Abstract:
A hybrid vehicle includes a generator driven by an internal combustion engine, a battery charged by the generator and an electric motor driven by the generator and the battery. A drive system transmits the output of the motor to wheels of the vehicle. When, and only when, adequate power cannot be provided by the motor to the wheels because of a fault, an emergency drive indicator issues a command to a power transmitting mechanism, which is responsive only to the command signal to directly transmit the output of the engine to the drive system.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a hybrid vehicle comprising an internal combustion engine and an electric motor as power source. 
     BACKGROUND OF THE INVENTION 
     A hybrid vehicle is known in the art comprising an internal combustion engine (ICE) and an electric motor as the power source in order to reduce the exhaust emissions of a vehicle. 
     Such a hybrid vehicle is disclosed for example by Japanese Patent Application Tokkai Hei 9-103001 published by the Japanese Patent Office in 1997. In this prior art, an ICE and an electric motor are both mechanically connected to wheels, and the wheels are driven by both the ICE and the electric motor. Therefore, the wheels can be driven by the ICE even if the electric motor breaks down. 
     However, there is also a series type of hybrid vehicle wherein all the output from the ICE is converted into power by a generator and the wheels are driven only by the electric motor. In such a series type hybrid vehicle, as the wheels are not connected to the ICE mechanically, the ICE cannot transmit its output to the wheels when the electric motor breaks down even if there is no fault in the ICE, so the vehicle therefore cannot run at all. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of this invention to enable a series type hybrid vehicle to run even when its motor breaks down. 
     In order to achieve the above object, this invention provides a series type hybrid vehicle comprising a generator driven by an internal combustion engine, a battery charged by the generator, an electric motor driven by the generator and the battery, and a drive system for transmitting the output of the electric motor to wheels. The hybrid vehicle further comprises emergency drive indicator means, and a power transmitting mechanism which directly transmits the output of the internal combustion engine to the drive system only when there is a command from the emergency drive indicator means. 
     According to an aspect of this invention, the hybrid vehicle further comprises a controller which holds the generator in a power generation stop state or a power generation minimum state and holds the electric motor in a neutral state when the output of the internal combustion engine is transmitted to the drive system via the power transmitting mechanism. 
     According to yet another aspect of this invention, the power transmitting mechanism comprises a torque converter and a clutch arranged in series with each other. 
     According to yet another aspect of this invention, the power transmitting mechanism comprises a torque converter and two clutches respectively provided on the input side and output side of the torque converter. 
     According to yet another aspect of this invention, the power transmitting mechanism further comprises direction change-over means, and a reversing mechanism which reverses the output rotation from the internal combustion engine and transmits it to the drive system when there is a command from the direction change-over means. 
     The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows the construction of a hybrid vehicle according to a first embodiment of this invention. 
     FIG. 2 is a block diagram of a controller of the hybrid vehicle. 
     FIG. 3 is a flowchart for showing the operation of the controller. 
     FIG. 4 shows the partial construction of a second embodiment of this invention. 
     FIG. 5 is similar to FIG. 1, but showing a third embodiment of this invention. 
     FIG. 6 is similar to FIG. 1, but showing a fourth embodiment of this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1 of the drawings, a series type hybrid vehicle is equipped with an internal combustion engine (ICE)  1  and a generator  3  that is connected to an output shaft  2  of the ICE  1 , a battery  4  for storing electric power generated by the generator  3 , and a pair of electric motors  5  driven by the generator  3  and battery  4 . The output of the electric motor  5  is transmitted to the wheels via a reduction gear  6 , coupling  7 , propeller shaft  8 , coupling  9 , and final drive  10 . 
     A torque converter  13  is connected to the output shaft  2  of the ICE  1  via a pair of reducing gears  12   a ,  12   b . A clutch  14  is further provided between the torque converter  13  and reduction gear  6 . These gears  12   a ,  12   b , torque converter  13  and clutch  14  comprise a power transmitting mechanism  11  for use in an emergency. 
     This hybrid vehicle comprises a controller shown in FIG. 2. A system controller  15  controls the output of the ICE  1  via an ICE controller  16 , controls the amount of power generated by the generator  3  via a generator controller  17 , and controls the output of the electric motor  5  via a motor controller  18 . 
     When a signal from an emergency drive switch  20  is input, for example when the electric motor  5  breaks down, the system controller  15  controls the output of the ICE  1 , and engages or releases the clutch  14  via an emergency drive controller  19 . 
     Signals are input to the system controller  15  from an accelerator pedal opening sensor  22  and vehicle speed sensor  23 , and the system controller  15  performs emergency drive control in accordance with the signals. 
     FIG. 3 is a flowchart describing the operation of the system controller  15  in an emergency. 
