WORK MACHINE

Abstract

A work machine having: a working part; a holding part for holding the working part; and an operating part for rotating the working part around the holding part; further comprising: an angle sensing means for sensing the angle of the working part from the horizontal; and a controller for adjusting and holding the position of the working part by use of the operation means based on the angle sensing means.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a work machine, such as an agricultural machine or a construction machine, having a bucket, booms supporting the bucket, and dump cylinders for rotating the bucket around the booms.

2. Description of the Relate Art

In conventional work machines having a working part such as a bucket, an operator operates the bucket by use of a bucket control lever. In other words, the bucket is operated by the operator manually. Therefore, during operation, it is difficult for the operator to recognize the exact angular position of the bucket. To address this problem, patent publications, such as WO2002/040783 and U.S. Pat. No. 5,887,365 have disclosed new methods. These inventions have a control unit that controls automatic bucket operation, and the control unit recognizes the angular position of the bucket. Then, the control unit adjusts the bucket position according to a target slope angle and a target depth of excavation.

Problem to be Solved by the Invention

During excavation work, it is sometimes necessary to keep a loaded bucket level. However, it is difficult for an unskilled operator (a driver) to do so. The two above-mentioned patent publications do not present the solution for this problem. Therefore, this invention offers a work machine, which is able to keep a loaded bucket level easily.

SUMMARY OF THE INVENTION

Means to Solve the Problem

A work machine having: a working part; a holding part for holding the working part; and an operating part for rotating the working part around the holding part; further comprising: an angle sensing means for sensing the angle of the working part from the horizontal; and a controller for adjusting and holding the position of the working part by use of the operation means based on the angle sensing means.

In one embodiment, the invention may offer the work machine wherein the angle sensing means is installed on the working part.

In one embodiment, the invention may offer the work machine wherein the angle sensing means is installed on the back part of the working part.

In one embodiment, the invention may offer the work machine wherein the angle sensing means is installed on the side part of the working part.

In one embodiment, the invention may offer the work machine further comprising: a driver's seat for the operator, a working part control lever installed at the side of the driver's seat, for turning the working part around by the operator, and an angle control switch equipped on the working part control lever, for starting adjusting and holding the working part to a target angular position.

Advantages of the Invention

The invention offers a work machine having: a working part; a holding part for holding the working part; and an operating part for rotating the working part around the holding part;

further comprising: an angle sensing means for sensing the angle of the working part from the horizontal; and a controller for adjusting and holding the position of the working part by use of the operation means based on the angle sensing means. Therefore, the bucket can be easily kept level by even an unskilled operator (a driver).

In one embodiment, the invention offers the work machine wherein the angle sensing means is installed on the working part. Therefore, the angle position of the working part can be easily sensed by the angle sensing means.

In one embodiment, the invention offers the work machine wherein the angle sensing means is installed on the back part of the working part. Therefore, the angle position of the working part can be easily sensed by the angle sensing means.

In one embodiment, the invention offers the work machine wherein the angle sensing means is installed on the side part of the working part. Therefore, the angle position of the working part can be easily sensed by the angle sensing means.

In one embodiment, the invention offers the work machine further comprising: a driver's seat for the operator, a working part control lever installed at the side of the driver's seat, for turning the working part around by the operator, and an angle control switch equipped on the working part control lever, for starting adjusting and holding the working part to a target angular position. Therefore, the working part angle control can be easily operated with the working part control lever while the working part is operated.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] A front perspective view of a tractor (a work machine) with a front loader as a first embodiment of the invention.

[FIG. 2] (a) is a back view of the bucket, (b) is a side view from “B” in (a), (c) is a side view of the hitch, and (d) is a section view from “X” in (c).

[FIG. 3] (a) is a front view of the boom control lever and the bucket control lever, (b) is a side view of the bucket control lever from “A” in (a), (c) is a side view of the boom control lever from “A” in (a).

