US 6,681,570 B2 · Hydrostatic transmission with pressure regulation means

Abstract

A hydrostatic transmission comprising a housing formed with a fluid sump, a center section, a hydraulic pump, and a hydraulic motor. A fluid passage is formed in the center section. A bore is open at an outer surface of the center section in communication with the fluid passage. An output operation device is provided for controlling discharged fluid of the hydraulic pump. A piston having an outer surface is reciprocally inserted into the bore so as to be allowed to project outward from the center section. A valve is disposed within the bore. The valve is biased to be closed by a spring disposed between the valve and the piston. A member interlocks with the output operation device so as to contact with the outer surface of the piston.

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Drawings

Claims16

Dependent claims

A hydrostatic transmission, comprising:

a housing formed with a fluid sump;
a center section disposed within said fluid sump;
a hydraulic pump mounted on said center section;
a hydraulic motor mounted on said center section;
a fluid passage formed in said center section for hydraulically connecting said hydraulic pump with said hydraulic motor;
a bore opening at an outer surface of said center section in communication with said fluid passage;
an output operation device for controlling discharged fluid of said hydraulic pump, wherein said output operation device is moved to an operational position from a neutral position;
a piston reciprocally inserted into said bore so as to be allowed to project outward from said center section, said piston having an outer surface;
a valve disposed within said bore for opening and closing said bore to and from said fluid passage, said valve being biased to be closed by a spring disposed between said valve and said piston;
and
a member interlocking with said output operation device so as to contact with said outer surface of said piston, wherein, when said output operation device is adjacent to said neutral position and pressure fluid in said fluid passage forcedly opens said valve and flows into said bore, said member drains said pressure fluid in said bore to a low-pressured area.

8 more elements

A hydrostatic transmission, comprising:

a housing formed with a fluid sump;
a center section disposed within said fluid sump;
a hydraulic pump mounted on said center section;
a hydraulic motor mounted on said center section;
a fluid passage formed in said center section for hydraulically connecting said hydraulic pump with said hydraulic motor;
a bore opening at an outer surface of said center section in communication with said fluid passage;
an output operation device for controlling discharged fluid of said hydraulic pump, wherein said output operation device is moved to an operational position from a neutral position;
a piston reciprocally inserted into said bore so as to be allowed to project outward from said center section, said piston having an outer surface with an opening;
a valve disposed within said bore for opening and closing said bore to and from said fluid passage, said valve being biased to be closed by a spring disposed between said valve and said piston;
and
a member interlocking with said output operation device so as to contact with said outer surface of said piston, said member having a passage in communication with said fluid sump, wherein, when said output operation device is adjacent to said neutral position, said passage of said member is brought into communication with said opening of said piston so that, if pressure fluid in said fluid passage forcedly opens said valve and flows into said bore, said pressure fluid in said bore is introduced into said fluid sump through said opening of said piston and said passage of said member.

8 more elements

A hydrostatic transmission, comprising:

a housing formed with a fluid sump;
a center section disposed within said fluid sump;
a hydraulic pump mounted on said center section;
a hydraulic motor mounted on said center section;
a pair of fluid passages formed in said center section for hydraulically connecting said hydraulic pump with said hydraulic motor;
a pair of bores opening at the same outer surface of said center section in communication with said respective fluid passages;
an output operation device for controlling discharged fluid of said hydraulic pump, wherein said output operation device is moved to operational positions from a neutral position;
a pair of pistons reciprocally inserted into said respective bores so as to be allowed to project outward from said center section, each of said pistons having an outer surface with an opening;
a pair of relief valves disposed within said respective bores so as to pass and shut a flow of fluid from said respective fluid passages to said respective bores, each of said relief valves being biased to shut said flow of fluid by a spring disposed between said relief valve and said piston, and each of said relief valves having a check valve for allowing an opposite flow of fluid from said bore to said fluid passage;
and
a member interlocking with said output operation device so as to contact with said outer surfaces of said pistons, said member having a passage, wherein, when said output operation device is adjacent to said neutral position, said openings of said pair of pistons are hydraulically connected with each other through said passage of said member so that, if fluid in a higher-pressured one of said fluid passages forcedly opens one of said relief valves and flows into one of said bores, said fluid in said one of said bores is introduced into the other of said fluid passages through said openings of said pistons, said passage of said member and said check valve of the other of said relief valves.

8 more elements

A hydrostatic transmission, comprising:

a hydraulic pump and a hydraulic motor disposed within a fluid sump;
a hydraulic fluid passage constituting a closed hydraulic circuit for said hydraulic pump and said hydraulic motor;
a pressure regulating device communicating with said closed hydraulic circuit, wherein said pressure regulating device includes a relief valve biased against hydraulic pressure in said closed hydraulic circuit;
and
an output operation device for controlling discharged fluid of said hydraulic pump, said output operation device being operatively connected to said pressure regulating device,
wherein, when said output operation device is located within a certain range including its neutral position, said pressure regulating device is brought into a first pressure setting condition, and
wherein, when said output operation device is located out of said certain range, said pressure regulating device is brought into a second pressure setting condition.

4 more elements

Dependencies are inferred from the claim text.

Description12,840 words

Summary2,673 words

#1. Field of the Invention

#The present invention relates to a hydrostatic transmission having a hydraulic pump and a hydraulic motor fluidly connected with each other. Especially, it relates to a pressure regulation means for adjusting hydraulic pressure in a closed hydraulic circuit of the hydrostatic transmission.

#2. Background Art

Brief description of the drawings22 figures

#FIG. 1 is a plan view partly in section of an interior structure of an axle driving apparatus including an HST according to an embodiment of the present invention;

#FIG. 2 is a cross-sectional view taken on line II—II of FIG. 1;

#FIG. 3 is a cross-sectional view taken on line III—III of FIG. 1;

Detailed description9,727 words

#First of all, description will be given of an axle driving apparatus as one embodiment of the present invention in accordance with FIGS. 1 to 3.

#As shown in FIGS. 2 and 3, a housing is constituted by joining an upper housing part 1 and a lower housing part 2 through a horizontal joint surface. A bearing portion for a motor shaft 4 is provided on the horizontal joint surface between upper and lower housing parts 1 and 2. Bearing portions for a pair of axles 7 are provided in upper housing part 1 so as to be located above the horizontal joint surface. Axles 7 rotatably supported by the bearing portions of upper housing part 1 project laterally outward. In the housing, a differential gear unit 23 differentially connects axles 7 with each other.

#A partition wall 8 is formed in the housing so as to divide the interior space of the housing into a first chamber R1 and a second chamber R2. As shown in FIG. 1, an HST is disposed in first chamber RI. Differential gear unit 23, a gear train interposed between motor shaft 4 and differential gear unit 23 and axles 7 are disposed in second chamber R2.

Facts

Application

10/052,816Filed 23 Jan 2002

Priority

JP 2001-01409523 Jan 2001

Published

US 2002/0095933 A125 Jul 2002

Granted

27 Jan 2004

Term ended

9 Mar 2022

Estimated · how

20 years from earliest known nonprovisional domestic filing plus recorded patent term adjustment, including 45 days of adjustment. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification11 codes

F16H 61/433
Involving adjustment of a pump or motor with adjustable output or capacity: pump capacity control by fluid pressure control means
F16D 31/02
Fluid couplings or clutches with pumping sets of the volumetric type, i.e. in the case of liquid passing a predetermined volume per revolution:…
F16D 31/08
Fluid couplings or clutches with pumping sets of the volumetric type, i.e. in the case of liquid passing a predetermined volume per revolution:…
F16H 61/40
Control of exclusively fluid gearing: hydrostatic

Timeline

23 Jan 2001Priority claimedJP 2001-014095
23 Jan 2002Application filedUS 10/052,816
14 Feb 2002Assigned to Kanzaki Kokyukoki Mfg. Co., Ltd.assignment of assignor's interest
25 Jul 2002PublishedUS 2002/0095933 A1
27 Jan 2004GrantedUS 6,681,570 B2
9 Mar 2022Term endedEstimated, includes 45 days of adjustment

Hydrostatic transmission with pressure regulation means

Life of this patent

Hydrostatic transmission with pressure regulation means

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims16

Description12,840 words

Classification11 codes

Life of this patent

Description12,840 words

Drawings