JPH0483972A - Shift control structure for working vehicle - Google Patents

Abstract

PURPOSE:To simplify structure of an oil pressure circuit, to reduce a cost, and to facilitate a shift by interlinking high and low switching mechanisms, respectively disposed to two hydraulic motors, and a single running speed switching tool. CONSTITUTION:Hydraulic motors M1 and M2 on both sides form a capacity variable type motor capable of producing a rotation state for two speeds of high and low speeds, and operation shafts 25 and 26 serving as a high and low switching mechanism are linked to the wash plates of the hydraulic motors M1 and M2. A piston 29a of a hydraulic cylinder 29 is linked as a running speed switching tool, having an operation part, to a pedal 30 for shift control, and the pedal 30 for shift control is energized to the low speed operation position side through the piston 29a through the force of a spring 31. The hydraulic motors M1 and M2 are both run normally in a low speed state, and when the pedal 30 for shift control is pedalled to the high speed operation side, the hydraulic motors M1 and M2 are both switched to a high speed state and run.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a pair of hydraulic motors for separately driving a pair of left and right traveling devices, for example, in an operator of a backhoe, etc., and also provides two high and low traveling speeds. This invention relates to a gear shifting operation structure for a work vehicle that shifts gears.

[Conventional technology]

Conventionally, as shown in Fig. 5, the speed change operation structure of this type of work vehicle consists of a pair of left and right hydraulic motors (M1), (M
2) is driven by a pair of hydraulic pumps (P+) (P2) separately at low speed (Fig. 5 (a)), and the pressure from the hydraulic pumps (P1) and (P2) connected in parallel. Hydraulic motor (Ml) connected in series with oil.

It is known to use an oil passage switching valve or the like to switch the hydraulic circuit (FIG. 5(b)) for supplying oil to (M2) and driving at high speed.

[Invention or problem to be solved]

However, the conventional structure described above has a hydraulic motor (M
1), (M2), hydraulic motor (
M1), (L), hydraulic pumps (P1), (P2) must be provided with hydraulic piping, oil passage switching valves, etc. so that the series-parallel connection state of the hydraulic circuits as described above can be switched. However, there were drawbacks such as a complicated circuit structure and relatively high manufacturing costs.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a shift operation structure for a work vehicle that can easily change the running speed into two stages, high and low, without constructing a complicated hydraulic circuit. shall be.

[Means to solve the problem]

In order to achieve the above object, the speed change operation structure for a work vehicle according to the present invention has a pair of hydraulic motors that separately drive a pair of left and right traveling devices, and each of these hydraulic motors is switched to two high and low drive states. The present invention is characterized in that the vehicle is provided with a high/low speed switching mechanism capable of switching between high and low speeds, and in order to simultaneously operate both switching mechanisms, both switching mechanisms are linked to a single running speed switching device.

The functions and effects of this characteristic configuration are as follows.

[For production]

That is, in order to simultaneously switch a pair of hydraulic motors to a high-speed or low-speed driving state, the height switching mechanism provided for both hydraulic motors and a single running speed switching device are linked.
When the travel speed switching tool is operated to switch to the high speed or low speed side, both hydraulic motors are simultaneously switched to the high speed or low speed driving state in conjunction with the operation.

〔Effect of the invention〕

Therefore, since the connection state of the circuit between the hydraulic motor and the hydraulic pump can remain constant, the structure of the hydraulic circuit etc. can be made simple and inexpensive, and the traveling speed can be changed by simply operating the traveling speed switching device. Since this is fine, I was able to easily shift gears.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a backhoe as an example of a work vehicle. This backhoe has a pair of left and right crawler running devices (
1), A swivel base (3) is mounted on the traveling machine base (2) equipped with (1) so as to be able to rotate freely around the vertical axis (Y), and an excavation work device is mounted on the swivel base (3). (4), Operation Department (
5) and a driving unit (6).

The hydraulic circuit of this backhoe is shown in FIG.

An engine (not shown) includes first and second pumps (PI),
(P2), the discharge pressure oil of the first pump (Pl),
The control valve (8) of the packet cylinder (7), the control valve (10) of the boom cylinder (9), and the control valve (11) of the right travel hydraulic motor (M2) can be passed in this order. 2 pump (P2) discharge pressure oil, left travel hydraulic motor (M,) control valve (12), boom cylinder (9)
merging control valve (13), control valve (15) of the arm cylinder (14), and control valve (17) of the service port (16).
) can be passed in this order. In addition, each control valve (
8), (10), (12), (13), (15
).

The valve unit (U), which is integrally connected with the valve unit (17), is attached to the swivel base (3) using the flanges (
18), (18) and the valve mounting base of the swivel base (3) (
19) by fastening them with bolts (20) and nuts (21). The bolts (20) and nuts (21) are fastened to the valve mounting base (19) and the flange (18).
(18) and the flange (18), (18)
Anti-vibration rubbers (23) and (24) are interposed between the bolt (20) and the washer (22) of the head of the bolt (20).

Next, the hydraulic motors (Ml) and (M2) will be explained.

The left and right hydraulic motors (Ml) and (M2) are both variable displacement motors that can achieve two high and low speed rotational states by adjusting the swash plate angle in two stages.
The operating shafts (25) and (26) as a height switching mechanism for switching and adjusting the swash plate angle are connected to hydraulic motors (M1) and (
It is linked to the swash plate of M2). These operating axes (25),
(26) is connected to the piston (27a) of the single-acting switch cylinder (27) so as to be able to switch between high and low speeds while both are linked to high-speed drive or low-speed drive. They are linked via link mechanisms, etc.

The pressure chamber (27A) of this switch cylinder (27) is
As shown in FIG. 1, it is connected to a pressure chamber (29A) of a hydraulic cylinder (29) for speed change operation via an oil passage (28) so that hydraulic oil can be supplied and discharged therefrom. Then, the piston (29a) of the hydraulic cylinder (29) is connected to a speed change operation pedal (30) as a traveling speed switching device provided in the driving section (5).
), and the spring (3 parts) is connected to the piston (
29a), the gear shift operation pedal (30) is biased toward the low speed operation position.

Therefore, with the above configuration, the hydraulic motor (M,).

(M2) are normally driven together at low speeds, and when the gear shift operation pedal (30) is depressed instead of high speed operation, the piston (29a) is pushed in and hydraulic oil is supplied to the switch cylinder (27). switch cylinder (
The piston (29a) of 27) moves in a certain direction, and along with this, the hydraulic motor (M,).

(M2) are both switched to high speed state and driven.

When the depressing operation of the shift operation pedal (30) is released, the piston (29a) and the shift operation pedal (30) are returned to the low speed operation position by the spring (31), and the piston (27) of the switch cylinder (27) is returned to the low speed operation position. 27
a) also returns to its normal position, and the hydraulic motors (Ml) and (M
2) are both driven at low speed.

[Another example]

The present invention may be implemented as follows.

■ The linkage mechanism between the travel speed switching device and the switching mechanism for both hydraulic motors should be configured mechanically using lofts, links, etc.

■ Applicable to various work vehicles other than backhoes.

■ Use a different type of hydraulic motor in addition to the swash plate type plunger motor as the hydraulic motors (M, ), (M2).

It should be noted that the present invention is not limited to the structure shown in the accompanying drawings by adding reference numerals in the claims for convenient comparison with the drawings.

[Brief explanation of drawings]

In the drawings, FIGS. 1 to 4 show an embodiment of a speed change operation structure for a working vehicle according to the present invention, FIG. 1 is an explanatory diagram showing a hydraulic circuit and a speed change operation structure in a backhoe, and FIG. 2 shows a backhoe. FIG. 3 is a plan view showing the valve unit, and FIG. 4 is a longitudinal sectional side view showing the structure of the valve unit. In the drawings, FIG. 5 shows a conventional example;
Figure (a) is a circuit diagram showing the hydraulic circuit of the hydraulic motor when the traveling device is driven at low speed, and Figure 5 (0) is a circuit diagram showing the hydraulic circuit of the hydraulic motor when driving the traveling device at high speed. It is a diagram. (1)... Traveling device, (25), (26).
...High/low speed switching mechanism, (30)...Traveling speed switching device, (M1), (M2)...Hydraulic motor. l2WI

Claims (1)

[Claims] A pair of hydraulic motors (M_1) and (M_2) that separately drive the pair of left and right traveling devices (1) and (1) are respectively driven in two high and low stages. A high/low speed switching mechanism (25) that can be switched (
26), and in order to operate both the switching mechanisms (25) and (26) simultaneously, the switching mechanisms (25) and (26) are provided.
A speed change operation structure for a work vehicle, characterized in that a single running speed switching tool (30) is linked to the drive speed switching tool (30).