JP6696342B2 - Engine starting method and engine starting device - Google Patents

Description

  The present invention relates to an engine starting method and an engine starting device.

  Conventionally, attempts have been made to reduce rattling noise generated from the gears of a vehicle. For example, Patent Document 1 discloses a technique for reducing rattle noise in a vehicle in which an axle can be driven by both an engine and a battery.

JP, 11-93725, A

  However, in recent years, a vehicle has been developed in which the axle is not driven by the rotation of the engine but is exclusively driven by a battery, and there is a demand to reduce rattle noise in such a vehicle. Such a vehicle is called a series hybrid car because the engine, battery, axle, and wheels are connected in series (series connection).

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an engine starting method and an engine starting device capable of reducing gear rattling noise in a vehicle in which an axle is not driven by rotation of an engine.

  In the engine starting method according to one aspect of the present invention, when the engine is cranked by the generator, the rotation speed of the generator is rotated to a predetermined rotation speed or higher, and then the rotation speed is reduced. The engine is ignited after the magnitude of the torque in the regenerative direction of the generator becomes equal to or greater than the friction torque of the engine.

  According to the present invention, gear rattling noise in a vehicle in which the axle is not driven by the rotation of the engine can be reduced.

FIG. 1 is a functional block diagram of a vehicle including the engine starting device of the present embodiment. FIG. 2 is a flowchart of the engine starting method according to the first embodiment. FIG. 3 is a map showing the relationship between the oil temperature of the engine 1 and the target rotation speed. FIG. 4 is a map showing the relationship between the oil temperature of the engine 1 and the rotation speed reduction rate. FIG. 5 is a timing chart of the engine starting method according to the first embodiment. FIG. 6 is a diagram showing the state of the gears in the periods T1 to T3 of FIG. FIG. 7 is a diagram showing a state of gears in a comparative example. FIG. 8 is a flow chart of an engine starting method according to the second embodiment. FIG. 9 is a map showing the relationship between the oil temperature of the engine 1, the rotation speed, and the rotation speed decrease rate. FIG. 10 is a timing chart when the rotation speed of the generator 4 is less than the target rotation speed in the engine starting method of the second embodiment. FIG. 11 is a timing chart when the rotation speed of the generator 4 is equal to or higher than the target rotation speed in the engine starting method of the second embodiment.

  Hereinafter, embodiments will be described with reference to the drawings. The same members are designated by the same reference numerals, and repeated description will be omitted.

  As shown in FIG. 1, the vehicle of the present embodiment includes an engine 1, a flywheel 2, a speed reducer 3, a generator 4, a battery 5, an electric motor 6, wheels 7, a generator inverter 8 and an electric motor inverter 9. Prepare Further, the vehicle includes an engine control unit 10, a generator control unit 11, a battery control unit 12, an electric motor control unit 13, and a control unit 14. The control unit 14 functions as an engine starting device.

  In this vehicle, the axles and wheels 7 are not driven by the rotation of the engine 1, but the axles and wheels 7 are driven by the electric motor 6 driven by the electric power of the battery 5. The engine 1, the battery 5, the axles, and the wheels 7 are They are called series hybrid cars because they are connected in series (series connection).

  The engine 1 is connected to a generator 4 via a flywheel 2 and a speed reducer 3. The speed reducer 3 is composed of gears, that is, the engine 1 is connected to the generator 4 via the gears. The engine control unit 10 is electrically connected to the engine 1.

  The generator inverter 8 is electrically connected to the generator 4 and the generator control unit 11, and the electric motor inverter 9 is electrically connected to the electric motor 6 and the electric motor control unit 13. The battery 5 is electrically connected to the generator inverter 8, the electric motor inverter 9, and the battery control unit 12.

  The engine control unit 10, the generator control unit 11, the battery control unit 12, and the electric motor control unit 13 are connected to each other via a communication line 15. The electric motor 6 is connected to an axle via a transmission or the like (not shown), and the axle is connected to wheels 7.

(First embodiment)
First, as a first embodiment, an engine starting method for the engine 1 that is not rotating will be described. When the engine 1 stops rotating, the generator 4 also stops rotating.

  As shown in FIG. 2, the control unit 14 determines whether or not an engine start request is input from the outside (S1), and when it is determined that the engine start request is not input (S1: N), the determination is performed again (S1). S1).

