JPH0512327Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a wheel drive device suitable for use in driving the wheels of a leveling machine such as an asphalt finisher or a base paver.

[Prior Art] Conventionally, this type of leveling machine includes a leveling device for leveling the road surface, etc., mounted on a vehicle body equipped with a front wheel for driving and a rear wheel for driving. Something is known.

In such a leveling machine,
Generally, wheel drive devices are provided in which the rear wheels are driven by hydraulic motors, but in such wheel drive devices, the amount of leakage from the hydraulic motor changes when the load resistance applied to the rear wheels changes. The number of rotations of the hydraulic motor will vary, and the running speed of the leveling machine will vary accordingly, which may cause various problems (for example, the thickness of the asphalt may become uneven). It has become essential to add a function to reduce the effect of fluctuations in load resistance on running speed, and wheel drive devices equipped with this function are The present invention provides a system that constantly monitors the number of vehicles using a sensor, etc., and changes the discharge amount of a hydraulic pump that pumps hydraulic fluid to the hydraulic motor based on the output signal of this sensor to prevent fluctuations in traveling speed. ing.

[Problem to be solved by the invention] However, in the conventional wheel drive device described above, it is necessary to calculate the increase/decrease in the hydraulic pump discharge amount with respect to the fluctuation value of the rotation speed of the hydraulic motor, so it is difficult to control the control system. The drawback was that it inevitably became complicated.

This idea was developed against this background, and was designed to suppress fluctuations in the running speed of the leveling machine through simple control without the need for complex calculations as described above. The purpose of the present invention is to provide a wheel drive device that can.

[Means for Solving the Problems] In order to solve the above problems, this invention provides a rear wheel hydraulic motor that drives the rear wheels, and a rear wheel hydraulic pump that pumps hydraulic fluid to the rear wheel hydraulic motor. a front wheel hydraulic motor that drives the front wheels; a front wheel hydraulic pump that pumps hydraulic fluid to the front wheel hydraulic motor;
A pressure switch installed in a rear wheel supply pipe line that supplies hydraulic oil from the rear hydraulic pump to the rear hydraulic motor, and a pressure switch that supplies hydraulic oil from the front hydraulic pump to the front hydraulic motor. The switching valve is disposed in the front wheel side supply line and connects and shuts off the front wheel side supply line based on the output signal of the pressure switch.

[Function] According to the above configuration, the pressure switch detects the pressure increase in the rear wheel supply pipe when a load resistance that changes the rotation speed of the rear wheel hydraulic motor is applied to the rear wheel. The switching valve is switched in accordance with the output signal of the pressure switch, and the front wheel side supply pipe is communicated with the switching valve. Then, hydraulic oil is supplied from the front wheel hydraulic pump to the front wheel hydraulic motor, and the front wheel hydraulic motor is started, thereby reducing the load on the rear wheels and preventing fluctuations in the traveling speed.

[Example] Hereinafter, an example in which the present invention is applied to an asphalt finisher will be described with reference to FIGS. 1 to 3.

As shown in Figures 1 and 2, this asphalt finisher consists of a rear wheel (wheel) 1 and a front wheel 2.
While driving the car body 3 to rotate, the asphalt material put into the hopper 4 is sent to the rear spreading screw 6 by a conveyor (bar feeder) 5, where it is spread uniformly from side to side. A leveling device 8 suspended from the rear of a support arm 7 is configured so that the leveling device 8 can evenly level the pavement on the road surface. In this case, the front wheels 2 are configured to serve both as steering wheels and as driving wheels, but normally only the rear wheels 1 are driven, and the front wheels 2 are driven as necessary.

FIG. 3 shows a hydraulic circuit of a drive system in an asphalt finisher having such a configuration.
In the figure, reference numeral 9 is a hydraulic pump for the front wheels, 10 is a hydraulic pump for the rear wheels, 11 is a hydraulic pump for pilot and fluid replacement, and 12 is a hydraulic pump dedicated to leveling work. , is connected to an engine 13 mounted on the vehicle body 3 of the asphalt finisher (see FIG. 1), and is driven to rotate.

