JP3905515B2 - Regeneration control method of exhaust purification device in diesel hybrid vehicle - Google Patents

Description

  The present invention relates to a regeneration control method for an exhaust purification device in a diesel hybrid vehicle, and more specifically, to increase the PM regeneration opportunity of the exhaust purification device even during EV travel other than during engine travel, and to promote PM regeneration of the exhaust purification device. The present invention relates to a regeneration control method for an exhaust emission control device in a diesel hybrid vehicle capable of performing the same.

  In recent years, diesel hybrid vehicles have been developed from the viewpoint of conservation of the global environment and resource saving. For example, this diesel hybrid vehicle collects a diesel engine, a motor generator that assists in power generation by the diesel engine output or engine output by battery power, and particulate matter (hereinafter abbreviated as PM) in the exhaust gas. A filter having a particulate filter (hereinafter simply referred to as a filter) is known.

  By the way, this filter gradually clogs when the amount of collected PM increases, and the pressure loss increases. Therefore, when the clogging reaches a certain level, the collected PM is burned to eliminate clogging ( Hereinafter, it is referred to as PM regeneration). As a method for regenerating PM, for example, a method of burning PM by increasing engine load and supplying high-temperature exhaust gas to a filter is known.

  In a diesel hybrid vehicle equipped with such an exhaust purification device, when there is a regeneration request for the filter, the lower limit value of the battery charge amount is set to a value lower than that during normal operation, whereby the continuous charge time of the battery is reached. To extend the continuous operation time in a high load state where a relatively high temperature exhaust gas is supplied. As a result, a control technique has been proposed that ensures a relatively long combustion time for PM deposited on the filter and promotes regeneration of the filter (see, for example, Patent Document 1).

  As a related technique, when promoting the oxidation of PM deposited on the purification catalyst, the operation state of the diesel engine is changed to increase the oxygen concentration in the exhaust gas flowing into the purification catalyst, and the engine operation There has been proposed a technique for controlling the operation state of a motor generator so as to cancel the output fluctuation accompanying the state change (see, for example, Patent Document 2).

  Further, in a diesel hybrid vehicle, a diesel engine is operated such that the PM component contained in the exhaust gas is a predetermined value or less, and a deficient torque of the engine is adjusted by a motor generator (for example, (See Patent Document 3).

JP 2002-242721 A JP 2003-120263 A JP 2002-115576 A

  However, the conventional technique according to Patent Document 1 has a problem in that there are few opportunities for PM regeneration because PM regeneration control of the exhaust purification device is performed only when the engine is running.

  In the prior arts disclosed in Patent Document 2 and Patent Document 3 described above, a motor generator is used to adjust torque fluctuations, but PM regeneration of the exhaust purification device is performed during EV travel using only the motor generator as a drive source. No control is disclosed to increase the opportunity.

  The present invention has been made in view of the above, and in a diesel hybrid vehicle capable of increasing the PM regeneration opportunity of the exhaust purification device even during EV travel other than during engine travel and promoting PM regeneration of the exhaust purification device. It is an object of the present invention to provide a regeneration control method for an exhaust purification device.

  In order to solve the above-described problems and achieve the object, a regeneration control method for an exhaust gas purification apparatus in a diesel hybrid vehicle according to claim 1 of the present invention includes a diesel engine, a stepped transmission capable of automatic transmission, A clutch that performs power transmission / reception between the engine and the stepped transmission, a motor generator that assists the engine output by power generation by the engine output or battery power, and for removing particulate matter in the exhaust gas A diesel hybrid comprising an exhaust gas purification device carrying a catalyst on the engine and configured to be able to travel by either engine traveling using only the engine as a driving source or EV traveling using only the motor generator as a driving source In a regeneration control method for an exhaust emission control device in a vehicle, the engine is running and The temperature control of the exhaust purification device is performed when the EV traveling condition is satisfied, and then the engine is stopped and the particulate matter collected in the exhaust purification device during the EV traveling is burned and removed (PM regeneration). It is characterized by.

  Thus, the PM regeneration opportunity of the exhaust purification device is increased during EV travel other than during engine travel, and PM regeneration of the exhaust purification device is further promoted.

  According to a second aspect of the present invention, there is provided a regeneration control method for an exhaust purification device in a diesel hybrid vehicle according to the first aspect, wherein the temperature increase control of the exhaust purification device is low-temperature combustion. To do.

