EP0258005A1
Expired / Lapsed
EP
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Control system for a continuously variable transmission
Assignee: Subaru Corp
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Filing: 1987-08-21
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Granted: —
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Expires: 2007-08-21
Abstract
Abstract A control system for a continuously variable transmission (CVT) for a motor vehicle has a transmission ratio controlled in accordance with a desired transmission ratio, by adjusting the transmission ratio changing speed. This is achieved by a control circuit (70) adjusting the oil supply to a hydraulic circuit (Figure 2a, 2b) of the CVT through the transmission ratio control valve 50. The transmission ratio changing speed is corrected by the line pressure, so that the transmission ratio is controlled in accordance with the line pressure.
Inventors
- 👤 Yoshihiko Morimoto
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 09:53
CPC Classifications
F; F16; F16H; F16H61/00; F16H61/66; F16H61/662; F16H61/66254; F16H61/66259
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
312 words
A control system for a continuously variable transmission for transmitting the power of an internal combustion engine, having a drive pulley (7) having a hydraulically shiftable disc and a hydraulic cylinder for operating the disc, a driven pulley (8) having a hydraulically shiftable disc and a hydraulic cylinder for operating the disc, a belt (11) engaging with both pulleys, the system comprising: a hydraulic circuit (Figure 2a, 2b) having a pump (21) for supplying oil to both the hydraulic cylinders, a spool type valve (40) in the hydraulic circuit for controlling the pressure; a spool type valve in the hydraulic circuit for controlling a transmission ratio by varying the oil supply to the cylinder of the drive pulley (7); means (66, 68, 70) for controlling the valves; means (71-73) for sensing operating conditions of the engine and the transmission and for producing an output signal dependent on the conditions; means (75) responsive to the output signal for producing an actual transmission ratio signal; means (76, 103, 104) responsive to the output signal for producing a desired line pressure signal and a desired transmission ratio signal; means (78, 79, 82) responsive to the desired transmission ratio signal and the actual transmisson ratio signal for producing a control signal for operating the valve control means (68) to shift the spool of the transmission ratio control valve (50) to provide a transmission ratio; means (105, 106) responsive to the desired line pressure signal for producing a control signal for operating the valve control means (66) to shift the spool of the line pressure control valve (40) to provide a line pressure; means (86) for producing a correcting signal dependent on the line pressure; means (84) responsive to the correcting signal for correcting the control signal for the transmission ratio control valve (50) so as to control the transmission ratio in accordance with the line pressure.
Claim 2
Dependent Claim
312 words
A control system for a continuously variable transmission for transmitting the power of an internal combustion engine, having a drive pulley (7) having a hydraulically shiftable disc and a hydraulic cylinder for operating the disc, a driven pulley (8) having a hydraulically shiftable disc and a hydraulic cylinder for operating the disc, a belt (11) engaging with both pulleys, the system comprising: a hydraulic circuit (Figure 2a, 2b) having a pump (21) for supplying oil to both the hydraulic cylinders, a spool type valve (40) in the hydraulic circuit for controlling the pressure; a spool type valve in the hydraulic circuit for controlling a transmission ratio by varying the oil supply to the cylinder of the drive pulley (7); means (66, 68, 70) for controlling the valves; means (71-73) for sensing operating conditions of the engine and the transmission and for producing an output signal dependent on the conditions; means (75) responsive to the output signal for producing an actual transmission ratio signal; means (76, 103, 104) responsive to the output signal for producing a desired line pressure signal and a desired transmission ratio signal; means (78, 79, 82) responsive to the desired transmission ratio signal and the actual transmisson ratio signal for producing a control signal for operating the valve control means (68) to shift the spool of the transmission ratio control valve (50) to provide a transmission ratio; means (105, 106) responsive to the desired line pressure signal for producing a control signal for operating the valve control means (66) to shift the spool of the line pressure control valve (40) to provide a line pressure; means (86) for producing a correcting signal dependent on the line pressure; means (84) responsive to the correcting signal for correcting the control signal for the transmission ratio control valve (50) so as to control the transmission ratio in accordance with the line pressure.
Claim 3
Dependent Claim
70 words
A control system as claimed in claim 1, wherein the transmission ratio control valve (50) has a chamber (51d, 51c) at both ends of the spool, the valve control means includes a hydraulic circuit (37, 38, 60) for supplying oil to the chambers, and control valve means (68) provided in the hydraulic circuit for controlling flow rate of control oil supplied to the chambers of the transmission ratio control valve.
Claim 4
Dependent Claim
42 words
A control system as claimed in claim 2, wherein the control valve means (68) is a solenoid operated on-off valve, and the control signal is a pulse train the duty ratio of which is varied to control the transmission ratio changing speed.
Claim 5
Dependent Claim
32 words
A control system as claimed in claim 2 or 3, wherein the second hydraulic circuit is provided with a regulator valve (60) for maintaining the pressure of oil at a constant value.
Claim 6
Dependent Claim
27 words
A control system as claimed in claim 1, wherein the sensing means comprises a drive pulley speed sensor, driven pulley speed sensor and throttle valve position sensor.
Claim 7
Dependent Claim
15 words
A continuously variable transmission characterised by a control system as described in any preceding claim.
References Cited (Backward Citations)
EP0027672A1
Cited
EP0182616A1
Cited
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