JPS644889Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an automatic work speed control device for a road cutter.

[Conventional technology]

In a road cutter, the cutting load on the cutter drum increases or decreases depending on the working speed, i.e. the running speed of the road cutter during work, the hardness of the road surface, etc. Therefore, the cutting load on the cutter drum is maintained at the full capacity of the road cutter to proceed with the work efficiently. In order to do this, the work speed must be controlled in response to changes in the cutting load on the cutter drum due to changes in the road surface.

[The problem that the idea attempts to solve]

However, conventional road cutters were not equipped with a device that automatically controlled the working speed in response to fluctuations in the cutting load on the cutter drum, so workers monitored the driving pressure of the cutter drum with a pressure gauge and adjusted the work speed according to the magnitude of the pressure. It is necessary to perform the work while adjusting the cutter drum to reduce or increase it, but in reality, if the work speed is set to a level that does not cause the cutter drum to stop when the cutting load becomes large, then the cutting load will be small and cutting will be easy. Even if you reach a place where you can do it,
It is customary for work to proceed at the previous slow speed without adjusting the work speed. Therefore, it is difficult to say that conventional road cutters are always working at their maximum potential.

The present invention was developed in view of the above-mentioned circumstances, and its purpose is to provide an automatic control device that detects the cutting load on the cutter drum and obtains an optimal working speed according to the load.

[Means for solving problems and their effects]

In order to solve the above problems, the present invention includes a hydraulic motor, a hydraulic pump that can variably adjust the drive speed of the hydraulic motor according to the inclination angle of the swash plate, and a hydraulic system that controls the inclination angle of the swash plate. The load pressure applied to the hydraulic motor is introduced as pilot pressure, and when the pilot pressure exceeds a predetermined pressure, the hydraulic line to the electromagnetic servo directional switching valve is closed. In a road cutter equipped with a working traveling circuit having a pressure-sensitive directional control valve that shuts off and a cutter drum circuit having a similar configuration, the pilot pressure line of the pressure-sensitive directional control valve is connected to the working traveling circuit and the cutter drum circuit. The circuit is in communication with the circuit, and the setting value of the cracking pressure of the pressure-sensitive directional control valve in the work traveling circuit is set to a value smaller than the setting value of the cracking pressure of the pressure-sensitive directional control valve in the cutter drum circuit. Features.

By adopting the above configuration, when the cutting load increases while the road cutter is running while working, the cutter drum driving pressure, which is the pilot pressure of the cutter drum circuit, is changed to the cracking pressure of the pressure-sensitive directional valve of the cutter drum circuit. The cracking pressure of the pressure-sensitive directional valve in the working travel circuit is exceeded before the set value of
Before the pressure sensitive directional control valve in the cut drum circuit is switched to release the swash plate of the hydraulic pump for the cut drum, the pressure sensitive directional valve in the work drive circuit is switched to release the hydraulic pump for work drive. The bias against the swash plate can be released.
That is, when the cutting load increases in this way,
While driving the cutter drum at the same driving speed as before, the working traveling speed can be reduced even though there is a command to tilt the swash plate of the working hydraulic pump.

〔Example〕

The present invention will be described below with reference to the drawings. Reference numeral 1 represents the entire load cutter equipped with the automatic control device of the present invention, 2 is a drive circuit for the cutter drum 3, and 4 is a reciprocating variable displacement type for driving the cutter drum. It is a type hydraulic pump. The hydraulic pump 4 drives a hydraulic motor 5 for driving the cutter drum provided in the cutter drum 3 via pipes 6 and 7, and its drive speed can be variably adjusted by changing the inclination angle of the swash plate 8. That is, by changing the inclination angle of the swash plate 8, the stroke of the piston, etc. of the reciprocating hydraulic pump 4 is changed, and the discharge amount of pressure oil is changed to variably adjust the drive speed. The charge pump 28 connects the pipes 6 and 7 with a pipe 19, a branch pipe 17,
Charge pressure is supplied through 18 to maintain the control pressure of the servo system, and new oil is constantly fed. Further, an oil tank 11 is connected to the suction side of the charge pump 28 via a pipe line 9 and a filter 10 .

