JP2002295181A - Propulsive mechanism of ground drilling machine and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid a collision with an underground obstacle by accurately surveying a distance to the obstacle with radar for underground exploration during propulsion of a ground drilling machine. SOLUTION: The ground drilling machine having the propulsive mechanism is propelled via a speed reducer 14 by a motor 13 for propulsion while rods 3 are sequentially added to a leading body 5, so as to drill a hole in the ground. In the propulsive mechanism, the speed reducer 14 is taken as a two-stage type having two speed reduction ratios, i.e., high and low speed reduction ratios. Accordingly, when switching to a stage of the high speed reduction ratio takes place, the high speed reduction ratio permits avoidance of an unstable area where revolutions are not stabilized in a state of a low oil flow rate of the motor 13, and prevents occurrence of an unstable state of action with intermittent halts in order to enable stabilization of low-speed propulsion. When the distance to the underground obstacle is surveyed with the radar 8 for the underground exploration, the distance to the obstacle can be accurately surveyed to enable avoidance of the collision with the obstacle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground drilling machine for drilling holes for burying gas pipes, power cables, signal cables, optical fiber cables, water supply pipes, sewage pipes, etc. in the ground without cutting. The present invention relates to a propulsion mechanism and a control method thereof.

[0002]

2. Description of the Related Art Conventionally, as a ground drilling machine, a body is provided with a propulsion mechanism, and a rod propelled into the ground by the propulsion mechanism and a leading conductor attached to the tip of the rod and having an inclined pressure receiving surface. In addition, the rod is propelled from the starting conductor, for example, from a starting shaft, to a target point, for example, a reaching shaft, by propelling the rod while sequentially adding a rod to the leading conductor. The earth pressure reaction force acting on the inclined pressure receiving surface of the leading conductor by propelling while rotating the leading conductor with the rod while rotating the leading conductor substantially linearly, and by propelling the leading conductor without rotating with the rod. Thus, the leading conductor is propelled in the direction opposite to the inclined pressure receiving surface (in the direction of the combined force of the propulsion force and the earth pressure reaction force) to change the propulsion direction.

On the other hand, in this ground drilling machine, an underground exploration radar is attached to a tip conductor attached to the tip of a rod to find an underground obstacle to be propelled, and to identify this obstacle. Was exploring the distance. When exploring the distance to an underground obstacle using this installed underground radar, if the propulsion speed of the leading conductor and the rod is not extremely low due to the performance of the radar, The distance could not be probed accurately.

In such a ground drilling machine, the propulsion mechanism is provided with a propulsion motor for propelling the leading conductor and the rod, and this propulsion motor is a swash plate type variable hydraulic motor. . A reduction gear is attached to this propulsion motor so that power is output via the reduction gear.

[0005] Conventionally, in a machine for drilling a hole in the ground, a device in which a speed reducer is attached to a propulsion motor to output power through the speed reducer is disclosed in Japanese Unexamined Patent Publication No. 5-3212.
As disclosed in Japanese Patent Publication No. 87, there has been known a speed reducer in a one-stage type having only a predetermined value, which is always decelerated at the same speed reduction ratio.

On the other hand, Japanese Patent Application No. 200
At 0-364315, in the ground drilling machine, the propulsion was performed by the propulsion motor in the propulsion mechanism. At this time, the propulsion speed of the leading conductor and the rod was controlled by controlling the propulsion motor. .

[0007]

SUMMARY OF THE INVENTION In a conventional ground drilling machine, when the distance to an underground obstacle is searched by using an underground radar, it is necessary to accurately detect the distance to the obstacle. , It was necessary to make the propulsion speed of the leading conductor and the rod extremely low.
In the device described in Japanese Patent No. 1287, since the speed reduction gear attached to the propulsion motor always reduces the speed at the same reduction ratio, when the propulsion speed is reduced, the swash plate type hydraulic variable motor is used. An unstable state such as stopping and moving may occur in the motor for propulsion, and the propulsion at low speed may not be stable and may become unstable. This hinders the distance search, and in the worst case, there is a problem that the leading conductor collides with an obstacle and is damaged. this is,
In the case of propulsion motors, due to the nature of the swash plate, when the flow rate of oil is low, there is a dead zone or unstable area where the rotation speed stops or rises or falls due to oil leakage, and the rotation is not stable. There is an unstable state such as stopping or moving in the propulsion motor, which makes propulsion at low speed unstable.

