JPH11210546A - Compression top dead center detecting device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the compression top dead center with high accuracy by detecting a crank angle and cylinder internal pressure. SOLUTION: The unit crank angle (every 1 deg.) of a crankshaft 5 is detected by a crank angle sensor 10 according to detecting teeth formed around a disc 6. The cylinder internal pressure of cylinders ξ1-ξ4 is detected by cylinder internal pressure sensors 41-44. A controller 7 obtains the maximum cylinder internal pressure of each cylinder on the basis of cylinder internal pressure data of each cylinder detected in a noncombustion state such as the time of start-up cranking start of a multiple cylinder engine, and determines the crank angle at the time of detecting maximum cylinder internal pressure, as the compression top dead center of each cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compression top dead center detecting device for detecting a compression top dead center of an engine based on a cylinder pressure detected by a cylinder pressure sensor.

[0002]

2. Description of the Related Art In a gasoline engine or a diesel engine, in order to improve engine performance such as reduction of fuel consumption and improvement of exhaust gas characteristics, a fuel ignition timing or a fuel injection timing and a fuel injection amount are determined by an engine operating condition. Is controlled so as to match the target value with high accuracy in accordance with the following. For this reason, it has been proposed to electronically control the operation of the engine with high accuracy in terms of the fuel injection timing, the fuel injection amount, and the like.

[0003] The detection of the crank angle in the engine is performed by
Conventionally, this is performed by a top dead center detection mechanism as shown in FIG. In this top dead center detection mechanism, a TDC (Top Dead Center:
In order to obtain a top dead center signal corresponding to the compression top dead center of the two cylinders with one rotation of the crankshaft, two teeth 51 opposed in the diameter direction of the gear are attached to an electromagnetic pickup. It is detected by the sensor 52 of the formula. T
In addition to the DC detection gear 50, a gear (not shown) for detecting a crank angle for each 1 ° is also provided. The mounting angles of the detection gear 50 with respect to the crankshaft and the sensor 51 with respect to the frame are set in advance so that the sensor 52 detects the teeth 51 of the detection gear 50 corresponding to the top dead center. Further, instead of the TDC, a signal before the top dead center which is arranged ahead of the TDC by a predetermined angle may be detected. Further, in a multi-cylinder engine, it is necessary to determine which cylinder should be subjected to fuel injection. Therefore, in an engine driven in four cycles, for example, a specific angle on a camshaft corresponding to a specific cylinder is required. Is provided with a cylinder discriminating sensor for detecting a reference signal and outputting a reference signal.

[0004] However, an error due to an assembly error when assembling these crank angle detecting gears to the crankshaft and an error in mounting the sensor are inevitable, and the detection of the crank angle corresponding to the top dead center lacks accuracy. I was If the mounting accuracy of the above-mentioned sensor is improved, the detection accuracy is also improved, but the adjustment work for that is complicated and the productivity of engine assembly is affected. On the other hand, with the recent technological development, engine operation control has been performed electronically with high accuracy. However, when the accuracy of detecting the crank angle, which is the basis of such control, is low, high accuracy of the engine is required. Electronic control cannot be fully exhibited. For example, when a top dead center detection error occurs, the heat generation rate changes as shown in FIG. FIG. 16 is a graph showing the influence of the heat release rate in the combustion chamber on the top dead center error as viewed from the crank angle. For example, if the detection error of the top dead center at the crank angle is shifted by + 1 ° or -1 ° to the front side of the top dead center, the fuel is injected earlier and the heat is increased as compared with the case where the detection is normally performed (graph a). The incidence tends to increase (graph b) or decrease (graph c). As described above, if an error occurs in the detection of the crank angle, the target engine operation state cannot be obtained in the entire operation range of the engine, and the performance of the engine cannot be fully utilized.

[0005] Therefore, it is necessary to detect the mounting error of the top dead center sensor by some means and reflect the error in the control of the engine. 64-11819 and Japanese Patent Publication No. 3-19500. That is, Japanese Patent Publication No. 64-11819 discloses that a crank angle sensor detects a unit rotation angle of a crankshaft, and a pressure in a cylinder formed by a piezoelectric element during non-combustion such as during inertial running or starting cranking. Detects with a sensor, performs waveform processing such as differentiation on the pressure waveform, detects the peak value of the in-cylinder pressure, and regards the time at which the peak value is detected as the piston top dead center, assuming a predetermined crank angle reference. The correct top dead center position is obtained by correcting the set value of the top dead center from the reference position by pulse counting or time division from the position to the top dead center detection time, and the corrected top dead center position is obtained. There is disclosed an engine crank position detecting device capable of controlling a timing such as a fuel immediate injection timing based on the above.

