JP2018013016A - Road surface cutting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more improve followability of a road surface cutting machine to change of a road surface to be cut.SOLUTION: A road surface cutting device comprises: a road surface cutting machine 3 which is provided to a vehicle and cuts a road surface as the vehicle travels; an actuator 4 which elevates and lowers the road surface cutting machine 3; cutting depth detection parts 19Aa, 19Ba which detect a road surface depth of cutting by the road surface cutting machine 3; and an elevation control part 19 which controls the actuator 4 so as to make smaller deviations between detection values of the cutting depth detection parts 19Aa, 19Ba and a set target depth H0 of cutting. The elevation control part 19 has an operation speed ratio setting part 19C which sets an operation speed ratio k of the actuator 4 larger when a traveling speed is slow than when the traveling speed is fast.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a road surface cutting device provided in a road surface cutting vehicle, and relates to a technique for cutting a road surface to a target cutting depth with a road surface cutting machine as the vehicle travels for the purpose of maintaining and repairing the road surface.

For example, asphalt pavements such as roads and bridge road surfaces are subject to deterioration such as rutting or cracking over time due to vehicle running or the like. For this reason, repair work of the road surface is performed regularly or at any time using a time zone with a small traffic volume such as at night.
Thus, in the repair of the road surface, the surface layer portion of the road surface is cut and removed by a road surface cutting device mounted on a dedicated road surface cutting vehicle called a road cutter. Then, if necessary, re-paving with a new asphalt mixture on the cutting road surface.

  Such a road surface cutting vehicle has a structure described in Patent Document 1, for example. In other words, this road surface cutting vehicle can be self-propelled by the front and rear wheels for traveling, and the road surface can be cut by a road surface cutting machine (cutter part) provided so as to be movable up and down with respect to the vehicle body. The road surface cutting vehicle is capable of scraping the asphalt pavement road surface with a road surface cutting machine while being self-propelled, and continuously transporting the scraped cutting waste material to the front of the vehicle body by a conveyor.

  The road surface cutting machine has a cutter portion in which a large number of cutter bits are provided on the peripheral surface of a cutter drum extending in the vehicle body width direction. The cutter unit is rotatably supported by the machine frame and is driven to rotate by a hydraulic motor. Further, the cutter unit is raised and lowered with respect to the road surface by a pair of right and left hydraulic cylinders connected to the machine frame, so that the cutter surface is provided with a cutter bit provided on the peripheral surface of the cutter drum, and the road surface is cut at an arbitrary cutting depth. Scrape off.

  The road surface cutting vehicle includes a road surface cutting automatic control unit as described in Patent Document 2. The road surface cutting automatic control unit detects the current cutting depth by the road surface cutting machine, and moves the left and right lifting hydraulic cylinders up and down so that the deviation between the detected cutting depth and the set target cutting depth is small. The cutting depth from the road surface is automatically controlled so as to be the target cutting depth.

Japanese Patent Laid-Open No. 11-50415 Japanese Patent Laid-Open No. 64-62505

Here, by automatically controlling the raising / lowering speed (operating speed) of the raising / lowering hydraulic cylinder so that the deviation between the detected cutting depth and the set target cutting depth increases, the cutting depth is set to the target cutting depth as much as possible. Thus, that is, the elevation of the road surface cutting machine is made to follow so that unevenness of a predetermined level or more does not occur on the cutting road surface.
At this time, when the road surface to be cut has unevenness more than necessary, it is common for the operator of the road surface cutting vehicle to perform cutting work (hanging work) at a vehicle speed slower than the vehicle speed at the time of normal cutting.

  However, in the above prior art, if the deviation amount is the same regardless of the vehicle speed, the lifting speed of the road surface cutting machine is the same lifting speed, so when performing optimization at the vehicle speed during normal cutting, In the cutting work in the road surface situation where the deviation from the target value is frequently changed with the traveling as described above, the responsiveness becomes slow, and the road surface cutting machine has not been able to follow up and down to cut. There is a risk of local irregularities (drum marks etc.) occurring on the cutting road surface.

On the other hand, if the response of the lifting speed to the vehicle speed is set to be fast, the lifting work is sensitive to the cutting work at the normal cutting speed, and conversely, there is a possibility that unevenness is locally generated on the cutting road surface. .
The present invention has been made paying attention to the above points, and aims to further improve the followability of a road surface cutting machine with respect to a change in the road surface to be cut.

In order to solve the problem, a road surface cutting device according to an aspect of the present invention includes a road surface cutting machine that is provided in a vehicle and cuts the road surface as the vehicle travels, an actuator that moves up and down the road surface cutting machine, and the above Elevation control for controlling the actuator so that a deviation between a detected value of the cutting depth detecting unit and a set target cutting depth becomes small, and a cutting depth detecting unit for detecting a road surface depth to be cut by a road surface cutting machine The elevator controller changes an operating speed ratio, which is a ratio of the operating speed of the actuator to the deviation, according to the traveling speed of the vehicle, and the traveling speed is relatively slow An operation speed ratio setting unit that sets the operation speed ratio larger than that when the traveling speed is high is provided.
Here, the operation speed ratio can be expressed by (operation speed / deviation). The operating speed of the actuator is synonymous with the lifting speed of the road surface cutting machine.

An operator of a road surface cutting vehicle usually performs a cutting operation (hanging operation) at a reduced vehicle speed when the road surface to be cut has more than necessary unevenness. In this scene, even when the vehicle speed is decreased, the deviation with respect to the target cutting depth is frequently changed as the vehicle travels.
On the other hand, according to the aspect of the present invention, when the traveling speed of the vehicle is low, the responsiveness of the raising / lowering of the road surface cutting machine with respect to the target cutting depth is higher than when the vehicle is fast, so that the road surface to be cut The followability of the road surface cutting machine to changes can be improved.

On the other hand, at the time of normal cutting, it is possible to ensure the followability of the road surface cutting machine with respect to changes in the road surface to be cut by suppressing the responsiveness of raising and lowering of the road surface cutting machine with respect to the target cutting depth.
As a result, even when the cutting speed changes with the change in the speed of the vehicle, the formation of local irregularities on the cut road surface is suppressed as compared with the conventional case, and a flatter cutting road surface can be finished.

  Here, the present invention is not effective only when the vehicle is traveling at a steady speed during road surface cutting, but when the vehicle starts to travel (at the start of cutting) or when the vehicle shifts to stop (cutting). This is also effective when quitting. For example, at the start of cutting, the vehicle speed is traveling at an extremely low speed, but the cutting depth fluctuates due to body vibration due to a large cutting resistance (cutting reaction force), and the deviation from the target cutting depth frequently Change. On the other hand, according to the aspect of the present invention, when the vehicle speed is low, the control responsiveness is relatively high, so that it is possible to finish the cutting road surface more flatly from the start of cutting. Become.

[BRIEF DESCRIPTION OF THE DRAWINGS] It is a side view explaining the road surface cutting vehicle based on Embodiment based on this invention. It is a conceptual diagram explaining the road surface cutting device which concerns on embodiment based on this invention, (a) is the conceptual diagram seen from the vehicle back, (b) is the conceptual diagram seen from the side. It is a figure explaining the structure of the cutting control controller. It is a figure explaining the relationship between the deviation amount according to an operation speed ratio, and a control signal. It is a figure explaining another example of the relationship between the deviation amount according to the operating speed ratio and the control signal. It is a figure explaining another example of the relationship between the deviation amount according to the operating speed ratio and the control signal.

Next, embodiments of the present invention will be described with reference to the drawings.
<Configuration>
As shown in FIG. 1, a road surface cutting vehicle 1 equipped with a road surface cutting device of the present embodiment includes a vehicle body 2, a traveling wheel 6, and a road surface cutting machine 3 supported so as to be movable up and down with respect to the vehicle body 2. The actuator 4 which raises / lowers the road surface cutting machine 3 and the conveyance conveyor 5 are provided. The road surface cutting vehicle 1 further includes cutting depth detection units 14 </ b> A and 14 </ b> B and a cutting control controller 17.

The conveyor 5 is a conveyor that conveys the cutting waste material scraped off by the road surface cutting machine 3 to the front of the vehicle body 2 and is supported by the vehicle body 2.
The traveling wheel 6 of the present embodiment includes a front wheel 6 </ b> A provided on the front side of the vehicle body 2 and a rear wheel 6 </ b> B provided on the rear side of the vehicle body 2. The front wheels 6A can be steered by operating a steering mechanism (not shown). The axle of the rear wheel 6B is connected to the engine via a transmission, and constitutes a driving wheel that is rotationally driven by the driving force from the engine. The traveling form of the road surface cutting vehicle 1 is not limited to this, and the front wheel 6A side may be a driving wheel or a vehicle that is self-propelled by a crawler or the like.

  The road surface cutting machine 3 is disposed below the vehicle body 2 between the front wheel 6A and the rear wheel 6B. As shown in FIG. 2, the road surface cutting machine 3 is configured by providing a large number of cutter bits 3 b on the peripheral surface of a cutter drum 3 a whose axis is oriented in the width direction of the vehicle body 2. The cutter drum 3a is rotatably supported by the machine casing 7 and can be driven to rotate by a hydraulic motor (not shown). The machine frame 7 is, for example, a box-shaped frame that is open at the bottom.

  The actuator 4 that moves up and down the road surface cutting machine 3 includes a pair of left and right lifting hydraulic cylinders 4A and 4B. Each of the lifting hydraulic cylinders 4A and 4B is attached to the vehicle body 2 with the cylinder body facing up and down, and the cylinder rod extends downward from the cylinder body. The tip of the cylinder rod is connected to the machine casing 7. Accordingly, the vertical position (position with respect to the road surface) of the machine frame 7, that is, the road surface cutting machine 3 with respect to the vehicle body 2 is adjusted according to the stroke amount of the lifting hydraulic cylinders 4 </ b> A, 4 </ b> B, and the cutting depth by the road surface cutting machine 3 is adjusted. Is adjusted.

Here, the front side of the machine casing 7 is connected to the vehicle body 2 via parallel links 8 extending in the longitudinal direction of the vehicle body 2. A pair of parallel links 8 are arranged on both sides in the vehicle width direction. By providing the parallel link 8, the machine frame 7 is held in a constant posture as it moves up and down.
Each lifting hydraulic cylinder 4A, 4B is connected to a hydraulic pressure supply device (not shown) via individual servo valves 10A, 10B. And the stroke of each raising / lowering hydraulic cylinder 4A, 4B can be independently controlled by changing the control signal (control current value i) given to each servo valve 10A, 10B.

  Further, plate-like side covers 11 </ b> A and 11 </ b> B are arranged along the left and right side walls of the machine casing 7, respectively. The side covers 11 </ b> A and 11 </ b> B are provided to be movable up and down with respect to the machine frame 7. The side covers 11A and 11B have one ends of wires 12A and 12B connected to the upper portions thereof. The wires 12A and 12B extend upward and are wound in a state where tension is applied to the wire winders 13A and 13B provided on the upper part of the machine casing 7. As a result, the side covers 11A and 11B are displaced downward by their own weight, and the lower ends of the side covers 11A and 11B can come into contact with the road surface during cutting.

Moreover, the lower end part of side cover 11A, 11B is provided with the warp-shaped slider which slides on a road surface. It is preferable that a rotating body that rolls as the vehicle moves is provided at the lower ends of the side covers 11A and 11B.
In addition, it has a stopper (not shown) for temporarily fixing the side covers 11A and 11B to the machine frame 7, and when the machine frame 7 is lifted upward by the stopper, for example, the lower ends of the side covers 11A and 11B Can be lifted off the road surface.

  The cutting depth detectors 14 </ b> A and 14 </ b> B are configured by level sensors, and detect the amount of elevation of the side covers 11 </ b> A and 11 </ b> B relative to the machine frame 7. Since the lower ends of the side covers 11A and 11B are in contact with the road surface, the cutting depth with respect to the road surface by the road surface cutting machine 3 can be detected from the vertical position of the machine frame 7 relative to the side covers 11A and 11B. The cutting depth detectors 14A and 14B detect the amount of elevation of the side covers 11A and 11B relative to the machine frame 7 by, for example, the amount of winding of the wires 12A and 12B according to the elevation of the side covers 11A and 11B.

The vehicle speed sensor 15 is provided in the above-described transmission, for example, and detects the traveling speed (vehicle speed) of the vehicle.
Here, at predetermined positions on the side of the driver's seat and the vehicle body 2, there are provided a traveling operator for instructing traveling of the vehicle, a set value for road surface cutting, and a control panel 16 for operating cutting. The vehicle operator operates the control panel 16 to set the target cutting depth H0 and to control the rotational drive of the cutter drum 3a. The cutting setting modes include a manual cutting mode and an automatic cutting mode. The present invention relates to the automatic cutting mode.

Here, in the case of the manual cutting mode, the operation control of the actuator, that is, the adjustment of the cutting depth and the like by the road surface cutting machine 3 is performed by the operator manually operating the switch and the like. For this reason, in the manual cutting mode, the cutting situation depends on the skill level of the operator.
The cutting control controller 17 operates when a cutting start control signal is input from the control panel 16. The cutting control controller 17 includes a road surface cutting machine drive control unit 18 and a lift control unit 19.

The road surface cutting machine drive control unit 18 outputs an operation signal to a hydraulic circuit of a hydraulic motor (not shown) and performs a process of driving the cutter drum 3a to rotate with a predetermined torque.
The elevating control unit 19 individually controls the left and right elevating hydraulic cylinders 4A and 4B via the servo valves 10A and 10B so that the road surface cutting depth by the road surface cutting machine 3 becomes the target cutting depth H0.

  The elevation control unit 19 includes cutting depth detection units 19Aa and 19Ba, deviation amount calculation units 19Ab and 19Bb, an operation speed ratio setting unit 19C, and elevation control signal output units 19Ac and 19Bc. Here, a series of processes of the cutting depth detectors 19Aa and 19Ba, the deviation amount calculators 19Ab and 19Bb, and the lifting control signal output units 19Ac and 19Bc are performed at a predetermined sampling period and are operated in synchronization with them. The processing of the speed ratio setting unit 19C is also executed. Here, the cutting depth detectors 19Aa and 19Ba, the deviation amount calculators 19Ab and 19Bb, and the lift control signal output units 19Ac and 19Bc are provided for the left lift hydraulic cylinder 4A and the right lift hydraulic cylinder 4B. Although two types of control units are provided, the processing contents are the same, and therefore, the processing of the control unit of the left lifting hydraulic cylinder 4A will be representatively described below.

The left cutting depth detector 19Aa detects the cutting depth of the road surface cutting machine 3 with respect to the road surface at the left position in the vehicle width direction based on the detection signal from the left cutting depth detector 14A.
The left deviation amount calculation unit 19Ab calculates a deviation amount ΔH by subtracting the target cutting depth H0 input from the control panel 16 from the cutting depth detected by the left cutting depth detection unit 19Aa.

  The operating speed ratio setting unit 19C sets the operating speed ratio, which is the response speed of the left and right lifting hydraulic cylinders 4A and 4B, according to the vehicle speed value input from the vehicle speed sensor 15. In the present embodiment, the first operating speed ratio and the second operating speed ratio are set as the operating speed ratio. At this time, the second operating speed ratio is set to a larger value than the first operating speed ratio. The operating speed ratio setting unit 19C selects the second operating speed ratio when it is determined that the vehicle speed is equal to or lower than the preset low speed value Vs, and when it is determined that the vehicle speed is greater than the set low speed value Vs. The first operating speed ratio is selected.

  The set low speed value Vs is an extremely low speed value of 2 m / min, for example. This set low speed value Vs is a speed that is slower than the speed range during steady running that is generally employed in normal cutting operations. The set low speed value Vs is preferably set to a different value between when the vehicle is in an acceleration state and when the vehicle is in a deceleration state. In this case, the set low speed value Vs when the vehicle is determined to be in a decelerating state is smaller than the set low speed value Vs when the vehicle is determined to be in an accelerated state. For example, the set low speed value Vs during acceleration is 2 m / min, and the set low speed value Vs during deceleration is 1 m / min.

Here, each operation speed ratio is stored and selected in the storage unit in the form of a map or a coefficient of a conversion formula using the deviation amount ΔH and the elevation control signal i as variables. The raising / lowering control signal i can be expressed by a current value, for example, as shown in FIG. In the case of a map, the slope of the line with the deviation amount ΔH and the lift control signal i as variables becomes the operation speed ratio. Moreover, if it is a conversion type | formula, for example, it represents with a type | formula like the following (1) type | formula, and the coefficient k will be an operating speed ratio. The conversion formula does not need to be a linear expression, and other conversion formulas may be applied as long as the deviation control signal i increases as the deviation amount ΔH increases. For example, the line corresponding to the second operating speed ratio may be set to have a quadratic curve shape as shown in FIGS.
k = ΔH / i (1) equation

In the following description, the operation speed ratio is described by a case where the operation speed ratio is represented by a coefficient k in the conversion formula. That is, the first operating speed ratio k1 and the second operating speed ratio k2 are stored in the storage unit. Note that k1 <k2.
Here, the values of the first operating speed ratio k1 and the second operating speed ratio k2 stored in the storage unit may be fixed values or may be configured to be set by an operator. good. For example, when the operator selects and inputs the deviation amount ΔH and the raising / lowering control signal i for the first operating speed ratio k1, k converted by the above equation (1) is used as the first operating speed ratio k1. Store as k1. Similarly, for the second operating speed ratio k2, the operator selects and inputs the deviation amount ΔH and the lift control signal i, whereby k converted by the above equation (1) is set to the second value. Stored as the operating speed ratio k2.

Then, the operating speed ratio setting unit 19C selects k1 or k2 according to the vehicle speed as described above, and sets the selected coefficient value k1 or k2 as the operating speed ratio k. For example, if it is determined that the vehicle speed is equal to or lower than the set low speed value Vs, k2 is selected and k2 is set to k.
An example of the relationship between k1 and k2 is a relationship as shown in FIG. 4, and the second operating speed ratio k2 at the time of low speed cutting is, for example, the first operating speed ratio at the vehicle speed at the time of normal cutting. It is set in the range of 1.5 to 3 times k1.

The lifting control signal output unit 19Ac for the left side uses the coefficient k set by the operating speed ratio setting unit 19C, and uses the coefficient k set for the raising / lowering corresponding to the deviation amount ΔH calculated by the deviation amount calculating unit 19Ab based on the equation (2). A control signal i, that is, a control current value i is calculated.
i = k · ΔH (2) The calculated lift control signal i is output as a control command to the left servo valve 10A that calculates the deviation amount ΔH.

<Operation other>
When it is determined that the automatic cutting is started, the cutting controller 17 causes the left and right lifting hydraulic pressures via the servo valves 10A and 10B so that the left and right cutting depths by the road surface cutting machine 3 become the target cutting depth H0. The stroke amount of the cylinders 4A and 4B is controlled. As a result, the road surface is sequentially cut as the road surface cutting vehicle 1 travels.

(Normal cutting)
As an operator, in order to efficiently perform the cutting work on the road surface, when it is thought that the road surface to be cut has a predetermined flatness, the cutting is performed at a steady vehicle speed such as 10 m / min.
At this time, in this embodiment, the road surface cutting machine 3 is moved up and down so as to achieve the target cutting depth H0 at the first operating speed ratio k1 in which the response is relatively suppressed.

Here, on the road surface where the deviation does not change greatly, when the operation speed ratio k at the time of cutting is too large, the response of the lifting and lowering operation of the road surface cutting machine 3 becomes more sensitive as the vehicle speed increases. There is a possibility that local unevenness (drum mark or the like) may occur on the cutting road surface. For this reason, what is necessary is just to obtain | require the 1st operating speed ratio k1 which does not produce a local unevenness | corrugation from an experiment or a theoretical value, and to set the 1st operating speed ratio k1 to a memory | storage part.
As a result, during normal cutting, it is suppressed that the responsiveness of raising and lowering of the road surface cutting machine 3 with respect to the target cutting depth H0 is suppressed. Followability can be ensured.

(When cutting at extremely low speed)
On the other hand, when the road surface to be cut has a predetermined unevenness or more, the operator performs the cutting operation (hanging operation) by reducing the speed of the vehicle. In this scene, even if the vehicle speed is decreased, the vehicle body 2 also rises and falls due to the wheels 6 climbing on the convex portion or being located in the concave portion. Therefore, the deviation amount ΔH with respect to the target cutting depth H0 as the vehicle travels. May change frequently and greatly.
On the other hand, according to the present embodiment, when the traveling speed of the vehicle is slow, the elevation control is performed at the second operation speed ratio k2, so that the road surface cutting machine 3 is moved up and down with respect to the target cutting depth H0. Responsiveness increases. As a result, the followability of the road surface cutting machine 3 with respect to a change in the road surface to be cut can be improved.

(At the start and end of cutting)
In addition, this embodiment is not effective only when the vehicle is traveling at a steady speed during road surface cutting, but when the vehicle starts to travel (at the start of cutting) or when the vehicle shifts to stop (cutting). This is also effective when quitting.
For example, at the start of cutting, the vehicle speed is traveling at an extremely low speed, but the detected cutting depth varies due to vehicle body vibration generated by a large cutting resistance (cutting reaction force) and the target cutting depth H0. Deviations to are sensitively changed. On the other hand, since the vehicle speed is slow, the second operating speed ratio k2 is adopted, so that the responsiveness of the lifting control becomes relatively high, so that the cutting road surface is finished more flatly from the start of cutting. Is possible.

As described above, in the road surface cutting device according to the present embodiment, even when the cutting speed changes with the change in the speed of the vehicle, the formation of local unevenness on the cut road surface is suppressed as compared with the conventional case. It becomes possible to finish a flatter cutting surface.
Here, the set low speed value Vs is set to a value different between the acceleration state and the deceleration state, and the vehicle is determined to be in a deceleration state rather than the set low speed value Vs when the vehicle is determined to be in an acceleration state. It is preferable that the setting low speed value Vs is set to be small. As a result, a dead zone is set for the control switching, and it is possible to prevent the switching of the set operating speed ratio from hunting while traveling at a vehicle speed near the set low speed value Vs.

<Modification>
Here, in the above description, the case where the elevation control is performed by selecting one of the two kinds of operation speed ratios k1 and k2 with the set low speed value Vs as a boundary is described, but the present invention is not limited to this. Three or more operating speed ratios may be provided according to the vehicle speed zone.
Moreover, although the case where the operation speed ratio k with respect to the vehicle speed range is set in multiple stages (two stages in the above embodiment) is illustrated. The operating speed ratio k may be set to change steplessly according to the vehicle speed. Even in this case, the operation speed ratio is set to increase as the vehicle speed decreases.

When the vehicle speed is Vs, for example, a constant value = Vs · k (where Vs> 0) is set.
Furthermore, the operation speed ratio k may be changed according to the target cutting depth H0 or the detected cutting depth. In this case, the operating speed ratio k set by the operating speed ratio setting unit 19C is corrected so that the cutting depth is greater when the cutting depth is deeper than when the cutting depth is shallow. For example, α (> 0) is subtracted from k when it is shallower than a predetermined cutting depth, and β (> 0) is added to k when it is equal to or larger than the predetermined cutting depth.
In this way, by taking into account the cutting depth, the formation of local irregularities on the cut road surface is further suppressed, and it becomes possible to finish a flatter cut road surface.

DESCRIPTION OF SYMBOLS 1 Road surface cutting vehicle 2 Car body 3 Road surface cutting machine 3a Cutter drum 3b Cutter bit 4 Actuator 4A, 4B Lifting hydraulic cylinder 6 Wheel 10A, 10B Servo valve 11A, 11B Side cover 14A, 14B Cutting depth detection part 15 Vehicle speed sensor 16 Control Panel 17 Cutting control controller 18 Road surface cutting machine drive control unit 19 Elevation control unit 19Aa, 19Ba Cutting depth detection unit 19Ab, 19Bb Deviation amount calculation unit 19Ac, 19Bc Elevation control signal output unit 19C Actuation speed ratio setting unit i Elevation control Signal k Operating speed ratio k1 First operating speed ratio k2 Second operating speed ratio Vs Set low speed value ΔH Deviation

Claims (3)

A road surface cutting machine provided on the vehicle for cutting the road surface as the vehicle travels;
An actuator for moving up and down the road surface cutting machine;
A cutting depth detection unit for detecting a road surface depth cut by the road surface cutting machine;
A lifting control unit that controls the actuator so that a deviation between a detection value of the cutting depth detection unit and a set target cutting depth is small, and
The elevating control unit changes an operation speed ratio, which is a ratio of the operation speed of the actuator to the deviation, according to the travel speed of the vehicle. When the travel speed is relatively slow, the travel speed is fast. A road surface cutting device comprising an operating speed ratio setting unit that sets the operating speed ratio larger than the case.   The operating speed ratio setting unit has a first operating speed ratio and a second operating speed ratio larger than the first operating speed ratio as the operating speed ratio, and the vehicle traveling speed is set in advance. 2. The road surface cutting device according to claim 1, wherein the second operating speed ratio is selected when it is equal to or less than a set low speed value.   The set low speed value is a value different between the acceleration state and the deceleration state of the vehicle, and the set low speed value when the vehicle is determined to be in a deceleration state rather than the set low speed value when the vehicle is determined as an acceleration state. The road cutting device according to claim 2, wherein the set low speed value is small.

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