JPH05223169A - Transmission mechanism for hydraulic continuously variable-transmission - Google Patents

Abstract

PURPOSE:To lessen impact due to sudden start and sudden stop, by changing the damping force coefficient of a fluid damper for controlling a gear shift lever in response to changes of operation oil pressure of a hydraulic continuously variable transmission and attenuating acceleration change of a running vehicle in a running vehicle with a hydraulic continuously variable transmission used as a shaft drive device. CONSTITUTION:In a gear shifting operation system of a hydraulic continuously variable transmission, a fluid damper D intervenes into a gear change system, a pilot differential pressure sensing type variable orifice valve A intervenes into a channel of fluid damper D, work oil for the hydraulic continuously variable transmission is introduced into pilot chambers a, b of the pilot differential pressure sensing type variable orifice valve A, and the diameter of the throttle is so constituted to become smaller, as the differential pressure between the pilot chamber a, b becomes larger.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation mechanism of a gear shift operation lever in a hydraulic continuously variable transmission used as an axle drive device of a traveling vehicle.

[0002]

2. Description of the Related Art Conventionally, a technique in which a fluid damper is interposed in a shift operation system of a hydraulic continuously variable transmission has been known. For example, it is like the technique described in JP-A-61-27730.

[0003]

However, in the above-mentioned prior art, it is known that the fluid damper is interposed in the gear shift operation system of the hydraulic continuously variable transmission, but the damping force constant of the fluid damper is known. Was always constant and could not be dampened to changes in vehicle acceleration.

[0004]

The problems to be solved by the present invention are as described above, and the means for solving the problems will be described below. That is, in a configuration in which a fluid damper is interposed in a gear shift operation system of a hydraulic type continuously variable transmission, a pilot differential pressure sensing type variable orifice valve is provided in a flow path of the fluid damper, and the pilot differential pressure sensing type variable valve is installed. The hydraulic fluid of the hydraulic continuously variable transmission is introduced into the pilot chambers a and b of the orifice valve, and the throttle hole diameter is reduced as the hydraulic pressure difference between the pilot chambers a and b increases.

[0005]

[Operation] Next, the operation will be described. That is, in a traveling vehicle in which the hydraulic continuously variable transmission is used as the axle drive device, the damping force constant of the fluid damper changes in accordance with the change in the operating oil pressure of the hydraulic continuously variable transmission, and the acceleration change damping of the traveling vehicle is attenuated. , The impact of sudden start or sudden stop will be softened.

[0006]

EXAMPLES Next, examples will be described. FIG. 1 is a hydraulic circuit diagram of an embodiment in which two pilot differential pressure sensing type variable orifice valves A are arranged in a shift operation mechanism of a hydraulic continuously variable transmission, and FIG. 2 is a hydraulic continuously variable transmission of the present invention. In the speed change operation mechanism of the shuttle valve 1, a shuttle valve
4 is a hydraulic circuit diagram of a configuration in which only one pilot differential pressure sensing type variable orifice valve A is arranged, FIG. 3 is a drawing showing an operating mode of the pilot differential pressure sensing type variable orifice valve, and FIG. FIG. 3 is a schematic view of a gear shift operation mechanism of a continuously variable transmission.

This will be described with reference to FIG. The traveling vehicle is equipped with a hydraulic continuously variable transmission, and an engine E of the traveling vehicle drives a hydraulic pump P having a movable swash plate 6. The hydraulic pump P can reverse the discharge direction of the pressure oil by changing the angle of the movable swash plate 6, and the rotation of the hydraulic motor M can be forward rotation and reverse rotation, and a neutral state in a non-rotation state between them. It is possible to shift to the state. The forward rotation and the reverse rotation enable stepless speed change by changing the rotation angle of the movable swash plate 6.

The hydraulic pump P and the hydraulic motor M are connected by a pair of oil passages 4 and 5 forming a closed circuit. When one of the oil passages 4 and 5 has a high pressure, the other has a low pressure, and which one has a high pressure is determined by the rotating direction of the movable swash plate 6. The pressure oil is supplied from the charge pump CP via the charge check valves 11 and 12 between 4 and 5.

The hydraulic oil replenishment check valves 11 and 12 open the low-pressure side charge check valves 11 and 12 when the hydraulic oil in the closed circuit decreases and a negative pressure is generated inside.
The hydraulic oil is replenished from the open charge check valves 11 and 12. The charge pump CP is driven by the engine E by the same shaft as that of the hydraulic pump P, and when there is no need to replenish the operating oil to the closed circuit, the pressure oil from the charge pump CP is supplied by the charge relief valve 13. , Is ejected into the mission case, which is a hydraulic oil tank.

In the above configuration, the operator who gets on the traveling vehicle rotates the movable swash plate 6 by rotating the speed change lever 1 back and forth to change the discharge direction and discharge amount of the pressure oil, The rotation direction and the rotation speed of the hydraulic motor M are operated. However, when the movable swash plate 6 is greatly tilted at a stroke by the rotation operation of the speed change lever 1, the amount and direction of the pressure oil discharged from the hydraulic pump P change at once, and the rotation speed and rotation direction of the hydraulic motor M are changed. Is changed all at once. In this way, if the rotational speed of the hydraulic motor M is changed at once, the acceleration for acceleration and the acceleration for deceleration change at once, and the operator feels a sudden start or sudden stop of the machine. .

In order to avoid a sudden change in acceleration such as a sudden start or a sudden stop as described above, a fluid damper D for regulating the rotational speed of the speed change lever 1 is provided. The fluid damper D is composed of a piston 3 and a cylinder 2 into a reciprocating cylinder, and the inside thereof is filled with oil. In FIG. 1, when the piston 3 slides left and right inside the cylinder 2, the piston 3 completely divides the cylinder 2 into two chambers.
The oil in the oil chamber e or the oil chamber f is movable via the flow path C.

In the present invention, the pilot differential pressure sensing type variable orifice valve A is arranged in the flow path C. The pilot differential pressure sensing type variable orifice valve A guides the pressure oil from the closed circuits 4 and 5 to the pilot chambers a and b.

The pressure oil introduced into the pilot chambers a and b of the pilot differential pressure sensing type variable orifice valve A and the opening of the orifice valve are constructed as shown in FIG. That is, the pressure oil in the oil passages 4 and 5 is directly introduced into the pilot chamber a, but the pressure oil is introduced into the pilot chamber b through the throttle m, so that only the portion corresponding to this throttle m. The difference between the pressures in the pilot chambers a and b causes the orifice valve to open and close.

That is, the oil pressure Pb of the pilot chamber b introduced through the throttle m is a steady pressure which is uniformized by the throttle m, and is not so affected by the acceleration change. On the other hand, the oil passage 4 does not pass through the throttle m.
・ Hydraulic pressure Pa introduced directly into the pilot chamber a from 5
Accepts the fluctuating pressure as it is, and the magnitude of the fluctuating pressure is input as it is. The pilot differential pressure sensing type variable orifice valve A senses the difference between the fluctuating pressure input to the pilot chamber a and the steady pressure input to the pilot chamber b.

As a result, as shown in FIG. 3, when the fluctuation pressure is larger than the steady pressure, "Pa>Pb", the throttle hole diameter of the pilot differential pressure sensing type variable orifice valve A is also reduced to a small diameter. When the fluctuating pressure is equal to the steady pressure "Pa = Pb"
In, the aperture diameter is reduced to a medium diameter. When the fluctuating pressure is smaller than the steady pressure, the diameter of the throttle hole is set to a large diameter in the case of "Pa <Pb". That is, depending on the magnitude of the fluctuating pressure and the steady pressure,
By changing the throttle hole diameter of the pilot differential pressure sensing type variable orifice valve A, resistance is given to the passage of oil in the flow path C and the resistance force given to the speed change lever 1 is changed.

In the embodiment of FIG. 1, in the oil passages 4 and 5, either one of the pilot differential pressure sensing type variable orifice valves A is operated by the high pressure side pressure, and the other orifice valve is operated by the low pressure side pressure. A does not work. Oil passage 4.5
Since it is necessary to operate the pilot differential pressure sensing type variable orifice valve A by the pressure oil on either side of the high pressure side, two pilot differential pressure sensing type variable orifice valves A are arranged.

As shown in the embodiment of FIG. 2, the shuttle valve 1 having a structure in which the ball valve 9 closes the circuit on the low pressure side.
When 4 is provided between the oil passages 4 and 5, the shuttle valve 14 is configured to constantly guide the high pressure side pressure oil to the pilot differential pressure sensing type variable orifice valve A.
With only one pilot differential pressure sensing type variable orifice valve A,
It can be configured.

[0018]

Since the present invention is configured as described above, it has the following effects. That is, in a traveling vehicle using a hydraulic continuously variable transmission as an axle drive device, the throttle hole diameter of the pilot differential pressure sensing type variable orifice valve is changed by the hydraulic pressure difference of the high pressure side oil passage of the hydraulic continuously variable transmission. As a result, the damping force constant of the fluid damper D can be changed. Therefore, it becomes possible to damp the acceleration change of the traveling vehicle and soften the shock such as sudden start or sudden stop.

[Brief description of drawings]

FIG. 1 shows a shift operation mechanism of a hydraulic continuously variable transmission,
FIG. 3 is a hydraulic circuit diagram of an embodiment in which two pilot differential pressure sensing type variable orifice valves A are arranged.

FIG. 2 is a diagram showing a shift operation mechanism of a hydraulic continuously variable transmission according to the present invention, in which a shuttle valve 14 is interposed between a closed high-pressure circuit composed of a hydraulic pump P and a hydraulic motor M, and a low-pressure circuit; FIG. 3 is a hydraulic circuit diagram of a configuration in which one pilot differential pressure sensing type variable orifice valve A is arranged.

FIG. 3 is a view showing an operation mode of a pilot differential pressure sensing type variable orifice valve.

FIG. 4 is a schematic view of a shift operation mechanism of a hydraulic continuously variable transmission.

[Explanation of symbols]

 A Pilot differential pressure sensing type variable orifice valve C Flow path D Fluid damper a / b Pilot chamber 1 Shift lever 2 Fluid damper D cylinder 3 Fluid damper D piston 4.5 Oil passage 6 Movable swash plate 14 Shuttle valve

Claims (1)

[Claims] 1. A hydraulic differential continuously variable transmission having a structure in which a fluid damper is interposed in a speed change operation system, wherein a pilot differential pressure sensing type variable orifice valve is provided in a flow path of the fluid damper, and the pilot differential pressure is provided. The hydraulic fluid of the hydraulic continuously variable transmission is introduced into the pilot chambers a and b of the sensing type variable orifice valve, and the throttle hole diameter is reduced as the hydraulic pressure difference between the pilot chambers a and b increases. A gear shifting operation mechanism of a hydraulic continuously variable transmission characterized by: