Engine starting control device

Abstract

To provide a start control device of an engine capable of early starting the engine while suppressing torque shock.SOLUTION: An engine, a motor, a clutch for connecting the engine and the motor in a disconnectable and connectable manner, and a start control portion for starting connection of the clutch when a prescribed engine start condition is satisfied during driving of the motor and disconnection of the clutch, are provided. In a starting period from the start of the connection of the clutch to a time when a rotational frequency of the engine reaches a prescribed determination rotational frequency, fuel supply means is controlled so that a fuel is supplied to the cylinder only in an initial time of the starting period and the fuel supply to the cylinder is stopped in a later stage of the starting period.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to an engine starting control device.

Background Art

[0002] As disclosed in Patent Document 1, there is known a vehicle including an engine and a motor, wherein the engine and the motor are connected to each other by a clutch so as to be connectable and disconnectable. In such a vehicle, the engine is started by connecting the clutch during the driving of the motor to transmit the torque of the motor to the engine.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When starting the engine by transmitting the torque of the motor during driving as described above, if the engine is started only by the torque of the motor, the engine starting time becomes long. Specifically, in this case, since the clutch is gradually connected, the acceleration rate of the torque transmitted from the motor to the engine is suppressed to be small, and the rising speed of the engine speed is suppressed to be low. On the other hand, if combustion in the engine is started while transmitting the torque of the motor to the engine, the rising speed of the engine speed can be increased. However, if torque transmission from the motor to the engine and combustion in the engine are simply performed simultaneously, there is a risk that the engine speed will rise excessively and a torque shock will occur.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide an engine starting control device capable of starting the engine early while suppressing torque shock. [Means for solving the problem]

[0006] The present invention relates to a device for controlling the starting of an engine having a cylinder in which a piston is reciprocally housed and a fuel supply means for supplying fuel to the cylinder, comprising a motor, a clutch for connecting the engine and the motor so as to be able to disconnect and reconnect, and a starting control unit which starts engaging the clutch when predetermined engine starting conditions are met while the motor is running and the clutch is disengaged, wherein during the starting period from when the clutch is engaged until the engine speed reaches a predetermined determination speed, the starting control unit controls the fuel supply means such that fuel is supplied to the cylinder only in the early part of the starting period and the fuel supply to the cylinder is stopped in the later part of the starting period. Furthermore, the initial part of the starting period is the period during or before the second compression stroke of the cylinder, and the later part of the starting period is the period later than the initial part. Engine starting control device characterized by the following of provide.

[0007] In the engine starting control device of the present invention, when the engine starting conditions are met while the motor is running and the clutch is disengaged, the clutch is initiated to engage. This allows the motor's torque to be transmitted to the engine, enabling the engine to start rotating. Furthermore, in this device, during the starting period from the start of clutch engagement until the engine speed reaches a predetermined threshold speed, fuel is supplied to the cylinder only in the initial phase, and the fuel supply to the cylinder is stopped in the latter phase. Therefore, in the initial phase of the starting period, when the engine speed is sufficiently low compared to the motor speed, the torque transmitted from the motor and the combustion energy generated in the cylinder can quickly increase the engine speed. Then, in the later phase of the starting period, when the engine speed approaches the motor speed, the increase in engine speed can be suppressed. Consequently, the engine starting time, that is, the time from the start of clutch engagement until the engine speed reaches the threshold speed, can be kept short while suppressing the engine speed from exceeding the motor speed, thereby suppressing the occurrence of torque shock.

[0008] In the above configuration, preferably, the engine has a plurality of cylinders, and the starting control unit controls the fuel supply means such that during the starting period, fuel is supplied only to a specific cylinder in which the piston is stopped in the latter half of the intake stroke or the first half of the compression stroke, and such fuel supply occurs during the first compression stroke of the specific cylinder (Claim 2).

[0009] In this configuration, the piston stops in the latter half of the intake stroke or the first half of the compression stroke, and fuel is supplied to the cylinder where the air-fuel mixture is sufficiently compressed during the first compression stroke and combustion is easily achieved. This allows for more reliable acquisition of combustion energy relatively early in the starting period. As a result, the rate of increase in engine speed can be more reliably increased in the early stages of the starting period.

[0010] In the above configuration, preferably, the engine has six cylinders, and the particular cylinder is the cylinder that reaches top dead center second during the starting period (Claim 3).

[0011] With this configuration, fuel is supplied to the cylinder that reaches top dead center second, not first, resulting in a longer compression time and thus making the air-fuel mixture easier to burn. This ensures that the air-fuel mixture is reliably burned in that cylinder.

[0012] In the above configuration, preferably, the starting control unit controls the clutch such that when the stopping position of the piston of the particular cylinder is advanced compared to a predetermined determination position, the torque transmitted from the motor to the engine during the starting period is greater than when it is retarded (Claim 4).

[0013] In this configuration, when the crank angle until a particular cylinder's piston reaches top dead center (TDC) and the crank period until combustion energy is generated in that cylinder is long, the torque transmitted from the motor to the engine is increased, thereby increasing the rate at which the engine speed increases. Therefore, when the crank period until combustion energy is obtained is long, it is possible to suppress the time it takes for the engine speed to reach the predetermined speed, i.e., the engine starting time. Also, when the crank period until combustion energy is obtained is short, the torque transmitted from the motor to the engine can be kept low.

[0014] In the above configuration, preferably, the starting control unit controls the fuel supply means so that fuel is supplied to the cylinders both in the early and late stages of the starting period when the required value of the combined output of the engine and the motor is higher than a predetermined value (Claim 5).

[0015] In this configuration, when the combined output requirement of the engine and motor exceeds a predetermined value—that is, when the user is less likely to feel torque shock, such as during acceleration of the vehicle equipped with the engine and motor—the engine rotation is accelerated by combustion energy both in the early and late stages of the starting period. Therefore, the engine starting time can be shortened while minimizing the impact of torque shock on the user. [Effects of the Invention]

[0016] According to the starting control device of the present invention, the engine can be started early while suppressing torque shock. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 is a block diagram showing a schematic configuration of a vehicle to which an engine starting control device according to an embodiment of the present invention is applied. [Figure 2] This is a schematic diagram of the engine's configuration. [Figure 3] This is the engine control system block. [Figure 4] This is a diagram showing the stop positions of the compression stroke cylinder, compression transition cylinder, and expansion stroke cylinder at stop corresponding to the target stop range. [Figure 5] This is a flowchart showing the control at engine startup. [Figure 6] This is a graph showing the relationship between the stop position of the cylinder and the target clutch torque. [Figure 7] This is a graph showing the relationship between the crank angle and the clutch torque. [Figure 8] This is a diagram schematically showing the changes in each parameter at engine startup when the required output is greater than the determination output. [Figure 9] This is a diagram schematically showing the changes in each parameter at engine startup when the required output is less than or equal to the determination output.

Mode for Carrying Out the Invention

[0018] [[ID=I3]] Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.

[0019] (Overall Configuration) FIG. 1 is a schematic configuration diagram of a vehicle 100 equipped with an engine E to which the engine startup control device according to an embodiment of the present invention is applied. In the present embodiment, the vehicle 100 is a hybrid vehicle including an engine E and a motor M as drive sources of the vehicle 100 (wheels 101). The motor M is, for example, a three-phase AC synchronous motor generator. Note that the "startup control device" of the present invention is a device including at least the motor M, the clutch 102, and a controller 200 described later in the vehicle 100.

[0020] As shown in FIG. 1, in addition to the wheels 101, the engine E, and the motor M, the vehicle 100 includes a clutch 102, a battery 103 that exchanges electric power with the motor M, a transmission 104 connected to the motor M, a drive shaft 106 connected to the wheels 101, and a power transmission device 105 including a differential gear or the like that connects the transmission 104 and the drive shaft 106.

[0021] The clutch 102 connects the engine E and the motor M in a way that allows them to be connected and disconnected. More specifically, the clutch 102 connects the crankshaft 7, which is the output shaft of the engine E and will be described later, to the rotating shaft (rotor shaft, not shown) of the motor M in a way that allows them to be connected and disconnected. The clutch 102 switches the state of the engine E and the motor M between a connected state in which torque is transmitted between them and a disconnected state in which torque is not transmitted. More specifically, when the clutch 102 is connected, the state of the engine E and the motor M becomes a connected state in which torque is transmitted between them, and when the clutch 102 is disengaged (released), the state of the engine E and the motor M becomes a disconnected state in which torque is not transmitted between them. In this embodiment, the clutch 102 is hydraulic and includes a flywheel (not shown) that rotates integrally with the engine E, a clutch disc (not shown) that rotates integrally with the motor M, and a hydraulic pump (not shown) that drives them in the direction of connecting and disconnecting.

[0022] Since torque can be transmitted between the motor M and the engine E (crankshaft) via the clutch 102, when the motor M is running, the engine E is stopped, and the clutch 102 is disengaged, the engine E (crankshaft) will start to rotate when the clutch 102 is engaged.

[0023] The transmission 104 changes the input rotation speed and outputs it. For example, a transmission with 6 forward speeds and 1 reverse speed may be used as the transmission 104. The output shaft of the transmission 104 is connected to the wheel 101 via the power transmission device 105 and the drive shaft 106, and the rotational force input to the transmission 104 is transmitted to the wheel 101.

[0024] With the above configuration, the vehicle 100 can operate in three modes: a motor mode, where it runs solely on the driving force of the motor M; a combined mode, where it runs on the driving force of both the motor M and the engine E; and an engine mode, where it runs solely on the driving force of the engine E. Specifically, when the clutch 102 is disengaged, only the driving force of the motor M is transmitted to the wheels 101. On the other hand, when the clutch 102 is engaged and the motor M does not generate driving force (when the power supply to the motor M is cut off), only the driving force of the engine E is applied to the wheels 101 via the transmission 104, etc. Furthermore, when the clutch 102 is engaged and the motor M is generating driving force, the outputs of the engine E and the motor M are applied to the wheels 101 via the transmission 104, etc. In addition, the vehicle 100 in this embodiment is a vehicle capable of regenerative braking, and the motor M is configured to generate electricity from the rotational force transmitted from the wheels 101 when the vehicle 100 is decelerated. At this time, a braking force corresponding to the electricity generated by the motor M acts on the wheel 101.

[0025] (Engine configuration) Figure 2 is a schematic diagram of the engine E. Engine E comprises an engine body 1, an intake passage 30 through which intake air introduced into the engine body 1 flows, and an exhaust passage 40 through which exhaust gas discharged from the engine body 1 flows. Engine E in this embodiment is a four-stroke diesel engine and is driven by a fuel supply mainly composed of diesel oil.

[0026] The engine body 1 has a cylinder block 3 on which cylinders 2 are formed, and a cylinder head 4 that covers the cylinder block 3. The engine E of this embodiment is an inline 6-cylinder engine, and the engine body 1 (more specifically the cylinder block 3) has six cylinders 2 arranged in a line along a direction perpendicular to the plane of the paper in Figure 2.