[FIG. 4] A hydraulic circuit in the first embodiment.

[FIG. 5] A block diagram of the main part.

[FIG. 6] A flow chart of the automatic bucket level control process.

[FIG. 7] (a) is a back view of the bucket, (b) is a side view from “C” in (a).

[FIG. 8] A front perspective view of the main features of a tractor (a work machine).

[FIG. 9] (a) is a front view of the boom-bucket control lever, (b) is a plane view of (a), (c) is a right-side view of the boom-bucket control lever, (d) is a front view of the boom-bucket control lever.

[FIG. 10] A hydraulic circuit.

[FIG. 11] A block diagram of the main part.

DETAILED DESCRIPTION OF THE INVENTION

Best Mode of Embodying the Invention

The best mode of embodying the invention is described below with reference to specific figures. FIG. 1 shows a front perspective view of the tractor 10 (a work machine). The tractor 10 is composed of front tires 14, rear tires 15 and a front loader 16. In this specification, ‘front’ is defined as the direction when the tractor 10 is going forward, and ‘back’ as the direction when the tractor 10 is going backward. Furthermore, ‘left’ is defined as the left side when the tractor 10 is going forward, and ‘right’ is defined as the right side when the tractor 10 is going forward.

A hood 12 is put in the front part of the tractor 10. A tank of gas and an engine (not illustrated) are installed under the hood 12. A frame 41 is put in the lower part of the tractor 10, and the engine is mounted on the frame 41. The power of the engine is transmitted to front tires 14 and rear tires 15 through a transmission (not illustrated). The power of the engine is also used for a hydraulic pump, which is described below.

A driver's seat 17, on which a driver sits when operating the tractor 10, is at the rear part of the tractor 10. A steering wheel 18, a monitor (not illustrated) etc. are in front of the driver's seat 17. The monitor is to show driving speed, fuel level, etc. and also to give an alarm when a tilt sensor (described below) is not working. A bucket control lever (a working part control lever) 19 and a boom control lever 20 are installed at the right side of the driver's seat 17. A transmission (not illustrated) for changing gears of the tractor 10 is under the driver's seat 17.

A floor 13 is installed in front of the driver's seat 17. The floor 13 is composed of a pair of plane parts of the floor 13a and a projection part of the floor 13b. The two plane parts of the floor 13a are made plane and board-like. The projection part of the floor 13b is installed between the two plane parts of the floor 13a. The projection part of the floor 13b and the two plane parts of the floor 13a are coupled with each other by bolts etc. The projection part of the floor 13b bends upward, and a driving shaft, which transmits power from the engine to the transmission, is located under the projection part of the floor 13b.

Fenders F are mounted on both sides of the driver's seat 17. The bucket control lever 19 and the boom control lever 20 are at the fender F at the right side of the driver's seat 17. A Rollover Protective Structure (ROPS) R, which is an arch-like safety protective frame, is almost vertically installed at the rear part of the fenders F.

A boom holding mechanism 40 for holding the front loader 16 is installed on both sides and in the middle of the tractor 10.

The front loader 16 is detachable from the tractor 10. The front loader 16 is composed of a pair of booms (a support part) 21 set up at both sides of the tractor 10, a pair of lift cylinders 23 located at both sides of the main body of the tractor 10, a bucket (working part) 26 and a pair of dump cylinders (operating part) 24. The lift cylinders 23 are to move the boom 21 up and down. The bucket 26 is coupled with the top of the two booms 21. The dump cylinders 24 are to turn the bucket 26 around the top of the booms 21. The lift cylinders 23 and the dump cylinders 24 are connected with a hydraulic circuit. This hydraulic circuit is to operate the lift cylinders 23 and the dump cylinders 24 by hydraulic pumps, which work by the power from the engine.

The booms 21 are shaped as an arc and stretch out toward the front of the tractor 10. The bottom of each of the booms 21 is coupled with the upper section of the boom holding mechanism 40, and the two booms 21 (which are located at both sides of the main body of the tractor 10) are rotatable around the boom holding mechanism 40. The bucket 26, on the other hand, is coupled with the two booms 21 by a hitch (a connection part) 25. The hitch 25 is detachable from the bucket 26, and is rotatable around the top of the booms 21. A cylinder bracket 27 is welded at the middle section of each boom 21. The cylinder bracket 27 is set upward from the boom 21 in its front part, whereas it is set downward from the boom 21 in its rear part.

The bucket 26 is made of metal. It is comprised of a bottom part 26bt, a pair of side parts 26s, a rear part 26bk, a back part 26b and a top part 26u. The side parts 26s are vertically installed at both ends of the bottom part 26bt. The rear part 26bk is connected to the pair of side parts 26s at both of its ends. The back part 26b is connected to the rear part 26bk, and it is also connected to the pair of side parts 26s at both of its ends. A pair of stays 26A is put on the rear part 26b. A hook bar 26B is fixed to the pair of stays 26A at its both ends. A tilt sensor (an angle sensing means) TS is equipped on the right side part 26s. Alternatively, the tilt sensor TS may be equipped on the left side part 26s. The tilt sensor TS senses the angle position of the bucket 26 from the horizontal; in other words, it senses the angle between an upper edge 26su of the side part 26s and the horizontal. Alternatively, the tilt sensor TS may sense the angle position of the bucket 26 from the vertical. The tilt sensor TS is connected to a controller (later described).

The hitch 25 is comprised of a pair of trapezoidal metal plates. Each boom 21 is held at its top between the two metal plates and is rotatable at Pin P. Each dump cylinder 24 is also held at its top between the two metal plates and is rotatable at this point. Pin P is called a rotation center of the hitch 25 and the bucket 26. A holding part 25A is made at the top edge of the hitch 25. The holding part 25A is made by cutting the hitch 25 in a half circle shape. The holding part 25A holds a hook part 26B of the bucket 26. Therefore, the bucket 26 is connected to the hitch 25 via the holding part 25A. A pair of stays 26A is made of a rectangular metal plate and is fixed on the rear part 26bk of the bucket 26.

Other attachments instead of the bucket 26 can also be attached to the hitch 25. A harness, which connects between the tilt sensor TS and the above-mentioned controller, has a connecter. The harness can be disconnected from the bucket 26 at said connecter when the bucket 26 is detached. When another attachment is attached to the hitch 25, the harness is to be connected to the attachment with the connecter. A swing sensor or a gyro sensor can be installed in the bucket 26 instead of the tilt sensor TS.

The bottom of the lift cylinder 23 is coupled with the boom holding mechanism 40 and is rotatable at the boom holding mechanism 40. The top of the lift cylinder 23 is, on the other hand, connected to the back part of the cylinder bracket 27 and is rotatable at the cylinder bracket 27. Each lift cylinder 23 is installed underneath and parallel to each boom 21.

The dump cylinder 24 is connected to the front part of the cylinder bracket 27 and is rotatable at the cylinder bracket 27. On the other hand, the top of the dump cylinder 24 is coupled with the top of the hitch 25 and is rotatable at the hitch 25. Each dump cylinder 24 is installed over each boom 21.

Therefore, the booms 21 go up (or rotate upward) when the lift cylinders 23 stretch out, whereas the booms 21 go down (or rotate downward) when the lift cylinders 23 shrink. On the other hand, the bucket 26 turns upward when the dump cylinders 24 shrink, whereas the bucket 26 turns downward when the dump cylinders 24 stretch out.

