JP4345723B2 - Method for estimating the indicated mean effective pressure of an internal combustion engine - Google Patents

Description

  The present invention relates to a method for estimating an indicated mean effective pressure of an internal combustion engine.

  Patent Document 1 discloses a technique for calculating the indicated mean effective pressure based on the in-cylinder pressure detected for each predetermined crank rotation angle in a target section before and after the top dead center between the compression stroke and the expansion stroke.

Japanese Patent Laid-Open No. 9-329049

  However, in the calculation method of the indicated mean effective pressure in Patent Document 1, since measurement is performed every predetermined crank rotation negative for the target section before and after top dead center, even in a corresponding period of the compression stroke section before ignition. In-cylinder pressure is measured at every predetermined crank rotation angle. For this reason, in-cylinder pressure measurement is performed for each predetermined crank rotation angle even in a section that is not directly related to the combustion state, and there is a problem that the burden of calculation processing in the control system increases. In order to reduce this burden, it is conceivable to set the measurement target section short. However, if the measurement target section is shortened, the measurement section in the expansion stroke is also shortened, leading to a problem that the calculation accuracy is lowered. .

  An object of the present invention is to propose a method for estimating the indicated mean effective pressure with high accuracy while reducing the burden of arithmetic processing in the control system.

  In order to achieve the above object, in the method for estimating the indicated mean effective pressure of an internal combustion engine according to the present invention, the combustion cycle of the internal combustion engine is divided into a combustion zone extending from the end of the compression stroke to the middle of the expansion stroke, and a non-combustion zone other than the same The non-combustion section is divided into an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke, and an effective pressure index for the combustion section is calculated based on the calculation of the in-cylinder pressure sequentially measured in the combustion section. In the non-combustion section, the effective pressure index for each stroke is estimated according to the operating state of the engine, and the indicated mean effective pressure of the internal combustion engine is determined based on the effective pressure index for the combustion section and the effective pressure index for each stroke in the non-combustion section. It is characterized by seeking.

  In the method for estimating the indicated mean effective pressure of the internal combustion engine according to the present invention, the effective pressure index in the non-combustion section is obtained based on the intake pressure of the engine or the intake pressure and the rotational speed of the engine.

  In the method for estimating the indicated mean effective pressure of the internal combustion engine according to the present invention, the effective pressure index in the compression stroke in the non-combustion section and the effective pressure index in the expansion stroke in the non-combustion section are the in-cylinder pressure measured at a predetermined crank angle. It is characterized by being estimated based on this.

  In the method for estimating the indicated mean effective pressure of the internal combustion engine according to the present invention, when the internal combustion engine has four cylinders, the length of the combustion section in the compression stroke is set to be equal to or less than the length of the non-combustion section in the expansion stroke. It is characterized by that.

  In the method for estimating the indicated mean effective pressure of the internal combustion engine according to the present invention, the combustion section is set from the vicinity of BTDC 20 ° to the vicinity of ATDC 140 °.

  According to the present invention, since the in-cylinder pressure measured sequentially in the combustion zone from the end of the compression stroke to the middle of the expansion stroke is calculated, the effective pressure index in the combustion zone can be accurately calculated based on the actually measured value. Further, in the non-combustion section, the section is divided into an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke, and the effective pressure does not fluctuate greatly in each stroke. Since the effective pressure index of the stroke is estimated, the effective pressure index of each stroke in the non-combustion section can be efficiently estimated without requiring many measurements. For this reason, actual values are calculated for the combustion section and estimated for each stroke in the non-combustion section to obtain the indicated mean effective pressure of the internal combustion engine. The pressure can be determined.