  When determining that the engine start request is input (S1: Y), the control unit 14 acquires the target rotation speed of the generator 4 (S3). When the generator 4 is not rotating, the control unit 14 rotates the generator 4 via the generator control unit 11. The engine 1 is also rotated by the rotation of the generator 4. When the engine 1 is started, the engine 1 is cranked by the generator 4, the teeth of the speed reducer 3 are moved (details will be described later), and then the engine 1 is ignited.

  The control unit 14 stores in advance a map showing the relationship between the oil temperature of the engine 1 and the target rotation speed as shown in FIG. 3, and in step S3, the oil temperature of the engine 1 is controlled via the engine control unit 10. It is acquired and the corresponding target rotation speed is read from the map. In the map, in the region where the oil temperature is low, the lower the oil temperature, the higher the target rotation speed is set.

  Next, the control unit 14 gives a fuel injection prohibition request to the engine control unit 10 (S5). As a result, the engine control unit 10 stops fuel injection into the engine 1.

  Next, the control unit 14 acquires the current rotation speed of the generator 4 via the generator control unit 11 and determines whether the rotation speed matches the target rotation speed (S7).

  When the acquired rotation speed does not match the target rotation speed (S7: N), the control unit 14 acquires the rotation speed again and makes a determination (S7).

  When the acquired rotation speed matches the target rotation speed (S7: Y), the control unit 14 proceeds to step S9. That is, when the engine 1 is cranked by the generator 4, the rotation speed of the generator 4 is rotated so as to be equal to or higher than a predetermined rotation speed.

  In step S9, the control unit 14 acquires the amount of decrease in the rotation speed per unit time when decreasing the rotation speed of the generator 4. The amount of decrease is a value (positive value) obtained by subtracting the rotational speed after the decrease from the rotational speed before the decrease, and is hereinafter referred to as the rotational speed decrease rate. Then, the control unit 14 reduces the rotation speed of the generator 4 according to the rotation speed reduction rate with time (S9). Specifically, by lowering the target rotation speed according to the rotation speed reduction rate over time, the rotation speed of the generator 4 also decreases.

  The control unit 14 stores in advance a map showing the relationship between the oil temperature of the engine 1 and the rotation speed decrease rate as shown in FIG. 4, and in step S9, acquires the oil temperature of the engine 1 and from the map, Read the corresponding rotation speed reduction rate. In a region where the oil temperature is low, the rotation speed decrease rate is set to be smaller as the oil temperature is higher. The reason for setting in this way will be described later.

  In step S9, the control unit 14 reduces the target rotation speed as follows. First, the next target rotation speed (referred to as the target rotation speed to be calculated) is calculated as follows. In other words, the calculation result obtained by dividing the difference between the current target rotation speed and the target rotation speed of the calculation target by the difference between the time at which the target rotation speed of the calculation target is set and the current time is equal to the rotation speed decrease rate, Calculate the target rotation speed to be calculated. Then, the generator control unit 11 is controlled so that the rotation speed of the generator 4 matches the calculated target rotation speed.

  Next, the control unit 14 acquires the magnitude and direction of the torque currently generated in the generator 4 via the generator control unit 11. Then, based on the magnitude and direction of the torque, it is determined whether or not two conditions are satisfied: (1) the direction of the torque is reversed, and (2) the magnitude of the torque is equal to or greater than the friction torque of the engine 1 ( S11). The torque direction reversal here means that the torque in the power running direction is changed to the torque in the regenerative direction.

  The friction torque is a torque in the regenerative direction generated by the friction of the engine 1. The control unit 14 stores the value of the friction torque in advance, and uses the value (friction torque) stored in advance in step S11.

  When at least one of the above two conditions is not satisfied (S11: N), the control unit 14 returns to step S9. On the other hand, when both of the above two conditions are satisfied (S11: Y), that is, when the torque in the regenerative direction of the generator 4 is equal to or greater than the friction torque, the process proceeds to step S13.

  In step S13, the control unit 14 ignites the engine 1. Specifically, an engine ignition request is given to the engine control unit 10 (S13). As a result, the engine control unit 10 ignites the engine 1 while injecting fuel into the engine 1, and the engine 1 is started.