[0027] Each cylinder 2 houses a piston 5 that is capable of reciprocating and sliding. A combustion chamber 6 is partitioned above the piston 5 in each cylinder 2. Each piston 5 is connected to the crankshaft 7 via a connecting rod 8. The crankshaft 7 rotates around its central axis in accordance with the reciprocating motion of each piston 5. The cylinder block 3 is provided with a crank angle sensor SN1 for detecting the rotation angle of the crankshaft 7, i.e., the crank angle, and consequently the engine speed.

[0028] The cylinder head 4 is fitted with one injector 15 for each cylinder 2 (combustion chamber 6) that injects fuel into the cylinder 2. The piston 5 reciprocates as it is pushed down by the expansion force caused by the combustion of the fuel-air mixture in the combustion chamber 6. The injector 15 corresponds to the "fuel supply means" of this invention.

[0029] The cylinder head 4 is provided with an intake port 9 for introducing intake air into each cylinder 2 (combustion chamber 6), an intake valve 11 for opening and closing the intake port 9, an exhaust port 10 for releasing exhaust gas generated in each cylinder 2 (combustion chamber 6), and an exhaust valve 12 for opening and closing the exhaust port 10, corresponding to each cylinder 2.

[0030] As described above, engine E is a four-stroke engine. Therefore, in each cylinder 2, the intake stroke → compression stroke → expansion stroke → exhaust stroke are performed in this order consecutively. Also, engine E is an inline six-cylinder engine. Therefore, the piston 5 in each cylinder 2 reciprocates with a phase difference of 120°CA (120 degrees in crank angle), and combustion takes place sequentially in the six cylinders 2 at 120°CA intervals.

[0031] Here, the intake, compression, expansion, and exhaust strokes as used herein refer to the periods obtained by dividing one combustion cycle, i.e., the period during which the crankshaft 7 rotates twice (360°CA), into four equal parts by the crank angle, during which intake, compression, expansion, and exhaust primarily occur, respectively. Specifically, the intake stroke as used herein refers not to the period from when the intake valve 11 actually begins to open until it closes, but to the period during which the piston 5 is located between the exhaust top dead center and the intake bottom dead center. The compression stroke refers to the period during which the piston 5 is located between the intake bottom dead center and the compression top dead center. The expansion stroke refers to the period during which the piston 5 is located between the compression top dead center and the expansion bottom dead center. The exhaust stroke refers to the period during which the piston 5 is located between the expansion bottom dead center and the exhaust top dead center. In this specification, the period during which the piston 5 is located from the intake bottom dead center to 90°CA before the intake bottom dead center is referred to as the second half of the intake stroke, and the period during which the piston 5 is located from the intake bottom dead center to 90°CA after the intake bottom dead center is referred to as the first half of the compression stroke.

[0032] The compression top dead center (TDC) is the uppermost position (closest to the cylinder head 4) within the reciprocating range of the piston 5, and is the position reached after the intake valve 11 is closed and before the exhaust valve 12 is opened. The expansion bottom dead center, exhaust top dead center, and intake bottom dead center are the positions of the piston 5 when the crankshaft 7 rotates 180°CA, 360°CA, and 540°CA forward from the state where the piston 5 is at the compression top dead center (TDC), respectively.

[0033] Each cylinder 2's intake valve 11 is driven by an intake valve train mechanism 13, which includes an intake camshaft located in the cylinder head 4. Similarly, each cylinder 2's exhaust valve 12 is driven by an exhaust valve train mechanism 14, which includes an exhaust camshaft located in the cylinder head 4. The intake valve train mechanism 13 incorporates an intake SVT 13a that changes the phase of the intake camshaft relative to the phase (rotational phase) of the crankshaft 7. The intake SVT 13a changes the opening and closing timings of the intake valve 11 by the same amount while maintaining the lift amount and opening duration of the intake valve 11 at a constant level. The exhaust valve train mechanism 14 also incorporates an exhaust SVT 14a that changes the phase of the exhaust camshaft relative to the phase (rotational phase) of the crankshaft 7. The exhaust SVT 14a changes the opening and closing timings of the exhaust valve 12 by the same amount while maintaining the lift amount and opening duration of the exhaust valve 12 at a constant level. The cylinder head 4 is fitted with an intake cam angle sensor SN2 for detecting the rotation angle of the intake cam shaft.

[0034] The intake passage 30 is connected to the engine body 1 in a manner that communicates with the intake ports 9 of each cylinder 2. The intake passage 30 is provided with a throttle valve 31 that can open and close its flow path to adjust the amount of intake air flowing into the cylinders 2 (combustion chambers 6) through the intake passage 30.

[0035] The exhaust passage 40 is connected to the engine body 1 in a manner that communicates with the exhaust ports 10 of each cylinder 2. Although not shown in the illustration, the exhaust passage 40 is equipped with a purification device and the like for purifying the exhaust gas passing through it.

[0036] (Control system) Figure 3 is a block diagram showing the control system of vehicle 100. The controller 200 shown in Figure 3 is a microprocessor for comprehensively controlling vehicle 100, and is composed of a well-known CPU, ROM, RAM, etc.

[0037] The controller 200 receives sequential detection signals from various sensors mounted on the vehicle 100, including the sensors SN1 and SN2 mentioned above. The vehicle 100 is also equipped with an accelerator position sensor SN3 that detects the accelerator position, which is the amount the accelerator pedal is pressed, and the detection signal from the accelerator position sensor SN3 is also input to the controller 200. The controller 200 performs various judgments and calculations based on the information input from each sensor SN1 to SN3, etc. For example, the controller 200 determines which cylinder is in which stroke based on the detection signal from the crank angle sensor SN1 and the detection signal from the intake cam angle sensor SN2. The controller 200 also calculates the required acceleration, which is the acceleration required for the vehicle 100, based on the accelerator position detected by the accelerator position sensor SN3. The controller 200 then outputs control signals to various parts of the engine E, such as the intake SVT 13a, injector 15, and throttle valve 31, based on the calculation results, and also outputs control signals to various parts of the vehicle 100, such as the clutch 102. For example, the controller 200 controls the injector 15 so that fuel is injected into each cylinder 2 during its compression stroke.

