MALFUNCTION DETECTION DEVICE

Abstract

Misfire detection device for a four-stroke multi-cylinder engine with a pair of cylinders in which an explosion takes place successively and which has an explosion time specification property of partially overlapping periods of an expansion stroke, wherein the misfire detection device comprises the following: Devices (53, 66, 67) for detecting the angular velocity of a crank; a combustion pressure sensor (40, 140) arranged in at least one cylinder of the cylinder pair; a combustion pressure-based detection device (202) for detecting a misfire in the cylinder in which the combustion pressure sensor is located, using an output from the combustion pressure sensor; and an angular velocity-based detection device (203) for detecting a misfire in each of the remaining cylinders in which the combustion pressure sensor is not located, using the crank angular velocity.

Description

[0001] The present invention relates generally to misfire detection devices that detect engine misfires, and in particular to a misfire detection device suitable for detecting misfires in an engine with irregular explosion intervals.

[0002] A known method detects misfires in the engine of a four-wheeled vehicle based on the angular velocity of a crankshaft, measured from the time intervals at which a crank pulse occurs (the period between two adjacent crank pulses). JP H07-119532 A discloses a method that detects misfires using the crank angular velocity and a combustion pressure sensor that detects cylinder pressure. The method disclosed in JP H07-119532 A includes a combustion pressure sensor located in each cylinder. The combustion pressure sensor enables the detection of pressure fluctuations in each cylinder, thus allowing misfires to be detected. Since misfire detection is difficult due to fluctuations in combustion pressure at low engine speeds, the method uses the crank angular velocity at low speeds to detect misfires.

[0003] Recently, studies on the potential adoption of misfire detection technology in motorcycles have been underway, focusing on improved maintainability and environmental protection. Many motorcycles currently feature engines with irregular firing intervals, designed to meet diverse performance and characteristic demands and, particularly in sport motorcycles, to deliver the expected traction.

[0004] The method disclosed in JP H07-119532A, while the detection accuracy can be improved by using crankshaft angular velocity and combustion pressure within suitable time parameters and a strong field of these for misfire detection, requires the cylinder pressure sensors to be installed in all cylinders. Therefore, the increased number of sensors required when using the method in a multi-cylinder engine unfortunately leads to an increase in labor hours and costs.

[0005] DE 10 2005 026 724 A2 and DE 10 2009 035 700 B3 also show misfire detection units with cylinder pressure sensors in all cylinders.

[0006] One object of the present invention is to provide a misfire detection device that can reliably detect a misfire in an engine with irregular explosion intervals, while minimizing the use of costly combustion pressure sensors.

[0007] To solve the aforementioned problem, the present invention comprises the following features in a misfire detection device for a four-stroke multi-cylinder engine with a pair of cylinders in which an explosion takes place successively and which has an explosion time specification feature of partially overlapping expansion stroke times. (1) The present invention has a first feature in that it comprises devices (53, 66, 67) for detecting an angular velocity of a crank, a combustion pressure sensor (40, 140) arranged in at least one cylinder of the cylinder pair, a combustion pressure-based detection device (202) for detecting a misfire in the cylinder in which the combustion pressure sensor is arranged using an output from the combustion pressure sensor, and an angular velocity-based detection device (203) for detecting a misfire in each of the other cylinders in which the combustion pressure sensor is not arranged using the crank angular velocity. (2) The present invention has a second feature in that the engine consists of an engine with irregular explosion intervals having a pair of cylinders in which the explosion intervals are less than 180 degrees. (3) The present invention has a third feature in that the engine is an irregular explosion interval engine with a pair of cylinders in which the explosion intervals are 90 degrees. (4) The present invention has a fourth feature in that the combustion pressure-based detection device (202) comprises a device (202a) for detecting a crank angle, a device (202b) for detecting combustion pressure in a cylinder using an output from the combustion pressure sensor, a device (202c) for calculating the IMEP (reported mean effective pressure) using a PV (pressure-volume) diagram which represents a relationship between a displacement volume value based on the crank angle and an output from the combustion pressure sensor, and a misfire detection device (202d) for detecting a misfire condition using the IMEP. (5) The present invention has a fifth feature in that the misfire detection device (202d) compares the IMEP obtained in a current cycle with a misfire detection threshold IMEP_ref, and when it detects that IMEP < IMEP_ref, the misfire detection device (202d) detects a misfire condition. (6) The present invention has a sixth feature in that the misfire detection device (202d) compares the IMEP_n-1 calculated in a previous cycle with the IMEP_n calculated in a current cycle, and when it detects that IMEP_n is less than IMEP_n-1, the misfire detection device (202d) detects a misfire condition. (7) The present invention has a seventh feature in that the combustion pressure sensor (40, 140) is arranged in a cylinder head between adjacent cylinders and a pressure-sensitive section (40b, 140b) of the combustion pressure sensor (40, 140) is exposed to a connection path which is connected to a combustion chamber.

[0008] According to the present invention, the following effects are achieved. (1) According to the first feature of the present invention, in a misfire detection device for a four-stroke multi-cylinder engine with a cylinder pair in which the explosion takes place sequentially and which has an explosion time specification characteristic of partially superimposed expansion stroke times, the misfire detection device comprises means (53, 66, 67) for detecting an angular velocity of a crank, a combustion pressure sensor (40, 140) arranged in at least one cylinder of the cylinder pair, and a combustion pressure-based detection device (202) for detecting a misfire in the cylinder in which the combustion pressure sensor is arranged, using an output from the combustion pressure sensor.and an angular velocity-based detection device (203) for detecting a misfire in each of the other cylinders in which the combustion pressure sensor is not located, using the crankshaft angular velocity.

[0009] Therefore, misfire detection is performed using an angular velocity-based approach without installing a combustion pressure sensor for a cylinder where the expansion stroke periods do not overlap, thus enabling angular velocity-based misfire detection. Conversely, misfire detection is performed using a combustion pressure sensor only for a cylinder where the expansion stroke periods overlap, making angular velocity-based misfire detection difficult. This arrangement reduces the number of combustion pressure sensors required compared to the prior art, where all cylinders are equipped with combustion pressure sensors. Thus, highly accurate misfire detection can be achieved with a simple design and at low cost.

[0010] (2) According to the second feature of the present invention, the engine is an irregular explosion interval engine with a pair of cylinders in which the explosion intervals are less than 180 degrees. Thus, a misfire in the irregular explosion interval engine, in which expansion stroke times are likely to partially overlap, can be reliably detected.

[0011] (3) According to the third feature of the present invention, the engine is an irregular explosion interval engine with a pair of cylinders in which the explosion intervals are 90 degrees. Thus, a misfire in the irregular explosion interval engine, in which the explosion time parameters are set to achieve high traction performance, can be reliably detected.

[0012] (4) According to the fourth feature of the present invention, the combustion pressure-based sensing device (202) comprises a device (202a) for sensing a crank angle, a device (202b) for sensing combustion pressure in a cylinder using an output from the combustion pressure sensor, a device (202c) for calculating the IMEP (reported mean effective pressure) using a PV (pressure-volume) diagram that represents a relationship between a displacement volume value based on the crank angle and an output from the combustion pressure sensor, and a misfire detection device (202d) for detecting a misfire condition using the IMEP. Thus, a quantitative determination of engine combustion conditions can be carried out such that adequate misfire detection can be performed.

[0013] (5) According to the fifth feature of the present invention, the misfire detection device (202d) compares the IMEP obtained in a current cycle with a misfire detection threshold IMEP_ref, and if it detects that IMEP < IMEP_ref, the misfire detection device (202d) detects a misfire condition. Thus, conditions for detecting a misfire can be optimized for different engine specifications in such a way that misfire detection can be achieved with high accuracy.

[0014] (6) According to the sixth feature of the present invention, the misfire detection device (202d) compares the IMEP_n-1 calculated in a previous cycle with the IMEP_n calculated in a current cycle, and upon detection that IMEP_n is less than IMEP_n-1, the misfire detection device (202d) detects a misfire condition. Thus, misfire detection can be performed using an identical algorithm, independent of the specified diagram and the specified mean effective pressure (IMEP), which may vary depending on the engine specifications.

[0015] (7) According to the seventh feature of the present invention, the combustion pressure sensor (40, 140) is arranged in a cylinder head between adjacent cylinders, and a pressure-sensitive section (40b, 140b) of the combustion pressure sensor (40, 140) is exposed to a connecting path that is in contact with a combustion chamber. Thus, even if misfire detection is only to take place in one of adjacent cylinders at a time, the sensor can be mounted at a location that is uniform for different engine types, and the shape of a connecting path can vary between different engine types. Fig. Figure 1 shows a cross-sectional view of a motor 10 to which the present invention is applied. Fig. Figure 2 shows a cross-sectional view of the motor 10 from the rear. Fig. Figure 3 shows a diagram illustrating how a pulse generator ring 53 is arranged. Fig. Figure 4 shows an enlarged cross-sectional view of parts around the combustion chamber 31. Fig. Figure 5 shows a perspective view of the cylinder head 18 in cross-sectional view. Fig. 4 shown. Fig. Figure 6 shows an enlarged cross-sectional view of parts around the combustion pressure sensor 40, as in Fig. 4 shown. Fig. Figure 7 shows a cross-sectional view of a motor 110 in a left-hand view. Fig. Figure 8 shows a cross-sectional view of the engine 110 from the rear. Fig. Figure 9 shows a top view of the cylinder block section 117 in a view from the side of the cylinder head 118. Fig. Figure 10 shows a cross-sectional view along line XX in Fig. 9. Fig. Figure 11 shows an enlarged cross-sectional view of parts around the combustion pressure sensor 140, as in Fig. 10 shown. Fig. Figure 12(a) shows a graph illustrating a relationship between a crank angle (abscissa) and an angular velocity (ordinate) in a four-cylinder V-engine with irregular explosion intervals. Fig. Figure 12(b) shows a graph illustrating a relationship between order and slope, derived from the in Fig. The frequency analysis is obtained from the waveforms shown in 12(a). Fig. Figure 13 shows a functional block diagram illustrating an embodiment of the main components of a misfire detection device according to an embodiment of the present invention. Fig. Figure 14 shows exemplary diagrams illustrating the relationship between displacement volume and cylinder pressure when combustion occurs normally ( Fig. 14(a)) and if a misfire occurs ( Fig. 14(b)).

[0016] A particular embodiment to which the present invention is applied is described below with reference to the accompanying drawings. The basic concept of the present invention is first described below with reference to Fig. 12. The embodiment is then explained in detail.

[0017] Fig. Figure 12(a) shows a graph illustrating a relationship between a crank angle (abscissa) and an angular velocity (ordinate) in a four-cylinder V-engine with irregular combustion intervals. The following description is based on the irregular combustion interval engine with the following details: a firing order in this example consists of cylinder No. 1 (#1) → cylinder No. 3 (#3) → cylinder No. 2 (#2) → cylinder No. 4 (#4) → cylinder No. 1 (#1); and the intervals of combustion strokes between #1 and #3 are 180 degrees, the intervals of combustion strokes between #3 and #2 are 270 degrees, the intervals of combustion strokes between #2 and #4 are 180 degrees, and the intervals of combustion strokes between #4 and #1 are 90 degrees.

[0018] Fig. Figure 12(a) shows the relationship between the crank angle and the angular velocity when the explosion occurs normally in all cylinders (♦), a misfire occurs only in cylinder No. 3 (■), and a misfire occurs only in cylinder No. 4 (▲). Fig. 12(b) is a graph illustrating a relationship between order and slope, derived from the in Fig. The frequency analysis is obtained from the waveforms shown in 12(a).

[0019] Reference is made to Fig. 12(a). If cylinder No. 3 (#3) misfires, the crankshaft angular velocity gradually decreases over a prolonged period due to the longer associated time until a time interval at which the next explosion occurs in cylinder No. 4. In contrast, if cylinder No. 4 (#4) misfires, the time interval before the next explosion occurs in cylinder No. 1 (#1) is so short that some expansion cycles between cylinder No. 4 (#4) and cylinder No. 1 (#1) overlap. Thus, even if cylinder No. 4 (#4) misfires, the crankshaft angular velocity begins to increase within a short period when the next explosion occurs normally in cylinder No. 1 (#1). Consequently, a change in crankshaft angular velocity limited to misfires is difficult to detect.

[0020] It will be on Fig. 12(b) is referenced. If frequency components of changes in crankshaft angular velocity are represented by order components, the crankshaft angular velocity gradually decreases over an extended period, and a low-frequency component of the waveform increases when cylinder No. 3 (#3) misfires, thus increasing a low-order component. When cylinder No. 4 (#4) misfires, the low-frequency component of the change in crankshaft angular velocity decreases more than when cylinder No. 3 (#3) misfires, thus decreasing the low-order component.

[0021] The inventor has discovered that in a cylinder pair of an engine with irregular explosion intervals, where the intervals of explosion strokes are short and the times of expansion strokes partially overlap, a misfire in cylinder (#1), which is still required to reach a specific time at which an explosion occurs, is difficult to detect using a change in the crankshaft angular velocity. To solve this problem, the present invention provides misfire detection configurations that differ between the specific cylinder of interest here and other cylinders.

[0022] Fig. Figure 1 shows a cross-sectional view of an engine with irregular explosion intervals viewed from the left side, to which an embodiment of the present invention is applied. Fig. Figure 2 shows a cross-sectional view of the motor 10 from the rear.

[0023] Engine 10 is mounted on a vehicle with a seat, such as a motorcycle. Engine 10 is a four-cylinder, four-stroke V-engine, with two cylinders arranged in a line on one front side of the body and two cylinders arranged in a line at right angles to them on one rear side of the body.

[0024] The engine 10 is positioned between the front and rear wheels of the motorcycle and supported on a body frame. The engine 10 comprises a crankcase 12 and cylinder sections 13. The crankcase 12 houses a crankshaft 11, which extends across the width of the vehicle. The cylinder sections 13 are connected to the crankcase 12. Each cylinder section 13 extends individually from an upper section of the crankcase 12, one towards the front of the motorcycle and the other towards the rear. The cylinder sections 13 thus essentially form a V-shape. A transmission TM is housed in a rear section of the crankcase 12. The transmission TM transmits power from the engine 10 to the rear wheel at a reduced speed.

[0025] An oil pan 15 is mounted on a lower section of the crankcase 12. The cylinder sections 13 each have a cylinder block section 17, a cylinder head 18, and a cylinder head cover 19. The cylinder block section 17 accommodates a piston 16. The cylinder head 18 is connected to an upper surface of the cylinder block section 17. The cylinder head cover 19 is mounted on an upper surface of the cylinder head 18.

[0026] A valve chamber 20 is defined between the cylinder head 18 and the cylinder head cover 19. The valve chamber 20 accommodates an intake camshaft 21 and an exhaust camshaft 22. The intake camshaft 21 and the exhaust camshaft 22 are arranged so that they run parallel to the crankshaft 11. The intake camshaft 21 and the exhaust camshaft 22 are supported by an upper surface section of the cylinder head 18 and rotate by means of a operative connection with the crankshaft 11.

[0027] Intake systems 23 are mounted between the front and rear cylinders. Exhaust ports 33 are formed on the front side of the cylinder heads 18 of the front cylinders and on the rear side of the cylinder heads 18 of the rear cylinders. The exhaust ports 33 connect to exhaust pipes. The piston 16 is connected to the crankshaft 11 via a connecting rod 26. The piston 16 is connected to a distal end section of the connecting rod 26 via a piston pin, which is arranged to run parallel to the crankshaft 11.

[0028] The crankshaft 11 is rotatably supported by several support walls 27a. The support walls 27a are arranged in a crank chamber 27 of the crankcase 12. The piston 16 is received in a cylindrical cylinder bore 28. The cylinder bore 28 is defined in the cylinder block section 17. A valve actuation unit 29 and a spark plug 30 are arranged in the cylinder head 18.

[0029] The cylinder head 18 has a combustion chamber 18a, which corresponds to an upper surface 16a (see Fig. 4) opposite the piston 16. The combustion bowl 18a forms a lower surface of the cylinder head 18, which is recessed towards the side of the cylinder head cover 19. The combustion bowl 18a closes an upper surface opening in the cylinder bore 28. A combustion chamber 31 is formed between the upper surface 16a and the combustion bowl 18a.

[0030] The cylinder head 18 has intake ports 32 and exhaust ports 33. The intake ports 32 each provide a connection between the intake system 23 and the combustion chamber 31 via an opening 33a located at a lower end of the cylinder head 18 (see Fig. 4) The exhaust ports 33 each provide a connection between the combustion chamber 31 and an exhaust pipe 24 via the opening 33a located at the lower end of the cylinder head 18. A fuel injection unit 34 injects fuel into the intake port 32.

[0031] The valve actuation unit 29 comprises the intake camshaft 21, the exhaust camshaft 22, an intake valve 35, an exhaust valve 36, and valve springs. The intake valve 35 opens and closes the opening 33a in the intake port 32. The exhaust valve 36 opens and closes the opening 33a in the exhaust port 33. The valve springs force the intake valve 35 and the exhaust valve 36 individually into a valve closing direction. The intake valve 35 and the exhaust valve 36 are provided in pairs for each cylinder and are arranged side by side in the axial direction of the crankshaft 11.

[0032] The intake valve 35 is driven by an intake cam 21a of the intake camshaft 21, which presses on the intake valve 35 to open the opening 33a in the intake port 32 within a predetermined time interval. The exhaust valve 36 is driven by an exhaust cam 22 of the exhaust camshaft 22, which presses on the exhaust valve 36 to open the opening 33a in the exhaust port 33 within a predetermined time interval.

[0033] The crankshaft 11 is provided with a drive pinion 37. The drive pinion 37 is arranged on a shaft end section of the crankshaft 11 and projects outwards from the crankcase chamber 27. A driving force from the crankshaft 11 is transmitted to the valve actuation unit 29 by a drive force transmission element 38. The drive force transmission element 38 connects the drive pinion 37 to the intake camshaft 21 and the exhaust camshaft 22. The engine 10 has a drive force transmission element receiving chamber 39. The drive force transmission element receiving chamber 39 is arranged outside the right cylinder. The drive force transmission element 38 is received in the drive force transmission element receiving chamber 39. The drive force transmission element 38 is, for example, a chain.

[0034] The piston 16 moves back and forth within the cylinder bore 28 when a mixture supplied from the intake port 32 into the combustion chamber 31 is ignited and burned by the spark plug 30. The engine 10 is a four-stroke engine in which an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke occur with each 180-degree rotation of the crankshaft 11. During the intake stroke, the piston 16 moves downwards to draw in air. During the compression stroke, the piston 16 moves upwards to top dead center to compress the mixture. During the combustion stroke, combustion gases ignited by the spark plug 30 expand, causing the piston 16 to move downwards to bottom dead center. During the exhaust stroke, the piston 16 moves upwards to expel the exhaust gases.

[0035] The rotational drive force of the crankshaft 11 is transmitted to a main shaft MS via a clutch CL and slowed down by the gearbox TM. The gearbox TM has several gear pairs arranged between the main shaft MS and an auxiliary shaft CS. The reduced rotational drive force is then discharged from an end section of the auxiliary shaft CS. A generator G is arranged at an end section of the crankshaft 11.

[0036] In engine 10, the timing of ignition by spark plug 30 varies from one cylinder to another. Engine 10 has a combustion pressure sensor 40. The combustion pressure sensor 40 detects the pressure within cylinder section 13.

[0037] Fig. Figure 3 shows a diagram illustrating the arrangement of a pulse generator ring 53. The pulse generator ring 53 is formed in an annular plate shape, which is coaxially connected to the crankshaft 11 via an axis of rotation and rotates integrally with the crankshaft 11. The pulse generator ring 53 has a plurality of pulse generator wheels 66. The pulse generator wheels 66 are arranged annularly and at equal intervals around the axis of rotation. The pulse generator wheels 66 are made, for example, of a magnetic material and are arranged at intervals with a predetermined central angle.

[0038] The motor 10 has a pulse generator sensor 67. The pulse generator sensor 67 is located opposite an annular path of the pulse generator ring 53 and generates a pulse signal to correspond to a movement of the pulse generator ring 53. The pulse generator sensor 67 has a main unit 69 and a mounting piece 72. The main unit 69 is located opposite an interior of the crankcase 12. The mounting piece 72 is connected to the main unit 69 and attached to the crankcase 12. A through-hole 68 has an axis aligned with the axis of a second drive shaft 44. The pulse generator sensor 67 outputs an electrical signal depending on the presence of a magnetic material detected on a movement path of the pulse generator ring 53. The pulse generator sensor 67 outputs a pulse signal that detects an angular position of the crankshaft 11.

[0039] The mounting piece 72 is positioned above an upper surface of a base 73. The base 73 projects from the upper surface of the crankcase 12. The mounting piece 72 is then attached to the base 73 using a bolt 74. The pulse generator sensor 67 has a sensing axis 75. The sensing axis 75, which has the highest sensitivity, is aligned with an axis of rotation of the crankshaft 11. The sensing axis 75 is orthogonal to the axis of rotation.

[0040] In a view of an extension of the crankshaft 11, the pulse generator sensor 67 is located outside the circulating path of the cam chain 38 and on a front side of the vehicle structure. The pulse generator sensor 67 is located below the circulating path of the cam chain 38 and above the upper-lower butt surfaces 76 of the crankcase 12.

[0041] Fig. Figure 4 shows an enlarged cross-sectional view of parts around the combustion chamber 31. Fig. Figure 5 shows a perspective view of the cross-sectional view. Fig. Figure 4 shows the cylinder head 18 as viewed from the side of the cylinder block section 17. The combustion pressure sensor 40 comprises a main unit 40a, a pressure-sensitive section 40b, and a line section 40c. The main unit 40a is cylindrical. The pressure-sensitive section 40b is located at a distal end section of the main unit 40a. The line section 40c extends from a proximal end section of the main unit 40a. The pressure-sensitive section 40b has a smaller diameter than the diameter of the main unit 40a. The combustion pressure sensor 40 is, for example, a piezoelectric sensor. The pressure detected by the pressure-sensitive section 40b is converted into a corresponding electrical signal by a circuit in the main unit 40a and output to the engine 10 or a vehicle control unit via the line section 40c.

[0042] The cylinder head 18 has a lower surface that forms a connecting surface 18b. The connecting surface 18b adjoins and is connected to an upper surface 17a of the cylinder block section 17. The cylinder head 18 is connected to the cylinder block section 17 by means of a plurality of bolts, which are arranged around the cylinder bore 28 in a direction parallel to a cylinder axis 13a. The spark plug 30 is mounted in a spark plug holder 18c in the combustion chamber 18a in the cylinder head 18. The spark plug holder 18c is located on the cylinder axis 13a. The cylinder head 18 has an upper surface that forms a head cover connecting surface 18d, to which the cylinder head cover 19 is connected.

[0043] The cylinder head 18 has a wall section 18e. The wall section 18e is arranged between a combustion chamber 31L and a combustion chamber 31R, thereby separating the combustion chamber 31L from the combustion chamber 31R. A connecting path 50 forms an opening section defined by a groove 51 and the upper surface 17a of the cylinder block section 17. The groove 51 is formed in the connecting surface 18b in the wall section 18e of the cylinder head 18. The groove 51 is straight, so that it is open to the combustion chamber 31L. The groove 51 is formed, for example, integrally with the cylinder head 18 during the casting of the cylinder head 18 or by machining after casting. In this embodiment, since the groove 51 is formed in an end face of the cylinder head 18 and is thus open to the outside, it can be easily formed by casting or machining.

[0044] Fig. Figure 6 shows an enlarged cross-sectional view of parts around the in Fig. The combustion pressure sensor 40 shown in Figure 4 is located around the cylinder head 18. The wall section 18e of the cylinder head 18 forms a sensor support hole 45 within it. The sensor support hole 45 is connected to the connection path 50. The sensor support hole 45 extends from the side of the cylinder head cover 19 to a bottom surface 51a of the groove 51. Specifically, a cooling water jacket 18f is formed in the cylinder head 18 between the wall section 18e and the head cover connection surface 18d. Coolant from the engine 10 flows through the cooling water jacket 18f. The sensor support hole 45 provides a connection between the cooling water jacket 18f and the connection path 50.

[0045] The sensor support hole 45 extends parallel to the spark plug support hole 18c and the cylinder axis 13a. This arrangement allows the spark plug support hole 18c and the sensor support hole 45 to be machined from the same direction when both are to be machined. The sensor support hole 45 can therefore be machined easily.

[0046] The combustion pressure sensor 40 is inserted into the sensor support hole 45 from the side of the cooling water jacket 18f, thereby securing it in the sensor support hole 45. The pressure-sensitive section 40b of the combustion pressure sensor 40 is exposed to the connection path 50. The combustion pressure sensor 40 is located at an intermediate point between the combustion chamber 31L and the combustion chamber 31R in the connection path 50.

[0047] The combustion pressure sensor 40 is mounted in the sensor support hole 45 to hermetically seal the connection path 50. The combustion pressure sensor 40 is shown in this example mounted in the sensor support hole 45 using a threaded section formed on the outer circumference of the combustion pressure sensor 40. This mounting method is for illustrative purposes only and is not limiting. Furthermore, the cylinder head 18 has a sensor through-hole 18g. The sensor through-hole 18g allows the combustion pressure sensor 40 to be inserted into the sensor support hole 45 from the side of the cylinder head cover connection surface 18d. The sensor through-hole 18g is formed in a wall that defines the cooling water jacket 18f. The sensor through-hole 18g is closed by a plug after the combustion pressure sensor 40 has been mounted in the sensor support hole 45.

[0048] The connecting path 50 has a projection 52. The projection 52 extends from a side surface 51b of the groove 51 into the connecting path 50. The projection 52 is positioned such that it does not obstruct the connecting path 50. The projection 52 has a flat upper surface against which the pressure-sensitive section 40b at the distal end of the combustion pressure sensor 40 rests, ensuring correct positioning. Based on the foregoing, the combustion pressure sensor 40, located in the connecting path 50, can detect pressure in the combustion chamber 31L.

[0049] Fig. Figure 7 is a cross-sectional view of an engine 110 when viewed from the left side. