 to float, and specifically includes various conditions for operating the float switching valve 73 of the float switching device 65. It is a thing.

A float mode switch 78 provided near the driver's seat 13, a pilot first pressure sensor 80, a pilot second pressure sensor 81, and an arm height sensor 83 are connected to the input side of the controller 75. . A float switching valve 73 of the float switching device 65 is connected to the output side of the controller 75.
The float mode switch 78 switches the float mode 76 (program) stored in the controller 75 between valid and invalid. When the float mode switch 78 is turned on, the float mode 76 becomes valid, and the float mode is switched by the float mode 76. The valve 73 can be operated. Further, when the float mode switch 78 is turned OFF, the float mode 76 becomes invalid, and the operation of the float switching valve 73 in the float mode 76 becomes impossible.

The pilot first pressure sensor 80 detects the pilot pressure of the pilot valve 41 for lowering the arm 22. When the pilot pressure is output from the pilot valve 41 and the pilot pressure is detected, the pilot pressure of the lower pilot pressure is detected. A detection signal is input to the controller 75.
The pilot second pressure sensor 81 detects the pilot pressure of the pilot valve 40 for raising the arm 22. When the pilot pressure is output from the pilot valve 40 and the pilot pressure is detected, the pilot pressure of the raised pilot pressure is detected. A detection signal is input to the controller 75.

The arm height sensor 83 is for detecting the height of the arm 22, and for example, the angle of the arm 22 is input to the controller 75. The controller 75 calculates the height of the distal end side of the arm 22 from the angle of the arm 22.
The float control system includes an operation speed detection unit 84 that detects the operation speed of the arm 22. In this embodiment, the operation speed detection unit 84 includes an arm height sensor 83 and an operation speed calculation unit 85 that calculates the operation speed of the arm 22 based on a signal from the arm height sensor 83. . The operation speed calculation unit 85 obtains the operation speed of the arm 22 based on a change in the angle of the arm 22 (angular speed change) input from the arm height sensor 83. As a matter of course, the operation speed is fast when the height change or angle change by the arm height sensor 83 is large, and the operation speed is slow when the height change or angle change by the arm height sensor 83 is small.

The operation speed detecting means 84 may be anything as long as it can obtain the operation speed of the arm 22 and is not limited to the above. For example, the operation speed detection means 84 may be configured by a flow sensor that detects the flow rate of the hydraulic oil flowing through the lift cylinder 26, and the flow rate detected by the flow sensor may be replaced with the operation speed.
Further, the operation speed detecting means 84 is composed of a pilot first pressure sensor 80 and an operation speed calculation unit for obtaining the operation speed of the arm 22 based on the lowered pilot pressure detected from the pilot first pressure sensor 80. The operating speed of the arm 22 may be detected based on a change in the lower pilot pressure.

FIG. 5 is a flowchart of the float operation by the controller 75, that is, the float mode 76 (program).
When the arm 22 is floated, the controller 75 first determines whether or not the float mode 76 is enabled (S1). That is, when the float mode switch 78 is pressed and turned on and the float mode 76 is enabled, the process proceeds to the next process. When the float mode switch 78 is not pressed and is OFF and the float mode 76 is invalid, the arm 22 does not perform the float operation, and the arm 22 is controlled by the operation lever 15. Normal operation (such as vertical movement) is performed.

  The controller 75 determines whether or not the operation lever 15 is operated and the arm 22 is in a lowering operation in a state where the float mode 76 is enabled (S2). That is, after the operator activates the float mode 76, the operator operates the operation lever 15 to lower the arm 22, whereby the pilot pressure detection signal is input to the controller 75 from the pilot first pressure sensor 80. Then, it is determined that the arm 22 is in the lowering operation, and the process proceeds to the next process. On the other hand, in the state where the detection signal of the increased pilot pressure is input from the pilot second pressure sensor 81 to the controller 75, it is not determined that the arm 22 has been lowered.

Then, it is determined whether or not the lowering operation speed of the arm 22 is equal to or higher than a predetermined value (S3). Specifically, if the operating speed of lowering of the arm 22 detected by the operating speed detecting means 84 is equal to or higher than a predetermined value (threshold value), the process proceeds to the next process. Otherwise, the process does not proceed to the next process.
The predetermined value (threshold value) of the lowering operation speed of the arm 22 is preferably a little slower than the operation speed when the arm 22 performs the float operation. Specifically, the predetermined value of the operation speed during the lowering operation of the arm 22 is set to 0.05 m / sec or more, and in this embodiment, is set to 0.25 m / sec. The predetermined value of the operation speed during the lowering operation of the arm 22 is preferably 0.25 m / sec or more.

