JP7375625B2 - engine system - Google Patents

Description

The present invention relates to an engine system.

A technique related to determining whether a foreign object is caught in an EGR valve is known (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 2019-157771

For example, the above determination can be made based on the difference between the measured value and the estimated value of the intake pressure. In other words, if the above difference is relatively large, it is determined that EGR valve clogging has occurred, and if this difference is small and the actual measured value and estimated value can be considered to be approximately the same, clogging has not occurred. It can be determined that there is no However, even under normal conditions when no foreign matter is caught, there is a discrepancy between the actual measured value and the estimated value. This deviation value is not a constant value but varies. For this reason, if the above-mentioned judgment is made without considering such a dispersion value, there is a possibility that the above-mentioned judgment cannot be made with high accuracy.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an engine system that can accurately learn the deviation between an actual measured value and an estimated value of intake pressure.

The above object includes an engine, a throttle valve and an intake pressure sensor provided in an intake passage connected to the engine, a crank angle sensor that detects the rotational speed of the engine, and a temperature of cooling water flowing through the throttle valve. a temperature sensor for detecting a temperature sensor; an evaporative fuel processing device for introducing purge gas containing evaporated fuel from a canister into the intake passage through a purge passage; an estimator for estimating an intake pressure; and the rate of change in the engine speed is below a predetermined value, the rate of change in the flow rate of the purge gas is below a predetermined value, and the rate of change in the temperature of the cooling water is below a predetermined value, the intake pressure This can be achieved by an engine system equipped with a learning section that learns the discrepancy between the actual measured value of the sensor and the estimated value of the intake pressure.

According to the present invention, it is possible to provide an engine system that can accurately learn the deviation between the measured value and the estimated value of the intake pressure.

FIG. 1 is a schematic diagram of the engine system of this embodiment. FIG. 2A is an explanatory diagram when no foreign object is caught, and FIG. 2B is an explanatory diagram when foreign object is caught. FIG. 3 is a flowchart showing an example of control executed by the ECU. FIG. 4 is a graph showing variations in the deviation value obtained by subtracting the estimated value from the measured value of the intake pressure.

FIG. 1 is a schematic diagram of the engine system of this embodiment. The engine 20 combusts an air-fuel mixture in a combustion chamber 23 in a cylinder head 22 installed on a cylinder block 21 in which a piston 24 is housed, and causes the piston 24 to reciprocate. The reciprocating motion of the piston 24 is converted into rotational motion of the crankshaft 26. An oil pan 21a that stores lubricating oil is provided at the bottom of the cylinder block 21. Although not shown, the engine 20 is an in-line four-cylinder engine having four cylinders, but is not limited thereto.

The cylinder head 22 of the engine 20 is provided with an intake valve 42 for opening and closing the intake port 10i and an exhaust valve 44 for opening and closing the exhaust port 30e for each cylinder. Furthermore, a spark plug 27 for igniting the air-fuel mixture in the combustion chamber 23 is attached to the top of the cylinder head 22 for each cylinder. Further, the cylinder head 22 is provided with an in-cylinder injection valve 12 that injects fuel into the combustion chamber 23 . The intake air taken into the combustion chamber 23 when the intake valve 42 is opened and the fuel injected from the in-cylinder injection valve 12 are mixed to form an air-fuel mixture, which is compressed by the piston 24, and the spark plug It is ignited and burned at 27.

The intake port 10i of each cylinder is connected to the surge tank 18 via a branch pipe for each cylinder. An intake pipe 10 is connected to the upstream side of the surge tank 18, and an air cleaner 19 is provided at the upstream end of the intake pipe 10. The intake pipe 10 is provided with, in order from the upstream side, an air flow meter 15a for detecting the amount of intake air, an intake air temperature sensor 15b for detecting the temperature of the intake air, and an electronically controlled throttle valve 13. Further, the surge tank 18 is provided with an intake pressure sensor 17 that detects intake pressure.

