JP4788531B2 - Engine control device - Google Patents

Description

  The present invention can perform various engine controls including a control for reducing torque shock or vibration generated when starting an engine in a hybrid vehicle using a motor and an engine as a prime mover, an idle stop vehicle, or the like with a compact device. It relates to the improved technology.

In a hybrid vehicle, when the engine is switched to the engine drive mode while driving with the driving force of only the motor, the engine starts regardless of the driver's intention, and in an idle stop vehicle, the engine is stopped by waiting for a signal, etc. When restarting, restart the engine with the starter motor.
Here, at the time of start (cranking), since the rotation is extremely low, the intake negative pressure does not develop even when the throttle valve is closed, and the air close to the atmospheric pressure is sucked into the cylinder. The generated torque becomes large and the occupant may be given an uncomfortable torque shock or vibration.

In order to prevent such torque shock or vibration, in the device described in Patent Document 1, in an idle stop vehicle, the air in the intake manifold is sucked by the negative pressure tank immediately before the engine is started, and the intake manifold is negatively pressurized ( By starting the engine in a state set to a pressure lower than the atmospheric pressure), the amount of air flowing into the cylinder is reduced and the generated torque is reduced.
JP 2003-172237 A

However, in the apparatus described in Patent Document 1, the amount of air sucked from the intake passage downstream of the throttle valve by the negative pressure tank is almost proportional to the volume of the negative pressure tank, so that torque shock or vibration can be prevented. When trying to obtain a sufficient negative pressure, the negative pressure tank is enlarged and the space of the engine room is impaired.
The present invention has been made in view of the above-described conventional problems, and has a compact configuration using a general device for performing various engine controls in a vehicle-mounted engine, and a torque shock at engine startup. Or it aims at enabling it to reduce a vibration.

Therefore, according to the present invention, in an engine provided with a throttle valve in the intake passage and an exhaust purification catalyst in the exhaust passage, a first passage having one end communicating with the atmosphere and a first passage communicating with the intake passage downstream of the throttle valve. Two passages, and a third passage having one end communicating with the exhaust passage upstream of the exhaust purification catalyst and interposing an electric air pump, the other ends of these passages being joined together, A passage switching valve is provided at the junction so that the first passage and the second passage can be selectively communicated with the third passage, while at the time of engine start request, before cranking starts , By connecting the second passage and the third passage by the passage switching valve and driving the air pump, the air in the intake passage downstream of the closed throttle valve is allowed to pass through the second passage and the third passage. Excretion And discharged to the passage, the start of the throttle valve downstream engine to start cranking the intake passage in a state with the negative pressure, after starting the engine, the secondary time air supply request for the exhaust gas purifying catalyst activity, By connecting the first passage and the third passage by the passage switching valve and driving the air pump, the atmosphere is supplied as secondary air to the exhaust passage through the first passage and the third passage, When the exhaust gas recirculation request is made in the exhaust purification catalyst active state, the second switching passage is communicated with the third passage by the passage switching valve, and a part of the exhaust gas is exhausted from the exhaust passage through the second passage and the third passage. It was set as the structure controlled to recirculate | reflux to the said intake passage.

With the above configuration, at the time of engine start request, before the cranking starts , the air in the intake passage downstream of the closed throttle valve is discharged by the air pump to the exhaust passage through the second passage and the third passage, Since cranking is started after the intake passage is set to a sufficiently large negative pressure state (a state where the pressure is sufficiently low), the torque generated at the time of engine start is kept small, and torque shock or vibration can be prevented. .

Further, when secondary air supply is requested after startup and when exhaust gas recirculation (EGR) is requested, these controls can be performed without any problem by switching the passages and controlling the air pump as described above.
The air pump, the first passage, and the third passage are provided as a basic secondary air system, and an EGR passage configured by connecting an exhaust passage and an intake passage downstream of the throttle valve is provided as a second. Since it can be composed of a passage and a third passage, it is only necessary to add a passage switching valve to the general engine control device including the secondary air system and the EGR device for switching control. A large negative pressure tank as in Document 1 is not required and a compact configuration is not required, and the space in the engine room is not impaired.

Embodiments of an engine control apparatus according to the present invention will be described below.
The configuration of the present invention is mounted on a hybrid vehicle, an idle stop vehicle, or the like. In the following embodiment, a configuration of a hybrid vehicle will be described.
FIG. 1 shows a system configuration of a first embodiment which is a basic form of the present invention.
In FIG. 1, intake air taken into the engine 2 via the intake passage 4 is sequentially an air cleaner 6 that removes foreign matter from the intake air, an air flow meter 8 that detects an intake air flow rate for air-fuel ratio control of the engine 2, 4 is led to the cylinder 2a of the engine 2 through an electronically controlled throttle valve 10 that adjusts the intake air flow rate.

