JP2008002376A - Engine system for hybrid vehicles - Google Patents

Abstract

Provided is a technique capable of suppressing deterioration in performance of an exhaust purification device even when scavenging control is performed when an internal combustion engine of a hybrid vehicle is stopped.
An exhaust pipe of an internal combustion engine of a hybrid vehicle is provided with an O ₂ sensor, an exhaust switching valve, a three-way catalyst, and a bypass pipe that bypasses the three-way catalyst. A catalyst 16 is provided. When the O ₂ sensor 12 detects that excessive oxygen exhaust gas has passed during scavenging control by the motor generator 3, the exhaust gas switching valve 10 is operated to allow the exhaust gas to pass through the bypass pipe 6.
[Selection] Figure 1

Description

  The present invention relates to a control device for a hybrid engine having a plurality of drive sources including an internal combustion engine and an electric motor, and more particularly to a system for improving the function of an exhaust purification device provided in an exhaust passage of the internal combustion engine.

  A hybrid engine in which an internal combustion engine and an electric motor are combined as a plurality of drive sources has a function of appropriately transmitting the power generated from these drive sources to the outside while controlling the operating state of each drive source. If the hybrid engine system is used, for example, the output of the internal combustion engine is preferentially used in an operation region where the energy conversion efficiency by engine combustion is high, and the electric motor output is preferentially used in the operation region where the energy conversion efficiency by engine combustion is low. Control such as utilization can be performed. As a result, a vehicle equipped with a hybrid engine can significantly reduce the amount of fuel consumed and the amount of exhaust gas discharged during vehicle operation compared to a vehicle equipped with a conventional internal combustion engine.

  When the internal combustion engine is stopped while the hybrid engine is running, there is a case where a control for forcibly reducing the rotation of the internal combustion engine with an electric motor is performed. In this case, part of the exhaust gas remains in the cylinder after the internal combustion engine is stopped. Then, when the engine is stopped, the atmospheric temperature in the cylinder becomes high, and deposits may be generated at, for example, the nozzle part of the fuel injection valve. On the other hand, after the fuel supply to the internal combustion engine is stopped, the internal combustion engine in the non-combustion state is controlled by the electric motor for a predetermined period to exhaust the exhaust gas completely from the cylinder, Has been proposed (hereinafter referred to as “scavenging control”).

  As a technique related to this, a technique has been proposed in which the opening of the throttle valve is throttled in conjunction with the scavenging control to suppress an increase in the oxygen storage amount of the three-way catalyst in the catalytic converter accompanying the scavenging control. (For example, refer to Patent Document 1).

Here, when the above scavenging control is performed, exhaust gas at a high temperature is introduced into the exhaust gas purification device and the oxygen excess state occurs during the scavenging, so that the temperature of the exhaust gas purification device may become excessively high and deteriorate. was there.
JP 2004-19519 A

  The present invention has been made in view of the above prior art, and an object of the present invention is to suppress deterioration in the performance of the exhaust purification device even when scavenging control is performed when the internal combustion engine of the hybrid vehicle is stopped. It is to provide technology that can.

  In order to achieve the above object, the present invention comprises a bypass passage for bypassing an exhaust purification device and an auxiliary exhaust purification device provided in the bypass passage in an exhaust passage of an internal combustion engine of a hybrid vehicle. The greatest feature is that it passes through the bypass.

More specifically, an internal combustion engine,
A motor generator;
An exhaust purification device that is provided in an exhaust passage of the internal combustion engine and purifies exhaust gas passing through the exhaust passage;
A bypass path for bypassing the exhaust gas purification apparatus to exhaust gas passing through the exhaust path by communicating the upstream side and the downstream side of the exhaust gas purification apparatus in the exhaust path;
An auxiliary exhaust purification device that is provided in the bypass passage and purifies exhaust gas passing through the bypass passage;
Flow rate control means for controlling whether the exhaust gas that passes through the exhaust passage passes through the exhaust gas purification device or the bypass passage;
Scavenging means for forcibly rotating the crankshaft of the internal combustion engine a predetermined number of times by the motor generator to scavenge the exhaust gas in the cylinder of the internal combustion engine when the internal combustion engine stops;
An engine system for a hybrid vehicle equipped with
During the scavenging of the exhaust gas by the scavenging means, the flow rate control means allows the exhaust gas passing through the exhaust passage to pass through the bypass path.