[0038] The controller 200 operates functionally to include a stop control unit 201 and a start control unit 202 when a predetermined program is executed.

[0039] (Stop control unit) When the engine stop condition, which is set in advance as the condition for stopping engine E, is met, the stop control unit 201 performs the following control.

[0040] When the engine stop condition is met, the stop control unit 201 performs a fuel cut, stopping fuel injection from the injector 15 to each cylinder 2. As the fuel cut is performed, the engine speed decreases. After the fuel cut is performed, the stop control unit 201 closes the throttle valve 31 towards full closure. The stop control unit 201 also drives the intake SVT 13a to set the intake valve closing timing to the most retarded timing (the most retarded timing among the possible timings for intake valve closing). Specifically, after fully closing the throttle valve 31, the stop control unit 201 waits for the engine speed to decrease to a predetermined speed, and then retards the intake valve closing timing towards the most retarded timing. Then, when the engine E stops, the stop control unit 201 disengages the clutch 102.

[0041] Furthermore, after the stop control unit 201 begins to retard the intake valve closing timing to the most delayed timing, it adjusts the opening degree of the throttle valve 31 in order to bring the position of the piston 5 of each cylinder 2 within a predetermined target stop range.

[0042] Hereafter, the position of piston 5 of cylinder 2 will be referred to as the position of cylinder 2. Furthermore, when engine E is stopped, more specifically when the engine speed is 0 and engine E is completely stopped, the stroke in which cylinder 2 (piston 5) is in the latter half of the compression stroke, that is, within the range of 90°CA from top dead center (TDC) to just before top dead center (BTDC), is called the stop-time compression stroke cylinder. The cylinder whose combustion order follows the stop-time compression stroke cylinder is called the stop-time compression transition cylinder, and the cylinder whose combustion order follows the stop-time compression stroke cylinder is called the stop-time expansion cylinder.

[0043] The above target stopping range is set to a range where the position of the compression transition cylinder at stopping is in the latter half of the intake stroke or the first half of the compression stroke. In this embodiment, the above target stopping range is set as shown in Figure 4. Figure 4 is a diagram showing the stopping positions of the compression stroke cylinder at stopping, the compression transition cylinder at stopping, and the expansion stroke cylinder at stopping, corresponding to the target stopping range. In Figure 4, the uppermost point of the circle is defined as top dead center (TDC) and the lowermost point as bottom dead center (BDC), and the positions of each cylinder 2 (the position of the piston 5 of each cylinder 2) are shown such that the piston 5 position becomes retarded as the clockwise direction progresses. As shown in Figure 4, the above target stopping range is set to the range A1 from 75°CA before compression top dead center (position P1 in Figure 4) to 40°CA before compression top dead center (position P2 in Figure 4), in terms of the position of the compression stroke cylinder at stopping. Accordingly, in this embodiment, the stop control unit 201 adjusts the opening degree of the throttle valve 31 so that when the engine is stopped, the position of the compression stroke cylinder is within the range A1 from 75°CA before top dead center to 40°CA before top dead center, the position of the compression transition cylinder when the engine is stopped is within the range A2 from 15°CA before bottom dead center (position P3 in Figure 4) to 20°CA after bottom dead center (position P4 in Figure 4), and the position of the expansion stroke cylinder when the engine is stopped is within the range A3 from 45°CA after top dead center (position P5 in Figure 4) to 80°CA after top dead center (position P6 in Figure 4).

[0044] With the control described above, when engine E is started, the cylinder in the compression stroke at stop is the first to reach top dead center (TDC). That is, the piston 5 of the cylinder in the compression stroke at stop is the first to pass through TDC. Then, each cylinder reaches TDC in the order of combustion. Hereafter, the cylinder that reaches TDC the nth time after engine E starts rotating when engine E is started will be called the ○th compression cylinder. For example, the cylinder in the compression stroke at stop will be called the 1st compression cylinder, and the cylinder that reaches TDC next, the cylinder transitioning to compression at stop, will be called the 2nd compression cylinder.

[0045] (Startup control unit) The start control unit 202 performs control to start the engine E when the preset engine start conditions are met while the motor M is running, the engine E is stopped, and the clutch 102 is disengaged. Hereinafter, the state in which the motor M is running, the engine E is stopped, and the clutch 102 is disengaged will be referred to as the motor-only running state. The control procedure performed by the controller 200 (mainly the start control unit 202) when the engine start conditions are met in the motor-only running state will be explained using the flowchart in Figure 5.

[0046] First, the start control unit 202 determines whether the engine start condition has been met while the motor is running on its own (step S1). If this determination is NO and the motor is not running on its own, or if the engine start condition has not been met, the start control unit 202 repeats step S1 without performing the following control.

[0047] On the other hand, if the determination in step S1 is YES and the engine starting condition is met with the motor running alone, the starting control unit 202 determines whether the requested output, which is the required value for the total output of the engine E and motor M that are the drive sources of the vehicle 100, is greater than a predetermined determination output (step S2). Here, the requested output is greater when the vehicle 100 is accelerating and the required acceleration for the vehicle 100 is high. Based on this, the starting control unit 202 makes the determination in step S2 based on the accelerator opening detected by the accelerator opening sensor SN3. Specifically, the starting control unit 202 determines that the requested output is greater than the determination output if the accelerator opening is greater than a predetermined value, or if the rate of increase of the accelerator opening is greater than a predetermined value. The above values ​​used for the determination are set in advance and stored in the starting control unit 202.

