JP2007064008A - Valve temperature estimating device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose a valve temperature estimating device capable of accurately estimating the valve temperature in response to an operation condition. <P>SOLUTION: This valve temperature estimating device of an internal combustion engine is characterized by calculating a basic value TVSTD of the valve temperature on the basis of the suction air volume Qa, an engine speed Ne and the engine cooling water temperature TWN, and calculating a correction value TVHOS of the valve temperature on the basis of the engine speed Ne and the target equivalent ratio TFBYA, and calculating the valve temperature TV by using the balance temperature TVH of correcting its basic value by the correction value and a time constant TCONST based on the suction air volume Qa. Since the valve temperature is calculated in response to the suction air volume, the engine speed and the target equivalent ratio of reflecting the operation condition, the valve temperature can be highly accurately estimated in conformity with the operation condition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an internal combustion engine, and more particularly to a technique for estimating a valve temperature for air-fuel ratio control of an air-fuel mixture.

In order to control the air-fuel ratio of the air-fuel mixture as accurately as possible in an internal combustion engine, a technique for estimating the valve temperature on the intake side as described in Patent Documents 1 to 3 has been proposed. The technique described in Patent Document 1 calculates the valve temperature based on the elapsed time after starting. In the technique described in Patent Document 2, the valve temperature is calculated from the engine coolant temperature and the number of ignitions. And the technique of patent document 3 is calculating the valve temperature from engine cooling water temperature, catalyst temperature, and oil temperature (physical temperature different from cooling water).
JP-A-8-49581 (paragraphs 0027 to 0028) JP-A-8-61115 (paragraphs 0027 to 0028) JP-A-9-177578 (paragraphs 0024 to 0027)

  The above-described conventional valve temperature estimation apparatus has an improvement in that the error cannot be ignored because the temperature cannot be estimated according to the operating conditions. That is, in the case of the technique described in Patent Document 1, the valve temperature is obtained simply by adding the correction value for the elapsed time after the start to the engine coolant temperature, and a fine temperature estimation according to the operating conditions after the start is performed. Cannot be performed, and a large error may occur. In this case, it is necessary to store a correction value for each elapsed time for each coolant temperature at the time of starting, and the memory capacity and calculation load are large. Further, in the case of the technique described in Patent Document 2, the valve temperature is calculated from the engine coolant temperature and the number of ignitions, but it cannot cope with the operating conditions in which the intake air amount and the target equivalent ratio change even with the same number of ignitions. Large errors can occur. Furthermore, in the case of the technique described in Patent Document 3, the initial value of the valve temperature at the time of starting is only predicted from the temperature difference between the engine coolant temperature, the catalyst temperature, and the oil temperature. Temperature estimation cannot be performed, and a large error may occur.

  In view of such improvements, the present invention proposes a valve temperature estimation device that can accurately estimate the valve temperature according to operating conditions.

  The valve temperature estimating apparatus for an internal combustion engine according to the present invention calculates a basic value of the valve temperature based on the intake air amount and the engine speed, calculates a correction value of the valve temperature based on the target equivalence ratio, and calculates the basic value. The valve temperature is calculated by correcting with a correction value.

  According to the valve temperature estimation device of the present invention, the valve temperature is calculated according to the intake air amount, the engine rotation speed, and the target equivalence ratio reflecting the operation conditions. Estimation is possible.

FIG. 1 schematically shows an embodiment of a multi-cylinder gasoline engine provided with a valve temperature estimating device according to the present invention.
The cylinder head of the engine is provided with an intake valve 1 and an exhaust valve 2 each having a variable valve mechanism around a spark plug for each cylinder. The lift characteristics (open / close timing) of the intake valve 1 and the exhaust valve 2 change the phase of the cams 5 and 6 with respect to the crankshaft by the variable valve solenoids 3 and 4 provided on the intake side and the exhaust side, respectively. It can be adjusted by controlling the timing. The cam angles of the cams 5 and 6 are measured by cam sensors 7 and 8.