The bucket control lever 18 and the boom control lever 20 are illustrated in FIG. 3(a) to FIG. 3(c), and the hydraulic circuit is illustrated in FIG. 4. The bucket control lever 19 is to operate the dump cylinders 24 of the front loader 16. The bucket control lever 19 consists of a grip 19a, a rod 19b and a protection part 19c. The grip 19a is made of resin and shaped by an injection molder. The lower part of the rod 19b is held inside the right fender F. The protection part 19c covers the gap between the rod 19b and the fender F in order to prevent dust from coming inside the fender F. The protection part 19c is made of a flexible material to enable it to follow the movement of the rod 19b. The bucket control lever 19 is connected to a selector valve 50. The selector valve 50 changes position when the bucket control lever 19 is turned.

More specifically, when the bucket control lever 19 is turned toward the D direction, the selector valve 50 moves to the D position (DOWN position). When the bucket control lever 19 is turned toward the U direction, the selector valve 50 moves to the U position (UP position). The bucket control lever 19 is always in the N position (neutral) by coil springs (not illustrated) whenever it is not operated. Operation buttons B1, B2 are installed on the front side of the bucket control lever 19. Furthermore, operation buttons B1, B2 project from the front side of the bucket control lever 19. An operation button B3 is installed on the upper side of the bucket control lever 19. Furthermore, the operation button B3 projects from the upper side of the bucket control lever 19. Each operation button B1, B2, B3 is made of resin and is a column with a dome-like tip. The back of the operation buttons B1, B2, B3 are flat. The actuator of each switch (the switch is a push-plunger type limit switch with the actuator) touches the back of the operation buttons B1, B2 and B3, respectively.

Three switches of the operation buttons B1, B2, B3 are respectively connected to the controller (described later). The solenoid valve SL is moved to the position U when the operation button B1 is pressed. On the other hand, the solenoid valve SL is moved to the position D when the operation button B2 is pressed. The automatic bucket level control for the bucket 26 starts when the operation button (an angle control switch) B3 is pressed (and then the switch is ON). The automatic bucket level control for the bucket 26 ends when the operation button (an angle control switch) B3 is pressed again (and then the switch is OFF).

The boom control lever 20 is to operate the lift cylinders 23. The boom control lever 20 consists of a grip 20a, a rod 20b and a protection part 20c. The grip 20a is made of resin and shaped by an injection molder. The lower part of the rod 20b is held inside the right fender F. The protection part 20c covers the gap between the rod 20b and the fender F in order to prevent dust from entering the fender F. The protection part 20c is made of a flexible material to enable it to follow the movement of the rod 20b. The boom control lever 20 is connected to a selector valve 51. The selector valve 51 changes position when the boom control lever 20 is turned.

More specifically, when the boom control lever 20 is turned toward the D direction, the selector valve 51 moves to the D position (DOWN position). When the boom control lever 20 is turned toward the U direction, the selector valve 51 moves to the U position (UP position). The boom control lever 20 is always in the N position (neutral) by coil springs (not illustrated) whenever it is not operated.

The hydraulic circuit is connected to the hydraulic fluid tank (not illustrated). The hydraulic fluid can move with a constant pressure between the hydraulic fluid tank and the dump cylinders 24 when the bucket control lever 19 is in operation. The hydraulic fluid can move with a constant pressure between the hydraulic fluid tank and the boom cylinders 23 when the boom control lever 20 is in operation. The dump cylinders 24 expand when the bucket control lever 19 is turned toward the D direction. On the other hand, the dump cylinders 24 shrink when the bucket control lever 19 is turned toward the U direction. The lift cylinders 23 shrink when the boom control lever 20 is turned toward the D direction. On the other hand, the lift cylinders 23 expand when the boom control lever 20 is turned toward the U direction.

The procedure for operating the front loader 16 by use of the bucket control lever 19 and the boom control lever 20 is described as follows: In order to move the booms 21 upward, turn the boom control lever 20 toward the operator's side (the U direction). The selector valve 51 moves toward the U position. Then, the hydraulic circuit of the lift cylinders 23 is opened to expand the lift cylinders 23. In order to stop moving the booms 21 upward, release your hand from the boom control lever 20. The boom control lever 20 returns to the N position and the selector valve 51 moves toward the N position to close the hydraulic circuit of the lift cylinders 23.