In Japanese Patent Publication No. 3-19500,
For example, when the engine is in a non-combustion state according to a specific operating state such as deceleration or cranking, the pressure due to combustion is excluded, and the maximum pressure timing of the in-cylinder pressure in this non-combustion state is the compression top dead center. The top dead center, which is the true top dead center, is detected based on the in-cylinder pressure detected by the sensor, and the top dead center signal that the crank angle sensor outputs based on the initial mounting state is output. There is disclosed an engine crank angle detection device that corrects using the maximum pressure timing and detects an accurate crank angle based on the corrected top dead center signal.

[0007]

As in the above-mentioned prior art, detection of the conventional crank angle, in particular, the compression top dead center (TDC), is performed in advance from the reference angle of the crank angle.
An angle is set, and a true TDC angle is obtained by correcting a preset TDC angle based on the fact that the actual top dead center is the maximum pressure detection time of the in-cylinder pressure in a non-combustion state of the engine. Therefore, as a sensor, a sensor for detecting a crank angle reference (for example, a crank angle for every 1 °) and a sensor for detecting an angular position serving as a reference of the crank angle are basically required. If these sensors are optical sensors or magnetic sensors, it is necessary to provide different types of through holes or teeth and two photo sensors or pickups on one rotating plate. Further, in the case of a multi-cylinder engine driven in four cycles, in order to determine the top dead center of a specific cylinder, for example, it is necessary to attach a cylinder discrimination sensor in connection with the camshaft.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem, and to control fuel injection or the like in accordance with a top dead center or a predetermined angular position before the top dead center. There is no need to provide a sensor that determines the reference crank angle or a cylinder discrimination sensor that discriminates a specific cylinder in a multi-cylinder engine. It detects the compression top dead center of the engine with high accuracy only by detecting the in-cylinder pressure. To provide a compression top dead center detection device for an engine.

The present invention provides a crank angle sensor for detecting a crank angle of an engine, an in-cylinder pressure sensor provided in each cylinder of the engine for detecting an in-cylinder pressure of each cylinder, and an output of the in-cylinder pressure sensor. A compression top dead center of the engine comprising a controller for determining the maximum in-cylinder pressure of each of the cylinders in the non-combustion state of the engine based on the above and determining the crank angle at the maximum in-cylinder pressure as the compression top dead center of each of the cylinders The present invention relates to a point detection device.

In the compression top dead center detecting apparatus for an engine, the crank angle sensor is a sensor for detecting a crank angle for each unit crank angle, and the in-cylinder pressure sensor is a sensor for detecting the crank angle by the crank angle sensor. The in-cylinder pressure is detected in synchronization with the detection.

In the compression top dead center detecting apparatus for an engine, the non-combustion state of the engine is a state of the engine at the start of engine start cranking.
The engine is driven in four cycles, and the controller stores a maximum value of the in-cylinder pressure detected by the in-cylinder pressure sensor during at least two rotations of the crankshaft of the engine as a maximum in-cylinder pressure.

In the compression top dead center detection device for an engine, the controller may be configured to detect the in-cylinder pressure detected by the in-cylinder pressure sensor after at least a half rotation immediately after the start of rotation of the crankshaft. Is adopted as data for obtaining the maximum in-cylinder pressure.

In the compression top dead center detecting apparatus for an engine, the controller determines a predetermined value as a reference for fuel injection into each cylinder based on the crank angle determined as the compression top dead center. Determines the crank angle.

Further, in the compression top dead center detecting apparatus for an engine, the predetermined crank angle may be a crank angle before the top dead center, which is reversely above a predetermined angle from the compression top dead center in each cylinder. , And a reference crank angle for cylinder discrimination.