In view of this, by setting the reduction gear at a high reduction ratio so as not to hinder the search for the distance to the underground obstacle by the underground search radar in the speed reducer, the oil of the propulsion motor can be reduced at low speed propulsion. It is conceivable to avoid the unstable region by avoiding the unstable region in the state where the flow rate is low, but in this case, the propulsion speed decreases at the high speed propulsion, and the underground There is a problem that the propulsion speed in normal propulsion when the distance to an obstacle is not searched by the search radar becomes very slow, and the work efficiency is greatly reduced. For this reason, it was difficult to increase the reduction ratio of the reduction gear.

On the other hand, a conventional Japanese Patent Application No. 2000-364315.
In the thing described in the above, the propulsion motor was controlled to control the propulsion speed of the leading conductor,
Even if the propulsion motor is controlled constantly, the propulsion speed of the leading conductor may not be constant and may change due to changes in the load due to soil changes in the ground, etc. Also, there is a problem in that when the distance to the obstacle under the ground is searched using the underground radar, the search for the distance to the obstacle cannot be performed accurately.

[0010]

The first invention is a propulsion mechanism for a ground drilling machine which drills a hole in the ground by propelling through a speed reducer with a propulsion motor while sequentially adding a rod to a leading conductor. , Is a propulsion mechanism for a ground drilling machine in which the reduction gear is a multi-stage type having a plurality of different reduction ratios.

According to the first aspect of the invention, the speed reducer is a multi-stage type having a plurality of different speed reduction ratios, so that the speed reducer can be switched between a high speed reduction ratio and a low speed reduction ratio. When the propulsion speed is set to a low speed when switching to a high reduction ratio, the high reduction ratio avoids an unstable region where rotation of the propulsion motor in a state where the oil flow rate is small is not stable, and stops or moves. Prevents unstable conditions such as flapping and stabilizes propulsion at low speeds.For example, when using an underground exploration radar to detect the distance to an underground obstacle, Can be accurately detected, and collision with an obstacle can be reliably avoided. On the other hand, when switching to a low reduction ratio, the propulsion speed can be increased, and the working efficiency can be greatly improved. In this way, when searching for the distance to an underground obstacle using the underground radar and when performing normal propulsion, the reduction gear with a reduction ratio suitable for the content of each work By making the selection, it is possible to always optimally perform the search for the distance to the obstacle and the normal propulsion by the underground radar.

A second invention provides a method for controlling a propulsion mechanism of a ground drilling machine which drills a hole in the ground by propelling through a reduction gear with a propulsion motor while sequentially adding a rod to a leading conductor. A propulsion speed detecting means for detecting a propulsion speed, a propulsion target speed setting means for setting a propulsion target speed, and a propulsion speed detected by the propulsion speed detection means. Speed constant control means for calculating a speed deviation between the propulsion target speed set by the propulsion target speed setting means and outputting a command for eliminating the calculated speed deviation to the propulsion motor to control the propulsion speed to be constant. When the speed reducer is switched to a high reduction ratio, the speed constant control means controls the propulsion speed to be constant. It is your way.

According to the second aspect of the present invention, when the reduction gear is switched to a high reduction ratio, the constant speed control means controls the propulsion speed to be constant, thereby stabilizing the propulsion speed at low speed. For example, a collision with an obstacle can be prevented by performing a very good search for a distance from the obstacle using an underground search radar, for example.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a propulsion mechanism for a ground drill according to the present invention and a control method thereof will be described. The ground drilling machine is basically the same as the conventional one. Figure 1
As shown in FIG. 1, a fuselage 1 is provided with a propulsion mechanism 2, and a rod 3 propelled into the ground by the propulsion mechanism 2;
A leading conductor 5 having an inclined pressure-receiving surface 4 attached to the tip of the rod.
To a target point, for example, a reaching shaft 7.
Then, the tip conductor 5 is propelled while being rotated together with the rod 3 so as to be propelled linearly. Further, the tip conductor 5 is propelled without being rotated together with the rod 3 so as to act on the inclined pressure receiving surface 4 of the tip conductor 5. Due to the earth pressure reaction force, the leading conductor 5 is propelled in a direction opposite to the inclined pressure receiving surface 4 (the direction of the combined force of the propulsion force and the earth pressure reaction force) to change the propulsion direction.

