Patent US3903756A successfully refreshed from Google Patents.
US3903756A
Expired / Lapsed
US
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Hydromechanical transmission
Assignee: ZF Friedrichshafen AG
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Filing: 1974-02-14
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Granted: 1975-09-09
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Expires: 1994-02-14
Abstract
Abstract An input shaft, driven by an engine with a predetermined range of operating speeds, is connectable to an output shaft through a power train with a mechanical branch and a hydraulic branch. First, second and third hydrostatic speed sensors on the input shaft, on an intermediate shaft and on the output shaft control the delivery rate of a reversible variable-displacement pump in the hydraulic branch through a hydraulic servomechanism. Whenever the engine operates below its normal speed range in forward drive, and at all speeds in reverse drive, the mechanical branch is ineffectual and the servomechanism responds to the output pressure of the pump and to the output pressures of the first and third speed sensors to adapt its delivery rate to the load. At a predetermined engine speed within the normal range, on forward drive, the second speed sensor becomes effective to allow a switchover to mixed hydraulic/mechanical operation as soon as the speeds of the input and intermediate shafts are equal. Thereupon, and until the engine speed drops below the normal range, the servomechanism responds only to the first and third sensors to reduce the delivery rate upon any acceleration of the input and/or output shafts.
Inventors
- 👤 Karlmann Hamma
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 20:29
CPC Classifications
F; F16; F16H; F16H47/00; F16H47/02; F16H47/04; F16H61/00; F16H61/38; F16H61/40; F16H61/46; F16H61/462; F16H37/00; F16H37/02; F16H37/06; F16H37/08; F16H37/0833; F16H37/084; F16H2037/088; Y; Y10; Y10T; Y10T74/00; Y10T74/19; Y10T74/19023; Y10T74/19037
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
256 words
A hydromechanical transmission for driving a load from an engine having a predetermined range of operating speeds, comprising: an input shaft coupled to said engine; an output shaft coupled to said load; a power train between said input and output shafts including a mechanical branch and a hydraulic branch; a hydrostatic torque converter in said hydraulic branch including a variable-displacement pump and a constantdisplacement motor in tandem therewith; speed-sensing means in said power train; servo-control means for said pump connected to said speedsensing means and to said torque converter for making the delivery rate of said pump per input-shaft revolution dependent on the output pressure of said pump and on the speeds of said shafts, said servo-control means having a first operating condition for varying said delivery rate directly with the speed of said input shaft and inversely with said output pressure and with the speed of said output shaft, said servocontrol means further having a second operating condition for varying said delivery rate inversely with the speed of either of said shafts independently of said output pressure; and switchover means in said power train responsive to said speedsensing means for deactivating said mechanical branch at engine speeds below said range and for activating said mechanical branch at engine speeds within said range upon equalization of the speeds of said input and output shafts, said servo-control means being coupled to said switchover means for assuming said first operating condition in the deactivated state and said second operating condition in the activated state of said mechanical branch.
Claim 2
Dependent Claim
256 words
A hydromechanical transmission for driving a load from an engine having a predetermined range of operating speeds, comprising: an input shaft coupled to said engine; an output shaft coupled to said load; a power train between said input and output shafts including a mechanical branch and a hydraulic branch; a hydrostatic torque converter in said hydraulic branch including a variable-displacement pump and a constantdisplacement motor in tandem therewith; speed-sensing means in said power train; servo-control means for said pump connected to said speedsensing means and to said torque converter for making the delivery rate of said pump per input-shaft revolution dependent on the output pressure of said pump and on the speeds of said shafts, said servo-control means having a first operating condition for varying said delivery rate directly with the speed of said input shaft and inversely with said output pressure and with the speed of said output shaft, said servocontrol means further having a second operating condition for varying said delivery rate inversely with the speed of either of said shafts independently of said output pressure; and switchover means in said power train responsive to said speedsensing means for deactivating said mechanical branch at engine speeds below said range and for activating said mechanical branch at engine speeds within said range upon equalization of the speeds of said input and output shafts, said servo-control means being coupled to said switchover means for assuming said first operating condition in the deactivated state and said second operating condition in the activated state of said mechanical branch.
