JP6866008B2 - Internal combustion engine control device - Google Patents

Description

The present invention relates to the control of an internal combustion engine accompanied by an exhaust gas recirculation device.

In the external EGR device, the exhaust passage and the intake passage of the internal combustion engine are connected by the EGR passage, and a part of the exhaust gas is returned to the intake passage via the EGR passage to be mixed with the intake air (for example, the following patent documents are referred to. reference). With EGR, it is possible to reduce the combustion temperature of the air-fuel mixture in the combustion chamber of the cylinder, _{suppress the amount of NO x} discharged, and reduce the pumping loss.

The exhaust contains water vapor or water derived from the fuel. In the process of mixing the EGR gas into the intake air, the water vapor or water contained in the EGR gas is condensed to generate condensed water. If this condensed water stays in a specific place and the sulfuric acid combined with the sulfur content in the fuel component dissolves in the condensed water, there is a concern that the members of the intake system, for example, the pipes and valves of the flow path, are corroded. In addition, a large amount of condensed water may flow into the combustion chamber of the cylinder at one time, causing a misfire.

Therefore, conventionally, the intake passage is designed to have a shape that prevents condensed water from accumulating in one place, and there is a high possibility that a large amount of condensed water will be generated in the intake passage, that is, the outside temperature or the intake temperature is low (for example, 5). When the temperature is (° C or lower), EGR is uniformly prohibited, that is, the EGR valve is fully closed to block the EGR passage. However, prohibiting EGR leads to abandoning the utility of EGR in reducing fuel injection amount and pumping loss.

Japanese Unexamined Patent Publication No. 2016-065510

An object of the present invention is to increase the chances of implementing EGR as much as possible even under the situation where EGR is conventionally prohibited, and to further improve the fuel efficiency of the internal combustion engine.

In order to solve the above-mentioned problems, in the present invention, the flow rate of the intake air flowing through the intake passage toward the cylinder, the ratio or amount of the EGR gas in the intake air filled in the cylinder, and the outside temperature, intake air temperature or cooling water temperature. Based on the above, the amount of condensed water remaining in the intake passage is estimated, and if the estimated amount of condensed water is equal to or greater than the judgment threshold, the implementation of EGR is prohibited. During the period until the predetermined time elapses, the amount of condensed water remaining in the intake passage is estimated according to the outside temperature at that time, and after the predetermined time elapses after the start of the internal combustion engine, the intake air is taken. The amount of condensed water remaining in the passage is estimated according to the latest calculated amount in the past, according to the flow rate of intake air at that time, the EGR rate of intake air or the EGR gas partial pressure suggesting the amount of EGR gas, and the outside temperature . It is calculated by adding the amount of change in condensed water per unit time, and the amount of change in condensed water per unit time becomes smaller as the flow rate of intake air flowing through the intake passage increases, and the EGR gas partial pressure of intake air becomes smaller. The lower the value, the smaller the value, and the higher the outside temperature, the smaller the value. Also, while EGR is prohibited, the EGR gas partial pressure of the intake air becomes 0 and the amount of change in condensed water per unit time takes a negative value. Yes, the estimated amount of condensed water gradually decreases, and the outside temperature is the outside temperature obtained by referring to the outside temperature signal, the intake temperature obtained by referring to the intake temperature signal, and the cooling water temperature. The control device of the internal combustion engine, which is the smallest value among the cooling water temperatures of the internal combustion engine known by referring to the signal, was constructed.

Specifically, the flow rate of the intake air, the ratio or amount of EGR gas in the intake air, the outside temperature, the intake air temperature or the cooling water temperature, and the value suggesting the amount of change in the condensed water accumulated in the intake passage per unit time. The map data that defines the relationship between the two is stored and stored, and for each unit time, the flow rate of the intake air at that time, the ratio or amount of EGR gas in the intake air, and the value corresponding to the outside temperature, intake air temperature, or cooling water temperature are stored. It is conceivable to read from the map data, integrate the read values, and compare the integrated value with the determination threshold to determine whether it is necessary to prohibit EGR.

According to the present invention, it is possible to increase the chances of implementing EGR even in a situation where EGR is conventionally prohibited, and it is possible to contribute to further improvement of the fuel efficiency performance of the internal combustion engine.

The figure which shows the schematic structure of the internal combustion engine for a vehicle and the control device in one Embodiment of this invention. The flow chart which shows the procedure example of the process which the control device of the same embodiment executes according to a program. The figure which illustrated the relationship between the flow rate of intake air, the partial pressure of EGR gas of intake air, and the outside air temperature, and the amount of change Δesegrwater of condensed water per unit time.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle according to the present embodiment. The internal combustion engine in the present embodiment is a spark-ignition type 4-stroke engine, and includes a plurality of cylinders 1 (one of which is illustrated in FIG. 1). An injector 11 for injecting fuel is provided in the vicinity of the intake port of each cylinder 1. Further, a spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives the application of the induced voltage generated by the ignition coil and induces a spark discharge between the center electrode and the ground electrode. The ignition coil is integrally built in the coil case together with the igniter which is a semiconductor switching element.

The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. An air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream on the intake passage 3.

The exhaust passage 4 for discharging the exhaust guides the exhaust generated by burning the fuel in the cylinder 1 to the outside from the exhaust port of each cylinder 1. An exhaust manifold 42 and a three-way catalyst 41 for purifying exhaust gas are arranged on the exhaust passage 4.

The external EGR device 2 realizes a so-called high-pressure loop EGR, and is an external EGR passage 21 that communicates with the upstream side of the catalyst 41 in the exhaust passage 4 and the downstream side of the throttle valve 32 in the intake passage 3, and the EGR passage 21. The EGR cooler 22 provided above and the EGR valve 23 that opens and closes the EGR passage 21 and controls the flow rate of the EGR gas flowing through the EGR passage 21 are elements. The inlet of the EGR passage 21 is connected to the exhaust manifold 42 in the exhaust passage 4 or a predetermined portion downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined portion downstream of the throttle valve 32 in the intake passage 3, particularly a surge tank 33.

The ECU (Electronic Control Unit) 0, which is a control device for an internal combustion engine of the present embodiment, is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

The input interface of ECU0 includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from an engine rotation sensor that detects the rotation angle of the crank shaft and the engine rotation speed, and an accelerator pedal. The accelerator opening signal c output from the sensor that detects the depression amount or the opening degree of the throttle valve 32 as the accelerator opening degree (so to speak, the engine load required for the internal combustion engine, the required output), and the temperature of the internal combustion engine are suggested. Cooling water temperature signal d output from the water temperature sensor that detects the cooling water temperature, intake air temperature / intake pressure signal output from the temperature / pressure sensor that detects the intake air temperature and intake pressure in the intake passage 3 (particularly, surge tank 33). e, outside temperature signal f output from the temperature sensor that detects the outside temperature (or new temperature), battery current / voltage signal g output from the sensor that detects the terminal current or terminal voltage of the vehicle-mounted battery, brake pedal The brake depression amount signal h or the like output from the sensor that detects the depression amount or the master cylinder pressure is input.

From the output interface of ECU 0, an ignition signal i is sent to the igniter, a fuel injection signal j is sent to the injector 11, an opening operation signal k is sent to the throttle valve 32, an opening operation signal l is sent to the EGR valve 23, and the like. Output.

The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates an operation parameter, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, h necessary for the operation control of the internal combustion engine via the input interface, obtains the engine speed, and fills the cylinder 1. Estimate the amount of intake air. Then, based on the engine speed, intake amount, etc., the required fuel injection amount, fuel injection timing (including the number of fuel injections per combustion), fuel injection pressure, ignition timing, required EGR rate (or EGR). Various operating parameters such as gas amount) and opening / closing timing of the intake valve are determined. The ECU 0 applies various control signals i, j, k, l corresponding to the operation parameters via the output interface.

Further, the ECU 0 controls to operate the electric motor (starter motor or ISG (Integrated Starter Generator)) when the internal combustion engine is started (it may be a cold start or a return from the idling stop). The signal o is input to the electric motor, and the electric motor performs cranking to rotate the crankshaft. Cranking is performed when the internal combustion engine goes from the initial explosion to the continuous explosion and the engine speed, that is, the rotation speed of the crankshaft, exceeds the judgment value determined according to the cooling water temperature of the internal combustion engine (considered to be completely detonated). ) Finish.

The ECU 0 executes an idle stop system for stopping the idle rotation of the internal combustion engine when a predetermined idle stop condition is satisfied. First, after the cold start of the internal combustion engine, the ECU 0 executes idle stop on the condition that the cooling water temperature rises above a predetermined value and the charge amount or terminal voltage of the vehicle-mounted battery is above a predetermined value. Allow (until then, do not allow the execution of idle stop). On top of that, the amount of depression of the brake pedal or the pressure of the master cylinder is above the threshold (the brake pedal is depressed), the compressor for refrigerant compression of the air conditioner for vehicle interior air conditioning is not operating, and the shift position is set. It is a driving range, has a history of accelerating to a certain vehicle speed or more from the end of the previous idle stop, and the current vehicle speed is below a certain vehicle speed (for example, the vehicle speed has decreased from 13.5 km / h or more to 13 km / h). Or, when all the conditions such as (decreased from 9.5 km / h or more to 7 km / h) are satisfied, the idle stop is executed.

After the idle stop condition is satisfied, the internal combustion engine is restarted when the predetermined idle stop end condition is satisfied. In ECU0, the depression amount of the brake pedal or the master cylinder pressure became 0 or less than the threshold value close to 0 (the brake pedal was not depressed), and conversely, the depression amount of the brake pedal or the master cylinder pressure further increased (brake). When any of the following is true: the pedal is depressed more strongly), the accelerator opening is increased (the accelerator pedal is depressed), the predetermined time (3 minutes) has passed in the idle stop state, and so on. Finish the idle stop and restart the internal combustion engine.

The EGR ratio, which is the ratio of the EGR gas to the intake air charged in the cylinder 1, is determined according to the load required for the internal combustion engine at that time. The required EGR rate is highest in the medium load operating region, and decreases as the engine load increases, and decreases as the engine load decreases. In a high load operating region near full load or near full load, or in a low load operating region close to idle operation or idle operation, the required EGR rate becomes 0, and the EGR valve 23 is fully closed to shut off the EGR passage 21. It becomes.

The required EGR rate is affected by the temperature of the internal combustion engine at that time. Generally, the lower the temperature of the internal combustion engine, the more unstable the combustion of the air-fuel mixture in the combustion chamber of the cylinder 1. Therefore, when the cooling water temperature of the internal combustion engine is low, the required EGR rate is lowered as compared with the case where the cooling water temperature is high.

The EGR gas that returns from the exhaust passage 4 to the intake passage 3 contains water vapor or water derived from the fuel. Then, in the process of the EGR gas flowing through the intake passage 3, the water vapor or the water contained in the EGR gas is condensed. If the condensed water stays in a specific place and the sulfuric acid combined with the sulfur content in the fuel component dissolves in it, the piping of the intake passage 3, the surge tank 33, the intake manifold 34, the throttle valve 32, etc. may be corroded. There is. Not only that, a large amount of condensed water may flow into the combustion chamber of the cylinder 1 at one time, which may cause a misfire.

Therefore, the ECU 0 of the present embodiment includes the flow rate of the intake air flowing through the intake passage 3 toward the cylinder 1, the EGR ratio (or the amount of EGR gas) of the intake air filled in the cylinder 1, and the outside temperature, the intake air temperature, or the internal combustion engine. Based on the cooling water temperature of the engine, the amount of condensed water remaining in the intake passage 3 is estimated, and it is determined whether or not it is necessary to prohibit EGR according to the amount of the condensed water.

