Patent Publication Number: US-2022213851-A1

Title: Hybrid vehicle control method and hybrid vehicle control device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. national stage application of International Application No. PCT/IB2019/000429, filed on Apr. 19, 2019. 
    
    
     BACKGROUND 
     Technical Field 
     The present invention relates to a hybrid vehicle control method and a hybrid vehicle control device. 
     Background Information 
     Evaporative fuel generated in a fuel tank is adsorbed in a canister mounted in a vehicle. The evaporative fuel adsorbed in the canister is purged and supplied to an internal combustion engine, or the like, when a prescribed set of conditions is satisfied. 
     For example, in Japanese Laid open application No. 2000-282917 (Patent Document 1), when the operating state shifts from a lean operating region, in which the air-fuel ratio is greater than a theoretical air-fuel ratio, to a rich operating region, in which the air-fuel ratio is below the theoretical air-fuel ratio, the evaporative fuel adsorbed in the canister is introduced into an intake system. 
     In Patent Document 1, by introducing the evaporative fuel adsorbed in the canister into the intake system, the NOx that is adsorbed on the NOx catalytic converter is released to restore (refresh) the function of the NOx catalytic converter and to reduce the NOx released from the NOx catalytic converter. The NOx catalytic converter of Patent Document 1 is arranged in the exhaust system of the internal combustion engine and absorbs NOx in an oxygen-rich atmosphere, and releases NOx as the oxygen concentration decreases. 
     However, in Patent Document 1, the evaporative fuel adsorbed in the canister is purged during the operation of the internal combustion engine (self-sustaining operation) and introduced into the intake passage. 
     Therefore, for example, when there are few opportunities for an internal combustion engine mounted in a hybrid vehicle to operate during vehicle travel, a forced purging of the canister will take place during operation of the internal combustion engine, so that the exhaust performance and combustion stability of the internal combustion engine may deteriorate due to the evaporative fuel introduced by means of the purge. 
     In other words, in a hybrid vehicle equipped with an internal combustion engine, there is potential to improve the processing of the evaporative fuel generated in the fuel tank. 
     SUMMARY 
     A hybrid vehicle according to the present invention has a canister that adsorbs the evaporative fuel that is generated in the fuel tank of the internal combustion engine, and the drive wheels of the hybrid vehicle can be driven even while the internal combustion engine is stopped. In the hybrid vehicle, when the internal combustion engine is stopped during operation of the vehicle and a prescribed set of conditions is satisfied, the electric motor connected to the internal combustion engine will rotate the internal combustion engine, and the evaporative fuel adsorbed in the canister will be introduced on the upstream side of the exhaust purification catalytic converter provided in the exhaust passage of the internal combustion engine. The hybrid vehicle then causes the evaporative fuel that has been introduced as a reducing agent to be adsorbed on the catalytic converter. 
     As a result, it becomes possible for the hybrid vehicle to supply the evaporative fuel as a reducing agent to the exhaust purification catalytic converter before the internal combustion engine starts up. 
     Therefore, the hybrid vehicle is able to suppress a deterioration of combustion stability and exhaust performance of the internal combustion engine caused by the evaporative fuel introduced by means of purging, and to secure exhaust gas purification performance of the exhaust purification catalytic converter when the internal combustion engine starts up (self-sustaining operation). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the attached drawings which form a part of this original disclosure. 
         FIG. 1  is an explanatory diagram schematically illustrating an outline of a drive system of a hybrid vehicle to which the present invention is applied. 
         FIG. 2  is an explanatory diagram schematically illustrating an outline of a system configuration of an internal combustion engine mounted in a hybrid vehicle in a first embodiment of the present invention. 
         FIG. 3  is a flowchart showing one example of a control flow of the hybrid vehicle in the first embodiment of the present invention. 
         FIG. 4  is a flowchart showing one example of a control flow of the hybrid vehicle in a second embodiment of the present invention. 
         FIG. 5  is a flowchart showing one example of a control flow of the hybrid vehicle in a third embodiment of the present invention. 
         FIG. 6  is a flowchart showing one example of a control flow of the hybrid vehicle in a fourth embodiment of the present invention. 
         FIG. 7  is an explanatory diagram schematically illustrating an outline of a system configuration of an internal combustion engine mounted in a hybrid vehicle of a fifth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     An embodiment of the present invention will be described in detail below based on the drawings. 
       FIG. 1  is an explanatory diagram schematically illustrating an outline of the drive system of a hybrid vehicle  1  to which the present invention is applied.  FIG. 2  is an explanatory diagram schematically illustrating an outline of the system configuration of an internal combustion engine  10  mounted in the hybrid vehicle  1  in a first embodiment of the present invention. 
     The hybrid vehicle  1  has a drive unit  3  that drives drive wheels  2  and a power generation unit  4  that generates electric power for driving the drive wheels  2 . 
     The drive unit  3  has a drive motor  5  that rotationally drives the drive wheels  2 , and a first gear train  6  and a differential gear  7  that transmit the driving force of the drive motor  5  to the drive wheels  2 . The drive motor  5  is supplied with electric power from a not-shown battery charged by the power generated by the power generation unit  4 . 
     The power generation unit  4  has a generator  9  that can act as an electric motor that generates the power to be supplied to the drive motor  5 , the internal combustion engine  10  that drives the generator  9 , and a second gear train  11  that transmits the rotation of the internal combustion engine  10  to the generator  9 . 
     The hybrid vehicle  1  according to the present embodiment is a so-called series hybrid vehicle that does not use the internal combustion engine  10  to power the vehicle. That is, in the hybrid vehicle  1  according to the present embodiment, the internal combustion engine  10  is dedicated to power generation, and the drive motor  5  drives the drive wheels  2  to run the vehicle. That is, the hybrid vehicle  1  according to the present embodiment can drive the drive wheels  2  even if the internal combustion engine  10  is stopped. For example, in the hybrid vehicle  1  according to the present embodiment, when the remaining battery capacity (remaining charge) of the battery is low, the internal combustion engine  10  is driven and the generator  9  generates power in order to charge the battery. 
     The drive motor  5  acts as a direct drive source for the vehicle, and is driven by AC power from the battery. For example, the drive motor  5  can be a synchronous motor with a permanent magnet rotor. 
     In addition, the drive motor  5  functions as a generator when the vehicle decelerates. That is, the drive motor  5  is a power generation motor that can charge the battery using the regenerative energy as electric power when the vehicle decelerates. 
     The first gear train  6  is for decelerating the rotation of the drive motor  5  and increasing the motor torque to secure the travel drive torque. 
     The first gear train  6  is, for example, a gear train with two-stage deceleration, and includes a motor shaft  14  equipped with a drive unit first gear  13 , and a first idler shaft  17  equipped with a drive unit second gear  15  and a drive unit third gear  16 . The motor shaft  14  is a rotary shaft of the drive motor  5 . 
     The drive unit first gear  13  engages with the drive unit second gear  15 . 
     The drive unit third gear  16  engages with an input-side gear  18  provided on the input side of the differential gear  7 . 
     The differential gear  7  transmits the drive torque input from the first gear train  6  via the input-side gear  18  to the left and right drive wheels  2 ,  2  via left and right drive shafts  19 ,  19 . The differential gear  7  can transmit the same drive torque to the left and right drive wheels  2 ,  2  while allowing a difference in the rotational speeds of the left and right drive wheels  2 ,  2 . 
     The generator  9  comprises a synchronous motor with a permanent magnet rotor. The generator  9  converts the rotational energy generated by the internal combustion engine  10  into electrical energy and, for example, charges the battery described above. In addition, the generator  9  functions as an electric motor that rotates the internal combustion engine  10 , and functions as a starter motor when the internal combustion engine  10  is started. That is, the generator  9  acts as a power generation motor that can supply the generated electric power to the battery and that can be rotationally driven by means of the electric power from the battery. 
     The electric power generated by the generator  9  may be, for example, directly supplied to the drive motor  5  instead of charging the above-described battery in accordance with the driving state. In addition, the internal combustion engine  10  may be configured to be started by a dedicated starter motor that is not the generator  9 . 
     The second gear train  11  is a gear train that connects the internal combustion engine  10  and the generator  9 . That is, the internal combustion engine  10  and the generator  9  are mechanically connected. The second gear train  11  has an engine shaft  24  equipped with a power generation unit first gear  23 , a second idler shaft  26  equipped with a power generation unit second gear  25 , and a generator input shaft  28  equipped with a power generation unit third gear  27 . 
     At the time of the power generation operation, the second gear train  11  increases the rotational speed of the internal combustion engine  10  to transmit the required engine torque to the generator  9 . When the generator  9  functions as a starter, the second gear train  11  reduces the rotational speed of the generator  9  to transmit the required motor torque to the internal combustion engine  10 . 
     The engine shaft  24  rotates synchronously with a crankshaft (not shown) of the internal combustion engine  10 . The generator input shaft  28  rotates synchronously with a rotor (not shown) of the generator  9 . 
     The power generation unit first gear  23  engages with the power generation unit second gear  25 . The power generation unit third gear  27  engages with the power generation unit second gear  25 . That is, the power generation unit first gear  23  and the power generation unit third gear  27  engage with the power generation unit second gear  25 . 
       FIG. 2  is an explanatory diagram schematically illustrating the system configuration of the internal combustion engine  10  of the first embodiment. 
     The internal combustion engine  10  is a so-called reciprocating internal combustion engine, which converts the reciprocating linear motion of the pistons (not shown) into the rotary motion of a crankshaft (now shown) and extracts it as power. 
     The generator  9  is connected to the internal combustion engine  10 . The generator  9  thus generates electrical power by rotating the internal combustion engine  10 . 
