Control device for internal combustion engines

Abstract

Provided is a control device for an internal combustion engine, the control device comprising a means for calculating an excess air ratio in which a table or the like can be set easily and that has excellent accuracy. The control device includes an excess ratio calculation unit (25) that calculates an excess air ratio λ on the basis of a voltage value VHG that increases with an increase in the excess air ratio λ obtained on the basis of oxygen concentration in the exhaust of the internal combustion engine. The excess ratio calculation unit (25) calculates a corresponding excess air ratio λ in response to the input of a voltage value VHGMA between a voltage value VHG5 corresponding to a rich-side boundary excess ratio LAMR and a voltage value VHG4 corresponding to a lean-side boundary excess ratio LAML. The excess air ratio λ has a characteristic that changes sensitively with respect to a change in the voltage value VHGMA as the voltage value VHGMA approaches the voltage value VHG5.

Description

Technical Field

[0001] The present invention relates to a control device for an internal combustion engine that controls the internal combustion engine based on a parameter obtained from the oxygen concentration in the exhaust gas.

Background Art

[0002] Conventionally, an oxygen sensor having a detection unit provided so as to be in contact with the exhaust of an internal combustion engine provided with a fuel injection valve and detecting the oxygen concentration in the exhaust gas is provided, and based on a parameter obtained based on the detection value from the detection unit, an air excess ratio λ as a parameter is known. An internal combustion engine control device that controls an internal combustion engine based on this is known (see, for example, Patent Document 1).

[0003] The device of Patent Document 1 includes a temperature detection unit that detects the temperature of a detection unit having a predetermined temperature characteristic, and based on the detection value and temperature of the detection unit, the detection value is linearly converted with respect to the air excess ratio while compensating for the temperature characteristic. An excess ratio calculation unit that calculates the air excess ratio λ of the exhaust using the converted data. As the detection unit (sensor element), a titania-type sensor element, which is a resistive oxygen sensor whose resistance value changes according to the oxygen concentration, is used.

[0004] The excess ratio calculation unit includes a limit threshold setting unit that sets a conversion limit threshold value for the linear conversion, and a data map that associates the temperature and detection value of the detection unit of the oxygen sensor with the air excess ratio λ of the exhaust. Then, the linearly converted data is acquired using this data map, and when the detection value or the linearly converted data is below the conversion limit threshold value, the linearly converted data is regarded as the air excess ratio λ of the exhaust.

[0005] On the other hand, when the detection value or the linearly converted data exceeds the conversion limit threshold value, the excess ratio calculation unit regards an alternative value R calculated based on the ratio of the execution time of fuel injection to the torque value as the air excess ratio λ instead of the linearly converted data.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-70442 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, the apparatus described in Patent Document 1 uses a sensor element whose resistance value changes significantly depending on the partial pressure of oxygen. Therefore, when setting the data map described above, it is difficult to test fixing the exhaust temperature and oxygen sensor output, and the amount of work required for trial and error using the actual equipment becomes burdensome.

[0008] In view of the problems of the prior art, the object of the present invention is to provide a control device for an internal combustion engine that has a means for calculating the excess air ratio with easy setup of tables and other components and good accuracy. [Means for solving the problem]

[0009] The control device for an internal combustion engine of the present invention is A control device for an internal combustion engine equipped with a fuel injection valve, comprising: a concentration detection unit that outputs a signal value indicating the oxygen concentration in the exhaust of the internal combustion engine; and a parameter detection unit that detects a parameter based on the signal value which changes in one direction as the parameter obtained based on the oxygen concentration increases, The concentration detection unit has a temperature characteristic in which the signal value fluctuates according to the temperature of the concentration detection unit. The parameter detection unit, A lookup table that associates the temperature and signal value corresponding to each predetermined parameter value of the parameter, wherein the range of possible values ​​for the temperature and signal value is divided into multiple regions bounded by each parameter value. Based on the input temperature and signal value, and the lookup table, depending on which of the regions the temperature and signal value belong to, the region is determined. suitable The method used to detect the aforementioned parameters There is, When a third signal value is input, which is between a first signal value corresponding to a first parameter and a second signal value corresponding to a second parameter that is greater than the first parameter, the third parameter, which is the parameter corresponding to the third signal value, is detected based on the first signal value, the first parameter, the second signal value, the second parameter, and the third signal value. The third parameter has the characteristic of changing more sensitively to changes in the third signal value as the third signal value approaches the first signal value. The second parameter is smaller than the parameter corresponding to the stoichiometric air-fuel ratio of the internal combustion engine. It is characterized by the following: The region to which the temperature and signal value belong among the plurality of regions may be determined by comparing the signal value with the signal value that indicates the boundary of each region for the temperature obtained from the lookup table.