  An electronic control throttle valve 11 for controlling the amount of intake air is provided in the intake passage 10 from the air cleaner to the intake port through the surge tank and manifold, and an air flow meter 12 and a downstream side of the electronic control throttle valve 11 are provided. In addition, an intake pressure sensor 13 for each cylinder is installed. An injector 14 faces the intake port immediately before the intake valve 1 to form an air-fuel mixture. The injector 14 may be a direct injection type that directly injects into the combustion chamber. On the other hand, an exhaust pressure sensor 21, an exhaust temperature sensor 22, and an oxygen sensor 23 for each cylinder are provided in the exhaust passage 20 from the exhaust port through the manifold and the catalyst to the muffler.

The operations of the variable valve solenoids 3 and 4, the electronically controlled throttle valve 11, and the injector 14 in the engine are controlled by an ECU (engine control unit) 30, and in synchronization with this, the ECU 30 performs an internal power coil built-in ignition coil 31 (ignition plug). In other words, the ignition timing is also controlled.
For these controls, the ECU 30 receives signals from various sensors. That is, the cam sensors 7 and 8 for detecting the cam angle, the air flow meter 12 for detecting the intake air amount, the intake pressure sensor 13 for detecting the intake pressure, the exhaust pressure sensor 21 for detecting the exhaust pressure, and the exhaust temperature sensor for detecting the exhaust temperature. 22, an oxygen sensor 23 for detecting the oxygen concentration in the exhaust, a water temperature sensor 32 for detecting the temperature of the engine cooling water, a crank angle sensor 33 for detecting the crank angle and obtaining the engine rotation speed, and the wall temperature of the cylinder head Receiving the outputs of the wall temperature sensor 34 to be detected and the accelerator opening sensor 35 to detect the accelerator opening, arithmetic processing is executed.

  For example, when the air-fuel ratio of the air-fuel mixture is controlled by the variable valve solenoids 3, 4, the electronically controlled throttle valve 11, the injector 14, etc., the ECU 30 estimates the temperature of the valves 1, 2 and executes more accurate control. . A valve temperature estimation device for this purpose will be described by taking the intake valve 1 as an example. It should be understood that the valve temperature estimation device for the exhaust valve 2 can be implemented with the same configuration.

In this example, the ECU 30 serving as a calculation means for calculating the valve temperature calculates the valve temperature TV based on the intake air amount Qa, the engine rotational speed Ne, and the target equivalent ratio TFBYA as follows. The configuration of the arithmetic processing executed by the ECU 30 is shown in a block diagram in FIG.
First, in the valve temperature basic reference value calculation block B1, the ECU 30 calculates the valve temperature basic reference value TVSTD0 from the current intake air amount Qa and the engine rotational speed Ne. In this example, the corresponding basic reference value TVSTD0 is read from the basic reference value map MTVSTD0 stored in advance in a memory such as a ROM. The basic reference value map MTVSTD0 is obtained by mapping the basic reference value TVSTD0 in relation to the intake air amount Qa and the engine rotational speed Ne. The higher the both values, the higher the basic reference value TVSTD0 tends to be. At this time, the target equivalent ratio TFBYA is 1.

  When the basic reference value TVSTD0 is calculated, the engine coolant temperature TWN is added to the basic reference value TVSTD0 as the temperature of the valve installation site (cylinder head in this embodiment) in the valve temperature basic value calculation block B2. The basic value TVSTD is calculated. Thereby, the basic value TVSTD corresponding to the current operating condition is calculated. However, this basic value TVSTD indicates the equilibrium temperature when the target equivalent ratio TFBYA is 1. It is possible to input the wall temperature of the cylinder head by the wall temperature sensor 34 as the temperature of the valve installation site. However, measuring the temperature of the engine coolant flowing through the cylinder head will result in a temperature closer to the valve. Since it is caught, it is preferable.

