JP2000081108A - Hydrostatic transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit the drive force of a power source directly to the hydraulic motor side during high speed running while characteristics, such as continuously variable shifting, is maintained during low speed running. SOLUTION: A controller C brings a clutch mechanism 6 into a contact state when a difference between the number of revolutions of a variable volume type pump 1 detected by number of revolutions sensors 18 and 19 and the number of revolutions of a hydraulic motor 3 is reduced approximately to zero. Besides, approximately at the same time when the clutch mechanism 6 is brought into a contact state, a communication valve 14 is switched to a communication position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrostatic transmission device used as a drive mechanism for a working vehicle such as a road roller.

[0002]

2. Description of the Related Art Although not specifically shown, a hydrostatic transmission device has a closed circuit constituted by a variable displacement pump and a hydraulic motor. That is, when the variable displacement pump is rotated by the driving force of the engine, the variable displacement pump discharges hydraulic oil according to the inclination of the swash plate. Then, the hydraulic motor is rotated by the discharged oil to drive the vehicle,
The hydraulic oil discharged from the hydraulic motor is returned to the variable displacement pump.

[0003] In such a hydrostatic transmission device, if the engine speed is kept constant, the variable displacement pump also rotates at a constant speed. And
In this state, if the swash plate of the variable displacement pump is tilted to control the discharge amount from the minimum to the maximum, the rotation speed of the hydraulic motor can be continuously controlled. Therefore, stepless speed change is possible, and for example, smooth start, acceleration, and deceleration can be realized. If the inclination of the swash plate of the variable displacement pump is reversed, the discharge direction can be reversed. Therefore, the vehicle can be made to travel forward or backward by rotating the hydraulic motor in both the forward and reverse directions.

[0004]

In such a hydrostatic transmission device as described above, a characteristic such as a continuously variable transmission becomes very effective especially at a low vehicle speed where the transmission is frequently changed. However, since the driving force of the engine is transmitted to the hydraulic motor side indirectly via the hydraulic oil instead of directly, the transmission efficiency is poor, and the fuel efficiency is poor. When the vehicle normally travels at a high vehicle speed, there is almost no need for shifting, and the disadvantage that transmission efficiency is worse than the characteristic of stepless shifting is a serious problem. The purpose of this invention is
At low vehicle speeds, while maintaining characteristics such as stepless shifting, at high vehicle speeds, the driving force of the power source is transmitted directly to the hydraulic motor side, thereby avoiding deterioration in transmission efficiency. It is to provide a hydrostatic transmission device.

[0005]

SUMMARY OF THE INVENTION A first aspect of the present invention provides a variable displacement pump which is associated with a power source which rotates in one direction, and which changes a discharge amount and a discharge direction in accordance with the inclination of a swash plate. Motor, a forward traveling line connecting one port of the variable displacement pump to one port of the hydraulic motor, and connecting the other port of the variable displacement pump to the other port of the hydraulic motor. And a hydrostatic transmission device having a reverse traveling line. A clutch mechanism that transmits the driving force of the power source to the fluid pressure motor in the contact state and cuts off the transmission in the cutoff state, and a clutch disconnection that brings the clutch mechanism into contact or cutoff state by pressure action. A contacting mechanism, a control pump that rotates together with the variable displacement pump, a switching valve that guides the discharge pressure of the control pump to the clutch connecting / disconnecting mechanism, and connects the clutch connecting / disconnecting mechanism to the tank; A communication line that communicates with the traveling line, a communication valve that communicates the communication line at the communication position, and shuts off the communication line at the shutoff position, a rotation speed sensor that detects the rotation speed of the variable displacement pump, and a fluid pressure motor. A rotation speed sensor for detecting the rotation speed,
The controller switches the switching valve when the difference between the rotation speed of the variable displacement pump detected by the rotation speed sensor and the rotation speed of the fluid pressure motor becomes substantially zero, and changes the discharge pressure of the control pump to a clutch connection / disconnection mechanism. Or the clutch connecting / disconnecting mechanism is connected to the tank to bring the clutch mechanism into contact, and at the same time as the clutch mechanism comes into contact, the communication valve is switched to the communication position. It is characterized by the following points.

According to a second aspect of the present invention, in the first aspect, a tilt angle sensor for detecting a tilt angle of the variable displacement pump is provided, and a controller of the variable displacement pump detected by the rotation speed sensor is provided. Only when the difference between the rotation speed and the rotation speed of the fluid pressure motor becomes almost zero and the tilt angle of the variable displacement pump reaches the set angle, the switching valve is switched, and the discharge pressure of the control pump is disconnected and connected. Leading to the mechanism, or
It is characterized in that the clutch connecting / disconnecting mechanism is connected to the tank to bring the clutch mechanism into a contact state.

A third invention relates to a variable displacement pump which is linked to a power source which rotates in one direction and changes the discharge amount and discharge direction in accordance with the inclination of a swash plate, and a fluid pressure motor which permits flow in both directions. A forward traveling line connecting one port of the variable displacement pump to one port of the hydraulic motor, and a reverse traveling line connecting the other port of the variable displacement pump to the other port of the hydraulic motor. It is assumed that a hydrostatic transmission device equipped with this is used. A clutch mechanism that transmits the driving force of the power source to the fluid pressure motor in the contact state and cuts off the transmission in the cutoff state, and a clutch disconnection that brings the clutch mechanism into contact or cutoff state by pressure action. A contacting mechanism, a control pump that rotates together with the variable displacement pump, a switching valve that guides the discharge pressure of the control pump to the clutch connecting / disconnecting mechanism, and connects the clutch connecting / disconnecting mechanism to the tank; A communication line that communicates with the traveling line, a communication valve that communicates the communication line at the communication position, and a communication valve that shuts off the communication line at the shutoff position, and a tilt angle sensor that detects a tilt angle of the variable displacement pump; When the tilt angle detected by the tilt angle sensor reaches the set angle, the controller switches the switching valve, and uses the discharge pressure of the control pump as the pilot pressure to crack. Lead to disengaging mechanism, or,
The clutch connection / disconnection mechanism communicates with the tank to bring the clutch mechanism into contact, and at the same time as the clutch mechanism comes into contact, the communication valve switches to the communication position. Have.

[0008]

FIG. 1 shows a first embodiment of a hydrostatic transmission device according to the present invention.
The variable displacement pump 1 is linked to an engine E as its power source. Then, one port 1 a of the variable displacement pump 1 is connected to one port 3 a of the hydraulic motor 3 via the forward traveling line 2. Further, the other port 1b of the variable displacement pump 1 is connected to the other port 3b of the hydraulic motor 3 via the reverse traveling line 4. Therefore, the variable displacement pump 1 and the hydraulic motor 3 form a closed circuit.

When the engine E is driven, the variable displacement pump 1 is rotated in the rotation direction of the engine E. When the swash plate of the variable displacement pump 1 is tilted in the forward traveling range as shown in FIG. 1, the variable displacement pump 1 discharges hydraulic oil from the port 1a to the forward traveling line 2 side. Therefore, according to the discharge amount, the hydraulic motor 3
Rotates forward, causing the vehicle to travel forward. Also, if the swash plate of the variable displacement pump 1 is inclined in the reverse traveling range as shown in FIG.
Is discharged in the opposite direction, and hydraulic oil is discharged from the port 1b to the reverse traveling line 4 side. Therefore, the hydraulic motor 3 rotates in the reverse direction according to the discharge amount, and the vehicle travels backward.

Further, in the first embodiment, unlike the conventional hydrostatic transmission device,
The hydraulic motor 3 is connected to a variable displacement pump 1 via a shaft 5.
It is linked to the side. However, a clutch mechanism 6 is provided in the middle of the shaft 5. As the clutch mechanism 6,
Although not specifically shown, a friction clutch system is employed. And if this clutch mechanism 6 is in a contact state,
The driving force of the engine E is transmitted to the hydraulic motor 3, and if it is in a cutoff state, the transmission is cut off.

The clutch mechanism 6 as described above is brought into a contact state or a disconnected state by the cylinder 7 and the spring 8. Bottom chamber 7a of cylinder 7
When the pressure guided to the clutch mechanism 6 is low, the clutch mechanism 6 is kept in the disconnected state by the spring 8. On the other hand, when the pressure guided to the bottom chamber 7a of the cylinder 7 increases, the cylinder 7 operates against the spring 8 to bring the clutch mechanism 6 into a contact state and transmit the driving force of the engine E to the hydraulic motor 3. I am trying to do it. Note that these cylinders 7
The spring 8 constitutes a clutch connection / disconnection mechanism according to the present invention.

On the other hand, a control pump 9 is connected to the variable displacement pump 1. Therefore, the control pump 9 is driven by the driving force of the engine E to control the variable displacement pump 1.
Rotates with. Then, the suction port 9a of the control pump 9 is connected to the tank, and the discharge port 9b
Is connected to a switching valve 10 described below.

The switching valve 10 is in a low vehicle speed switching position in a normal state maintained by a spring 11, as shown in FIG. At this low vehicle speed switching position, the discharge port 9b of the control pump 9 and the bottom chamber 7a of the cylinder 7 communicate with the tank. Then, when the solenoid 12 is excited, it switches to the high vehicle speed switching position.
In the high vehicle speed switching position, the discharge port 9b of the control pump 9 communicates with the bottom chamber 7a of the cylinder 7, and the bottom chamber 7a of the cylinder 7 is shut off from the tank.

Further, there is provided a communication line 13 which connects the two traveling lines 2 and 4. And this communication line 1
3 is provided with a communication valve 14. Communication valve 14
Is in the normal state held by the spring 15,
As shown in FIG. 1, the communication line 13 is in a blocking position for blocking the communication line 13. Then, when the solenoid 16 is excited, the position is switched to a communication position where the communication line 13 is communicated.

Here, a tilt angle sensor 17 for detecting the tilt angle of the variable displacement pump 1 and a rotation speed sensor 18 for detecting the rotation speed of the variable displacement pump 1 are provided. The detected result is input to the controller C. Further, a rotation speed sensor 19 for detecting the rotation speed of the hydraulic motor 3 is provided, and the result detected by this sensor 19 is
Input to controller C. As will be described later in detail, the controller C excites the solenoid 12 of the switching valve 10 and the solenoid 16 of the communication valve 14 in accordance with the detection results of the sensors 17, 18, and 19.

Next, the operation of the hydrostatic transmission of the first embodiment will be described. Hereinafter, a case where the swash plate of the variable displacement pump 1 is inclined in the forward traveling range of the vehicle will be described. In a work vehicle such as a road roller, the running speed of the engine E is kept constant and the variable displacement pump 1 is kept rotating at a constant speed. When changing the vehicle speed, the swash plate of the variable displacement pump 1 is operated by moving an operation lever (not shown). Here, when the swash plate of the variable displacement pump 1 is inclined at a set angle, the discharge amount of the variable displacement pump 1 is made to substantially match the displacement of the hydraulic motor 3. The set angle is set to a substantially maximum angle, in other words, an angle at which the discharge amount of the variable displacement pump 1 becomes substantially maximum.

First, the operation when the swash plate of the variable displacement pump 1 is inclined in the range from the minimum angle to the set angle will be described. When tilting the swash plate of the variable displacement pump 1 in a range from the minimum angle to the set angle, the variable displacement pump 1
Is smaller than the capacity of the hydraulic motor 3. That is, the variable displacement pump 1 rotates more than one rotation to rotate the hydraulic motor 3 one rotation,
A difference occurs between the rotation speed of the variable displacement pump 1 and the rotation speed of the hydraulic motor 3.

The controller C knows from the detection results of the rotation speed sensors 18 and 19 that the rotation speed of the variable displacement pump 1 is higher than the rotation speed of the hydraulic motor 3. At this time, the controller C does not excite the solenoid 12 of the switching valve 10 and the solenoid 16 of the communication valve 14, and keeps the valves 10, 14 in a normal state. Therefore, as shown in FIG. 1, the switching valve 10 is in the low vehicle speed switching position, and the communication valve 14 is in the shut-off position.

If the switching valve 10 is at the low vehicle speed switching position, the bottom chamber 7a of the cylinder 7 communicates with the tank, so that the clutch mechanism 6 is kept closed by the spring 8 and the hydraulic motor 3 is driven by the variable displacement pump. It can be shut off from one side. Further, if the communication valve 14 is at the shut-off position, the traveling lines 2 and 4 can be shut off while the communication line 13 is shut off.

As described above, when the swash plate of the variable displacement pump 1 is tilted in the range from the minimum angle to the set angle,
That is, when the vehicle is traveling at a low vehicle speed, the clutch mechanism 6 is in the disconnected state, and the communication valve 14 is in the disconnected position. Therefore, it functions as a normal hydrostatic transmission device, and continuously controls the rotation speed of the hydraulic motor 3 according to the inclination of the swash plate of the variable displacement pump 1 to enable stepless transmission.

Next, the operation when the swash plate of the variable displacement pump 1 is inclined beyond the set angle will be described. When the swash plate of the variable displacement pump 1 is tilted at the set angle, the discharge amount of the variable displacement pump 1 substantially matches the displacement of the hydraulic motor 3 as described above. In other words, the variable displacement pump 1 also makes one revolution in order to make the hydraulic motor 3 make one revolution, so that the difference between the revolution speed of the variable displacement pump 1 and the revolution speed of the hydraulic motor 3 becomes almost the same. .

Then, the controller C knows from the detection results of the rotation speed sensors 18 and 19 that the difference between the rotation speed of the variable displacement pump 1 and the rotation speed of the hydraulic motor 3 has become almost zero. At this time, the controller C operates the switching valve 1
0 solenoid 12 and communication valve 14 solenoid 16
To switch the switching valve 10 to the high vehicle speed switching position and the communication valve 14 to the communication position.

When the switching valve 10 is switched to the high vehicle speed switching position, the bottom chamber 7a of the cylinder 7 is shut off from the tank, and the discharge oil of the control pump 9 is guided to the bottom chamber 7a. Therefore, the cylinder 7 operates against the spring 8 to bring the clutch mechanism 6 into a contact state, thereby transmitting the driving force of the engine E to the hydraulic motor 3. Note that a relief valve 20 is connected to the discharge port 9b side of the control pump 9 so that the pressure guided to the bottom chamber 7a of the cylinder 7 does not increase more than necessary.
When the communication valve 14 is switched to the communication position, the communication line 13 communicates, and the two traveling lines 2 and 4 communicate.

As described above, when the swash plate of the variable displacement pump 1 is inclined beyond the set angle, that is, when the vehicle is running at a high vehicle speed, the clutch mechanism 6 is brought into the contact state to reduce the driving force of the engine E. Power can be transmitted to the hydraulic motor 3 via the shaft 5. Therefore, the driving force of the engine E can be transmitted to the output side most efficiently, and almost no energy loss occurs. Further, since the communication valve 14 is switched to the communication position, the two traveling lines 2 and 4 communicate with each other via the communication line 13. Accordingly, the two traveling lines 2 and 4 have the same pressure, and the hydraulic motor 3 is not rotated by the discharge oil of the variable displacement pump 1, and there is no possibility that the transmission efficiency is impaired there.

In the first embodiment, the tilt angle of the variable displacement pump 1 is also detected by using the tilt angle sensor 17. In practice, not only does the difference between the rotation speed of the variable displacement pump 1 and the rotation speed of the hydraulic motor 3 become almost zero as described above, but also the tilt angle of the variable displacement pump 1 becomes the set angle. As a condition, the controller C excites the solenoid 12 of the switching valve 10 and the solenoid 16 of the communication valve 14 to switch the switching valve 10 to the high vehicle speed switching position to bring the clutch mechanism 6 into contact, Further, the communication valve 14 is switched to the communication position. Hereinafter, the reason why the AND circuit is configured using not only the rotation speed sensors 18 and 19 but also the tilt angle sensor 17 will be described.

As described above, when the vehicle travels from the low vehicle speed to the high vehicle speed, there is no problem if the control is performed based only on the rotation speed sensors 18 and 19, but the vehicle travels at a low vehicle speed after the high vehicle speed travel. At this time, the control cannot be performed based on the rotation speed sensors 18 and 19. In other words, once the clutch mechanism 6 is brought into the contact state, even if the tilt angle of the variable displacement pump 1 is reduced in order to reduce the vehicle speed, the hydraulic motor 3 remains rotating together with the variable displacement pump 1. . Therefore, there is no difference between the rotation speed of the variable displacement pump 1 and the rotation speed of the hydraulic motor 3, and the rotation speed sensors 18 and 19
If the control is based on only
The clutch mechanism 6 remains in the contact state.

Therefore, a tilt angle sensor 17 is provided to transmit the tilt angle of the variable displacement pump 1 to the controller C. By doing so, the controller C
Is communicated with the solenoid 12 of the switching valve 10 even if there is no difference between the rotation speed of the variable displacement pump 1 and the rotation speed of the hydraulic motor 3 if the tilt angle of the variable displacement pump 1 becomes smaller than the set angle. The solenoid 16 of the valve 14 can be de-energized, the clutch mechanism 6 can be turned off, and the communication valve 14 can be switched to the communication position to return to a normal hydrostatic transmission device.

The case in which the vehicle travels forward has been described above. However, when the vehicle travels backward, it is unlikely that the vehicle will run at a high speed. Therefore, the hydraulic motor 3 is directly rotated by the driving force of the engine E. There is no need. Therefore, in the first embodiment, whenever the vehicle travels backward,
It functions as a normal hydrostatic transmission device. That is, when the swash plate of the variable displacement pump 1 is in the reverse traveling range, it is detected by the tilt angle sensor 17 and transmitted to the controller C. Then, at this time, even if the rotation speed of the variable displacement pump 1 and the rotation speed of the hydraulic motor 3 match, the controller C operates the solenoid 12 of the switching valve 10 and the communication valve 1.
The fourth solenoid 16 is not excited, and functions as a normal hydrostatic transmission device.

In the second embodiment shown in FIG.
4 is switched by using the discharge oil of the control pump 9 instead of being switched by the solenoid 16. That is, similarly to the first embodiment, when the swash plate of the variable displacement pump 1 is tilted to the set angle, the rotation speed of the variable displacement pump 1 and the rotation speed of the hydraulic pump 3 match.
Excites the solenoid 12 of the switching valve 10 to switch the switching valve 10 to the high vehicle speed switching position.

When the switching valve 10 is switched to the high vehicle speed switching position, the discharge oil of the control pump 9 is guided to the bottom chamber 7a of the cylinder 7 as in the first embodiment, and the clutch mechanism 6
To the contact state, and the driving force of the engine E is
To communicate. When the switching valve 10 is switched to the high vehicle speed switching position, the discharge oil of the control pump 9 is also guided to the pilot chamber 21 of the communication valve 14. Therefore, the communication valve 14 can be switched to the communication position almost simultaneously with the clutch mechanism 6 being brought into the contact state.

In the third embodiment shown in FIG. 3, the rotation speed sensors 18 and 19 are not provided, and the control is performed based only on the tilt angle sensor 17. That is, when the tilt angle sensor 17 detects that the tilt angle of the variable displacement pump 1 is in the range from the minimum angle to the set angle, the controller C sets the solenoids 12 and 16 to the non-excited state, Function as a hydrostatic transmission device. When the tilt angle sensor 17 detects that the tilt angle of the variable displacement pump 1 has exceeded the set angle, the controller C excites the solenoids 12 and 16 to bring the clutch mechanism 6 into a contact state. While transmitting the driving force of the engine E to the hydraulic motor 3, the communication valve 1
4 is switched to the communication position so that the two traveling lines 2 and 4 communicate with each other.

As in the third embodiment, the tilt angle sensor 1
7, the same effect as in the first embodiment can be obtained. In addition, cost can be reduced by reducing the number of sensors. However, this third
The control is performed based only on the tilt angle sensor 17 as in the embodiment, and the rotation speed sensor 1 is controlled as in the first embodiment.
The following differences can be considered between the control based on 8, 19 and the tilt angle sensor 17.

For example, if used for a long period of time, the pump efficiency of the variable displacement pump 1 may deteriorate due to deterioration or the like. When the pumping efficiency of the variable displacement pump 1 is deteriorated, a difference between the discharge amount of the variable displacement pump 1 and the displacement of the hydraulic motor 3 occurs even when the swash plate of the variable displacement pump 1 is tilted at a set angle. Then, a difference occurs between the two rotation speeds. In this case, if control is performed based only on the tilt angle sensor 17, the rotational speed of the variable displacement pump 1 and the hydraulic pump 3
The clutch mechanism 6 is brought into a contact state in a situation where the rotation speeds do not match, and a shock may occur. On the other hand, if control is performed based on the rotation speed sensors 18 and 19, the clutch mechanism 6 is brought into the contact state only when the rotation speed of the variable displacement pump 1 and the rotation speed of the hydraulic pump 3 match. This can prevent a shock from occurring.

In the fourth embodiment shown in FIG. 4, a charge pump 22 is used as a control pump. That is,
In the hydrostatic transmission device, since the operating oil circulates through the closed circuit, a problem such as heat generation occurs. In order to avoid the problem, in most cases, as shown in FIG.
, And the discharge oil of the charge pump 22 is supplied to a closed circuit via check valves 23 and 24. Although not specifically shown, the same amount of hydraulic oil as supplied from the charge pump 22 is returned from the closed circuit to the tank.

In the fourth embodiment, the charge pump 22 is used as a control pump. In this case, when the charge pump 22 communicates with the tank,
It will not function as the charge pump 22. Therefore, as shown in FIG. 4, when the switching valve 10 is in the low vehicle speed switching position, the bottom side chamber 7a of the cylinder 7 communicates with the tank as in the other embodiments. The pump 22 is shut off from the tank. In the fourth embodiment, since the charge pump 22 is used, it is not necessary to newly provide a control pump, and it is possible to avoid an increase in cost.

In the fifth embodiment shown in FIG. 5, an auxiliary transmission 25 is added to the output shaft of the hydraulic motor 3. In the fifth embodiment as described above, by changing the mode of the auxiliary transmission 25, the rotational output of the hydraulic motor 3 is reduced and transmitted to the wheels (not shown) to generate a large torque. Can be transmitted to the wheels by increasing the rotation speed of the hydraulic motor 3.

In the sixth embodiment shown in FIG. 6, the variable displacement pump 1 and the
This is the one to which the auxiliary transmission 25 is added. In the sixth embodiment, when the clutch mechanism 6 is in the contact state,
By the auxiliary transmission 25, the driving force of the engine E can be reduced and transmitted to the hydraulic motor 3 or, conversely, the driving force of the engine E can be increased and transmitted to the hydraulic motor 3.

[0038]

According to the first and third aspects of the present invention, when the vehicle is running at a low vehicle speed, the clutch mechanism is in the disconnected state, and the communication valve is in the disconnected position. Therefore, it functions as a normal hydrostatic transmission device, and continuously controls the rotation speed of the fluid pressure motor according to the inclination of the swash plate of the variable displacement pump, thereby enabling stepless transmission. On the other hand, when the vehicle travels at a high vehicle speed, the clutch mechanism is brought into a contact state, and the driving force of the power source can be directly transmitted to the fluid pressure motor. Further, since the communication valve is switched to the communication position, the two traveling lines have the same pressure, and the fluid pressure motor does not rotate by the discharge fluid of the variable displacement pump, and there is no possibility that the transmission efficiency is impaired there. According to the second aspect, in the first aspect, even when the tilt angle of the variable displacement pump is reduced to reduce the vehicle speed after the clutch mechanism is brought into the contact state once, the clutch mechanism is brought into the disconnected state. can do.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a hydrostatic transmission device according to a first embodiment.

FIG. 2 is a circuit diagram showing a hydrostatic transmission device according to a second embodiment.

FIG. 3 is a circuit diagram showing a hydrostatic transmission device according to a third embodiment.

FIG. 4 is a circuit diagram showing a hydrostatic transmission device according to a fourth embodiment.

FIG. 5 is a circuit diagram showing a hydrostatic transmission device according to a fifth embodiment.

FIG. 6 is a circuit diagram showing a hydrostatic transmission device according to a sixth embodiment.