Claim 3
Dependent Claim
182 words
A hydromechanical transmission as defined in claim 1 wherein said power train includes an intermediate shaft, first clutch means actuatable to couple said intermediate shaft to said input shaft, planetary-gear means with a first driving element coupled to said motor, a second driving element coupled to said intermediate shaft and a driven element coupled to said output shaft, and a second clutch means actuatable to establish a positive driving connection between said motor and said output shaft with consequent entrainment of said intermediate shaft at the speed and in the direction of said output shaft; said speed-sensing means including a first sensor operatively connected with said input shaft and a second sensor operatively connected with said intermediate shaft; said switchover means being connected to said first and second sensors for actuating said second clutch means to the exclusion of said first clutch means upon the speed of said input shaft exceeding that of said intermediate shaft and for actuating said first clutch means to the exclusion of said second clutch means upon said intermediate shaft attaining the speed of said input shaft.
Claim 4
Dependent Claim
34 words
A hydromechanical transmission as defined in claim 2, further comprising disabling means responsive to said first sensor for making said second sensor ineffectual at engine speeds below a predetermined speed threshold within said range.
Claim 5
Dependent Claim
48 words
A hydromechanical transmission as defined in claim 2 wherein said torque converter is provided with reversing means for selectively changing the direction of rotation of said motor, said switchover means being responsive to equality of the speeds of said input and intermediate shafts only upon codirection rotation thereof.
Claim 6
Dependent Claim
47 words
A hydromechanical transmission as defined in claim 2 wherein said first driving element is a ring gear, said second driving element is a sun gear, and said driven element is a planet carrier having at least one planet gear in mesh with said ring and sun gears.
Claim 7
Dependent Claim
179 words
A hydromechanical transmission as defined in claim 2 wherein said speed-sensing means further includes a third sensor operatively connected with said output shaft, said servo-control means having a first measuring input connected to said first sensor for receiving a first variable tending to reduce said delivery rate with a rise in the speed of said input shaft, a second measuring input connected to said pump for receiving a second variable tending to reduce said delivery rate with a rise in said output pressure, a third measuring input connected to said third sensor for receiving a third variable tending to reduce said delivery rate with a rise in the speed of said output shaft, and a fourth measuring input connected to said first sensor for receiving a fourth variable tending to increase said delivery rate with a rise in the speed of said input shaft, said fourth variable overriding said first variable in said first operating condition; said second and fourth measuring inputs being provided with cutoff means making said second and fourth variables ineffectual in said second operating condition.
Claim 8
Dependent Claim
20 words
A hydromechanical transmission as defined in claim 6 wherein said sensors are generators of hydrostatic pressures proportional to shaft speed.
Claim 9
Dependent Claim
91 words
A hydromechanical transmission as defined in claim 7 wherein said pump is provided with a control member for changing said delivery rate, said servo-control means comprising an operating member responsive to fluid pressures from said pump and from said first sensor representing said second and fourth variable, said servo-control means further comprising a mechanical connection between said oPerating member and said control member, said connection including a link of variable effective length adjustable in aiding relationship by fluid pressures from said first and third sensors constituting said first and third variables.
Claim 10
Dependent Claim
36 words
A hydromechanical transmission as defined in claim 8 wherein said link comprises a cylinder and a stepped piston in said cylinder with two lands respectively exposed to the fluid pressures from said first and third sensors.
Claim 11
Dependent Claim
38 words
A hydromechanical transmission as defined in claim 8 wherein said pump is reversible by shifting said control member between two alternate positions, said connection further including a position modifier in tandem with said link for reversing said pump.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-08 | 1979-03-10 | 1979-09-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-08 | 1983-03-10 | 1983-09-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-08 | 1987-03-10 | 1987-09-09 | $7700.00 | Window Closed / Lapsed |