     The internal combustion engine  10  has an intake passage  31  and an exhaust passage  32 . 
     An electric throttle valve  34 , the degree of opening of which is controlled by a control signal from a control unit  33 , is provided in the intake passage  31 . The throttle valve  34  controls the amount of intake air. 
     A purge passage  36  for introducing the evaporative fuel generated in a fuel tank  35  is connected to the intake passage  31 . The purge passage  36  is connected to the intake passage  31  downstream of the throttle valve  34 . 
     The purge passage  36  is provided with a purge control valve  37  and a canister  38 . 
     The canister  38  adsorbs the evaporative fuel generated in the fuel tank  35 . The purge control valve  37  is disposed downstream of the canister  38 . 
     An upstream side exhaust catalyst device  41 , and a downstream side exhaust catalyst device  42  positioned downstream of the upstream side exhaust catalyst device  41  are provided in the exhaust passage  32 . The upstream side exhaust catalyst device  41  and the downstream side exhaust catalyst device  42  are exhaust purification catalytic converters. 
     The upstream side exhaust catalyst device  41  comprises a first catalytic converter  43 , a second catalytic converter  44 , which is a three-way catalytic converter, and a third catalytic converter  45 , which is an NOx trap catalytic converter that are series-connected. The second catalytic converter  44  is positioned downstream of the first catalytic converter  43 . The third catalytic converter  45  is positioned downstream of the second catalytic converter  44 . 
     The first catalytic converter  43  comprises a fourth catalytic converter  46 , which is an electric heating catalytic converter, and a fifth catalytic converter  47 , which is an NOx trap catalytic converter that are series-connected. The fourth catalytic converter  46  is positioned upstream of the fifth catalytic converter  47 . 
     The first catalytic converter  43  may be a series-connected electric heating catalytic converter and a three-way catalytic converter. In this case, the electric heating catalytic converter is positioned upstream of the three-way catalytic converter. 
     The electric heating generates heat when energized. The energization of the fourth catalytic converter  46 , which is an electric heating catalytic converter, is controlled by the control unit  33 . The NOx trap catalytic converter traps NOx (nitrogen oxides) in the exhaust when the exhaust air-fuel ratio is lean, and reduces and purifies the trapped NOx when the exhaust air-fuel ratio is at or below the theoretical value, using the HC (hydrocarbons) and CO in the exhaust as reducing agents. 
     The three-way catalytic converter can simultaneously purify the NOx, HC, and CO in the exhaust with maximum conversion efficiency when the air-fuel ratio is within a so-called window centered at the theoretical air-fuel ratio. 
     An A/F sensor  51  is disposed upstream to the upstream side exhaust catalyst device  41 . The A/F sensor  51  is a so-called wide range air-fuel ratio sensor that has a substantially linear output characteristic with respect to the exhaust air-fuel ratio. 
     The downstream side exhaust catalyst device  42  is a so-called underfloor catalytic converter located for instance beneath the floor of the vehicle, and comprises a three-way catalytic converter, for example. 
     An oxygen sensor  52  and an NOx sensor  53  are disposed downstream of the downstream side exhaust catalyst device  42 . The oxygen sensor  52  detects only rich or lean air-fuel ratios by changing the output voltage ON/OFF (rich, lean) over a narrow range near the theoretical air-fuel ratio. The NOx sensor  53  is a sensor for detecting NOx concentrations. 
     In addition, the internal combustion engine  10  has a turbocharger  55  serving as a supercharger. The turbocharger  55  includes a compressor  56  provided coaxially with the intake passage  31  and an exhaust turbine  57  provided coaxially with the exhaust passage  32 . The turbocharger  55  has an electric motor  58  serving as a supercharger electric motor that can rotationally drive the compressor  56 . 
     The compressor  56  is disposed upstream of the throttle valve  34 . The compressor  56  is disposed downstream of an air flow meter, not shown. The exhaust turbine  57  is disposed upstream of the upstream side exhaust catalyst device  41 . The compressor  56  can be driven by the exhaust turbine  57  and the electric motor  58 . 
     An exhaust bypass passage  61  that bypasses the exhaust turbine  57  and connects the upstream side and the downstream side of the exhaust turbine  57  is connected to the exhaust passage  32 . The downstream end of the exhaust bypass passage  61  is connected to the exhaust passage  32  in a location upstream of the upstream side exhaust catalyst device  41 . An electric waste gate valve  62  that controls the exhaust flow rate in the exhaust bypass passage  61  is disposed in the exhaust bypass passage  61 . The waste gate valve  62  can bypass a portion of the exhaust gas that is guided to the exhaust turbine  57  to the downstream side of the exhaust turbine  57  and can control the supercharging pressure of the internal combustion engine  10 . 