[Explanation of symbols]

 E Engine C Controller 1 Variable displacement pump 1a, 1b port 2 Forward traveling line 3 Hydraulic motor 3a, 3b port 4 Reverse traveling line 6 Clutch mechanism 7 Cylinder 8 Spring 9 Control pump 10 Switching valve 11 Spring 12 Solenoid 13 Communication line 14 Communication Valve 15 Spring 16 Solenoid 17 Tilt angle sensor 18, 19 Rotation speed sensor 21 Pilot room

Claims (3)

[Claims] 1. A variable displacement pump which is linked to a power source rotating in one direction and changes a discharge amount and a discharge direction in accordance with a tilt of a swash plate, a fluid pressure motor permitting flow in both directions, and a variable displacement pump. Hydrostatic having a forward traveling line connecting one port of a hydraulic pump to one port of a hydraulic motor, and a reverse traveling line connecting the other port of the variable displacement pump to the other port of the hydraulic motor In a transmission device, a clutch mechanism that transmits a driving force of a power source to a fluid pressure motor in a contact state and interrupts the transmission in a disconnected state, and brings the clutch mechanism into a contact state or a disconnected state by a pressure action. A clutch connecting / disconnecting mechanism, a control pump that rotates together with the variable displacement pump, and a control pump discharge pressure guided to the clutch connecting / disconnecting mechanism, A switching valve for communicating the clutch connecting / disconnecting mechanism to the tank, a communication line for communicating the forward traveling line and the reverse traveling line, a communication valve for communicating the communication line at the communication position, and disconnecting the communication line at the disconnection position A rotational speed sensor for detecting the rotational speed of the variable displacement pump, and a rotational speed sensor for detecting the rotational speed of the fluid pressure motor, wherein the controller detects the rotational speed of the variable displacement pump detected by the rotational speed sensor. When the difference between the rotation speed of the motor and the fluid pressure motor becomes substantially zero, the switching valve is switched, and the discharge pressure of the control pump is led to the clutch connecting / disconnecting mechanism, or the clutch connecting / disconnecting mechanism is connected to the tank, and the clutch is connected. The mechanism is configured to be in the contact state, and the communication valve is switched to the communication position almost simultaneously with the clutch mechanism being in the contact state. B static transmission equipment. 2. A tilt angle sensor for detecting a tilt angle of the variable displacement pump, wherein the controller is configured to determine a difference between the rotation speed of the variable displacement pump detected by the rotation speed sensor and the rotation speed of the fluid pressure motor. Is almost zero, and only when the tilt angle of the variable displacement pump reaches the set angle, the switching valve is switched, and the discharge pressure of the control pump is led to the clutch connection / disconnection mechanism,
2. The hydrostatic transmission device according to claim 1, wherein the clutch connecting / disconnecting mechanism is connected to the tank to bring the clutch mechanism into a contact state. 3. A variable displacement pump which is linked to a power source rotating in one direction and changes the discharge amount and discharge direction in accordance with the inclination of the swash plate, a fluid pressure motor which permits flow in both directions, and a variable displacement pump. Hydrostatic having a forward traveling line connecting one port of a hydraulic pump to one port of a hydraulic motor, and a reverse traveling line connecting the other port of the variable displacement pump to the other port of the hydraulic motor In a transmission device, a clutch mechanism that transmits a driving force of a power source to a fluid pressure motor in a contact state and interrupts the transmission in a disconnected state, and brings the clutch mechanism into a contact state or a disconnected state by a pressure action. A clutch connecting / disconnecting mechanism, a control pump that rotates together with the variable displacement pump, and a control pump discharge pressure guided to the clutch connecting / disconnecting mechanism, A switching valve for communicating the clutch connecting / disconnecting mechanism to the tank, a communication line for communicating the forward traveling line and the reverse traveling line, a communication valve for communicating the communication line at the communication position, and disconnecting the communication line at the disconnection position And a tilt angle sensor that detects a tilt angle of the variable displacement pump. The controller switches the switching valve when the tilt angle detected by the tilt angle sensor reaches a set angle, and controls the control pump. To the clutch connection / disconnection mechanism as pilot pressure, or to connect the clutch connection / disconnection mechanism to the tank to bring the clutch mechanism into a contact state,
Further, the hydrostatic transmission device is characterized in that the communication valve is switched to the communication position almost at the same time when the clutch mechanism is brought into the contact state.