According to the compression top dead center detecting apparatus for an engine according to the present invention, the crank angle sensor detects the crank angle of the engine at, for example, a unit crank angle (every 1 °), and the cylinder provided for each cylinder of the engine. The internal pressure sensor
The in-cylinder pressure of each cylinder is detected. The controller calculates the maximum in-cylinder pressure of each cylinder based on the output of the in-cylinder pressure sensor in the non-combustion state of the engine, and determines the crank angle when the maximum in-cylinder pressure is detected as the compression top dead center of each cylinder. I do.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An engine compression top dead center detecting device according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an outline of an engine to which a compression top dead center detecting device for an engine according to the present invention is applied. FIG. 2 is a graph showing an outline of in-cylinder pressure and injector processing in each injector with the passage of the crank angle of the engine shown in FIG. The engine shown in FIG. 1 is a multi-cylinder engine 1 having four cylinders, and has four cylinders # 1 to #.
4, injectors 31, 32, 33, and 34 for injecting fuel into combustion chambers (not shown) formed therein, respectively.
(When collectively referred to, 3 is used). Fuel is supplied to the injector 3 from a pressure-controlled common rail 22 through a branch pipe 23 that forms a part of a fuel flow path. The fuel is stored in the common rail 22 in a control state in which the pressure is increased to a predetermined pressure, and the injector 3 injects the fuel into the corresponding combustion chamber at an appropriate injection timing and injection amount under the control of the controller 7 which is an electronic control unit. . The common rail fuel injection system itself is conventionally known, and further detailed description will be omitted.

At the shaft end of the crankshaft 5 of the multi-cylinder engine 1, a disk 6 having detection teeth formed corresponding to each crank angle (1 °) is attached. A crank angle sensor 10 is mounted on a vehicle body frame (not shown) in the vicinity of the disk 6. Crank angle sensor 10
Is the crank angle 1 ° according to the rotation of the crankshaft 5.
The detection signal is output to the controller 7 every time. In-cylinder pressure sensors 41, 42, 43, and 44 as pressure detecting means for detecting the pressure (in-cylinder pressure) in the combustion chambers facing the respective combustion chambers of the four cylinders # 1 to # 4. 4
Is used). Signals representing the in-cylinder pressure of each of the cylinders # 1 to # 4 detected by the in-cylinder pressure sensor 4 are amplified by the charge amplifier 8 and then output to the controller 7.

The combustion order i of the multi-cylinder engine 1 is as follows: if the cylinder number n is # 1 to # 4 according to the row arrangement, # 1 → #
The order is 3 → # 4 → # 2. The crank angle θ is a count value of a crank angle that counts 1 every 1 ° of the crank angle unless otherwise specified. In an engine driven in four cycles, the crank angle θ is 0 at the compression top dead center of the # 1 cylinder, and the crankshaft 5 rotates twice, that is, makes a full cycle with the count value 719 (the crank angle for each cylinder is No) crank angle. The four graphs in the upper part of FIG. 2 show changes in the in-cylinder pressure Pc with the passage of the crank angle θ of each of the cylinders # 1 to # 4.

In each of the cylinders # 1 to # 4, when the combustion of fuel is not performed at the beginning of cranking or the like, the compression / expansion strokes are successively performed in the order described above. The cylinder is in the compression stroke. For cylinder # 1, 180 ° before compression top dead center to 18 ° after compression top dead center
Up to 0 °, that is, 1 when the crank angle θ is 540 or more
When it is less than 80, the # 1 cylinder reaches the compression / expansion stroke, and the in-cylinder pressure Pc greatly changes before and after the compression top dead center. At the exhaust top dead center, a remarkable pressure rise unlike the compression top dead center does not occur. Therefore, by setting a threshold value, the compression top dead center and the exhaust top dead center can be distinguished. When fuel burns, compression top dead center does not generally occur at the highest pressure due to pressure rise due to combustion. The fuel injection timing and the injection period can be controlled based on the in-cylinder pressure data that is sequentially detected and stored with the progress of the crank angle. The main processing is calculated within a predetermined time from 180 ° after the compression top dead center, and the processing of the injector 31 is performed based on the next TDC interrupt signal. The lower graph in FIG. 2 schematically shows the order and timing of processing of each injector 3 in each of the cylinders # 1 to # 4 as the crank angle θ increases.

FIG. 3 shows control of the multi-cylinder engine 1 including fuel injection of the multi-cylinder engine 1 which receives signals detected by various sensors including an in-cylinder pressure sensor and outputs a control signal to the injector 3 and the like. FIG. 2 is a block diagram of a controller 7. The rotation sensor of the multi-cylinder engine 1 includes only a crank angle sensor 10 that detects a crank angle every 1 °. In the controller 7, in addition to the crank angle sensor 10, the operating state of the multi-cylinder engine 1 is represented by, for example, an accelerator opening sensor 11 for detecting an accelerator opening, and a fuel pressure provided on a common rail 22. A (common rail pressure) sensor 12 and a water temperature sensor 13 for detecting the temperature of engine cooling water are input to a central processing unit (CPU) 14.

The cylinder pressure Pc detected by the cylinder pressure sensor 4
Is input to an AD converter 19 and converted into a digital signal. The digital signal is a DSP (digital signal) that can be added and subtracted at high speed through a DSP bus 18.
al processor) 15. CPU1
Between the DSP 4 and the DSP 15 is the CPU 1
4 and the DSP 15 via a dual-port memory 16 which is a common RAM that can be read and written from either side. The CPU 14 and the dual port memory 16 are connected through a CPU bus 17, and the DSP 15 and the dual port memory 16 are connected through a DSP bus 18.

The CPU 14 controls the DSP 1 with respect to the information indicating the operating state of the multi-cylinder engine 1 which is directly input from the sensors 10 to 13 and the in-cylinder pressure from the in-cylinder pressure sensor 4.
The calculation is performed based on the results and the like processed in step 5, and the engine output and the exhaust gas characteristics are provided corresponding to each of the cylinders # 1 to # 4 so as to be optimal according to the operating state. Fuel injection timing of the injectors 31 to 34
Control related to fuel injection, such as fuel injection amount and fuel injection pressure control. The DSP 15 performs high-speed addition and subtraction processing of digital signals related to the in-cylinder pressure Pc. Since this process is a digital process, the differentiation and integration of the in-cylinder pressure Pc can be similarly calculated at a high speed. Further, the CPU 15 controls the discharge amount of the variable fuel pump 20 to control the pressure of the common rail 22, and controls the EGR valve 21 to control the exhaust gas circulation amount.

The CPU 14 performs the main processing shown in FIG. FIG. 4 shows a CPU in the controller shown in FIG.
14 is a flowchart showing a main process of No. 14; This main processing includes the following steps. (1) Initialization of the CPU 14 is performed (steps 1, S
Abbreviated as 1. same as below). (2) Process the sensor signal (S2). As shown in FIG. 4, processing of detection signals from various sensors input to the CPU 14 is performed. (3) Based on the information obtained in the signal processing performed in S2, the amount of fuel to be injected by each injector 3, that is, the fuel injection amount is calculated (S3). In the fuel injection amount characteristic map which is determined in advance by the operating state of the multi-cylinder engine 1, that is, the accelerator opening and the engine speed and stored in the memory, the current operating state, that is, the accelerator opening sensor 11 detects the current operating state. A target fuel injection amount corresponding to the current accelerator opening and the engine speed is obtained. (4) Further, based on the information obtained in the signal processing performed in S2, the timing at which each injector 3 should inject fuel,
That is, the fuel injection timing is calculated (S4). (5) Further, the fuel is injected based on the information obtained by the signal processing performed in S2 and so that the fuel injection amount determined in S3 can be injected at the fuel injection timing determined in S4. The pressure, that is, the fuel injection pressure is calculated (S
5). The control of the fuel injection pressure is performed by obtaining the target injection pressure from the fuel injection amount and the engine speed. More specifically, the common rail pressure (fuel pressure) detected by the common rail pressure sensor 12 becomes the target injection pressure. As described above, the control is performed by controlling the flow control valve provided in connection with the fuel pump. After the CPU 14 is initialized in S1, each of the injectors 31 to 31 to execute fuel injection is executed.
34, S2 to S5 are sequentially executed.

Next, the main processing of the DSP 15 will be described with reference to FIG. FIG. 5 is a flowchart showing DSP main processing in the controller shown in FIG. (1) Initialize the DSP (S10). (2) Once the initialization is completed in S10, the in-cylinder pressure data of the cylinders # 1 to # 4 is processed and the compression top dead center (T
DC) (S11), and thereafter, the compression top dead center (T
DC) is repeated. The details of the detection of the compression top dead center (TDC) will be described later.

In the DSP, an AD conversion end interrupt process shown in FIG. 6 is performed. FIG. 6 shows the DSP shown in FIG.
It is a flow chart which shows the interruption processing at the time of the end of AD conversion in main processing. In this interrupt processing, each step of reading the AD conversion result of the in-cylinder pressure (that is, the pressure of the combustion chamber) and updating the crank angle is executed in synchronization with a signal of every 1 ° of the crank angle. (1) The AD conversion result ADr (i) of the in-cylinder pressure is read (S20). AD conversion result ADr (i) of each in-cylinder pressure
Is read as Pc (i) in the combustion order i (= 1 to 4). (2) Next, initialization of the crank angle is performed (S2).
1). (3) The in-cylinder pressure data is stored in the memory (S2
2). (4) A signal for cylinder determination, that is, a REF signal is output (S23). (5) Signal before top dead center, that is, BTDC (Before
(Top Dead Center) signal is output (S
24). (6) The crank angle is updated. (S25). Details of S21 to S25 will be described below.

Referring to the flowchart shown in FIG.
1 will be described. FIG. 7 is a flowchart showing a process of initializing the crank angle in the interrupt process at the end of the AD conversion shown in FIG. (1) When the engine is started, it is determined whether or not the initialization of the crank angle has already been completed (S30). If the crank angle initialization is completed,
The process immediately returns to the AD conversion end interrupt routine. (2) If the initialization of the crank angle has not been completed, the crank angle θ is set to 0 at the start of the operation of the controller 7 (S31). (3) At the end of setting the crank angle θ in S31,
The initialization of the crank angle is completed (S32).

Next, the process of storing the in-cylinder pressure data in the memory in S22 will be described with reference to the flowchart shown in FIG. FIG. 8 is a flowchart showing a process of storing the in-cylinder pressure data in the memory in the interrupt process at the end of the AD conversion shown in FIG. (1) It is determined whether the storage of the in-cylinder pressure data has been completed (S40). If the storage of the in-cylinder pressure data has been completed, the process returns to the interrupt processing at the end of AD conversion (FIG. 6) without executing this routine. (2) If the storage of the in-cylinder pressure data is not completed, it is determined whether or not the storage of the in-cylinder pressure data is started (S4).
1). The shift to S41 is performed only in the first two-and-a-half rotations during the engine starting cranking. However, since the in-cylinder pressure during the first half revolution during the engine start cranking is not used for detecting the compression top dead center, the interruption processing at the end of the AD conversion without starting the in-cylinder pressure data storage (see FIG. Return to 6). The start and end of the storage of the in-cylinder pressure data will be described in detail in a crank angle update process S25. (3) During the starting cranking to start storing the in-cylinder pressure data, the current crank angle θ of each of the cylinders # 1 to # 4
Pressures Pc (1) to Pc (4) for four cylinders at
Are stored as Pc (θ, 1) to Pc (θ, 4), respectively (S42). (4) It is determined whether or not the crank angle θ is 719 (S43). If the crank angle θ is not 719, the operation of the four cycles in each of the cylinders # 1 to # 4 has not yet been completed, so the crank angle θ is updated by 1 ° to continue storing the in-cylinder pressure data. Is performed again. (5) If the crank angle θ is 719, each cylinder # 1
Since each cycle in # 4 has completed one cycle, the storage of the in-cylinder pressure data ends (S44).

Next, the output processing of the cylinder discrimination signal (REF signal) in S23 will be described with reference to the flowchart shown in FIG. FIG. 9 is a flowchart showing the output processing of the REF signal in the interrupt processing at the end of the AD conversion shown in FIG. (1) It is determined whether or not the top dead center (TDC) detection (details will be described later) has been completed (S50). If the TDC detection has not been completed, this routine is not executed and
The process returns to the interrupt processing at the end of AD conversion (FIG. 6). (2) If the detection of TDC has been completed, it is determined whether or not the crank angle θ at the time of executing this routine is the crank angle at the time of TDC detection for cylinder # 1, that is, θt (1). A determination is made (S51). The crank angle θ is θt
If not (1), return to the interrupt processing at the end of AD conversion (FIG. 6). (3) If the crank angle θ is θt (1), the DSP 1
5 outputs a one-pulse REF signal to the CPU 14 with two rotations of the crankshaft (S52). When the REF signal is output, the predetermined cylinder has reached the compression top dead center, so that the fuel injection control for the other cylinders is determined based on the combustion order from the reference cylinder.