     A supercharger that can be applied to the present invention is not limited to a so-called electric turbocharger that can rotate the compressor  56  with the electric motor  58 , such as the above-described turbocharger  55 . A turbocharger  55  from which the electric motor  58  has been omitted, or a mechanical turbocharger (supercharger) in which a compressor disposed in the intake passage  31  is driven by the internal combustion engine  10  may be applied to the present invention. 
     The control unit  33  is a known digital computer provided with a CPU, ROM, RAM, and an input/output interface. 
     In addition to the detection signals of the A/F sensor  51 , the oxygen sensor  52 , and the NOx sensor  53  described above, detection signals of various sensors such as an EVAP pressure sensor  63  for detecting the internal pressure of the canister  38 , a crank angle sensor  64  for detecting the crank angle of the crankshaft, and the like, are input to the control unit  33 . The crank angle sensor  64  can detect the engine rotational speed of the internal combustion engine  10 . 
     When there is a prescribed power generation request, the control unit  33  drives the internal combustion engine  10  to generate power with the generator  9 . 
     The control unit  33  controls the opening degrees of the throttle valve  34 , the purge control valve  37 , and the waste gate valve  62 . 
     The control unit  33  controls the operation of the electric motor  58  of the turbocharger  55 . 
     When there is a prescribed power generation request, the control unit  33  drives the internal combustion engine  10  to generate power with the generator  9 . 
     The control unit  33  can estimate the amount of evaporative fuel adsorbed in the canister  38  using the detected value of the EVAP pressure sensor  63 . That is, the control unit  33  corresponds to an evaporative fuel amount detection unit for detecting the state of generation of evaporative fuel. 
     The control unit  33  can use the detected values of the oxygen sensor  52  and the NOx sensor  53  to estimate the amount of HC on the downstream side of the downstream side exhaust catalyst device  42 . That is, the control unit  33  corresponds to an HC detection unit for detecting the amount of HC on the downstream side of the downstream side exhaust catalyst device  42 . 
     It is also possible to provide an oxygen sensor and an A/F sensor downstream of the downstream side exhaust catalyst device  42  to estimate the amount of HC on the downstream side of the downstream side exhaust catalyst device  42  using the detected values of these oxygen and A/F sensors. 
     The internal combustion engine  10  is not operated when power generation by the generator  9  is not required. That is, in the internal combustion engine  10  there are few opportunities to open the purge control valve  37  to purge the evaporative fuel adsorbed in the canister  38  for the introduction thereof into the intake passage  31 . Thus, there is the risk of the forced purging of the evaporative fuel in the canister  38  and the introduction thereof into the intake passage  31  during the operation of the internal combustion engine  10 . 
     Since the internal combustion engine  10  is used exclusively for power generation, an operating region that leads to a deterioration in fuel consumption is not used during power generation, and the internal combustion engine is operated at an air-fuel ratio that is leaner than the theoretical air-fuel ratio from the standpoint of enhancing fuel consumption. 
     When the internal combustion engine  10  operates with an air-fuel ratio that is leaner than the theoretical air-fuel ratio, it is more likely that the exhaust performance and the combustion stability will be adversely affected by the introduction of the evaporative fuel adsorbed in the canister  38 , as compared with operation at a rich air-fuel ratio, such as the theoretical air-fuel ratio of the internal combustion engine. 
     Therefore, in the hybrid vehicle  1  according to the first embodiment, when the internal combustion engine  10  is stopped during operation of the vehicle and a prescribed set of conditions is satisfied, a motor mode for driving the internal combustion engine  10  by means of the generator  9  is executed, and the internal combustion engine  10  to rotates (idles).by means of the generator  9 . In other words, when the internal combustion engine  10  is stopped during operation of the vehicle and a prescribed set of conditions is satisfied, the internal combustion engine  10  rotates (idles) by means of the generator  9 , with no fuel being to the internal combustion engine  10 . That is, the control unit  33  corresponds to a first control unit that causes the generator  9  to rotate (idle) the internal combustion engine  10 , when the internal combustion engine  10  is stopped during operation of the hybrid vehicle  1  and a prescribed set of conditions is satisfied. Here, the prescribed set of conditions for rotating the internal combustion engine  10  with the generator  9  may include, for example, the case in which the amount of evaporative fuel adsorbed in the canister  38  is greater than or equal to a prescribed amount, which has been set in advance. 
     During idling of the internal combustion engine  10  (when motoring the internal combustion engine  10 ), the hybrid vehicle  1  purges the evaporative fuel adsorbed in the canister  38 , the evaporative fuel is introduced into the intake passage  31  via the purge passage  36 , and the introduced evaporative fuel is adsorbed in the upstream side exhaust catalyst device  41  and the downstream side exhaust catalyst device  42  as a reducing agent. That is, the control unit  33  corresponds to a second control unit that introduces the evaporative fuel adsorbed in the canister  38  upstream to the upstream side exhaust catalyst device  41 , serving as an exhaust purification catalytic converter provided in the exhaust passage  32  of the internal combustion engine  10 , when the internal combustion engine  10  is driven the generator  9  in motor mode, and causes the introduced evaporative fuel to be adsorbed in the upstream side exhaust catalyst device  41  and the downstream side exhaust catalyst device  42  as a reducing agent. 
