JP5614393B2 - Engine start system - Google Patents

Description

  The present invention relates to an engine start system that starts an engine using torque of an electric motor during traveling of a hybrid vehicle.

  As an engine starting system, when there is a request for starting the engine during the EV driving mode of the hybrid vehicle, the torque of the electric motor is transmitted to the engine via the clutch to start the engine and suppress vibrations in the starting process. It is known that the clutch is disengaged or the fastening force is reduced when the rotational speeds of the engine side and the motor side of the clutch coincide with each other (Patent Document 1). In addition, there is Patent Document 2 as a prior art document related to the present invention.

JP 2011-5957 A JP 2008-44599 A

  The system of Patent Document 1 does not take measures against the failure when a failure in which the clutch cannot be released occurs in the engine starting process. Therefore, when the above-mentioned failure occurs in the clutch during the engine start-up process, the release operation becomes impossible. Therefore, there is a possibility that the engine-side rotational speed exceeds the electric motor-side rotational speed while the clutch is engaged, and vibration is generated.

  Accordingly, an object of the present invention is to provide an engine start system that can suppress the occurrence of vibration even if a failure occurs in which a clutch cannot be released during a start process of an engine mounted on a hybrid vehicle.

  The engine start system of the present invention is applied to a hybrid vehicle in which an engine is connected to a power transmission path that outputs a driving force for driving via a clutch, and an electric motor is connected to the power transmission path, and the engine is stopped. In an engine start system for starting the engine by using the torque of the electric motor when there is a request to start the engine during the traveling mode, the clutch is engaged while sliding the clutch to crank the engine. A clutch control means for performing a half-engagement operation and a release operation for releasing the clutch on the condition that the rotation speed of the engine exceeds a startable limit after cranking of the engine is started; and the half-engagement operation If a failure occurs later that the clutch cannot be released, the engine speed of the clutch There are those comprising a fail-safe means for reducing the torque of the electric motor at a time when reaching the limit not exceeding a power transmission path side rotational speed, the (claim 1).

  According to this engine starting system, when a failure occurs in which the clutch cannot be released during the engine starting process, the torque of the electric motor is reduced when the engine side rotational speed of the clutch reaches a limit that does not exceed the power transmission path side rotational speed. To reduce. Therefore, it is possible to reduce the vibration generated when the engine-side rotational speed exceeds the power transmission path-side rotational speed without releasing the clutch.

  In one aspect of the engine start system of the present invention, the fail-safe means may reduce the torque of the electric motor while performing fuel cut on the engine when the failure occurs (claim 2). According to this aspect, since the fuel cut is also performed when reducing the torque of the electric motor, the output torque of the engine is reduced. Therefore, the above vibration can be further suppressed.

  In order to suppress the vibration described above, the torque of the electric motor may be reduced when the engine side rotational speed of the clutch reaches a limit that does not exceed the power transmission path side rotational speed. For example, the fail safe means may be configured such that the difference between the engine side rotational speed and the power transmission path side rotational speed is less than a predetermined safety margin when the engine side rotational speed and the power transmission path side rotational speed coincide with each other. The torque of the electric motor may be reduced at a time when it becomes (Claim 3). According to this aspect, the above-described vibration can be suppressed even if the torque of the electric motor is reduced at any time.

  As described above, according to the engine starting system of the present invention, the torque of the electric motor is reduced when a failure that cannot release the clutch occurs during the starting process of the engine. Vibration generated by exceeding the transmission path side rotation speed can be reduced.

The figure which showed the outline | summary of the vehicle to which the starting system which concerns on one form of this invention was applied. The flowchart which showed an example of the control routine of start control. The timing chart which showed an example of the control result when an electromagnetic clutch is normal. The timing chart which showed an example of the control result at the time of a failure of an electromagnetic clutch. The figure which showed the other example of the vehicle which can apply the starting system of this invention.

  As shown in FIG. 1, the vehicle 1 is configured as a so-called hybrid vehicle in which an internal combustion engine 2 and a motor / generator 3 as an electric motor are provided as a driving power source. An internal combustion engine (hereinafter referred to as an engine) 2 is configured as a spark ignition type internal combustion engine. An output shaft 2 a of the engine 2 is connected to an automated transmission (AMT) 8 through an electromagnetic clutch 7. The electromagnetic clutch 7 is engaged and disengaged in accordance with the shifting operation of the AMT 8. Further, the electromagnetic clutch 7 can adjust the power transmission rate almost steplessly by changing the strength of the supply current. Therefore, by controlling the strength of the current supplied to the electromagnetic clutch 7, a half-engagement operation in which the electromagnetic clutch 7 is engaged while sliding is possible.

  The AMT 8 can select one shift speed from a plurality of forward shift speeds. The selection of the gear position by the AMT 8 is automatically performed based on the vehicle speed of the vehicle 1 and the accelerator opening. Further, when the AMT 8 is switched to the manual mode, the gear position is selected by the driver operating a shift knob (not shown).

  The AMT 8 includes an input shaft 10, an output shaft 11 extending parallel to the input shaft 10, and first to fourth gear pairs G 1 to G 4 provided between the input shaft 10 and the output shaft 11. . The first to fourth gear pairs G1 to G4 correspond to the first speed to the fourth speed. The backward running of the vehicle 1 is performed when the motor / generator 8 reversely rotates with the first speed selected. The first gear pair G1 includes a first drive gear 13 and a first driven gear 14 that mesh with each other. The second gear pair G2 includes a second drive gear 15 and a second driven gear 16 that mesh with each other. The third gear pair G3 includes a third drive gear 17 and a third driven gear 18 that mesh with each other. The fourth gear pair G4 includes a fourth drive gear 19 and a fourth driven gear 20 that mesh with each other. The gear ratio of each gear pair G1 to G4 is set so as to decrease in the order of the first gear pair G1, the second gear pair G2, the third gear pair G3, and the fourth gear pair G4.

  The first drive gear 13 and the second drive gear 15 are provided on the input shaft 10 so as to rotate integrally with the input shaft 10. On the other hand, the third drive gear 17 and the fourth drive gear 19 are provided on the input shaft 10 so as to be rotatable relative to the input shaft 10. The first driven gear 14 and the second driven gear 16 are provided on the output shaft 11 so as to be rotatable relative to the output shaft 11. On the other hand, the third driven gear 18 and the fourth driven gear 20 are provided on the output shaft 11 so as to rotate integrally with the output shaft 11.

  The AMT 8 is provided with coupling devices C1 to C4 in order to validate any one of the plurality of shift speeds. Each coupling device C1 to C4 is configured as a well-known meshing clutch and is operated by an operation mechanism (not shown). The first coupling device C1 operates between an engaged state in which the first driven gear 14 is coupled to the output shaft 11 and the first driven gear 14 and the output shaft 11 are integrally rotated, and a released state in which the coupling is released. it can. Similarly, the second coupling device C2 includes an engagement state in which the second driven gear 16 is coupled to the output shaft 11 and the second driven gear 16 and the output shaft 11 are integrally rotated, and a released state in which the coupling is released. Can work between. Further, the third coupling device C3 is connected between an engagement state in which the third drive gear 17 is coupled to the input shaft 10 and the third drive gear 17 and the input shaft 10 are integrally rotated and a released state in which the coupling is released. It can work with. Similarly, the fourth coupling device C4 includes an engagement state in which the fourth drive gear 19 is coupled to the input shaft 11 to rotate the fourth drive gear 19 and the input shaft 11 together, and a release state in which the coupling is released. Can work between. The AMT 8 can validate any one of the plurality of shift speeds when any one of the coupling devices C1 to C4 is engaged.

  A first output gear 21 is provided on the output shaft 11 so as to rotate integrally. The first output gear 21 meshes with a ring gear 26 provided in a case of a differential mechanism 25 connected to a drive wheel (not shown). Torque output from the AMT 8 is transmitted to the left and right drive wheels via the ring gear 26 and the differential mechanism 25. The power transmission path from the AMT 8 to the drive wheels is for outputting the driving force for traveling and therefore corresponds to the power transmission path according to the present invention. The torque of the motor / generator 3 is transmitted to the output shaft 11 via the gear train 28. The gear train 28 includes a second output gear 29 that rotates integrally with the output shaft 11, and a motor drive gear 30 that rotates integrally with the motor shaft 3 a while meshing with the second output gear 29.

  Control of the engine 2, the motor / generator 3, the electromagnetic clutch 7, and the AMT 8 is performed by an electronic control unit (ECU) 40 configured as a computer unit. The ECU 40 holds various control programs for obtaining an appropriate traveling state of the vehicle 1. The ECU 40 executes control of the control object such as the engine 2 described above by executing these programs. Various sensors that output information related to the running state of the vehicle 1 are connected to the ECU 40. For example, an input side resolver 41 that outputs a signal according to the rotational speed of the input shaft 10, an output side resolver 42 that outputs a signal according to the rotational speed of the output shaft 11, and a signal according to the crank angle of the engine 2 are output. A crank angle sensor 43 and an accelerator opening sensor 44 that outputs a signal corresponding to the accelerator opening are electrically connected to the ECU 40.

  The ECU 40 performs various controls such as a hybrid travel mode in which the engine 2 and the motor / generator 3 are travel power sources, and an electric travel mode in which only the motor / generator 3 is traveled while the engine 2 is stopped. There is a travel mode switching control for switching the travel mode. Along with the travel mode switching control, stop control and start control of the engine 2 are performed. Further, regenerative control is performed in which the motor / generator 3 generates power using the power input from the drive wheels when the vehicle 1 is decelerated. Hereinafter, control related to the present invention among the control executed by the ECU 40 will be described, and description of other control will be omitted or simplified.

  The ECU 40 stops the engine 2 in accordance with the stop of the vehicle 1 except when a prohibition condition such as insufficient battery storage rate (not shown) is satisfied, and adjusts to the start operation reflecting the driver's start intention. Then, so-called idle stop control is performed to restart the internal combustion engine 2. Further, the ECU 40 may start the engine in accordance with an increase in the required driving force during the electric travel mode and switch the travel mode from the electric travel mode to the hybrid travel mode. In order to realize the start of the engine 2 in the process of switching the travel mode, the ECU 40 performs the start control of FIG. The routine program of FIG. 2 is stored in the ECU 40, read out in a timely manner, and repeatedly executed at predetermined intervals of about several milliseconds.

  In step S1, the ECU 40 determines whether or not there is a request for starting the engine 2. If there is a start request, the process proceeds to step S2, and if not, the subsequent process is skipped and the current routine is terminated. The start request is generated when a start condition such as the required driving force increases exceeding a threshold value during traveling in the electric travel mode is satisfied.

  In step S2, the ECU 40 starts the half-engagement operation of the electromagnetic clutch 7 and increases the clutch torque. At the same time, the ECU 40 compensates for the loss of the electromagnetic clutch 7 to prevent the vehicle 1 from decelerating. Torque). Thereby, the engine 2 is cranked. Note that the amount of increase in clutch torque and motor torque per process in step S2 is set as appropriate.

  In step S3, the ECU 40 determines whether or not the rotational speed Ne of the engine 2 has exceeded the startable limit Nec. The startable limit Nec is unique to the engine 2 and is a limit value of the rotational speed of the engine 2 that can be started by firing. If the rotational speed Ne exceeds the startable limit Nec, the process proceeds to step S4. Otherwise, the process returns to step S2.

  In step S4, the ECU 40 fires the engine 2 and simultaneously reduces the clutch torque and the motor torque. That is, the ECU 40 starts the release operation for the electromagnetic clutch 7 while reducing the firing and motor torque.

  In step S5, the ECU 40 determines whether or not the clutch torque Tqc is larger than the reference torque Tqcl. The reference torque Tqcl is a lower limit value of the clutch torque that does not generate vibration. If the clutch torque Tqc is larger than the reference torque Tqcl, the process proceeds to step S6, and if not, the process proceeds to step S12.

