JPH0458856B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a boom lowering speed control device for controlling the working posture of a front loader.

(Prior Art) A front loader, which is attached to a tractor body and performs work, has a boom pivotably supported on the tractor body so as to be able to rise and fall freely, and a working tool such as a bucket is rotatably attached to the tip of the boom. A solenoid valve corresponding to each cylinder is installed in the hydraulic circuit of the boom cylinder and bucket cylinder that operate these booms and buckets, and these solenoid valves raise and lower the boom and rotate the bucket in the scooping and dumping directions. I try to control it.

In this type of front loader, when scooping up earth and sand, it is necessary to ground the bottom of the bucket in a horizontal state. Therefore, the target posture is set in advance so that the bottom surface of the bucket is horizontal, and when the boom is lowered, the posture of the bucket is detected and
There is one that controls the attitude of the bucket tote so that it has a target attitude, so that the bottom surface of the bucket is in a horizontal state when it touches the ground.

(Problems to be Solved by the Invention) However, in the past, attitude control was performed independently on the bucket cart side regardless of the descending speed of the boom, so there were cases where the bucket cart could not reliably land on the ground with the bottom horizontal.

In other words, when lowering the boom from a sufficiently high position, or when the bucket does not deviate significantly from the target attitude (bottom horizontal) even if the boom is not high enough,
It is possible to control the attitude of the bucket to make the bottom horizontal during the lowering operation of the boom, but if the boom is at a low position, due to the responsiveness of the bucket tot control system, the bottom will be horizontal by the time the bucket touches the ground. You may not be able to correct your posture.

Therefore, if the bottom of the bucket is not level at a certain boom height, sequential control may be considered in which the lowering operation of the boom is electrically stopped and the bottom is lowered again after the bottom of the bucket is horizontal.

However, in this case, it would be unnatural for the boom to stop mid-way even though the operator is operating the control lever in the downward direction, and a shock when the boom stops is also expected. Therefore, it is ideal to allow the bucket to touch the ground with the bottom horizontal as much as possible without stopping the boom's lowering movement midway through.

SUMMARY OF THE INVENTION In view of these conventional problems, an object of the present invention is to enable a work tool such as a bucket to be controlled to a predetermined target posture without stopping the boom in the middle of its lowering operation.

(Means for Solving the Problems) The present invention raises and lowers the boom at an operating speed proportional to the command signal for raising and lowering the boom, and detects the attitude of the work implement at the tip of the boom when lowering the boom. In a front loader work tool attitude control device that controls the work tool so that it has a target attitude, the deviation between the target attitude signal of the work tool and the detection signal is determined, and the deviation signal is calculated from the boom lowering command signal. The boom is lowered at an operating speed proportional to the signal pulled.

(Function) [1] Manual control When performing manual control, keep the holding switch 32 of the operating lever 26 in the OFF position and press the operating lever 26.
All you need to do is to operate this operating lever 26.
By operating in the direction of the arrow shown in the figure, the boom 10 can be raised and lowered, the bucket 13 can be dumped and scooped, and a complex operation combining these can be performed (see Figure 10). In addition, operation lever 2
6 automatically returns to the central stop position when you release your hand.

Now, when the operating lever 26 is rotated toward the left scooping side during the scooping operation of the bucket 13, the second potentiometer 28 is actuated via the horizontal shaft 31, and the resistance value is set according to the amount of operation. changes, and the voltage of the command signal becomes smaller. here,
It is assumed that the resistance value of the second potentiometer 28 becomes 1/2 at the stop point where the operating lever 26 is at the neutral stop position, and the voltage at that time becomes 1/2 of the supply voltage V. This is called the neutral point. The command signal from the second potentiometer 28 is transmitted to the second determining means 4.
Since it is smaller than the neutral point, the comparison unit 51 determines that it is a scoop command and outputs a scoop signal, and the analog switch 69 of the second drive means 65 is turned on. . On the other hand, the command signal from the second potentiometer 28 is input to each comparing section 58, 59 of the second comparing means 57, and is compared with the triangular wave signal from the triangular wave oscillating means 53. In this case, since the command signal is smaller than the neutral point, the comparison section 59 of the second comparison means 57 compares the two, and turns on when the command signal is smaller than the triangular wave signal, contrary to FIG. A pulse signal is generated by the comparator 59. The larger the deviation between the two, the wider the pulse width of the pulse signal becomes. Therefore, the switching element 67 repeats the on/off operation by the pulse signal via the analog switch 69 of the second driving means 65. Excitation current flows intermittently to the scoop solenoid 44 of the second electromagnetic valve 42 . As a result, the scoop solenoid 44 repeats excitation and demagnetization in synchronization with the pulse signal, so the second solenoid valve 42 switches to the upward side with an opening proportional to the excitation and demagnetization, and the bucketed cylinder 1
4 moves in the contraction direction at a predetermined speed, causing the bucket 13 to move around the pivot 12.
Therefore, by changing the amount of operation of the operation lever 26, the opening degree of the second solenoid valve 42 changes, and the flow rate to the bucket cylinder 14 changes, so that the flow rate changes proportionally according to the amount of operation of the operation lever 26. The bucket 13 rises at a certain speed, and can be controlled at any speed from high speed to slow speed. Then, when the operating lever 26 is returned to the neutral stop position, the second solenoid valve 42 returns to the neutral position, and the bucket 13 stops. At this time, if the operating lever 26 is gradually returned, the bucket 13 will stop slowly and smoothly.