     In this manner, the hybrid vehicle  1  according to the present invention has the canister  38  that adsorbs the evaporative fuel generated in the fuel tank  35  of the internal combustion engine  10  that can be operated at an air-fuel ratio that is leaner than the theoretical air-fuel ratio, and can drive the drive wheels  2  even when the internal combustion engine  10  is stopped. Then, in the hybrid vehicle  1 , when a prescribed set of conditions is satisfied when the internal combustion engine  10  is stopped during vehicle operation, the internal combustion engine  10  is rotated by the generator  9 , the evaporative fuel adsorbed in the canister  38  is introduced upstream to the upstream side exhaust catalyst device  41 , which is an exhaust purification catalytic converter provided in the exhaust passage  32  of the internal combustion engine  10 , via the purge passage  36 , and the introduced evaporative fuel is adsorbed in the upstream side exhaust catalyst device  41  and the downstream side exhaust catalyst device  42  as a reducing agent. 
     At the time that the internal combustion engine  10  is driven by the generator  9  in motor node, the engine rotational speed of the internal combustion engine  10  may be controlled to be a prescribed rotational speed set in advance. This prescribed rotational speed is, for example, a rotational speed at which the introduced evaporative fuel is not discharged to the outside air from the downstream side of the downstream side exhaust catalyst device  42 . Specifically, the prescribed rotational speed is, for example, a value that is lower than the engine rotational speed when the internal combustion engine  10  is driven by the generator  9  to generate power. In other words, the above-described prescribed rotational speed is a value that is below the engine rotational speed during power generation mode when the generator  9  is driven by the internal combustion engine  10 . 
     Therefore, in the hybrid vehicle  1 , the evaporative fuel is not discharged to the outside even when the evaporative fuel is introduced upstream to the upstream side exhaust catalyst device  41  when the internal combustion engine  10  is rotated by the generator  9 , so that it is possible to suppress a deterioration in exhaust performance. 
     When the evaporative fuel is introduced into the intake passage  31 , for example, the opening degree of the throttle valve  34  is adjusted to generate a negative pressure downstream of the throttle valve  34 , and the purge control valve  37  is opened. The purge control valve  37  is controlled such that the opening degree increases as the amount of evaporative fuel adsorbed in the canister  38  increases. The opening degree of the purge control valve  37  when the evaporative fuel is introduced into the intake passage  31  may be controlled such that the introduced evaporative fuel is not discharged to the outside air from the downstream side of the downstream side exhaust catalyst device  42 . 
     Therefore, it becomes possible for the hybrid vehicle  1  to supply the evaporative fuel as a reducing agent to the upstream side exhaust catalyst device  41  and the downstream side exhaust catalyst device  42  before the internal combustion engine  10  starts up. 
     Therefore, the hybrid vehicle  1  is able to suppress a deterioration in combustion stability and exhaust performance of the internal combustion engine  10  caused by the evaporative fuel introduced by means of purging, and to secure exhaust gas purification performance of the upstream side exhaust catalyst device  41  and the downstream side exhaust catalyst device  42  when the internal combustion engine  10  starts (self-sustaining operation). A self-sustaining operation of the internal combustion engine  10  refers to an operating state in which fuel is combusted to generate driving force. 
     In the upstream side exhaust catalyst device  41  and the downstream side exhaust catalyst device  42 , when there is little reducing agent at the time of starting of the internal combustion engine  10 , the NOx is not sufficiently processed and the amount of NOx emission is high. 
     However, in the hybrid vehicle  1 , the evaporative fuel is supplied to the upstream side exhaust catalyst device  41  and the downstream side exhaust catalyst device  42  while the internal combustion engine  10  is stopped. Thus, the hybrid vehicle  1  is able to improve the NOx purification performance of the upstream side exhaust catalyst device  41  and the downstream side exhaust catalyst device  42  at the time of starting of the internal combustion engine  10 . 
     When the evaporative fuel is introduced into the intake passage  31  during lean operation in which the air-fuel ratio is controlled to be higher than the theoretical air-fuel ratio, since the variation in the air-fuel ratio is high due to the variation in the amount of evaporative fuel to be introduced, the margin for setting the air-fuel ratio will be wide, and the fuel consumption and the exhaust performance will deteriorate. 
     However, in the hybrid vehicle  1 , since the evaporative fuel is introduced into the intake passage  31  while the internal combustion engine  10  is stopped, it is unlikely that the evaporative fuel will be introduced into the intake passage  31  during lean operation of the internal combustion engine  10 . Therefore, in the hybrid vehicle  1 , since there is little variation in the amount of evaporative fuel introduced and in the air-fuel ratio, the margin when the air-fuel ratio is set can be relatively narrow, and it is possible to suppress a deterioration in fuel consumption and exhaust performance. 
