JP2009208562A - Engine start control device for hybrid vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an influence on an output due to the torque change of a second clutch, and to achieve shock reduction even when engine start shock reduction is not expected due to the slip of the second clutch. <P>SOLUTION: A transmission torque capacity tTc1 of a first clutch is decreased by a prescribed gradient ΔTca from a clanking torque value at t3 when it is decided that an engine revolving speed Ne approaches a motor/generator revolving speed Nm in a prescribed range by the complete explosion of the engine, and tTc1 is set to 0 at t4 when Ne=Nm, and tTc1 is increased by prescribed gradient ΔTcb at t5 when Ne≥Nm+ΔN2, and tTc1 is set to a value by which the fastening of the first clutch is compensated at t6 when Ne=Nm again. In accordance with the decrease of the tTc1 at t3 to t6, engine start shock is reduced by the slip of the first clutch even when engine start shock reduction is not expected due to the slip of a second clutch. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an engine start control technique for a hybrid vehicle that includes an engine and a motor / generator as a power source and can travel using power from at least one of the engine and the motor / generator.

  Conventionally, various types of hybrid drive apparatuses used in the hybrid vehicle as described above have been proposed. As one of them, the one described in Patent Document 1 is known.

This hybrid drive system has an engine and a motor / generator in tandem as power sources,
The engine and motor / generator can be connected by the first clutch,
The motor / generator and drive wheel can be connected / disconnected by the second clutch,
As the second clutch, a shift friction element in the automatic transmission interposed between the motor / generator and the drive wheel is used.

A hybrid vehicle equipped with such a drive device can perform electric travel only by a motor / generator when releasing the first clutch and engaging the second clutch (EV mode),
When engaging both the first and second clutches, use only the power from the engine, or use both engine power and power from the motor / generator, that is, by power from both the engine and motor / generator. Hybrid driving is possible (HEV mode).

In such a hybrid vehicle, the electric driving (EV) mode is used for small and low loads and low vehicle speeds, including when starting, because of the ease of delicate driving force control, and high output is required at high loads and high vehicle speeds. / Hybrid driving (HEV) mode is used because the driving power is insufficient with only the power from the generator.
Therefore, if the accelerator pedal is depressed or the vehicle speed increases and the vehicle is in a heavy load / high vehicle speed driving state while driving in the electric vehicle (EV) mode with a small, low load and low vehicle speed, the hybrid vehicle (HEV) mode is entered. The engine needs to be started for mode switching.

  In the hybrid vehicle of the above type, the starter motor for starting the engine is not provided, and when starting the engine when switching from EV to HEV mode, the first clutch that has been released in the EV mode is engaged, Usually, the engine is cranked by the power of the motor / generator, and the engine is rotated up to a speed at which the engine can be started.

By the way, when the engine is started, a large torque fluctuation occurs, and this torque fluctuation is transmitted to the drive wheels to cause an engine start shock, which gives the passenger a sense of incongruity.
As a technique for reducing such engine start shock, Patent Document 1 discloses that when the torque fluctuation that causes engine start shock occurs when the torque transmission capacity of the second clutch is reduced at the time of engine start, the second clutch slips. Techniques have been proposed for absorbing torque fluctuations so that they do not travel toward the drive wheels, thereby reducing engine start shocks.
JP 2005-221073 A

  However, as described in Patent Documents 1 and 2, regardless of whether the shift friction element in the automatic transmission is diverted as the second clutch or a dedicated second clutch is additionally installed in the front stage or the rear stage of the automatic transmission, When the second clutch is slip-controlled to reduce the engine start shock, the second clutch needs to be slip-controlled to reduce the engine start shock while transmitting the required driving force of the vehicle to the drive wheels. Mitigating engine start-up shocks by slip control with only two clutches is a difficult task.

Moreover, the second clutch has the highest priority to have a transmission torque capacity that can transmit the required driving force of the vehicle to the drive wheels, and the transmission torque capacity at the time of slip control of the second clutch determined in relation to this is the engine start Under operating conditions that do not become small enough to reduce shock,
The slip of the second clutch due to the input torque fluctuation of the automatic transmission that occurs when the engine starts is unlikely to occur, and most of the torque fluctuation is directed to the drive wheels as the transmission output torque. Can not be reduced.

  In the present invention, even when the transmission torque capacity at the time of slip control of the second clutch for reducing the engine start shock is not reduced to the extent that the engine start shock can be reduced, the engine start torque fluctuation is the transmission output torque. The engine start control of the hybrid vehicle which does not go to the driving wheel is proposed to solve the above-mentioned problems.

For this purpose, the engine start control device for a hybrid vehicle according to the present invention is configured as described in claim 1.
First of all, to explain the prerequisite hybrid vehicle,
Provide the engine and motor / generator in tandem as a power source,
The engine and motor / generator can be connected by the first clutch,
The motor / generator and drive wheel can be connected by the second clutch,
When starting the engine in a state where the first clutch is released and the second clutch is engaged to perform electric traveling only by the motor / generator, the transmission torque capacity of the second clutch is reduced and the first clutch is engaged, The engine is started by cranking the engine by the driving torque of the motor / generator.

The engine start control device for a hybrid vehicle according to the present invention is such a hybrid vehicle,
The transmission torque capacity of the first clutch is reduced when it is determined that the engine speed approaches a predetermined range with respect to the motor / generator speed by the engine start described above.

According to the engine start control device of the hybrid vehicle according to the present invention described above,
In order to reduce the transmission torque capacity of the first clutch from the time when it is determined that the engine speed approaches a predetermined range with respect to the motor / generator speed when the engine is started,
Even in the driving state where the transmission torque capacity at the time of slip control of the second clutch for reducing the engine start shock does not become small enough to reduce the engine start shock,
As described above, the first clutch whose transmission torque capacity is reduced can absorb the torque fluctuation at the time of engine start due to the slip and reduce the engine start shock.

Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.
FIG. 1 shows a power train of a front engine / rear wheel drive type hybrid vehicle including a hybrid drive device incorporating an engine start control device according to an embodiment of the present invention, together with its control system. Is an automatic transmission, and 3 is a motor / generator.
In the power train of the hybrid vehicle shown in FIG. 1, the automatic transmission 2 is arranged in tandem at the rear of the engine 1 in the longitudinal direction of the vehicle in the same manner as a normal rear wheel drive vehicle. A motor / generator 3 is provided coupled to a shaft 5 that transmits the rotation to the input shaft 4 of the automatic transmission 2.

The motor / generator 3 includes an annular stator 3a fixed in a housing and a rotor 3b arranged concentrically with a predetermined air gap in the stator 3a. Acting as an electric motor) or acting as a generator (generator), it is arranged between the engine 1 and the automatic transmission 2.
The motor / generator 3 passes through the shaft 5 and is attached to the center of the rotor 3b, and uses the shaft 5 as a motor / generator shaft.

The first clutch 6 is inserted between the motor / generator 3 and the engine 1, more specifically, between the motor / generator shaft 5 and the engine crankshaft 1a, and the engine 1 and the motor / generator 3 are connected by the first clutch 6. Combine in a detachable manner.
Here, the first clutch 6 is assumed to be capable of continuously changing the transmission torque capacity. For example, the first clutch 6 is a wet type engine that can change the transmission torque capacity by continuously controlling the clutch hydraulic oil flow rate and the clutch hydraulic pressure with a proportional solenoid. It consists of a plate clutch.

The motor / generator 3 and the automatic transmission 2 are directly connected to each other by the direct connection of the motor / generator shaft 5 and the transmission input shaft 4.
The automatic transmission 2 is similar to the well-known planetary gear type automatic transmission in its transmission mechanism, but the torque converter is excluded from this, and the motor / generator 3 is directly connected to the transmission input shaft 4 instead. It shall be combined.

The automatic transmission 2 will be briefly described below.
The automatic transmission 2 includes an output shaft 7 arranged in a coaxial butt relationship with the input shaft 4, and the front planetary gear set Gf and the center planetary gear are sequentially placed on the input / output shafts 4 and 7 from the engine 1 (motor / generator 3) side. A set Gm and a rear planetary gear set Gr are provided, and these are the main components of the planetary gear transmission mechanism in the automatic transmission 2.

The front planetary gear set Gf closest to the engine 1 (motor / generator 3) is a simple planetary gear comprising a front sun gear Sf, a front ring gear Rf, a front pinion Pf meshing with the front sun gear Sf, and a front carrier Cf rotatably supporting the front pinion. A gear set,
Next, the center planetary gear set Gm close to the engine 1 (motor / generator 3) includes a center sun gear Sm, a center ring gear Rm, a center pinion Pm meshing with the center sun gear Sm, and a center carrier Cm that rotatably supports the center pinion. A planetary gear set,
The rear planetary gear set Gr farthest from the engine 1 (motor / generator 3) is a simple planetary gear set comprising a rear sun gear Sr, a rear ring gear Rr, a rear pinion Pr meshing with the rear sun gear Sr, and a rear carrier Cr that rotatably supports the rear pinion. To do.

  Front friction Fr / B, input clutch I / C, high-and-low reverse clutch H & LR / C, direct clutch D / C, reverse, as the transmission friction elements that determine the transmission path (speed stage) of the planetary gear transmission mechanism A brake R / B and a forward brake FWD / B are provided, and these are correlated with the above-described components of the planetary gear group Gf, Gm, Gr as follows to constitute a planetary gear transmission mechanism of the automatic transmission 2.

The front ring gear Rf is coupled to the input shaft 4, and the center ring gear Rm can be appropriately coupled to the input shaft 4 by the input clutch I / C.
The front sun gear Sf can be appropriately fixed to the transmission case 2a by the front brake Fr / B.
Front carrier Cf and rear ring gear Rr are coupled to each other, and center ring gear Rm and rear carrier Cr are coupled to each other.
The center carrier Cm is coupled to the output shaft 7, and the center sun gear Sm and the rear sun gear Sr can be coupled to each other by a high and low reverse clutch H & LR / C.

The rear sun gear Sr and the rear carrier Cr can be coupled by the direct clutch D / C, and the rear carrier Cr can be appropriately fixed to the transmission case 2a by the reverse brake R / B.
Further, the center sun gear Sm can be appropriately fixed to the transmission case 2a by the forward brake FWD / B.

  The power transmission train of the above planetary gear transmission mechanism is a selective transmission shown by the circles in Fig. 2 for six shift friction elements Fr / B, I / C, H & LR / C, D / C, R / B, and FWD / B. By engaging, it is possible to obtain the forward shift speed and the reverse shift speed of the first forward speed, the second forward speed, the third forward speed, the fourth forward speed, and the fifth forward speed.

A hybrid vehicle having the power train of FIG. 1 composed of the engine 1, the motor / generator 3 and the automatic transmission 2 described above is provided between the motor / generator 3 and a drive wheel coupled to the transmission output shaft 7. A second clutch is required that is detachably coupled,
In the present embodiment, among the six shift friction elements Fr / B, I / C, H & LR / C, D / C, R / B, and FWD / B existing in the automatic transmission 2, the forward shift is performed. Shift friction element for selecting gear (H & LR / C for forward 1st speed, 3rd speed, 4th speed, 5th speed, D / C for forward 2nd speed), or shift friction element for selecting reverse gear ( H & LR / C) is used as the second clutch.

  By the way, the existing shift friction element (H & LR / C, D / C) for selecting the forward shift stage or the shift friction element (H & LR / C) for selecting the reverse shift stage is originally present in the automatic transmission 2 used as the second clutch. As with the first clutch 6, the transmission torque capacity can be changed continuously.

The functions for each power train selection mode described above with reference to FIG. 1 will be described below.
In the power train of FIG. 1, when the electric travel (EV) mode used at low load and low vehicle speed including when starting from a stopped state is required, the first clutch 6 is released and the second clutch H & LR / C (D / C) is fastened and the automatic transmission 2 is in the power transmission state.

When the motor / generator 3 is driven in this state, only the output rotation from the motor / generator 3 reaches the transmission input shaft 4, and the automatic transmission 2 changes the rotation to the input shaft 4 to the selected shift. The speed is changed according to the speed and output from the transmission output shaft 7.
Then, the rotation from the transmission output shaft 4 reaches the left and right drive wheels through a differential gear device (not shown), and the vehicle can be electrically driven (EV traveling) only by the motor / generator 3. (EV mode)

When the hybrid driving mode (HEV mode) used when driving at high speeds, during heavy loads, or when the battery power that can be taken out is low is required, the first clutch 6 and the second clutch H & LR / C (D / C) together and put automatic transmission 2 in the power transmission state.
In this state, the output rotation from the engine 1 or both the output rotation from the engine 1 and the output rotation from the motor / generator 3 reach the transmission input shaft 4, and the automatic transmission 2 is connected to the input shaft 4 Is rotated according to the currently selected shift speed and output from the transmission output shaft 7.
Thereafter, the rotation from the transmission output shaft 7 passes through a differential gear device (not shown) to reach the left and right drive wheels, and the vehicle can be hybrid-run by both the engine 1 and the motor / generator 3. (HEV mode)

  When the engine 1 is operated at the optimum fuel efficiency during such HEV traveling, if the energy becomes surplus, the surplus energy is converted into electric power by operating the motor / generator 3 as a generator by this surplus energy, and this generated power is converted into electric power. By accumulating power to be used for driving the motor of the motor / generator 3, the fuel consumption of the engine 1 can be improved.

  In the above description, the automatic transmission 2 is described as a stepped automatic transmission. However, the automatic transmission 2 is not limited to a stepped type, and may be a continuously variable transmission. In the case of a step transmission, the forward selection clutch and the reverse selection brake in the forward / reverse switching mechanism constitute the second clutch.

Hereinafter, the control system of the engine 1, the motor / generator 3, the first clutch 6, and the second clutch H & LR / C (D / C) in the transmission 2 constituting the power train of the hybrid vehicle will be outlined based on FIG. explain.
This control system includes an integrated controller 11 that integrally controls the operating point of the power train. The operating point of the power train includes the target engine torque tTe, the target motor / generator torque tTm, and the target transmission torque of the first clutch 6. It is defined by the capacity tTc1 and the target transmission torque capacity tTc2 of the second clutch H & LR / C (D / C).

In the integrated controller 11, in order to determine the operating point of the power train,
A signal from the engine rotation sensor 12 for detecting the rotation speed Ne of the engine 1,
A signal from the motor / generator rotation sensor 13 for detecting the rotation speed Nm of the motor / generator 3;
A signal from the input rotation sensor 14 for detecting the transmission input rotation speed Ni;
A signal from the output rotation sensor 15 for detecting the transmission output rotation speed No (vehicle speed),
A signal from the accelerator opening sensor 16 for detecting the accelerator pedal depression amount (accelerator opening APO);
A signal from a power storage state sensor 17 that detects a power storage state SOC (power that can be taken out) of a battery (not shown) that stores power for the motor / generator 3 is input.

  The integrated controller 11 is an operation mode in which the driving force of the vehicle desired by the driver can be realized from the accelerator opening APO, the battery storage state SOC, and the transmission output rotational speed No (vehicle speed) among the above input information ( EV mode, HEV mode) is selected, and target engine torque tTe, target motor / generator torque tTm, first clutch target transmission torque capacity tTc1, and second clutch target transmission torque capacity tTc2 are calculated.

  The target engine torque tTe is supplied to the engine controller 21. The engine controller 21 realizes the target engine torque tTe based on the engine speed Ne from the engine speed Ne detected by the sensor 12 and the target engine torque tTe. Therefore, the engine 1 is controlled so that the engine torque becomes the target engine torque tTe by the throttle opening control and the fuel injection amount control.

The target motor / generator torque tTm is supplied to the motor / generator controller 22, which converts the battery power into DC-AC by means of an inverter (not shown) and controls the motor under the control of the inverter. The motor / generator torque is supplied to the stator 3a of the generator 3 so that the motor / generator torque matches the target motor / generator torque tTm.
If the target motor / generator torque tTm is such that the motor / generator 3 requires a regenerative braking action, the motor / generator controller 22 is connected to the battery storage state SOC (power that can be taken out) detected by the sensor 17 via the inverter. ) To the motor / generator 3 so as to prevent the battery from being overcharged.
The electric power generated by the motor / generator 3 due to the regenerative braking action is AC-DC converted to charge the battery.

  The first clutch target transmission torque capacity tTc1 is supplied to the first clutch controller 23. The first clutch controller 23 includes the first clutch engagement pressure command value corresponding to the first clutch target transmission torque capacity tTc1, the first clutch 6 By controlling the engagement pressure of the first clutch 6 so that the actual engagement pressure of the first clutch 6 becomes the first clutch engagement pressure command value, the transmission torque capacity of the first clutch 3 is targeted Executes control to obtain the value tTc1.

  The second clutch target transmission torque capacity tTc2 is supplied to the transmission controller 24, which transmits the second clutch engagement pressure command value corresponding to the second clutch target transmission torque capacity tTc2 and the second clutch H & LR / C. The second clutch H & LR / C (D / C) is adjusted so that the actual engagement pressure Pc2 of the second clutch H & LR / C (D / C) becomes the second clutch engagement pressure command value by comparing with the actual engagement pressure of (D / C). C) The engagement pressure of the second clutch H & LR / C (D / C) is controlled to the target value tTc2 by controlling the engagement pressure.

  The transmission controller 24 basically sets the current driving state based on the planned shift map based on the transmission output rotation speed No (vehicle speed) detected by the sensor 15 and the accelerator opening APO detected by the sensor 16. A suitable gear position is obtained, and the transmission 2 is automatically shifted so that the suitable gear position is selected.

The above is an outline of the normal control executed by the control system of FIG.
In the present embodiment, the accelerator pedal is depressed during traveling in the electric traveling (EV) mode with the first clutch 6 released, the vehicle speed is increased, a heavy load / high vehicle speed driving state is reached, or the battery charge state SOC ( 1) The control system in FIG. 1 performs the engine start as follows according to the control program shown in FIG. 3 when the mode change to the hybrid running (HEV) mode is requested due to a decrease in the power that can be taken out To

As described above, the hybrid vehicle having the power train shown in FIG. 1 does not include the starter motor for starting the engine, and the engine is released in the EV mode when the engine is switched from EV to HEV mode. The first clutch 6 is engaged, the engine 1 is cranked by the power of the motor / generator 3, and the engine 1 is rotated to a rotational speed at which the engine 1 can be started.
Therefore, the engine start control in FIG. 3 is nothing but the transmission torque capacity control of the first clutch 6.

  On the other hand, during the engine start control based on FIG. 3, the transmission torque capacity of the second clutch H & LR / C (D / C) is reduced as described in Patent Document 1, and the automatic transmission 2 is controlled by the engine start control of FIG. When the engine start shock cannot be reduced by (the transmission torque capacity control of the first clutch 6), the engine start shock can be reduced by the slip of the second clutch H & LR / C (D / C).

Such transmission clutch capacity reduction control of the second clutch H & LR / C (D / C) will be supplemented based on FIG.
FIG. 4 is an operation time chart when an engine start request is generated when there is a command to switch from the EV mode to the HEV mode at an instant t1 due to the increase in the accelerator opening APO shown in the figure.
For the torque reduction control of the second clutch H & LR / C (D / C), the engine start request instant t1 is multiplied by the second clutch target transmission torque capacity tTc2, and the target driving torque Tin corresponding to the accelerator opening APO is multiplied by 0.7. Start with a drop in value.

  The target motor / generator torque tTm is set to increase the motor / generator rotational speed Nm as shown in the figure for engine start in synchronization with the transmission torque capacity decrease control of the second clutch H & LR / C (D / C) from the instant t1. Increased as shown.

In response to the decrease in the second clutch target transmission torque capacity tTc2 described above, the target transmission torque capacity tTc1 of the first clutch 6 is changed from 0 at the instant t2 when the second clutch H & LR / C (D / C) starts to slip. While increasing the cranking torque required for cranking the engine 1, the second clutch target transmission torque capacity tTc2 is increased to the cranking upper limit torque (tTm-tTc1).
By increasing the first clutch target transmission torque capacity tTc1 from 0 to the cranking torque at the instant t2, the engine 1 is cranked by the power from the motor / generator 3 as shown by the increase in the engine speed Nm,
During this time, the target motor / generator torque tTm is determined so as to feedback-control the motor / generator rotation speed Nm so as to become the target rotation speed tNm for engine cranking.

In step S11 in FIG. 3, it is determined whether or not the engine 1 is completely explosive due to this cranking and is in a state where it can be operated independently. It is determined whether or not the number Nm approaches a predetermined range.
When detecting whether the engine speed Ne approaches the predetermined range with respect to the speed Nm of the motor / generator 3, instead of performing the detection by the complete explosion determination of the engine 1 as described above, the engine 1 It goes without saying that the detection may be performed by the start determination of the fuel injection or the detection may be performed by the rapid increase determination of the engine speed Ne.

  Before it is determined in step S11 that the engine 1 has completely exploded (the engine speed Ne approaches the predetermined range with respect to the motor / generator speed Nm), the first clutch target transmission torque capacity tTc1 is determined in step S12. The cranking of engine 1 is continued by using the ranking torque.

  At the instant t3 in FIG. 4 where it is determined that the engine 1 has completely exploded in step S11 (the engine speed Ne approaches the predetermined range with respect to the motor / generator speed Nm), the control proceeds to step S13. Depending on whether or not the absolute value | Ne−Nm | of the rotational difference between the engine speed Ne and the motor / generator speed Nm is less than the minute set value ΔN1, the engine speed Ne and the motor / generator speed Nm It is checked whether or not the rotational difference has become substantially zero (whether or not the engine rotational speed Ne substantially matches the motor / generator rotational speed Nm).

In step S13, it is determined that the rotational difference between the engine speed Ne and the motor / generator speed Nm has become substantially zero (the engine speed Ne has substantially matched the motor / generator speed Nm). Prior to this, in step S14, the first clutch target transmission torque capacity tTc1 is gradually decreased at a predetermined time change gradient ΔTca.
As shown in FIG. 4, the decrease gradient ΔTca of the first clutch target transmission torque capacity tTc1 depends on the rotational difference (Ne−Nm) according to the rotational difference (Ne−Nm) between the engine rotational speed Ne and the motor / generator rotational speed Nm. It is determined that the first clutch target transmission torque capacity tTc1 becomes substantially zero at the instant t4 when Nm) becomes substantially zero.

When it is determined in step S13 that the rotational difference between the engine rotational speed Ne and the motor / generator rotational speed Nm has become substantially zero (the engine rotational speed Ne substantially coincides with the motor / generator rotational speed Nm) (in FIG. t4) This time, in step S15, the engine speed Ne is determined based on whether Ne ≧ Nm + ΔN2 using the second set speed ΔN2 for determining whether the engine speed Ne is equal to or higher than the motor / generator speed Nm. It is determined whether Ne is higher than the motor / generator rotational speed Nm by exceeding the second set rotational speed ΔN2.
While it is determined in step S15 that the engine speed Ne is not yet higher than the motor / generator speed Nm beyond the second set speed ΔN2, the first clutch target transmission torque capacity tTc1 is set to 0 in step S16. To do.

In step S15, after the instant t5 in FIG. 4 where it is determined that the engine speed Ne is higher than the motor / generator speed Nm beyond the second set speed ΔN2, the first clutch 6 does not slip in step S17. Then, it is checked whether or not it is in a synchronization completion state in which the forward / backward differential rotation (Ne−Nm) becomes zero.
FIG. 4 shows the first clutch target transmission torque capacity tTc1 in step S18 after the instant t5 in FIG. 4 and before the instant t6 in FIG. 4 in which it is determined that the first clutch 6 is synchronized in step S17. In this way, it is gradually increased at a predetermined time change gradient ΔTcb.

  After the instant t5 in FIG. 4 at which it is determined in step S17 that the first clutch 6 has been synchronized, in step S19, the first clutch target transmission torque capacity tTc1 is engaged with the accelerator opening APO equivalent engine torque as shown in FIG. The static torque value obtained by multiplying the safety factor for compensation is used.

According to the engine start control of the hybrid vehicle according to the above-described embodiment,
During engine start-up (cranking), the engine speed Ne approaches the motor / generator speed Nm within a predetermined range by determining whether the engine has completed an explosion, starting fuel injection from the engine, or determining whether the engine speed has suddenly increased. Then, from the time t3 determined (step S11), in order to reduce the transmission torque capacity tTc1 of the first clutch 6 (step S14),
In order to reduce the transmission torque capacity of the second clutch H & LR / C (D / C) with priority given to realizing the required driving force of the vehicle, the transmission torque capacity of the second clutch H & LR / C (D / C) If the transmission torque capacity of the second clutch H & LR / C (D / C) is not reduced sufficiently, the engine start shock cannot be reduced as intended,
Although the transmission torque capacity reduction of the second clutch H & LR / C (D / C) is sufficient, the degree of influence on the transmission output torque due to the clutch torque change of the second clutch H & LR / C (D / C) is small, Even when the transmission torque capacity of the second clutch H & LR / C (D / C) cannot be reduced as intended,
As described above, the first clutch 6 whose transmission torque capacity tTc1 is reduced can absorb the torque fluctuation at the time of engine start due to the slip and reduce the engine start shock.

In addition, the above determination that the engine speed Ne is close to the predetermined range with respect to the motor / generator speed Nm is made by the engine complete explosion determination, the engine fuel injection start determination, the engine speed rapid increase determination, etc. To do
The first clutch transmission torque capacity tTc1 can be lowered at the timing when the engine start torque fluctuation (engine start shock) is actually generated, and the above-described effects are remarkable. be able to.

Further, at the instant t4 when the rotational difference between the engine rotational speed Ne and the motor / generator rotational speed Nm becomes substantially zero (step S13), the transmission torque capacity tTc1 of the first clutch 6 is made substantially zero (step S16).
At the instant t4 when the rotation difference becomes substantially zero, the state in which the motor / generator 6 is cranking the engine 1 is switched to the state in which the engine 1 is operated at a higher speed than the motor / generator 6 by the self-sustaining operation. As a result, the direction of the torque is reversed to cause a stepwise torque change. This stepwise torque change can be absorbed by the slip of the first clutch 6 in which the transmission torque capacity tTc1 is substantially 0, and the stepwise torque change is thus achieved. Generation of shock due to torque change can be avoided.

Further, in order to gradually decrease the transmission torque capacity tTc1 of the first clutch 6 with a predetermined time change gradient ΔTca (step S14), the slip of the first clutch 6 suddenly increases due to the decrease of the transmission torque capacity tTc1. No shock.
It should be noted that when the difference in rotation ΔTca of the transmission torque capacity tTc1 of the first clutch 6 becomes substantially zero in accordance with the rotational difference between the engine rotational speed Ne and the motor / generator rotational speed Nm, the first clutch 6 Since the transmission torque capacity tTc1 is determined to be substantially zero,
At the instant t4 when the rotational difference between the engine speed Ne and the motor / generator speed Nm is substantially zero (step S13), the transmission torque capacity tTc1 of the first clutch 6 is substantially zero (step S16). Therefore, the above-described effects can be further ensured.

In order to increase the transmission torque capacity tTc1 of the first clutch 6 from the instant t5 when the engine speed Ne becomes higher than the motor / generator speed Nm beyond the set speed ΔN2 (step S15),
The transmission torque capacity tTc1 of the first clutch 6 is increased from substantially 0 after the stepwise torque change due to the reverse rotation of the torque direction described above. When the first clutch 6 is increased in the transmission torque capacity tTc1, The shock due to the stepwise torque change is not generated.

  Note that this effect can also be achieved by increasing the transmission torque capacity tTc1 of the first clutch 6 after the set time has elapsed since the engine speed Ne coincided with the motor / generator speed Nm. .

Incidentally, in order to gradually increase the above-described increase in the transmission torque capacity tTc1 of the first clutch 6 with a predetermined time change gradient ΔTcb (step S18),
It is possible to avoid the occurrence of shock accompanying the increase in the transmission torque capacity tTc1 of the first clutch 6.
In this sense, the increase gradient ΔTcb of the transmission torque capacity tTc1 of the first clutch 6 should be determined according to at least one of the required acceleration feeling, allowable acceleration shock, and accelerator opening APO equivalent torque. Needless to say.

By the way, it is preferable to reduce the engine torque while the first clutch transmission torque capacity tTc1 is increased, in order to ensure the engagement of the first clutch 6 whose transmission torque capacity tTc1 is increased.
For this purpose, the decrease in engine torque is indicated by a time-series change in engine torque tTe between instants t4 and t6 in FIG. 4, and the engine throttle opening TVO representing the engine load is set by a fixed amount α from the accelerator opening equivalent value. It is preferable to delay the engine ignition timing in the lowered state because it can realize a highly responsive engine torque reduction.

Such a decrease in engine torque ends the rotation synchronization instant t6 at which the input / output rotation difference of the first clutch 6 disappears, and the engine torque tTe is restored to the accelerator opening APO equivalent value as shown in FIG. 4 after this instant t6.
On the other hand, the transmission torque capacity tTc1 of the first clutch 6 is the static torque value obtained by multiplying the accelerator opening APO equivalent engine torque by the safety factor for clutch engagement compensation after this instant t6, and the first clutch 6 is completely Ensure that fastening is compensated.

In the above-described embodiment, the second clutch that is detachably coupled to the drive wheel coupled to the transmission output shaft 7 is provided in the automatic transmission 2 that is interposed between the motor / generator 3 and the drive wheel. The explanation of the case of using the shift friction element H & LR / C (D / C) among the shift friction elements Fr / B, I / C, H & LR / C, D / C, R / B, and FWD / B. But
Instead, the above-described idea of the present invention is similarly applied to a hybrid vehicle having a power train newly added by adding a second clutch before or after the automatic transmission 2 to achieve the intended purpose. Needless to say you get.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing a power train of a front engine / rear wheel drive hybrid vehicle including a hybrid drive device incorporating an engine start control device according to an embodiment of the present invention, together with its control system. FIG. 2 is an engagement logic diagram showing a relationship between a selected shift stage of the automatic transmission in FIG. 1 and a combination of engagement of shift friction elements. 2 is a flowchart showing an engine start control program executed by a power train control system in FIG. FIG. 4 is an operation time chart according to the engine start control program of FIG. 3. FIG.

Explanation of symbols

1 Engine (Power source)
2 Automatic transmission 3 Motor / generator (power source)
4 Transmission input shaft 6 First clutch 7 Transmission output shaft
H & LR / C High and low reverse clutch (second clutch)
D / C direct clutch (second clutch)
11 Integrated controller
12 Engine rotation sensor
13 Motor / generator rotation sensor
14 Transmission input rotation sensor
15 Transmission output rotation sensor
16 Accelerator position sensor
17 Storage state sensor
21 Engine controller
22 Motor / generator controller
23 1st clutch controller
24 Transmission controller

Claims (16)

Provide the engine and motor / generator in tandem as a power source,
The engine and motor / generator can be connected by the first clutch,
The motor / generator and drive wheel can be connected by the second clutch,
When starting the engine in a state where the first clutch is released and the second clutch is engaged to perform electric traveling only by the motor / generator, the transmission torque capacity of the second clutch is reduced and the first clutch is engaged, In a hybrid vehicle that starts the engine by cranking the engine with the driving torque of the motor / generator,
An engine of a hybrid vehicle configured to reduce the transmission torque capacity of the first clutch from when it is determined that the engine speed approaches a predetermined range with respect to the motor / generator speed by the engine start. Start control device. In the engine start control device of the hybrid vehicle according to claim 1,
An engine start control device for a hybrid vehicle, characterized in that an automatic transmission is interposed between the motor / generator and a drive wheel so that a shift friction element in the automatic transmission is used as the second clutch. In the engine start control device of the hybrid vehicle according to claim 1 or 2,
An engine start control device for a hybrid vehicle, characterized in that the determination that the engine speed approaches the predetermined range with respect to the motor / generator speed is made by a complete explosion determination of the engine. In the engine start control device of the hybrid vehicle according to claim 1 or 2,
An engine start control device for a hybrid vehicle, characterized in that the determination that the engine speed approaches the predetermined range with respect to the motor / generator speed is made based on a start determination of fuel injection of the engine. In the engine start control device of the hybrid vehicle according to claim 1 or 2,
An engine start control device for a hybrid vehicle, wherein the determination that the engine speed approaches the predetermined range with respect to the motor / generator speed is made by a rapid increase determination of the engine speed. In the engine start control device for a hybrid vehicle according to any one of claims 1 to 5,
An engine start control device for a hybrid vehicle, wherein the transmission torque capacity of the first clutch is made substantially zero when the rotational difference between the engine rotational speed and the motor / generator rotational speed becomes substantially zero. In the engine start control device for a hybrid vehicle according to any one of claims 1 to 6,
An engine start control device for a hybrid vehicle, wherein the transmission torque capacity of the first clutch is gradually decreased with a predetermined time change gradient. In the engine start control device of the hybrid vehicle according to claim 7,
The engine start control of the hybrid vehicle, wherein the predetermined time-varying gradient relating to the decrease in the first clutch transmission torque capacity is determined in accordance with a rotational difference between the engine speed and the motor / generator speed. apparatus. In the engine start control device for a hybrid vehicle according to any one of claims 6 to 8,
When the rotational difference between the engine speed and the motor / generator rotational speed is substantially zero, the transmission torque capacity of the first clutch is substantially zero. An engine start control device for a hybrid vehicle, characterized in that In the engine start control device of the hybrid vehicle according to any one of claims 1 to 9,
An engine start control device for a hybrid vehicle, wherein the transmission torque capacity of the first clutch is increased when the engine speed becomes higher than the motor / generator speed exceeding a set speed. In the engine start control device of the hybrid vehicle according to any one of claims 1 to 9,
An engine start control device for a hybrid vehicle, characterized in that a transmission torque capacity of the first clutch is increased from when a set time has elapsed since the engine speed coincided with the motor / generator speed. In the engine start control device of the hybrid vehicle according to claim 10 or 11,
An engine start control device for a hybrid vehicle, wherein the transmission torque capacity of the first clutch is gradually increased with a predetermined time change gradient. The engine start control device for a hybrid vehicle according to claim 12,
A hybrid vehicle characterized in that a predetermined time change gradient related to an increase in the first clutch transmission torque capacity is determined in accordance with at least one of a required acceleration feeling, an allowable acceleration shock, and an accelerator opening equivalent torque. Engine start control device. In the engine start control device for a hybrid vehicle according to claim 12 or 13,
An engine start control device for a hybrid vehicle, wherein the engine torque is reduced while the first clutch transmission torque capacity is increased. The engine start control device for a hybrid vehicle according to claim 14,
The engine torque reduction is performed by delaying the engine ignition timing in a state where the engine load is reduced by a certain amount from the accelerator opening equivalent value. . In the engine start control device for a hybrid vehicle according to claim 14 or 15,
At the time of rotation synchronization when the input / output rotation difference of the first clutch disappears, the decrease in the engine torque is finished to return the engine torque to the value corresponding to the accelerator opening, and the transmission torque capacity of the first clutch is fully engaged with the first clutch. An engine start control device for a hybrid vehicle, characterized by being configured to increase to a compensated value.

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