  As shown in FIG. 3, in the region where the oil temperature is low, the lower the oil temperature of the engine 1, the higher the target rotation speed is set. This is because the friction torque is large when the oil temperature is low, and the engine 1 is difficult to start at a low rotation speed. Therefore, by increasing the target rotation speed to increase the rotation speed of the engine 1 before starting, the rotation speed can be relatively increased even after the decrease. Therefore, the engine 1 can be easily started.

  When the engine 1 is completely started, the engine control unit 10 notifies the control unit 14 of engine start completion.

  Next, the control unit 14 determines whether or not the engine start completion has been notified (S15), and if there is no notification (S15: N), the determination is performed again (S15), while if there is a notification. (S15: Y), the engine starting process ends. The control unit 14 recognizes that the start of the engine 1 is not completed until the completion of the engine start is notified, and recognizes that the start of the engine 1 is completed after the completion of the engine start is notified.

  The started engine 1 rotates the generator 4 via the speed reducer 3. The rotation causes the generator 4 to generate electricity, and the battery 5 is charged with the generated power via the generator inverter 8.

  The electric motor inverter 9 rotates the electric motor 6 by the electric power of the battery 5, the electric motor 6 drives the axle, and the wheels 7 connected to the axle are rotated. Thus, the vehicle can run.

  Further, the electric motor 6 generates electric power by braking the wheels 7, and charges the battery 5 via the electric motor inverter 9. That is, the battery 5 is charged by regeneration. Note that regenerative charging does not have to be performed if unnecessary.

Next, the engine starting method of the first embodiment will be described with reference to the timing chart of FIG.
Reference numeral 100H indicates a transition of the target rotation speed when the oil temperature of the engine 1 is high, and reference numeral 100L indicates a transition of the target rotation speed when the oil temperature of the engine 1 is low. Reference numeral 101H indicates the transition of the rotation speed of the generator 4 when the oil temperature of the engine 1 is high, and reference numeral 101L indicates the transition of the rotation speed of the generator 4 when the oil temperature of the engine 1 is low.

At time t ₁ , the target rotation speed before starting is set (step S3 in FIG. 2), and thereafter, the rotation speed of the generator 4 increases with time. Since the rotation speed of the engine 1 is the same as the rotation speed of the generator 4, it also rises. Regardless of whether the oil temperature of the engine 1 is low or high, the rotation speed of the generator 4 does not change and remains constant for a while after reaching the target rotation speed. The rotation speed of the engine 1 does not change for a while after it matches the target rotation speed and remains constant.

  Reference numeral 102 indicates the timing when it is determined that the rotation speed of the generator 4 matches the target rotation speed (S7: Y) in step S7 when the oil temperature of the engine 1 is low. Timing is omitted when the oil temperature of the engine 1 is high.

When it is determined that the rotation speed of the generator 4 matches the target rotation speed at time t ₂ (S7: Y), the target rotation speed is the elapsed time depending on the rotation speed decrease rate when the oil temperature of the engine 1 is low. Decreases with. The rotation speed of the generator 4 also decreases with time according to the rotation speed decrease rate. Since the rotation speed of the engine 1 is the same as the rotation speed of the generator 4, it also decreases.

  Similarly, even when the oil temperature of the engine 1 is high, when it is determined that the rotation speed of the generator 4 matches the target rotation speed (S7: Y), the target rotation speed is the rotation speed when the oil temperature of the engine 1 is high. It decreases with time according to the decrease rate. The rotation speed of the generator 4 also decreases with time according to the rotation speed decrease rate. Since the rotation speed of the engine 1 is the same as the rotation speed of the generator 4, it also decreases.

  Here, as shown in FIG. 4, the reason why the rotation speed decrease rate is reduced as the oil temperature is higher will be described. First, as shown in FIG. 3, the higher the oil temperature of the engine 1, the lower the target rotation speed is set. With the target rotation speed, the rotation speed of the engine 1 before starting also decreases. If the rotation speed decrease rate is increased and the rotation speed of the engine 1 is rapidly decreased, the rotation speed may be too low and the engine 1 may not start. Therefore, the engine 1 can be easily started by decreasing the rotation speed reduction rate as the oil temperature of the engine 1 is higher.

Returning to FIG. 5, the description will be continued.
As described above, if the rotation speed becomes too low, the engine 1 may not start. Therefore, the target rotation speed is set to a predetermined minimum rotation speed Min or more, whereby the rotation speed of the engine 1 is set to the minimum rotation speed Min. The above is preferable.