In order to move the booms 21 downward, turn the boom control lever 20 frontward (the D direction). The selector valve 51 moves toward the D direction. Then, the hydraulic circuit of the lift cylinders 23 is opened to shrink the lift cylinders 23. In order to stop moving the booms 21 downward, release your hand from the boom control lever 20. The boom control lever 20 returns to the N position, and the selector valve 51 moves toward the N position for closing the hydraulic circuit of the lift cylinders 23.

In order to move the bucket 26 upward, turn the bucket control lever 19 backward (the U direction). The selector valve 50 moves toward the U direction. Then, the hydraulic circuit of the dump cylinders 24 is opened to shrink the dump cylinders 24. In order to stop moving the bucket 26 upward, release your hand from the bucket control lever 19. The bucket control lever 19 returns to the N position, and the selector valve 50 moves toward the N position for closing the hydraulic circuit of the dump cylinders 24.

In order to move the bucket 26 downward, turn the bucket control lever 19 frontward (the D direction). The selector valve 50 moves toward the D direction. Then, the hydraulic circuit of the dump cylinders 24 is opened to expand the dump cylinders 24. In order to stop moving the bucket 26 downward, release your hand from the bucket control lever 19. The bucket control lever 19 returns to the N position and the selector valve 50 moves toward the N position to close the hydraulic circuit of the dump cylinders 24.

The bucket 26 can also be operated upwardly or downwardly by the operation buttons B1 and B2, respectively. The solenoid valve SL moves toward the U position when the operation button B1 is pressed while the bucket control lever 19 is in the N position. The solenoid valve SL moves back to the N position when your hand is released from the operation button B1. The solenoid valve SL moves toward the D position when the operation button B2 is pressed while the bucket control lever 19 is in the N position. The solenoid valve SL moves back to the N position when your hand is released from the operation button B2. The controller (described later) is in between the operation buttons B1, B2 and the solenoid valve SL. The solenoid valve SL is moved by the controller.

FIG. 5 shows the main block diagram of this embodiment (the engine is described as “E”). The controller (a control part) CT, which is inside a dashboard in front of the driver's seat 17, is connected with the operation buttons B1, B2, B3. The controller CT is also connected with the tilt sensor TS. Furthermore, the controller CT is connected to the solenoid valve SL and operates it.

The controller CT is able to conduct the automatic bucket level control process for the bucket 26, which keeps the bucket 26 level. FIG. 6 shows the automatic bucket level control program flow chart for the controller CT. The controller CT periodically senses if the tilt sensor TS is working (STEP1). If the tilt sensor TS is not working, the controller CT gives an alarm on the display, which is installed in front of the driver's seat 17 (STEP2). If the tilt sensor TS is working, the controller CT program proceeds to STEP3 and the controller CT senses if the operation button (the automatic level control button) B3 is ON. If the operation button B3 is OFF, then, the controller CT program proceeds to STEP4 and the controller CT ends the automatic level control program (or the controller CT does not start the program). If the operation button B3 is ON, then the controller CT program proceeds to STEP5 and the controller CT starts the automatic level control program.

Furthermore, at STEP6, the controller CT periodically senses if the bucket 26 is level via the tilt sensor (an angle sensing means) TS. If the bucket 26 is level, the controller CT program goes back to STEP3. If the bucket 26 is not level, the controller CT program goes to STEP7 and the controller CT senses if the upper edge 26su of the bucket 26 is turning more than the level (the horizontal) or, in other words, the upper edge 26su is turning backward (toward the driver' seat 17) more than the level. If the upper edge 26su is turning more than the level, the controller CT moves the solenoid valve SL toward the DOWN position to expand the dump cylinder 24 (STEPS). If the upper edge 26su is not turning more than the level, the controller CT program proceeds to STEPS and the controller CT senses if the upper edge 26su is turning less than the level. If the upper edge 26su is not turning less than the level, the controller CT program goes back to STEP1. If the upper edge 26su is turning less than the level (the horizontal), the controller CT moves the solenoid valve SL toward the UP position for shrinking the dump cylinder 24 (STEP10).

The automatic level control precedes the bucket manual operation with the operation buttons B1, B2.

The automatic level control program in this embodiment can be applied not only to the horizontal control of the bucket but also angle control of the bucket in any plane—it is called an automatic angle control program. In such cases, an angle set dial, which is connected to the operation button B3, should be set on the bucket control lever 19 in order to automatically control the bucket angle with respect to the level. In addition, the target angle of the bucket 26 may be input through a touch screen display.

Further Embodiment 1

FIG. 7 shows a further embodiment of this invention. In this embodiment, a tilt sensor TS1 is installed on the rear part 26bk of the bucket 26. Other components of the tractor 10 are not described as they are the same as the previous embodiment.

The bucket 26 is made of metal. It is comprised of a bottom part 26bt, a pair of side parts 26s, a rear part 26bk, a back part 26b and a top part 26u. The side parts 26s are vertically installed at both ends of the bottom part 26bt. The rear part 26bk is connected to the side parts 26s at both of its ends. The back part 26b is connected to the rear part 26bk and is also connected to the pair of side parts 26s at both of its ends. A pair of stays 26A is put on the rear part 26b. A hook bar 26B is fixed to the pair of stays 26A at both of its ends. A tilt sensor (an angle detection means) TS1 is equipped underneath the hook bar 26B. Alternatively, the tilt sensor TS1 may be equipped on the top part 26u or the back part. The tilt sensor TS1 is to sense the angle position of the bucket 26 from the horizontal; however, the tilt sensor TS1 may sense the angular position of the bucket 26 from the vertical, instead. The tilt sensor TS1 is connected to a controller CT with a harness.

The automatic bucket level control process, which gives an automatic level control for the bucket 26, is the same as the previous embodiment shown in FIG. 6. If the tilt sensor is installed on the side part 26s, as described in the previous embodiment, the tilt sensor might be broken by sand or rocks when the tractor 10 digs. However, if the tilt sensor TS1 is installed on the rear part 26bk (or the upper part 26u, the back part 26b), the risk of the tilt sensor TS1 being broken unexpectedly as just described can be reduced.

Further Embodiment 2

Another embodiment of this invention is shown in FIG. 8 to FIG. 11. In this embodiment, a boom-bucket control lever JS is introduced instead of the bucket control lever 19 and the boom control lever 20. In this embodiment, the boom-bucket control lever JS has two functions: a bucket control function and a boom control function. The boom-bucket control lever JS is positioned on the fender F. Other components of the tractor 10 are the same as the first embodiment. When the boom-bucket control lever JS is turned frontward or backward (BD-BU direction in FIG. 9), the selector valve 51 is operated and the booms 21 are turned. On the other hand, when the boom-bucket control lever JS is turned left-sideward or right-sideward (AU-AD direction in FIG. 9), the selector valve 50 is operated and the bucket 26 is turned. Operation buttons B1, B2 are installed on the front side of the boom-bucket control lever JS. Furthermore, operation buttons B1, B2 project from the front side of the boom-bucket control lever JS. An operation button B3 is installed on the upper side of the boom-bucket control lever JS. Furthermore, the operation button B3 projects from the upper side of the boom-bucket control lever JS.

The hydraulic circuit is connected to the hydraulic fluid tank (not illustrated). The hydraulic fluid can move with a constant pressure between the hydraulic fluid tank and the dump cylinders 24 when the boom-bucket control lever JS is in operation. The hydraulic fluid can move with a constant pressure between the hydraulic fluid tank and the boom cylinders 23 when the boom-bucket control lever JS is in operation. The dump cylinders 24 expand when the boom-bucket control lever JS is turned toward the AD direction. On the other hand, the dump cylinders 24 shrink when the boom-bucket control lever JS is turned toward the AU direction. The lift cylinders 23 shrink when the boom-bucket control lever JS is turned toward the BD direction. On the other hand, the lift cylinders 23 expand when the boom-bucket control lever JS is turned toward the BU direction.

The procedure for operating the front loader 16 by use of the boom-bucket control lever JS is described as follows: in order to move the booms 21 upward, turn the boom-bucket control lever JS backward (the BU direction). The selector valve 51 moves toward the BU position. Then, the hydraulic circuit of the lift cylinders 23 is opened to expand the lift cylinders 23. In order to stop moving the booms 21 upward, release your hand from the boom-bucket control lever JS. The boom-bucket control lever JS returns to the N position and the selector valve 51 moves toward the N position to close the hydraulic circuit of the lift cylinders 23.

In order to move the booms 21 downward, turn the boom-bucket control lever JS forward (the BD direction). The selector valve 51 moves toward the BD direction. Then, the hydraulic circuit of the lift cylinders 23 is opened to shrink the lift cylinders 23. In order to stop moving the booms 21 downward, release your hand from the boom-bucket control lever JS. The boom-bucket control lever JS returns to the N position, and the selector valve 51 moves toward the N position for closing the hydraulic circuit of the lift cylinders 23.

In order to move the bucket 26 upward, turn the boom-bucket control lever JS left-sideward (the AU direction). The selector valve 50 moves toward the AU direction. Then, the hydraulic circuit of the dump cylinders 24 is opened to shrink the dump cylinders 24. In order to stop moving the bucket 26 upward, release your hand from the boom-bucket control lever JS. The boom-bucket control lever JS returns to the N position, and the selector valve 50 moves toward the N position for closing the hydraulic circuit of the dump cylinders 24.

In order to move the bucket 26 downward, turn the boom-bucket control lever JS right-sideward (the AD direction). The selector valve 50 moves toward the AD direction. Then, the hydraulic circuit of the dump cylinders 24 is opened to expand the dump cylinders 24. In order to stop moving the bucket 26 downward, release your hand from the boom-bucket control lever JS. The boom-bucket control lever JS returns to the N position and the selector valve 50 moves toward the N position to close the hydraulic circuit of the dump cylinders 24.

As with the previous embodiments, the bucket 26 can also be operated upwardly or downwardly by the operation buttons B1 and B2, respectively. The solenoid valve SL moves toward the U position when the operation button B1 is pressed while the boom-bucket control lever JS is in the N position. The solenoid valve SL moves back to the N position when your hand is released from the operation button B1. The solenoid valve SL moves toward the D position when the operation button B2 is pressed while the boom-bucket control lever JS is in the N position. The solenoid valve SL moves back to the N position when your hand is released from the operation button B2. The controller CT is in between the operation buttons B1, B2 and the solenoid valve SL. The solenoid valve SL is moved by the controller CT. The automatic bucket level control program flow chart shown in FIG. 6 applies to this embodiment.

Claims

1. A work machine having:

a working part;

a holding part for holding the working part; and

an operating part for rotating the working part around the holding part; further comprising:

an angle sensing means for sensing the angle of the working part from the horizontal; and

a controller for adjusting and holding the position of the working part by use of the operation means based on the angle sensing means.

2. The work machine as set forth in claim 1 wherein the angle sensing means is installed on the working part.

3. The work machine as set forth in claim 1 wherein the angle sensing means is installed on the back part of the working part.

4. The work machine as set forth in claim 1 wherein the angle sensing means is installed on the side part of the working part.

5. The work machine as set forth in claim 1, further comprising:

a driver's seat for the operator,

a working part control lever installed at the side of the driver's seat, for turning the working part around by the operator, and

an angle control switch equipped on the working part control lever, for starting adjusting and holding the working part to a target angular position.