The front wheel hydraulic pump 9 is a unidirectional discharge swash plate type variable displacement hydraulic pump, and a portion of the hydraulic oil discharged from the front wheel hydraulic pump 9 into the pipe line 14 is controlled by electromagnetic proportional control via a pressure reducing valve 15. It is adapted to be guided to a valve 16. And the electromagnetic proportional control valve 16
The downstream side of the solenoid valve 19 is connected to a solenoid valve (switching valve) 19 via conduits 17 and 18, and the downstream side of the solenoid valve 19 drives the front wheel 2 (see Fig. 1) via conduits 20 and 21. The motors are connected to ports 22a and 22b of front wheel hydraulic motors 22 and 22, respectively, which rotate in both directions and are of a constant displacement type. And the above electromagnetic proportional control valve 1
6 is designed to be switched to the side that leads hydraulic oil to the pipe 17 when the asphalt finisher moves forward, and when the electromagnetic valve 19 and the electromagnetic proportional control valve 16 are energized in this state, the pipe 1
7 and 20 act as front wheel side supply pipes that supply hydraulic oil to the front wheel hydraulic motors 22 and 22, causing the front wheel hydraulic motors 22 and 22 to rotate in the normal direction, thereby causing the front wheel 2 (see Fig. 1) to rotate in the normal direction. It's starting to turn around. In addition, the solenoid valve 19 and the solenoid proportional control valve 1
When valve 6 is de-energized, pipes 20 and 21 are connected to solenoid valve 1.
9 through an electromagnetic proportional control valve 16, so that the front wheel hydraulic motors 22, 22 are idled. The remainder of the hydraulic oil discharged from the front wheel hydraulic pump 9 is supplied to a leveling device such as a vibrator (not shown) via pipes 23 and 24.

On the other hand, the rear wheel hydraulic pump 10 is a swash plate type variable displacement hydraulic pump with bidirectional discharge.
The port 10a is a bidirectional rotating variable displacement rear wheel hydraulic motor 2 that drives the rear wheel 1 (see Figure 1).
Ports 25a of 5 and 25, pipe line 26 and diverter valve 2
7 while its second port 1
0b is the port 25b of the hydraulic motor 25, 25
This causes the rear wheel hydraulic motors 25, 25 to rotate forward or reverse in response to switching of the discharge direction of the rear wheel hydraulic pump 10, so that the rear wheel 1 is rotated in the normal direction. It is becoming possible to reverse it. The discharge direction of the rear wheel hydraulic pump 10 is determined so that the rear wheel 1 is rotated in the normal direction when hydraulic oil is discharged from the first port 10a, and in this state, the pipe line 26 is connected to the hydraulic motor 25. , 25 functions as a rear wheel side supply conduit for supplying hydraulic oil.

A pressure switch 29 is connected to the pipe line 26. This pressure switch 29 is designed to output a front wheel drive signal when the hydraulic oil pressure in the pipe line 26 becomes larger than a predetermined set value, and this front wheel drive signal causes the solenoid valve 19 and the solenoid valve to be connected to each other. When the proportional control valve 16 is excited, a portion of the hydraulic fluid discharged from the front hydraulic pump 9 is supplied to the front hydraulic motor 2.
2, 22. Further, a bypass line 30 is provided between the above-mentioned lines 26 and 28, and a bypass valve 31 is provided in this bypass line 30. This bypass valve 31
connects and shuts off the bypass line 30 according to the pilot pressure led from the pilot lines 32 and 33, and when communicating, connects the bypass line 30 from the line 26 as the hydraulic pressure in the line 26 increases. Decreasing the flow rate of hydraulic oil passing through the pipe 28,
Rear wheel hydraulic motor 2 due to pressure increase in pipe line 26
The flow rate of hydraulic oil supplied to the rear wheel hydraulic motors 25, 25 is increased to compensate for the increase in the amount of hydraulic oil leaking from the hydraulic motors 5, 25. Further, a hydraulic oil discharge valve 34 is disposed above the bypass valve 31, and this hydraulic oil discharge valve 34 is connected to the pipes 26, 2.
The hydraulic oil with higher pressure among the 8 hydraulic oils,
It is designed to discharge into the tank T only when the pressure exceeds a predetermined set pressure.

Further, the hydraulic pump 11 is a fixed displacement hydraulic pump with one-way discharge, and the pressure of the hydraulic oil discharged from the hydraulic pump 11 is introduced as pilot pressure to drive the solenoid valve 19 via a pilot pipe 36. It's starting to get worse. Also hydraulic pump 1
The hydraulic pressure discharged by the hydraulic pump 1 is also guided to either of the pilot pipes 37 and 38 which adjust the swash plate angle of the rear wheel hydraulic pump 10 based on the switching position of the proportional control valve 36. As a result, the discharge amount and discharge direction of the rear wheel hydraulic pump 10 are switched, and the rotation speed and rotation direction of the rear wheel hydraulic motors 25, 25 are determined. In addition, when the proportional control valve 36 is in the neutral position, the pilot pipes 37 and 38 are communicated with each other, so that the swash plate angle of the rear wheel hydraulic pump 10 becomes 0 degrees and the discharge of the hydraulic oil is stopped. It's summery. Further, the downstream side of the proportional control valve 36 is a solenoid valve 39.
The pilot pipes 37 and 38 are connected to each other even when the solenoid valve 39 is energized, so that the discharge of hydraulic fluid from the rear wheel hydraulic pump 10 is stopped. The hydraulic oil discharged from the hydraulic pump 11 is then passed through the conduit 40 to the solenoid valve 41.
~45 is also supplied. The solenoid valve 41 switches the pilot pressure of the bypass valve 31, and when the solenoid valve 41 is energized, the bypass valve 3
The discharge pressure of the hydraulic pump 11 is introduced to the first pilot line 32, thereby driving the bypass valve 31 and shutting off the bypass line 30. Further, the solenoid valve 42 is used to replenish hydraulic oil to the front wheel drive system mentioned above and to stop replenishment, and when the solenoid valve 42 is de-energized, the hydraulic pump 1
Hydraulic oil discharged from 1 is supplied to the pipes 20 and 21 via check valves 46 and 47, and supply is stopped during excitation. Further, the solenoid valve 43 is adapted to switch the flow divider valve 27 by guiding the discharge pressure of the hydraulic pump 11 to the flow divider valve 27 as a pilot pressure. Further, the solenoid valve 44 switches the pressure in the pilot line 48 that brakes the rotation of the rear wheel hydraulic motors 25, 25, and when the solenoid valve 44 is energized, the pressure in the braking pilot line 48 is released to the tank T. The rotation of the rear wheel hydraulic motors 25, 25 is braked, and when de-energized, the discharge pressure of the hydraulic pump 11 is guided to the pilot pipe 48 to brake the rotation of the rear wheel hydraulic motors 25, 2.
5 brake is now released. The solenoid valve 45 switches the swash plate angle of the rear wheel hydraulic motors 25, 25 between high and low speeds, and when the solenoid valve 45 is not energized, the discharge pressure of the hydraulic pump 11 is guided to the pilot pipe 49. The pilot line 50 is opened to the tank T, and the hydraulic motor 25,
The angle of the swash plate 25 is switched to the low speed side, and during excitation, the pressure in the pilot lines 49 and 50 is switched to the opposite of the above-mentioned low speed, and the pressure of the rear wheel hydraulic motor 2 is switched to the low speed side.
The swash plate angles 5 and 25 can be switched to the high speed side.

Note that reference numeral 51 in the figure is a control valve that controls the discharge pressure and discharge amount of the front wheel hydraulic pump 9 based on fluctuations in the load pressure applied to the front wheel drive system. Also,
Reference numerals 52 and 53 are pressure release valves that release surge pressure in the pipes 26 and 28, and a portion of the hydraulic fluid discharged from the hydraulic pump 11 is supplied to these pressure release valves 53, 53.
Each of the above pipes 2 through check valves 54 and 55 in 53
It is scheduled to be replenished on June 6, 28.

Next, the operation of the asphalt finisher constructed as described above will be explained.

When performing leveling work, the solenoid valve 41 and the solenoid valve 45 are de-energized in advance and held in the normal position, thereby switching the bypass valve 31 to a position where the bypass pipe line 30 is communicated with, and also switching the bypass valve 31 to the position where the bypass pipe line 30 is communicated with. While the swash plate angles of the hydraulic motors 25, 25 are switched to the low speed side, the electromagnetic proportional control valve 16 is switched to the side where the hydraulic fluid discharged from the front wheel hydraulic pump 9 is guided to the pipe line 17.

To start work from the above state, first energize the solenoid valve 39 to cut off communication between the pilot pipes 37 and 38, and then open the proportional control valve 3.
6 to the specified position. Then, the discharge pressure of the hydraulic pump 11 is guided to the pilot line 37 as a pilot pressure, and this pilot pressure sets the swash plate angle of the rear wheel hydraulic pump 10 to a predetermined angle. 1 port 10a
A predetermined amount of hydraulic oil is discharged from. The hydraulic oil discharged from the rear wheel hydraulic pump 10 is guided to the port 25a of the rear wheel hydraulic motors 25, 25 while its flow rate is adjusted by the bypass valve 31. 25 is rotated forward at a constant speed, the asphalt finisher moves forward at a low speed, and leveling work is performed by the leveling device 8 or the like. Here, if the load resistance applied to the leveling device 8 during the leveling work is not large enough to change the rotation speed of the rear wheels 1, the pressure in the pipe line 26 will hardly increase, so the pressure in the pipe line 26 will be The installed pressure switch 29 does not react at all and the solenoid valve 1
9 is held in a de-energized state. Therefore, the hydraulic fluid discharged from the front wheel hydraulic pump 9 is blocked by the electromagnetic proportional control valve 16, and is then transferred to the front wheel hydraulic motors 22, 22.
As a result, the front wheel hydraulic motor 2
Hydraulic oil circulates between the front wheel motors 2, 22 and the solenoid valve 19, so that the front wheel motors 22, 22 are maintained in a freely rotating state. On the other hand, when the load resistance applied to the leveling device 8 becomes large enough to change the rotation speed of the rear wheels 1, the conduit acting as the rear wheel side supply conduit increases as the load resistance increases. 26 increases, and in conjunction with this, a front wheel drive signal is output from the pressure switch 29, and the electromagnetic valve 19 and the electromagnetic proportional control valve 16 are energized. Then, the hydraulic oil led from the front wheel hydraulic pump 9 is supplied to the conduit 20 via the solenoid valve 19 and the electromagnetic proportional control valve 16, and the front wheel hydraulic motors 22, 22 are started, thereby causing the rear wheel 1 to be supplied with hydraulic oil. This load is reduced and fluctuations in the running speed of the asphalt finisher are prevented.