  In step S6, the ECU 40 determines that the electromagnetic clutch 7 has failed. It is determined whether or not the cause that the clutch torque Tq exceeds the reference torque Tqcl is a failure in which the electromagnetic clutch 7 cannot be released. The determination of the failure is performed by comparing the relationship between the current supplied to the electromagnetic clutch 7 and the clutch torque Tq with the relationship at the normal time. If the electromagnetic clutch 7 has failed as described above, the process proceeds to step S7, and if not, the process proceeds to step S12.

  In step S <b> 7, the ECU 40 performs fuel cut on the engine 2. Thereby, since the torque of the engine 2 is reduced, vibration can be suppressed.

  In step S8, the ECU 40 determines whether or not the difference between the rotational speed Nin of the input shaft 10 and the rotational speed Ne of the engine 2 is less than the safety margin β. The safety margin β is appropriately set in consideration of control delay and the like. The time when the difference becomes less than the safety margin β corresponds to the time when the engine-side rotational speed of the electromagnetic clutch 7 reaches a limit that does not exceed the power transmission path-side rotational speed. In this embodiment, since the output shaft 2a and the input shaft 10 of the engine 2 are directly connected to the electromagnetic clutch 7, the rotational speed of the engine 2 is the engine-side rotational speed, and the rotational speed of the input shaft 10 is the power transmission path side. It corresponds to each rotation speed. Note that the process of step S8 can be changed to a process of determining whether or not the engine-side rotational speed of the electromagnetic clutch 7 and the power transmission path-side rotational speed match without setting the safety margin β. .

  In step S9, the ECU 40 reduces the motor torque. The degree of reduction may be set as appropriate. In this embodiment, the ECU 40 reduces the motor torque by the amount of clutch torque borne by the failed electromagnetic clutch 7.

  In step S10, the ECU 40 cancels the fuel cut. Thereby, the torque of the engine 2 increases.

  In step S <b> 11, the ECU 40 switches the torque of the travel drive source from the torque of the motor / generator 3 to the torque of the engine 2. Specifically, while further reducing the torque of the motor / generator 3, the torque of the engine 2 is increased simultaneously with the reduction operation.

  In step S12, the ECU 40 determines whether or not the difference between the rotational speed Nin of the input shaft 10 and the rotational speed Ne of the engine 2 is less than the safety margin α. The safety margin α may be the same as or different from the safety margin β in step S8. If the difference is less than the safety margin α, the process proceeds to step S13. If not, the process returns to step S4 to continue the release operation.

  In step S13, the ECU 40 switches the torque of the driving source for driving from the torque of the motor / generator 3 to the torque of the engine 2 while sliding the electromagnetic clutch 7 by engaging it. When the electromagnetic clutch 7 is completely engaged, the travel mode is switched to a travel mode using the engine 2 as a drive source.

  2 is performed, the control results shown in FIGS. 3 and 4 are obtained. As shown in FIG. 3, when the electromagnetic clutch 7 is normal, the half-engagement operation is started from t0 when the start request is generated, and the clutch torque Tqc is increased. The clutch torque Tqc is kept constant from time t1 to time t2. As a result, the engine 2 is cranked and its rotational speed Ne gradually increases. In parallel with the cranking of the engine 2, the engine 2 is fired. That is, the flag for managing the execution of the fuel cut (F / C) is switched from ON to OFF between time t1 and time t2.

  In order to compensate for the loss associated with the half-engagement operation of the electromagnetic clutch 7, the torque Tqm of the motor / generator 3 changes in the same manner as the clutch torque Tqc. When the rotational speed Ne of the engine 2 reaches the startable limit Nec at time t2, the release operation of the electromagnetic clutch 7 is started and the clutch torque Tqc decreases. In accordance with the release operation, the torque Tqm of the motor / generator 3 also decreases in the same manner as the clutch torque Tqc. By time t3 when the rotational speed Ne of the engine 2 reaches the rotational speed Nin of the input shaft 10, the electromagnetic clutch 7 is completely released and the clutch torque Tqc is zero. Therefore, no vibration is generated in the electromagnetic clutch 7. Thereafter, the engagement operation of the electromagnetic clutch 7 is started at time t4, and the torque Tqm of the motor / generator 3 is gradually reduced to zero simultaneously with the engagement operation. As a result, the torque of the driving source for traveling is switched from the torque Tqm of the motor / generator 3 to the torque of the engine 2. At time t5, the electromagnetic clutch 7 is completely engaged, and the traveling mode is switched to the traveling mode using the engine 2 as a drive source.

  On the other hand, as shown in FIG. 4, when the above-described failure occurs in the electromagnetic clutch 7, even if the rotational speed Ne of the engine 2 reaches the startable limit Nec at time t2, the release operation of the electromagnetic clutch 7 is performed due to the failure F. Can not. Therefore, the clutch torque Tqc remains constant. In response to the determination of the failure F at time t2, a fuel cut is performed and the firing is interrupted. The torque Tqm of the motor / generator 3 is reduced by the clutch torque Tqc borne by the electromagnetic clutch 7 immediately before the time t3 when the rotational speed Ne of the engine 2 reaches the rotational speed Nin of the input shaft 10. As a result, the energy is reduced as compared with the case where the torque Tqm of the motor / generator 3 is maintained without being reduced while a failure occurs. Therefore, vibration generated in the electromagnetic clutch 7 is suppressed. Thereafter, the firing is resumed at time t4. Simultaneously with the resumption of firing, the torque Tqm of the motor / generator 3 is reduced to zero. As a result, the torque of the driving source for traveling is switched from the torque Tqm of the motor / generator 3 to the torque of the engine 2. Since it is difficult to continue running with the engine 2 after the torque Tqm reaches 0 and the torque is switched, a warning that prompts the driver to stop may be output.

  In the above embodiment, the ECU 40 functions as the clutch control means and the fail safe means of the present invention by executing the control routine of FIG. However, this invention is not limited to the said form, It can implement with a various form within the range of the summary of this invention. It is not essential to perform fuel cut when the clutch fails. It is possible to suppress vibration by reducing the torque of the electric motor without performing fuel cut.

  The vehicle to which the engine start system of the present invention can be applied is not limited to the form shown in FIG. For example, as shown in FIG. 5, a vehicle 1 ′ equipped with a transmission 60 incorporating a motor / generator 61 as an electric motor may be used. There are no restrictions on the location of the motor. Therefore, the electric motor should just be provided in the output side rather than the clutch. For example, the electric motor may be provided between the drive mechanism and the differential mechanism to which the drive wheels are connected. Furthermore, the electric motor may be provided inside the drive wheel as an in-wheel motor. The transmission mounted on the vehicle may be a dual clutch transmission (DCT), a continuously variable transmission (CVT), or an automatic transmission (AT).

1, 1 'Vehicle 2 Engine 3 Motor generator (electric motor)
7 Electromagnetic clutch (clutch)
40 ECU (clutch control means, fail-safe means)

Claims (3)

The present invention is applied to a hybrid vehicle in which an engine is connected to a power transmission path for outputting a driving force for driving through a clutch and an electric motor is connected to the power transmission path, and the engine is stopped during a traveling mode in which the engine is stopped. In an engine start system for starting the engine using the torque of the electric motor when there is a start request,
The clutch is released on the condition that a half-engagement operation in which the clutch is slid and engaged to crank the engine and the engine speed exceeds the startable limit after the cranking of the engine is started. The clutch control means for performing the releasing operation and the failure that the clutch cannot be released after the half-engagement operation has reached a limit where the engine side rotational speed of the clutch does not exceed the power transmission path side rotational speed An engine start system comprising: fail-safe means for reducing torque of the electric motor at a time.   The engine start system according to claim 1, wherein the fail-safe means reduces the torque of the electric motor while performing fuel cut on the engine when the failure occurs.   In the fail-safe means, the difference between the engine side rotational speed and the power transmission path side rotational speed exceeds a predetermined safety margin at the time when the engine side rotational speed and the power transmission path side rotational speed coincide with each other. The engine starting system according to claim 1 or 2, wherein the torque of the electric motor is reduced at a time.

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