Interrelated power delivery controls – including engine control – Plural engines – Electric engine
Reexamination Certificate
2002-04-18
2004-05-18
Bucci, David A. (Department: 3682)
Interrelated power delivery controls, including engine control
Plural engines
Electric engine
C477S045000
Reexamination Certificate
active
06736753
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2001-148891 filed on May 18, 2001 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to vehicle drive control apparatus and method, and more particularly, to an improvement in a drive control apparatus of a vehicle capable of running in different running modes in which the states of operation of various drive power sources vary.
2. Description of Related Art
In known vehicles, drive wheels are rotated via a power transmission apparatus capable of changing the transfer torque capacity. For example, a vehicle, described in Japanese Patent Application Laid-Open No. 3-209050, has as a power transmission apparatus capable of changing the transfer torque capacity, a belt-type continuously variable transmission that transfers power by clamping a transmission belt via a hydraulic actuator, and shifts the transmission speed ratio by changing the groove width of a pair of variable pulleys. The belt-type continuously variable transmission is designed so that the transfer torque capacity can be adjusted by changing the pressure receiving area of the hydraulic actuator, and the transfer torque capacity (receiving area) is controlled in accordance with the input torque so as to prevent the belt from slipping. According to this conventional technology, the transfer torque capacity is controlled by oil pressure instead of the pressure-receiving area.
The aforementioned transfer torque capacity is set so as not to allow the belt to slip, factoring in the torque change characteristic of the drive power source, etc., with a certain safety factor. Therefore, the setting of the transfer torque capacity is not necessarily satisfactory in the case of hybrid vehicles equipped with a plurality of drive power sources. That is, in a hybrid vehicle having an internal combustion engine and an electric motor as drive power sources, it is necessary to employ an increased safety factor since relatively great torque fluctuations are caused by the internal combustion engine. Hence, if the transfer torque capacity is set in consideration of the internal combustion engine, the transfer torque capacity becomes greater than a needed capacity during a vehicle run caused by the electric motor, which produces less fluctuations in torque and allows high control precision. The greater than needed transfer torque capacity increases the power transfer loss of the transmission, the energy loss of an oil pump for producing oil pressure, etc., thus degrading the fuel economy.
This problem occurs not only in the hydraulic belt-type continuously variable transmissions, but also in power transmission apparatus capable of changing the transfer torque capacity. Various examples of the power transmission apparatus include, for example, a running mode changing apparatus, a forward-rearward switch apparatus, or a stepwise variable transmission equipped with clutches and brakes that are hydraulically put into a friction-engaged state, if the transfer torque capacity is controlled in accordance with the transfer torque (input torque).
During a running mode in which the operation states of drive power sources are changed, the torque may fluctuate due to, for example, the startup of the internal combustion engine, the fuel cut, etc. Consequently, the transfer torque capacity may become insufficient, and the belt may slip. If the running mode is changed by changing the engaged/released states of the clutches and brakes, the belt may slip due to torque fluctuations at the time of engagement or release of such a clutch or brake.
At the time of an ascending start on a slope, the vehicle may move down in a direction opposite to the direction of the ascending start. In such a case, there is a possibility that when great torque is applied in the direction of start, the transfer torque capacity may become insufficient and may allow the belt, a clutch or a brake to slip.
SUMMARY OF THE INVENTION
It is an object of the invention to control the transfer torque capacity of a power transmission apparatus so as to reduce the power transfer loss and the energy loss and prevent the slipping of the power transmission apparatus due to insufficient transfer torque capacity.
In a first aspect of the invention, a vehicle drive control apparatus includes a plurality of drive power sources that rotate a drive wheel via a power transfer device that changes a transfer torque capacity, and causes a vehicle to run in a plurality of run modes that differ in states of operation of the drive power sources. This vehicle drive control apparatus changes the transfer torque capacity of the power transfer device in accordance with the run modes.
The transfer torque capacity is a maximum torque that the power transfer device is able to transfer without allowing a slip or the like.
According to the first aspect, the transfer torque capacity of the power transfer device is changed in accordance with the mode of run of the vehicle. Therefore, by setting a minimum sufficient transfer torque capacity in accordance with the torque fluctuation characteristics of the individual drive power sources, it becomes possible to reduce the power transfer loss due to excessive transfer torque capacity and the energy loss of an oil pump or the like for generating a transfer torque capacity while avoiding the slipping of the power transfer device due to insufficient transfer torque capacity. Thus, fuel economy improves.
In the first aspect, the vehicle drive control apparatus may be constructed so that (a) the drive power sources include an internal combustion engine, wherein the run modes include a run mode in which the internal combustion engine is used, and a run mode in which the internal combustion engine is not used, and (b) the transfer torque capacity is made smaller during the run mode in which the internal combustion engine is not used than during the run mode in which the internal combustion engine is used. In this construction, the internal combustion engine is provided as a drive power source and the transfer torque capacity is made smaller during the run mode in which the engine is not used than during the run mode in which the engine is used. Therefore, insufficient transfer torque capacity due to torque fluctuations of the internal combustion engine is avoided. Furthermore, since the transfer torque capacity is made smaller during a run mode in which the internal combustion engine is not used, that is, a run mode in which the torque fluctuation is small, the power transfer loss and the energy loss of the oil pump or the like are reduced and fuel economy is improved.
In a second aspect of the invention, a vehicle drive control apparatus includes a plurality of drive power sources that rotate a drive wheel via a power transfer device that changes a transfer torque capacity, and causes a vehicle to run in a plurality of run modes that differ in states of operation with respect to the drive power sources. The vehicle drive control apparatus increases the transfer torque capacity of the power transfer device when the run mode is changed.
According to the second aspect, since the transfer torque capacity of the power transfer device is increased at the time of the changing of the run mode at which the states of operation of the drive power sources are changed, it is possible to prevent the slipping of the power transfer device due to insufficient transfer torque capacity regardless of, for example, torque fluctuations at the time of startup of an internal combustion engine as a drive power source or at the time of a fuel cut, or torque fluctuations at the time of engagement and release of a clutch and a brake for changing the run mode. That is, by reducing the transfer torque capacity at occasions other than the time of change in the run mode, the power transfer loss due to excessive transfer torque capacity and the energy loss of the oil pump for producing the transfer torque cap
Endo Hiroatsu
Hoshiya Kazumi
Ozeki Tatsuya
Bucci David A.
Oliff & Berriedge, PLC
Van Pelt Bradley J.
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