Interrelated power delivery controls – including engine control – Transmission control – Engine controlled by transmission
Reexamination Certificate
1999-08-20
2001-07-10
Wright, Dirk (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Engine controlled by transmission
Reexamination Certificate
active
06258008
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosures of Japanese Patent Application Nos.HEI 10-260204 filed on Sep. 14, 1998 and HEI 11-66258 filed on Mar. 12, 1999 including the specification, drawings and abstract are incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a vehicle in which an engine is automatically stopped when predetermined engine stop conditions are met and restarted when predetermined restart conditions are met, and more particularly to a control device of the vehicle for restarting the engine by engaging a predetermined clutch of an automatic transmission upon restarting.
2. Description of the Related Art
For example, as a related art, Japanese Patent Application Laid-Open No. HEI8-193531 discloses a vehicle wherein if the vehicle stops running and predetermined engine stop conditions are met, an engine is stopped automatically so as to save fuel, reduce exhaust emission, attenuate noise or the like. In such a vehicle, if predetermined engine restart conditions are met when a driver shows the intention of driving the vehicle by depressing an accelerator pedal, the engine is restarted immediately.
In a vehicle in which a hydraulic automatic transmission is installed, if an engine is stopped, an oil pump coupled to the engine is also stopped. For this reason, for example, oil that has been supplied to a forward clutch of the automatic transmission leaks out from an oil passage, thereby causing a drop in hydraulic pressure. Therefore, in restarting the engine, the forward clutch, which should be engaged during a forward running state of the vehicle, is still disengaged. In such case, unless the forward clutch is promptly engaged when the engine is restarted, the accelerator pedal is depressed, as it were, in a neutral state. Therefore, the forward clutch is engaged when the engine is at a high engine speed, whereby an engagement shock is caused. As a result, the amount of work done by the clutch increases, which may adversely affect the durability of the clutch.
Accordingly, in order to prevent such condition, a technique is proposed by the aforementioned Japanese Patent Laid-Open No. HEI 8-14076 wherein a large-sized accumulator functions to maintain the forward clutch in an engaged state until the engine which has been automatically stopped is restarted. Further, Japanese Patent Laid-Open No. HEI 9-39613 discloses a technique in which, rather than stopping the engine operation completely, the fuel supply to the engine is stopped but the engine speed is kept at an idle speed by a motor generator, such that the operation of the oil pump is not stopped.
However, the technique disclosed in Japanese Patent Laid-Open No. HEI 8-14076 in which the forward clutch is kept in an engaged state with a large-sized accumulator when the engine is stopped could not eliminate other disadvantage due to the accumulator, such as deterioration of a drain performance during shifting from a D (drive) position to an N (neutral) position, that is, retarding of the releasing speed of the forward clutch, or enlarging of the hydraulic control device, for example. Further, the technique disclosed in Japanese Patent Laid-Open No. HEI 9-39613, wherein the engine is maintained at an idle speed by a motor generator is able to reduce the fuel consumption. However, it demands a larger battery (larger capacity) because driving by the motor generator involves significant battery consumption.
SUMMARY OF THE INVENTION
The present invention has been made in the light of the aforementioned drawbacks, and it is an object of the present invention to provide a control device for restarting a vehicle wherein a predetermined clutch of a transmission to be engaged when restarting the engine is engaged without causing engagement shock, without giving rise to other disadvantages such as requiring larger battery or hydraulic control device, while preventing the deterioration of the clutch durability.
According to a first aspect of the present invention, the aforementioned drawback is eliminated by providing a control device for restarting engine of vehicle. The control device comprises an engine restart device, a predetermined clutch, a hydraulic control device, determination device and a torque-down control device. The engine restart device is connected to the engine so as to restart the engine when the engine is stopped and predetermined restart conditions are met. The predetermined clutch is engaged by oil supplied to the clutch and is connected to the engine so as to transmit torque outputted from the engine. The hydraulic control device is connected to the predetermined clutch so as to execute quick pressure increase control which quickly supplies oil temporarily to the clutch at an initial stage of hydraulic pressure supply to the clutch. The determination device determines whether the quick pressure increase control is executable. The torque-down control device reduces the engine torque, as compared to a case where the quick pressure increase control is possible, when it is determined by the determination device that the quick pressure increase control is non-executable.
The “predetermined clutch” referred to herein indicates the clutch which is engaged at the restarting of the engine. It corresponds to a “forward clutch,” for example, in a discontinuous variable transmission. Further, the “start clutch,” for example, corresponds to the “predetermined clutch” in a continuous variable transmission. In the case of a manual transmission having an automatic clutch, the “automatic clutch” corresponds to the “predetermined clutch.”
Also, the “quick pressure increase control” referred to herein, indicates the controlling of the oil supply speed (hydraulic pressure increase) when supplying oil to a predetermined clutch such that the speed is faster than in an ordinary supply. To increase the oil supply speed, such methods as setting a higher control target for the line pressure or enlarging the throttle of the oil passage, for example, may be adopted.
In the present invention, to solve the above-mentioned drawbacks, neither a large-sized accumulator is provided nor is the predetermined clutch maintained in an engaged state by rotating the engine even when the vehicle is stopped. Instead a hydraulic pressure supply for engaging a predetermined clutch is started upon engine restart.
To avoid delay at takeoff, it is necessary to engage the predetermined clutch as quickly as possible when supplying hydraulic pressure. Therefore, the aforementioned quick pressure increase control is executed. However, in the case where this quick pressure increase control is non-executable for some reason, a state may occur where the engagement of a predetermined clutch is not performed on time.
Especially when the accelerator pedal had been depressed, the engagement of the predetermined clutch is further delayed with respect to the engine start. As a result, the clutch is engaged at a high engine speed, possibly leading to a wear of the predetermined clutch and a heavy engagement shock.
Therefore, in the present invention, the engine torque is reduced (torque-down control) when the quick pressure increase control is non-executable for some reason (later explained in detail) as compared to the case where the quick pressure increase control is executable. This reduces the amount of work involved at the time of clutch engagement, thus preventing the deterioration of clutch durability.
When to terminate the torque-down control is not specifically provided. However, such terminating conditions as 1) detection of the clutch engagement completion, and 2) lapse of time predicted of engagement completion are adopted depending on the purpose.
There are many possible specific methods for reducing the engine torque. Of those methods, the easiest to implement is, for example, retarding the ignition timing by an uniform predetermined amount.
Also, the engine torque may be reduced by monitoring the engine speed, for example, and changing the method of reducing the eng
Nagano Shuji
Tabata Atsushi
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Toyota Jidosha & Kabushiki Kaisha
Wright Dirk
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