JP2566076B2 - Starting aid for tractor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tractor having a main clutch for connecting / disconnecting power transmitted to a PTO shaft and a traveling portion, and a hydraulic traveling clutch for switching forward / backward movement or high / low speed of the traveling portion. Start assist device

[0002]

2. Description of the Related Art Conventionally, in a tractor having a main clutch for connecting and disconnecting power transmitted to a PTO shaft and a traveling portion, and a hydraulic traveling clutch for switching forward and backward of the traveling portion, a main clutch is intermittently operated. Power transmission between the PTO shaft and the traveling portion is intermittently performed, and forward / backward switching and speed changeover switching of the traveling portion are performed while continuing the power transmission to the PTO shaft by the intermittent operation of the hydraulic traveling clutch. In a tractor that employs a clutch of such a system, when performing loader work or rotary work in which forward / reverse switching is frequently performed, the forward / reverse switching operation can be performed without performing the intermittent operation of the main clutch. It is convenient.

Here, when the tractor employing such a clutch is started, the main clutch is kept in the power transmission state, and then the switching lever of the hydraulic valve connected to the hydraulic traveling clutch is operated to control the hydraulic pressure. The traveling clutch is started in the connected state. For this reason, if a large amount of hydraulic oil is supplied to the hydraulic traveling clutch at the same time as switching the hydraulic valve, the hydraulic traveling clutch will be suddenly connected and a large shock will occur at the time of starting. There is.

Therefore, in order to prevent the occurrence of a large shock or engine stall at the time of starting, a soft engagement valve for automatically gradually raising the pressure of the hydraulic oil supplied to the hydraulic traveling clutch is incorporated in the hydraulic circuit. Is being carried out. When setting the specifications of the soft engagement valve, consider all conditions related to the connection of the hydraulic traveling clutch such as the load condition at start, hydraulic oil viscosity, hydraulic oil temperature, engine speed at start, etc. ing.

[0005]

A soft engagement valve set to one specification may not be able to sufficiently cope with various conditions at the time of starting. For example, if the soft engagement valve specifications are set to correspond to a large starting load, the starting operation will be delayed when the starting load is small, while the soft engagement valve specifications will be set when the starting load is small. When set to correspond to, there is a risk of sudden start or engine stall when the load at start is large.

[0006]

A main clutch for connecting and disconnecting power transmitted from an engine to a PTO shaft and a traveling portion, a hydraulic traveling clutch for switching forward / backward movement or high / low speed of the traveling portion, and the main clutch. In a tractor having a clutch pedal for intermittently operating a clutch, a supply amount of the hydraulic oil is controlled between a hydraulic pump that supplies hydraulic oil to the hydraulic traveling clutch and a hydraulic valve that controls the supply of the hydraulic oil. A throttle valve is provided, the throttle valve is connected to the clutch pedal, and the throttle valve is adjusted by operating the clutch pedal in the play area of the clutch pedal.

[0007]

By operating this clutch pedal in the play area of the clutch pedal, the throttle valve is throttle-adjusted, and by the throttle adjustment of the throttle valve, hydraulic oil is supplied from the hydraulic pump to the hydraulic traveling clutch via the hydraulic valve. The amount is controlled. Therefore, even if the starting conditions are different, the throttle valve can be throttled to smoothly connect the hydraulic traveling clutch and to smoothly start the tractor.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. First, the power transmission path in the tractor will be described based on FIG. Main clutch 2 at the rear of engine 1
The main clutch 2 is connected to one end of a drive shaft 5 for transmitting the power from the engine 1 to the PTO shaft 3 and the traveling drive wheels 4 which are traveling portions. The other end is connected to the transmission of the tractor. A forward / reverse switching hydraulic clutch 6 which is a hydraulic traveling clutch, a main transmission device 7, and an auxiliary transmission device 8 are provided in the transmission, and a differential device 9 is connected to the transmission. The drive wheels 4 are connected to the differential device 9 via a final reduction gear 10. The tractor is provided with a clutch pedal 11 for intermittently operating the main clutch 2.

A rear PTO drive shaft 12 is connected to the other end of the drive shaft 5,
The PTO shaft 3 is connected to the rear PTO drive shaft 12 via a PTO transmission 13.