The exhaust discharged from the cylinder 2a to the exhaust passage 14 is purified by an exhaust purification catalyst 18 such as a three-way catalyst interposed in the exhaust passage 14, and then released to the atmosphere.
A first passage 20 having one end communicating with a portion of the intake passage 4 downstream of the air cleaner 6 and upstream of the air flow meter 8, a second passage 22 having one end communicating with the downstream portion of the throttle valve 10, and an exhaust passage 14 The upstream portion (manifold portion) of the catalyst 18 and the third passage 24 having one end communicating with each other are arranged by joining the other ends of the respective passages at the joining portion 26. In the present embodiment, one end of the third passage 24 is configured to communicate with each branch portion branched to each cylinder of the exhaust passage 14. Of course, you may comprise so that it may communicate.

The merging portion 26 is provided with an electromagnetically driven three-way valve 28 as a passage switching valve. By the three-way valve 28, the first passage 20 and the second passage 22 are selectively transferred to the third passage 24. And free communication. Further, the three-way valve 28 is configured to be capable of simultaneously closing the first passage 20 and the second passage 22 (blocking from the third passage 24).
Furthermore, an electric air pump 30 is provided in the third passage 24. As the air pump 30, a general secondary air supply system may be used. In the present embodiment, air is supplied in the forward direction in which secondary air is supplied (from the three-way valve 28 side to the exhaust passage 14 side). Driving direction).

A motor 34 is connected to the engine 2 via a clutch 32, and a transmission 36 is connected to an output shaft of the motor 34. An output of the transmission 36 is transmitted to an axle (not shown). A power train for a hybrid vehicle is configured.
The control unit 38 includes an intake air flow signal from the air flow meter 8, an accelerator opening signal from an accelerator opening sensor 40 that detects the amount of depression of the accelerator pedal (vehicle driving force request), and a crank that detects the engine speed. The crank angle signal from the angle sensor 42, the vehicle speed signal from the vehicle speed sensor 44 that detects the vehicle speed, the coolant temperature signal from the water temperature sensor 46 that detects the coolant temperature of the engine 2, and the temperature of the catalyst 18 (active state). The catalyst temperature signal from the catalyst temperature sensor 48 for detecting the above is input. The catalyst temperature sensor 48 may be omitted, and the temperature detection (activity determination) of the catalyst 18 may be performed by the water temperature sensor 46.

The control unit 38 also issues a drive command to the air pump 30 and a passage switching command to the three-way valve 28.
Next, the control of the present embodiment by the control unit 38 will be described with reference to the flowchart of FIG.
In step S1, it is determined whether the engine 2 is in a stopped state.

If it is determined that the engine 2 is in a stopped state, the process proceeds to step S2, and it is determined whether there is a request for starting the engine 2 according to the current traveling state, based on detection signals from the accelerator opening sensor 40, the vehicle speed sensor 44, and the like.
If it is determined in step S2 that there is a request to start the engine, the process proceeds to step S3, and the air pump 30 is driven in a state where the three-way valve 28 is in a position where the second passage 22 and the third passage 24 communicate with each other. Note that the throttle valve 10 is closed before the engine 2 is started.

By driving the air pump 30, the air in the intake passage 4 (downstream portion from the throttle valve 10) is exhausted through the second passage 22 and the third passage 24 that are in communication with each other, as indicated by an arrow A in FIG. The pressure is fed to the passage 14 and the negative pressure in the intake passage 4 is developed.
In step S4, the pressure in the intake passage 4 downstream of the throttle valve is detected, or the elapsed time from the start of driving the air pump 30 is detected. Determine if it has reached a state.

If it is determined in step S4 that the sufficient negative pressure state has been reached, the routine proceeds to step S5, where the engine 2 is started (cranked). The engine 2 may be started by a dedicated starter motor, but may be configured such that the transmission 36 is neutral, the clutch 32 is connected, and the traveling motor 34 is used.
Thus, the engine 2 is started after the intake passage 4 is in a negative pressure state greater than or equal to a predetermined level and the amount of intake air to the cylinder 2a is sufficiently reduced. Shock or vibration can be prevented.

  After engine 2 is started (cranking) in step S5, the process proceeds to step S6 to determine whether the start is completed (complete explosion). If it is determined that the start is completed, the process proceeds to step S7, and the three-way valve 28 Is controlled to close the second passage 22, stop driving the air pump 30, and release the negative pressure control. The driving of the air pump 30 may be stopped when it is determined that the driving is unnecessary in the control described later after the engine 2 is started.

After the engine 2 has been started, the determination in step S1 is NO and the process proceeds to step S11 to determine whether or not the catalyst 18 has reached the predetermined temperature for activity determination.
When it is determined in step S11 that the catalyst 18 is in an inactive state below the predetermined temperature, the process proceeds to step S12 to activate the catalyst 18, so that the three-way valve 28 communicates with the first passage 20 and the third passage 24. And the air pump 30 is driven to supply the atmosphere as secondary air to the exhaust passage 14 via the first passage 20 and the third passage 24 that are in communication with each other, as indicated by an arrow B in FIG. The catalyst 18 is warmed up and activated. Here, since the air flow meter 8 is disposed downstream of the connection point of the first passage 20 to the intake passage 4, the air flow meter 8 does not detect the secondary air supply and flows into the cylinder 2a. Since only the air flow amount to be detected is detected, good air-fuel ratio control can be maintained.

Then, the catalyst 18 is circulated through the steps S1, S11, and S12 until the catalyst 18 is determined to be in an active state at a predetermined temperature or higher in step S11, and the warming up of the catalyst 18 by driving the air pump 30 is continued.
Thereafter, if it is determined in step S11 that the catalyst 18 is in an active state of a predetermined temperature or higher, the process proceeds to step S13, and when the secondary air is being supplied, the determination in step S13 is YES and the process proceeds to step S14. The drive is released, the secondary air supply is stopped, and the first passage 20 is closed.

As described above, the catalyst 18 is changed from the inactive state to the active state, and the secondary air supply is stopped. Then, the process proceeds to step S15 to determine whether the exhaust gas recirculation (EGR) condition is satisfied based on the engine operating state. .
If it is determined in step S15 that the EGR condition is satisfied (a condition that satisfies the condition for performing EGR), the process proceeds to step S16, and the three-way valve 28 is switched to a position where the second passage 22 communicates with the third passage 24. As shown by an arrow C, EGR is performed by recirculating a part of the exhaust gas from the exhaust passage 14 to the intake passage 4 (portion downstream from the throttle valve 10) via the second passage 22 and the third passage 24. With this EGR, the combustion temperature of the engine 2 is lowered, so that the emission amount of nitrogen oxides can be suppressed. In addition, if the EGR control valve whose opening degree is continuously variable together with the opening / closing function is provided in the second passage 22, the EGR amount can be controlled with high accuracy, but the opening degree of the second passage 22 is continuously connected to the three-way valve 28. If the function of the EGR control valve is provided so that it can be adjusted automatically, highly accurate EGR amount control can be performed with a minimum configuration without providing a separate EGR control valve.

When it is determined in step S15 that the EGR condition is not satisfied, in this state (the first passage 20 and the second passage 22 are both closed and the air pump 30 is stopped driving), this routine is terminated and the operation is performed without performing the EGR.
Further, when the catalyst 18 at the time of starting the engine 2 is already in an active state and secondary air supply is unnecessary (for example, when the engine 2 is restarted in a short time after the engine is stopped), the process does not go through step S12. Proceeding to S13, the determination in step S13 is NO, and the process proceeds to step S15 without performing the secondary air supply control, and based on the EGR condition determination, the process proceeds to step S16 to perform the EGR control.

As described above, according to this embodiment, the engine 2 is started by sucking and discharging the air in the intake passage 4 by the air pump 30 without using a large negative pressure tank as in the prior art (Patent Document 1). The torque generated at the time can be made sufficiently small, and torque shock and vibration can be suppressed.
The basic secondary air supply system is configured by the air pump 30, the first passage 20, and the third passage 24, and the EGR passage is configured by the second passage 22 and the third passage 24. The configuration of a general engine control device provided with a supply system and an EGR device is used as it is, and the three-way valve 28 is provided to perform switching control.

Further, as described above, if the three-way valve 28 also has the function of an EGR control valve, the number of parts does not need to be increased at all, and the third passage 24 has a downstream portion of the secondary air supply passage and the EGR passage. Since they are shared, a torque shock and vibration prevention function can be newly obtained while promoting more compactness than the conventional system that performs secondary air supply and EGR.
Next, FIG. 3 shows a second embodiment of the engine control apparatus according to the present invention.

In the first embodiment, the EGR is performed by the differential pressure between the exhaust pressure and the intake pressure. However, there is a case where the air pump 30 is interposed in the middle of the EGR passage and becomes a resistance, and it is difficult to obtain a sufficient EGR amount. Then, it becomes difficult to secure a sufficient amount of EGR because the above-mentioned differential pressure becomes small in the middle and high load regions where the frequency of use is high.
Therefore, in the second embodiment, conversely, the air pump 30 is actively used to improve the EGR performance. For this reason, in this embodiment, the air pump 30 can be driven in a direction opposite to the suction direction in the intake passage before starting the engine 2 and the drive direction (forward rotation direction) at the time of supplying the secondary air as in the first embodiment. The configuration is such that during EGR, the amount of EGR can be increased by driving in the opposite direction.

The configuration in which the air pump 30 can be reversed does not require the air pump 30 itself to be changed, and a circuit for switching the energization direction may be provided inside the control unit 38.
FIG. 6A shows a case where the air pump 30 is driven in the forward rotation direction, as in the first embodiment, where arrow A indicates the suction in the intake passage before starting, and arrow B indicates the secondary air supply. Shows the state.
On the other hand, at the time of EGR, as shown in FIG. 5B, at least a predetermined condition, for example, a high load where the differential pressure between the exhaust pressure and the intake pressure is small, or a condition where an EGR amount greater than a predetermined value is required. For example, the air pump 30 is driven in the reverse direction. Thereby, a desired EGR amount can be satisfied even under these conditions, and the EGR control performance can be improved. In particular, it is possible to improve the fuel efficiency in the high-load driving range when the frequency of use is high in hybrid vehicles.

Note that, in a region where the differential pressure between the exhaust passage 14 and the intake passage 4 is large, such as a partial load operation region, EGR may be performed using this differential pressure as in the first embodiment. Only when the air pump 30 cannot be secured, the air pump 30 may be driven in reverse.
Next, FIG. 4 shows a third embodiment of the engine control apparatus according to the present invention.
In the present embodiment, one end (upstream end) of the first passage 20 is opened to the atmosphere without being connected to the intake passage 4, and the second air cleaner 50 is separated from the air cleaner 6 in the middle of the first passage 20. Although it differs from the said 1st, 2nd embodiment by the point which provided, The effect | action and effect similar to either of the said 1st, 2nd embodiment can be acquired.

Outline of First Embodiment of Engine Control Device according to the Present Invention Flowchart for control of the engine control apparatus according to FIG. Outline of Second Embodiment of Engine Control Device According to the Present Invention Outline of third embodiment of engine control apparatus according to present invention

Explanation of symbols

2 Engine 4 Intake passage 6 Air cleaner 8 Air flow meter 10 Throttle valve 14 Exhaust passage 18 Catalyst (Exhaust purification catalyst)
20 first passage 22 second passage 24 third passage 26 merging section 28 three-way valve (passage switching valve)
30 Air pump 50 Second air cleaner

Claims (5)

In an engine having a throttle valve in the intake passage and an exhaust purification catalyst in the exhaust passage,
A first passage with one end communicating with the atmosphere, a second passage with one end communicating with the intake passage downstream of the throttle valve, and an electric air pump with one end communicating with the exhaust passage upstream of the exhaust purification catalyst. And the third passage, the other ends of these passages are joined together, and a passage switching valve is provided at the joining portion, and the first passage and the second passage are selectively provided, While free to communicate with the third passage,
At the time of engine start request, before the cranking starts , the air in the intake passage downstream of the closed throttle valve is established by connecting the second passage and the third passage by the passage switching valve and driving the air pump. Is discharged to the exhaust passage through the second passage and the third passage, cranking is started in a state where the intake passage downstream of the throttle valve is set to a negative pressure, and the engine is started.
After the engine is started, when the secondary air supply for activation of the exhaust purification catalyst is requested, the first passage and the third passage are made to communicate with each other by the passage switching valve, and the air pump is driven so that the atmosphere is brought into the secondary air. To the exhaust passage through the first passage and the third passage,
When the exhaust gas recirculation request is made in the exhaust purification catalyst active state, the second passage and the third passage are communicated with each other by the passage switching valve, and a part of the exhaust gas is exhausted from the exhaust passage through the second passage and the third passage. Is controlled to recirculate to the intake passage.   2. The engine control device according to claim 1, wherein one end of the first passage communicates with an intake passage upstream of the throttle valve and an air flow meter.   The engine control device according to claim 2, wherein one end of the first passage communicates with the intake passage downstream of an air cleaner.   The engine according to any one of claims 1 to 3, wherein when the exhaust gas recirculation request is made, exhaust gas recirculation is performed by a differential pressure between an intake passage downstream of the throttle valve and the exhaust passage. Control device.   The air pump is configured to be driven in the opposite direction to the engine start request and the secondary air supply request, and when the exhaust gas recirculation request is made, the air pump is driven in the reverse direction so that a part of the exhaust gas is pumped and recirculated. The engine control device according to any one of claims 1 to 4, wherein

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