     In addition, when the evaporative fuel is introduced into the intake passage  31 , it is conceivable to operate the vehicle at a different operating point than that used during lean operation, due to the problem related to margin described above. In this case, the mode fuel consumption deteriorates. Mode fuel consumption is the amount of fuel consumed (fuel consumption) when the vehicle is operated in accordance with a prescribed set of conditions. 
     However, since it is not necessary to set a dedicated operating point when introducing the evaporative fuel in the hybrid vehicle  1 , it is possible to suppress a deterioration of the mode fuel consumption. 
     In the first embodiment described above, a bypass passage  67  that bypasses the internal combustion engine  10  and that connects the intake passage  31  and the exhaust passage  32  may be provided, as shown by the broken line in  FIG. 2 . The bypass passage  67  is, for example, connected to the intake passage  31  on the downstream side of the throttle valve  34  and connected to the exhaust passage  32  on the downstream side of the downstream side exhaust catalyst device  42 . A bypass valve  68  is provided in the bypass passage  67 . For example, the bypass valve  68  is opened if the evaporative fuel is detected downstream of the downstream side exhaust catalyst device  42 , when the evaporative fuel is introduced. The opening degree of the bypass valve  68  is controlled by the control unit  33 . 
       FIG. 3  is a flowchart showing one example of a control flow of the hybrid vehicle  1  in the first embodiment described above. 
     In Step S 11 , the internal pressure of the canister  38  is detected. In Step S 12 , it is determined whether the internal combustion engine  10  is stopped. If it is determined in Step S 12  that the internal combustion engine  10  is stopped, the process proceeds to Step S 13 . If it is determined in Step S 12  that the internal combustion engine  10  is not stopped, the current routine is ended. In Step S 13 , the amount of evaporative fuel adsorbed in the canister  38  is estimated from the internal pressure of the canister  38 , and it is determined that there is a request for purging the canister  38  when the amount of evaporative fuel is greater than or equal to a prescribed amount set in advance. If there is a purge processing request in Step S 13 , the process proceeds to Step S 14 . If there is no purge processing request in Step S 13 , the current routine is ended. In Step S 14 , the generator  9  rotates the internal combustion engine  10 . In Step S 15 , the purge control valve  37  is opened. In Step S 16 , the opening degree of the purge control valve  37  is controlled such that the opening degree increases as the amount of evaporative fuel inside the canister  38  increases. 
     Other embodiments of the present invention will be described below. The same constituent elements as those of the first embodiment have been assigned the same reference numerals and redundant descriptions have been omitted. 
     The second embodiment of the present invention will now be described. In the second embodiment the opening degree of the purge control valve  37  and the engine rotational speed of the internal combustion engine  10  are controlled such that the introduced evaporative fuel is not discharged to the outside air from the downstream side of the downstream side exhaust catalyst device  42  as in the first embodiment described above. Accordingly, the system configuration of the internal combustion engine  10  in the second embodiment is the same as that of the first embodiment described above. 
       FIG. 4  is a flowchart showing one example of the control flow of the hybrid vehicle  1  of the second embodiment. 
     In Step S 21 , the internal pressure of the canister  38  is detected. In Step S 22 , it is determined whether the internal combustion engine  10  is stopped. If it is determined in Step S 22  that the internal combustion engine  10  is stopped, the process proceeds to Step S 23 . If it is determined in Step S 22  that the internal combustion engine  10  is not stopped, the current routine is ended. In Step S 23 , the amount of evaporative fuel adsorbed in the canister  38  is estimated from the internal pressure of the canister  38 , and it is determined that there is a request for purging the canister  38  when the amount of evaporative fuel is greater than or equal to a prescribed amount set in advance. If there is a purge processing request in Step S 23 , the process proceeds to Step S 24 . If there is no purge processing request in Step S 23 , the current routine is ended. In Step S 24 , the generator  9  rotates the internal combustion engine  10 . In Step S 25 , the engine rotational speed of the internal combustion engine  10  when rotated by the generator  9  is controlled such that the introduced evaporative fuel is not discharged to the outside air from the downstream side of the downstream side exhaust catalyst device  42 . In Step S 26 , the purge control valve  37  is opened. In Step S 27 , the opening degree of the purge control valve  37  is controlled such that the introduced evaporative fuel is not discharged to the outside air from the downstream side of the downstream side exhaust catalyst device  42 . 
     Even in this second embodiment, essentially the same action and effects as the first embodiment can be achieved. 
     In addition, in the second embodiment, it is possible to suppress the discharge of the introduced evaporative fuel from the exhaust passage  32  to the outside. 
     In the second embodiment shown in  FIG. 4 , either the engine rotational speed of the internal combustion engine  10  or the opening degree of the purge control valve  37  may be controlled such that the evaporative fuel is not discharged to the outside air from the downstream side of the downstream side exhaust catalyst device  42 . That is, either Step S 23  or Step S 26  may be omitted from the flowchart shown in  FIG. 4 . 
