JPH01303374A - Working vehicle - Google Patents

Abstract

PURPOSE:To prevent a vehicular body from generating shock by, on reversely operating the traveling direction, maintaining a continuously variable transmission in the travel stopping state by a predetermined time from a timing when an operating piece is reached at a neutral position. CONSTITUTION:When an operating piece 28 is switched from a forward position F to a backward position R, during a predetermined time T from a timing when the operating piece 28 is reached at a neutral position N, the output of a control signal to a solenoid valve from a controller 30 is stopped, so as to maintain a continuously variable transmission A in the travel stopping state. Thus, after the inertia moving speed for a vehicular body is naturally attenuated, an oil pressure pump 13 is controlled in the backward direction, thereby prevent the vehicular body from generating shock.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a working vehicle, and more particularly to a working vehicle having a continuously variable transmission configured to move the vehicle forward and backward by driving in both forward and reverse directions.

[Conventional technology]

For example, in agricultural tractors, wheel loaders, etc., some of these travel drive systems are equipped with hydrostatic continuously variable transmissions, and normally these continuously variable transmissions are operated by adjusting the swash plate angle. It consists of a variable displacement hydraulic pump that can change the oil discharge direction and the oil discharge direction, and a hydraulic motor that is driven by hydraulic oil supplied from this hydraulic pump (references not listed). .

[Problem to be solved by the invention]

However, if the continuously variable transmission is configured as described above, for example, if an operation to change the direction of travel is performed within an extremely short period of time, the continuously variable transmission will reverse the direction before the vehicle has finished stopping. This not only causes discomfort to the driver due to shock, but also causes an excessive load to be applied to the travel drive system, which may reduce the durability of the travel drive system.

The purpose of the present invention is to prevent shock from occurring in the vehicle body even when the continuously variable transmission is reversed in a relatively short period of time through reasonable modification, and to prevent excessive loads from being placed on the drive system. The point is that the work vehicle is constructed without causing any

[Means to solve the problem]

A feature of the present invention is that the operating tool is configured to stop the vehicle from moving by setting the operating tool to the neutral position, and to switch the running direction of the vehicle to either front or rear by setting the operating tool to a predetermined position away from the neutral position. and the continuously variable transmission are linked together, and when an operation is performed to reverse the traveling direction using the operating tool, a predetermined period of time starts from the timing when the operating tool reaches a substantially neutral position, regardless of the operating position of the operating tool. However, the control means for maintaining the continuously variable transmission in a stopped state is provided, and its functions and effects are as follows.

[For production]

If the above characteristics are configured as shown in FIG. 1, for example, when an operation to reverse the running direction is performed using the operating tool (28), the control means (30) is a continuously variable transmission (A
) is held in the neutral position for a predetermined time (T), and then the servo cylinder (21)
) to a position corresponding to the operating position of the operating tool (28).

In other words, even if an operation to reverse the continuously variable transmission (A) is performed rapidly, the continuously variable transmission (A) will always be set to a drive stop state for a predetermined period of time (T) regardless of this operation. Therefore, it is possible to suppress a phenomenon in which a driving force acting in a direction opposite to the direction of movement of the vehicle body is applied to the traveling drive system while the vehicle body is moving due to inertia.

Furthermore, when this operation is expressed in a graph, as shown in Fig. 2,
When the operating tool (28) is switched from the forward position (F) to the reverse position (R), until time (T) has elapsed after the operating tool (28) reached the neutral position (N), Acceleration in the reverse direction is not reflected on the vehicle body.

〔Effect of the invention〕

Therefore, by modifying the connection between the operating tool and the continuously variable transmission by interposing a control means, even if the operation of reversing the continuously variable transmission is performed within a relatively short period of time, shocks may not be generated in the vehicle body. Moreover, a work vehicle has been constructed that does not impose an excessive load on the travel drive system.

〔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 longitudinal axis (Y). ), the front and rear car bodies (2) are connected so that they can swing freely.

(4) A shovel (7) is provided with a steering cylinder (5) therebetween to form a running vehicle body, and is supported by a pair of left and right arms (6) on the front vehicle body (2) so as to be able to rise and fall freely; , the lift cylinder that drives these (
8), a tilt cylinder (9) is provided, and a rear body (4) is installed.
) is provided with a drive system that transmits power to an engine (10), a driver's seat (11), a steering wheel (12), and front and rear wheels (1) and (3), respectively, to constitute a wheel loader.

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

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). Pressure oil from the oil passage (16),
(16) is supplied to a hydraulic motor (17) for driving which switches the swash plate angle to two high and low steps, and a working pump (14).
Pressure oil is supplied to the control valve (18) for the steering cylinder (5), the control valve (19) for the tilt cylinder (9), and the 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 (20) and 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 traveling drive, and the remaining part is sent to the switching valve (23). It is supplied to a hydraulic actuator (24) that switches the swash plate angle of the hydraulic motor (17) and a negative brake (25) installed in the traveling system.

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 rotor, the system consisting of the hydraulic pump (13) and the hydraulic motor (17) is connected to a continuously variable transmission (A>
This operating tool (28) is called a lever type operating tool (28) provided on the side of the steering handle (12) so that one of the driving directions, forward or backward, can be selected.
A signal from a switch (29) associated with the solenoid valve (22) is input to a control device (30) (an example of a control means) that controls the solenoid valve (22), and furthermore, this operating tool (28) is operated for a relatively short period of time. It is designed so that no shock is generated to the vehicle body even if the vehicle is switched to reverse the direction of travel.

That is, the control device (30) is equipped with a timer (not shown), and when the engine speed is maintained constant, for example, the operating tool (28) is moved to the forward position (F) as shown in FIG.
) to the reverse position (R), the operating tool (
28) reaches the neutral position (N) until the timer finishes counting the predetermined time (T), the control device (30) does not output a control signal to the solenoid valve (22) and the vehicle body After the inertial movement speed of the vehicle is naturally attenuated, the hydraulic pump (13) is controlled in the reverse direction.

Note that the operating amount of the servo cylinder (21) is equal to the engine (lO
The pressure oil from the charge pump (15) is divided by an orifice (31) through two oil lines (32), (32) so that the pressure increases as the rotation speed of the solenoid valve ( ) increases. 22) to operate the servo cylinder (21) to a position where the value of the differential pressure caused by changing the rotation speed of the engine (10) and the spring (33) built into the servo cylinder (21) are balanced. It has become.

[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. The continuously variable transmission can be implemented in various ways, and the continuously variable transmission may have a structure other than a hydraulic pump or motor type.Furthermore, the operating tool increases forward speed by operating in a predetermined direction, and reverses by sandwiching the neutral position. It may be configured such that reverse speed is increased by operating in the direction.

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 work vehicle according to the present invention, and FIG. 1 is a diagram showing the control system and hydraulic system, and FIG. 2 is a graph showing the vehicle speed etc. when the forward/reverse switching operation is performed. FIG. 3 is an overall side view of the wheel loader. (28)... Operating tool, (30)... Control means, (A)... Continuously variable transmission, (N)...
...Neutral position, (T) ...Predetermined time.

Claims (1)

[Claims] By setting the operating tool (28) to the neutral position (N), the vehicle body stops running, and by setting it to a predetermined position away from the neutral position (N), the running direction can be switched to either front or rear. , when the operating tool (28) and the continuously variable transmission (A) are linked and the operating tool (28) is used to reverse the running direction, regardless of the operating position of the operating tool (28), First, a predetermined period of time (
A working vehicle is provided with a control means (30) for maintaining a continuously variable transmission (A) in a stopped state by an amount equal to T).