[0048] If the determination in step S2 is YES and the requested output is greater than the determination output, that is, if the requested acceleration for the vehicle 100 is high, the start control unit 202 performs steps S21 to S26. This control will be described later.

[0049] On the other hand, if the determination in step S2 is NO and the requested output is less than or equal to the determination output, that is, if the requested acceleration for the vehicle 100 is low, the start control unit 202 performs steps S3 to S11.

[0050] First, the starting control unit 202 determines whether the stopping position of cylinder 2 is advanced beyond a preset determination position (step S3). The stopping position of cylinder 2 used for the determination is the current position of cylinder 2, that is, when the engine E is stopped. The determination position is preset and stored.

[0051] Specifically, the determination position is the position shown by the solid line in Figure 4, which is the position where the compression transition cylinder at stop (the position of the piston 5 of the compression transition cylinder at stop) is at intake bottom dead center (BDC). In this embodiment, as described above, the stop control unit 201 controls the position of the compression transition cylinder at stop when the engine E is stopped to a position within the range A2 from 15°CA before intake bottom dead center (position P3 in Figure 4) to 20°CA after intake bottom dead center (position P4 in Figure 4). Thus, in step S3, it is determined whether or not the position of the compression transition cylinder at stop is within the range from intake bottom dead center (BDC) to 15°CA before intake bottom dead center (position P3 in Figure 4).

[0052] If the determination in step S3 is NO and the stopping position of cylinder 2 is at the determination position or a position retarded further than the determination position, the starting control unit 202 sets the target clutch torque, which is the target value of the clutch torque, to the base torque (step S4).

[0053] The clutch torque is the torque transmitted from the motor M to the engine E via the clutch 102. When the engine starting conditions are met while the motor is running alone, in step S6 described later, the starting control unit 202 starts engaging the clutch 102 and increases the torque transmission from the motor M to the engine E from zero. The target clutch torque is the target value for this torque increase control, and the starting control unit 202 controls the clutch 102 so that the clutch torque increases to the target clutch torque. Specifically, the starting control unit 202 controls the discharge pressure of the hydraulic pump of the clutch 102. The above basic torque is set in advance and stored in the starting control unit 202. The basic torque is set to a value smaller than the clutch torque achieved when the clutch 102 is fully engaged, that is, when 100% of the torque is transmitted between the motor M and the engine E. After step S4, the process proceeds to step S6.

[0054] On the other hand, if the determination in step S4 is YES and the stopping position of cylinder 2 is advanced beyond the determination position, the starting control unit 202 increases the target clutch torque relative to the basic torque (step S5). In other words, the starting control unit 202 sets the target clutch torque to a value greater than the basic torque. In this case, the starting control unit 202 sets the target clutch torque to a value greater than the basic torque and less than the clutch torque achieved when the clutch 102 is fully engaged.

[0055] Figure 6 is a graph showing the relationship between the stopping position of cylinder 2 and the target clutch torque in this embodiment. In this embodiment, the target clutch torque is increased in stages as the advance angle of the stopping position of cylinder 2 relative to the determination position increases. Specifically, if the stopping position of cylinder 2 is within the range from the determination position to the first position P11 which is further advanced, the target clutch torque is set to a first torque CO-1 which is greater than the basic torque. If the stopping position of cylinder 2 is within the range from the first position P11 to the second position P12 which is further advanced, the target clutch torque is set to a second torque CO-2 which is greater than the first torque CO-1. ​​If the stopping position of cylinder 2 is further advanced than the second position P12, that is, within the range from the second position P12 to the most advanced target stopping position, the target clutch torque is set to a third torque CO-3 which is greater than the second torque CO-2. Furthermore, the advance angle of the first position P11 relative to the determination position, the advance angle of the second position P12 relative to the first position P11, and the advance angle of the maximum advance position relative to the second position are all set to the same amount (crank angle). In addition, the values ​​of the first position P11, the second position P12, the maximum advance position, and each torque CO-1, CO-2, and CO-3 are pre-set and stored in the starting control unit 202.

[0056] Returning to Figure 5, in step S6, the starting control unit 202 starts engaging the clutch 102 (step S6). Specifically, the starting control unit 202 starts driving the hydraulic pump of the clutch 102. Once the clutch 102 is engaged, the engine E starts to rotate.

[0057] Here, the starting control unit 202 controls the clutch 102 (hydraulic pump) so that the clutch torque reaches the target clutch torque set in step S4 or step S5. Specifically, the starting control unit 202 controls the clutch torque as shown in Figure 7. Figure 7 is a schematic diagram showing the change in clutch torque with respect to the crank angle, where lines L0, L1, L2, and L3 show the change when the target clutch torque is the basic clutch torque, the first torque CO-1, the second torque CO-2, and the third torque CO-3, respectively. As shown in Figure 7, once the clutch torque reaches the target clutch torque, the starting control unit 202 controls the clutch 102 so that the target clutch torque is maintained. In addition, the target clutch torque can take on multiple values ​​depending on the stopping position of cylinder 2, but as shown in Figure 7, the starting control unit 202 controls the clutch 102 so that the rate of increase of the clutch torque is the same regardless of the value of the target clutch torque.

[0058] Returning to Figure 5, after step S6, the starting control unit 202 prohibits fuel injection into the first compression cylinder 2 (step S7), and then performs fuel injection into the second compression cylinder 2 (step S8). Specifically, the starting control unit 202 does not drive the injector 15 of the first compression cylinder, which is the cylinder in the compression stroke while stopped, and prohibits fuel injection into the cylinder in the compression stroke while stopped (during the first compression stroke of the cylinder in the compression stroke while stopped after the engine E starts rotating). On the other hand, the starting control unit 202 drives the injector 15 of the second compression cylinder, which is the cylinder in the compression transition while stopped, and causes the injector 15 to inject fuel into the cylinder in the compression transition while stopped (during the first compression stroke of the cylinder in the compression transition while stopped after the engine E starts rotating). The second compression cylinder 2, or the cylinder in the compression transition while stopped, corresponds to the "specific cylinder" of the present invention.

