Control mechanism for stepless transmission

Patent metadata

Field	Value
Publication number	US-10890252-B2
Application number	US-201916560214-A
Country	US
Kind code	B2
Filing date	Sep 4, 2019
Priority date	Aug 7, 2014
Publication date	Jan 12, 2021
Grant date	Jan 12, 2021

Abstract

A control mechanism for a hydrostatic transmission includes a piston rod, a neutral biasing spring, a piston, a cylinder case provided with a first fluid chamber and a second fluid chamber, a solenoid valve capable of selectively supplying pressurized fluid to the first fluid chamber and the second fluid chamber, a pivot shaft configured to swingably support the cylinder case, and a first relief valve configured to flow the hydraulic fluid from the first fluid chamber to the second fluid chamber when a hydraulic pressure in the first fluid chamber exceeds a set pressure, and a second relief valve configured to flow the hydraulic fluid from the second fluid chamber to the first fluid chamber when a hydraulic pressure in the second fluid chamber exceeds a set pressure.

First claim

What is claimed is:

1. A control mechanism for a stepless transmission connected to a manipulation lever in the stepless transmission and disposed outside a housing of the stepless transmission, the control mechanism for the stepless transmission comprising:
a piston rod connected to the manipulation lever;
a neutral biasing spring configured to bias the manipulation lever in a neutral direction;
a piston provided on the piston rod wherein the piston is coaxial with the piston rod;
a cylinder case provided with a cylinder configured to house the piston rod and the piston such that the piston rod and the piston are displaceable in an axial direction of the cylinder,
a first fluid chamber configured to be supplied with a hydraulic fluid for withdrawing the piston rod from the cylinder;
a second fluid chamber configured to be supplied with the hydraulic fluid for introducing the piston rod into the cylinder;
a solenoid valve capable of selectively supplying pressurized fluid to the first fluid chamber and the second fluid chamber and supported by the cylinder case;
a pivot shaft configured to swingably support the cylinder case with respect to the housing;
a first relief valve configured to flow the hydraulic fluid from the first fluid chamber to the second fluid chamber when a hydraulic pressure in the first fluid chamber exceeds a set pressure; and
a second relief valve configured to flow the hydraulic fluid from the second fluid chamber to the first fluid chamber when a hydraulic pressure in the second fluid chamber exceeds a set pressure.

2. The control mechanism for the stepless transmission according to claim 1 , wherein
the piston rod includes a first rod portion protruding into the first fluid chamber and a second rod portion protruding into the second fluid chamber,
wherein an axial diameter of the second rod portion of the piston rod is larger than an axial diameter of the first rod portion, and a stepped portion is formed at a boundary between the first rod portion and the second rod portion,
wherein a first threaded portion is formed at least at a tip portion of the first rod portion,
wherein the neutral biasing spring is supported by a shaft and a pair of spring retainers configured to be slidable on the shaft,
wherein the neutral biasing spring is supported on the shaft between the pair of spring retainers,
wherein a second threaded portion is formed at one end of the shaft that protrudes into the first fluid chamber,
wherein the first rod portion with the first threaded portion is inserted into a shaft hole of the piston and the first threaded portion is screwed into a nut,
wherein the first threaded portion and the second threaded portion are fixed together by a nut, and
wherein the piston is sandwiched by the stepped portion and the nut with respect to the piston rod.

3. The control mechanism for the stepless transmission according to claim 1 , wherein
the piston is provided with a first fluid passage and a second fluid passage in fluid communication with the first fluid chamber and the second fluid chamber,
the piston is configured to be dividable into two portions in an axial center direction of the shaft hole,
the first fluid passage of the piston is provided with a first seat surface, a first ball in contact with the first seat surface, and a first spring configured to press the first ball to the first seat surface with a predetermined biasing force are arranged, and
the second fluid passage of the piston is provided with a second seat surface, a second ball in contact with the second seat surface, and a second spring configured to press the second ball to the second seat surface with a predetermined biasing force are arranged.

4. The control mechanism for the stepless transmission according to claim 1 , wherein
the piston is provided with a first fluid passage and a second fluid passage in fluid communication with the first fluid chamber and the second fluid chamber,
the first fluid passage is provided with a first seat surface, a first ball in contact with the first seat surface, and a first spring configured to press the first ball to the first seat surface with a predetermined biasing force are arranged, and
the second fluid passage is provided with a second seat surface, a second ball in contact with the second seat surface, and a second spring configured to press the second ball to the second seat surface with a predetermined biasing force are arranged.

5. The control mechanism for the stepless transmission according to claim 1 , further comprising:
a case configured to accommodate the neutral biasing spring, comprising:
a cylindrical member accommodating the neutral biasing spring; and
a plate closing one end of the cylindrical member,
wherein the plate is fixed to the cylinder case by a plurality of bolts, and
wherein the cylindrical member is sandwiched by the cylinder case and the plate.

Assignees

• Kanzaki Kokyukoki Mfg Co Ltd

Inventors

• Matsuura Jun
• Kamikawa Nobuhisa

Classifications

• F16H61/4069 Primary

  Valves related to the control of neutral, e.g. shut off valves · CPC title

• F16H61/431 Primary

  Pump capacity control by electro-hydraulic control means, e.g. using solenoid valves · CPC title

• F04B23/106

  being an axial piston pump · CPC title

• F04B1/20

  having rotary cylinder block · CPC title

• F04B1/00

  Multi-cylinder machines or pumps characterised by number or arrangement of cylinders (machines or pumps with pistons coacting within one cylinder F04B3/00) · CPC title