In this ground drilling machine, a ground conductor radar 8 is mounted on the tip conductor 5 attached to the tip of the rod 3 at the center of the inclined pressure receiving surface 4 so that an obstacle in the ground to be propelled can be removed. Find and explore the distance to this obstacle. The underground radar 8 radiates electromagnetic waves into the ground and receives reflected waves from obstacles in the ground, thereby detecting the distance to the obstacles. In the underground radar 8 for exploring the distance to an obstacle, the probing speed of the leading conductor 5 and the rod 3 needs to be extremely low because the exploration distance is as short as 500 mm in terms of radar performance. .

As the propulsion mechanism 2 of the ground drilling machine, a cradle 12 that moves along a frame 11 obliquely to the front and rear of the body 1 is provided, and a propulsion motor 13 is provided at a rear portion of the frame 11. Motor 1
3, the cradle 12 is moved along the frame 11, and the propulsion motor 13 is a swash plate type variable hydraulic motor.
4 to output power. In addition, a rotation motor 15 is provided on the cradle 12 that moves along the frame 11, and the rotation motor 15 is also a swash plate type variable hydraulic motor. Output power. A rod mounting portion 17 is provided in front of the rotation motor 15, and the rod 3 is mounted on the rod mounting portion 17, thereby rotating the leading conductor 5 and the rod 3 by the rotation motor 15,
The tip conductor 5 and the rod 3 are propelled underground by the propulsion motor 13. In addition, in this propulsion motor 13,
A propulsion distance detector 18 such as a potentiometer or an encoder is attached to detect the propulsion distance, and the rotation motor 15 is also provided with a rotation angle detector 19 such as a potentiometer or an encoder to detect the rotation angle.

In the propulsion mechanism 2 having such a configuration, the speed reducer 14 attached to the propulsion motor 13 has a plurality of stages having a plurality of different reduction ratios. A two-stage system having two reduction ratios is used to switch to a desired reduction ratio. Although the reduction gear 14 is a two-stage type having two different reduction ratios, it may be a multi-stage type having three or more different reduction ratios.

In the speed reducer 14, when the speed reduction ratio is changed to a low speed reduction ratio, the low speed reduction ratio allows the propulsion speed to be set to a high speed specification, for example, a speed reduction ratio of 40.
7. The propulsion speed is increased to about 200 mm / sec to increase the speed range. Also, when the propulsion speed is switched to a high reduction ratio, the propulsion speed is set to a low speed specification by a high reduction ratio. The speed range is made as small as about 5 to 50 mm / sec by setting the speed to about 50 mm / sec. As described above, in this embodiment, for example,
The reduction ratio between the high-speed specification and the low-speed specification is as large as about 1: 8, and a compact reduction gear is used.

Next, the reduction gear 14 and the propulsion motor 1
3, the shaft 21 and the plurality of cylinders 22 are arranged in parallel in the propulsion motor 13, and the tip of the piston 23 of each cylinder 22 is fixed. The swash plate 24 is slidably contacted. Thus, the plurality of cylinders 22 are sequentially reciprocated to rotate the shaft 21 and generate power.

In the speed reducer 14, the shaft 21 of the propulsion motor 13 passes through the center. The multi-plate type first clutch portion 25 is directly attached to the shaft 21, and the planetary speed reducer 26 is attached to the shaft 21. The multi-plate type second clutch unit 27 is attached via the. This planetary reduction unit 26
Is a sun gear 28, a ring gear 29 and a planet gear 30
The sun gear 28 is fixed to the shaft 21 side, and the planet gear 30 is fixed to the second clutch part 27 side. Then, the first clutch section 25 and the second clutch section 27
, A spur gear reduction unit 32 is attached to the rotation body 31, and the spur gear reduction unit 32 includes a central small gear 33 and a large gear 34 fixed to the rotation body 31. The eccentric reduction unit 35 is connected to the spur gear reduction unit 32.
The eccentric reduction unit 35 is attached to the spur gear reduction unit 32.
An eccentric reduction unit 35 has an output unit 38 attached to the ring gear 37 of the eccentric reduction unit 35. Although not shown, the first clutch portion 25 and the second clutch portion 27 are provided by the reduction ratio switching portion.
And the second clutch portion 27.