The exhaust port 30e of each cylinder is connected to the exhaust pipe 30 via a branch pipe for each cylinder. A three-way catalyst 31 is provided in the exhaust pipe 30. An air-fuel ratio sensor 33 is installed upstream of the three-way catalyst 31 to detect the air-fuel ratio of exhaust gas.

An EGR pipe 50 is provided that communicates the exhaust pipe 30 and the intake pipe 10. The EGR pipe 50 is provided with an EGR valve 52 whose opening degree can be adjusted. The EGR pipe 50 and the EGR valve 52 correspond to an EGR device. When the EGR valve 52 opens, a part of the exhaust gas is returned to the intake pipe 10, and by adjusting the opening degree of the EGR valve 52, the amount of EGR gas relative to the total amount of intake gas taken into the combustion chamber 23 can be adjusted. The EGR rate, which is a ratio, can be adjusted. Note that the EGR rate here is an external EGR rate. The EGR pipe 50 may be equipped with an EGR cooler.

The engine 20 also includes variable valve mechanisms (hereinafter referred to as VVT) 43 and 45 that change the valve operating characteristics of the intake valve 42 and the exhaust valve 44, respectively. In the VVT 45, for example, a drive cam is provided on the exhaust side camshaft corresponding to one exhaust valve 44, and the exhaust valve 44 is opened and closed by the drive cam. The drive cam is connected to the exhaust side camshaft so that its phase can be changed. Thereby, the opening timing and closing timing of the exhaust valve 44 can be changed to the advanced or retarded side. The same applies to VVT43. Note that the phase of the drive cam with respect to the camshaft is switched according to the oil pressure adjusted by the oil control valve. Note that an electric valve mechanism may be used instead of the hydraulic VVT 45.

The evaporative fuel processing device 60 includes a canister 61 , a vapor passage 62 , a blocking valve 63 , an outside air introduction passage 64 , an outside air introduction valve 65 , a purge passage 66 , and a purge valve 67 . The canister 61 is configured to be able to adsorb evaporated fuel. The vapor passage 62 guides the vaporized fuel in the fuel tank 28 to the canister 61. The blocking valve 63 is provided in the vapor passage 62. When the blockage valve 63 is closed, vaporized fuel does not flow from the fuel tank 28 to the canister 61 via the vapor passage 62. When the blockage valve 63 is open, vaporized fuel is allowed to flow from the inside of the fuel tank 28 to the canister 61 via the vapor passage 62.

The outside air introduction passage 64 is connected to the canister 61 and introduces outside air into the canister 61. The outside air introduction valve 65 is provided in the outside air introduction passage 64. When the outside air introduction valve 65 is open, outside air is allowed to be introduced into the canister 61 via the outside air introduction passage 64. When the outside air introduction valve 65 is closed, the introduction of outside air into the canister 61 via the outside air introduction passage 64 is stopped.

Purge passage 66 connects canister 61 and surge tank 18 . The purge passage 66 is connected to a portion of the intake pipe 10 downstream of the throttle valve 13. A purge valve 67 is provided in the purge passage 66.

The evaporated fuel processing device 60 opens both the blockade valve 63 and the purge valve 67 when negative pressure is generated in the downstream side of the throttle valve 13 in the intake pipe 10, thereby reducing the internal pressure in the fuel tank 28. The vaporized fuel is purged into the intake pipe 10 through the vapor passage 62, the canister 61, and the purge passage 66.

The ECU (Electronic Control Unit) 60 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory). ECU 100 controls engine 20 by executing programs stored in RAM or ROM. ECU 100 is a control device for engine 20. Further, the CPU, RAM, and ROM of the ECU 100 functionally implement an estimation section and a learning section, which will be described later.