  Reference numeral 103 indicates the transition of the torque generated in the generator 4 when the oil temperature of the engine 1 is low. Illustration of the transition of the torque when the oil temperature of the engine 1 is high is omitted.

In the generator 4, torque in the direction of rotating the engine 1 (torque in the power running direction) is generated at time t _1, and the torque in the power running direction increases with time. After that, the torque decreases, and the direction of the torque reverses at time t ₄ after time t ₃ when the rotation speed of the generator 4 starts decreasing. That is, the torque in the power running direction changes to the torque in the regenerative direction.

Then, in the subsequent time t _5, it determines that the magnitude of the regenerative direction of torque of the generator 4 is equal to or higher than the friction torque of the engine 1 (step of FIG. 2 S11: Y). Reference numeral Ft in FIG. 5 indicates this friction torque.

Reference numeral 104 in FIG. 5 indicates the timing of the engine ignition request when the oil temperature of the engine 1 is low. At time t _5, the magnitude of the regenerative direction of torque of the generator 4 is so determined to be greater than or equal to the friction torque of the engine 1, the engine ignition request is generated to the time t _5.

Further, in FIG. 5, reference numeral 105 indicates the transition of the torque generated in the engine 1 when the oil temperature of the engine 1 is low. In the engine 1, torque in the direction opposite to the rotation direction (torque in the regenerative direction) is generated at time t _1, and the torque in the regenerative direction rises with time. In FIG. 5, the regeneration direction is indicated by a negative value.

Engine 1 is ignited starting the engine ignition request at time t _5, when the start completion at time t _6, the torque (torque in the regenerative direction) is reduced and eventually, the direction is reversed. That is, the torque in the power running direction (plus value in FIG. 5) is the same as the direction in which the engine 1 rotates the generator 4.

Further, reference numeral 106 in FIG. 5 indicates the notification timing of engine start completion when the oil temperature of the engine 1 is low. When the engine 1 is completely started at time t ₆ , the engine control unit 10 notifies the control unit 14 that the engine has been started.

Reference numeral 107 in FIG. 5 indicates the transition of the recognition result of the engine start completion in the control unit 14. The control unit 14 recognizes that the start of the engine 1 is not completed until the engine start completion is notified at the time t _6, and the engine 1 start is completed after the engine start completion is notified at the time t _6. Recognize that you did.

In FIG. 5, a period T1 indicates a period until the time t ₃ when the rotation speed of the generator 4 starts decreasing. Period T2, the time t ₅ from time t _{3 (magnitude} of the regenerative direction of torque of the generator 4 is a time determined to be greater than or equal to the friction torque of the engine 1) shows the time to. Period T3 indicates a period of time _{t 5} or later.

Here, the periods T1 to T3 will be described in detail.
In FIG. 6, the gears 3a and 3b constitute the speed reducer 3, and the gear 3a is located on the engine 1 side and the gear 3b is located on the generator 4 side.

  As shown in FIG. 6A, in the period T1, a clockwise torque (torque in the power running direction) is generated in the gear 3b and rotates in the same direction in the figure. This causes the gear 3b to rotate the gear 3a in the counterclockwise direction. In the figure, clockwise torque (torque in the regenerative direction) is generated in the gear 3a. The gears 3a and 3b are in contact with each other at the position P1. At this time, the generator 4 is cranking the engine 1.

As shown in FIG. 6 (b), at time t ₄ of the period T2, the torque of the generator 4 is switched to the counterclockwise direction of the torque (torque in the regenerative direction) in FIG. The rotation speed of the generator 4 decreases. As a result, the gears 3a and 3b are not in contact with each other, and then the contact positions of the gears 3a and 3b are switched from the position P1 to the position P2. During this time, a clockwise torque (torque in the regenerative direction) is generated in the gear 3a in the figure, so that the sound generated when the gear 3a contacts the gear 3b at the position P2 can be reduced. Alternatively, it is possible to suppress the generation of sound when the gears 3a and 3b come into contact with each other.

  As shown in FIG. 6C, in the period T3, shortly after the start of the engine 1 is completed, the rotation direction does not change, but the torque in the engine 1 (the torque in the clockwise direction (regeneration direction) in the figure) is , The torque switches in the counterclockwise direction (power running direction) in the figure. That is, the engine 1 is in a state of rotating the generator 4.

  That is, in the period T1, the generator 4 rotates the engine 1. In the period T2, the contact position of the gear is switched. In the period T3, the engine 1 rotates the generator 4.

Here, an engine starting method as a comparative example will be described with reference to FIG. 7.
As shown in FIG. 7A, the period T1 is the same as that of the present embodiment (FIG. 6A).

  As shown in FIG. 7 (b), when the engine 1 is ignited in a state where a clockwise torque (torque in the power running direction) is generated in the gear 3b in the figure, the position where the gears 3a and 3b come into contact is the position. Switch from P1 to position P2. At this time, since a counterclockwise torque (torque in the power running direction) is generated in the gear 3a in the figure, the gear 3a collides with the gear 3b at the position P2, and a loud noise is generated at that time.

  That is, by executing the engine starting method of the present embodiment, it is possible to reduce or suppress the sound generated when the gears collide with each other.

(Second embodiment)
Next, as a second embodiment, an engine starting method from a state in which the generator 4 is cranking the engine 1 will be described with reference to the flowchart of FIG.

In FIG. 8, steps up to step S5 are the same as in FIG.
The control unit 14 acquires the current rotation speed of the generator 4 and determines whether the rotation speed is equal to or higher than the target rotation speed (S6). If the rotation speed is equal to or higher than the target rotation speed (S6: Y), the process proceeds to step S9. That is, when the engine 1 is cranked by the generator 4, the rotation speed of the generator 4 is rotated so as to be equal to or higher than a predetermined rotation speed. On the other hand, if the rotation speed is less than the target rotation speed, the process proceeds to step S7.

  The operation of step S9 is different when the acquired rotation speed matches the target rotation speed (S7: Y) and when the rotation speed is equal to or higher than the target rotation speed (S6: Y). The former operation is similar to that described with reference to FIG.

  The latter operation is different from the description in FIG. That is, the control unit 14 acquires the rotation speed decrease rate using the map of FIG. 9 and decreases the rotation speed of the generator 4 with the passage of time according to the rotation speed decrease rate (S9).

  The control unit 14 stores in advance a map showing the relationship between the oil temperature of the engine 1, the rotation speed, and the rotation speed decrease rate, as shown in FIG. 9, and in step S9, acquires the oil temperature of the engine 1, The rotation speed decrease rate corresponding to the oil temperature and the rotation speed of the engine 1 is read from the map. In a region where the oil temperature is low, the rotation speed decrease rate is set to be smaller as the oil temperature is higher. Further, the lower the rotation speed of the engine 1, the smaller the rotation speed reduction rate is set. The reason why the rotation speed decrease rate is set to be smaller as the rotation speed of the engine 1 is lower will be described later.

  Next, an engine starting method of the second embodiment will be described with reference to the timing charts of FIGS. 10 shows the case where the rotation speed of the generator 4 is determined to be less than the target rotation speed in step S6, and FIG. 11 shows that the rotation speed of the generator 4 is determined to be equal to or higher than the target rotation speed in step S6. This is the case.

First, FIG. 10 will be described.
Reference numeral 200 indicates the timing at which the engine start request is input. Reference numeral 100 indicates a transition of the target rotation speed, and reference numeral 101 indicates a transition of the rotation speed of the generator 4.

When the engine start request is input at time t ₁ and the rotation speed of the generator 4 is determined to be less than the target rotation speed in step S6 after that, the target rotation speed and the rotation speed of the generator 4 are determined as in the first embodiment. Rises over time. Then, the target rotation speed and the rotation speed of the generator 4 decrease with time according to the rotation speed decrease rate.

  Reference numeral 102 indicates the timing at which it is determined in step S7 that the rotation speed of the generator 4 matches the target rotation speed (S7: Y).

Rotational speed of the generator 4 at time t ₂ is equal to the target rotational speed (S7: Y) and it is determined, the target rotational speed in accordance with the engine speed reduction rate decreases with time. The rotation speed of the generator 4 also decreases with time according to the rotation speed decrease rate. Since the rotation speed of the engine 1 is the same as the rotation speed of the generator 4, it also decreases. As in the first embodiment, it is preferable that the target rotation speed be equal to or higher than the minimum rotation speed Min.

Reference numeral 103 indicates the transition of the torque generated in the generator 4. In the generator 4, the torque in the direction of rotating the engine 1 (torque in the power running direction) has already been generated at time t ₁ , and the torque in the power running direction increases with time. After that, the torque decreases, and the direction of the torque reverses at time t ₄ after time t ₃ when the rotation speed of the generator 4 starts decreasing. That is, the torque in the power running direction changes to the torque in the regenerative direction.

  Here, as shown in FIG. 9, the reason why the rotational speed reduction rate is set to be smaller as the rotational speed of the engine 1 is lower will be described. When the rotation speed of the engine 1 is low and the rotation speed decrease rate is increased to rapidly reduce the rotation speed of the engine 1, the rotation speed may be too low and the engine 1 may not start. Therefore, the lower the rotation speed of the engine 1 is, the smaller the rotation speed decrease rate is, so that the engine 1 can be easily started. That is, the lower the rotation speed of the engine 1, the smaller the rotation speed reduction rate, so that the engine 1 can be easily started.

Now, subsequent at time t _5, the magnitude of the regenerative direction of torque of the generator 4 is determined to be greater than or equal to the friction torque Ft of the engine 1 (step S11 in FIG. 8: Y).

Reference numeral 104 indicates the timing of the engine ignition request. Like the first embodiment, at time t _5, the engine ignition request occurs.

Reference numeral 105 indicates the transition of the torque generated in the engine 1. In the engine 1, the torque in the direction opposite to the rotation direction (torque in the regenerative direction) has already been generated at time t ₁ , and the torque in the regenerative direction rises with time.

Engine 1 is ignited starting the engine ignition request at time t _5, when the start completion at time t _6, the torque (torque in the regenerative direction) is reduced and eventually, the direction is reversed. That is, the torque in the power running direction (the positive value in FIG. 10) is the same as the direction in which the engine 1 rotates the generator 4.

Reference numeral 106 indicates the notification timing of engine start completion. When the engine 1 is completely started at time t ₆ , the engine control unit 10 notifies the control unit 14 that the engine has been started.

Reference numeral 107 indicates the transition of the recognition result of the engine start completion in the control unit 14. The control unit 14 recognizes that the start of the engine 1 is not completed until the engine start completion is notified at the time t _6, and the engine 1 start is completed after the engine start completion is notified at the time t _6. Recognize that you did.

  Similar to the first embodiment, the generator 4 rotates the engine 1 in the period T1. In the period T2, the contact position of the gear is switched. In the period T3, the engine 1 rotates the generator 4.

Next, FIG. 11 will be described.
Reference numeral 200 indicates the timing at which the engine start request is input. Reference numeral 100 indicates a transition of the target rotation speed, and reference numeral 101 indicates a transition of the rotation speed of the generator 4.

Engine start request is input to the time t _2, the the rotational speed in the subsequent step S6 it is determined that the target rotation speed more than the target rotational speed, the rotational speed of the generator 4 does not rise in response to the engine speed reduction rate, It decreases with time.

  Reference numeral 102 indicates the timing of determining that the rotation speed of the generator 4 is equal to or higher than the target rotation speed (S6: Y) in step S6.

Rotational speed of the generator 4 is equal to or higher than the target rotational speed at the time t _2: If it is determined that (S6 Y), a target rotational speed in accordance with the engine speed reduction rate decreases with time. The rotation speed of the generator 4 also decreases with time according to the rotation speed decrease rate. Since the rotation speed of the engine 1 is the same as the rotation speed of the generator 4, it also decreases.

Reference numeral 103 indicates the transition of the torque generated in the generator 4. In the generator 4, torque in the direction of rotating the engine 1 (torque in the power running direction) has already been generated. After that, the torque in the power running direction decreases, and after the time t ₃ when the rotation speed of the generator 4 starts decreasing, the direction of the torque reverses at the time t ₄ . That is, the torque in the power running direction changes to the torque in the regenerative direction.

In a subsequent time t _5, it determines that the magnitude of the regenerative direction of torque of the generator 4 is equal to or higher than the friction torque Ft of the engine 1 (step in FIG. 8 S11: Y).

Reference numeral 104 indicates the timing of the engine ignition request. Like the first embodiment, at time t _5, the engine ignition request occurs.

  Reference numeral 105 indicates the transition of the torque generated in the engine 1. In the engine 1, torque in the direction opposite to the rotation direction (torque in the regenerative direction) has already been generated.

Engine 1 is ignited starting the engine ignition request at time t _5, when the start completion at time t _6, the torque (torque in the regenerative direction) is reduced and eventually, the direction is reversed. That is, the torque in the power running direction (the positive value in FIG. 11) is the same as the direction in which the engine 1 rotates the generator 4.

Reference numeral 106 indicates the notification timing of engine start completion. When the engine 1 is completely started at time t ₆ , the engine control unit 10 notifies the control unit 14 that the engine has been started.

Reference numeral 107 indicates the transition of the recognition result of the engine start completion in the control unit 14. The control unit 14 recognizes that the start of the engine 1 is not completed until the engine start completion is notified at the time t _6, and the engine 1 start is completed after the engine start completion is notified at the time t _6. Recognize that you did.

  Similar to the first embodiment, the generator 4 rotates the engine 1 in the period T1. In the period T2, the contact position of the gear is switched. In the period T3, the engine 1 rotates the generator 4.

  As described above, according to the engine starting method and the engine starting device described above, when the engine 1 is cranked by the generator 4, the rotation speed of the generator 4 is set to be equal to or higher than a predetermined rotation speed. Then, after that, the rotation speed is reduced and the engine 1 is ignited after the magnitude of the torque in the regenerative direction of the generator 4 becomes equal to or greater than the friction torque of the engine 1. This can reduce rattling noise in a series hybrid car, that is, a vehicle in which the axle is not driven by the rotation of the engine.

  Further, reducing the rattling noise is highly significant in series hybrid cars as described below.

  First, in a series hybrid car, the engine 1 may be started irrespective of the driver's will due to a decrease in the amount of electricity stored in the battery 5 or the like, and when a rattling noise is generated at this time, the driver suddenly makes a noise. Be done. On the other hand, in a hybrid car in which the engine 1 drives an axle, the engine 1 is often started by the driver's intention, and thus there is little possibility of being surprised. In case of abruptness, the rattling noise is felt louder and the comfort is reduced. That is, it can be said that the significance of reducing the rattle noise of the series hybrid car is higher than the significance of reducing the rattle noise of the hybrid car in which the engine 1 drives the axle.

  Further, in the series hybrid car, since the engine 1 does not drive the axle, the weight load on the flywheel and the gears of the speed reducer is low. On the other hand, in a hybrid car in which the engine 1 drives the axle, the weight load on the gears is high. For this reason, the rattling noise of the series hybrid car tends to be louder, and the comfort is further reduced. That is, it can be said that the significance of reducing the rattle noise of the series hybrid car is higher than the significance of reducing the rattle noise of the hybrid car in which the engine 1 drives the axle.

  Although the embodiments of the present invention have been described above, it should not be understood that the descriptions and drawings forming a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art.

1 Engine 3 Reduction Gear 4 Generator 5 Battery 6 Electric Motor 7 Wheel 10 Engine Control Unit 11 Generator Control Unit 14 Control Unit

Claims (5)

An engine is connected to a generator via a gear, a battery is charged with electric power generated by the generator, an electric motor is rotated by the electric power of the battery to drive an axle, and the axle is driven by the rotation of the engine. A method of starting the engine of a vehicle that is not performed,
When the engine is cranked by the generator, the rotation speed of the generator is rotated to a predetermined rotation speed or more,
Then, reduce the rotation speed,
An engine starting method comprising igniting the engine after the magnitude of the torque in the regenerative direction of the generator becomes equal to or greater than the friction torque of the engine.   The engine starting method according to claim 1, wherein the predetermined rotation speed is increased as the oil temperature of the engine is lower.   3. The engine starting method according to claim 1, wherein the higher the oil temperature of the engine, the smaller the decrease amount of the rotation speed of the generator per unit time.   4. The engine starting method according to claim 1, wherein the lower the rotational speed of the engine before starting is, the smaller the decrease amount of the rotational speed of the generator per unit time is. An engine is connected to a generator via a gear, a battery is charged with electric power generated by the generator, an electric motor is rotated by the electric power of the battery to drive an axle, and the axle is driven by the rotation of the engine. A vehicle engine starting device that does not perform,
When the engine is cranked by the generator, the rotation speed of the generator is rotated to a predetermined rotation speed or higher, and then the rotation speed is decreased to set the magnitude of torque in the regenerative direction of the generator. An engine starting device comprising: a control unit that ignites the engine after the friction torque of the engine exceeds the friction torque of the engine.

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