  On the other hand, in the valve temperature correction value calculation block B3, the ECU 30 calculates the valve temperature correction value TVHOS based on the current engine speed Ne and the target equivalent ratio TFBYA. In this example, the corresponding correction value TVHOS is read from the correction value map MTVHOS stored in advance in a memory such as a ROM. The correction value map MTVHOS is obtained by mapping the correction value TVHOS with respect to the target equivalent ratio TFBYA for each engine speed Ne, and the correction value TVHOS rises and falls according to the engine speed Ne even at the same target equivalent ratio TFBYA. On the contrary, even if the engine speed Ne is the same, the correction value TVHOS also changes if the target equivalent ratio TFBYA changes.

The calculated correction value TVHOS is multiplied by the basic value TVSTD in the valve equilibrium temperature calculation block B4, and the valve equilibrium temperature TVH taking into account the target equivalence ratio is calculated. In this way, by correcting the basic value TVSTD with the correction value TVHOS, it is possible to calculate a highly accurate valve temperature that closely corresponds to the operating conditions.
Further, in the valve temperature time constant calculation block B5, the ECU 30 calculates the valve temperature time constant TCONST according to the intake air amount Qa. In this example, a corresponding time constant TCONST is read from a time constant map MTCONST stored in advance in a memory such as a ROM. The time constant map MTCONST is obtained by mapping the time constant TCONST to the intake air amount Qa, and the time constant TCONST tends to increase as the intake air amount Qa increases. This time constant TCONST represents the transient response of the valve temperature to the operating conditions.

  The ECU 30 calculates the valve temperature TV in the valve temperature calculation block B6 using the equilibrium temperature TVH from the equilibrium temperature calculation block B4 and the time constant TCONST from the time constant calculation block B5. The valve temperature TV can be calculated by Formula 1: TV = TVH × TCONST + TVz × (1−TCONST). By calculating the current equilibrium temperature TVH using the time constant TCONST and the previous value TVz of the valve temperature, it is possible to calculate the valve temperature with higher accuracy corresponding to the transient operating condition change.

By executing such arithmetic processing, it is possible to calculate a fine valve temperature in accordance with changes in operating conditions, and the accuracy is greatly improved. In addition, the memory capacity and calculation load for storing the correction value for each elapsed time for each coolant temperature at the time of starting are unnecessary, and the estimation accuracy is increased by simple calculation without increasing the memory capacity and calculation load. .
The flowchart of the calculation process is shown in FIGS.

First, in step S1 of FIG. 3, the ECU 30 confirms whether or not a fuel cut is being performed, for example, during an accelerator-off deceleration operation. If the fuel is being cut, combustion is not performed. Therefore, the process proceeds to step S2, and the engine coolant temperature TWN is read. In step S3, the engine coolant temperature TWN is set to the equilibrium temperature TVH.
On the other hand, if the fuel is not being cut, the process proceeds to step S4, where the ECU 30 reads the intake air amount Qa and the engine rotational speed Ne. In step S5, the corresponding basic reference value TVSTD0 is calculated from the basic reference value map MTVSTD0 (basic reference value calculation block B1 in FIG. 2). In step S6, the ECU 30 reads the engine coolant temperature TWN. In step S7, the ECU 30 calculates the basic value TVSTD from TVSTD0 + TWN (basic value calculation block B2 in FIG. 2).

  Subsequently (or in parallel), in step S8, the ECU 30 reads the target equivalent ratio TFBYA and the engine speed Ne. In step S9, a correction value TVHOS is calculated from the correction value map MTVHOS (correction value calculation block B3 in FIG. 2). In step S10, an equilibrium temperature TVH is calculated by TVSTD × TVHOS (equilibrium temperature calculation block B4 in FIG. 2). ).

