Micro-traction drive unit, hydraulic transmission and hydraulic device

Patent metadata

Field	Value
Publication number	US-10408319-B2
Application number	US-201615274995-A
Country	US
Kind code	B2
Filing date	Sep 23, 2016
Priority date	Dec 1, 2015
Publication date	Sep 10, 2019
Grant date	Sep 10, 2019

Abstract

A MTD unit according to a present disclosure includes a bearing member that has an inner ring, a plurality of rolling elements and an outer ring and is capable of bearing a radial load and a unidirectional axial load, a retainer that has a retaining part retaining the rolling elements such that the rolling elements are rotatable around their own axes and rotates around an axis of the inner ring in accordance with an orbital motion of the rolling elements around the inner ring, and a case that accommodates the bearing member and the retainer, wherein the case has a piston that is axially movable so as to push a movable body, which is either the inner ring or the outer ring, in a first axial direction, an oil chamber provided on an opposite side of the piston from the movable body, and an oil passage for guiding pressurized oil to the oil chamber.

First claim

The invention claimed is:

1. A hydrostatic transmission, comprising:
a pump shaft operatively connected to a driving source;
a motor shaft acting as an output shaft;
a hydraulic pump and a hydraulic motor that are supported by the pump shaft and the motor shaft, respectively, and are fluidly connected to each other;
a case wherein the hydraulic pump and the hydraulic motor are disposed therein, and a volume varying member varying a volume of at least one of the hydraulic pump and the hydraulic motor; and
a bearing member that has an inner ring, a plurality of rolling elements, and an outer ring and is capable of bearing a radial load and a unidirectional axial load, and a retainer that has a retaining part retaining the rolling elements such that the rolling elements are rotatable around their own axes and rotates around an axis of the inner ring in accordance with an orbital motion of the rolling elements around the inner ring,
wherein the bearing member is disposed in the case such that, with the inner ring being connected to one of the pump shaft and the motor shaft so as to be relatively non-rotatable and the outer ring being radially immovable, one of the inner ring and the outer ring is a movable body that is movable in a first axial direction to exert a radial load on the rolling elements, and the other is a fixed body that is immovable in the first axial direction,
wherein the case has a piston that is axially movable so as to be capable of pushing the movable body in the first axial direction, an oil chamber provided on an opposite side of the piston from the movable body, and an oil passage that forms at least a part of a preload line for supplying some of pressurized oil present in the hydrostatic transmission to the oil chamber,
wherein the hydraulic pump and the hydraulic motor are fluidly connected to each other by a pair of first and second hydraulic oil lines so as to form a closed circuit,
wherein the volume varying member is configured to be capable of reaching a normal-rotation operating state in which supply and discharge directions of the hydraulic pump are determined such that the first and second hydraulic oil lines have a high pressure and a low pressure, respectively, so as to cause the hydraulic motor to perform normal rotation, and a reverse-rotation operating state in which supply and discharge directions of the hydraulic pump are determined such that the first and second hydraulic oil lines have a low pressure and a high pressure, respectively, so as to cause the hydraulic motor to perform reverse rotation,
wherein the preload line includes first and second preload lines fluidly connected to the first and second hydraulic oil lines, respectively, an oil-chamber-side preload line fluidly connected to the oil chamber, and a switching valve interposed between the oil-chamber-side preload line and the first and second preload lines, and
wherein the switching valve is capable of reaching a normal-rotation position where the first preload line is connected to the oil-chamber-side preload line and the second preload line is disconnected from the oil-chamber-side preload line, and a reverse-rotation position where the first preload line is disconnected from the oil-chamber-side preload line and the second preload line is connected to the oil-chamber-side pre-load line, and
the switching valve reaches the normal-rotation position and the reverse-rotation position when the volume varying member is in the normal-rotation operating state and the reverse-rotation operating state, respectively.

2. The hydrostatic transmission according to claim 1 , wherein the switching valve is capable of reaching, in addition to the normal-rotation position and the reverse-rotation position, a neutral position where the first and second preload lines are both disconnected from the oil-chamber-side preload line, and the switching valve reaches the neutral position when the volume varying member is in a neutral state between the normal-rotation operating state and the reverse-rotation operating state.

3. The hydrostatic transmission according to claim 1 , wherein an auxiliary spring that biases the piston in the first axial direction is provided in the oil chamber.

4. A hydrostatic transmission comprising:
a pump shaft operatively connected to a driving source;
a motor shaft acting as an output shaft;
a hydraulic pump and a hydraulic motor that are supported by the pump shaft and the motor shaft, respectively, and are fluidly connected to each other;
a case wherein the hydraulic pump and the hydraulic motor are disposed therein, and a volume varying member varying a volume of at least one of the hydraulic pump and the hydraulic motor; and
a bearing member that has an inner ring, a plurality of rolling elements, and an outer ring and is capable of bearing a radial load and a unidirectional axial load, and a retainer that has a retaining part retaining the rolling elements such that the rolling elements are rotatable around their own axes and rotates around an axis of the inner ring in accordance with an orbital motion of the rolling elements around the inner ring,
wherein the bearing member is disposed in the case such that, with the inner ring being connected to one of the pump shaft and the motor shaft so as to be relatively non-rotatable and the outer ring being radially immovable, one of the inner ring and the outer ring is a movable body that is movable in a first axial direction to exert a radial load on the rolling elements, and the other is a fixed body that is immovable in the first axial direction,
wherein the case has a piston that is axially movable so as to be capable of pushing the movable body in the first axial direction, an oil chamber provided on an opposite side of the piston from the movable body, and an oil passage that forms at least a part of a preload line for supplying some of pressurized oil present in the hydrostatic transmission to the oil chamber,
wherein the hydraulic pump and the hydraulic motor are fluidly connected to each other by a pair of first and second hydraulic oil lines so as to form a closed circuit,
wherein the volume varying member is configured to be capable of reaching a normal-rotation operating state in which supply and discharge directions of the hydraulic pump are determined such that the first hydraulic oil line has a high pressure so as to cause the hydraulic motor to perform normal rotation, and a neutral state in which supply and discharge of the hydraulic pump are suspended,
wherein the preload line has one end that is fluidly connected to the first hydraulic oil line and the other end that is fluidly connected to the oil chamber,
wherein a switching valve is disposed in the preload line, and
wherein the switching valve is capable of reaching a normal-rotation position where the preload line is in a communicating state, and a neutral position where the preload line is in an interrupted state, and the switching valve reaches the normal-rotation position and the neutral position when the volume varying member is in a normal-rotation operating state and a neutral state, respectively.

5. The hydrostatic transmission according to claim 4 , wherein an auxiliary spring that biases the piston in the first axial direction is provided in the oil chamber.

Assignees

• Kanzaki Kokyukoki Mfg Co Ltd

Inventors

• Sugimoto Hiroshi
• Imanaka Hajimu
• Hashima Hiroaki

Classifications

• F16H61/431

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

• F16H13/08

  with balls or with rollers acting in a similar manner · CPC title

• F16H13/10

  Means for influencing the pressure between the members · CPC title

• F16H47/04

  the mechanical gearing being of the type with members having orbital motion · CPC title

• F16H61/0025 Primary

  Supply of control fluid; Pumps therefor · CPC title