Next, the output processing of the signal before the top dead center (BTDC) in S24 will be described with reference to the flowchart shown in FIG. FIG. 10 is a flowchart showing the output processing of the BTDC signal in the interrupt processing at the end of the AD conversion shown in FIG. (1) It is determined whether or not the top dead center (TDC) detection has been completed (S60). If the TDC detection has not been completed, the process returns to the interrupt processing at the end of AD conversion (FIG. 6) without executing this routine. (2) If the detection of the TDC has been completed, the crank angle θ (count value) becomes equal to the TDC of the cylinder # 1.
It is determined whether or not it is 60 before the crank angle θt (1) corresponding to (S61). (3) If the crank angle is not 60 before θt (1) in S61, it is determined whether or not the crank angle is 60 before crank angle θt (2) corresponding to TDC for cylinder # 2 ( S62). (4) Similarly, the crank angle is the crank angle θ corresponding to the TDC for cylinder # 3 or cylinder # 4, respectively.
It is determined whether or not it is 60 before t (3) or θt (4) (S63) (S64). (5) If the judgment is positive in any of S61 to S64,
The DSP 15 outputs a BTDC signal for each cylinder to the CPU 14 at each determination (S65). BTDC
The signal is output for a total of four pulses in two rotations of the crankshaft.

Next, the process of updating the crank angle in S25 will be described with reference to the flowchart shown in FIG. FIG. 11 is a flowchart showing a crank angle update process in the interrupt process at the end of the AD conversion shown in FIG. (1) The crank angle θ is updated by a unit amount (one count) (S70). (2) It is determined whether the rotation of the engine 1 is started from the stopped state and the storage of the in-cylinder pressure data is completed (S7).
1). The storage of the in-cylinder pressure data does not end until the crankshaft makes two and a half rotations after the engine is stopped. In particular, for cylinders whose engine has been stopped during the compression process due to the closing of the intake valve, pressure leakage occurs while the engine is stopped, so the maximum value of the cylinder pressure is normally detected during the first half rotation of the crankshaft. May not be possible. The in-cylinder pressure data during this period is not used for detecting the compression top dead center. Further, in order to store a necessary data amount, the crankshaft needs to rotate twice. (3) It is determined whether storage of the in-cylinder pressure data has started (S72). Since the in-cylinder pressure data is not taken during a half rotation from the stop state of the engine 1, NO is determined in S72. (4) It is determined whether or not the crank angle θ is 180 (S73). Since the crank angle θ is updated, when the angle θ gradually increases to 180, the crank angle θ is reset to 0 and the storage of the in-cylinder pressure data is started (S74). (5) When the storage of the in-cylinder pressure data is started, the process branches to YES in S72 every time the crank angle θ is updated, and it is determined whether or not the crank angle θ is less than 720 (S75). . After resetting the crank angle θ in S74, until the crankshaft makes two revolutions (720 in count value),
The storage of the in-cylinder pressure data is continued. (6) When the crankshaft rotates twice, the determination in S75 is N
O, and the crank angle θ is reset to 0 (S7
6).

Next, the process of detecting the top dead center (TDC) in S11 will be described with reference to the flowchart shown in FIG. FIG. 12 is a flowchart showing a TDC detection process in the main process of the DSP shown in FIG. (1) It is determined whether the detection of TDC has already been completed (S80). If the detection of TDC has been completed, this flow is not executed. (2) If the detection of TDC has not been completed, it is determined whether the storage of the in-cylinder pressure data has been completed (S).
81). This flow is not executed even when the storage of the in-cylinder pressure data has not been completed. (3) When the storage of the in-cylinder pressure data is completed, the crank angle θ in the calculation process is set to 0 (S82). (4) The maximum in-cylinder pressures Pm (1) to Pm (4) stored for each of the cylinders # 1 to # 4 are set to 0 and initialized (S83). (5) S84 and S85 are steps for cylinder # 1. At the crank angle θ (starting from 0 at the beginning), the in-cylinder pressure Pc of cylinder # 1 stored as data
It is determined whether (θ, 1) is greater than Pm (1) (S84). (6) If the determination in S84 is YES, the in-cylinder pressure Pc (θ, 1) is substituted for Pm (1) and replaced. Further, the crank angle θ at that time is updated as the crank angle θm (1) when the maximum in-cylinder pressure of the cylinder # 1 is detected (S
85). (7) S86 and S87 are steps for cylinder # 2. In-cylinder pressure Pc (θ, 2) of cylinder # 2 is Pm
(2) It is determined whether or not the pressure is greater than (S86), the in-cylinder pressure Pc (θ, 1) is replaced with Pm (1), and the crank angle θm is updated when the maximum in-cylinder pressure is detected (S87). Is performed in the same manner as S84 and S85. (8) For cylinders # 3 and # 4, the same processing as that for cylinders # 1 and # 2 shown in S84 to S87 is performed (S8).
8). (9) The crank angle θ is updated by a unit amount (one count) (S89). (10) It is determined whether the crank angle θ has exceeded 720 (S90). If the crank angle θ is equal to or less than 720, the flow returns to S84, and the routine for obtaining the maximum in-cylinder pressure Pm and the crank angle θm at the time of detecting the maximum pressure Pm is repeated. (11) When the crank angle θ exceeds 720, each cylinder #
Crank angle θ when detecting maximum in-cylinder pressure for 1 to # 4
m (1) to θm (4) are represented by θt (1) to θt, respectively.
(4) (S91). (12) When θt (1) to θt (4) are obtained, TDC detection ends (S92).

When the REF signal is output, a REF interrupt process as shown in FIG. 13 is performed. FIG. 13 is a flowchart showing an interrupt process when a REF signal is input to the CPU 14 in the main process shown in FIG.
In this interrupt processing, the count value CNb of the BTDC signal is used.
Is reset to zero. That is, engine 1
Is a four-cylinder engine, the count value CNb can take four integers from 0 to 3. Count value CN
When b is 0, the fuel injection and ignition in each cylinder make one cycle, and before the count value CNb becomes 4, an REF signal is output and an interrupt process is performed, and the count value CNb becomes 0.
Is set to (S100).

4 per pump shaft rotation based on S65
BTDC signals are output. BTDC signal is CPU
14, the BTDC signal interruption processing as shown in FIG. 14 is performed. FIG. 14 shows the CP shown in FIG.
It is a flowchart in the U main process which shows the interruption process when a BTDC signal is input. (1) The rotation speed of the engine 1 is calculated (S11)
0). That is, the rotation speed of the engine 1 per unit time is calculated based on the time required from the output of the previous BTDC signal to the output of the current BTDC signal. (2) It is determined whether or not the count value CNb of the BTDC signal is 0 (S111). If the count value CNb is 0, the fuel injection process (S2 to S5 and subsequent fuel injection execution) of the injector 31 provided in the cylinder (# 1) with the combustion order i = 1 is performed (S112). An outline of the timing of this injector processing is shown in the lowermost graph of FIG. (3) In the determination in S111, the count value CNb is 0
If not, the process immediately proceeds to S113, where the count value CN
It is determined whether or not b is 1 (S113). (4) If the count value CNb is 1, fuel injection processing (execution of S2 to S5 and subsequent fuel injection) of the injector 33 provided in the cylinder (# 3) of i = 2 is performed (S1).
14). (5) In the determination in S113, the count value CNb is 1
If not, the process immediately proceeds to S115, and the same determination processing as described above and the fuel injection processing of the injector when YES is determined in the determination processing are performed (S115). (6) In S112, S114 or S115, # 1
When the fuel injection processing of any one of the injectors 3 to # 4 is performed, the determination other than the determination of the corresponding count value CNb is always NO, so that the count value CNb which is increased by 1 is replaced with the new count value. Change to CNb (S116),
This interrupt processing ends. Also in the next interrupt processing, the determination for the next count value CNb is made in S11.
YES is determined in any of the similar determinations in S1, S113, and S115. When the sequentially increasing count value CNb becomes 3, the count value CNb is reset to 0 by the interruption processing of the REF signal (S100) before the count value CNb becomes 4.

[0034]

Since the compression top dead center detecting device for an engine according to the present invention is configured as described above, the following effects can be obtained. That is, the controller obtains the maximum in-cylinder pressure of each cylinder based on the output of the in-cylinder pressure sensor provided for each cylinder of the engine when the engine is not in a combustion state. The determined crank angle is determined as the compression top dead center of each cylinder. To determine the top dead center of each cylinder, a sensor that determines the crank angle at the top dead center position or a predetermined angle position before the top dead center, and a cylinder identification sensor that identifies a specific cylinder in a multi-cylinder engine are provided. There is no necessity, and as a sensor relating to the rotation of the engine, basically a unit crank angle (for example, 1 °
The compression top dead center of the engine is detected with high accuracy only by a sensor that detects each crank angle) and a sensor that detects the in-cylinder pressure used for fuel injection control. If an optical or electromagnetic sensor for discriminating top dead center or cylinder is provided, it is necessary to provide different types of through holes or teeth and two photo sensors or pickups on one rotating plate. Plates and sensors are not required.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an outline of an engine to which a compression top dead center detection device for an engine according to the present invention is applied.