The above-described spark plug 27, throttle valve 13, direct injection valve 12, and EGR valve 52 are electrically connected to the ECU 100. The ECU 100 also includes an accelerator opening sensor 11 that detects the accelerator opening, a throttle opening sensor 14 that detects the throttle opening of the throttle valve 13, an air flow meter 15a, an intake temperature sensor 15b, an intake pressure sensor 17, and a crankshaft 26. A crank angle sensor 25 that detects the crank angle of the engine 20, a water temperature sensor 29a that detects the temperature of the cooling water of the engine 20, an atmospheric pressure sensor 29b, an air-fuel ratio sensor 33, and other various sensors are electrically connected. The ECU 100 controls the spark plug 27, the throttle valve 13, the in-cylinder injection valve 12, the EGR valve 52, the blockade valve 63, the outside air introduction valve 65, and the like to obtain the desired output based on the detected values of various sensors. It controls the purge valve 67, etc., and controls the ignition timing, fuel injection amount, fuel injection timing, throttle opening, EGR rate, flow rate of purge gas, etc.

Next, a description will be given of foreign matter getting caught in the EGR valve 52. FIG. 2A is an explanatory diagram when no foreign matter is caught. The EGR valve 52 includes a valve body 54 that is stroked by an actuator (not shown), and a valve seat 56 on which the valve body 54 is seated when the valve is closed. As shown in FIG. 2A, the EGR pipe 50 is closed by the valve body 54 being seated on the valve seat 56. Here, when the valve body 54 moves from the open state where the valve body 54 is separated from the valve seat 56 to the closed state where the valve body 54 is seated on the valve seat 56, a foreign object F is generated between the valve body 54 and the valve seat 56. There is a possibility of being bitten. FIG. 2B is an explanatory diagram when a foreign object is caught. As shown in FIG. 2B, when a foreign object F gets caught between the valve body 54 and the valve seat 56, a gap is created between the valve body 54 and the valve seat 56, and the flow rate of EGR gas should become zero. However, EGR gas may be returned to the intake pipe 10 through this gap. This foreign material may be caused, for example, by spatter generated during the welding process during the manufacture of the engine 20 and peeled off due to engine vibration or the like.

Such foreign matter may cause, for example, deterioration of the combustion state and engine stall, excessive temperature rise of the three-way catalyst 31, increase in the vibration frequency of the engine 20 during idling operation, or the engine stall. This may affect the startup of the 20. Therefore, it is desirable to accurately determine whether such foreign matter is caught.

Here, if there is no foreign matter trapped, the actual measurement value of the intake pressure sensor 17 will be a negative pressure depending on the opening degree of the throttle valve 13, but if there is foreign matter trapped, the EGR gas will be absorbed into the intake air. By being refluxed into the pipe 10, the pressure becomes higher than that in the case where no foreign matter is trapped, that is, it approaches positive pressure (atmospheric pressure). Here, the intake pressure is estimated based on the operating state of the engine 20, detected values of other sensors, etc., and based on the difference between the actual measurement value and the estimated value of the intake pressure sensor 17, it is determined whether or not a foreign object is caught. It is possible that The estimated value corresponds to the intake pressure when no foreign object is trapped, and if no foreign object is trapped, the above difference will be a relatively small value, and if no foreign object is trapped, the above difference will be a relatively small value. This is because the above difference should be a relatively large value if the

However, as will be described in detail later, there is a discrepancy between the actual measured value and the estimated value even under normal conditions when no foreign matter is caught, and this discrepancy value is not constant but varies. Variations in this deviation value are caused by variations in the detection accuracy of the intake pressure sensor 17 itself, variations in the operating state of the engine 20, variations in the detection accuracy of the sensor itself used to calculate the estimated value, and variations due to other environmental changes. . Therefore, in this embodiment, the deviation value is learned when a certain condition is satisfied that the variation in the deviation value becomes small, and the foreign object bite determination is performed in consideration of the learned deviation value.

For example, the determination of whether a foreign object is caught can be performed as follows. The determination is made based on the actual measurement value of the intake pressure sensor 17, the estimated value of the intake pressure, a deviation value learned in advance, and the rotation speed of the engine 20. Specifically, a measured value and an estimated value are obtained when a predetermined judgment condition is met, a difference value is obtained by subtracting this estimated value from the measured value, and a deviation value is subtracted from this difference value. If the calculated value is less than or equal to a predetermined value, it is determined that no jamming has occurred, and if the calculated value exceeds the predetermined value, it is determined that jamming has occurred. Here, the predetermined value is set to a smaller value, for example, as the rotation speed of the engine 20 increases.

Next, the control executed by ECU 100 will be explained. FIG. 3 is a flowchart showing an example of control executed by the ECU 100. This control is executed repeatedly. The ECU 100 determines whether a foreign object jamming determination condition is satisfied (step S1). The foreign object jamming determination condition is that the engine 20 is in an idling operating state, a fuel cut is not being performed, and the EGR valve 52 is transitioning from an open state to a closed state. Note that these determination conditions are satisfied in the process of decelerating and stopping the vehicle while the engine 20 is in an idling state. Therefore, the condition for determining whether a foreign object is caught is satisfied every time from the time the vehicle decelerates until the vehicle stops.

FIG. 4 is a graph showing the variation in the deviation value [kPa] obtained by subtracting the estimated value [kPa] from the measured value [kPa] of the intake pressure under normal conditions when no foreign matter is caught. A curve D1 shows variations in deviation values when the EGR valve 52 is transitioning from open to closed. Curve D2 shows variations in deviation values when the EGR valve 52 is in a state of transition from open to closed and the engine 20 is in an idling operating state. Curve D3 shows variations in deviation values when the EGR valve 52 is transitioning from open to closed, the engine 20 is in idle operation, and no fuel cut is performed. . As shown in FIG. 3, among the curves D1 to D3, the curve D3 has the smallest variation.

Here, the deviation value is the difference between the actual measured value and the estimated value of the intake pressure under normal conditions, as described above, so when the variation in the deviation value is small, the following foreign object detection processing is performed. By executing this, the accuracy of determining whether a foreign object is caught will improve.

If No in step S1, this control ends. If Yes in step S1, a foreign object jamming determination process is executed (step S2). In the foreign object jamming determination, as described above, the actual measured value of the intake pressure sensor 17 is acquired, and the estimated value of the intake pressure is calculated, and this actual measured value and estimated value are combined with the learned value stored in advance in the RAM of the ECU 100. The determination is made based on the deviation value. Here, the estimated value of the intake pressure is calculated by an air model from the actual measurement value of the atmospheric pressure sensor 29b, the actual measurement value of the air flow meter 15a, the actual measurement value of the intake temperature sensor 15b, etc. The process in step S2 is an example of a process executed by the estimator that estimates the intake pressure. Note that the estimated value of the intake pressure may be calculated using other known methods.

Next, the ECU 100 determines whether or not a foreign object is caught, based on the result of the determination process described above. (Step S3). If Yes in step S3, ECU 100 executes engine stall prevention processing (step S4). As the engine stall prevention process, for example, an idle up process and an intake air amount increase process are executed. The idle up process is a process that sets the target idle speed to a value obtained by adding the idle up speed to the reference idle speed. The intake air amount increasing process is a process that can increase the reserve torque by increasing the opening degree of the throttle valve to increase the intake air amount while retarding the ignition timing. This makes it possible to prevent the engine from stalling due to foreign objects being caught in the engine. Note that the process to be performed when it is determined that a foreign object is caught is not limited to the above, but for example, when a predetermined operating condition is satisfied, a process for opening the EGR valve 52 and removing the foreign object is executed. It's okay.

If No in step S3, the ECU 100 determines whether a condition for learning the deviation value is satisfied (step S5). Specifically, in addition to the foreign object jamming determination conditions, there is no foreign object trapped, the rate of change in the rotational speed of the engine 20 is below a predetermined value, the rate of change in the flow rate of purge gas is below a predetermined value, and cooling If the rate of change in water temperature is less than or equal to a predetermined value, it is determined that the learning condition is satisfied. The rotation speed of the engine 20 can be acquired by the crank angle sensor 25. The rate of change in the flow rate of the purge gas can be estimated based on the rate of change in the air-fuel ratio detected by the air-fuel ratio sensor 33 when the purge valve 67 is opened from closed. The rate of change in the temperature of the cooling water can be obtained by the water temperature sensor 29a. Note that the methods for obtaining, calculating, and estimating these rates of change are not limited to the above.

The fact that the rate of change in the rotational speed of the engine 20 is less than or equal to a predetermined value, the rate of change in the flow rate of purge gas is less than or equal to a predetermined value, and the rate of change in temperature of cooling water is less than or equal to a predetermined value means that the change in intake pressure is This means that the rate is low. This is because if the rate of change in the rotational speed of the engine 20 is large, the intake pressure will also vary greatly, and if the rate of change in the flow rate of the purge gas is large, the intake pressure will also vary greatly. The reason why the above learning conditions include the case where the rate of change in the temperature of the cooling water is small is as follows. This cooling water flows not only in the cylinder block 21 and cylinder head 22 of the engine 20 but also in the throttle valve 13. Therefore, for example, until the engine 20 is started and warmed up, the rate of increase in the temperature of the cooling water is large, and accordingly the temperature of the throttle valve 13 changes greatly, which causes the intake air temperature to change greatly as well.

If No in step S5, this control ends. If Yes in step S5, ECU 100 executes a learning process (step S6). In the learning process, the deviation value between the obtained measured value of the intake pressure and the calculated estimated value is learned. A curve D4 in FIG. 4 shows the variation in the difference when the above-mentioned foreign object jamming determination condition and learning condition are satisfied. In this case, since the deviation value has the least variation, the deviation value can be learned with high accuracy by learning when the above conditions are met. In addition, in such a learning process, a deviation value obtained by performing smoothing processing based on the deviation value learned last time and the deviation value learned this time may be learned as a new deviation value. The processing in steps S5 and S6 is an example of processing executed by the learning section.

As described above, when the foreign object jamming determination condition is satisfied, it is determined that there is no foreign object trapped, and the learning condition is satisfied, the learning process is executed. Therefore, the learning conditions are essentially that the EGR valve 52 is normal and its opening degree is zero, the engine 20 is in an idling operating state, no fuel cut is being performed, and the engine 20 is rotating. The rate of change in the flow rate of the purge gas is less than or equal to a predetermined value, and the rate of change in the temperature of the cooling water is less than or equal to a predetermined value. However, in the above-mentioned foreign object jamming determination conditions or learning conditions, the fact that fuel cut is not performed may be excluded.

In the above embodiment, the learned difference between the actual measured value and the estimated value of the intake pressure is used to determine if a foreign object is caught in the EGR valve, but the difference is not limited to this, and may be used for other determinations, processing, control, etc. Good too.

In the above embodiment, the deviation value is learned when the foreign object jamming determination process is executed, but the present invention is not limited to this. For example, even in an engine system in which the EGR pipe 50 and the EGR valve 52 are not provided, when the engine 20 is in an idling state and the rate of change in the rotational speed of the engine 20 is below a predetermined value, the flow rate of the purge gas changes. The deviation value may be learned when the rate is below a predetermined value and the rate of change in the temperature of the cooling water is below a predetermined value.

The engine system of this embodiment may be a system employing a gasoline engine or a diesel engine, or may be an engine system mounted on a hybrid vehicle.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and variations can be made within the scope of the gist of the present invention as described in the claims. Changes are possible.

13 Throttle valve 17 Intake pressure sensor 20 Engine 25 Crank angle sensor 60 Evaporated fuel processing device 100 ECU (estimation section, learning section)

Claims (1)

engine and
a throttle valve and an intake pressure sensor provided in an intake passage connected to the engine;
a crank angle sensor that detects the rotation speed of the engine;
a temperature sensor that detects the temperature of cooling water flowing through the throttle valve;
an evaporated fuel processing device that introduces purge gas containing evaporated fuel from a canister to the intake passage through a purge passage;
an estimation unit that estimates intake pressure;
The operating state of the engine is an idle operating state, the rate of change in the rotational speed of the engine is below a predetermined value, the rate of change in the flow rate of the purge gas is below a predetermined value, and the rate of change in the temperature of the cooling water is below a predetermined value. An engine system comprising: a learning unit that learns a deviation between an actual value measured by the intake pressure sensor and an estimated value of the intake pressure when the intake pressure is equal to or less than a predetermined value.

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