12 is a pressure sensitive directional control valve, and 13 is an electromagnetic servo directional control valve. The pressure-sensitive directional control valve 12 receives cutter drum drive pressure through branch pipes 14 and 15 drawn out from the pipes 6 and 7 connecting the hydraulic pump 4 and the hydraulic motor 5, and a pilot pipe 16 which joins these pipes. Derived as pilot pressure. Pressure oil is also supplied to the pressure-sensitive directional control valve 12 from a charge pump 28 via pipes 19 and 20. 21 is a conduit connecting the pressure sensitive directional control valve 12 and the electromagnetic servo directional control valve 13.

Next, the swash plate 8 of the hydraulic pump 4 is connected to the actuator side connection port of the electromagnetic servo directional control valve 13 via a conduit 23 equipped with a throttle 22 and a conduit 25 equipped with a throttle 24. . Furthermore, a pipe line 2 is connected to the tank port of the electromagnetic servo directional control valve 13.
An oil tank 27 is connected through 6.

Therefore, the drive circuit 2 of the katsuta drum explained above
When the electromagnetic servo directional control valve 13 is in the neutral position, no pressure oil acts on the swash plate 8, so the hydraulic motor 5 does not receive the driving force of the hydraulic pump 4. Further, when a swash plate tilting command is input to the electromagnetic servo directional control valve 13, the valve is switched and pressure oil acts on either side of the swash plate 8, and the swash plate is moved by an amount corresponding to the amount of the swash plate tilt command. Balance in a tilted position. As the amount of inclination of the swash plate 8 changes, the driving speed of the hydraulic motor 5 increases. Therefore, if the driving pressure of the hydraulic motor 5 guided to the pipe line 16 exceeds the set value of the cracking pressure of the pressure-sensitive directional valve 12 due to an increase in the cutting load based on changes in the hardness of the road surface, etc., the valve 12 is switched, the action of pressure oil on the swash plate 8 disappears, and the swash plate moves in the direction of returning to the neutral position despite the swash plate tilting command. This slows down the driving speed of the hydraulic motor 5. When the driving pressure of the hydraulic motor 5 becomes less than the set value of the cracking pressure, the valve 12 returns to its original state and the pressure oil increases the angle of inclination of the swash plate 8. In this way, the rotational speed of the hydraulic motor 5 is controlled.

On the other hand, 2a is a drive circuit for operating the running wheels 3a, and this circuit 2a also includes the same structure and operation as described above for the drive circuit for the cutter drum 3. That is, reference numeral 4a denotes a variable displacement reciprocating hydraulic pump for working travel, and the pump 4a drives a working traveling hydraulic motor 5a provided on the traveling wheels 3a via pipes 6a and 7a. The driving speed is variably adjusted by operating the swash plate 8a. A charge pump 28a connects a pipe 19a and a branch pipe 17 to the pipes 6a and 7a.
Charge pressure is supplied through a and 18a. Further, an oil tank 11a is connected to the suction side of the charge pump 28a via a pipe 9a and a filter 10a.

12a is a pressure sensitive directional switching valve, and 13a is an electromagnetic servo directional switching valve. Pressure sensitive directional valve 12
A is a branch pipe 1 drawn out from the pipes 6a and 7a connecting the hydraulic pump 4a and the hydraulic motor 5a.
4a, 15a and a pilot pipe 16a that joins them, the driving wheel drive pressure is introduced as pilot pressure. Also, the pressure sensitive directional valve 12a
In this case, the charge pump 28a connects the pipes 19a, 2
Pressure oil is supplied via 0a. 21a is a pressure sensitive directional control valve 12a and an electromagnetic servo directional control valve 13a.
It is a conduit that connects the

Next, the actuator side connection port of the electromagnetic servo directional control valve 13a has a conduit 2 equipped with a throttle 22a.
The swash plate 8a of the hydraulic pump 4a is connected to the swash plate 8a of the hydraulic pump 4a through a conduit 25a having a conduit 3a and a throttle 24a. Furthermore, an oil tank 27a is connected to the tank port of the electromagnetic servo directional control valve 13a via a conduit 26a.

In the drive circuit 2a during the operation of the traveling wheels described above, the electromagnetic servo directional control valve 1
3a is in the neutral position, pressure oil does not act on the swash plate 8a, so the hydraulic motor 5a
It does not receive the driving force of a. Further, when a swash plate tilting command is input to the electromagnetic servo direction switching valve 13a, the valve is switched and pressure oil acts on either side of the swash plate 8a, and the swash plate is moved by an amount commensurate with the amount of the swash plate tilt command. Balance in a tilted position. The drive speed of the hydraulic motor 5a increases as the amount of inclination of the swash plate 8a changes. Therefore, when the working load increases and exceeds the set value of the cracking pressure of the driving pressure-sensitive directional control valve 12a of the hydraulic motor 5a guided to the pipe line 16a, the valve 12a is switched and the pressure oil is supplied to the swash plate 8a. The action is lost and the swash plate moves in the direction of returning to the neutral position despite the swash plate tilt command. This slows down the driving speed of the hydraulic motor 5a. When the driving pressure of the hydraulic motor 5a becomes less than the set value of the cracking pressure, the valve 12a returns to its original state and the pressure oil increases the inclination angle of the swash plate 8a. In this way,
The working traveling speed is controlled, and in order to control the working traveling speed, the drive circuit 2a in this embodiment further has the following two requirements, and this point is an important feature of the present invention. . That is, first, the set value of the cracking pressure of the pressure-sensitive directional control valve 12a in the drive circuit 2a for work traveling is smaller than the set value of the cracking pressure of the pressure-sensitive directional control valve 12 in the drive circuit 2 for the cutter drum. It is to take it as a value. Second, the pipe line 16a in the work traveling drive circuit 2a and the pipe line 16 in the cutter drum drive circuit 2 are connected through a pipe line 30. By meeting these requirements, when the cutting load increases while the load cutter 1 is running while working, the drive pressure of the hydraulic motor 5 communicating with the pipe 16 exceeds the set value of the cracking pressure of the valve 12. Since the cracking pressure of the valve 12a exceeds the set value, the hydraulic pump 4 for the cutter drum is switched off before the swash plate 8 is released from the swash plate 8 by switching the valve 12a. The biasing force of the swash plate 4a against the swash plate 8a can be released. Therefore, when the cutting load increases in this way, the working traveling speed is reduced, although the cutter drum is driven at the same driving speed as before, even though there is a command to tilt the swash plate 8a of the working hydraulic pump 4a. When the cutting load is reduced to a predetermined value or less due to this deceleration, the valve 12a returns to its normal operation, and the work begins to proceed while increasing the work speed again.

[Effect of idea]

As is clear from the above explanation, the device of the present invention can automatically reduce the working speed when the cutting load increases, and this automatic control is performed while the operating levers of valves 13 and 13a are kept at their maximum values. Therefore, the worker can maximize the capacity of the road cutter and proceed with the work efficiently at the optimum speed without having to operate the control lever while watching the pressure gauge. This is extremely effective in practical terms as it can also reduce costs.

[Brief explanation of drawings]

The drawing is a circuit diagram showing a hydraulic circuit of an automatic working speed control device according to an embodiment of the present invention combined with a side view of a road cutter. 1...Road cutter, 3...Katsuta drum, 3
a... Traveling wheel, 4, 4a... Hydraulic pump, 5,
5a...Hydraulic motor, 8, 8a...Swash plate, 12,
12a...Pressure sensitive directional valve, 13, 13a...
...Electromagnetic servo directional control valve, 30...pipe line.

Claims (1)

[Scope of utility model registration request] A hydraulic motor, a hydraulic pump that can variably adjust the drive speed of the hydraulic motor according to the inclination angle of the swash plate, and an electromagnetic servo direction switch for controlling the inclination angle of the swash plate using pressure oil in a hydraulic system path. and a pressure-sensitive directional control valve that introduces the load pressure applied to the hydraulic motor as a pilot pressure and shuts off the hydraulic line to the electromagnetic servo directional control valve when the pilot pressure exceeds a predetermined pressure. In a road cutter equipped with a cutter drum circuit and a cutter drum circuit having a similar configuration, the pilot pressure line of the pressure-sensitive directional control valve is communicated with the work travel circuit and the cutter drum circuit, and the work travel circuit is connected to the cutter drum circuit. An automatic work speed control device for a road cutter, characterized in that a set value of cracking pressure of a pressure sensitive directional valve in the circuit is set to a value smaller than a set value of cracking pressure of a pressure sensitive directional valve in a cutter drum circuit.