  Following the calculation of the equilibrium temperature TVH (or in parallel), the ECU 30 executes the calculation flow of the time constant TCONST in FIG. First, in step S20, it is checked whether the fuel is being cut. If the fuel is being cut, the process proceeds to step S21, and a previously stored time constant TCONSTF dedicated for the fuel cut is read. On the other hand, if the fuel is not being cut, the process proceeds to step S22, where the ECU 30 reads the intake air amount Qa, and calculates the corresponding time constant TCONST from the time constant map MTCONST in step S23 (time constant calculation block B5 in FIG. 2).

When the equilibrium temperature TVH and the time constant TCONST are calculated, the operation flow of FIG. 5 is performed, and in step S30, the ECU 30 reads the equilibrium temperature TVH, the time constant TCONST, and the valve temperature previous value TVz. In step S31, the valve temperature TV is calculated by performing the calculation according to Equation 1 (valve temperature calculation block B6 in FIG. 2).
The highly accurate valve temperature TV calculated in this way can also be used, for example, in a valve clearance amount estimating device as described below. This greatly contributes to the calculation of the actual valve clearance amount with high accuracy.

  In controlling the variable valve solenoids 3 and 4 and the associated ignition timing by the ECU 30, it is also important to calculate the actual valve clearance amount according to the operating conditions. A valve clearance amount estimation apparatus for this purpose will be described by taking the intake valve 1 as an example. It should be understood that the valve clearance amount estimation device for the exhaust valve 2 can be implemented with the same configuration.

  In this example, the ECU 30, which is a calculation means for calculating the actual valve clearance amount, inputs the engine coolant temperature TWN by the water temperature sensor 32 as the temperature of the valve installation part in the cylinder in order to calculate the reference amount VCLRSTD of the valve clearance. . Further, the ECU 30 calculates the valve clearance correction amount VCLRVAR using the valve temperature TV by the valve temperature estimation device. Then, the ECU 30 calculates the actual valve clearance amount under the current operating conditions by correcting the calculated reference amount of the valve clearance with the correction amount. A flowchart of the calculation processing is shown in FIG. 6, and the configuration of the calculation processing is shown in a block diagram in FIG.

  When the estimation process of the actual valve clearance amount is started with a predetermined period or valve timing control, the ECU 30 reads the engine coolant temperature TWN by the water temperature sensor 32 in step S40. In step S41, a reference amount VCLRSTD of the valve clearance is calculated from the read engine coolant temperature TWN. This reference amount calculation is executed in the reference amount calculation block B10 in FIG.

  In the reference amount calculation block B10, a reference amount map MSTD in which the valve coolant reference amount VCLRSTD is associated with the engine coolant temperature TWN is stored in the ROM of the ECU 30, and the reference amount map MSTD is determined according to the actually measured engine coolant temperature TWN. The corresponding reference amount VCLRSTD is read out by accessing. The reference amount map MSTD is created in advance by associating the amount of change in valve clearance due to thermal deformation of the valve clearance-related components with the engine coolant temperature TWN and storing it in the memory. The valve clearance-related parts are, for example, a cylinder head, a valve, a valve seat, a valve guide, a valve lifter, a retainer, and a cam base circle. The total change amount of the valve clearance due to thermal deformation of these valve clearance-related parts is a reference amount VCLRSTD. It is stored in the reference amount map MSTD.

  In this way, by creating and accessing a map in advance, the amount of thermal deformation of the cylinder head and the valve can be calculated, or the amount of thermal deformation can be calculated separately for the umbrella radial direction and the axial direction of the valve. This eliminates the need to perform calculation, simplifies the calculation process, and reduces the calculation load and memory capacity. In addition, by calculating the reference amount from the engine coolant temperature, simple processing is sufficient.

When the calculation of the reference amount VCLRSTD of the valve clearance is completed (or in parallel), the valve temperature TV is read in step S42, and the correction amount VCLRVAR of the valve clearance is calculated in the subsequent step S43. This correction amount calculation is executed in the correction amount calculation block B11 in FIG.
In the correction amount calculation block B11, the valve temperature TV of the intake valve 1, the engine coolant temperature TWN, the thermal expansion coefficient THEREXP of the intake valve 1 known in advance, and the stem length VSTEM and the stem length of the intake valve 1 are also calculated. Using the umbrella diameter ratio VRATIO, the correction amount VCLRVAR is calculated by Formula 2: VCLRVAR = VSTEM × VRATIO × THEREX × (TV−TWN).

  In Formula 2, the reference amount VCLRSTD obtained from the engine coolant temperature TWN is calculated by calculating the difference between the engine coolant temperature and the actual valve temperature by TV-TWN and multiplying this by the thermal expansion coefficient THEREXP. A correction value that increases accuracy is calculated so as to be more in line with the actual value. Then, the shape and physical property value of the intake valve 1 is multiplied by the stem length VSTEM (initial value) and the ratio of the umbrella diameter to the stem length VRATIO to obtain a coefficient, which is multiplied by THEREXP × (TV-TWN). Thus, the correction amount VCLRVAR is calculated. By performing the calculation of VSTEM × VRATIO, it is possible to easily process with a simplified model calculation without solving the heat receiving and radiating of the valve. Therefore, it is not necessary to calculate the amount of thermal deformation separately for the umbrella diameter direction and the axial direction of the valve, the calculation process is simplified, and the calculation load and the memory capacity can be reduced.

  When the correction amount VCLRVAR is calculated, the process proceeds to step S44 to calculate the actual valve clearance amount VCL. In the actual valve clearance amount calculation block B12 of FIG. 7 that executes this calculation, the correction amount VCLRVAR is added to the reference amount VCLRSTD for correction, and finally the actual valve clearance amount VCL is calculated.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows embodiment of the engine provided with the valve temperature estimation apparatus which concerns on this invention. The block diagram explaining the structure of valve temperature calculation. The flowchart which showed an example of the equilibrium temperature calculation process in valve temperature calculation processing. The flowchart which showed an example of the time constant calculation process in valve temperature calculation processing. The flowchart which showed an example of the valve temperature calculation process in valve temperature calculation processing. The flowchart which showed an example of the actual valve clearance amount calculation process. The block diagram explaining the structure of actual valve clearance amount calculation.

Explanation of symbols

1, 2 Valve 3, 4 Variable valve solenoid 5, 6 Cam 7, 8 Cam sensor 12 Air flow meter 30 ECU
32 Water temperature sensor 33 Crank angle sensor B1 Valve temperature basic reference value calculation block B2 Valve temperature basic value calculation block B3 Valve temperature correction value calculation block B4 Valve equilibrium temperature calculation block B5 Valve temperature time constant calculation block B6 Valve temperature calculation block

Claims (7)

  Calculate the basic value of the valve temperature based on the intake air amount and the engine speed, calculate the correction value of the valve temperature based on the target equivalence ratio, and calculate the valve temperature by correcting the basic value with the correction value A valve temperature estimation device for an internal combustion engine, characterized in that:   2. The valve temperature estimating device for an internal combustion engine according to claim 1, wherein the basic value is calculated based on an intake air amount, an engine rotation speed, and an engine coolant temperature.   3. The internal combustion engine according to claim 2, wherein the basic value is calculated by calculating the basic reference value based on the intake air amount and the engine rotational speed and then calculating the basic reference value and the engine coolant temperature. Valve temperature estimation device.   The valve temperature estimation device for an internal combustion engine according to any one of claims 1 to 3, wherein the basic value is a value when the target equivalent ratio is 1.   The valve temperature estimation device for an internal combustion engine according to any one of claims 1 to 4, wherein the correction value is calculated based on an engine speed and a target equivalent ratio.   The valve temperature of the internal combustion engine according to any one of claims 1 to 5, wherein a valve temperature is a result of a response change of a value obtained by correcting the basic value with the correction value with a predetermined time constant. Estimating device.   7. The valve temperature estimating device for an internal combustion engine according to claim 6, wherein the time constant is calculated based on an intake air amount.

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