With such a configuration, the first clutch 2
5, the rotation of the shaft 21 of the propulsion motor 13, that is, the power is transmitted to the first clutch unit 25, the rotating body 31, the spur gear reduction unit 32, and the eccentric reduction unit 35, as shown in FIG. After that, it is output from the output unit 38. At this time,
Reduced gear ratio and high-speed specification.

When the second clutch portion 27 is connected, as shown in FIG. 3B, the rotation of the shaft 21 of the propulsion motor 13, that is, the power is reduced by the planetary reduction portion 26, the second clutch portion 27, and the rotation. The signal is output from the output unit 38 through the body 31, the spur gear reduction unit 32, and the eccentric reduction unit 35. At this time, as compared with the case where the first clutch unit 25 is engaged, the reduction ratio is increased by passing through the planetary reduction unit 26, and the low-speed specification is achieved.

Next, the speed reducer 14 in the propulsion mechanism 2
The hydraulic circuit of the propulsion motor 13 will be briefly described. As shown in FIG. 4, a pump 42 driven by an engine 41 is provided.
The flow control valve 43 is connected to a flow switching valve 44, and the flow switching valve 44 is connected to the propulsion motor 13 and the speed reducer 14.
Connect. This flow control valve 43 inputs an electric signal,
A flow rate based on the electric signal is supplied. The flow switching valve 44 receives an electric signal, and switches the forward / reverse rotation of the propulsion motor 13 according to the electric signal.

The hydraulic circuit is not limited to the one described above, but may be another circuit. For example, as shown in FIG. 5, a main pump 45 and a sub-pump 46 driven by the engine 41 are provided, and a flow control valve 47 is connected to the main pump 45, and a propulsion motor is connected to the flow control valve 47. 13 and the speed reducer 14, and pilot valves 48, 48 'are connected to the sub-pump 46. The pilot valves 48, 48' are connected to the flow control valve 47 as a pilot circuit. As a result, the flow control valve 47 supplies a flow based on the electric signal, and also switches the forward / reverse rotation of the propulsion motor 13.

Next, an outline of a control device of the propulsion motor 13 and the rotation motor 15 in the propulsion mechanism 2 will be described. As shown in FIG. 6, a propulsion distance detector 18 attached to the propulsion motor 13 and a rotation angle detector 19 attached to the rotation motor 15 are provided. A reduction ratio switching input unit 51 for switching the ratio;
Further, a propulsion speed input unit 52 for inputting a propulsion speed and a rotation speed input unit 53 for inputting a rotation speed are provided. The controller 54 includes a timer 55 therein, and includes a propulsion control unit 56 and a rotation control unit 57. The propulsion control unit 56 includes a propulsion distance detector 18 and a reduction ratio switching input unit. 51
The flow control valve 4 in the hydraulic circuit of the propulsion motor 13 based on the data input from the
3. A command is output to the pilot valves 48, 48 'and the flow rate switching valve 44, and a command is also output to the reduction ratio switching unit 58 of the speed reducer 14 to control the propulsion motor 13 and the speed reducer 14. The rotation control unit 57 also issues a command to the flow control valve 59 and the flow switching valve 60 in the hydraulic circuit of the rotation motor 15 based on data input from the rotation angle detector 19 and the rotation speed input unit 53. Output to control the rotation motor 15. A display unit 61 for displaying various data input to the propulsion control unit 56 and the rotation control unit 59
Is provided.

In this controller 54,
Although not shown, distance data to the obstacle is input from the underground survey radar 8 attached to the conductor 5 and output to the display unit 61 so as to display the distance to the obstacle and the like. May be.

As described above, in the two-stage type speed reducer 14 having two reduction ratios, that is, one having a low reduction ratio and one having a high reduction ratio, the two-stage reduction gear 14 has a low reduction ratio and a high reduction ratio. The propulsion speed at the time of switching will be described with reference to FIG. In FIG. 7, the horizontal axis represents the propulsion motor 1.
3 is a chart showing the relationship between the oil flow rate and the propulsion speed, with the oil flow rate and the vertical axis representing the propulsion speed.

When the speed reducer 14 is switched to a low reduction ratio for high-speed specification, the propulsion speed can be set to a maximum speed of about 200 mm / sec by the low reduction ratio, as indicated by a line L in the drawing. When switching to a high reduction ratio and using the low-speed specification, as shown by the line H in the figure, the propulsion speed can be set to about 50 mm / sec at the highest speed by the high reduction ratio. In the low-speed specification with a high reduction ratio, the inclination angle becomes smaller than in the high-speed specification with a low reduction ratio, so that the oil flow rate near the start of the propulsion speed rise of the propulsion motor 13 is small. A propulsion speed of about 5 to 50 mm / sec can be obtained in a stable area where the flow rate of oil is stable to a certain extent while avoiding an unstable area or dead zone where rotation is not stable. Propulsion at a low speed in the stable region of the motor 13 stabilizes the propulsion speed.

As described above, the speed reducer 14 attached to the propulsion motor 13 in the propulsion mechanism 2 has a two-stage type having two reduction ratios, one having a low reduction ratio and the other having a high reduction ratio. When switching to a high reduction ratio, the high reduction ratio avoids an unstable region or dead zone where the rotation of the propulsion motor 13 is low when the flow rate is low, and causes an unstable state such as stopping or moving. And propulsion at low speed can be stabilized. For example, when the distance to the obstacle under the ground is searched using the underground radar 8, the search for the distance to the obstacle can be accurately performed. Can do and avoid collisions with obstacles. On the other hand, when switching to a low speed reduction ratio, the low speed reduction ratio prevents a reduction in the propulsion speed in propulsion at a high speed, and also enables a high speed of the propulsion speed, which makes it possible to perform normal propulsion. Work efficiency is greatly improved.

Thus, the worker performs a preliminary survey of the ground, and if it is determined that there is no obstacle in the ground, the operator sets a high-speed specification with a low reduction ratio in the speed reducer 14 and performs propulsion at a high speed. To In addition, the worker conducted a preliminary survey of the ground and found that there was an obstacle in the ground,
Alternatively, if it is not possible to carry out a preliminary survey of the ground, a low-speed specification with a high reduction ratio in the speed reducer 14 is used so that the underground radar 8 does not hinder the search for the distance to an underground obstacle. Therefore, while accurately detecting the distance to the obstacle, collision with the obstacle is avoided and propulsion at a low speed is performed.

As described above, by selecting a reduction gear having a reduction ratio suitable for the contents of various operations in the speed reducer 14, it is always possible to optimally search for a distance to an obstacle and normal propulsion by the underground radar 8. It can be carried out.

On the other hand, in the above-described embodiment, in the speed reducer 14 having a two-stage structure having two speed reduction ratios of a low speed reduction ratio and a high speed reduction ratio, When switching to the low-speed specification, the controller 54 of the control device performs the following control method.

As shown in FIG. 8, the propulsion control section 56 of the controller 54 includes a propulsion speed detecting means 71, a propulsion target speed setting means 72, and a constant speed control means 73. The propulsion speed detecting means 71 and the propulsion position data input from the propulsion distance detector 18 and the timer 5
The propulsion speed V is detected from the time data of No. 5. The target propulsion speed setting means 72 sets the target propulsion speed Vref from the propulsion speed data input by the propulsion speed input unit 52.
In the constant speed control means 73, the propulsion speed detection means 7
A propulsion speed V between the propulsion speed V detected in Step 1 and the propulsion target speed Vref set by the propulsion target speed setting means 72 is calculated, and a command to eliminate the calculated speed deviation u is output to the propulsion motor 13 so that the propulsion is performed. Control for keeping the speed V constant is performed.

As a control for keeping the propulsion speed V constant by the constant speed control means 73, as shown in FIG. 9, the propulsion speed V is subtracted from the propulsion target speed Vref to calculate a speed deviation u, and the calculated speed deviation u is calculated. The command value i is obtained by multiplying the speed deviation u by the proportional / integral control, that is, by the transfer function K {1 + 1 / (T × s)}. In the transfer function, K is a gain constant, T is a time constant, and s is a Laplace transform operator. The command value i is a current value output to the flow control valve 43 and the pilot valves 48, 48 'of the hydraulic circuit of the propulsion motor 13. Then, the obtained command value i is output as a command for eliminating the speed deviation u. By feeding back the propulsion speed V in this way, the propulsion speed V can be quickly set to the target propulsion speed Vref, and thereafter, can be stabilized at the target propulsion speed Vref.
Can be kept constant.

As described above, when the reduction gear 13 is switched to a high reduction ratio, by controlling the propulsion speed to be constant by the constant speed control means 73, the load changes due to a change in the soil quality in the ground. Even when affected by the leading conductor 5, the propulsion speed can be kept constant at all times, and the propulsion at a low speed can be stabilized. For example, the underground exploration radar 8 can search the distance to an obstacle very well. This reliably prevents collision with an obstacle.

