Prime-mover dynamo plants – Electric control – Engine control
Reexamination Certificate
1999-12-03
2001-07-17
Ponomarenko, Nicholas (Department: 2834)
Prime-mover dynamo plants
Electric control
Engine control
C290S04000F, C180S065230
Reexamination Certificate
active
06262491
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a control system for a hybrid vehicle which determines the motor assist amount when the vehicle accelerates. This invention relates also to a control system for a hybrid vehicle determines whether motor assist is started, based on air intake passage pressure information and throttle state information.
This application is based on Japanese Patent Application Nos. Hei 10-347542 and Hei 10-361695, the contents of which are incorporated herein by reference.
2. Background Art
Conventionally, hybrid vehicles which carry motors as power sources for driving the vehicles in addition to engines are known. Hybrid vehicles are divided into series hybrid vehicles and parallel hybrid vehicles. In series hybrid vehicles, the engine drives a generator, which outputs electric power to the motor and the motor drives the wheels.
Because the engine and the wheels are not mechanically connected, the engine constantly runs within a rotational range which reduces fuel consumption and emissions, as compared with conventional engine vehicles.
In parallel hybrid vehicles, the motor connected to the engine assists the rotation of the drive shaft of the engine while charging a battery using a generator which is separate from the motor or is the motor itself.
Although the engine and the wheels are mechanically connected, the parallel hybrid vehicle can reduce the load to the engine. Thus, the parallel hybrid vehicle also has reduced fuel consumption and emissions as compared with conventional engine vehicles.
In the parallel hybrid vehicle, the motor for assisting the output of the engine is directly connected to the output shaft of the engine, and acts as a generator for charging the battery when the vehicle speed is reduced. Alternatively, either or both of the engine and the motor may generate the drive power, and the generator may be provided separately.
When a hybrid vehicle accelerates, the engine is assisted by the motor, and, when it decelerates, various operations are performed, such as charging the battery by deceleration regeneration, so as to maintain sufficient electric energy in the battery (hereinafter referred to as the “state of charge (remaining charge)”) to meet the driver's demands. Specifically, because high deceleration regeneration is obtained after high speed cruising, the battery regains a part of the consumed energy when decelerating. After the vehicle goes up a slope such as a mountain path, the vehicle can charge its battery by deceleration regeneration when the vehicle goes down (as disclosed in, for example, Japanese Patent Application, First Publication No. Hei 7-123509).
While a conventional hybrid vehicle obtains an engine output corresponding to the state of opening of the throttle within the partial load range of the engine, the torque from the engine is not increased when the throttle is further opened in the full throttle state. When the vehicle accelerates, the assist by the motor and the torque assist is performed evenly over the entire range from the partial load range to the full load range of the engine, while the increase in torque is stopped when the engine enters the full throttle state, so that the torque changes suddenly, which can make the driver feels uneasy.
To appropriately perform the motor assist when the vehicle accelerates, the assist amount should determined, depending on the running conditions of the vehicle, the road conditions, and the conditions of battery use.
Meanwhile, parallel hybrid vehicles determine whether to start the assist, based on whether the opening state of the throttle is above the threshold value. When it is above the threshold value, the motor is driven so as to assist the output from the engine.
The intention of the driver to accelerate the vehicle is generally reflected in the throttle opening state. Therefore, by determining whether to start the assist, based on the throttle opening state, the vehicle responds to the driver's intention. However, even in this output range, the throttle opening state may vary, depending on the rotational speed of the engine. For instance, when the engine rotational speed is 3100 rpm, the throttle opening state is 10 to 30 degrees. Then, when the engine rotational speed is decreased to 1000 rpm, the throttle opening state becomes 3 to 14 degrees. Therefore, in the high rotational speed range, detailed setting can be achieved. However, in the low rotational speed range, because the throttle opening state is decreased, it is difficult to achieve fine control of the starting of assist, and in particular, the fuel consumption may be increased.
To solve this problem, the threshold value for determining whether to start the assist may be set based on the air intake passage pressure which is in proportion to the engine torque. According to this background technique, in the partial load range, the assist decreases the load on the engine over the entire output, and reduces the intake air, thereby improving the fuel consumption. In the full throttle state of the engine, the vehicle cannot respond to the driver's intention to accelerate the vehicle, and the vehicle has such limitation.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a control system for a hybrid vehicle in which the motor smoothly performs torque assist for the driving shaft of the engine even when the vehicle accelerates through the partial load range to the full load range.
Another object of the present invention is to provide a control system which makes the reduction of the fuel consumption compatible with the response to the driver's intention, and which efficiently controls the assist, depending on the running conditions of the vehicle, i.e., when the vehicle climbs a slope.
In a first aspect of the present invention, the control system is provided for a hybrid vehicle with an engine (E) for producing a driving force for the vehicle, a motor (M) for producing an assist driving force to assist the output from the engine, and a power storage unit (battery
3
) for supplying electric energy to the motor and storing regenerated energy produced by regeneration of the motor when the vehicle decelerates. The control system selects one of an air intake passage pressure assist mode (PB assist mode) corresponding to a partial load range of the engine (the mode corresponding to the lower solid line in the graph of
FIG. 6
) and a throttle assist mode (TH assist mode) corresponding to the opening state of a throttle (the mode corresponding to the upper solid line in the graph of FIG.
6
). The control system comprises: an assist mode determining device (step S
309
) for determining whether the vehicle is in the PB assist mode or in the TH assist mode, based on the opening state of a throttle; a PB assist amount determining device (step S
312
) for determining a base assist amount (ASTPWR) in the PB assist mode, based on the rotational speed of the engine (NE) and an air intake passage pressure (PB); a throttle assist amount determining device (S
315
) for determining the base assist amount (APWRTHL/H) in the TH assist mode, based on the rotational speed of the engine, the base assist amount including a range defined by an upper threshold value (upper throttle assist amount threshold value APWRTHH) and a lower threshold value (lower throttle assist amount threshold value APWRTHL); and a TH assist amount changer (S
315
) for gradually changing the assist amount determined by the TH assist amount determining device between the upper threshold value and the lower threshold value when the vehicle runs through a partial load range to a full load range of the engine.
When the assist mode determining device determines that the vehicle is in the PB assist mode, the PB assist amount determining device determines the base assist amount based on the rotational speed of the engine and the air intake passage pressure. In the TH assist mode, the TH assist amount determining device determines the base assist amount based on
Fukuchi Hironao
Irie Nobuyuki
Izumiura Atsushi
Kitajima Shinichi
Kiyomiya Takashi
Armstrong Westerman Hattori McLeland & Naughton LLP
Honda Giken Kogyo Kabushiki Kaisha
Ponomarenko Nicholas
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