In addition, when the asphalt finisher is run at high speed for forwarding, etc., the solenoid valves 41 and 4 are
5 is excited to connect the bypass valve 31 to the bypass pipe 30.
At the same time, the swash plate angles of the rear wheel hydraulic motors 25, 25 are switched to the high speed side. Then, the rear wheel hydraulic motors 25, 25 are driven at high speed by the entire flow rate of the hydraulic oil discharged by the rear wheel hydraulic pump 10, and in addition, at this time, the load applied to the rear wheel 1 is kept almost constant. Therefore, the hydraulic oil pressure in the pipe line 26 does not increase and the front wheel hydraulic motor 22,
22 is maintained in a freely rotating state, and as a result, the asphalt finisher is efficiently driven at high speed.

As described above, the wheel drive device of this embodiment uses the pressure switch 29 to detect the pressure increase in the conduit 26 when a load resistance that changes the rotation speed of the rear wheel 1 is applied during leveling work. And this pressure switch 29
The solenoid valve 19 responds to the front wheel drive signal output from the
By energizing the electromagnetic proportional control valve 16, the front wheel hydraulic motors 22, 22 are driven to reduce the load on the rear wheels 1, so the control device includes a pressure switch 29, an electromagnetic valve 19, and an electromagnetic proportional control valve 16. Simple control such as connecting the proportional control valve 16 is sufficient, and complex control such as calculating the increase/decrease in the hydraulic pump discharge amount based on the fluctuation value of the hydraulic motor rotation speed, as in the conventional wheel drive device described above, is not necessary. I don't need anything.

Note that the configurations such as the circuit arrangement of each hydraulic pump and hydraulic motor in the above embodiments are merely examples; for example, the number of front wheel hydraulic motors and rear wheel hydraulic motors may be changed, or the number of front and rear wheels may be changed. Naturally, the design of these configurations can be changed in accordance with the leveling machine in which the wheel drive device of the present invention is mounted.

[Effects of the invention] As explained above, the wheel drive device of the invention detects the pressure increase in the rear wheel side supply pipe using the pressure switch, and switches the switching valve based on the output signal of this pressure switch. This system starts the hydraulic motor for the front wheels, so when a load that changes the running speed is applied to the rear wheels, the front wheels are started immediately, reducing the load on the rear wheels and reducing the fluctuations in the running speed. is prevented. The control in this case is extremely simple, simply by interlocking the pressure switch and the switching valve. Therefore, according to the present invention, the hydraulic pump discharge amount corresponding to the fluctuation value of the hydraulic motor rotation speed can be controlled as required by the conventional method. It is possible to realize a wheel drive device that can suppress fluctuations in traveling speed without using complicated control such as calculating the increments and decrement of .

[Brief explanation of the drawing]

Figures 1 to 3 are views showing one embodiment of the present invention, in which Figure 1 is a side view of an asphalt finisher, Figure 2 is a plan view of the asphalt finisher, and Figure 3 is a drive device of the same. FIG. 1... Rear wheel, 2... Front wheel, 9... Hydraulic pump for front wheels, 10... Hydraulic pump for rear wheels, 17, 20...
... Pipe line (front wheel side supply pipe line), 19... Solenoid valve (switching valve), 26... Pipe line (rear wheel side supply pipe line), 29...
...Pressure switch.

Claims (1)

[Scope of utility model registration request] A wheel drive device for a leveling machine including a front wheel for traveling and a rear wheel for driving, the rear wheel hydraulic motor driving the rear wheel, and the hydraulic fluid being pumped to the rear wheel hydraulic motor. a front wheel hydraulic pump that drives the front wheels; a front wheel hydraulic pump that pumps hydraulic fluid to the front wheel hydraulic motor; and a front wheel hydraulic pump that pumps hydraulic fluid to the front wheel hydraulic motor; a pressure switch disposed in a rear wheel side supply conduit for supplying hydraulic oil; and a pressure switch disposed in a front wheel side supply conduit for supplying hydraulic oil from the front wheel hydraulic pump to the front wheel hydraulic motor. A wheel drive device for a leveling machine, comprising a switching valve that connects and shuts off the front wheel side supply pipe based on the output signal of the leveling machine.