Next, a hydraulic circuit for connecting and disconnecting the forward / reverse switching hydraulic clutch 6 will be described with reference to FIG. First, the forward / reverse switching hydraulic clutch 6 is composed of a forward clutch 6a and a reverse clutch 6b. The forward / reverse switching hydraulic clutch 6 and the tank 1 that stores hydraulic oil.
4, a hydraulic pump 15 for supplying the hydraulic oil in the tank 14 to the forward / reverse switching hydraulic clutch 6,
Hydraulic valve 16 for controlling the supply state of this hydraulic oil
Are provided. The hydraulic valve 16 is provided with a switching lever 17 for switching the hydraulic valve 16 between a forward drive position (F), a reverse drive position (R) and a neutral position (N). Further, in the hydraulic circuit, the relief valve 1
8. A splash cut valve 19 is provided to intermittently supply the lubricating oil to the hydraulic clutch 6 in response to the intermittent operation of the main clutch 2 by depressing the clutch pedal 11.

The hydraulic pump 15 and the hydraulic valve 16
A rotary throttle valve 20 which is a throttle valve for controlling the supply amount of the hydraulic oil supplied to the forward / reverse switching hydraulic clutch 6 via the hydraulic valve 16 is provided between and. As shown in FIG. 3, the rotary throttle valve 20 includes a body 21, a substantially cylindrical rotatable spool 22, a crescent-shaped oil passage 23 formed on the outer peripheral portion of the spool 22,
It is composed of ports 24, 25 and 26 formed in three directions. A hydraulic oil line 27 connected to the hydraulic pump 15 is connected to the first port 24, and a hydraulic oil line 28 connected to the hydraulic valve 16 is connected to the second port 25. The drain port 29 is connected to the third port 26 and is connected to the tank 14. Further, the spool 22 and the clutch pedal 11 are connected via a wire 30,
By operating the clutch pedal 11, the spool 2
2 is rotated.

FIG. 3 shows the amount of depression of the clutch pedal 11 and the associated state of the rotary throttle valve 20 in such a configuration. First, FIG. 6 (e) shows a state in which the clutch pedal 11 is depressed to the maximum depression position (e), and the spool 22 connected via the wire 30 rotates in response to the depression operation, and the first port 24 And the third port 26 communicate with each other through the oil flow path 23. Therefore,
All of the hydraulic oil supplied by the hydraulic pump 15 is returned to the tank 14 through the drain conduit 29, and the hydraulic valve 16
And the forward / reverse switching hydraulic clutch 6 is not supplied (the forward / reverse switching hydraulic clutch 6 is OFF), and the tractor is stopped. In this state, the main clutch 2 is in the power transmission cutoff state (OFF), and the PTO shaft 3 does not rotate.

FIG. 3 (d) shows a state in which the depression amount of the clutch pedal 11 is reduced to the position (d), and the spool 22 is rotated accordingly, but the first port 24 and the third port 26 are The state of communication via the oil flow path 23 does not change. Therefore, all the hydraulic oil supplied by the hydraulic pump 15 is returned to the tank 14 through the drain conduit 29, is not supplied to the hydraulic valve 16 and the forward / reverse switching hydraulic clutch 6, and the tractor is stopped. On the other hand, the main clutch 2 is in a half-clutch state, and the PTO shaft 3 starts rotating.

FIG. 1C shows a state in which the depression amount of the clutch pedal 11 is reduced to the position of (C), and the spool 22 rotates accordingly and the first port 24 is rotated.
The second port 25 and the third port 26 are communicated with each other via the oil flow path 23. Therefore, by switching the hydraulic valve 16 to the forward position or the reverse position, the hydraulic pump 15
A part of the hydraulic oil supplied by is supplied to the forward / reverse switching hydraulic clutch 6 via the hydraulic valve 16, the forward / reverse switching hydraulic clutch 6 is in a half-clutch state, and the tractor starts traveling. Although the engagement pressure to which the forward / reverse switching hydraulic clutch 6 is connected changes depending on the load state acting on the forward / reverse switching hydraulic clutch 6, the depression amount of the clutch pedal 11 is finely adjusted to flow into the second port 25. By adjusting the amount of hydraulic oil, the tractor can be started smoothly regardless of the load state acting on the forward / reverse switching hydraulic clutch 6. On the other hand, the main clutch 2 is completely connected (ON), the clutch pedal 11 enters the play area, and the PTO shaft 3 continues to rotate.

FIG. 2B shows a state in which the amount of depression of the clutch pedal 11 is reduced to the position (B), and the spool 22 rotates accordingly and the first port 24 is rotated.
The communication between the third port 26 and the third port 26 is blocked, and only the first port 24 and the second port 25 are connected. That is, the state is the same as when the rotary throttle valve 20 is not provided, and the hydraulic pump 1
5 is supplied to the forward / reverse switching hydraulic clutch 6 via the hydraulic valve 16, the forward / reverse switching hydraulic clutch 6 is completely connected (ON), and the tractor continues traveling. To do. On the other hand, the main clutch 2 is maintained in the completely connected state, the clutch pedal 11 is maintained in the play area, and the PTO shaft 3 continues to rotate.

FIG. 1A shows a state where the clutch pedal 11 is not depressed, and the clutch pedal 11 is returned to the position (a). This state is shown in (b) of the same figure.
The state is substantially the same as that shown in FIG. 3, and all of the hydraulic oil supplied by the hydraulic pump 15 is supplied to the forward / reverse switching hydraulic clutch 6 via the hydraulic valve 16 and the forward / reverse switching hydraulic clutch 6 is completely connected. The tractor continues traveling as the state (ON) is entered. On the other hand, the main clutch 2 is maintained in the completely connected state, the clutch pedal 11 is maintained in the play area, and the PTO shaft 3 continues to rotate.

Here, the clutch pedal 11 described above is used.
Table 1 shows the relationship between the position of the rotary throttle valve 20, the state of the rotary throttle valve 20, the disengaged state of the main clutch 11 and the disengaged state of the forward / reverse switching hydraulic clutch 6, and the rotating state of the PTO shaft 3 and the traveling state of the tractor. As shown.

[0018]

[Table 1]

[0019]

As described above, according to the present invention, the throttle valve is throttle-adjusted by the operation in the play area of the clutch pedal for intermittently operating the main clutch as described above. It is possible to control the supply amount of the hydraulic oil supplied to the hydraulic traveling clutch via the hydraulic traveling clutch. Therefore, it is possible to smoothly connect the hydraulic traveling clutch under any starting condition. Along with this, it is possible to prevent sudden start and engine stall at the time of starting the tractor, and moreover, a main clutch for intermittently transmitting the power transmitted to the PTO shaft and the traveling part, and a hydraulic type for switching the traveling part between forward and backward and high / low speed. Since a throttle valve is added to the conventional tractor having a traveling clutch, and the throttle valve and the clutch pedal are connected together An effect such as can be obtained a good start assisting unit without performing major design changes to the conventional tractor.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram according to an embodiment of the present invention.

FIG. 2 is a power transmission path diagram in the tractor.

FIG. 3 is an explanatory diagram showing a depression amount of a clutch pedal and a rotation state of a rotary throttle valve.

[Explanation of symbols]

 1 Engine 2 Main Clutch 3 PTO Shaft 4 Traveling Section 6 Hydraulic Traveling Clutch 11 Clutch Pedal 15 Hydraulic Pump 16 Hydraulic Valve 20 Throttle Valve

Claims (1)

(57) [Claims] 1. A main clutch for connecting / disconnecting power transmitted from an engine to a PTO shaft and a traveling section, a hydraulic traveling clutch for switching forward / backward movement and high / low speed switching of the traveling section, and an on / off operation for the main clutch. In a tractor having a clutch pedal that operates, a throttle valve that controls the supply amount of the hydraulic oil is provided between a hydraulic pump that supplies the hydraulic oil to the hydraulic traveling clutch and a hydraulic valve that controls the supply of the hydraulic oil. A starting assistance device for a tractor, wherein the throttle valve is connected to the clutch pedal, and the throttle valve is throttle-adjusted by operating the clutch pedal in a play area of the clutch pedal.