JP2007276510A - Dpf control device for hybrid vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform efficient regeneration of DPF (particulate filter) while preventing torque shock by sudden increase of engine torque or welding loss of PDF in transfer to a DPF regeneration mode while traveling in a motor assist mode with a low battery charged quantity. <P>SOLUTION: When the deposit amount of PM (particulate) is larger than a predetermined deposit amount (S2), and the battery charged quantity is lower than a predetermined charged quantity (S3) while traveling in the motor assist mode, a first target torque of engine is computed based on the battery charged quantity (S4), and when the torque difference between the first target torque and a current torque is larger than a predetermined value (S5), a second target torque smaller than the first target torque, at which the exhaust gas temperature is a predetermined temperature or higher is computed (S6). At least one of fuel injection quantity and fuel injection timing is controlled so that the current torque becomes the second target torque, and then controlled to reach the first target torque (S11). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to DPF regeneration control in a parallel hybrid vehicle.

  A hybrid vehicle that has an engine and a motor as a driving force source and switches the driving force source according to the driving state is superior in fuel efficiency and exhaust purification characteristics compared to a vehicle that travels only with a conventional engine output. Exhaust gas exhaust due to engine operation cannot be avoided, and an exhaust gas purification device for purifying exhaust gas exhausted from the engine is necessary.

In Patent Document 1, in a hybrid vehicle, when the amount of charge of a battery is equal to or lower than a predetermined lower limit value, the driving force of a diesel engine that drives the generator is controlled to start charging the battery from the generator. It is disclosed that when there is a regeneration request for a particulate filter (DPF) provided in the exhaust passage of the engine, the predetermined lower limit value is changed to a value lower than that during normal operation. As a result, the continuous charging time of the battery is extended, so that the continuous operation time in a high-load state of the engine is also extended, and the time for burning particulates (PM) by the high-temperature exhaust gas from the diesel engine is extended. Will be secured.
JP 2002-242721 A

  In general, the engine torque is high during DPF regeneration, and the engine torque is low in a so-called motor assist mode in which both the engine and the motor are used for driving. Further, when the generator is driven to charge the battery, it is necessary to increase the engine torque accordingly.

  Therefore, if the DPF regeneration and the battery charging are started during traveling in the motor assist mode, the engine torque may rapidly increase and a torque shock may occur. Further, as the engine torque increases, the exhaust gas temperature rises rapidly, and PM combustion in the DPF may run out of control, causing the DPF to melt.

  The present invention is effective in preventing a torque shock and a DPF melting due to a sudden increase in engine torque when shifting to the DPF regeneration mode while traveling in the motor assist mode and the battery charge is low. The purpose is to regenerate the DPF.

  The DPF control device for a hybrid vehicle according to the present invention is the time when it is determined that the accumulated amount of PM is larger than the predetermined accumulated amount during driving by driving both the engine and the motor, and the charged amount of the battery is predetermined. When it is determined that the charging amount is lower than the charging amount of the engine, a first target torque of the engine is calculated based on the charging amount of the battery, and when the torque difference between the first target torque and the current torque is larger than a predetermined value, The engine torque at which the exhaust gas temperature is equal to or higher than a predetermined temperature, and a second target torque smaller than the first target torque is calculated. When the second target torque is calculated, the engine torque becomes the second target torque. After controlling at least one of the fuel injection amount and the fuel injection timing of the engine so as to become the torque, the fuel injection amount and the fuel of the engine are set so that the engine torque becomes the first target torque. Controlling at least one of injection timing.

  According to the present invention, when switching from the motor assist mode to the DPF regeneration mode and the battery charge level is low, the engine torque is lower than the first target torque and the exhaust temperature is equal to or higher than the predetermined temperature. Since at least one of the fuel injection amount and the fuel injection timing of the engine is controlled so as to increase to the first target torque after increasing to the second target torque, the engine torque is generated for power generation in addition to DPF regeneration. Even in a situation where it is necessary to increase the DPF, it is possible to regenerate the DPF while preventing a torque shock by suppressing a rapid increase in torque.

(First embodiment)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a DPF control device for a hybrid vehicle according to the present invention. The hybrid vehicle of the present invention is a parallel hybrid vehicle, and is configured with the engine 1 and the motor 2 as driving force sources.

  The engine 1 transmits the driving force to the drive wheels 4 via the motor 2 and the transmission 3 and drives the motor 2. The transmission 3 changes the rotational speed of the input shaft and outputs it from the output shaft.

  The motor 2 is driven by consuming the electric power stored in the battery 5 and generates electric power by being driven by the driving force of the engine 1. The electric power stored in the battery 5 is supplied to the motor 2 through the inverter 6, and the electric power generated by the motor 2 is stored in the battery 5 through the inverter 6. Further, the regenerative energy obtained during braking of the vehicle is recovered as electric power by the motor 2 and charged to the battery 5.

  The charging / discharging of the electric power to the battery 5 is controlled by adjusting the power generation amount by controlling the driving of the motor 2 by the engine 1 and increasing / decreasing the electric power allocated to the charging of the battery 5 (charging control means). In the present embodiment, as shown in FIG. 2, when the charge amount of the battery 5 (hereinafter referred to as “SOC”) decreases and falls below the lower limit value L1, power charging to the battery 5 is started, and the SOC increases and the upper limit value is reached. Charging is stopped when H1 or higher.

  Therefore, when the SOC of the battery 5 is sufficient and the load required by the vehicle can be covered only by the power of the battery 5, the engine 1 is stopped and the battery 5 is discharged, and the engine 1 is turned off when the SOC becomes insufficient. The battery 5 is charged with electric power other than the driving force of the vehicle. In this way, charging / discharging of the power to the battery 5 is controlled by stopping / starting the operation of the engine 1, and at the time of charging, the power generation amount of the motor 2 is large by the amount charged to the battery 5. The load is greater during charging than during discharging.

  The engine 1 is configured as a general diesel engine 1. The exhaust passage 7 of the engine 1 is provided with a particulate filter 8 (hereinafter referred to as “DPF”) for collecting particulates (hereinafter referred to as “PM”) in the exhaust gas. Further, pressure sensors 9 for detecting the pressure in the exhaust passage 7 are disposed on the upstream side and the downstream side of the DPF 8 in the exhaust passage 7 respectively.

  The controller 10 controls the engine 1 and the motor 2 based on the pressure in the exhaust passage 7 detected by the pressure sensor 9 and the charge amount of the battery 5 detected by the inverter 6.

  Next, the control performed by the controller 10 will be described with reference to the flowchart of FIG. This control is executed during traveling in the motor assist mode in which the vehicle is driven by the driving force of both the diesel engine 1 and the motor 2.

  In step S1, the PM accumulation amount in the DPF 8 is estimated. The PM accumulation amount is estimated by calculating the pressure difference between the upstream side and the downstream side of the DPF 8 based on the pressure detected by the pressure sensor 9. Note that the relationship between the PM deposition amount and the pressure difference is obtained in advance by experiments or the like.

  In step S2, it is determined whether there is a DPF regeneration request. If there is a DPF regeneration request, the process proceeds to step S3, and if there is no DPF regeneration request, the process proceeds to step S13 to perform the normal operation mode. The normal operation mode is a normal operation mode in which DPF regeneration is not performed, and details of this mode are omitted.

  The DPF regeneration request is determined to be “present” when the PM accumulation amount is greater than the upper limit value, and is determined to be “absent” once the PM accumulation amount is less than the lower limit value after it is determined that the regeneration request is present. Here, as shown in FIG. 4, when the PM accumulation amount becomes smaller than the accumulation amount at the point D, the PM collection efficiency of the DPF 8 rapidly decreases, so the accumulation amount at the point D is set to the lower limit value.

  In step S3, it is determined whether the SOC is lower than a predetermined value L1. If the SOC is lower than the predetermined value L1, the process proceeds to step S4. If the SOC is equal to or greater than the predetermined value L1, the process proceeds to step S12 (particulate filter regeneration means) to perform the DPF regeneration mode. The predetermined value L1 is set to the lower limit value L1 in FIG. 2, whereby it is possible to determine a situation where the battery 5 needs to be charged in addition to the DPF regeneration, that is, a situation where the engine torque becomes larger.

  Further, the DPF regeneration mode is a mode in which the PM in the DPF 8 is burned by increasing the exhaust temperature of the engine 1 to reduce the accumulation amount. For example, the fuel injection amount is increased and the fuel injection timing is retarded. As a result, the exhaust temperature of the engine 1 is raised.

  In step S4 (first target torque calculation means), a target engine torque is calculated. The target engine torque is calculated based on the SOC and the engine speed with reference to the map of FIG.

  In step S5, a difference between the target engine torque and the current engine torque is calculated, and it is determined whether or not this difference is greater than a predetermined value To. If the torque difference is larger than the predetermined value To, the process proceeds to step S6, and if it is equal to or smaller than the predetermined value To, the process proceeds to step S12 to perform the DPF regeneration mode.

  In step S6 (second target torque calculation means), an operating point is set. With reference to the map of FIG. 6, the operating point is set between the current operating point and the operating point corresponding to the target torque so that the exhaust temperature is equal to or higher than the combustion start temperature of the particulate matter. However, the exhaust temperature is set to be closer to the exhaust temperature at the target torque than the current exhaust temperature. In the following description, the current operating point is A, the operating point corresponding to the target torque is C, and the operating point set in step S6 is B.

  In step S7, the fuel injection timing and the fuel injection amount of the engine 1 necessary for shifting the operating point to points B and C are calculated. The fuel injection amount is calculated based on the target torque and rotational speed at each operating point with reference to the map of FIG. The fuel injection timing is calculated based on the exhaust temperature and the fuel injection amount at each operating point with reference to FIG. Here, since the operating point B is set so that the exhaust temperature is closer to the exhaust temperature at the target torque than the current exhaust temperature, the increment of the target injection amount and the retard amount of the injection timing are more between AB than between BC. Become more.

In step S8, the engine cycle number N _AB required for the transition from the operating point A to the operating point B and the engine cycle number N _BC required for the transition from the operating point B to the operating point C are calculated. The engine cycle numbers N _AB and N _BC are calculated based on the following equations (1) and (2).

Here, N ₀ is a predetermined number of cycles, X _A is the combustion speed at the operating point A, X _B is the combustion speed at the operating point B, and X _C is the combustion speed at the operating point C. The predetermined number of cycles N ₀ is a value that does not bother the driver with torque shock, and is obtained in advance by experiments.

In step S9, a retard amount ΔIT of the fuel injection timing per cycle is calculated. The retard amount ΔIT _AB per cycle during the transition from the operating point A to the operating point B, and the retard amount ΔIT _BC per cycle during the transition from the operating point B to the operating point C are the following (3), ( 4) Calculated based on the equation.

Here, IT _A , IT _B and IT _C are fuel injection timings at the operating points A, B and C, respectively.

In step S10, a fuel injection amount increment ΔQ per cycle is calculated. The injection amount increment ΔQ _AB per cycle at the time of transition from the operating point A to the operating point B, and the injection amount increment ΔQ _BC per cycle at the time of transition from the operating point B to the operating point C are the following (5) , (6).

Here, a Q _A, Q _B, Q _C respectively operating point A, B, the fuel injection amount in C.

In step S11 (engine control means), the engine quantity 1 is controlled stepwise until the engine cycle numbers N _AB and N _BC calculated in step S8 elapse, and the combustion temperature of the engine 1 is raised while surplus. Charge with the engine torque of.

  Next, the operation of this embodiment will be described with reference to FIG. FIG. 9 is a time chart showing the operation of the DPF control device for a hybrid vehicle in the present embodiment.

  While traveling in the motor assist mode, when the DPF regeneration request is determined to be “present” at time t1, and the SOC at this time is lower than the predetermined value L1, and the difference between the target torque and the current torque is large, Set point B. The fuel injection amount and the injection timing are changed to the operating point B by changing stepwise for each cycle. At this time, the fuel injection amount is increased and the fuel injection timing is retarded. As a result, the exhaust temperature of the engine 1 rises, so that the temperature of the DPF 8 rises and the PM combustion rate rises as shown in the table of FIG. Further, since the engine torque increases due to the increase in the fuel injection amount, power is generated by the surplus torque and the SOC increases.

  At time t2, the operation point B is shifted to the operation point B. Further, the fuel injection amount and the injection timing are gradually changed from t1 to t2 in a stepwise manner to be shifted to the operation point C.

  At time t3, the driving point C is reached and the target torque is achieved, so that DPF regeneration is performed.

  As described above, in the present embodiment, the torque difference between the target torque and the current torque is greater than the predetermined value To when switching from the motor assist mode to the DPF regeneration mode and when the charge amount of the battery 5 is low. When the operation point B is set between the operation point A and the operation point C and the exhaust gas temperature is equal to or higher than the predetermined temperature, the engine torque is increased to the torque corresponding to the operation point B, and then the operation point C is reached. The fuel injection timing is retarded while increasing the fuel injection amount of the engine 1 so as to increase the target torque, which is a corresponding torque. As a result, it is possible to suppress an increase in torque while raising the exhaust temperature, and to suppress a sudden increase in torque even in a situation where it is necessary to increase the engine torque for power generation in addition to DPF regeneration. Thus, the DPF 8 can be regenerated while preventing torque shock.

  Further, the operating point B is set so that the increase in the fuel injection amount and the retard amount at the fuel injection timing are smaller between the operating points B and C than between the operating points A and B. The rising speed of the DPF 8 temperature is lower between the operating points B and C, and the DPF 8 can be prevented from overheating due to overheating.

  Furthermore, since the predetermined temperature is set to a temperature equal to or higher than the combustion start temperature of PM, even if the engine torque is increased stepwise, PM starts combustion at the operating point B. Can be played.

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made within the scope of the technical idea.

  For example, in this embodiment, the fuel injection amount and the injection timing are controlled in order to increase the exhaust temperature and increase the engine torque. However, as shown in the time chart of FIG. Similar effects can be obtained by reducing the valve opening and controlling the fuel injection amount and the injection timing from the operating points B to C.

  In the present embodiment, the operation point B is set between the operation point A and the operation point C, but two or more operation points may be set between the operation point A and the operation point C. As a result, the torque fluctuation becomes more gradual, and a torque shock can be prevented more reliably.

It is a schematic block diagram which shows the structure of the DPF control apparatus of the hybrid vehicle in this embodiment. It is a map which shows charge control of the DPF control apparatus of the hybrid vehicle in this embodiment. It is a flowchart which shows control of the DPF control apparatus of the hybrid vehicle in this embodiment. It is a table which shows the relationship between the accumulation amount of particulate matter in a particulate filter, and collection efficiency. It is a map which shows the relationship between an engine speed, SOC, and target torque. It is a map which shows the relationship between an engine speed, a torque, and exhaust temperature. It is a map which shows the relationship between an engine speed, a torque, and target fuel injection amount. It is a map which shows the relationship between fuel-injection time, fuel-injection amount, and exhaust temperature. It is a time chart which shows the effect | action of the DPF control apparatus of the hybrid vehicle in this embodiment. It is a table which shows the relationship between DPF temperature and PM combustion speed. It is a time chart which shows the effect | action of the DPF control apparatus of the hybrid vehicle in another embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Motor 3 Transmission 4 Drive wheel 5 Battery 6 Inverter 7 Exhaust passage 8 Particulate filter (DPF)
9 Pressure sensor 10 Controller

Claims (6)

In a hybrid vehicle using at least one of a diesel engine and a motor as a driving force source,
A battery that charges the electric power generated by the motor driven by the engine;
When it is determined that the amount of charge of the battery is lower than a predetermined amount of charge, charge control means for driving the engine and starting charging the battery;
A particulate filter provided in an exhaust passage of the engine and collecting particulate matter contained in the exhaust;
When it is determined that the accumulation amount of the particulate matter collected by the particulate filter is larger than a predetermined accumulation amount, the particulate matter is burned by increasing the torque of the engine and raising the exhaust temperature. Curate filter regeneration means;
While driving with both the engine and the motor, it is determined that the accumulation amount is greater than a predetermined accumulation amount, and the charge amount of the battery is determined to be lower than a predetermined charge amount. A first target torque calculating means for calculating a first target torque of the engine based on a charge amount of the battery;
When the torque difference between the first target torque and the current torque is greater than a predetermined value, the engine torque at which the exhaust temperature of the engine is equal to or higher than a predetermined temperature, the second torque being smaller than the first target torque. Second target torque calculating means for calculating a target torque;
When the second target torque is calculated, after controlling at least one of the fuel injection amount and fuel injection timing of the engine so that the engine torque becomes the second target torque, the engine torque is Engine control means for controlling at least one of the fuel injection amount and the fuel injection timing of the engine so as to obtain a first target torque;
A hybrid vehicle comprising:   The hybrid vehicle according to claim 1, wherein the engine control means retards the fuel injection timing and increases the fuel injection amount to increase the torque of the engine in a stepwise manner.   The engine control means retards the fuel injection timing and increases the fuel injection amount to increase the combustion rate of particulate matter deposited on the particulate filter in a stepwise manner. 2. The hybrid vehicle according to 2.   The engine control means is configured to calculate a particulate matter combustion speed difference between the current torque and the second target torque, or a particulate matter combustion speed difference between the second target torque and the first target torque. 4. The hybrid vehicle according to claim 2, wherein the fuel injection timing and the fuel injection amount are controlled so that the rate of change of the fuel injection timing and the fuel injection amount decreases as the value increases.   The second target torque calculating means determines whether the fuel injection timing and the amount of change in the fuel injection amount required to increase the engine torque to the second target torque are changed from the second target torque to the first target torque. The second target torque is calculated so as to be larger than a change amount of the fuel injection timing and the fuel injection amount required to increase the target torque to a predetermined target torque. The hybrid vehicle according to item 1.   The hybrid vehicle according to any one of claims 1 to 5, wherein the predetermined temperature is equal to or higher than a combustion start temperature of the particulate matter.

Images