This also applies when operating the operating lever 26 to the right to dump the bucket 13, and when operating the operating lever 26 to the front and back to raise or lower the boom 10.

When the operating lever 26 is operated to the maximum in the front-back direction, the switches 34 to 37 are operated by the actuating section 33, and the corresponding solenoids 40, 4 are operated.
Since current flows through 1, 43, and 44, solenoid valve 3
9,42 works. This allows the solenoid valves 39, 42 to be operated without going through the control system. However, in this case, proportional control is not possible, and therefore, it is only necessary to use it in the event of a failure.

[2] Automatic control During automatic control, when the holding switch 32 is turned on, the analog switch 77 is turned off and the analog switches 78 and 85 are turned on, and the deviation detection means 75 detects the second discrimination means 49 and the second
The deviation detecting means 75 and 86 and the reversing section 80 are connected to the comparing means 57 and the like, and the first determining means 4
5. Since it is connected to the first comparison means 54 etc., automatic control is possible.

In this case, the attitude sensor 16 that detects the attitude of the bucket 13 is used, but the relationship between the attitude sensor 16 and the attitude of the bucket during scooping, horizontal elevation of the opening surface, horizontal elevation of the bottom surface, and dumping is
It will look like A to D in Figure 1. Further, the relationship between the posture sensor 16 and the voltage when the bottom surface is horizontally raised and lowered and the opening surface is horizontally raised and lowered is as shown in FIG.

Each operation will be explained below in the order of horizontal bottom surface, horizontal horizontal opening surface, posture maintenance, and bottom surface grounding.

() Bottom horizontal control First, use the selection switch 72 to select the bottom horizontal voltage Vr ₁ . Here, when the bottom surface of the bucket 13 is parallel to the horizontal line, the voltage (resistance) of the attitude sensor 16 is always constant, and the attitude of the boom 10 is
It has nothing to do with the attitude of the tractor body 1. Therefore, the potentiometer in the setting means 70 is set so that the voltage at this time becomes the bottom horizontal voltage Vr ₁ .
Set the settings as shown in Figure 2.

When the selection switch 72 is set to the bottom horizontal side,
The voltage Vr ₁ is inverted by the inverter 74 around the 1/2V voltage at the N terminal to become the voltage Vr ₁ '. Then, the first deviation detection means 75 adds this voltage Vr ₁ ' and the detected voltage from the attitude sensor 16, that is, the voltage indicating the current attitude of the bucket bag 13, and after determining the deviation between the two voltages, the inverting section It is inverted and amplified at 76. These characteristics are shown in FIGS. 13A to 13D. Therefore, if the voltage of the attitude sensor 16 shows the voltage Vr ₁ , the deviation becomes 0, and there is no need to correct the attitude of the bucket 13, so the subsequent stage does not operate. Further, if the attitude sensor 16 is rotated toward the dump side than the bottom surface is horizontal, the voltage of the attitude sensor 16 is large, so the deviation voltage of the first deviation detection means 75 becomes the state shown in FIG. 13C, The voltage will be below the neutral point voltage. Then, based on this deviation voltage, the second determining means 49 judges that the rake direction needs to be corrected, and the second comparing means 57 compares the deviation voltage with the triangular wave signal, The analog switch 6 of the second driving means 65 generates a pulse signal with a pulse width.
9. The scoop solenoid 44 of the second solenoid valve 42 is energized via the switching element 67, and the bucket cylinder 14 is contracted to cause the bucket cylinder 14 to close.
Correct 3 in the scooping direction. As the bucket 13 approaches the horizontal bottom surface, the voltage of the attitude sensor 16 decreases, so the deviation voltage gradually decreases and the pulse width of the pulse signal becomes smaller, so the operating speed of the bucket cylinder 14 slows down. , the correction operation stops when the deviation is 0. That is,
The closer the bottom surface is to the horizontal, the slower the operating speed of the bucket 13 becomes, and the operation speeds up and stops smoothly.