  When this low-temperature combustion control is performed, unburned hydrocarbons (HC) and carbon monoxide (CO) increase in the exhaust gas, so these unburned HC and CO are supplied to the exhaust system. Then, an oxidation reaction occurs in an oxygen atmosphere. Then, since the catalyst bed temperature of the exhaust purification device rises, PM is burned and removed when the temperature becomes equal to or higher than the PM ignition temperature.

  According to a third aspect of the present invention, there is provided an exhaust purification device regeneration control method for a diesel hybrid vehicle according to the first or second aspect, wherein the exhaust purification device avoids overheating or the exhaust purification during the EV traveling. When it is necessary to supply air to the apparatus, the clutch is engaged and air is supplied to the exhaust gas purification apparatus.

  By engaging the clutch and supplying air to the exhaust purification device, the exhaust purification device that has reached a high temperature due to the catalytic reaction (oxidation reaction) is cooled by the air, so that overheating of the exhaust purification device is avoided. In addition, since oxygen is supplied to the oxygen-deficient catalyst, the oxidation reaction is promoted and PM regeneration is promoted.

  According to the regeneration control method for an exhaust purification device in a diesel hybrid vehicle according to the present invention (claim 1), the PM regeneration opportunity of the exhaust purification device can be increased even during EV travel other than during engine travel. PM regeneration can be further promoted.

  Further, according to the regeneration control method for an exhaust purification device in a diesel hybrid vehicle according to the present invention (Claim 2), the catalyst bed temperature of the exhaust purification device can be raised by low-temperature combustion control. The PM can be burned and removed at this stage.

  Further, according to the regeneration control method for an exhaust purification device in a diesel hybrid vehicle according to the present invention (claim 3), by engaging the clutch and supplying air to the exhaust purification device, a catalytic reaction (oxidation reaction) is performed. The exhaust purification device that has reached a high temperature can be cooled by the air, and the exhaust purification device can be prevented from being overheated. Moreover, since oxygen is supplied to the oxygen-deficient catalyst, the oxidation reaction is promoted, and PM regeneration can be promoted.

  Hereinafter, an embodiment of a regeneration control method for an exhaust gas purification apparatus in a diesel hybrid vehicle according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  First, a schematic configuration of a diesel hybrid vehicle that is a front wheel drive vehicle (FF vehicle) will be described with reference to FIG. Here, FIG. 3 is a schematic diagram showing a schematic configuration of the diesel hybrid vehicle.

  The diesel hybrid vehicle 10 is provided with a diesel engine 11 as a travel drive source at the front of the vehicle. In the diesel engine 11, the fuel injection amount is controlled by a common rail fuel injection system (not shown). The intake air amount is detected by an air flow meter (not shown).

  Although not shown in the drawings, the diesel engine 11 is a well-known variable valve timing mechanism (VVT mechanism) that variably controls the opening / closing operation timing of the exhaust valve, or a turbocharger that increases the intake amount using exhaust gas. And an exhaust gas recirculation device (hereinafter referred to as an EGR device) that recirculates part of the exhaust gas to the intake system. Further, in the exhaust passage of the diesel engine 11, an air-fuel ratio (A / F) sensor (not shown) for detecting the air-fuel ratio and an exhaust temperature sensor (exhaust gas temperature downstream of the catalyst to be described later) are detected. Etc.) are provided.

  Further, in the exhaust passage of the diesel engine 11, a particulate filter (hereinafter referred to as a well-known exhaust purification device) carrying a storage reduction type NOx catalyst for purifying PM and nitrogen oxide (NOx) in the exhaust gas. (This is simply referred to as PM trapping device) (not shown).

  Further, pressure sensors (not shown) are provided on the upstream side and the downstream side of the PM collection device in the exhaust passage, respectively, and the amount of PM deposited on the PM collection device is detected by detecting the differential pressure. It is comprised so that can be estimated. The PM trapping device is also provided with a temperature sensor (not shown) for detecting the catalyst bed temperature.

  A driving force generated by the diesel engine 11 is transmitted to a front wheel 13 as a main driving wheel via a stepped transmission (hereinafter referred to as MMT (multimode manual transmission)) 12 and a drive shaft 14 that can be automatically shifted. It is like that. The MMT 12 electrically and automatically controls a gear shift operation by an actuator in accordance with a traveling state. That is, no torque converter is mounted.

  The diesel engine 11 is configured such that its fuel injection amount, intake air amount, and the like are controlled in order to output the requested engine torque commanded from the MMT 12. The required fuel injection amount of the diesel engine 11 is determined based on a map from the engine speed and the accelerator opening, for example, and fuel injection is executed. At this time, a fuel injection amount that does not exceed the smoke limit is determined based on the map from the engine speed and the intake air amount.

  In addition, the diesel hybrid vehicle 10 is provided with a clutch 12a that performs contact / separation of power transmission between the diesel engine 11 and the MMT 12, so that the contact / separation operation is automatically and electrically controlled by an actuator according to the traveling state. It has become.

  Also, a propeller shaft 16 is connected to the transfer 15 that transmits the driving force separately, and a motor generator (MG) 17 integrated with a driving gear device (gear train) is connected to the end of the transfer shaft 15. The rear wheel 18 is configured to be rotated only by the front wheel 13 that is a driving wheel. In the present embodiment, the motor generator 17 is mounted on the rear part of the vehicle via the transfer 15 and the propeller shaft 16; however, the motor generator 17 may be mounted integrally on the MMT 12 without using these.

  The motor generator 17 is connected via an inverter 19 to a battery 20 that is a chargeable / dischargeable secondary battery. Further, the motor generator 17 is configured to be able to take two operation states, a power running operation mode that functions as a motor that is a travel drive source, and a regenerative operation mode that functions as a generator.

  For example, the motor generator 17 receives power supplied from the battery 20 in the power running operation mode and generates power for driving the drive shaft 14 via the propeller shaft 16. In the regenerative operation mode, the motor generator 17 converts the driving force transmitted from the diesel engine 11 or the drive shaft 14 via the propeller shaft 16 into electric power, and charges the battery 20.

  Whether the motor generator 17 is operated in the power running mode or the regenerative operation mode is determined in consideration of the state of charge (SOC) of the battery 20.

  The diesel hybrid vehicle 10 configured as described above is basically controlled as described below together with each component based on output information from the various sensors by an electronic control unit (ECU) (not shown) and travels in various states. be able to.

  For example, in a relatively low speed state in which the diesel hybrid vehicle 10 starts traveling, the vehicle travels (EV traveling) by powering the motor generator 17 while the diesel engine 11 is stopped. Then, when the diesel hybrid vehicle 10 reaches a predetermined speed or load after the start of traveling, the diesel engine 11 is cranked and started using the motor generator 17 and the operation is shifted to the operation using the diesel engine 11.

  During steady operation, the diesel engine 11 is normally operated so as to generate an output substantially equal to the required power of the drive shaft 14. At this time, almost all of the output of the diesel engine 11 is transmitted to the drive shaft 14.

  On the other hand, when the state of charge SOC of the battery 20 has dropped below a predetermined reference value, the diesel engine 11 is operated with an output that exceeds the required power of the drive shaft 14, and a part of the surplus power is a motor. It is regenerated as electric power by the generator 17 and used for charging the battery 20. When the output torque of the diesel engine 11 is insufficient, the insufficient torque is assisted by driving the motor generator 17, and the necessary torque is ensured.

  The diesel hybrid vehicle 10 is also subjected to so-called eco-run (economy & ecology running) control in order to save fuel and reduce exhaust emissions. That is, for example, when the diesel hybrid vehicle 10 stops due to a signal waiting at an intersection or the like, the diesel engine 11 is automatically stopped under a predetermined stop condition, and then the predetermined restart condition (for example, the accelerator pedal is depressed). At a time), the diesel engine 11 is also restarted.

  The above is the basic configuration and basic control operation of the diesel hybrid vehicle 10 according to the present invention.

  Next, a control method which is a main part of the present invention will be described with reference to FIG. Here, FIG. 1 is a flowchart showing a regeneration control method for the PM collection device in the diesel hybrid vehicle.

  First, it is determined whether or not an EV traveling condition is satisfied during engine traveling (step S10). The driving conditions under which EV driving is possible are set in advance by a map or the like according to the output of the motor generator 17 and the SOC of the battery 20, so that the current driving conditions are determined by comparison with this.

  If the EV traveling condition is satisfied (Yes at Step S10), so-called low-temperature combustion control is performed as temperature increase control of the NOx catalyst (Step S20). If the EV traveling condition is not satisfied (No at Step S10), the control may be terminated and PM regeneration during engine traveling may be performed.

  The low temperature combustion refers to the following combustion disclosed in, for example, Japanese Patent No. 3116876. When the amount of exhaust gas (hereinafter referred to as EGR gas) recirculated from the EGR device to the intake system is increased and the amount of EGR gas in the combustion chamber is increased, the amount of PM generated gradually increases and reaches a peak. If the amount of EGR gas in the combustion chamber is further increased, the temperature of the fuel and the surrounding gas during combustion in the combustion chamber becomes lower than the generation temperature of PM, and PM is hardly generated. This refers to combustion when the amount of EGR gas in the combustion chamber is larger than the amount of EGR gas at which the amount of PM generated reaches a peak.

  When low-temperature combustion control is performed in this way, the combustion temperature of the engine decreases, the amount of NOx in the exhaust gas is reduced, and the generation of smoke is suppressed. That is, as the low-temperature combustion control is performed, the amount of unburned hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas increases, so that these unburned HC and CO enter the exhaust system. When supplied, an oxidation reaction takes place in an oxygen atmosphere. Then, since the catalyst bed temperature rises, PM is burned and removed when the temperature becomes equal to or higher than the PM ignition temperature.

  Next, when the low temperature combustion control in step S20 is performed, the diesel engine 11 is stopped and the clutch 12a is disengaged (step S30). Then, exhaust gas generated by engine combustion is not supplied to the PM trapping device, so that the HC and CO react only with oxygen remaining in the catalyst. The extent of the catalyst bed temperature rise described later depends on the reaction based on the amount of HC and CO and the amount of residual oxygen.

  Next, after shifting to the EV running, it is determined whether or not the catalyst bed temperature has risen above a predetermined value (step S40). As shown in FIG. 2, the catalyst bed temperature rise is determined within a certain temperature range, that is, within a range between a lower limit temperature T1 (for example, about 500 ° C.) and an upper limit temperature T2 (for example, about 700 ° C.). Is maintained by monitoring the temperature gradient at any given time. Here, FIG. 2 is a graph showing an example of a temperature change of the catalyst bed temperature.

  For example, in the figure, it is determined whether or not the temperature gradient at point A when Δt time has elapsed from an arbitrary time t exceeds a predetermined upper limit value. That is, this upper limit value is a threshold value for avoiding the catalyst from being melted (thermally deteriorated) when the catalyst bed temperature rises with the temperature gradient. Therefore, the monitoring timing of this temperature gradient is performed as soon as the catalyst bed temperature exceeds the lower limit T1 in consideration of the time lag until the catalyst is actually cooled by the motoring operation in step S100 described later, or It is preferably set to be performed immediately before the lower limit value T1 is exceeded.

  Based on this determination, if the catalyst bed temperature has risen to a predetermined value or higher (Yes at step S40), the clutch of the clutch 12a is engaged, and the piston and intake / exhaust of the diesel engine 11 are not injected. A so-called motoring operation is performed to operate the valve (step S100). As a result, the air sucked into the cylinder of the diesel engine 11 is exhausted without being combusted. Therefore, although the oxidation reaction is promoted by the supply of this air and the catalyst bed temperature rises for a predetermined time, the air causes the catalyst bed to rise. Cooling is performed so that the temperature does not exceed the upper limit temperature T2, and the catalyst is prevented from being melted (thermal deterioration).

  On the other hand, if the catalyst bed temperature has not risen above the predetermined value (No at Step S40), PM regeneration control is performed (Step S50). If this PM regeneration control is continued, eventually the oxidation reaction slows down due to air shortage, that is, oxygen shortage, and as shown by the point B in FIG. 2, the catalyst bed temperature decreases and PM regeneration slows down. come.

  Therefore, it is next determined whether or not the catalyst is short of air, that is, whether or not the catalyst bed temperature has decreased (step S60). If the catalyst bed temperature has not decreased (No at Step S60), the process jumps to Step S90 to continue the PM regeneration control (Step S90).

  If the catalyst bed temperature decreases (Yes at step S60), the oxidation reaction has slowed down due to air shortage. Therefore, the clutch 12a is engaged, the motoring operation is performed, air is supplied to the catalyst, and the oxidation reaction is performed. Is promoted (step S70).

  Then, as a result of this motoring operation, it is determined whether or not the oxidation reaction has been promoted and the catalyst bed temperature has increased (step S80). If the catalyst bed temperature has not risen (No at Step S80), the oxidation reaction is not slowed down due to air shortage, but the amount of HC and CO has become insufficient as shown by the temperature gradient at point B in FIG. The reaction is considered to have slowed down, and the control is terminated in preparation for the increase control of HC and CO by the next low temperature combustion (see step S20).

  On the other hand, if the catalyst bed temperature has risen as a result of the air supply by motoring operation (Yes at step S80), the oxidation reaction has been slowed only by air shortage, so PM regeneration control is continued (step S90). ) This routine is repeatedly executed until the process returns to step S60 and the catalyst bed temperature decreases.

  The above control routine (steps S10 to S100) is repeatedly executed at predetermined time intervals, and a well-known PM regeneration control is executed when the engine is running. Therefore, by performing the control according to the present embodiment, the PM regeneration control can be executed even during EV traveling other than during engine traveling, so that the opportunity for PM regeneration is increased and the PM regeneration of the PM trapping device is promoted. Can do.

  In the above embodiment, it has been described that the low temperature combustion control (step S20) in which the engine air-fuel ratio becomes rich after the EV running condition is satisfied (Yes in step S10), but instead of this control, for example, As shown in step S25 of FIG. 4, low temperature combustion is performed until the engine air-fuel ratio becomes lean, and control is performed so that the temperature of the catalyst is raised in an oxygen atmosphere by adding fuel to the exhaust system. In addition, it is possible to expect the same effect as that of the above embodiment.

  The exhaust system is, for example, an exhaust passage upstream of the catalyst, an exhaust port of an engine, or an exhaust manifold, and piping and a fuel addition valve for adding fuel to the exhaust system are provided. Since the control operation in other steps is the same as that in the above embodiment, a duplicate description is omitted. Here, FIG. 4 is a flowchart showing another control method, and the same reference numerals are given to the same steps as the control steps of the above embodiment.

  In the above-described embodiment, the example in which the present invention is applied to the particulate filter carrying the NOx storage reduction catalyst has been described. However, the present invention is not limited to this, and the present invention is applied to the particulate filter carrying the oxidation catalyst. You can also.

  As described above, the exhaust gas purification device regeneration control method for a diesel hybrid vehicle according to the present invention is useful for a diesel hybrid vehicle equipped with an exhaust gas purification device carrying a catalyst in order to burn and remove particulate matter in exhaust gas. In particular, it is suitable for control that increases the PM regeneration opportunity of the exhaust purification device even during EV travel other than during engine travel and promotes PM regeneration of the exhaust purification device.

It is a flowchart which shows the PM reproduction | regeneration control method of PM collection apparatus in a diesel hybrid vehicle. It is a graph which shows an example of the temperature change of catalyst bed temperature. It is a mimetic diagram showing a schematic structure of a diesel hybrid vehicle. It is a flowchart which shows the other control method.

Explanation of symbols

10 Diesel hybrid vehicle 11 Diesel engine 12 MMT
12a Clutch 17 Motor generator 20 Battery

Claims (3)

A diesel engine, a stepped transmission capable of automatic transmission, a clutch for connecting and disconnecting power transmission between the engine and the stepped transmission, and assisting the engine output by power generation or battery power by the engine output A motor generator and an exhaust purification device carrying a catalyst to remove particulate matter in the exhaust gas;
In the regeneration control method for an exhaust purification device in a diesel hybrid vehicle configured to be able to run by either engine running using only the engine as a drive source or EV running using only the motor generator as a drive source,
Particulate matter collected in the exhaust gas purification device during the EV running after the engine is running and the temperature control of the exhaust gas purification device is performed when the EV running condition is satisfied, and then the engine is stopped A method for controlling the regeneration of an exhaust emission control device in a diesel hybrid vehicle, characterized in that combustion is removed.   The method for controlling regeneration of an exhaust purification device in a diesel hybrid vehicle according to claim 1, wherein the temperature raising control of the exhaust purification device is low-temperature combustion.   When the exhaust purifying device avoids overheating or needs to supply air to the exhaust purifying device during the EV traveling, the clutch is engaged to supply air to the exhaust purifying device. Item 3. A method for controlling regeneration of an exhaust purification device in a diesel hybrid vehicle according to Item 1 or 2.

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