[0059] After step S8, the starting control unit 202 again prohibits fuel injection by the injector 15 (step S9). In other words, the starting control unit 202 prohibits fuel injection into cylinder 2 for the third compression.

[0060] Next, the starting control unit 202 determines whether the engine speed detected by the crank angle sensor SN1 has reached a predetermined threshold speed. The threshold speed is pre-set and stored in the starting control unit 202.

[0061] If the determination in step S10 is NO and the engine speed is below the determination speed, the starting control unit 202 returns to step S9 and continues to prohibit fuel injection by the injector 15. In other words, the starting control unit 202 also prohibits fuel injection into cylinder 2, which enters the compression stroke after the third compression stroke. On the other hand, if the determination in step S10 is YES and the engine speed becomes equal to or greater than the determination speed, the starting control unit 202 starts normal control (step S11) and terminates the control for starting the engine E. Specifically, the starting control unit 202 controls the injector 15 so that fuel is injected into all cylinders 2 during their respective compression strokes, and changes the injection amount based on the accelerator opening, etc. In other words, the starting control unit 202 waits for the engine speed to rise to the determination speed following the fuel injection into cylinder 2 for the second compression stroke, and then resumes fuel supply to all cylinders 2.

[0062] Thus, if the determination in step S2 is NO and the requested output is less than or equal to the determination output, fuel injection into cylinder 2 for the first compression is not performed, and fuel injection into cylinder 2 for the second compression is performed. In addition, fuel injection into cylinder 2 for at least the third compression is prohibited.

[0063] Furthermore, the period from when the clutch 102 is engaged (when step S6 is performed) until the engine speed reaches the determined speed (until the determination in step S10 is YES) corresponds to the "starting period" of the present invention. Also, the compression stroke of the second cylinder corresponds to the "initial part of the starting period" in the present invention, and the period from the compression stroke of the second cylinder onward within the starting period corresponds to the "later part of the starting period".

[0064] Returning to step S2, if the determination in step S2 is YES and the requested output is greater than the determination output, the starting control unit 202 sets the target clutch torque to the base torque, similar to step S4 (step S21). The starting control unit 202 also starts engaging the clutch 102, similar to step S6 (step S22). Consequently, the engine E starts rotating. Here, even if the requested output is greater than the determination output, the starting control unit 202 controls the clutch 102 (hydraulic pump) so that the clutch torque reaches the target clutch torque set in step S21, similar to the case where the requested output is less than or equal to the determination output, and controls the clutch 102 so that the clutch torque is maintained once it reaches the target clutch torque. In this embodiment, even if the requested output is greater than the determination output, the starting control unit 202 controls the clutch 102 so that the clutch torque increases at the same rate as when the requested output is less than or equal to the determination output.

[0065] Next, the starting control unit 202 prohibits fuel injection to cylinder 2 for the first compression, similar to step S7 (step S23), and performs fuel injection to cylinder 2 for the second compression, similar to step S8 (step S24).

[0066] On the other hand, when the requested output is greater than the determined output, unlike when the requested output is less than or equal to the determined output, the starting control unit 202 continues fuel injection even after injecting fuel into the second compression cylinder 2 (step S25). In other words, the starting control unit 202 injects fuel from the injector 15 into each cylinder 2 that enters the compression stroke from the second compression cylinder onward. The starting control unit 202 also determines whether the engine speed has reached or exceeded the determined speed (step S26), and continues fuel injection from the injector 15 until the engine speed reaches or exceeds the determined speed and this determination is YES.

[0067] After the engine speed exceeds the determined speed, even if the requested output is greater than the determined output, the start control unit 202 proceeds to step S11 and starts normal control, just as when the requested output is less than or equal to the determined output.

[0068] Thus, when the determination in step S2 is YES and the requested output is greater than the determination output, fuel injection into cylinder 2 for the first compression is not performed, while fuel injection into cylinder 2 for the second and subsequent compressions is performed.

[0069] (effect, etc.) Figures 8 and 9 schematically show the changes in each parameter when the engine starting condition is met in the motor-driven state in the vehicle 100 according to the above embodiment. The horizontal axis in Figures 8 and 9 is the crank angle. Figures 8 and 9 show graphs of success or failure of the engine starting condition, clutch torque, fuel injection amount (amount of fuel injected from injector 15), and rotational speed, from top to bottom. In the rotational speed graph, the solid line is the engine speed (rotational speed of engine E), and the dashed line is the motor speed (rotational speed of motor M). Figure 8 shows the case when the requested output is greater than the judgment output, and Figure 9 shows the case when the requested output is less than or equal to the judgment output. Figures 8 and 9 also show an example in which the amount of fuel injected into cylinder 2 is reduced compared to before the start of normal control when normal control is started.

[0070] In the example shown in Figure 8, the engine starting condition is met at timing t1 while the motor is running alone. As described above, when the engine starting condition is met while the motor is running alone, the clutch 102 begins to engage. Consequently, the clutch torque begins to increase at timing t1. Then, some time after timing t1, the engine speed begins to rise and the motor speed begins to decrease.

[0071] As described above, when the engine starting conditions are met while the motor is driven alone, fuel is injected from the injector 15 into the second compression cylinder. Here, the second compression cylinder is the cylinder transitioning from compression while stationary, and the piston 5 of this cylinder is located near the intake bottom dead center when the engine E starts rotating. Therefore, the fuel and air in the cylinder transitioning from compression while stationary is sufficiently compressed by the time the piston 5 of that cylinder reaches the compression top dead center. As a result, the fuel-air mixture burns in the cylinder transitioning from compression while stationary, generating combustion energy. This combustion energy imparts rotational force to the engine E. Therefore, the rate at which the engine speed increases increases from around timing t2, when the piston 5 of the cylinder transitioning from compression while stationary exceeds the compression top dead center. Also, since the time from when the engine E starts rotating until the second compression cylinder, the cylinder transitioning from compression while stationary, reaches the compression top dead center is relatively short, the rate at which the engine speed increases increases relatively early after the engine E starts rotating (timing t2).

[0072] Here, if the requested output is greater than the judgment output, fuel is injected from the injector 15 into the third compression cylinder, i.e., the intake stroke cylinder while stopped, and combustion energy is generated. Therefore, when the requested output is greater than the judgment output, the engine speed continues to rise at a high speed and rises to the judgment speed early. In the example in Figure 8, the engine speed rises to the judgment speed at timing t3.

[0073] Thus, in the vehicle 100 according to the above embodiment, when the requested output is greater than the determined output, fuel is continuously injected into each cylinder 2 from the second compression onward, thereby increasing the engine speed earlier. In the engine speed graph of Figure 8, the dashed line represents the engine speed when fuel injection is stopped until the engine speed reaches the determined speed. As is clear from the comparison with this dashed line, according to the vehicle 100 according to the above embodiment, when the requested output is greater than the determined output, fuel is continuously injected into each cylinder 2 from the second compression onward, thereby significantly shortening the time it takes for the engine speed to reach the determined speed, i.e., the engine E starting time.

[0074] However, as shown in Figure 8, if control is implemented to continuously inject fuel into each cylinder 2 from the second compression onward, the engine speed will rise significantly, exceeding the motor speed. In the example in Figure 8, around timing t3, the engine speed rises rapidly to a speed higher than the motor speed. As a result, a torque shock occurs. In other words, the engine E and motor M vibrate considerably, and the occupants of the vehicle 100 may feel a shock.

[0075] However, the above control is implemented when the requested output is greater than the determined output and the requested acceleration for the vehicle 100 is high, that is, while the vehicle 100 is accelerating. Therefore, the impact of the above torque shock on the occupants is kept to a minimum.

[0076] On the other hand, if the above control is implemented when the requested output is less than or equal to the judgment output and the requested acceleration for the vehicle 100 is low, that is, when the vehicle 100 is not accelerating, the impact of torque shock on the occupants will be greater.

[0077] In contrast, in the vehicle 100 according to the above embodiment, when the requested output is less than or equal to the determination output, fuel injection is performed into the second compression cylinder 2, while fuel injection into cylinder 2 from the second compression onward is prohibited until the engine speed reaches or exceeds the determination speed. In other words, fuel injection into cylinder 2 is performed only in the early part of the starting period, from when the clutch 102 is engaged until the engine speed reaches the determination speed, and fuel injection into cylinder 2 is stopped in the later part of the starting period. Therefore, the engine speed can be increased to the determination speed relatively quickly while suppressing the occurrence of torque shock.

[0078] Specifically, in the rotational speed graph in Figure 9, the solid line shows the engine speed when fuel injection to cylinder 2 during the third compression stroke is prohibited, while the dashed line shows the engine speed shown by the solid line in Figure 8, when fuel injection is performed to cylinder 2 during the third compression stroke. As is clear from comparing the solid and dashed lines, even when the requested output is less than or equal to the judgment output, fuel is injected into the cylinder during the second compression stroke, i.e., the cylinder transitioning to compression during cessation, causing the rate of increase in engine speed to accelerate from around timing t2, when the piston 5 of that cylinder exceeds top dead center. However, when the requested output is less than or equal to the judgment output, fuel injection is not performed into the cylinder during the third compression stroke, i.e., the cylinder undergoing intake stroke during cessation, causing the rate of increase in engine speed to slow down temporarily. In other words, after timing t2, the rate of increase in engine speed increases temporarily, but then slows down (at timing t11 in the example of Figure 9). Therefore, when the requested output is less than or equal to the judgment output, the engine speed does not exceed the rotational speed of the motor M, and the occurrence of the above-mentioned torque shock can be suppressed. In the example shown in Figure 9, the engine speed exceeds the specified speed when the fourth cylinder is in the compression stroke, and consequently, fuel injection is performed on the fourth cylinder (cylinder 2).

[0079] As described above, in the engine E starting control device according to the above embodiment, when the engine starting conditions are met while the motor is running alone, the clutch 102 is engaged. If the requested output is less than or equal to the determination output, during the period from when the clutch 102 is engaged until the engine speed reaches the determination speed (starting period), fuel is injected only into the second compression cylinder 2, and fuel injection to the third compression and subsequent cylinders is stopped.

[0080] Therefore, according to the above embodiment, when the engine speed is sufficiently smaller than the motor speed of M, the torque transmitted from the motor speed of M and the combustion energy generated in the second compression cylinder can increase the engine speed quickly. Furthermore, when the engine speed has increased to a certain extent and approaches the motor speed of M, the increase in engine speed can be suppressed to prevent the engine speed from exceeding the motor speed. As a result, the engine start-up time, which is the time it takes for the engine speed to reach the predetermined speed, can be kept short, while the occurrence of torque shock that occurs when the engine speed exceeds the motor speed can be suppressed.

[0081] Furthermore, in the above embodiment, when the requested output is less than or equal to the judgment output, during the starting period until the engine E reaches the judgment rotational speed, fuel is injected only into cylinder 2, which is the second compression cylinder, and the position of the piston 5 at the time the engine stops is in the latter half of the intake stroke or the first half of the compression stroke. Fuel injection is also performed only during the first compression stroke of this second compression. As a result, the fuel-air mixture can be reliably burned to obtain combustion energy, and combustion energy can be obtained at a relatively early timing after the engine E starts rotating. Consequently, the rate of increase in engine speed can be reliably increased at a timing when the engine speed is sufficiently small compared to the rotational speed of the motor M.

[0082] Furthermore, in the above embodiment, it is determined whether the stopping position of cylinder 2, including the stopping position of the second compression cylinder, is advanced beyond the determination position (step S3). If the stopping position of cylinder 2, including the stopping position of the second compression cylinder 2, is advanced beyond the determination position, the target clutch torque is set to a larger value than when the stopping position of cylinder 2, including the stopping position of the second compression cylinder 2, is at the determination position or retarded beyond the determination position, thereby increasing the torque transmitted from the motor to the engine during the starting period. In other words, when the crank angle until the second compression cylinder 2 (piston 5) reaches top dead center and the crank period until combustion energy is generated in that cylinder 2 is long, the increase in engine speed due to the torque transmitted from the motor M to the engine E is promoted.

[0083] This makes it possible to suppress the increase in the time it takes for the engine speed to reach the predetermined speed, which occurs when the time it takes to obtain combustion energy increases. In other words, it is possible to suppress the increase in engine starting time. Furthermore, when the stopping position of cylinder 2, including the stopping position of cylinder 2 in the second compression, is the predetermined position or a position retarded further than the predetermined position, that is, when the crank period until combustion energy is obtained is short, the torque transmitted from motor M to engine E can be kept low by setting the target clutch torque to a small value.

[0084] Furthermore, in the above embodiment, when the requested output is greater than the judgment output as the vehicle 100 accelerates, and the occupants are less likely to feel torque shock, fuel injection to cylinder 2 continues even after the third compression. In other words, fuel is supplied to cylinder 2 both in the early and late stages of the starting period. Therefore, the engine starting time can be shortened while minimizing the impact of the torque shock that occurs when the engine E starts on the user.

[0085] (modified version) In the above embodiment, we described a case where fuel is injected into cylinder 2 both in the early and late stages of the starting period when the requested output is greater than the determination output. However, fuel injection to cylinder 2 may also be stopped in the later stages of the starting period when the requested output is greater than the determination output.

[0086] In the above embodiment, a case was described in which the target clutch torque is set to the basic clutch torque even when the requested output is greater than the judgment output. However, when the requested output is greater than the judgment output, the target engine torque may be set to a larger value than when it is smaller. Furthermore, when the requested output is greater than the judgment output, the rate at which the engine torque is increased to the target engine torque may be increased compared to when it is smaller.

[0087] In the above embodiment, we described a case where the target clutch torque is increased in stages as the advance angle of the stopping position of cylinder 2 relative to the determination position increases, when the stopping position of cylinder 2 is advanced beyond the determination position. However, the relationship between the advance angle and the target clutch torque is not limited to this. For example, the target clutch torque may be set to a constant torque regardless of the advance angle.

[0088] Furthermore, the configuration that changes the target clutch torque depending on whether the stopping position of cylinder 2 is advanced beyond the determination position may be omitted. In other words, the target clutch torque may be set to a constant value regardless of the stopping position of cylinder 2.

[0089] Furthermore, although the above embodiment described the case where the engine is an inline 6-cylinder engine, the number of cylinders and the arrangement of cylinders in the engine are not limited to this. [Explanation of Symbols]

[0090] 15. Injector (fuel supply means) 102 Clutch 202 Startup Control Unit E-engine M Motor

Claims

1. A device for controlling the starting of an engine having a cylinder in which a piston is housed so as to be able to reciprocate, and a fuel supply means for supplying fuel to the cylinder, Motor and, A clutch that connects the engine and the motor in a way that allows them to be connected and disconnected, The system includes a starting control unit that initiates engagement of the clutch when predetermined engine starting conditions are met while the motor is running and the clutch is disengaged, During the starting period from the start of clutch engagement until the engine speed reaches a predetermined determination speed, the starting control unit controls the fuel supply means such that fuel is supplied to the cylinder only in the early part of the starting period, and fuel supply to the cylinder is stopped in the later part of the starting period. An engine starting control device characterized in that the initial part of the starting period is the compression stroke of the second cylinder or earlier within the starting period, and the later part of the starting period is a period later than the initial part within the starting period.

2. In the engine starting control device according to claim 1, The engine has a plurality of the cylinders, An engine starting control device characterized in that the starting control unit controls the fuel supply means so that during the starting period, fuel is supplied only to a specific cylinder in which the piston is stopped at a position in the latter half of the intake stroke or the first half of the compression stroke, and such fuel supply is performed during the first compression stroke of the specific cylinder.

3. In the engine starting control device according to claim 2, The engine has six of the aforementioned cylinders, An engine starting control device characterized in that the aforementioned specific cylinder is the cylinder that reaches top dead center second during the starting period.

4. In the engine starting control device according to claim 3, The engine starting control device is characterized in that the starting control unit controls the clutch such that when the stopping position of the piston of the particular cylinder is advanced compared to a predetermined determination position, the torque transmitted from the motor to the engine during the starting period is greater than when the stopping position is retarded.

5. In the engine starting control device according to any one of claims 1 to 4, The engine starting control device is characterized in that, when the required value of the combined output of the engine and the motor is higher than a predetermined value, the fuel supply means is controlled so that fuel is supplied to the cylinders both in the early and late stages of the starting period.

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