On the other hand, if the bucket 13 is on the rake side, the deviation voltage will be in the state shown in FIG.

When lowering the boom 10 from the raised position, by operating the control lever 26 to the lowering side, the boom 10 will be lowered at an operating speed proportional to the amount of operation. The lowering speed of the boom 10 is automatically changed depending on the amount of deviation from the horizontal state of the bottom surface, and the bucket 13 is controlled so that the bottom surface is always horizontal when it touches the ground.

That is, a deviation signal between the detection signal detected by the attitude sensor 15 of the bucket 13 and the bottom horizontal voltage Vr ₁ which is the target attitude signal is obtained, and this is also related to the operating speed when the boom 16 is lowered. When the deviation signal is large, the descending speed of the beam 10 is made slower than the normal (during manual control) descending speed according to the command from the first potentiometer 27,
On the other hand, when the deviation signal is small, the descending speed is kept the same as normal.

The designated signal of the first potentiometer 27 is positive when rising and negative when falling, with the neutral potential being zero.
The deviation signal of the first deviation detection means 15 is negative when the bucket 13 deviates toward the dumping side from the attitude at the time when the bottom horizontally touches the ground, and is positive when the bucket 13 deviates toward the scooping side.

Therefore, when the bucket is shifted to the rake side, the bucket 13 is corrected to the dump side, and the AND gate 84 is opened by the dump signal from the comparator 50 and the falling signal from the comparator 47, and the analog switch 83 is turned on. In order to turn on, the deviation signal (positive) from the first deviation detection means 75 is sent to the second deviation detection means 8 via the analog switches 83 and 85.
6 and added to the command signal (negative). If the deviation is large, the second deviation detection means 86
The deviation between the output from the boom becomes smaller, and the operating speed when the boom is lowered becomes relatively slower than normal. As a result, the bottom surface of the bucket 13 approaches the horizontal position, and accordingly, the descending speed of the boom 10 returns to the normal speed.

When the bucket 13 is shifted toward the dumping side, the bucket 13 is corrected to the scooping side, the analog switch 81 is turned on via the AND gate 82, and the inverter 80 outputs the deviation signal from the first deviation detection means 75. A signal (positive) obtained by inverting (negative) is sent to the second deviation detection means 86 and added to the command signal (negative). Then, as described above, the bucket 13 is grounded with the bottom surface horizontal while adjusting the descending speed of the boom 10 depending on the magnitude of the deviation.

() Horizontal control of aperture surface At this time, select switch 72 to select horizontal aperture surface. In this case, the potentiometer of the setting means 70 has a bucket 13 as shown in FIG.
The aperture surface horizontal voltage Vr ₂ is set so that it is the same as the voltage of the attitude sensor 16 when the aperture surface is horizontal.

The operation is similar to the bottom horizontal control, and its operating characteristics are shown in FIGS. 14A to 14C.

() Posture maintenance control At this time, the selection switch 72 is set to the posture maintenance side, and the maintenance switch 32 is turned on. Then, a voltage indicating the current attitude of the bucket 13 is input to the sample/hold means 71 and held for a certain period of time, so this held voltage is inverted by the inverter 74 and the first deviation detecting means 75 detects the attitude sensor. The deviation from the voltage from 16 is determined and inverted. Then, the attitude of the bucket bag 13 is controlled by the deviation voltage in the same manner as the bottom horizontal control and opening surface horizontal control described above. Therefore, boom 1
Even if 0 moves up and down, the bucket 13 will maintain its initial position.

() Bottom surface grounding control Bottom surface grounding is a state in which the bottom surface of the bucket 13 is grounded or parallel to the plane that is the same as or parallel to the plane on which the front and rear wheels 2 and 3 of the tractor body 1 touch the ground, as shown in FIG. 15A. means. This is used when lowering the bucket 13 onto the ground or scooping it along the ground surface. In particular, when the bucket lorry 13 is grounded, it is difficult for the operator in the driver's seat 5 to see the attitude of the bucket loret 13 because it is obstructed by the bonnet, so this is very convenient in such a case.

The major difference between bottom ground control and other controls such as bottom horizontal control is that in other controls, control is based on the deviation of the rotation angle of bucket 13 with respect to the direction of the center of gravity; This is because a new factor, the inclination of the tractor body 1, is added to the posture.

Therefore, the tilt sensor 15 is used for control.
In this case, as shown in FIG. 15B, the signal voltages (resistances) of the tilt sensor 15 and the attitude sensor 15 are set to be the same when the bottom surface of the bucket 13 is grounded.

For control, the selection switch 72 and changeover switch 73 are placed on the side of the inclination sensor 15 on the bottom surface. Then, if the tractor body 1 has an inclination, the inclination sensor 15 detects the inclination and its voltage changes. At this time, if the bucket 13 is on the same ground surface, the attitude sensor 16 also has the same signal voltage as the tilt sensor 15. However, if the voltages of the attitude sensor 16 are different, the bucket cylinder 14 operates to correct the attitude of the bucket 13 so that it is on the bottom surface, by the same operation as the bottom horizontal control described above.

(Example) Hereinafter, the present invention will be described in detail with reference to the illustrated embodiment. In FIG. 2, 1 is a tractor body, 2 is a front wheel, 3 is a rear wheel, 4 is a rear wheel fender, and 6 is a driver's seat. Reference numeral 6 designates a front loader, which includes a mast 8 that is detachably installed on both sides of the tractor body 1 via a mounting base 7, and a boom 10 that is pivoted to the upper end of the mast 8 via a pivot shaft 9 so as to be movable up and down. This boom 10
It consists of a boom cylinder 11 for raising and lowering the boom, a bucket (working tool) 13 rotatably supported at the tip of the boom 10 by a pivot 12, and a bucket cylinder 14 for rotating the bucket.

A tilt sensor 15 detects the tilt of the trunk body 1, and is attached to the front loader 6 side, for example, the mast 8. Reference numeral 16 denotes an attitude sensor for detecting the attitude of the bucket cart 13, which is attached to a bracket 17 on the back side of the bucket cart 13. These sensors 15 and 16 are constructed by incorporating a weight plate 21 and a potentiometer 22 into two divided chambers 19 and 20 within a box-shaped case 18, as shown in FIG. The weight plate 21 is attached to a rotating shaft 23 supported by the case 18, and a potentiometer 22
is configured to be interlocked with the weight plate 21 via the rotation shaft 23, and therefore the tractor body 1,
The weight plate 21 responds to changes in the attitude of the bucket 13, and a voltage signal corresponding to the attitude is output from the potentiometer 22. Note that damper oil 23a is placed in the chamber 19.

Reference numeral 24 denotes an operating device, and as shown in FIGS. 4 to 7, there is an operating lever on a case 25 mounted on the rear wheel fender 4 on one side of the driver's seat 5, which can be operated longitudinally, horizontally, and diagonally. 26, this operating lever 26
first and second potentiometers 27,
28 etc. is incorporated. That is, the operating lever 26
is pivotally supported on the movable frame 29 via a horizontal axis 30, and the movable frame 29 is supported on the case 25 side via a longitudinal axis 31. Therefore, the operating lever 26 is pivoted on the horizontal axis 30 and the longitudinal axis which are perpendicular to each other. Using the two axes 31 as fulcrums, it can be operated in any direction as shown in FIG. Note that the operating lever 26 is elastically held at a neutral position by a spring (not shown).
The first potentiometer 27 constitutes a lifting command means for commanding the lifting and lowering of the boom 10, and
It outputs a command signal for raising and lowering the voltage in conjunction with the back and forth movement of the operating lever 26 via the horizontal shaft 30, and in accordance with the amount of operation of the operating lever 26. The second potentiometer 28 constitutes a rotation command means for commanding the rotation of the bucket 13, and is interlocked with the left and right movement of the operating lever 26 via the front and rear shaft 31 and the movable frame 29. It outputs a command signal for dumping and scooping voltage according to the operation amount of 26.

