Abstract: The control technique of the invention sets smaller values to an engine stop reference value and an engine start reference value in the state of use of a regular fuel, compared with values in the ordinal state. When a calculated engine power demand Pe* is less than the engine stop reference value, the control stops the operation of the engine. When the calculated engine power demand Pe* exceeds the engine start reference value, on the other hand, the control starts the operation of the engine. This arrangement facilitates the start of the engine in the state of use of the regular fuel, compared with the start in the ordinary state. A corrective revolution speed ?N is added to a target revolution speed Ne* of the engine, in order to respond to a decrease in output power from the internal combustion engine.

Abstract: A hybrid automobile runs by transmitting a power from an engine and a power from a motor-generator MG2, and can store a part of the power from the engine and an electric power generated by a motor-generator MG1. In this hybrid automobile, a power requirement Pr* of a drive shaft is set based on an accelerator opening, and a battery charge electric power Pbi is set based on SOC, and the sum of the power requirement Pr* and the battery charge electric power Pbi are set as an engine target power Pe*. When the engine target power Pe* is less than a predetermined minimum value Plow, the engine target power Pe* is changed to the minimum value Plow. Further, in accordance with this change, the battery charge electric power Pbi is also changed, and the engine and the motor-generators MG1, MG2 are operated.

Abstract: A hybrid automobile runs by transmitting a power from an engine and a power from a motor-generator MG2, and can store a part of the power from the engine and an electric power generated by a motor-generator MG1. In this hybrid automobile, a power requirement Pr* of a drive shaft is set based on an accelerator opening, and a battery charge electric power Pbi is set based on SOC, and the sum of the power requirement Pr* and the battery charge electric power Pbi are set as an engine target power Pe*. When the engine target power Pe* is less than a predetermined minimum value Plow, the engine target power Pe* is changed to the minimum value Plow. Further, in accordance with this change, the battery charge electric power Pbi is also changed, and the engine and the motor-generators MG1, MG2 are operated.

Abstract: A method of controlling an engine-operating-characteristic changing device operable between a first and a second operating state and including a locking device for locking the changing device in the first operating state in which a compression ratio of an intake air of an internal combustion engine is maintained at a value higher than that in the second operating state, the method including steps of determining whether there is a possibility that the engine-operating-characteristic changing device is locked in the first operating state by the locking device, where the changing device should not be placed in the first operating state, and if it is determined that there is the possibility, implementing a preventive operation to prevent the locking unit from locking the changing device in the first operating state.

Abstract: A delay time for delaying starting of an internal combustion engine in a hybrid vehicle is set to a predetermined time based on an engine coolant temperature and a state of an air conditioner switch. Starting of the engine is delayed for the predetermined time if it is determined that a vehicle can run using only a motor based on a required torque, a required power and an SOC of the battery. The predetermined time is determined based on a time necessary for completing preheating of an engine by a preheating device, preparations of sensors such as an air-furl ratio sensor, and warming-up of an exhaust gas purifying device. As a result, it is possible to efficiently perform start of the engine and operation immediately after the engine start, and to make control at the engine start time simple.

Abstract: When a starter switch is switched from OFF to ON, a hybrid ECU determines that a driver intends to start driving a vehicle, reads a temperature of each of items (engine coolant, injectors, lubricating oil, and the like), and makes a determination on the necessity of preheating depending on whether each of the items has reached a corresponding one of suitable temperatures. If preheating is required, the hybrid ECU sets an engine start permission flag so as to prohibit the engine from being started, and instructs an engine ECU to preheat the item requiring preheating. On the other hand, if every one of the items has reached the suitable temperature range of its own, the hybrid ECU determines that preheating is not required, and sets the engine start permission flag so as to permit the starting of the engine.

Abstract: A method of controlling an engine-operating-characteristic changing device operable between a first and a second operating state and including a locking device for locking the changing device in the first operating state in which a compression ratio of an intake air of an internal combustion engine is maintained at a value higher than that in the second operating state, the method including steps of determining whether there is a possibility that the engine-operating-characteristic changing device is locked in the first operating state by the locking device, where the changing device should not be placed in the first operating state, and if it is determined that there is the possibility, implementing a preventive operation to prevent the locking unit from locking the changing device in the first operating state.