According to the present invention, since the effective pressure index in the non-combustion section is obtained based on the intake pressure of the engine, the effective pressure index in the non-combustion section can be easily derived. Further, when the effective pressure index in the non-combustion section is obtained based on the intake pressure and the rotational speed of the engine, the effective pressure index in the non-combustion section can be derived more accurately.
According to the present invention, since the effective pressure index in the compression stroke in the non-combustion section is estimated based on the in-cylinder pressure measured at a predetermined crank angle, even in an internal combustion engine equipped with a variable valve timing mechanism, the variable valve timing The effective pressure index in the compression stroke in the non-combustion section can be appropriately estimated regardless of the mechanism phase.

  According to the present invention, the effective pressure index in the expansion stroke in the non-combustion section is estimated based on the in-cylinder pressure measured at a predetermined crank angle. Therefore, even if the ignition timing varies greatly, the effective pressure index is influenced by the ignition timing. Therefore, it is possible to appropriately estimate the effective pressure index in the expansion stroke in the non-combustion section.

  According to the present invention, since the length of the combustion section in the compression stroke is set to be equal to or less than the length of the non-combustion section in the expansion stroke, the calculation period of the in-cylinder pressure does not overlap between the cylinders, and the calculation load is reduced. It can be reduced efficiently.

  According to the present invention, since the combustion section is set from the vicinity of BTDC 20 ° to the vicinity of ATDC 140 °, the combustion section can be appropriately set, and the indicated mean effective pressure can be obtained with high accuracy while efficiently reducing the arithmetic processing. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The overall configuration will be described with reference to FIG. A spark plug 3 and an in-cylinder pressure sensor 4 as in-cylinder pressure detecting means are mounted on the upper part of the cylinder 2 of the engine which is an in-line four-cylinder internal combustion engine indicated by reference numeral 1 in FIG. Yes. In the present embodiment, the in-cylinder pressure sensor 4 is disposed in the vicinity of the intake valve 6. The in-cylinder pressure sensor 4 converts the combustion pressure in the cylinder into charges by a piezoelectric element, and outputs a charge output S to the charge amplifier 7. The charge amplifier 7 is a so-called charge-to-voltage conversion amplifier, converts the sensor output S into a voltage signal S and outputs the voltage signal S to the A / D converter 8. The A / D converter 8 converts the signal S input as an analog signal into a digital signal in synchronization with the crank angle, and outputs the digital signal to an engine control unit (hereinafter referred to as “ECU”) 10 serving as a control means. That is, the signal S becomes the pressure information S detected by the in-cylinder pressure sensor 4.

  The ECU 10 includes a voltage signal S detected by the pressure detection sensor 4, an intake pressure Pa (intake manifold pressure) detected by an intake pressure sensor 11 provided in the intake manifold, and an engine detected by a crank angle sensor 12. 1 crank angle Ca and a cylinder discrimination signal REF-i detected by a cylinder discrimination sensor 13 as cylinder discrimination means are input. The air flow sensor 11 and the crank angle sensor 12 constitute an operating state detection means 20. In this embodiment, the engine is a four-cylinder engine, and its combustion cycle is such that the intake process, the compression process, the expansion process, and the exhaust process complete one cycle at a crank angle of 720 ° as shown in FIG. .

  The crank angle sensor 7 outputs a reference signal Ca that becomes a [H] level pulse at a predetermined position before compression top dead center (TDC) of each cylinder, for example, BTDC 5 ° at every explosion interval (180 ° in a 4-cylinder engine). At the same time, a pulse signal of (H) level is output every unit angle (for example, 10 °) of the crank angle. The engine speed Ne can be known by counting the pulses of the signal Ca, and this process is performed by the control unit 5. In this embodiment, the cylinder discrimination sensor 13 discriminates a specific cylinder (for example, the first cylinder), and outputs a cylinder discrimination signal REF-i at a predetermined crank angle position before the compression top dead center of the specific cylinder.

  The ECU 10 is a known computer including a CPU 21, a ROM 22, a RAM 23, and an I / O port 24, which are connected to each other by a common bus 25. The ECU 10 includes a timer (not shown). The CPU 21 fetches necessary external data from the I / O port 24 in accordance with a program written in the ROM 22 in advance, and performs necessary processing values and the like while exchanging data with the RAM 23, as necessary. In response, the processed data is output to the I / O port 24. A signal from each sensor is input to the I / O port 24, an ignition signal Sp is output from the I / O port 24 to the spark plug 3, and an injection signal Si is output to the injector 14 for fuel injection. To do. That is, the ECU 10 has a function of performing ignition timing and fuel supply control based on each sensor information input, and estimating the indicated mean effective pressure in the cylinder, that is, in the combustion chamber 5. The ROM 22 stores basic ignition timing and basic fuel injection amount data (not shown) from the engine speed and the suction pressure Pa serving as load information.

  Next, estimation of the indicated mean effective pressure by the ECU 10 will be described. The estimation of the indicated mean effective pressure by the ECU 10 is executed for each cylinder. Here, one cylinder will be described.

  In this embodiment, the combustion cycle of the engine 1 has a section C as a combustion section extending from the end of the compression stroke to the middle of the expansion stroke, and a non-combustion section other than this section C, as shown in FIG. The non-combustion section is composed of section A, section B, section D, and section E. The section A corresponds to the intake stroke, the section B corresponds to the initial to middle period of the compression stroke, the section D corresponds to the late stage of the expansion stroke, and the section E corresponds to the exhaust stroke. The length C-1 of the combustion section in the compression stroke is set to be equal to or less than the section D that is the length of the non-combustion section in the expansion stroke.

  In the present embodiment, in these sections, in the section C that is the combustion section, the pressure signal S from the in-cylinder pressure sensor 4 is sequentially taken in every crank angle of 10 ° and integrated to calculate the effective pressure index Pi1 in the combustion section. In the non-combustion section, the operating state is determined from the engine speed Ne of the engine 1 and the suction pressure Pa, and the effective pressure indexes Si2 to Si4 in the sections A, B, D, and E are determined according to the operating state. And the effective pressure index Si1 of the combustion section and the effective pressure indices Si2 to Si4 of each stroke (each section A, B, D, E) in the non-combustion section are added to obtain the indicated mean effective pressure IMEP for one cycle. It is characterized by seeking. Here, the effective pressure index Si is also obtained from the absolute work / displacement amount in each section. In this embodiment, the section C is set from the vicinity of BTDC 20 ° to the vicinity of ATDC 140 °.

  As described above, the in-cylinder pressure in a specific section is obtained from the pressure signal S from the in-cylinder pressure sensor 4 except for the section C in which the intake manifold pressure and the in-cylinder pressure are subject to fluctuations due to combustion in one cycle (720 °). This is because the inventor of the present application has found a proportional relationship. Therefore, the map shown in FIG. 3 is stored in the ROM 22 of this embodiment. The map shown in FIG. 3 is a data map obtained by measuring the relationship between the intake manifold pressure and the in-cylinder pressure for each engine speed. The map shown in FIG. 3A shows the in-cylinder pressure in sections A and E (at the time of intake and exhaust) as pump loss kgf / cm 2 (Si1), and the map shown in FIG. 3B shows the section B (compression process). The in-cylinder pressure is indicated by the effective pressure index Si3 (kgf / cm2), and the map shown in FIG. 3C shows the in-cylinder pressure in the section D (late expansion stage) by the effective pressure index Si4 (kgf / cm2). It is.

  The ECU 10 adds the effective pressure index Pi1 of the combustion engine thus obtained and the effective pressure indices Si2 to 4 of the non-combustion engine to calculate the indicated mean effective pressure IMEP. The indicated mean effective pressure IMEP is used for grasping the generated torque of the engine 1 or detecting an unstable combustion state such as misfire, but the details are omitted here.

  The control process of such an estimation method is demonstrated using the flowchart shown in FIG. In this control process, an interrupt process is performed for each cylinder discrimination signal REF-i from the cylinder discrimination sensor 13, and the ignition timing is finally controlled here. In step F1, when the engine 1 is started, signals from the intake pressure sensor 11, the crank angle sensor 12, and the in-cylinder pressure detection sensor 4 are taken. In step F2, each section (steps A to E) of the engine 1 is determined.

  In step F3, effective pressure indexes Si1 to Si4 corresponding to the sections are obtained. In step F3, the effective pressure index Si2 is determined from the map of FIG. 3A when the sections A and E are reached, and the effective pressure index Si3 is determined from the map of FIG. The effective pressure index Si4 is obtained from the map of FIG. In the case of section C, the pressure information S from the in-cylinder pressure detection sensor 4 is integrated by the CPU 21 to calculate an effective pressure index Si1. The effective pressure indexes Si1 to Si4 obtained in step F3 are temporarily stored in the RAM 23, and are added (summed) in step F4 to calculate the indicated mean effective pressure IMEP.

  In this way, in the section C, which is the combustion section from the end of the compression stroke to the middle of the expansion stroke, the in-cylinder pressure detected by the in-cylinder pressure detection sensor 4 is integrated, so the effective pressure index Si1 in the section C is accurately calculated based on the actual measurement value. can do. Further, in section A, section B, section D, and section E, which are non-combustion sections, the section is divided into an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke, and the effective pressure varies greatly in each stroke. Focusing on the fact that the effective pressure indexes Si2 to Si4 of each stroke are estimated from the map shown in FIG. 3 according to the engine speed Ne and the intake pressure Pa, the non-combustion section does not require many measurements. The effective pressure indices Si2 to Si4 of each stroke in can be efficiently estimated. Further, the measured value is calculated for the section C, and the average effective pressure IMEP of the engine 1 is obtained from the sum of the effective pressure indexes Si1 to Si4 obtained by estimation for each stroke in the non-combustion section. The in-cylinder pressure measurement by 4 can be minimized, and the calculation load on the ECU 10 can be reduced.

  Since the length C-1 of the combustion section in the compression stroke is set to be equal to or less than the length of the non-combustion section (section D) in the expansion stroke, the calculation period of the in-cylinder pressure does not overlap between the cylinders, and the calculation in the ECU 10 The load can be reduced efficiently. Further, since the section C is set from around BTDC 20 ° to around ATDC 140 °, the section C can be set appropriately in one cycle, and the indicated mean effective pressure IMEP can be obtained with high accuracy while efficiently reducing the arithmetic processing in the ECU 10. Can do.

  In this embodiment, the effective pressure indexes Si2 to Si4 for each stroke in the non-combustion section are obtained based on the intake manifold pressure of the engine 1 and the engine speed Ne, so that the effective pressure indexes Si2 to Si4 for the non-combustion section are accurately derived. can do. In this embodiment, the effective pressure indexes Si2 to Si4 for each stroke in the non-combustion section are obtained based on the intake manifold pressure and the engine speed Ne, but may be simply obtained from the intake manifold pressure.

  The engine 1 according to this embodiment is not equipped with an exhaust gas recirculation device (hereinafter referred to as “EGR”) or a variable valve timing device (hereinafter referred to as “VVT”). is there. The estimation of the indicated mean effective pressure IMEP in that case will be described below.

The inventor of the present application calculates the effective pressure index Si1 by calculation from the in-cylinder pressure detection sensor 4 in the combustion section shown in FIG. 1 and estimates the effective pressure indices Si2 to Si4 from the map of FIG. 3 in the non-combustion section. It was examined whether it can be applied even when the amount and the VVT phase change. The examination result is shown in FIG. FIG. 5A is a diagram showing the relationship between the in-cylinder pressure at a crank angle of 320 ° (40 ° B of compression TDC) and the amount of change in the effective pressure index Si3 and the EGR amount in the section B. FIG. 5B is a diagram showing the relationship between the in-cylinder pressure at the crank angle of 320 ° (40 ° B of compression TDC) and the effective pressure index Si3 in the section B, and FIG. 5C is the crank angle of 320 ° (compression TDC). Is a diagram showing the relationship between the in-cylinder pressure at 40 ° B), the effective pressure index Si3 in the section B, and the VVT phase change.
(Effect of EGR amount)
The inventor of the present application considered that the engine speed was 1500 rpm and pb was −415 mmHg. As shown in FIG. 5B, the pump loss (sections A and E) hardly changed as the ERG amount changed. It was also found that there was almost no change in sections B and D as well. In section C, detection was possible every 10 ° crank angle as described above.
(Influence of VVT phase)
As shown in FIG. 5C, the pump loss (sections A and E) with respect to the change in the VVT phase (pb is constant) hardly changes as shown in FIG. 5C, but the effective pressure index Si3 in the section B changes with the VVT phase. Therefore, it was judged that estimation from intake manifold pressure was difficult. Although it can be estimated if the effective pressure index Si3 of the section B is provided for each VVT phase, this complicates the control.

  Therefore, paying attention to the in-cylinder pressure immediately before the start of combustion, the relationship between the in-cylinder pressure at the crank angle of 320 ° (compression TDC 40 ° B) and the effective pressure index Si3 in the section B was examined. It was found that the effective pressure index Si3 in the section B can be estimated even when the VVT changes, as shown in b).

  As a result of the examination, when the VVT phase is changed, as shown in FIG. 5C, the relationship between the intake manifold pressure and the effective pressure index Si3 in the section B changes. It was found that the effective pressure index Si3 in the section B can be estimated by measuring the in-cylinder pressure at 320 ° (40 ° B of compression TDC) and the in-cylinder pressure in the section B at one point.

Next, the inventor of the present application may have an ignition retard when the combustion start shown in FIG. 1 becomes an expansion stroke. At this time, when the intake manifold pressure changes, a throttle change occurs, the combustion interval shown in FIG. Whether the calculation of the effective pressure index Si1 by calculation from the in-cylinder pressure detection sensor 4 and the estimation of the effective pressure indexes Si2 to Si4 from the map of FIG. 3 in the non-combustion section were examined. The examination result is shown in FIG. FIG. 6A shows a comparison of the in-cylinder pressure change for each ignition timing in section B, section C, section D, and section E within one cycle, and FIG. FIG. 6C shows the relationship between the in-cylinder pressure at a crank angle of 500 ° (140 ° A of compression TDC) and the effective pressure indicator Si4 in the section D. About the influence of ignition over retard)
The inventor of the present application considered whether the estimation method of the present application can be applied even during the temperature increase control immediately after the cold start by changing the ignition timing while keeping the engine speed 1300 rpm and the intake manifold pressure constant at -230 mmHg.

  As a result, the effective pressure index Si4 in the section D changes with respect to the change in the ignition timing as shown in FIG. 6B, and it is difficult to estimate from the intake manifold pressure. It was found that the effective pressure index Si4 in the section D has a proportional relationship as shown in FIG. Therefore, in the present invention, in the section D, the effective pressure index Si4 is estimated with the in-cylinder pressure having a crank angle of 500 ° located in the section. When the engine speed was increased to a predetermined range by this method, it was found that the proportional relationship between the in-cylinder pressure at the crank angle of 500 ° and the effective pressure index Si4 in the section D was maintained.

Next, the inventor of the present application examined the estimation of the effective pressure index during the transition. This relates to a detection system of an effective pressure index in a transient state when the effective pressure index Si4 is estimated with an in-cylinder pressure with a crank angle of 500 ° in the section D. FIG. 7 is a diagram showing the characteristics of the effective pressure index Si4 when the load momentarily increases (for example, 3 kgf / cm ² → 8 kgf / cm ² ). As shown in FIG. 7, it was confirmed that the effective pressure index Si4 can be detected even when the intake manifold pressure change is relatively fast.

  That is, in this embodiment, the effective pressure index in the compression stroke in the non-combustion section is estimated based on the in-cylinder pressure measured at a predetermined crank angle of 320 °, so that the variable valve timing mounting (not shown) is mounted on the engine 1. Even in this case, it is possible to properly estimate the effective pressure index in the compression stroke in the non-combustion section regardless of the phase of the variable valve timing device. In addition, by estimating the effective pressure index in the expansion stroke in the non-combustion section based on the in-cylinder pressure measured at 500 °, which is a predetermined crank angle, the ignition timing can be adjusted even when the ignition timing varies greatly. Regardless, the effective pressure index in the expansion stroke in the non-combustion section can be properly estimated.

1 is a schematic view of a system of an internal combustion engine to which the present invention is applied. It is a characteristic view which shows the cylinder pressure change in 1 cycle of an internal combustion engine. It is a map which calculates | requires the effective pressure parameter | index of each process in a non-combustion area. It is a flowchart which shows one form of estimation control of an indicated mean effective pressure. It is a figure which shows the relationship between the change of an EGR amount and a VVT phase, and an effective pressure parameter | index. It is a figure which shows the relationship between ignition timing change and an effective pressure parameter | index. It is a figure which shows the characteristic of the effective pressure parameter | index at the time of a transition.

Explanation of symbols

1 Internal combustion engine A, B, E Non-combustion section C Combustion section C-1 Length of combustion section in compression stroke D Length of non-combustion section in expansion stroke (non-combustion section)
IMET Indicated mean effective pressure Si1 Effective pressure index for combustion section Si2 to Si4 Effective pressure index for non-combustion section

Claims (5)

The combustion cycle of the internal combustion engine is divided into a combustion section from the end of the compression stroke to the middle of the expansion stroke and a non-combustion section other than the combustion section, and the non-combustion section is divided into an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. In addition, the effective pressure index of the combustion section is calculated based on the calculation of the in-cylinder pressure sequentially measured in the combustion section, and the effective pressure index of each stroke is estimated based on the intake pressure of the engine in the non-combustion section. A method for estimating an indicated mean effective pressure of an internal combustion engine, comprising: obtaining an indicated mean effective pressure of the internal combustion engine based on an effective pressure index of the combustion section and an effective pressure index of each stroke in a non-combustion section. In the estimation method of the indicated mean effective pressure of the internal combustion engine according to claim 1,
A method for estimating an indicated mean effective pressure of an internal combustion engine, wherein the effective pressure index in the non-combustion section is obtained based on an intake pressure and a rotational speed of the engine. The combustion cycle of the internal combustion engine is divided into a combustion section from the end of the compression stroke to the middle of the expansion stroke and a non-combustion section other than the combustion section, and the non-combustion section is divided into an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. In addition, the effective pressure index of the combustion section is calculated based on the calculation of the in-cylinder pressure sequentially measured in the combustion section, and the effective pressure index in the compression stroke in the non-combustion section is a predetermined crank angle during the compression stroke. The effective pressure index in the expansion stroke in the non-combustion section is estimated based on the in-cylinder pressure measured at a predetermined crank angle during the expansion stroke based on the in-cylinder pressure measured in Step 1, and the effective pressure index and non-combustion in the combustion section are estimated. A method of estimating an indicated mean effective pressure of an internal combustion engine, comprising: obtaining an indicated mean effective pressure of the internal combustion engine based on an effective pressure index of each stroke in a section . In the estimation method of the indicated mean effective pressure of the internal combustion engine according to claim 1 or 3 ,
The internal combustion engine has four cylinders, and the length of the combustion section in the compression stroke is set to be equal to or less than the length of the non-combustion section in the expansion stroke. . In the estimation method of the indicated mean effective pressure of the internal combustion engine according to claim 1 or 3 ,
A method for estimating an indicated mean effective pressure of an internal combustion engine, wherein the combustion section is set from about BTDC 20 ° to about ATDC 140 ° .

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