FIG. 2 shows an example of a procedure for processing executed by ECU 0 of the present embodiment. First, the ECU 0 sets the estimated amount of condensed water ecgrwater remaining in the intake passage 3 during the period from the start of the stopped internal combustion engine to the elapse of a predetermined time (step S1). The initial value is set according to the outside air temperature of (step S2). In the memory of the ECU 0, map data that defines the relationship between the outside air temperature and the initial value of the estimated amount of condensed water ecgrwater is stored in advance. The ECU 0 searches the map data using the outside air temperature at the time of cold start of the internal combustion engine or the time immediately after the start as a key, and obtains the initial value of the estimated amount of condensed water ecgrwater. In general, the initial value of the estimated amount of condensed water ecgrwater becomes larger as the outside air temperature is lower.

On the other hand, in the period after a predetermined time has already passed since the start of the internal combustion engine, the estimated amount ecgrwater of the condensed water currently remaining in the intake passage 3 is converted to the estimated amount ecgrwater'calculated in the latest past. It is obtained by adding the amount of change Δecgrwater of condensed water per unit time (step S3). The amount of change Δacegrwater is a value according to the flow rate of the intake air at that time, the EGR rate of the intake air, the partial pressure of the EGR gas suggesting the amount of EGR gas, and the outside temperature. The amount of change Δacegrwater may be a positive value, that is, an increase amount, or a negative value, that is, a decrease amount. In the memory of the ECU 0, map data that defines the relationship between the intake flow rate, the EGR gas partial pressure, and the outside air temperature and the change amount Δescagrwater is stored in advance. The ECU 0 searches the map data using the current intake flow rate, EGR gas partial pressure, and outside air temperature as keys, and obtains the amount of change Δecgrwater.

FIG. 3 illustrates the relationship between the flow rate of intake air, the partial pressure of EGR gas of intake air, and the outside air temperature, and the amount of change in condensed water per unit time Δacegrwater. The amount of change Δecgrwater becomes a smaller value as the flow rate of the intake air flowing through the intake passage 3 increases, and becomes a negative value in some cases. This is because the larger the intake flow rate, the more difficult it is for condensed water to collect in the intake passage 3. The intake flow rate can be estimated from the engine speed and the intake pressure in the surge tank 33. Map data that defines the relationship between the engine speed, the intake pressure in the surge tank 33, and the intake flow rate is stored in the memory of the ECU 0 in advance. The ECU 0 searches the map data using the current engine speed and the intake pressure in the surge tank 33 as keys, and obtains an estimated value of the current intake flow rate. However, when an air flow meter is installed in the intake passage 3, it is possible to directly measure the flow rate of the intake air through the air flow meter.

Further, the change amount Δacegrwater becomes a smaller value as the partial pressure of the EGR gas in the intake air is lower, that is, as the amount of EGR gas contained in the intake air is smaller, and in some cases, it becomes a negative value. This is because the lower the EGR rate, the less water vapor or water is mixed in the intake air, and the less condensed water is generated in the intake passage 3. The partial pressure of the EGR gas in the intake air can be estimated from the engine speed and the opening degree of the EGR valve 23. Map data that defines the relationship between the engine speed, the opening degree of the EGR valve 23, and the EGR gas partial pressure is stored in the memory of the ECU 0 in advance. The ECU 0 searches the map data using the current engine speed and the EGR valve 23 opening as keys, and obtains an estimated value of the EGR gas partial pressure of the current intake air.

In addition, the amount of change Δecgrwater becomes a small value as the outside air temperature rises, and becomes a negative value in some cases. This is because the higher the outside air temperature, the higher the temperature of the pipe wall of the intake passage 3 and the less likely it is to generate condensed water. Conversely, the lower the outside air temperature, the lower the temperature of the pipe wall of the intake passage 3 and the more condensed water is generated. By making it easier to do. In steps S2 and S3, the outside air temperature obtained by referring to the outside air temperature signal f, the intake air temperature obtained by referring to the intake air temperature / intake pressure signal e, and the cooling water temperature signal d are referred to. The smallest value of the cooling water temperature that can be known is regarded as the outside air temperature. As a result, the accuracy of detecting the outside air temperature via the sensor can be improved, and the calculation accuracy of the estimated amount of condensed water ecgrwater can be improved.

Then, the ECU 0 compares the estimated amount ecgrwater of the condensed water remaining in the intake passage 3 calculated through steps S2 or S3 with the determination threshold value. Then, if the estimated amount of condensed water ecgrwater is smaller than the determination threshold value, the execution of EGR is permitted (step S4).

On the other hand, if the estimated amount of condensed water ecgrwater is equal to or greater than the determination threshold value, the implementation of EGR is prohibited (step S5). When EGR is prohibited, the required EGR rate is regarded as 0 regardless of the current engine load, and the EGR valve 23 is fully closed to shut off the EGR passage 21. If EGR is prohibited and the inflow of EGR gas into the intake passage 3 is stopped, the amount of condensed water staying in the intake passage 3 can be reduced. This contributes to suppressing corrosion of the components of the intake passage 3 and the valves on the intake passage 3 and preventing the occurrence of misfire due to a large amount of condensed water flowing into the combustion chamber of the cylinder 1.

The ECU 0 repeatedly executes the processes of steps S1 to S5 described above every unit time. While the implementation of EGR is prohibited, only the intake air containing no EGR gas, that is, fresh air flows through the intake passage 3, and the condensed water accumulated in the intake passage 3 is purged. The condensed water is discharged to the outside through the combustion chamber of the cylinder 1 and the exhaust passage 4. At the same time, the partial pressure of the EGR gas in the intake air becomes 0, the amount of change in the estimated amount of condensed water per unit time Δescagrwater becomes 0 or a negative value, and the estimated amount of condensed water calculated repeatedly by ECU 0. The estimator gradually decreases. When the estimated amount of condensed water ecgrwater falls below the determination threshold, EGR will be restarted.

In the present embodiment, based on the flow rate of the intake air flowing through the intake passage 3 toward the cylinder 1, the ratio or amount of the EGR gas in the intake air filled in the cylinder 1, and the outside temperature, the intake air temperature, or the cooling water temperature. The control device 0 of the internal combustion engine for determining whether or not the EGR needs to be prohibited is configured. More specifically, the control device 0 determines the flow rate of the intake air, the ratio or amount of the EGR gas in the intake air, the outside temperature, the intake air temperature or the cooling water temperature, and the condensed water accumulated in the intake air passage 3 per unit time. It stores and holds map data that defines the relationship with the value Δesegrwater that suggests the amount of change, and for each unit time, the flow rate of the intake air at that time, the ratio or amount of EGR gas in the intake air, and the outside temperature, By reading the value Δecegrwater corresponding to the intake air temperature or the cooling water temperature from the map data, integrating (or time-integrating) the read value Δesgrwater to obtain the integrated value eseggrwater, and comparing the integrated value eseggrwater with the judgment threshold value. Determine if EGR needs to be banned.

According to the present embodiment, even in a situation where EGR is conventionally prohibited, for example, a situation where the outside air temperature or the intake air temperature is low, the amount of condensed water remaining in the intake passage 3 ecgrwater determines the determination threshold value. As long as it is below, EGR can be performed. That is, the opportunity of EGR is increased, and the utility of EGR such as reduction of fuel injection amount and reduction of pumping loss can be fully enjoyed, and the fuel efficiency performance of the internal combustion engine can be further improved.

The present invention is not limited to the embodiments described in detail above.

In the above embodiment, the estimated amount of condensed water remaining in the intake passage 3 eseggrwater is set to an initial value according to the outside air temperature during the period from the start of the internal combustion engine until a predetermined time elapses. Was there. On the other hand, it is also conceivable to determine the estimated amount of condensed water ecgrwater during the period according to the length of the stop time before the start of the internal combustion engine. For example, when the internal combustion engine has been stopped for a significantly long time such as during a cold start, the estimated amount of condensed water during the period, ecgrwater, is initially set according to the outside air temperature, as in the above embodiment. Set to a value. On the other hand, if the internal combustion engine is stopped for a short time, such as when restarting after an idle stop, the internal combustion engine is restarted by taking over the estimated amount of condensed water ecegrwater at the time of the latest stop of the internal combustion engine. It is the estimated amount of condensed water after starting. The length of the stop time of the internal combustion engine can be determined by referring to the difference between the cooling water temperature stored at the time of the latest stop of the internal combustion engine and the cooling water temperature immediately after the start of the internal combustion engine. That is, if the absolute value of the difference between the former and the latter is larger than the predetermined value, it is determined that the stop time of the internal combustion engine is long, and if the absolute value of the difference is less than or equal to the predetermined value, the stop time of the internal combustion engine is short. Judge.

In addition, the specific configuration of each part, the content of processing, and the like can be variously modified without departing from the spirit of the present invention.

The present invention can be used for controlling an internal combustion engine mounted on a vehicle or the like.

0 ... Control device (ECU)
1 ... Cylinder 2 ... Exhaust gas recirculation (EGR) device 21 ... EGR passage 23 ... EGR valve 3 ... Intake passage 4 ... Exhaust passage

Claims (2)

Condensed water remaining in the intake passage based on the flow rate of the intake air flowing through the intake passage toward the cylinder, the ratio or amount of EGR gas in the intake air filled in the cylinder, and the outside temperature, intake air temperature, or cooling water temperature. If the estimated amount of condensed water is equal to or greater than the judgment threshold, the implementation of EGR is prohibited.
During the period from the start of the internal combustion engine to the elapse of a predetermined time, the amount of condensed water remaining in the intake passage is estimated according to the outside air temperature at that time.
After the start of the internal combustion engine, after a lapse of a predetermined time, the amount of condensed water that SonTome into the intake manifold, the estimated amount calculated to the nearest past, the flow rate of the intake air at the time, EGR rate or EGR intake It is determined by adding the EGR gas partial pressure that suggests the amount of gas and the amount of change in condensed water per unit time according to the outside temperature.
The amount of change in condensed water per unit time becomes smaller as the flow rate of intake air flowing through the intake passage increases, becomes smaller as the partial pressure of EGR gas in the intake air decreases, and decreases as the outside temperature rises.
In addition, while EGR is prohibited, the partial pressure of EGR gas in the intake air may become 0 and the amount of change in condensed water per unit time may take a negative value, and the estimated amount of condensed water gradually decreases.
The outside air temperature is an internal combustion engine known by referring to an outside air temperature obtained by referring to an outside air temperature signal, an intake air temperature obtained by referring to an intake air temperature signal, and a cooling water temperature signal. A control device for an internal combustion engine, which is the smallest value of the cooling water temperature. The relationship between the flow rate of the intake air, the ratio or amount of EGR gas in the intake air, and the relationship between the outside air temperature, the intake air temperature or the cooling water temperature, and the value suggesting the amount of change in the condensed water accumulated in the intake air passage per unit time is specified. It stores and retains map data.
For each unit time, the flow rate of the intake air at that time, the ratio or amount of the EGR gas in the intake air, and the values corresponding to the outside temperature, the intake air temperature, or the cooling water temperature are read from the map data, and the read values are integrated. The control device for an internal combustion engine according to claim 1, wherein it is determined whether or not it is necessary to prohibit EGR by comparing the integrated value with the determination threshold value.

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