     The third embodiment of the present invention will now be described. In the third embodiment, the fourth catalytic converter  46 , which is an electric heating catalytic converter, is energized when introducing the evaporative fuel, in the first embodiment described above. Accordingly, the system configuration of the internal combustion engine  10  in the third embodiment is the same as that of the first embodiment described above. 
       FIG. 5  is a flowchart showing one example of a control flow of the hybrid vehicle  1  in the third embodiment. 
     In Step S 31 , the internal pressure of the canister  38  is detected. In Step S 32 , it is determined whether the internal combustion engine  10  is stopped. If it is determined in Step S 32  that the internal combustion engine  10  is stopped, the process proceeds to Step S 33 . If it is determined in Step S 32  that the internal combustion engine  10  is not stopped, the current routine is ended. In Step S 33 , the amount of evaporative fuel adsorbed in the canister  38  is estimated from the internal pressure of the canister  38 , and it is determined that there is a request for purging the canister  38  when the amount of evaporative fuel is greater than or equal to a prescribed amount set in advance. If there is a purge processing request in Step S 33 , the process proceeds to Step S 34 . If there is no purge processing request in Step S 33 , the current routine is ended. In Step S 34 , the generator  9  rotates the internal combustion engine  10 . In Step S 35 , the purge control valve  37  is opened. In Step S 36 , the opening degree of the purge control valve  37  is controlled such that the opening degree increases as the amount of evaporative fuel inside the canister  38  increases. In Step S 37 , the fourth catalytic converter  46 , which is an electric heating catalytic converter, is energized. 
     Even in this third embodiment, essentially the same action and effects as those of the first embodiment can be achieved. 
     In addition, in the third embodiment, by energizing the fourth catalytic converter  46 , which is an electric heating catalytic converter, to preheat the fourth catalytic converter  46 , it is possible to purify the NOx adsorbed on the fifth catalytic converter  47 , which is an NOx trap catalytic converter, with the introduced evaporative fuel. 
     If the fifth catalytic converter  47  constituting the first catalytic converter  43  is a three-way catalytic converter, by energizing the fourth catalytic converter  46 , which is an electric heating catalytic converter, to preheat the fourth catalytic converter  46 , it is possible to activate the fifth catalytic converter  47 , which is a three-way catalytic converter, in order to purify the NOx with the introduced evaporative fuel. 
     In addition, since it is possible to suppress the overall temperature of the upstream side exhaust catalyst device  41  by energizing the fourth catalytic converter  46 , it is possible to quickly raise the temperature of the upstream side exhaust catalyst device  41  to the activation temperature at the time of starting the internal combustion engine  10 . 
     The fourth embodiment of the present invention will now be described. In the fourth embodiment, the bypass passage  67  and the bypass valve  68  are provided in the first embodiment described above. Accordingly, the system configuration of the internal combustion engine  10  in the fourth embodiment is the same as that of the first embodiment described above. 
     In the fourth embodiment, evaporative fuel that did not adhere to the upstream side exhaust catalyst device  41  and the downstream side exhaust catalyst device  42  is returned to the intake passage  31  via the bypass passage  67  such that the evaporative fuel is not discharged to the outside. 
     The evaporative fuel that has flowed out to the downstream side of the downstream side exhaust catalyst device  42  can be returned to the intake passage  31  by controlling the opening degree of the throttle valve  34  to generate a negative pressure on the downstream side of the throttle valve  34 . 
       FIG. 6  is a flowchart showing one example of the control flow of the hybrid vehicle  1  of the fourth embodiment. 
     In Step S 41 , the internal pressure of the canister  38  is detected. In Step S 42 , it is determined whether the internal combustion engine  10  is stopped. If it is determined in Step S 42  that the internal combustion engine  10  is stopped, the process proceeds to Step S 43 . If it is determined in Step S 42  that the internal combustion engine  10  is not stopped, the current routine is ended. In Step S 43 , the amount of evaporative fuel adsorbed in the canister  38  is estimated from the internal pressure of the canister  38 , and it is determined that there is a request for purging the canister  38  when the amount of evaporative fuel is greater than or equal to a prescribed amount set in advance. If there is a purge processing request in Step S 43 , the process proceeds to Step S 44 . If there is no purge processing request in Step S 43 , the current routine is ended. In Step S 44 , the generator  9  rotates the internal combustion engine  10 . In Step S 45 , the purge control valve  37  is opened. In Step S 46 , the opening degree of the purge control valve  37  is controlled such that the opening degree increases as the amount of evaporative fuel inside the canister  38  increases. In Step S 47 , the amount of HC downstream of the downstream side exhaust catalyst device  42  is detected. In Step S 48 , the opening degree of the bypass valve  68  is controlled in accordance with the amount of HC downstream of the downstream side exhaust catalyst device  42 . For example, if HC is not detected downstream of the downstream side exhaust catalyst device  42 , the bypass valve  68  is closed. In addition, if HC is detected downstream of the downstream side exhaust catalyst device  42 , the opening degree of the bypass valve  68  is increased proportionally with the amount of detected increase of the HC. 