FIG. 2 is a graph showing an outline of in-cylinder pressure and injector processing in each injector as the crank angle of the engine shown in FIG. 1 elapses.

FIG. 3 is a block diagram showing an outline of a controller for performing control related to combustion injection of an engine according to the present invention.

FIG. 4 is a flowchart showing main processing of a CPU in the controller shown in FIG. 3;

FIG. 5 is a flowchart showing a DSP main process in the controller shown in FIG. 3;

FIG. 6 is a flowchart showing an interrupt process at the end of AD conversion in the DSP main process shown in FIG. 5;

FIG. 7 is a flowchart showing a process of initializing a crank angle in an interrupt process at the end of AD conversion shown in FIG. 6;

FIG. 8 is a flowchart showing a process of storing in-cylinder pressure data in a memory in an interrupt process at the end of AD conversion shown in FIG. 6;

FIG. 9 is a flowchart showing the output processing of a REF signal in the interrupt processing at the end of AD conversion shown in FIG. 6;

FIG. 10 is a flowchart showing a process of outputting a BTDC signal in an interrupt process at the end of AD conversion shown in FIG. 6;

FIG. 11 is a flowchart showing a crank angle update process in the interrupt process at the end of AD conversion shown in FIG. 6;

12 is a diagram showing a TD in the main processing of the DSP shown in FIG.
It is a flowchart which shows the detection process of C.

13 is a flowchart showing an interrupt process when a REF signal is input to the CPU 14 in the main process shown in FIG.

FIG. 14 is a diagram showing B in the CPU main processing shown in FIG. 4;
It is a flowchart which shows the interruption processing when a TDC signal is input.

FIG. 15 is a diagram showing a conventional top dead center detection mechanism.

FIG. 16 is a graph showing the influence of the heat release rate in the combustion chamber on the top dead center error as viewed from the crank angle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multi-cylinder engine 3, 31-34 Injector 4, 41-44 In-cylinder pressure sensor 5 Crankshaft 7 Controller 10 Crank angle sensor θ Crank angle θm Crank angle at detection of maximum in-cylinder pressure θt Crank at compression top dead center detection Angle Pc In-cylinder pressure Pm Maximum in-cylinder pressure

Claims (6)

[Claims] 1. A crank angle sensor for detecting a crank angle of an engine, an in-cylinder pressure sensor provided in each cylinder of the engine for detecting an in-cylinder pressure of each cylinder, and an output of the in-cylinder pressure sensor. The compression top dead center detection of the engine comprising a controller for determining the maximum cylinder pressure of each cylinder in the non-combustion state of the engine and determining the crank angle at the maximum cylinder pressure as the compression top dead center of each cylinder. apparatus. 2. The cylinder angle sensor detects a crank angle for each unit crank angle, and the cylinder pressure sensor detects the cylinder pressure in synchronization with the detection of the crank angle by the crank angle sensor. 2. The compression top dead center detecting device for an engine according to claim 1, comprising: 3. The non-combustion state of the engine is a state of the engine at the start of engine starting cranking, wherein the engine is driven in four cycles, and the controller operates during a period at least two revolutions of the crankshaft of the engine. 3. The compression top dead center detection device for an engine according to claim 1, wherein a maximum value of the in-cylinder pressure detected by the in-cylinder pressure sensor is stored as a maximum in-cylinder pressure. 4. The controller according to claim 1, wherein the controller detects the in-cylinder pressure detected by the in-cylinder pressure sensor after at least a half rotation immediately after the start of rotation of the crankshaft as data for obtaining a maximum in-cylinder pressure of each of the cylinders. 4. The compression top dead center detecting device for an engine according to claim 3, wherein the compression top dead center is used. 5. The system according to claim 1, wherein the controller determines a predetermined crank angle as a reference for fuel injection into each cylinder based on the crank angle determined as the compression top dead center. Any one of items 1-4
Item 8. The compression top dead center detection device for an engine according to the above item. 6. The crank angle determined in advance is a crank angle before top dead center, which is above a predetermined angle from the compression top dead center in each cylinder, and a reference crank angle for cylinder identification. 6. The compression top dead center detecting device for an engine according to claim 5, wherein: