Interrelated power delivery controls – including engine control – Transmission control – With brake control
Reexamination Certificate
2002-05-16
2004-05-18
Wright, Dirk (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
With brake control
C477S117000
Reexamination Certificate
active
06736755
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a control system for an automatic transmission, and more particularly, to a control system for a vehicle, which is provided with an idle stop controller for stopping engine idle at a standstill of the running vehicle.
BACKGROUND ART
In recent years, idle stop vehicles are already operational wherein when the running vehicle comes into a standstill, and predetermined stop conditions are formed, an engine is automatically stopped to achieve fuel savings, a reduction in exhaust emission or noises and the like. With such vehicle, when the engine is stopped, a main pump driven by the engine is stopped, so that oil supplied to a forward clutch of an automatic transmission is also drawn from a hydraulic passage, lowering the hydraulic pressure.
As a result, when the engine is restarted, the forward clutch to be engaged at forward running also releases from its engagement state. Thus, if the forward clutch is not engaged quickly at engine restart, an accelerator pedal is depressed in the neutral state as it were, which may produce an engagement shock by engagement of the forward clutch with the engine at full throttle.
Therefore, the technique described, for example, in JP-A 2000-46166 is known as means for solving this.
This technique uses two pumps wherein the main pump is operated to supply fluid, and the assist pump driven by an electric motor is operated solely at stop of the main pump such as at engine stop to compensate for flow shortage, allowing secured supply of working fluid to the automatic transmission while keeping power consumption of a battery at the minimum.
However, in the above-mentioned prior art, the assist pump driven by the electric motor is always driven at engine stop, leading to significant power consumption. Particularly, at traffic congestion or the like, there arose a problem that a great load is applied not only to the battery, but also to the motor itself for driving the assist pump.
Moreover, since the assist pump is driven by the electric motor, the pump and the electric motor should be mounted on the automatic transmission, raising a problem of deteriorating the vehicle mountability.
DISCLOSURE OF THE INVENTION
The present invention aims to provide a control system for an automatic transmission having as a hydraulic-pressure supply source a main pump driven by an engine, wherein at idle stop control, the main pump is stopped to supply the hydraulic pressure required for running at restart, allowing smooth running.
The present invention is made in view of the problem in the prior art as mentioned above. The invention as described in claim
1
provides a control system for an automatic transmission in a vehicle comprising: an engine including a starter motor for start and idle-stop control means for outputting signals for idle operation and stop for the engine to an engine control unit in accordance with preset idle stop conditions and on the basis of a vehicle speed signal sensed by a vehicle speed sensor, a steering angle signal sensed by a steering angle sensor, a signal out of brake operation detecting means for detecting brake operation and the like; and an automatic transmission for performing speed change control using as a hydraulic-pressure supply source a main pump driven by said engine, characterized by arranging a bypass hydraulic passage for ensuring communication between said main pump and a point immediately before an engagement-pressure supply port of a forward engagement element in the automatic transmission, a switching valve on said bypass hydraulic passage to allow switching between a communication state and a non-communication state, and switching-valve control means for switching said switching valve between the communication state and the non-communication state.
The control system for an automatic transmission as described in claim
1
includes no electric assist pump and the like in the prior art, so that when engine idle is stopped by idle-stop control means, the electric assist pump is not continuously operated during idle stop as well.
Therefore, idle stop control can be performed without applying a load to the battery and the electric motor and at low cost.
Moreover, the bypass hydraulic passage is arranged to ensure communication between the main pump with a point immediately before the engagement element, and the switching valve is arranged on the bypass hydraulic passage to switch between the communicating state and the non-communicating state. Therefore, by directly supplying oil to the hydraulic passages having oil discharged therefrom without waiting switching of the hydraulic passages by the shift valves, sufficient engagement pressure can quickly be supplied to the engagement element.
Further, the invention as described in claim
2
provides a control system for an automatic transmission in a vehicle comprising: an engine including a starter motor for start and idle-stop control means for outputting signals for idle operation and stop for the engine to an engine control unit in accordance with preset idle stop conditions and on the basis of a vehicle speed signal sensed by a vehicle speed sensor, a steering angle signal sensed by a steering angle sensor, a signal out of brake operation detecting means for detecting brake operation and the like; and an automatic transmission for performing speed change control using as a hydraulic-pressure supply source a main pump driven by said engine, characterized by arranging a bypass hydraulic passage for ensuring communication between said main pump and a point immediately before an engagement-pressure supply port of a forward engagement element in the automatic transmission, and switching-valve control means for switching said switching valve to the communication state during a predetermined time period when said idle-stop control means output a release command for releasing an idle stop of the engine after said idle stop.
In the control system for an automatic transmission as described in claim
2
, the bypass hydraulic passage is arranged to ensure communication between the main pump with a point immediately before the engagement element, and the switching valve is arranged on the bypass hydraulic passage to switch between the communicating state and the non-communicating state.
And the switching-valve control means are arranged for switching the switching valve to the communication state during a predetermined time period at engine restart. Specifically, in the conventional hydraulic circuit for an automatic transmission, as shown, for example, in
FIG. 10
, the shift valves are arranged to perform switching of the hydraulic passages for supplying to the engagement elements the hydraulic pressure generated by the oil pump. The shift valves are actuated to switch the hydraulic passages, allowing engagement of the engagement elements and the like. At first speed start, for example, the pilot pressures are supplied to the shift valves A, B, C to supply the engagement pressures to the low clutch L/C and the reduction brake RD/B.
However, switching of the hydraulic passages by the shift valves requires a certain hydraulic pressure, which is produced after charging oil in the hydraulic passages having oil discharged therefrom once, requiring certain time for charging oil.
As a result, unless switching of the hydraulic passages is performed by the shift valves, the hydraulic pressure is supplied to the reduction brake RD/B, the 2-4 brake 2-4/B, and the high clutch H/C as shown, for example, by the hatched portions in
FIG. 10
, falling in fourth speed.
Then, in the invention of the present application, the bypass hydraulic passage is arranged in the engagement elements for first speed engagement so as to supply oil to the hydraulic passages having oil discharged therefrom without waiting switching of the hydraulic passages by the shift valves. By directly supplying oil to the points immediately before the engagement elements during a predetermined time period, sufficient engagement pressure can quickly be supplied to the engagement
Foley & Lardner LLP
Jatco LTD
Wright Dirk
LandOfFree
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