JP2006029193A - Idling speed control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an idling speed control device for an internal combustion engine capable of performing stable idling speed control. <P>SOLUTION: ECU 40 calculates feed back control quantity based on deviation of engine speed from idling target speed and retains the feed back control quantity in back up RAM 44 as a learning value at a predetermined learning timing, and performs feed back control of intake air quantity adjustment by opening and closing a throttle valve in a throttle body based on the feed back control quantity and learning value. The ECU 40 detects temperature of the throttle body based on engine room inside temperature (intake air temperature) and engine cooling water temperature, calculates learning value obtained by excluding temperature change component based on the temperature from the feed back control quantity and retains the learning value in the back up RAM 44. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an idling engine speed control device for an internal combustion engine that is suitable for stabilizing the engine speed during idling with a small intake air amount (throttle passage air amount).

  In the throttle control device that adjusts the amount of intake air to the engine, the temperature of the throttle body rises as the temperature in the engine room rises due to warming up of the engine or the like. Then, the throttle body is thermally expanded, and the throttle valve disposed therein is also thermally expanded. Since the throttle body is generally made of aluminum die cast and the throttle valve is made of brass, the throttle body has a larger coefficient of thermal expansion than the throttle valve, and even if the throttle opening is the same, the throttle valve is lower than at low temperatures. The amount of air passing through increases. The influence of the change in the air amount due to the thermal expansion of the throttle body appears remarkably during idling when the amount of air passing through the throttle is small.

  Therefore, in order to suppress the influence of the air amount change due to the thermal expansion of the throttle body as small as possible, for example, in the technique disclosed in Patent Document 1, the temperature of the throttle body is measured by a temperature sensor, and the measured throttle body temperature is measured. This is achieved by calculating the actual opening amount of the throttle valve in consideration of the thermal expansion of the throttle body using the temperature coefficient (expansion coefficient) of the throttle body based on the temperature.

  By the way, in idle speed control (ISC), feedback control of the air amount is performed so as to keep the intake air amount (throttle passage air amount) constant so that the engine speed matches the target speed. When the thermal expansion occurs, the idle rotation speed control is performed in a direction to decrease the air amount by feedback control so as to cancel out the increase in the air amount due to the thermal expansion.

  Further, although not described in Patent Document 1, in the feedback control, learning control is generally used together. However, if no special consideration is given to the thermal expansion of the throttle body in the learning control, the feedback control amount in the air amount decreasing direction due to the thermal expansion is held as it is as the learning value. Is directly reflected in the feedback control amount.

In other words, when the engine is stopped in a state where the feedback control amount in the air amount decreasing direction is learned at the time of thermal expansion of the throttle body, and then the engine is started (cold start) with the temperature of the throttle body being low, the throttle body However, the idling speed control is performed in the direction of decreasing the intake air amount based on the feedback control amount that reflects the learned value, even though the expansion of the engine is not generated or the expansion is low. As a result, a state in which a necessary amount of air cannot be obtained occurs, the engine speed during idling decreases and becomes unstable, and an engine stall may occur in some cases.
JP-A-3-294463

  An object of the present invention is to provide an idling engine speed control device for an internal combustion engine capable of performing idling engine speed control with high stability.

  According to the first aspect of the present invention, the idle speed control device for an internal combustion engine calculates a feedback control amount based on a deviation between the engine speed and the idle target speed, and learns the feedback control amount at a predetermined learning timing. As a value, feedback control of intake air amount adjustment by opening / closing a throttle valve in the throttle body is performed based on the feedback control amount and the learned value. The temperature detection means detects the temperature of the throttle body directly or indirectly, and the learning value calculation means removes the temperature change based on the throttle body temperature from the feedback control amount before holding the learning value. Learning values are calculated.

  Here, the amount of feedback control includes the amount of change in the temperature of the throttle body. Therefore, as the temperature of the throttle body rises, the throttle body is generally made of a material having a higher coefficient of thermal expansion than the throttle valve, so even if the throttle opening is the same, In comparison, the intake air amount (throttle passage air amount) increases. As a result, the feedback control amount is set in the direction of decreasing the intake air amount (the direction in which the throttle opening is closed). This feedback control amount is held as it is as the learning value, and the learned value is used as the feedback control amount from the next time. If this is reflected, there is a problem that the amount of intake air is excessively reduced when the internal combustion engine is cold started. Therefore, the learning value is calculated by removing the temperature change based on the temperature of the throttle body from the feedback control amount before holding the learning value, so the learning value is reduced by the intake air amount due to the temperature increase of the throttle body. The amount of control in the direction is not included, and the problem that the amount of intake air is excessively reduced at the next cold start of the internal combustion engine does not occur. As a result, the stability of idle speed control is increased.

  According to a second aspect of the present invention, in the first aspect of the present invention, an intake air temperature detecting means for detecting the temperature of the intake air and a cooling water temperature detection for detecting the temperature of the cooling water of the internal combustion engine that also circulates through the throttle body. And / or means. Then, the temperature of the throttle body is detected based on at least one of the temperature of the intake air and the temperature of the cooling water.

  That is, the temperature of the intake air and the temperature of the cooling water are parameters normally used for controlling the internal combustion engine, and the detection means for detecting them is usually attached to the vehicle. Therefore, it is not necessary to provide a special detection means for detecting the temperature of the throttle body, and the detection can be performed using the existing detection means, so that an increase in cost can be suppressed. In this case, the temperature of the throttle body can be detected from either the temperature of the intake air or the temperature of the cooling water. However, if the temperature of the throttle body is detected from these two temperatures, the detection accuracy is further improved. It will be expensive.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS An embodiment of the invention will be described below with reference to the drawings. In the present embodiment, an engine control system is constructed for an in-vehicle multi-cylinder gasoline engine that is an internal combustion engine, and FIG. 1 shows an overall schematic configuration of the engine control system.

  In the engine 10 shown in FIG. 1, an air cleaner 12 is provided at the most upstream portion of an intake pipe 11 having a substantially cylindrical shape, and an air flow meter 13 for detecting the amount of intake air is provided downstream of the air cleaner 12. Is provided. The air flow meter 13 is integrally provided with an intake air temperature sensor 20 for detecting the temperature of intake air (intake air temperature).

  In addition, an electronic throttle control device 30 is disposed on the downstream side of the air flow meter 13. As shown in FIG. 2, the electronic throttle control device 30 includes a throttle body 31 that has a hollow throttle bore 31 a interposed in the middle of the intake pipe 11 and serves as a base of the control device 30. A throttle actuator 32 such as a DC motor that is fixed, a throttle valve 14 that is disposed in the throttle bore 31a by the actuator 32 so as to be adjustable in opening, and a throttle opening for detecting the throttle opening of the throttle valve 14 Degree sensor 15. Further, the throttle body 31 is provided with a passage 31b through which engine cooling water flows to prevent the throttle valve 14 from freezing at a low temperature. The throttle body 31 is formed by aluminum die casting generally used as a constituent material of this member, and the throttle valve 14 is formed of brass generally used as a constituent material of this member.

  A surge tank 16 is provided downstream of the throttle valve 14, and an intake pipe pressure sensor 17 for detecting the intake pipe pressure is provided in the surge tank 16. The surge tank 16 is connected to an intake manifold 18 that introduces air into each cylinder of the engine 10. In the intake manifold 18, an electromagnetically driven fuel injection that injects fuel near the intake port of each cylinder. A valve 19 is attached.

  An intake valve 21 and an exhaust valve 22 are respectively provided in the intake port and the exhaust port of the engine 10, and an air / fuel mixture is introduced into the combustion chamber 23 by the opening operation of the intake valve 21, and the exhaust valve 22. By the opening operation, the exhaust gas after combustion is discharged to the exhaust pipe 24. The exhaust pipe 24 is provided with a catalyst 25 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas.

  A spark plug 26 is attached to the cylinder head of the engine 10 for each cylinder. A high voltage is applied to the spark plug 26 at a desired ignition timing through an ignition device (not shown) including an ignition coil. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 26, and the air-fuel mixture introduced into the combustion chamber 23 is ignited and used for combustion.

  Further, the cylinder block of the engine 10 includes a cooling water temperature sensor 27 that detects the temperature of engine cooling water that mainly circulates in the engine 10 (engine cooling water temperature Tw), and a predetermined crank angle of the engine (for example, 30). A crank angle sensor 28 for outputting a rectangular crank angle signal (with a CA period) is attached.

  The outputs of the various sensors described above are input to the ECU 40 that controls the engine. The ECU 40 is mainly composed of a microcomputer including a CPU 41, a ROM 42, a RAM 43, a backup RAM 44, and the like, and an engine operation detected by output signals of various sensors by executing various control programs stored in the ROM 42. The fuel injection amount of the fuel injection valve 19 and the ignition timing by the spark plug 26 are controlled according to the state.

  Further, the ECU 40 performs idle speed control (ISC) when the engine 10 is idling. Specifically, the ECU 40 detects the engine speed at that time and calculates the target idle speed, and the engine speed with respect to the target idle speed is converged so that the engine speed converges to the idle target speed. Based on the deviation, the feedback control amount of the intake air amount (throttle passage air amount) is calculated. The ECU 40 performs feedback control for adjusting the throttle opening using the calculated feedback control amount.

  Further, at the predetermined learning timing, the ECU 40 determines that the characteristic deviation has occurred when the feedback control amount exceeds the predetermined amount in this embodiment, and holds the feedback control amount at the time of determination in the backup RAM 44 as a learning value. . The backup RAM 44 functions as a backup memory that retains stored contents by supplying backup power even after the power supply to the ECU 40 is cut off by turning off the ignition switch, and can be replaced with an EEPROM. Then, the ECU 40 reflects the learned value held in the backup RAM 44 in the feedback control amount from the next time so that the feedback control amount changes around the zero center without the influence of change over time, machine difference variation, etc. The feedback control amount is optimized.

  Here, the above-described feedback control amount includes the temperature change of the throttle body 31. Therefore, as the temperature of the throttle body 31 rises, the throttle body 31 (made of aluminum die cast) has a larger coefficient of thermal expansion than the throttle valve 14 (made of brass), so the throttle opening is kept the same. However, the amount of intake air (the amount of air passing through the throttle) is increased as compared to the low temperature. As a result, the ECU 40 sets the feedback control amount in the direction of decreasing the intake air amount (the direction in which the throttle opening is closed). When reflected in the feedback control amount from the next time, there is a problem that the intake air amount is excessively reduced at the next cold start of the engine 10. For this reason, the ECU 40 according to the present embodiment updates the learning value as follows.

  The ECU 40 first detects the temperature of the throttle body 31 (throttle bore temperature Tb), and calculates the intake air amount change corresponding to the detected temperature change of the throttle bore temperature Tb from time to time. At this time, the ECU 40 indirectly detects the throttle bore temperature Tb based on the engine coolant temperature Tw detected by the coolant temperature sensor 27 and the engine room temperature Tr.

Incidentally, as described above, the throttle body 31 is provided with the passage 31b through which the engine cooling water flows in order to prevent the throttle valve 14 from freezing at a low temperature. Accordingly, it is considered that the throttle body 31 is greatly influenced by the engine room temperature Tr and the engine coolant temperature Tw, and its temperature changes. Note that the intake air temperature detected by the intake air temperature sensor 20 can be used as the engine room temperature Tr. Therefore, in this embodiment, the intake air temperature is used directly or multiplied by a coefficient. Then, when the throttle bore temperature Tb is obtained from the engine room temperature Tr and the engine coolant temperature Tw,

Tb = Tb [n−1] + α (Tb [n−1] −Tr) + β (Tw−Tb [n−1])

It becomes. However, Tb [n−1] is the throttle bore temperature Tb obtained in the processing flow of one cycle before (see FIG. 4), α and β are constants, and air in the engine room and engine cooling water, respectively. It is a heat receiving coefficient from. Thus, the ECU 40 estimates the throttle bore temperature Tb from time to time, and calculates the intake air amount change corresponding to the temperature change of the throttle bore temperature Tb. Then, at the learning timing, the ECU 40 removes the intake air amount change corresponding to the temperature change of the throttle bore temperature Tb calculated at that time from the feedback control amount at that time, and newly obtained in this way. The feedback control amount is held in the backup RAM 44 as a learning value. Thereby, as described above, the problem that the intake air amount is excessively reduced at the time of the cold start of the next engine 10 does not occur.

  Next, the feedback process and the learning value calculation process in the ISC of the ECU 40 are performed according to the process flow shown in FIGS. These processing flows are performed every predetermined time.

[Feedback process flow]
In step S101, it is determined whether or not the operating state of the engine 10 is an idle state. If it is determined not to be in the idle state, the subsequent processing is skipped and the process is terminated. On the other hand, if it is determined that the vehicle is in the idle state, the process proceeds to step S102.

  In step S102, an idle target speed that takes into account the operating state of the engine 10 is calculated. In step S103, the engine speed is detected. In step S104, the idle target speed and the engine speed are compared, and the deviation of the engine speed from the idle target speed is calculated.

  In step S105, a feedback control amount of the intake air amount based on the calculated deviation is calculated, and further, the feedback control amount is optimized by reflecting the learning value held in the backup RAM 44 (exclusion of change over time, machine difference variation, etc.). )I do.

  In step S106, the feedback control amount calculated in step S105 is output to the throttle actuator 32. The throttle actuator 32 adjusts the throttle opening to obtain the intake air amount based on the feedback control amount, and operates so that the engine speed converges to the idle target speed.

  In step S107, it is determined whether or not the feedback control amount calculated in step S105 exceeds a predetermined amount. If it is determined that the feedback control amount does not exceed the predetermined amount, it is determined that there is no characteristic deviation, and the subsequent processing is skipped and terminated. On the other hand, if it is determined that the feedback control amount exceeds the predetermined amount, it is determined that a characteristic deviation has occurred, and the process proceeds to step S108.

  In step S108, the learning value calculated in the learning value calculation processing flow shown in FIG. 4, that is, the feedback control amount obtained by removing the temperature change from the feedback control amount at the current determination is stored and stored in the backup RAM 44 as the learning value. The value is updated and the process is terminated.

[Learning value calculation processing flow]
In step S201, the throttle bore temperature Tb is estimated from the engine room temperature Tr calculated from the intake air temperature detected by the intake air temperature sensor 20 and the engine coolant temperature Tw detected by the coolant temperature sensor 27.

  In step S202, the change rate of the intake air amount (throttle passage air amount) with respect to the throttle bore temperature Tb is calculated from the intake air amount change rate calculation table shown in FIG.

  In step S203, the intake air amount detected by the air flow meter 13 is multiplied by the change rate of the intake air amount obtained in step S202 to calculate the intake air amount change accompanying the change in the throttle bore temperature Tb.

  In step S204, it is determined whether or not the operating state of the engine 10 is an idle state. If it is determined not to be in the idle state, the subsequent processing is skipped and the process is terminated. On the other hand, if it is determined that the vehicle is in the idle state, the process proceeds to step S205.

  In step S205, a temperature change corresponding to the intake air amount change is removed (for example, subtracted) from the feedback control amount calculated this time, and a learning value is calculated. This learning value is stored and held in the backup RAM 44 as described above, and is reflected in the feedback control amount from the next time.

  In this way, the ECU 40 eliminates the change in the temperature of the throttle body 31 (throttle bore temperature Tb) from the learned value, and performs idling speed control with high stability.

  According to the embodiment described above in detail, the following excellent effects can be obtained.

  In the present embodiment, the ECU 40 detects the temperature of the throttle body 31 (throttle bore temperature Tb) based on the engine room temperature Tr (substitute with the intake air temperature) and the engine coolant temperature Tw, and the throttle bore temperature Tb. The learning value obtained by removing the temperature change based on the feedback control amount is calculated, and the learning value is stored in the backup RAM 44. Therefore, the learning value does not include the control amount in the direction of decreasing the intake air amount due to the temperature rise of the throttle body 31, and there is a problem that the intake air amount is excessively reduced at the next cold start of the engine 10 as described above. Disappear. As a result, the stability of idle speed control is increased.

  Also, an intake air temperature sensor 20 for detecting an intake air temperature that substitutes for the engine room internal temperature Tr, and a cooling water temperature sensor for detecting the temperature of the engine 10 coolant that also circulates through the throttle body 31 (engine coolant temperature Tw). 27, and the ECU 40 detects the throttle bore temperature Tb based on these temperatures Tr and Tw. That is, the intake air temperature and the cooling water temperature Tw are parameters normally used for controlling the engine 10, and the sensors 20 and 27 for detecting them are normally attached to the vehicle. Therefore, it is not necessary to provide a special detection means for detecting the throttle bore temperature Tb, and the detection can be performed using the existing sensors 20 and 27, so that an increase in cost can be suppressed.