[0010] In this configuration, the closer the input third signal value is to the first signal value, the more sensitive the corresponding third parameter becomes to change. That is, the third parameter does not change linearly with respect to the change in signal value during the interval in which the signal value changes from the first signal value to the second signal value, but rather changes along a curve in which the rate of change increases. Examples of parameters include the excess air ratio and the air-fuel ratio.

[0011] Therefore, by approximating the change in the third parameter in that interval with this curve (interpolation curve) (curve interpolation), and storing this approximation curve (interpolation curve) as a table or function, the third parameter can be detected with good accuracy.

[0012] Therefore, by appropriately setting the first signal value corresponding to the first parameter and the second signal value corresponding to the second parameter, the third parameter corresponding to the third signal value in the interval between the first and second signal values ​​can be determined with good accuracy through a simple process that requires little effort.

[0013] Furthermore, if a third signal value corresponding to an interval other than the interval between the first signal value and the second signal value is input, the third parameter corresponding to the third signal value can be obtained with minimal effort by using the method for calculating the alternative value R disclosed in Patent Document 1 or the method for performing linear interpolation.

[0014] Therefore, it is possible to provide a control device for an internal combustion engine including a parameter detection unit that can calculate a third parameter (excess air ratio or air-fuel ratio) using only a two-dimensional table with easy settings or a simple calculation formula, without requiring the setting of a three-dimensional data map that is complicated and labor-intensive.

[0015] Also, The second parameter is smaller than the parameter corresponding to the theoretical air-fuel ratio of the internal combustion engine Therefore, The first signal value corresponding to the first parameter and the second signal value corresponding to the second parameter can be appropriately set so that the third parameter has a characteristic of changing sensitively with respect to the change in the third signal value as the third signal value gets closer to the first signal value.

[0016] In the present invention, the signal value output by the concentration detection unit may be such that it becomes smaller as the temperature of the detection unit increases when the parameter is constant. Also in this case, the third parameter can be calculated using only a two-dimensional table with easy settings or a simple calculation formula, without requiring the setting of a three-dimensional data map that is complicated and labor-intensive. concentration 検出部の温度が高くなるほど小さくなるものであってもよい。この場合も、設定が煩雑で工数を要する三次元のデータマップの設定を必要とすることなく、設定が容易な二次元テーブルや簡単な計算式のみを用いて第3パラメータを算出することができる。

[0017] In the present invention, the parameter may be such that it becomes larger as the temperature of the detection unit increases when the signal value output by the concentration detection unit is constant. Also in this case, the third parameter can be calculated using only a two-dimensional table with easy settings or a simple calculation formula, without requiring the setting of a three-dimensional data map that is complicated and labor-intensive. concentration 検出部の温度が高くなるほど大きくなるものであってもよい。この場合も、設定が煩雑で工数を要する三次元のデータマップの設定を必要とすることなく、設定が容易な二次元テーブルや簡単な計算式のみを用いて第3パラメータを算出することができる。

[0018] In the present invention , the concentration Based on the detection value from the detection unit, it includes a voltage calculation unit that calculates a voltage value indicating the oxygen concentration, and a temperature calculation unit that calculates a temperature value indicating the temperature of the detection unit, the signal value is the voltage value calculated by the voltage calculation unit, and the one direction may be the direction in which the voltage value increases. concentration 検出部の温度を示す温度値を算出する温度算出部とを備え、前記信号値は、前記電圧算出部が算出する電圧値であり、前記一方向は、前記電圧値が大きくなる方向であってもよい。

[0019] According to this, concentration Even when using a titania type sensor element as the detection unit, the third parameter can be calculated using only a two-dimensional table with easy settings or a simple calculation formula without the need for the complicated settings and man-hours required for setting a three-dimensional data map.

[0020] In the present invention, for the detection of the third parameter, the first signal value is set as VHGR, the second signal value is set as VHGL, and the third signal value is set as VHGM, and the following formula PN=(VHGM-VHGR)÷(VHGL-VHGR) The coefficient PN obtained by λ addition value is associated with PNLAMADD, and from the table, the PNLAMADD corresponding to the coefficient PN for the input third signal value is obtained. Further, the value of the first parameter is set as LAMR, the value of the second parameter is set as LAML, and PARAM3 as the third parameter is calculated by the following formula λ addition value PARAM3=[(LAML-LAMR)×PNLAMADD]+LAMR This may be done. According to this, by storing a table associating the coefficient PN and

[0021] PNLAMADD, the third parameter PARAM3 corresponding to the third signal value VHGM between the first signal value VHGR and the second signal value VHGL can be detected with good accuracy. λ addition value

Brief Description of Drawings

[0022] [Figure 1] It is a schematic diagram showing the configuration of the main part of an internal combustion engine equipped with a control device according to an embodiment of the present invention. [Figure 2] It is a block diagram showing the main configuration in the ECU of the internal combustion engine in FIG. 1. [Figure 3] It is a diagram showing each divided region A1 to A7 to which each calculation method is applied when the excess air ratio calculation unit in the ECU in FIG. 2 calculates the excess air ratio λ. [Figure 4]This figure shows the characteristics of the voltage value VHG with respect to the air excess ratio λ (λ-voltage characteristics (Tα)) for regions A1 to A7 in Figure 3, when the temperature value T input to the excess ratio calculation unit in Figure 3 is a temperature Tα that is higher than T2 and lower than T3. [Figure 5] This flowchart shows the excess rate calculation process in the excess rate calculation unit of the ECU shown in Figure 2. [Figure 6] This figure shows an example of a table that associates the coefficient PN used in the excess rate calculation process in Figure 5 with the λ sum value PNLAMADD. [Modes for carrying out the invention]

[0023] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 shows the configuration of the main part of a four-stroke internal combustion engine equipped with a control device for an internal combustion engine according to one embodiment of the present invention. As shown in the figure, the engine body 1 of this internal combustion engine includes an intake pipe 2 provided at the intake port and a throttle valve 3 provided in the intake pipe 2 that adjusts the amount of intake air supplied from the air cleaner 4 to the intake port according to the opening degree.

[0024] The throttle valve 3 is equipped with a throttle sensor 5 that detects the degree of opening of the throttle valve 3. A fuel injector 6 is provided near the intake port of the intake manifold 2 to inject fuel. Fuel is pumped to the fuel injector 6 from a fuel tank (not shown) by a fuel pump. The intake manifold 2 is equipped with an intake pressure sensor 7 that detects the intake pressure in the intake manifold 2 and an intake air temperature sensor 8 that detects the temperature of the intake air in the intake manifold 2.

[0025] Inside the exhaust pipe 10 connected to the exhaust port of the engine body 1, a catalyst 11 is provided to reduce unburned components in the exhaust gas from the exhaust pipe 10, and an oxygen sensor 12 is provided to detect the oxygen concentration in the exhaust gas. A spark plug 13 connected to an ignition device 14 is fixed to the engine body 1. When the ECU (electronic control unit) 15 issues a command to the ignition device 14 regarding the ignition timing, a spark discharge occurs in the cylinder combustion chamber of the engine body 1.

[0026] The ECU15 receives analog voltages representing the detected values ​​from the throttle sensor 5, intake pressure sensor 7, intake air temperature sensor 8, oxygen sensor 12, coolant temperature sensor 17, and atmospheric pressure sensor 20, which detects atmospheric pressure. The fuel injector 6 is also connected to the ECU15.

[0027] The ECU 15 also receives a signal from the crank angle sensor 19 indicating the rotational angle position of the crankshaft 18. Specifically, the crank angle sensor 19 magnetically or optically detects multiple protrusions provided at predetermined angle intervals (for example, 15 degrees) on the outer circumference of the rotor 19a, which rotates in conjunction with the crankshaft 18, using a pickup 19b positioned near the outer circumference of the rotor 19a. The pickup 19b generates a pulse (crank signal) for each predetermined angle rotation of the crankshaft 18.