A push-button posture holding switch 32 is attached to the upper end of the operating lever 26. A hemispherical operating portion 33 is provided at the lower end of the operating lever 26,
Further, on the bottom side of the case 25, a rise switch 34, a fall switch 35, a dump switch 36, and a scoop switch 37 are provided front and back, left and right around the operating part 33. Each of these switches 34~
37 is adapted to be actuated by the actuating portion 33 when the operating lever 26 is operated by the maximum amount. Note that 38 is a flexible cover.

FIG. 8 shows a hydraulic circuit for the boom cylinder 11 and the bucket cylinder 14. Reference numeral 39 is a first electromagnetic valve for controlling the boom cylinder 11, and has an upward solenoid 40 and a downward solenoid 41. A second electromagnetic valve 42 controls the bucket cylinder 14, and has a dump solenoid 43 and a scoop solenoid 44. Both of these solenoid valves 39 and 42 are proportional type.

FIG. 1 shows an electric circuit for driving and controlling the solenoid valves 39, 42. In FIG. 1, the first discriminating means for discriminating the direction of movement during lifting and lowering includes two comparison sections 46 and 47, and a dead zone between the comparison sections 46 and 47.
The command signal from the first potentiometer 27 is the upper reference value (1/
2V+α), the comparison unit 46 outputs a rising signal, and when the voltage is smaller than the lower reference value (1/2V−α), the comparison unit 47 outputs a fall signal. 49 is a second discrimination means for discriminating the direction of movement during dumping/scooping, and the first discrimination means 4
5, two comparing parts 50 and 51, variable resistor 5
The comparator 50 outputs a dump signal and the comparator 51 outputs a scoop signal in response to a command signal from the second potentiometer 28.

Reference numeral 53 denotes triangular wave oscillation means, which oscillates a triangular wave signal a of a constant frequency as shown in FIG. 54 is a first comparison means, which includes two comparison units 55,
56, as shown in FIG. 9, the command signal b from the first potentiometer 27 and the triangular wave signal a from the triangular wave oscillation means 53 are compared, and the pulse width is determined according to the change in the command signal b. It is designed to generate a pulse signal c of . That is, comparison sections 55, 56
The inputs of the command signal b and the triangular wave signal a are reversed, and the comparator 55 turns on when the command signal b is larger than the triangular wave signal a, and turns off when it is smaller.
Although the pulse signal c is generated according to the relationship shown in FIG. 9, the comparator 56 turns on when the command signal b is smaller than the triangular wave signal a, and turns off when the command signal b is larger than the triangular wave signal a, which is the opposite of that shown in FIG. 57 is a second comparison means, which has two comparison parts 58 and 59, and which is connected to the second potentiometer 2.
Based on the command signal from 8 and the triangular wave signal from the triangular wave oscillating means 53, a pulse signal is generated in the same way as the first comparing means 54.

Reference numeral 60 denotes a first driving means for driving the first solenoid valve 39, which includes switching elements 61, 62 connected to the respective solenoids 40, 41, and comparison parts 55, 5.
Analog switch 6 that sends a pulse signal from 6
3, 64, and the comparing section 5 of the first determining means 54
The signals from 5 and 56 are sent to analog switches 63 and 6.
4, switching elements 61 and 62 are turned on and off in synchronization with the pulse signal. 65 is a second driving means for driving the second solenoid valve 42, and like the first driving means 60,
It is composed of switching elements 66, 67 and analog switches 68, 69.

70 is a setting means for setting the attitude of the bucket 13 to a required target attitude, and the setting means 70 sets the holding voltage from the sample/hold means 71, the bottom horizontal voltage Vr ₁ necessary to make the bottom of the bucket 13 horizontal, and the bucket 13. The aperture surface horizontal voltage Vr ₂ necessary to level the aperture surface of the tractor body 1 and the voltage indicating the inclination of the tractor body 1 from the inclination sensor 15 are selected and set by the posture selection switch 72. When the holding switch 32 of the operating lever 26 is turned on, the sample/holding means 71 detects the position of the attitude sensor 16 at that time.
It is designed to input a signal voltage from and hold it for a certain period of time (several seconds).

Reference numeral 74 denotes an inverting section which inverts the signal selected by the selection switch 72 with reference to the reference voltage (1/2V) of the N terminal. 75 is a first deviation detection means, which detects the signal from the attitude sensor 16 and the inversion unit 7;
4 and detect the deviation between the two,
It is inverted and amplified by an inverting section 76. 77, 78 are analog switches, 79 is
In the NOT gate, these constitute an automatic/manual selection means. When the holding switch 32 is off, the signal from the second potentiometer 28 is selected, and when it is on, the signal from the first deviation detection means 75 is selected and sent to the subsequent stage.

Reference numeral 80 denotes an inverting section which inverts the deviation signal from the first deviation detecting means 75 with reference to the reference voltage (1/2V) of the N terminal. Reference numeral 81 denotes an analog switch, which is turned on via an AND gate 82 when the fall signal from the comparator 47 and the scoop signal from the comparator 51 meet, and outputs the deviation signal inverted by the inverter 80 to the analog switch 85. It is now being sent to Reference numeral 83 denotes an analog switch, which is turned on via an AND gate 84 when the falling signal from the comparison section 47 and the dump signal from the comparison section 50 meet, and outputs the deviation signal from the first deviation detection means 75 to the analog switch 85 side. It is now being sent to
Analog switch 85 opens when hold switch 32 is turned on. 86 is a second deviation detection means which adds the command signal from the first potentiometer 27 and the deviation signal or the inverted deviation signal on the input side of the inverting section 80 to find the deviation between the two, and the deviation signal is sent to the inverting section. 8
7, the voltage is inverted based on the reference voltage (1/2V).

In the embodiment, the bucket 13 is used as an example of the working tool, but the tool is not limited to the bucket 13, and may be a fork or other attachment. In that case, if you want to be able to attach and detach the work tool at will and replace it, a mounting bracket is pivotally attached to the tip of the boom 10, and the work tool is detachably attached to this mounting bracket with a pin or the like. On the other hand, if the attitude sensor 16 is provided on the mounting bracket side, even if there are various working tools, there is no need to provide the attitude sensor 16 for each working tool, which is very convenient.

(Effects of the Invention) According to the present invention, the deviation between the target posture signal of the work implement and the detection signal is determined, and depending on the magnitude of the deviation signal, the lowering speed of the boom is slowed down when the deviation signal is large, and when the deviation signal is small, the lowering speed of the boom is slowed down. At times, the lowering speed of the boom is increased, so
The work implement can be controlled to a target posture when the boom is lowered, and the lowering of the boom is not stopped midway, so the operation is smooth.

[Brief explanation of the drawing]

The drawings illustrate one embodiment of the present invention, in which Fig. 1 is an electrical circuit diagram of the control system, Fig. 2 is a side view of the tractor, Fig. 3 is a sectional view of the sensor, and Fig. 4 is an operation diagram. Rear view of the device, Figure 5 is a sectional rear view of the same, Figure 6 is a view taken along the X-X arrow in Figure 5, Figure 7 is a view taken along the Y-Y arrow in Figure 5, and Figure 8 is a hydraulic circuit. Figure 9 is a signal waveform diagram, Figure 10 is an explanatory diagram of the control position, and Figure 11 is a diagram of the control position.
The figure shows the relationship between Bucket's posture and the sensor.
Figure 12 is an explanatory diagram of voltage settings, Figure 13 and
FIG. 4 is an explanatory diagram of the operation, and FIG. 15 is a diagram showing the relationship between the attitude of the tractor and the sensor. 1...Tractor body, 6...Front loader,
10...Boom, 13...Bucket (work tool),
16... attitude sensor, 24... operating device, 26...
...Operation lever, 27, 28... Potentiometer, 41, 42... Solenoid valve, 45, 49... Discrimination means, 53... Triangular wave oscillation means, 54, 57...
Comparison means, 60, 65... Drive means, 70... Setting means, 71... Sample/hold means, 7
5, 86...deviation detection means.

Claims (1)

[Claims] 1 Based on the command signal for raising and lowering the boom, the boom is raised and lowered at an operating speed proportional to the command signal, and
In a front loader work implement attitude control device that detects the attitude of the work implement at the end of the boom when the boom is lowered and controls the work implement so that it takes the target attitude, the connection between the target attitude signal of the work implement and the detection signal is determined. A boom lowering speed control device for controlling the posture of a work implement, characterized in that the boom is lowered at an operating speed proportional to a signal obtained by determining a deviation and subtracting the deviation signal from a command signal for lowering the boom.