[Brief description of the drawings]

FIG. 1 is an overall explanatory view of a ground drill.

FIG. 2 is an explanatory diagram of a reduction gear and a propulsion motor according to the present invention.

FIG. 3 (A) is an explanatory view of an operation state of a reduction gear and a propulsion motor according to the present invention. (B) It is an explanatory view of an operation state of a reduction gear and a propulsion motor by the present invention.

FIG. 4 is an explanatory diagram of a hydraulic circuit of a reduction gear and a propulsion motor according to the present invention.

FIG. 5 is an explanatory diagram of another hydraulic circuit of the reduction gear and the propulsion motor according to the present invention.

FIG. 6 is an explanatory diagram of a control device for a propulsion motor and a rotation motor according to the present invention.

FIG. 7 is a table showing a relationship between an oil flow rate and a propulsion speed in a propulsion motor.

FIG. 8 is an explanatory diagram of a controller in the control device according to the present invention.

FIG. 9 is a control block diagram of the constant speed control means according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... body, 2 ... propulsion mechanism, 3 ... rod, 4 ... inclined pressure receiving surface, 5 ... tip conductor, 6 ... starting shaft, 7 ... reaching shaft, 8 ... underground radar, 11 ... frame, 12 ... cradle,
13: Propulsion motor, 14: Reduction gear, 15: Rotation motor, 16: Reduction gear, 17: Rod mounting part, 18: Propulsion distance detector, 19: Rotation angle detector, 21: Shaft,
22 ... cylinder, 23 ... piston, 24 ... swash plate, 25 ...
First clutch unit, 26: planetary reduction unit, 27: second clutch unit, 28: sun gear, 29: ring gear, 30: planet gear, 31: rotating body, 32: spur gear reduction unit, 33
... Small gear, 34 ... Large gear, 35 ... Eccentric reduction unit, 36 ... Gear, 37 ... Ring gear, 38 ... Output unit, 41 ... Engine, 42 ... Pump, 43 ... Flow control valve, 44 ... Flow switching valve, 45 ... Pump, 46 ... pump, 47 ... flow control valve,
48: pilot valve, 48 ': pilot valve, 51: reduction ratio switching input unit, 52: propulsion speed input unit, 53: rotation speed input unit, 54: controller, 55: timer,
56: Propulsion control unit, 57: Rotation control unit, 58: Reduction ratio switching unit, 59: Flow control valve, 60: Flow switching valve, 61: Display unit, 71: Propulsion speed detection unit, 72: Propulsion target speed setting unit 73, constant speed control means.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toyohiko Yasu 3-20-1 Nakase, Kawasaki-ku, Kawasaki-shi, Kanagawa F-term in the 3rd development center of Construction Machinery Development Headquarters, Komatsu Ltd. 2D054 AC18 BA03 GA04 GA15 GA82 GA92 5J070 AC02 AE11 AF03 AK22

Claims (2)

[Claims] 1. A propulsion mechanism for a ground drilling machine that drills a hole in the ground by propelling through a speed reducer (14) with a propulsion motor (13) while sequentially adding a rod (3) to a tip conductor (5). A propulsion mechanism for a ground drilling machine, wherein the speed reducer (14) is a multi-stage type having a plurality of different reduction ratios. 2. A propulsion mechanism for a ground drilling machine which drills a hole in the ground by propelling a propulsion motor (13) via a speed reducer (14) while sequentially adding a rod (3) to a tip conductor (5). In the control method, the speed reducer (14) has a multi-stage structure having a plurality of different reduction ratios, a propulsion speed detecting means (71) for detecting a propulsion speed, and a propulsion target for setting a propulsion target speed. Speed setting means (72)
And calculating a speed deviation between the propulsion speed detected by the propulsion speed detection means (71) and the propulsion target speed set by the propulsion target speed setting means (72), and issuing a command to eliminate the calculated speed deviation to the propulsion motor ( 13) and a constant speed control means (73) for controlling the propulsion speed to be constant. When the speed reducer (14) switches to a high reduction ratio,
A method for controlling a propulsion mechanism of a ground drilling machine, characterized in that a constant speed control means (73) controls the propulsion speed to be constant.