JPH0435576B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic control device for a motor grader.

Generally, a motor grader as shown in FIGS. 1 and 2 is used as a working machine for leveling roads, large-scale farms, etc. Here, FIG. 1 is a plan view of the motor grader, and FIG. 2 is a side view thereof. The illustrated motor graders are all articulate type motor graders, and each has at least a blade 1, a car body 2, a drawbar 3, a circle 4, a frame 5, and a front axle 6 as its basic components, and these components are interconnected. The posture is left to a hydraulic or mechanical drive system. First, the frame 5 has its front end pivotally supported by the front axle 6 and its rear end supported by the vehicle body 2, and is articulated at the connection point 7 with the vehicle body 2 (with the connection point 7 as the pivot point, the frame 5 is the same as the vehicle body). The frame 5 is configured to pivot on a plane. Note that this articulation is performed by a hydraulic motor (not shown).

Next, a drawbar 3 is connected to the front end of the frame 5 by a universal joint 8, and the left and right rear ends of the drawbar 3 are suspended from the frame 5 by a pair of hydraulic cylinders (not shown). ing. Therefore, by operating this pair of hydraulic cylinders simultaneously, the drawbar 3 moves up and down using the universal joint 8 as a fulcrum, and by making the lengths of the left and right hydraulic cylinders different, the drawbar 3 moves along its longitudinal axis and the universal joint. It pivots using 8 as the axis.

Furthermore, a hydraulic cylinder (not shown) is provided between the frame 5 and the drawbar 3 to apply force from the frame 5 to the drawbar 3 in the lateral direction (with respect to the longitudinal direction of the frame), and this hydraulic cylinder is actuated. By doing so, the drawbar 3 is shifted left and right using the universal joint 8 as a fulcrum. Next, drawbar 3
A circle 4 is attached to the lower surface of the drawbar 3 so as to be rotatable on the same plane as the lower surface of the drawbar 3, and the circle 4 is rotated by operating a hydraulic motor (not shown). Further, a blade 1 is fixed to the lower surface of this circle 4, and this blade 1 rotates together with the circle 4. Therefore, the locus of the cutting edge of the blade 1, that is, the finishing plane is the frame 5.
Various operations such as the articulation rate of the drawbar 3, the lift of the drawbar 3, the left/right tilt of the drawbar 3, the shift of the drawbar 3, and the rotation of the circle 4 are involved in the determination.

FIG. 3 schematically shows the relationship between each part, the traveling plane, and the finishing plane in the above-mentioned motor grader when the drawbar shift operation is not performed and the vehicle body inclination angle is arbitrary. First, plane ABCD shows the running surface, and the direction of movement of the motor grader is DA→
It is. Further, the line segment DE corresponds to the drawbar 3, and the line segment EF corresponds to the frame 5. In the initial state (in which the drawbar 3 is not tilted left or right or the circle 4 is not rotated), the line segment CD corresponds to the cutting edge of the blade 1, and the plane CDEG is the plane on which the circle rotates.

Now, if the drawbar 3 is tilted left and right in the direction of travel by operating the hydraulic cylinder that suspends the drawbar 3 from the above state, the cutting edge of the blade 1 will move to the line segment C ₁ D, and the circle plane will change to the plane C. ₁ DEG ₁
Move to. At this time, ∠C ₁ DC becomes the drawbar left/right inclination angle. When the hydraulic motor is driven in this state, the cutting edge of the blade 1 rotates on the circle plane C ₁ DEG ₁ with the point D as the center and moves to the line segment C ₂ D. At this time, ∠C ₂ DC ₁ becomes the circle rotation angle. When the motor grader is run in this state, the midpoint of the cutting edge of blade 1 moves on the line segment DA, and the right end of the cutting edge of blade 1 passes through point _C2 and moves parallel to the line segment DA, so the finishing plane is a point. It becomes a plane that includes A, C, and C ₂ .