By doing so, when the operation state is switched from the normal operation state to the float operation, the change in the operation speed of the arm 22 can be reduced, and the arm 22 can be operated smoothly.
Next, it is determined whether or not the height of the tip of the arm 22 is a predetermined value or less (S4). That is, after the arm 22 is lowered, it is determined whether or not the height from the arm height sensor 83 input to the controller 75 is equal to or less than a predetermined value. Specifically, in the float mode 76, when the angle of the arm 22 is input from the arm height sensor 83 to the controller 75 after the arm 22 has been lowered, the height of the tip of the arm 22 is determined from the angle of the arm 22. Then, it is determined whether or not the calculated height of the tip of the arm 22 is equal to or less than a predetermined value.

  Now, when the operator operates the operation lever 15 and lowers the arm 22 gradually, naturally the height of the arm 22 gradually decreases. In this embodiment, the predetermined value (threshold value) of the height of the arm 22 used for the determination of the float operation is set to be slightly higher than the attachment attached to the tip of the arm 22 contacting the ground. Specifically, with the fulcrum pin 22a to which the bucket 23 and the attachment on the tip side of the arm 22 are attached as the tip of the arm 22, the distance (height) between the fulcrum pin 22a serving as a reference and the ground is 1.5 m. Is a predetermined value (threshold value) of the height of the arm 22. The predetermined value of the height of the arm 22 used for determining the float operation is preferably 1.5 m or less, and more preferably, the predetermined value of the height of the arm 22 used for determining the float operation is 1.0 m or less. It is preferable to make it.

If the height of the tip of the arm 22 is equal to or less than a predetermined value (1.5 m or less), the float mode 76 outputs an excitation signal from the controller 75 to the float switching valve 73 (S5). That is, in the float mode 76, when the float mode 76 is in an effective state, the lowering operation speed of the arm 22 is equal to or higher than a predetermined value, and the height of the tip of the arm 22 is equal to or lower than the predetermined value, the float switching device. 65 opening operation (permission of opening operation) is permitted.
Here, in order to cancel the float operation of the arm 22 (stop excitation of the solenoid 73c), the float mode 76 may be disabled by the float mode switch 78. In addition, after the operation lever 15 is operated in the lowering direction of the arm 22 to start the float operation, the operation lever 15 is operated in the reverse direction of the arm 22 and the pilot second pressure sensor 81 detects the increased pilot pressure. Is input to the controller 75, the float mode 76 may cancel the float operation.

  In the float control system for a work machine according to the present invention, the controller 75 includes a float mode 76 for causing the arm 22 to float, and the controller 75 includes the float mode switch 78 for enabling or disabling the float mode 76 and the switching. A float switch 77 for operating the apparatus is connected, and in the float mode 76, the arm 22 descends at an operating speed equal to or higher than a predetermined value in the enabled state, and the height of the tip of the arm 22 is equal to or lower than a predetermined value. When this happens, the float switching device 65 is automatically operated so that the arm 22 floats.

According to this, the arm 22 is lowered in a very stable state, and the float operation can be started when the tip end side of the arm 22 becomes sufficiently low. Therefore, the normal operation state is changed to the float operation. Transition can be done smoothly.
The present invention is not limited to the above embodiment. That is, in the present invention, the determination for entering the float operation includes the condition that the height of the tip of the arm 22 is not more than a predetermined value and the condition that the operation speed of the arm is not less than a predetermined value. In each embodiment, the order of the conditions (processing procedure) is not limited to the above embodiment, and may be switched.

It is the whole working machine side view. It is side surface sectional drawing of the working machine of the state which raised the cabin. It is a circuit diagram of the hydraulic system of a working system. It is a circuit diagram of the principal part of the hydraulic system concerning the present invention. It is a flowchart of a float operation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Work implement 22 Arm 26 Lift cylinder 75 Controller 76 Float mode 78 Float mode switch 80 1st pressure sensor 81 2nd pressure sensor 83 Arm height sensor 84 Motion speed detection means 85 Motion speed calculation part

Claims (2)

An arm that is supported by the machine frame so that it can swing up and down and has an attachment that can be attached to and detached from the tip side, an arm hydraulic actuator that operates the arm with hydraulic oil, and the flow rate of hydraulic oil that is supplied to the hydraulic actuator for the arm are controlled. A control valve for the arm to be operated, a hydraulic fluid communication path communicating the bottom hydraulic pressure supply path of the hydraulic actuator for the arm and a top hydraulic pressure supply path of the hydraulic actuator for the arm, and the operation provided on the hydraulic fluid communication path A switching device that opens and closes the oil communication passage; and a controller that can control the switching device to float the arm by communicating the hydraulic fluid communication passage with the switching device open.
A float mode switch for enabling or disabling the float mode is connected to the controller. The float mode of the controller is such that the arm descends at an operating speed equal to or higher than a predetermined value, and the height of the tip of the arm is predetermined. A float control system for a working machine, wherein the switching device is operated so that the arm floats when the value becomes lower than the value.   A sensor for detecting an arm angle is connected to the controller, and the float mode calculates the height of the arm based on the arm angle detected by the sensor and detects the operating speed of the arm based on the angular speed of the arm angle. The work machine float control system according to claim 1.

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