     Even in this fourth embodiment, essentially the same action and effects as those of the first embodiment can be achieved. 
     In addition, in the fourth embodiment, the evaporative fuel that was not adsorbed by the upstream side exhaust catalyst device  41  and the downstream side exhaust catalyst device  42  is returned to the intake passage  31 , so that it is possible to suppress the discharge of the introduced evaporative fuel from the exhaust passage  32  to the outside. 
     The fifth embodiment of the present invention will now be described with reference to  FIG. 7 .  FIG. 7  is an explanatory diagram schematically illustrating the system configuration of the internal combustion engine  10  of the fifth embodiment. The fifth embodiment has essentially the same configuration as the first embodiment described above, but the purge passage  36  is connected to the intake passage  31  on the upstream side of the compressor  56 . 
     When the evaporative fuel is introduced into the intake passage  31  in this fifth embodiment, for example, the electric motor  58  is used to rotate the compressor  56  to generate a negative pressure upstream to the compressor  56 , and the purge control valve  37  is opened. 
     Even in this fifth embodiment, when the internal combustion engine  10  is stopped during operation of the vehicle, the internal combustion engine  10  can be idled by the generator  9 , and the evaporative fuel adsorbed in the canister  38  can be introduced upstream to the upstream side exhaust catalyst device  41 , which is an exhaust purification catalytic converter provided in the exhaust passage  32  of the internal combustion engine  10 , via the purge passage  36 . Thus, also in this fifth embodiment, the introduced evaporative fuel can be adsorbed in the upstream side exhaust catalyst device  41  and the downstream side exhaust catalyst device  42  as a reducing agent. 
     Therefore, even in this fifth embodiment, essentially the same action and effects as those of the first embodiment can be achieved. 
     In the fifth embodiment, a bypass passage  69  that bypasses the internal combustion engine  10  and that connects the intake passage  31  and the exhaust passage  32  may be provided, as indicated by the broken line in  FIG. 7 . The bypass passage  69  is, for example, connected to the intake passage  31  on the upstream side of the compressor  56  and connected to the exhaust passage  32  on the downstream side of the downstream side exhaust catalyst device  42 . A bypass valve  70  is provided in the bypass passage  69 . For example, the bypass valve  70  is opened if the evaporative fuel is detected downstream of the downstream side exhaust catalyst device  42 , when the evaporative fuel is introduced. The opening degree of the bypass valve  70  is controlled by the control unit  33 . 
     Additionally, in the fifth embodiment, a second throttle valve  71  serving as a control valve may be provided upstream of the connection position between the purge passage  36  and the intake passage  31 , or the connection position between the bypass passage  67  and the intake passage  31 . 
     By using the bypass passage  69 , the evaporative fuel that did not adhere to the upstream side exhaust catalyst device  41  and the downstream side exhaust catalyst device  42  can be returned to the intake passage  31  such that the evaporative fuel is not discharged to the outside. 
     The evaporative fuel that has flowed out to the downstream side of the downstream side exhaust catalyst device  42  can be returned to the intake passage  31  by rotating the compressor  56  with the electric motor  58 , for example, to generate a negative pressure on the upstream side of the compressor  56 . The rotation of the electric motor  58  is controlled by the control unit  33 . 
     In addition, the evaporative fuel that has flowed out to the downstream side of the downstream side exhaust catalyst device  42  can also be returned to the intake passage  31  by controlling the opening degree of the second throttle valve  71  to generate a negative pressure on the downstream side of the second throttle valve  71 . The opening degree of the second throttle valve  71  may be controlled by the control unit  33 . 
     That is, by using the bypass passage  69 , the evaporative fuel that was not adsorbed by the upstream side exhaust catalyst device  41  and the downstream side exhaust catalyst device  42  can be returned to the intake passage  31 , so that it is possible to suppress the discharge of the introduced evaporative fuel from the exhaust passage  32  to the outside. 
     Further, an EGR passage may be used as the bypass passages  67 ,  69 . That is, the bypass passages  67 ,  69  may be EGR passages that recirculate a portion of the exhaust of the internal combustion engine  10  to the intake passage  31 . In this case, an EGR control valve that is provided in the EGR passage and controls the amount of exhaust recirculation corresponds to the bypass valves  67 ,  68 . 
     Moreover, the present invention can be applied to a hybrid vehicle other than the above-described series hybrid vehicle (for example, to a so-called parallel hybrid vehicle). In other words, the present invention can be applied to a hybrid vehicle that can drive the drive wheels  2  for vehicle travel even if the internal combustion engine  10  is stopped. 
     The above-described embodiments relate to the hybrid vehicle control method and hybrid vehicle control device.