By the way, the ground to be graded by a motor grader is usually very sloped, uneven, etc., so if it is difficult to make one run considering the power of the motor grader, the rotation angle of the blade 1 should be reduced. It was necessary to change the propulsion angle of the blade 1 with respect to the direction of movement of the vehicle body in accordance with various conditions, such as running the blade in several times or decreasing the rotation angle when the propulsion speed decreases. For this reason, the circle rotation operation during operation of the motor grader is an operation that is performed particularly frequently during the ground leveling work. In the conventional motor grader, the above-described circle rotation operation is controlled by operating a lever-type circle rotation angle setting device provided in the driver's seat of the vehicle body 2.
That is, by operating the lever of the circle rotation angle setting device back and forth, a circle rotation command is given to a drive system such as a hydraulic motor, and the position of the blade 1, which rotates as one with the circle, is adjusted each time by adjusting the position of the blade 1 through the driver's seat window. The degree of rotation of the circle was controlled by checking it visually. For this reason, circle rotation control in conventional motor graders has had the following problems.

a) The lever operation is a back and forth operation, whereas the circle operation is a rotational operation, so the setting of the circle rotation angle and the rotational operation did not intuitively match, making control difficult.

b. Since the circle rotation angle was set visually each time, the operator's operations were complicated and errors were likely to occur in the rotation angle.

The present invention has been made in view of the above circumstances, and it is possible to easily set the rotation angle with the same feeling as the rotation operation of the circle, and to rotate the circle reliably following the set value. It is an object of the present invention to provide an automatic control device for a motor grader that enables the above-mentioned control even during shifting and articulation.

Therefore, in the present invention, the setting device for setting the rotation angle of the circle described above is constructed of a so-called dial-type setting device in which a rotating knob is provided with a needle that simulates the blade 1, and the setting device is integrated with the knob by rotating the knob. The angle pointed by the rotating needle is the same as the rotation angle of the circle and blade. In addition to this circle rotation angle setting device, a drawbar left/right inclination angle setting device, a circle rotation angle sensor, a drawbar left/right inclination angle sensor, a shift angle sensor, and an articulation angle sensor are provided at various locations to perform the following controls.

A. The circle rotation angle is made to follow the set angle based on the deviation between the set angle from the circle rotation angle setting device and the detection angle of the circle rotation angle sensor.

B. Correct the detection angle of the drawbar left/right tilt angle sensor with the set angle from the circle rotation angle setting device, and adjust the drawbar left/right tilt angle to the set angle based on the deviation between the corrected angle and the set angle from the drawbar left/right tilt angle setter. make it follow.

C When performing the control in A above at the time of shifting and articulation, the circle rotation angle is corrected to the propulsion angle of the blade with respect to the vehicle body traveling direction based on the detection angle of the shift angle sensor and the articulation angle sensor, and the correction angle and the setting described above are performed. The circle rotation angle is made to follow the set angle by the deviation of the angle.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 4 is a block diagram showing one embodiment of the present invention, in which controls A and B of the above-mentioned controls can be performed. That is, the circle rotation angle is made to follow the set angle α' by the deviation σ between the set angle α' from the circle rotation angle setter T ₁ and the detected angle α of the circle rotation angle sensor S ₁ . Furthermore, the detection angle β of the drawbar left/right tilt angle sensor S ₂ is corrected using the setting angle α′ from the circle rotation angle setting device T ₁ and the correction angle β ₁ and the setting value β′ from the drawbar left and right tilt angle setting device T ₂ are corrected. The drawbar left/right inclination angle is made to follow β' by the deviation σ〓. Therefore, the arithmetic unit 100 is an arithmetic means for correcting the drawbar left-right inclination angle β with the above-mentioned setting angle α' and calculates the drawbar inclination angle β ₁ at the circle rotation angle α', and the arithmetic circuit 101 is composed of a microcomputer.
and a memory 10 in which a processing program mainly containing calculation formulas and a data table of trigonometric functions are stored.
Consists of 2. Next circle rotation angle sensor S ₁
is composed of, for example, a shaft encoder, and detects the rotation angle of the circle 4 with respect to the drawbar 3 by measuring the rotation speed of the pinion gear 10 that transmits the rotation of the hydraulic motor 9 to the circle 4, as shown in FIG. Next, the drawbar left/right tilt angle sensor S ₂ is connected to its main body S ₂₁ as shown in FIGS. 5 and 6.
is fixed at an arbitrary point on the drawbar 3 in a direction perpendicular to the longitudinal axis of the drawbar 3, and the brush
S ₂₂ 's operation is dependent on gravity. Therefore, the drawbar left/right inclination angle sensor _S2 detects the inclination angle of the drawbar 3 in the direction perpendicular to the longitudinal axis of the drawbar. The circle rotation angle setting device T ₁ is a rotatable dial type device, and as shown in Fig. 7, the circle rotation angle setting device T 1 has a circular main body 11 whose inner periphery is carved with angle scales in predetermined units. knob 12
and a needle 13 imitating the blade 1. Therefore, by appropriately rotating this knob 12, the angle indicated by the needle 13 can be commanded to the drive system as the set angle α'. At this time, the blade 1 would ideally be rotated at the same time as the needle 13. The above-mentioned circle rotation angle setting device T ₁ and the drawbar left/right inclination angle setting device T ₂ are arranged at a position in the driver's seat of the vehicle body 2 that is easy for the operator to operate. Now, in Fig. 3, when the motor grader is in the initial state, that is, when the blade 1 is at the position of line segment CD,
0° is detected by the circle rotation angle sensor S ₁ and the drawbar left/right tilt angle sensor S ₂ , respectively. Next, when the target inclination angle β' is commanded from the drawbar left/right inclination angle setting device T ₂ , the drawbar 3, circle 4, and blade 1 are driven together, and the cutting edge of this Toki blade 1 is a line segment.
Move to DC ₁ . At the same time, the target setting angle β' is applied to the comparison circuit 60. At this time, ∠C ₁ DC is detected by the drawbar left/right tilt angle sensor S ₂ as the drawbar left/right tilt angle β.
It is added to the arithmetic circuit 101 in 00. At this time, no circle rotation angle is commanded from the circle rotation angle setter T ₁ and there is no correction condition, so the drawbar left/right inclination angle β is directly applied from the arithmetic circuit 101 to the comparison circuit 60 . Here, the comparison circuit 60 calculates the deviation σ between the drawbar inclination angle β and the drawbar left-right inclination angle β' added in advance from the drawbar left-right inclination angle setter _T2 . Then, by driving the hydraulic cylinder 62 via the drive circuit 61 using this deviation σ, the drawbar 3 is tilted to the target inclination angle β'. Therefore, the blade 1, which is tilted together with the drawbar 3, is also tilted by the control described above, following the target tilt angle β'. Next, from this state, the target rotation angle α' is commanded by the circle rotation angle setting device _T1 . At this time, turn knob 12 and hand 13.
Align it to the position where it points to α° on the angle scale. Then, circle 4 and blade 1 will be integrated into a flat surface.
Rotating on C ₁ DEG ₁ , the cutting edge of the blade 1 is a line segment
C ₂ Move to position D. At the same time, the target rotation angle α' is applied to the comparison circuit 50. At this time, the circle rotation angle sensor S ₁ detects ∠C ₂ DC ₁ as the circle rotation angle α, and the detected value α is also added to the comparison circuit 50. The comparator circuit 50 calculates the deviation σ between the detected value α and the target rotation angle α' set in advance by the circle rotation angle setting device _T1 . Then, by driving the hydraulic motor 52 via the drive circuit 51 using the deviation σ, the circle 4 is rotated to the target rotation angle α'. Therefore, the blade 1, which rotates integrally with the circle 4, follows and rotates up to the rotation angle α'. At this time, the rotational states of the needle 13 of the circle rotation angle setting device _T1 and the blade 1 are almost the same. Here, since the cutting edge of the blade 1 rotates from the line segment C ₁ D to the position of the line segment C ₂ D on the plane C ₁ DEG ₁ which is not parallel to the running plane ABCD, the inclination angle of the blade 1, that is, the inclination of the drawbar 3 An error occurs in the corner, and this error needs to be corrected. Therefore, the target rotation angle α' commanded by the circle rotation angle setting device T ₁ mentioned above is also applied to the arithmetic circuit 101 at the same time as the command. Here, calculation circuit 1
01 searches the trigonometric function data table in the memory 102, corrects the detected value β of the drawbar left/right tilt angle sensor S ₂ added in advance by the set angle α', and obtains the correction value β at the circle rotation angle α'. ₁ is calculated and the correction value β ₁ is added to the comparison circuit 60. The comparator circuit 60 calculates the deviation σ between the correction value β ₁ and the target inclination angle β' added in advance from the drawbar left/right inclination angle setter T ₂ . 62 to tilt the drawbar 3 to the tilt angle β'.

FIG _. 8 is a block diagram showing another _embodiment of the present invention, which differs from the embodiment shown in FIG. do. In this embodiment, in addition to the controls A and B of the above-mentioned controls, control C can also be performed.

In other words, during shift and articulation operations of the motor grader, the shift angle sensor
S ₃ detection angle γ and articulation angle sensor
The circle rotation angle α is corrected to the propulsion angle α ₁ of the blade 1 with respect to the vehicle body traveling direction using the detection angle δ of S ₄ , and the circle rotation angle is adjusted to the target rotation angle α based on the deviation between the correction angle α ₁ and the target rotation angle α′. ′ can be made to follow. Therefore, the arithmetic circuit 103 is a correction arithmetic means for this purpose, and the memory 102 contains a processing program centered on arithmetic expressions consisting of a circle rotation angle α, a shift angle γ, and an articulation angle δ, and a data table of trigonometric functions. Stored. First, the drawbar shift angle sensor _S3 is composed of a potentiometer, and as shown in FIG. 9, its main body _S31 is fixed to the back of the frame 5, and its brush
_S32 is connected to the back surface of the drawbar 3 via a buffer _S33 . Therefore, the drawbar shift angle sensor _S3 connects the frame 5 and the drawbar 3 with the universal joint 8 as the apex.
The horizontal component of the angle formed by these is detected. Here, the buffer 33 absorbs the lift operation (vertical movement) of the drawbar 3.

The articulation angle sensor _S4 is also composed of a potentiometer, and its main body _S41 is fixed to the vehicle body 2, and the brush _S42 is fixed to the frame 5, as shown in FIG. In this way, the articulation angle sensor _S4 is attached to the connection point between the vehicle body 2 and the frame 5, and the frame 5 is connected to the vehicle body 2.
This is to detect the articulation angle of.
Also, in Figure 11, the cutting edge of blade 1 is on the line in Figure 3.
The drawbar 3 is shifted by the shift angle γ from the state at position C ₂ D, and the relationship among the frame 5, drawbar 3, and blade ₁ at this time is simply shown. The line segment EF corresponds to the drawbar 3, and the line segment _C2D corresponds to the blade 1.

Therefore, in this state, ∠C ₂ DC ₁ is detected as the circle rotation angle α by the circle rotation angle sensor S ₁ , and ∠F ₁ EF is detected as the drawbar shift angle γ by the drawbar shift angle sensor S ₃ . (However, the line segment EF and the line segment C ₁ D, and the line segment A ₁ D and the line segment C ₃ D are perpendicular to each other.) Here, since the propulsion direction of the motor grader is parallel to the frame 5, that is, the line segment EF ₁ , the drawbar By shifting 3 by γ, the propulsion direction of blade 1 (line segment C ₂ D) moves from the direction of line segment DA to the direction of line DA ₁ .

Therefore, ∠C ₂ DC ₃ becomes the propulsion angle α ₁ of the blade 1 with respect to the vehicle body traveling direction. The detection values α and γ of the circle rotation angle sensor S ₁ and the drawbar shift angle sensor S ₃ described above are applied to the arithmetic circuit 103. The arithmetic circuit 103 searches the data table in the memory 102 based on the circle rotation angle α and the drawbar shift angle γ, and calculates the blade propulsion angle α ₁ with respect to the vehicle body traveling direction according to the processing program. Next, this calculated propulsion angle α ₁ is calculated by the calculation circuit 10
3 is added to the comparison circuit 50, and the comparison circuit 50 sets this propulsion angle α ₁ and the circle rotation angle setting device T ₁ in advance.
The deviation σ〓 from the target rotation angle α′ added from is calculated.

By driving the hydraulic motor 52 via the drive circuit 51 using this deviation σ, the circle 4 is
Rotate. At this time, the cutting edge of the blade 1, which rotates in unison with the circle 4, is rotated to a position rotated by α' from a line segment C ₃ D perpendicular to the direction of travel of the vehicle body.

Therefore, the rotation of the needle 13 of the circle rotation angle setting device _T1 and the rotation of the blade 1 are maintained in the same rotational state as viewed from the operator. Therefore, drawbar 3
The rotation angle α' can be set during shifting with the same feeling as when not shifting.

Next, FIG. 12 shows the frame 5 being articulated with respect to the car body 2 from the state where the cutting edge of the blade 1 is at the position of line segment C ₂ D in FIG. 3, and the posture of each part at this time is simply shown. This is what is shown.

Here, the line segment FK is the longitudinal direction of the vehicle body 2, the line segment FL is the extension line of the line segment EF, that is, the extension line of the frame 5,
Point F is the connection point between car body 2 and frame 5, line segment C ₂ D
indicate the blade 1, respectively.

Therefore, in this state, ∠C ₂ DC ₁ is sent to the circle rotation angle sensor S ₁ as the circle rotation angle α, ∠
KFL is detected as articulation angle δ by articulation angle sensor _S4 . (However, line segment EF and line segment C ₁ D, and line segment A ₂ D and line segment C ₄ D, respectively, are perpendicular to each other.) Also, since the motor grader's propulsion direction is parallel to the longitudinal direction of the vehicle body, that is, line segment FK, By articulating the frame 5 by δ from the car body 2, the blade 1, that is, the line segment
The propulsion direction of C ₂ D also moves from the line segment DA direction to the line segment DA ₂ direction. Therefore, ∠C ₂ DC ₄ becomes the propulsion angle α ₁ of the blade 1 in the vehicle body traveling direction. In this state, the detected angles α and δ of the circle rotation angle sensor S ₁ and the articulation angle sensor S ₄ are calculated by the calculation circuit 103.
added to. The arithmetic circuit 103 searches the data table in the memory 102 based on these circle rotation angle α and articulation angle δ, calculates the propulsion angle α ₁ of the blade 1 in the vehicle body traveling direction according to the processing program, and calculates the calculated value α ₁ Comparison circuit 10
Add to. Then, as described above, the circle 4 is rotated via the drive circuit 51 and the hydraulic motor 52 based on the deviation between the calculated value α ₁ and the target rotation angle α' added in advance from the circle rotation angle setting device T ₁ . .
At this time, since the blade 1 also rotates together with the circle 4, its cutting edge is rotated to a position rotated by α' from a line segment C ₄ D perpendicular to the direction of movement of the vehicle body. Therefore, the rotation of the needle 13 of the circle rotation angle setting device _T1 and the rotation of the blade 1 are maintained in the same rotational state as viewed from the operator. Therefore, when articulating the frame 5, the rotation angle α' can be set in the same manner as when not articulating. In the above explanation, the shift operation of the drawbar 3 and the articulation operation of the frame 5 are performed independently, and the circle rotation angle α is corrected by each of the shift angle and the articulation angle to obtain the drawbar propulsion angle α ₁ . As mentioned above, if the calculation formula and trigonometric function program for when the shift operation and articulation operation are performed at the same time are stored in the memory 102, then when the shift operation and articulation operation are performed at the same time, It is also possible to obtain a propulsion angle α ₁ . In addition, an arithmetic circuit 101 in the arithmetic unit 110 converts the detected value β of the drawbar left/right tilt angle sensor S ₂ into a circle rotation angle setting device.
_This is _an arithmetic circuit for correcting with the set value α _' of the arithmetic circuit 101, and the fourth
In the same manner as shown in the illustrated embodiment, the drawbar inclination angle β can be controlled to follow the target inclination angle β' during circle rotation control when shifting the drawbar and articulating the frame.

As explained above, according to the automatic control device for a motor grader of the present invention, since a dial-type circle rotation angle setting device is used, it is possible to know the circle rotation angle just by feeling the hand holding the setting device, and it is possible to know the circle rotation angle by just feeling the hand holding the setting device. By rotating the setting device, the angle of the blade can be set with the same feeling as rotating the blade. In addition, since the rotation of the circle is made to follow the set value based on the deviation between the set value of the circle rotation angle setting device and the detected value of the circle rotation angle sensor, it has the excellent effect of further improving the rotation precision of the blade. .

[Brief explanation of drawings]

Figure 1 is a plan view of the articulation type motor grader, Figure 2 is a side view of the articulation type motor grader, and Figures 3, 11, and 12 schematically show the positions of each part of the motor grader. Figures 4 and 8 are block diagrams showing one embodiment of the present invention, Figures 5, 6, 9, and 10 are diagrams showing the mounting positions of the sensors, respectively. The figure is a front view of the circle rotation angle setting device according to the present invention. 1... Blade, 2... Vehicle body, 3... Drawbar, 4... Circle, 5... Frame, 6... Front axle, 50, 60... Comparison circuit, 51, 61...
Drive circuit, 52...Hydraulic motor, 62...Hydraulic cylinder, 100...Arithmetic unit, 101, 103...
Arithmetic circuit, 102...Memory, _S1 ...Circle rotation angle sensor, _S2 ...Drawbar left/right tilt angle sensor,
_S3 ...Drawbar shift angle sensor, _S4 ...Article angle sensor, _T1 ...Circle rotation angle setting device, _T2 ...Drawbar left/right tilt angle setting device.

Claims (1)

[Scope of Claims] 1. A drawbar whose one longitudinal end is connected to a frame by a universal joint, and a drawbar along a plane parallel to the longitudinal axis of the drawbar centered on a point on the longitudinal axis of the drawbar. A driven system includes at least a rotating circle and a blade fixed to the circle in parallel to a plane in which the circle rotates, and lifts the drawbar using the universal joint as a fulcrum and rotates the longitudinal axis of the drawbar. A motor grader comprising at least a first means for pivoting the drawbar as a pivot and a second means for rotating the circle as a drive system, comprising: a sensor for detecting a rotation angle of the circle; and a longitudinal direction of the drawbar. It has a sensor that detects the horizontal inclination angle of the drawbar in a direction perpendicular to the direction, and a needle that simulates the rotation of the blade on the circle seen from the vertical direction, and has a needle that simulates the rotation of the blade on the circle seen from the vertical direction. a circle rotation angle setter having a dial type structure that provides a setting angle such that the needle can always rotate in the same manner as the hand when viewed from any operating position; and a drawbar left-right inclination angle that sets the left-right inclination angle of the drawbar. a setting device; a control means for controlling the rotation angle of the circle based on a deviation between a detection angle applied from a sensor that detects the rotation angle of the circle and a target circle rotation angle set by the circle rotation angle setting device; a calculator that calculates the horizontal inclination angle of the drawbar from a detection angle added from a sensor that detects the horizontal inclination angle of the drawbar and a target circle rotation angle preset by the circle rotation angle setting device; an automatic control device for a motor grader, comprising: a control means for controlling the left-right tilt angle of the drawbar according to a deviation between the drawbar left-right tilt angle and a target drawbar left-right tilt angle preset by the drawbar left-right tilt angle setting device. 2. A vehicle body or frame that can be articulated, a drawbar whose longitudinal end is connected to the frame by a universal joint, and parallel to the longitudinal axis of the drawbar centered on a point on the longitudinal axis of the drawbar. A driven system includes at least a circle that rotates along a plane along which the circle rotates, and a blade that is fixed to the circle parallel to the plane in which the circle rotates, and the drive system includes at least a circle that rotates along a plane in which the circle rotates, and a blade that is fixed to the circle in parallel with the plane that the circle rotates. a first means for articulating the drawbar; a second means for lifting the drawbar using the universal joint as a fulcrum; and pivoting the drawbar about a longitudinal axis of the drawbar; A motor grader comprising, as a drive system, at least third means for shifting the drawbar left and right in its longitudinal direction, and fourth means for rotating the circle. a sensor that detects the articulation angle between the vehicle body and the frame; a sensor that detects the shift angle of the drawbar; a sensor that detects the rotation angle of the circle; and a sensor that detects the horizontal inclination angle of the drawbar. and a needle that imitates the rotation of the blade on the circle viewed from the vertical direction, and with respect to the rotation of the needle, the blade always remains in the same manner as the needle when viewed from any operating position. A circle rotation angle setter having a dial type structure that provides a setting angle that allows the drawbar to rotate; a drawbar left and right tilt angle setter that sets the left and right tilt angle of the drawbar; a sensor that detects the circle rotation angle; a first computing unit that calculates the propulsion angle of the blade with respect to the vehicle body traveling direction from the detected angles of the sensor that detects the angle and the sensor that detects the shift angle; and a target circle rotation that is preset by the circle rotation angle setting device. a second computing unit that calculates the horizontal inclination angle of the drawbar based on a detection angle added from a sensor that detects the angle and the horizontal inclination angle of the drawbar; and a blade propulsion angle calculated by the first computing unit and the a control means for controlling a propulsion angle of the blade in the vehicle body traveling direction based on a deviation from a target circle rotation angle preset by a circle rotation angle setting device; An automatic control device for a motor grader, comprising: a control means for controlling a left-right tilt angle of the drawbar based on a deviation from a target drawbar left-right tilt angle set in advance from a drawbar left-right tilt angle setting device.