JPH01303371A - Speed change structure for working vehicle - Google Patents

Abstract

PURPOSE:To prevent a vehicular body from generating shock by, on turning the traveling direction thereof, operating a clutch once in the cutoff direction with a timing when a speed change system is located at approximately neutral position. CONSTITUTION:When an operational piece 28 is operated to be switched from a forward position F to a backward position R, a solenoid clutch 31 is operated to be cutoff until the period elapsing a predetermined time from a timing when the operational piece 28 is located at a neutral position N. Thus, until the inertia moving speed of the vehicular body is attenuated at a suitable value, the solenoid clutch 31 is operated to be cutoff, thereby preventing a reversal power from being transmitted to a traveling system so that it is possible to prevent the vehicular body from generating shock.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a transmission structure for a working vehicle, and more specifically, the invention is constructed to transmit power to a traveling system from a continuously variable transmission capable of drive rotation in both forward and reverse directions. Regarding the transmission structure of a work vehicle.

[Conventional technology]

For example, agricultural tractors, wheel loaders, etc. are equipped with hydrostatic continuously variable transmissions. Usually, these continuously variable transmissions control the discharge amount and discharge direction of hydraulic fluid by adjusting the swash plate angle. A transmission system that transmits power from the hydraulic motor to a traveling system, comprising a variable displacement hydraulic pump configured to change the hydraulic pump, and a hydraulic motor driven by hydraulic oil supplied from the hydraulic pump. In addition, the vehicle is provided with shift operation tools for adjusting the swash plate angle of the hydraulic pump, so that the traveling speed can be adjusted steplessly from the forward range to the reverse range (references not listed).

[Problem to be solved by the invention]

However, if the continuously variable transmission is configured like this,
For example, if an operation to change the driving direction is performed within an extremely short period of time, the continuously variable transmission will start reversing before the vehicle has completely stopped, that is, while the vehicle is moving due to inertia. The power of reversing the vehicle will cause it to stop and start rapidly, causing discomfort to the driver due to shock, and may also cause an excessive load to be applied to the running system, reducing the durability of the running system, etc. There is room for improvement as it may also reduce performance.

The purpose of the present invention is to prevent shock from occurring in the vehicle body even if the operation of reversing the continuously variable transmission is performed within a relatively short period of time through rational modification, and to prevent excessive loads from being placed on the driving system, etc. The point is that a transmission structure is constructed that does not have any effect on it.

[Means to solve the problem]

A feature of the present invention is that it is equipped with a continuously variable transmission that adjusts the forward and backward speed of the vehicle body and stops it, and that a clutch is interposed between the continuously variable transmission and the running system, and that The present invention further comprises a control means for once operating the clutch in the disengaged direction at the timing when the shift operation system reaches a substantially neutral position when control is performed to reverse the gear shift operation system.
Its action and effects are as follows.

[For production]

If the above features are configured as shown in FIG. 1, for example, when an operation to reverse the traveling direction is performed, the timing when the speed change operation system consisting of a solenoid valve (22) reaches the neutral position as shown in the graph of FIG. Since the clutch (31) is operated in the disengaged direction, even if the vehicle body is moving due to inertia, the driving force in the direction to stop this movement is suppressed from being transmitted from the continuously variable transmission (8). This allows the vehicle speed to be naturally attenuated.

In other words, even if the continuously variable transmission (A) starts reversing as a result of an operation to change the driving direction within an extremely short period of time, the inertial movement speed of the vehicle body will attenuate to an appropriate value.
By operating the clutch (31) in the disengaged direction, it is possible to prevent reverse rotation power from being transmitted to the travel system.

〔Effect of the invention〕

Therefore, even if the continuously variable transmission is reversed within a relatively short period of time, by providing a clutch and a control means to cut off the driving force to the traveling system in conjunction with the speed change operation. A transmission structure has been constructed that does not cause shock to the vehicle body and does not apply an excessive load to the driving system or the like.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

As shown in FIG. 3, a front body (2) having a pair of left and right drive wheels (1) and a rear body (4) having a pair of left and right drive wheels (3) are connected to a vertical axis (Y). The front and rear body parts are connected to each other so that they can swing freely around the body 2).

(4) An excavator (7) which is supported by a pair of left and right arms (6) on the front body (2) so as to be movable up and down; , lift cylinders (8
), a tilt cylinder (9) is provided, and a rear body (4) is provided.
A wheel loader is constructed by providing a drive system for transmitting power to an engine (10), a driver's seat (11), a steering wheel (12), and front and rear wheels (1) and (3), respectively.

In this wheel loader, the three types of cylinders (5),
(8), (9) Hydraulic system for each, wheels (1),
The hydraulic system that drives (3) is constructed as shown in FIG.

In other words, this hydraulic system includes a variable displacement hydraulic pump (13), a work pump (14), and a charge pump (15) driven by the power of the engine (10). ) from the oil passage (16), (
16) to a hydraulic motor (17) for driving that switches the swash plate angle between high and low levels, and pressure oil from the work pump (14) is supplied to a control valve (18) for the steering cylinder (5); Control valve for tilt cylinder (9) (
19), lift cylinder (8).

A portion of the pressure oil from the charge pump (15) is supplied to each of the control valves (20) for the control valves (8), and a portion of the pressure oil is supplied to the servo cylinder (2) that adjusts the capacity of the variable displacement hydraulic pump (13).
The remaining part is sent to the solenoid valve (22) for 1) and for charging to the oil passages (16) for driving the vehicle. A hydraulic actuator (24) for switching the swash plate angle of the hydraulic motor (17) and a negative brake (25) interposed in the traveling system are supplied through the hydraulic motor (17).

The negative brake (25) operates to release the braking state when pressure from the charge pump (15) is applied, and is configured to always apply braking force to the drive system when the engine (10) is stopped. Furthermore, an independent conduit (27) is also formed so that braking can be performed by operating a foot pedal (26) when the vehicle is running.

In addition, in this wheel loader, the system consisting of the hydraulic pump (13) and the hydraulic morph (17) is called a continuously variable transmission (8), and a lever-type operating tool (8) is provided on the side of the steering handle (12). A control device (30) transmits a signal from a switch (29) linked to this operating tool (28) so that either forward or backward running direction can be selected by using the control device (28).
(an example of a control means), and this control device (30) controls the electromagnetic valve (22) and the electromagnetic clutch ( A system is formed to control 31).

That is, the control device (30) controls the operation tool (28) so as not to cause a shock to the vehicle body even if the operation tool (28) is operated to reverse the running direction within a relatively short period of time.
28) reaches the neutral position (N), the electromagnetic clutch (31) is operated to disengage the electromagnetic clutch (31). Specifically, as shown in Fig. 2, the operating tool (28) moves to the forward position (F) When the vehicle is switched from the reverse position (R) to the reverse position (R), the electromagnetic clutch (31) is disengaged and operated until a predetermined time (T) elapses from the timing when the operating tool (28) reaches the neutral position (N). It has become. Note that the solenoid valve (22) is switched at substantially the same timing as the operation of the operating tool (28).

Incidentally, in this hydraulic system, the pressure oil from the charge pump (15) is divided into two parts by an orifice (32) so that the operating amount of the servo cylinder (21) increases with the increase in the rotational speed of the engine (10). System oil line (33),
(33) to the solenoid valve (22), and the engine (
The servo cylinder (21) is operated to a position where the value of the differential pressure caused by changing the rotation speed (10) and the spring 34) installed in the servo cylinder (21) are balanced.

[Another example]

In addition to the embodiments described above, the present invention may be applied to, for example, agricultural tractors, and the control means may be configured as software with a microprocessor, or configured as hardware with logic gates, etc. In addition, the continuously variable transmission may be of a structure other than a hydraulic pump or sweater type, and the clutch may be of a hydraulically operated type or the like that can be operated in a half-clutch state. When an operation to reverse the running direction is performed, this half-clutch state may be appropriately used to promote the attenuation of the vehicle speed.

Incidentally, although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of the drawing]

The drawings show an embodiment of the transmission structure for a work vehicle according to the present invention,
FIG. 1 is a diagram showing a control system and a hydraulic system, FIG. 2 is a graph showing clutch operation, etc. when a forward/reverse switching operation is performed, and FIG. 3 is an overall side view of the wheel loader. (30)... Control means, (31)...
Clutch, (A)... Continuously variable transmission, (N).
...Neutral position.

Claims (1)

[Claims] A continuously variable transmission (A) that adjusts the forward and backward speed of the vehicle body and stops the vehicle is provided, and a clutch (31) is interposed between the continuously variable transmission (A) and the running system, and the vehicle body control means (30) for once operating the clutch (31) in the disengagement direction at the timing when the shift operation system reaches a substantially neutral position (N) when control is performed to reverse the running direction of the vehicle;
A transmission structure for a work vehicle that is equipped with.