     In a step S 1 , the accelerator pedal opening and vehicle speed are read. In a step S 2 , it is determined whether or not the vehicle is at rest based on the accelerator pedal opening and vehicle speed. When it is determined that the vehicle is at rest, the routine proceeds to a step S 3 . In the step S 3 , it is determined whether or not the emergency drive switch  20  is ON. When it is determined that the emergency drive switch  20  is ON, the electric motor  5  is set to a neutral state and the generator  3  is set to a power generation stop state or power generation minimum state respectively in steps S 4 , S 5 , and the routine proceeds to a step S 6 . 
     In the step S 6 , it is determined whether or not a vehicle start operation has been performed by determining whether or not the accelerator pedal opening has increased. When it is determined that there has been a start operation, the routine proceeds to steps S 7 , S 8 , the clutch  14  is gradually connected, and the output of the ICE  1  is increased according to the accelerator pedal opening. 
     After the vehicle has started and begun running, running is continued until it is determined that a vehicle stop operation has been performed. When it is determined, in a step S 9 , that the accelerator pedal opening is zero and the vehicle speed is equal to or less than a predetermined value (very low speed), i.e. that a stop operation has been performed, the clutch  14  is disengaged in a step S 10 , the emergency drive switch  20  is switched OFF in a step S 11 , and control is terminated. 
     Next, the operation of this hybrid vehicle will be described. During normal running, the ICE  1  drives only the generator  3 . The electric motor  5  is driven by power supplied from the generator  3 . The rotation speed of the electric motor  5  is controlled according to the accelerator pedal opening, and the rotation speed rises the more the accelerator pedal opening increases. As the clutch  14  is then released, the output of the ICE  1  is not transmitted to the electric motor  5  via the clutch  14 . 
     On the other hand, when a fault occurs in the electric motor  5 , the vehicle is first stopped, and when the emergency drive switch  20  is turned ON, a shift to the emergency drive mode takes place. 
     The generator  3  then enters the power generation stop state or power generation minimum state, and the electric motor  5  goes into the neutral state. When the driver steps on the accelerator pedal, the clutch  14  is gradually connected. The output of the ICE  1  is input to the reduction gear  6  via the clutch  14 , and is transmitted to the wheels. As a result, the vehicle can be driven directly by the ICE  1  when, for example, the electric motor  5  breaks down. 
     When the accelerator pedal is released and the vehicle is slowed down, the clutch  14  is again released, so transmission of the output of the ICE  1  to the wheels is interrupted, and the vehicle can be brought to rest. 
     Therefore, even if the electric motor  5  breaks down, the vehicle can be safely moved to a required location. 
     As the output of the ICE  1  is input to the reduction gear  6  via the torque converter  13 , the output of the ICE  1  can be increased and transmitted, and the drive force necessary to run the vehicle can be obtained even during emergency drive. Also as torque can be transmitted smoothly, transmission shocks can be reduced. The vehicle can still be moved smoothly even without the torque converter  13  provided that the clutch  14  is present. 
     During emergency drive, as the generator  3  is maintained in the power generation stop state or minimum power state, and the electric motor  5  is maintained in the neutral state, the output of the ICE  1  used to drive the generators and motor  5  can be reduced. As a result, nearly all the output of the ICE  1  can be used to drive the wheels, and good running performance is ensured. 
     FIG. 4 shows a second embodiment of this invention. This embodiment is different from the first embodiment in that clutches  14   a  and  14   b  are respectively provided on the input side and the output side of the torque converter  13 . 
     According to this embodiment, the torque converter  13  can be kept completely separate from the ICE  1  and the electric motor  5  during normal running of the vehicle. Due to this, a loss of output of the ICE  1  which occurs due to driving the torque converter  13  during normal running, is eliminated. 
     FIG. 5 shows a third embodiment of this invention. This embodiment is different from the first embodiment in that a reversing mechanism  25  is interposed between the torque converter  13  and clutch  14   b  in addition to the torque converter  13  and clutches  14   a ,  14   b . This reversing mechanism  25  is the same as the mechanism used to change-over to reverse gear of a transmission known in the art. 
     A signal selecting “forward” or “reverse” is input from a direction change-over switch  21  to the emergency drive controller  19 . An actuator, not illustrated, displaces a moving engaging gear  26  according to the signal from this direction change-over switch  21 , so as to change-over between a state wherein the output rotation of the ICE  1  is directly transmitted to the wheels, and a state wherein the output is reversed before transmitting to the wheels. 
     The vehicle can therefore be made to move not only forwards but also backwards, and the operability of the vehicle in an emergency improves. 
     FIG. 6 shows a fourth embodiment of this invention. This embodiment is different from the third embodiment in that the power transmitting mechanism  11  is provided on the opposite side of the generator  3 . Due to this, there is more degree of freedom in the layout of the ICE  1  and the power transmitting mechanism  11 .