  According to this, during the scavenging of the exhaust gas by the scavenging means, it is possible to suppress the introduction of the high-temperature exhaust gas and the excessive oxygen exhaust gas into the exhaust gas purification device, and it is possible to suppress the excessive temperature rise of the exhaust gas purification device. In addition, since the auxiliary exhaust purification device is provided, it is possible to suppress deterioration of the exhaust emission purification rate when the exhaust gas passes through the bypass path.

Note that the fact that the exhaust gas is being scavenged by the scavenging means may be detected by an O ₂ sensor, an HC concentration sensor, an exhaust gas temperature sensor, or a combination thereof provided in the exhaust passage.

Further, the exhaust purification device means an exhaust purification catalyst such as a three-way catalyst and a NOx storage reduction catalyst and / or a filter that collects particulates in the exhaust. The auxiliary exhaust purification device may also be an exhaust purification catalyst such as a three-way catalyst or a NOx storage reduction catalyst and / or a filter that collects particulates in the exhaust, and has a smaller capacity than the exhaust purification device. Also good.

  Moreover, in this invention, you may make it further provide the cooling device which cools the exhaust_gas | exhaustion which passes the said bypass path in the upstream of the said auxiliary exhaust purification apparatus in the said bypass path. If it does so, it can control that the auxiliary exhaust gas purification device provided in the bypass way overheats.

In the present invention, the cooling device includes a heat exchanger that recovers heat of the exhaust gas that passes through the bypass passage, and a heat storage device that stores heat of the exhaust gas recovered by the heat exchanger. ,
The heat of the exhaust gas stored in the heat storage device may be used for warming up the internal combustion engine.

  In this case, the heat recovered from the exhaust gas when the exhaust gas passing through the bypass passage is cooled can be used for engine warm-up at the time of starting, so that the energy of the exhaust gas can be used effectively.

  The means for solving the above-described problems of the present invention can be used in combination as much as possible.

  In the present invention, even when the scavenging control is performed when the internal combustion engine of the hybrid vehicle is stopped, the deterioration of the performance of the exhaust emission control device can be suppressed.

The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  FIG. 1 shows a schematic configuration of an internal combustion engine 1, a control system, and an exhaust system in the present embodiment. The internal combustion engine 1 is provided with a motor generator 3 having both a function as an electric motor that outputs power via a clutch 2 and a function as a generator that generates electric power using the power output from the internal combustion engine 1. ing. The motor generator 3 also functions as a driving force source or a prime mover for the vehicle.

An exhaust pipe 5 is connected to the internal combustion engine 1. The exhaust pipe 5 is provided with an O ₂ sensor 12 for detecting the oxygen concentration in the exhaust and an exhaust temperature sensor 13 for detecting the temperature of the exhaust. A three-way catalyst 17 for purifying HC, CO, and NOx in the exhaust is provided downstream of the exhaust pipe 5. An upstream side and a downstream side of the three-way catalyst 17 in the exhaust pipe 5 are communicated with each other by a bypass pipe 6. The bypass pipe 6 is provided with a sub-catalyst 16 for exhaust purification. In addition, an exhaust switching valve 10 is provided at a branch portion between the exhaust pipe 5 and the bypass pipe 6 to select whether the three-way catalyst 17 or the bypass pipe 6 passes through the exhaust gas flowing from the upstream side of the exhaust pipe 5. It is possible. In the above, the sub-catalyst 16 corresponds to an auxiliary exhaust purification device, and the exhaust switching valve 10 corresponds to a flow rate control means.

The internal combustion engine 1 configured as described above and its exhaust system are provided with an electronic control unit (ECU) 20 for controlling the internal combustion engine 1 and the exhaust system. The ECU 20 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the driver's request, and performs control related to the exhaust gas purification device 10 of the internal combustion engine 1.

The ECU 20 includes an O ₂ sensor 12 and an exhaust temperature sensor 13 in addition to sensors related to control of the operating state of the internal combustion engine 1 such as a crank position sensor, an accelerator position sensor, and an air flow meter that detects the intake air amount. An output signal is input to the ECU 20 through electrical wiring. On the other hand, a fuel injection valve (not shown) in the internal combustion engine 1 is connected to the ECU 20 via an electric wiring, and an exhaust gas switching valve 10 in this embodiment is connected via an electric wiring and is controlled by the ECU 20. It is like that.

  The ECU 20 includes a CPU, a ROM, a RAM, and the like. The ROM stores a program for performing various controls of the internal combustion engine 1 and a map storing data. A scavenging flow path switching routine, which will be described later, is also one of the programs stored in the ROM of the ECU 20.

  When the internal combustion engine 1 is stopped during traveling in the hybrid system as described above, the motor generator 3 may be controlled to forcibly reduce the rotation of the internal combustion engine 1 to stop it. In this case, after the internal combustion engine 1 is stopped, a part of the exhaust gas remains in the cylinder. As a result, while the engine is stopped, the atmospheric temperature in the cylinder becomes high, and for example, deposits may be generated at the injection port portion of a fuel injection valve (not shown).

  On the other hand, when the internal combustion engine 1 is stopped, after the fuel supply to each cylinder (not shown) is stopped (or before and after the stop), the crankshaft (not shown) is rotated by using the power of the motor generator 3 to A control (scavenging control) for scavenging the exhaust gas in the combustion chamber is performed by gradually decreasing the rotational speed of the shaft to reach a complete stop.

When the scavenging control is performed, the power of the motor generator 3 is transmitted to the crankshaft of the internal combustion engine 1 via the clutch 2 to assist the rotation operation of the crankshaft. For this reason, the rapid fall of the engine speed accompanying the stop of the internal combustion engine 1 is suppressed.

  Then, after the fuel supply to the internal combustion engine 1 is stopped, the crankshaft is rotated until exhaust gas having a high temperature is completely exhausted from each cylinder, so that exposure of the components in each cylinder to high temperatures can be suppressed.

  However, conventionally, when the above scavenging control is performed, the high temperature exhaust gas is introduced into the downstream three-way catalyst, and further, the oxygen-excess air is introduced into the three-way catalyst by the scavenging control. There was a risk of overheating.

  Therefore, in this embodiment, when the scavenging control is being performed, the exhaust gas switching valve 10 is operated to introduce the exhaust gas from the internal combustion engine 1 into the bypass pipe 6 and not into the three-way catalyst 17. It was.

  FIG. 2 shows a flowchart of the scavenging flow path switching routine in the present embodiment. This routine is a routine executed by the ECU 20 every predetermined period while the internal combustion engine 1 is in operation.

  When this routine is executed, it is first determined in S101 whether an engine stop request has been issued. Specifically, it may be determined by reading whether the engine stop request flag that is turned on when the engine stop request is issued in the ECU 20 is turned on. Here, if it is determined that the engine stop request has not been issued, this routine is temporarily terminated as it is. On the other hand, if it is determined that an engine stop request has been issued, the process proceeds to S102.

  In S102, it is determined whether the engine stop request in S101 is due to ignition off. Specifically, it is determined by reading the output signal of the ignition switch into the ECU 20. This is to determine whether the engine stop request in S101 is due to the driver turning off the ignition or is automatically issued when the vehicle is stopped. If it is determined that the engine stop request is due to the ignition off, the process proceeds to S109. On the other hand, if it is determined that it is automatically issued when the vehicle stops, the process proceeds to S103.

  In S103, fuel cut is performed and VVT (not shown) is controlled to the most retarded angle side. Thereby, the combustion in each cylinder of the internal combustion engine 1 is stopped. Further, by controlling the VVT to the most retarded angle side, the intake air introduced into each cylinder of the internal combustion engine 1 during the scavenging control is blown back and does not flow backward to the intake side. When the process of S103 ends, the process proceeds to S104.

  In S104, scavenging control is started. Specifically, the driving force of the motor generator 3 is transmitted to the internal combustion engine 1 via the clutch 2, and a crankshaft (not shown) is forcibly rotated. The ECU 20 that executes the process of S104 corresponds to a scavenging means. When the process of S104 ends, the process proceeds to S105.

In S105, it is determined whether the exhaust gas is in an excessive oxygen state. Specifically, the oxygen concentration of the exhaust gas passing through the exhaust pipe 5 is detected by the O ₂ sensor 12, and it is determined whether or not the detected oxygen concentration is equal to or greater than a threshold value. Here, when it is determined that the exhaust gas is not in an excessive oxygen state, it is determined that the excessive oxygen exhaust gas by the scavenging control has not reached at least the location where the O ₂ sensor 12 is installed in the exhaust pipe 5. The process of S105 is repeated until it is determined that the exhaust gas is in an excessive oxygen state. If it is determined in S105 that the exhaust gas is in an excessive oxygen state, the excessive oxygen exhaust gas by the scavenging control reaches at least the installation location of the O ₂ sensor 12 in the exhaust pipe 5, and the scavenging control is started in the cylinder. Since it is presumed that the high-temperature exhaust gas existing at the upstream of the branch point between the exhaust pipe 3 and the bypass pipe 6 is present, the process proceeds to S106.

  In S <b> 106, the exhaust gas switching valve 10 is operated and exhaust gas is introduced into the bypass pipe 6. When the process of S106 ends, the process proceeds to S107.

  In S107, it is determined whether or not the scavenging control is finished. For example, in the scavenging control of this embodiment, when the crankshaft is forcibly rotated 10 times by the motor generator 3 after the fuel supply to the cylinder is stopped, here, after the scavenging control is started in S104, the crankshaft is controlled. Is determined whether it has rotated 10 times. If the crankshaft has not rotated 10 times, it is determined that the scavenging control has not been completed, and the process proceeds to S107. As described above, the process of S107 is repeatedly executed until it is determined that the scavenging control has been completed. If it is determined in S107 that the scavenging control has been completed, the process proceeds to S108.

  In S108, the exhaust switching valve 10 switches the flow path so that the three-way catalyst 17 passes through the exhaust flowing from the upstream of the exhaust pipe 5. When the process of S108 ends, this routine is temporarily ended.

  Returning to S102, if it is determined that the current engine stop request is due to the ignition off, the process proceeds to S109. In S109, first, fuel cut and VVT maximum retardation processing are executed. The content of the process is the same as S103. When the process of S109 ends, the process proceeds to S110.

  In S110, the internal combustion engine is forcibly stopped by the motor generator 3. Specifically, the rotation of the crankshaft is forcibly stopped by the motor generator 3 while the crankshaft rotates twice after the fuel supply to the cylinder is stopped. When the processing of S110 ends, this routine is once ended.

  As described above, in this embodiment, the scavenging control is being performed, and it is determined that the high-temperature exhaust gas and the excessive oxygen exhaust gas that has passed thereafter pass through the upstream side of the three-way catalyst 17. Then, the exhaust gas is introduced into the bypass pipe 6 by the operation of the exhaust gas switching valve 10. As a result, high-temperature exhaust gas and oxygen-exhaust exhaust gas are introduced into the three-way catalyst 17, and the three-way catalyst 17 can be prevented from being excessively heated.

In S105 described above, whether or not the exhaust gas is in an excessive oxygen state is detected by the output signal of the O ₂ sensor 12, but in addition to this, the output signal of the exhaust temperature sensor 13 is acquired and the temperature of the exhaust gas decreases. It may be detected whether or not. If it does so, it can be determined more reliably whether the exhaust gas of excess oxygen which is not combusting is passing by scavenging control. Further, instead of the O ₂ sensor 12, an HC sensor that detects the HC concentration in the exhaust gas may be used.

  Next, a second embodiment of the present invention will be described. In this embodiment, a heat exchanger and a heat storage device are provided on the upstream side of the sub-catalyst in the bypass pipe, and the sub-catalyst is prevented from being overheated by high-temperature exhaust gas, and the exhaust energy is effectively used. Will be described.

  FIG. 3 shows a schematic configuration of the internal combustion engine 1, the control system, and the exhaust system in the present embodiment. In the present embodiment, the same components as those illustrated in FIG. 1 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 3, in the exhaust system of the internal combustion engine 1 in the present embodiment, a heat exchanger 22 is provided upstream of the sub catalyst 16 in the bypass pipe 6. The heat exchanger 22 is provided with a heat medium circulation path 23 so that heat can be exchanged between the exhaust gas passing through the bypass pipe 6 and the heat medium. Further, a heat storage device 24 is connected to the heat medium circulation path 23 so as to be able to exchange heat, and heat of exhaust gas passing through the bypass pipe 6 can be stored in the heat storage device 24.

  A cooling water passage (not shown) is connected to the heat storage device 24 so that heat can be exchanged. When the internal combustion engine 1 is cold-started, the cooling water is led to the heat storage device 24 and the energy of the exhaust gas stored in the heat storage device 24 is stored. Thus, the warm-up of the internal combustion engine 1 is promoted.

  As described above, in the present embodiment, the heat exchanger 22 is provided upstream of the sub catalyst 16 in the bypass pipe 6, and the exhaust gas passing through the bypass pipe 6 and the heat medium exchange heat, thereby Is supposed to cool. Accordingly, it is possible to suppress the high-temperature exhaust gas from being introduced into the sub catalyst 16 as it is, and to suppress the excessive temperature rise of the sub catalyst 16.

  Further, the energy recovered from the exhaust is used for warming up the internal combustion engine 1 during a cold start via the heat storage device 24. Therefore, the exhaust energy can be effectively reused. In the above, the heat exchanger 22, the heat medium circulation path 23, and the heat storage device 24 correspond to a cooling device in this embodiment.

  In the present embodiment, an example in which heat exchange is performed between the exhaust gas passing through the bypass pipe 6 and the heat medium in the heat exchanger 22 and heat collected from the exhaust gas is stored in the heat storage device 24 has been described. On the other hand, in the heat exchanger 22, for example, heat exchange may be performed between the exhaust gas passing through the bypass pipe 6 and the cooling water, and only the exhaust gas may be cooled. Also by this, it is possible to suppress the high-temperature exhaust gas from being introduced into the sub catalyst 16 as it is, and it is possible to suppress the excessive temperature increase of the sub catalyst 16.

1 is a diagram illustrating a schematic configuration of an internal combustion engine, a control system, and an exhaust system according to Embodiment 1 of the present invention. It is a flowchart which shows the flow path switching routine at the time of scavenging concerning Example 1 of this invention. It is a figure which shows schematic structure of the internal combustion engine and intake / exhaust system which concern on Example 2 of this invention.

Explanation of symbols

1 ... internal combustion engine 2 ... clutch 3 ... motor-generator 5 ... exhaust pipe 6 ... bypass pipe 10 ... exhaust switching valve 12 ... _{O 2} sensor 13 ... exhaust gas temperature sensor 16 ... Sub-catalyst 17 ... Three-way catalyst 20 ... ECU
22 ... Heat exchanger 23 ... Heat medium circulation path 24 ... Heat storage device

Claims (3)

An internal combustion engine;
A motor generator;
An exhaust purification device that is provided in an exhaust passage of the internal combustion engine and purifies exhaust gas passing through the exhaust passage;
A bypass path for bypassing the exhaust gas purification apparatus to exhaust gas passing through the exhaust path by communicating the upstream side and the downstream side of the exhaust gas purification apparatus in the exhaust path;
An auxiliary exhaust purification device that is provided in the bypass passage and purifies exhaust gas passing through the bypass passage;
Flow rate control means for controlling whether the exhaust gas that passes through the exhaust passage passes through the exhaust gas purification device or the bypass passage;
Scavenging means for forcibly rotating the crankshaft of the internal combustion engine a predetermined number of times by the motor generator to scavenge the exhaust gas in the cylinder of the internal combustion engine when the internal combustion engine stops;
An engine system for a hybrid vehicle equipped with
During the scavenging of the exhaust gas by the scavenging means, the flow rate control means allows the exhaust gas passing through the exhaust passage to pass through the bypass path.   2. The engine system for a hybrid vehicle according to claim 1, further comprising a cooling device that cools exhaust gas that passes through the bypass passage upstream of the auxiliary exhaust purification device in the bypass passage. The cooling device includes a heat exchanger that recovers heat of exhaust gas that passes through the bypass passage, and a heat storage device that stores heat of the exhaust gas recovered by the heat exchanger,
The engine system for a hybrid vehicle according to claim 2, wherein the heat of the exhaust gas stored in the heat storage device is used to warm up the internal combustion engine.

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