[0028] Specifically, the crank angle sensor 19 outputs a signal indicating the reference angle to the ECU 15 each time the piston 9 reaches top dead center, or each time the crankshaft 18 rotates 360 degrees.

[0029] Figure 2 shows the main components of the ECU 15. As shown in the figure, the oxygen sensor 12 that supplies a detection signal for the oxygen concentration in the exhaust gas to the ECU 15 comprises a sensor element 12a, which is provided in contact with the exhaust gas of the internal combustion engine and acts as a detection unit to detect the oxygen concentration in the exhaust gas, and a sensor heater 12b adjacent to the sensor element 12a that heats the sensor element 12a.

[0030] The sensor element 12a has a temperature characteristic in which the detected value changes according to the temperature of the sensor element 12a. In this embodiment, the sensor element 12a used is a titania-type sensor element, which is a resistive oxygen sensor whose resistance value changes according to the oxygen concentration.

[0031] The ECU15 includes a heater controller 22 that controls the sensor heater 12b, a temperature calculation unit 23 that calculates a temperature value T indicating the temperature of the sensor element 12a, and a voltage calculation unit 24 that converts the output signal of the sensor element 12a into a voltage value VHG indicating the oxygen concentration in the exhaust gas.

[0032] The heater controller 22 controls the temperature of the sensor heater 12b by controlling the current I supplied to the sensor heater 12b from a power source (battery) (not shown) using pulse width modulation (PWM) control by the ECU 15. The temperature calculation unit 23 calculates the temperature value T by, for example, reading the resistance value of the sensor heater 12b with the ECU 15.

[0033] Furthermore, the ECU 15 includes a rotational speed calculation unit 27 that calculates the rotational speed NE and angular velocity NETC of the internal combustion engine based on the detection results of the crank angle sensor 19, and an excess ratio calculation unit 25 that calculates the excess air ratio λ based on the temperature value T from the temperature calculation unit 23, the voltage value VHG from the voltage calculation unit 24, and the angular velocity NETC from the rotational speed calculation unit 27.

[0034] Furthermore, the ECU 15 includes a target value calculation unit 28 that calculates a target air excess ratio λcmd based on an estimated value of the amount of stored oxygen in the catalyst 11, a basic injection amount calculation unit 29 that calculates a basic injection amount BJ based on the rotational speed NE from the rotational speed calculation unit 27 and the pressure PM in the intake pipe 2 from the intake pressure sensor 7, a feedback coefficient calculation unit 30 that finds a feedback coefficient k to correct the basic fuel injection amount BJ calculated by the basic injection amount calculation unit 29 in order to match the air excess ratio λ calculated by the excess ratio calculation unit 25 to the target air excess ratio λcmd, and an injection amount calculation unit 31 that calculates an injection amount Ti based on the feedback coefficient k and the basic injection amount BJ, and also operates the fuel injection valve 6.

[0035] In the feedback coefficient calculation unit 30, PID control is performed based on a comparison between the excess air ratio λ and the target excess air ratio λcmd to calculate the feedback coefficient k. Based on the injection amount Ti calculated by the injection amount calculation unit 31 based on the feedback coefficient k and the basic injection amount BJ, the fuel injection valve 6 is opened for a time corresponding to this, and an amount of fuel corresponding to the feedback coefficient k of the PID control based on the comparison between the excess air ratio λ and the target excess air ratio λcmd is injected into the cylinder combustion chamber of the engine body 1.

[0036] Figure 3 shows the seven divided regions to which each calculation method is applied when the excess ratio calculation unit 25, which acts as a parameter detection unit, calculates the air excess ratio λ. These seven regions A1 to A7 are formed by dividing a region consisting of the horizontal axis scale for the temperature value T calculated by the temperature calculation unit 23 and the vertical axis scale value for the voltage value VHG calculated by the voltage calculation unit 24 into six graph curves that represent six predetermined air excess ratios λ.

[0037] For example, λ1, λ2, λ3, λ4, λ5, and λ6 are adopted as the six predetermined air excess ratios λ. The six graph curves representing each air excess ratio λ are composed of six lookup tables, namely lookup tables TB1 to TB6, which associate the voltage value VHG with the temperature value T for each air excess ratio λ, starting from the lean side. Note that in Figure 3, λ1 > λ2 > 1.000 > λ3 > λ4 > λ5 > λ6, and T1 <T2<T3<T4<T5である。

[0038] As can be seen from Figure 3, the voltage value VHG, as a signal value, has the characteristic of decreasing as the temperature T of the sensor element 12a increases, when the excess air ratio λ, as a parameter, is constant. Conversely, the excess air ratio λ has the characteristic of increasing as the temperature T increases, when the voltage value VHG is constant.

[0039] Figure 4 shows the characteristics of the voltage value VHG with respect to the excess air ratio λ when the temperature value T is higher than T2 and lower than T3 (temperature Tα), corresponding to seven regions A1 to A7 obtained by dividing the system from the lean side using the six graph curves (six excess air ratios λ). Note that in Figure 4, VHG11 > 0. When the temperature value T from the temperature calculation unit 23 is, for example, Tα, the excess air ratio calculation unit 25 calculates the excess air ratio λ corresponding to the voltage value VHG input from the voltage calculation unit 24, depending on which of the regions A1 to A7 shown in Figure 4 the voltage value VHG falls into, using a method corresponding to the region.

[0040] Figure 5 shows the excess ratio calculation process in the excess ratio calculation unit 25 for calculating the air excess ratio λ. The control by the ECU 15, including this excess ratio calculation process, is executed in synchronization with the stroke of the internal combustion engine based on a pulse signal from the crank angle sensor 19 indicating the rotational angle position of the crankshaft 18.

[0041] When the excess rate calculation process is started, in step S1, the voltage value VHG is read from the voltage calculation unit 24. Next, in step S2, the voltage value VHGMA is obtained by applying a moving average process to the read voltage value VHG.

[0042] Next, in step S3, the temperature value T of the sensor element 12a of the oxygen sensor 12 is read from the temperature calculation unit 23. Then, in step S4, based on the read temperature value T, voltage values ​​VHG1 to VHG6 are obtained from each lookup table TB1 to TB6 corresponding to the air excess ratio λ shown by the six graph curves described above. The voltage values ​​VHG1 to VHG6 indicate the boundaries of the seven regions A1 to A7 described above at the read temperature value T.

[0043] Next, in step S5, the voltage values ​​VHG1 to VHG6 are compared with the voltage value VHGMA calculated in step S2 to determine whether the voltage value VHGMA corresponds to region A1 (VHGMA ≥ VHG1). If it is determined that it corresponds to region A1, in step S6, the excess air ratio λ is calculated according to the operating conditions of the internal combustion engine. Specifically, the method disclosed in the above-mentioned Patent Document 1 can be used.

[0044] Specifically, the fuel injection time by the fuel injector 6 when the excess air ratio λ is richer than in region A1 is Ti1, the torque value calculated based on the crank angular velocity NEC of the internal combustion engine is TQ1, the excess air ratio λb that separates region A1 from region A2 is Ti2, and the injection amount when the excess air ratio λ reaches the value corresponding to region A1 is TQ2, and the torque is calculated using the following equation (1). λ=((Ti1÷Ti2)÷(TQ1÷TQ2))×λb (1)

[0045] After calculating this air excess ratio λ, the excess ratio calculation process is terminated. Note that as the air excess ratio λ in this case, a value slightly larger than 1 may be adopted during normal times, and an even larger value may be adopted during fuel cut.

[0046] When it is determined in step S5 that the voltage value VHGMA does not correspond to region A1 (VHGMA < VHG1), in step S7, it is determined whether the voltage value VHGMA corresponds to any of regions A2, A3, A4, and A6. When it is determined that it corresponds to any of them, in step S8, the air excess ratio λ corresponding to the voltage value VHGMA is calculated by linear interpolation.

[0047] Specifically, the lean-side value of the air excess ratio λ that divides the region A2, A3, A4, or A6 corresponding to the voltage value VHGMA is defined as the lean-side excess ratio LAML, the rich-side value is defined as the rich-side excess ratio LAMR, the voltage value of the corresponding lean-side look-up table is defined as the lean-side voltage value VHGL, and the rich-side voltage value is defined as the rich-side voltage value VHGR. The air excess ratio λ corresponding to the voltage value VHGMA is calculated by the following formula (2), and the excess ratio calculation process is terminated. λ = [(LAML - LAMR) × (VHGMA - VHGR) ÷ (VHGL - VHGR)]] + LAMR (2)

[0048] When it is determined in step S7 that it does not correspond to any of regions A2, A3, A4, and A6, in step S9, it is determined whether the voltage value VHGMA corresponds to region A5 (VHG4 > VHGMA ≥ VHG5). When it is determined that it corresponds to region A5, in step S10, the air excess ratio λ corresponding to the voltage value VHGMA is calculated by curve interpolation, and the excess ratio calculation process is terminated.

[0049] FIG. 6 shows an example of a table that can be used when calculating the air excess ratio λ by curve complementation in step S10. This table associates the coefficient PN of the search ratio with the λ addition value PNLAMADD. However, in FIG. 6, 0 < PNLAMADD1 < PNLAMADD2 < PNLAMADD3 < PNLAMADD4.

[0050] The calculation of the air excess ratio λ in step S10 is performed by obtaining the λ addition value PNLAMADD corresponding to the coefficient PN calculated by the following equation (3) from the table in FIG. 6, and using the air excess ratio λ values of the lean side boundary and the rich side boundary of region A5 as the lean side boundary excess ratio LAML and the rich side boundary excess ratio LAMR, respectively, and using the following equation (4). PN = (VHGMA - VHG5) ÷ (VHG4 - VHG5) (3) λ = [(LAML - LAMR) × PNLAMADD] + LAMR (4)

[0051] If it is determined in step S9 that the voltage value VHGMA does not correspond to region A5, then in step S11, it is determined whether the voltage value VHGMA corresponds to region A7 (VHGMA < VHG6). If it is determined that it does not correspond to region A7, the excess ratio calculation process is terminated as it is. If it is determined that it corresponds to region A7, then in step S12, a predetermined lower limit value for the air excess ratio, for example, the above-mentioned λ6, is set as the air excess ratio λ, and the excess ratio calculation process is terminated.

[0052] As described above, according to the present embodiment, with the temperature value T and the voltage value VHG of the sensor element 12a as the horizontal axis and the vertical axis, six graph curves showing six air excess ratios λ are represented and divided into seven regions A1 to A7 from the lean side. For the air excess ratio λ of region A1, according to the above-mentioned equation (1), for regions A2, A3, A4, and A6, by complementary calculation, for region A5, by the table in FIG. 6 and the above-mentioned equations (3) and (4), and for the air excess ratio λ of region A7, by setting a predetermined value, the air excess ratio λ of each region can be obtained.

[0053] Furthermore, since the lean-side boundary excess ratio LAML (second parameter) in region A5 is smaller than the value of the air excess ratio λ (=1) corresponding to the stoichiometric air-fuel ratio of an internal combustion engine, the voltage value VHG5 (first signal value) corresponding to the rich-side boundary excess ratio LAMR (first parameter) in region A5 and the voltage value VHG4 (second signal value) corresponding to the lean-side boundary excess ratio LAML (second parameter) in region A5 can be appropriately set such that the closer the voltage value VHGMA (third signal value) is to the voltage value VHG5 (first signal value), the more sensitive the corresponding air excess ratio λ (third parameter) becomes to changes in the voltage value VHGMA (third signal value).

[0054] This allows for the calculation of the excess air ratio λ when the voltage value VHGMA corresponds to region A5 with good accuracy using the table in Figure 6 and the curve approximation using equations (3) and (4) described above. Therefore, the excess air ratio λ when the voltage value VHGMA corresponds to region A5 can also be obtained without the need to use a complex three-dimensional map that represents the temperature value T, voltage value VHG, and excess air ratio λ of the sensor element 12a.

[0055] Although embodiments of the present invention have been described above, the present invention is not limited thereto. For example, in the calculation of the excess air ratio λ when the voltage value VHGMA corresponds to region A5, the coefficient PN is λ addition value When calculating PNLAMADD, instead of using the table in Figure 6, use the approximation formula (PNLAMADD=F(PN)) and the coefficient PN λ addition value You may also want to find PNLAMADD. [Explanation of symbols]

[0056] 1...Engine body, 2...Intake pipe, 3...Throttle valve, 4...Air cleaner, 5...Throttle sensor, 6...Fuel injector, 7...Intake pressure sensor, 8...Intake air temperature sensor, 9...Piston, 10...Exhaust pipe, 11...Catalytic converter, 12...Oxygen sensor, 12a...Sensor element, 12b...Sensor heater, 13...Spark plug, 14...Ignition system, 15...ECU (Electronic Control Unit), 17...Coolant temperature sensor, 18...Crankshaft, 19 ...crank angle sensor, 19a...rotor, 19b...pickup, 20...atmospheric pressure sensor, 22...heater controller, 23...temperature calculation unit, 24...voltage calculation unit, 25...excess rate calculation unit, 26...alternative value calculation unit, 27...rotation speed calculation unit, 28...target value calculation unit, 29...basic injection amount calculation unit, 30...feedback coefficient calculation unit, 31...injection amount calculation unit, A1~A7...region, TB1~TB6...lookup table.

Claims

1. A control device for an internal combustion engine equipped with a fuel injection valve, comprising: a concentration detection unit that outputs a signal value indicating the oxygen concentration in the exhaust of the internal combustion engine; and a parameter detection unit that detects a parameter based on the signal value which changes in one direction as the parameter obtained based on the oxygen concentration increases, The concentration detection unit has a temperature characteristic in which the signal value fluctuates according to the temperature of the concentration detection unit. The parameter detection unit, A lookup table that associates the temperature and signal value corresponding to each predetermined parameter value of the parameter, wherein the range of possible values ​​for the temperature and signal value is divided into multiple regions bounded by each parameter value. Based on the input temperature and signal value, and the lookup table, the parameters are detected in a manner corresponding to the region, depending on which of the plurality of regions the temperature and signal value belong to. When a third signal value is input, which is between a first signal value corresponding to a first parameter and a second signal value corresponding to a second parameter that is greater than the first parameter, the third parameter, which is the parameter corresponding to the third signal value, is detected based on the first signal value, the first parameter, the second signal value, the second parameter, and the third signal value. The third parameter has the characteristic of changing more sensitively to changes in the third signal value as the third signal value approaches the first signal value. A control device for an internal combustion engine, characterized in that the second parameter is smaller than the parameter corresponding to the stoichiometric air-fuel ratio of the internal combustion engine.

2. The control device for an internal combustion engine according to claim 1, characterized in that the temperature and the signal value are determined to belong to one of the plurality of regions by comparing the signal value with the signal value indicating the boundary of each region for the temperature obtained from the lookup table.

3. The control device for an internal combustion engine according to claim 1, characterized in that, when the parameter is constant, the signal value decreases as the temperature of the concentration detection unit increases, and when the signal value is constant, the parameter increases as the temperature of the concentration detection unit increases.

4. A voltage calculation unit calculates a voltage value indicating the oxygen concentration based on the value detected from the concentration detection unit, The system includes a temperature calculation unit that calculates a temperature value indicating the temperature of the concentration detection unit, The aforementioned signal value is a voltage value calculated by the voltage calculation unit. The control device for an internal combustion engine according to claim 1, characterized in that the aforementioned one direction is the direction in which the voltage value increases.

5. The detection of the third parameter is performed using the following formula, where the first signal value is VHGR, the second signal value is VHGL, and the third signal value is VHGM. PN=(VHGM-VHGR)÷(VHGL-VHGR) From a table that associates the coefficient PN obtained with the λ-add value PNLAMADD, the λ-add value PNLAMADD corresponding to the coefficient PN for the input third signal value is determined, and further, the value of the first parameter is set to LAMR, the value of the second parameter to LAML, and the third parameter PARAM3 is set to the following equation PARAM3=[(LAML-LAMR)×PNLAMADD]+LAMR The control device for an internal combustion engine according to claim 1, characterized in that it is performed by calculation.

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