  In this case, the throttle bore temperature Tb can be detected from either the intake air temperature or the cooling water temperature Tw, but the ECU 40 of the present embodiment detects the throttle bore temperature Tb from these two temperatures. The detection accuracy of the throttle bore temperature Tb is higher.

  In addition, this invention is not limited to the content of description of the said embodiment, For example, you may implement as follows.

  In the above embodiment, the engine room temperature Tr is replaced with the intake air temperature detected by the intake air temperature sensor 20, but the engine room temperature Tr may be obtained using the intake air temperature and other detected temperatures. A detected temperature other than the intake air temperature may be used.

  In the above embodiment, the throttle bore temperature Tb is obtained from the engine room temperature Tr and the engine coolant temperature Tw. However, the throttle bore temperature Tb may be obtained from one of these temperatures Tr and Tw. Further, as shown in FIG. 2, a temperature sensor 33 that directly detects the temperature of the throttle body 31 may be provided, and a detection signal from the sensor 33 may be used.

  In the above embodiment, the electronic throttle control device 30 is implemented. However, the mechanical throttle control device 30a as shown in FIG. 6 may be implemented.

  Incidentally, the throttle control device 30a is mechanically operated in response to depression of an accelerator pedal (both not shown) to which the throttle valve 14 is connected via a wire. Further, an upstream side and a downstream side of the throttle bore 31a sandwiching the throttle valve 14 communicate with each other through a bypass passage 34, and an idle speed control valve (ISC valve) 35 is provided in the bypass passage 34. When the engine 10 is idling, the throttle valve 14 is fully closed, and the opening of the ISC valve 35 is adjusted by feedback control so that the engine speed converges to the idle target speed.

  Even in such a throttle control device 30a, when the temperature of the throttle body 31 rises, the throttle body 31 has a larger coefficient of thermal expansion than the throttle valve 14, and therefore the throttle opening degree is the same (in this case, the opening degree). However, the intake air amount (throttle passage air amount) increases compared to the low temperature. That is, since the same phenomenon as that of the electronic throttle control device 30 described above occurs, the present invention can be applied to this throttle control device 30a.

  In the above embodiment, the throttle body 31 is formed by aluminum die casting and the throttle valve 14 is formed by brass. However, the material constituting the throttle body 31 and the throttle valve 14 is not limited to this, Other metals and synthetic resins may be used.

  The processing flow shown in FIGS. 3 and 4 and the table shown in FIG. 5 used in the above embodiment are not limited to this, and may be appropriately changed.

It is a schematic block diagram of the engine control system in this Embodiment. It is a schematic block diagram of a throttle control device part. It is a flowchart which shows an ISC feedback process. It is a flowchart which shows an ISC learning value calculation process. It is a figure which shows the intake air amount change ratio calculation table. It is a schematic block diagram of the throttle-control apparatus part in another example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine (internal combustion engine), 14 ... Throttle valve, 20 ... Intake air temperature sensor (temperature detection means, intake air temperature detection means), 27 ... Cooling water temperature sensor (temperature detection means, cooling water temperature detection means), 30, 30a ... Throttle Control device (throttle control means), 31 ... throttle body, 40 ... ECU (feedback control amount calculation means, feedback control means, learning value calculation means), 44 ... backup RAM (learning value holding means).

Claims (2)

Throttle control means for adjusting the amount of intake air by opening and closing a throttle valve disposed inside the throttle body;
Feedback control amount calculation means for calculating a feedback control amount based on the deviation between the engine speed and the idle target speed;
Learning value holding means for holding the feedback control amount as a learning value at a predetermined learning timing;
Feedback control means for performing feedback control of the throttle control means based on the feedback control amount and the learning value;
An idling speed control device for an internal combustion engine comprising:
Temperature detecting means for directly or indirectly detecting the temperature of the throttle body;
Learning value calculation means for calculating the learning value by removing a temperature change based on the detected temperature of the throttle body from the feedback control amount before holding the learning value in the learning value holding means;
An idle speed control device for an internal combustion engine, comprising: Intake air temperature detecting means for detecting the temperature of the intake air;
The throttle body has a structure in which cooling water of the internal combustion engine circulates, and includes at least one of cooling water temperature detecting means for detecting the temperature of the cooling water,
2. The idle rotation of the internal combustion engine according to claim 1, wherein the temperature detecting unit indirectly detects the temperature of the throttle body based on at least one of a temperature of the intake air and a temperature of the cooling water. Number control device.

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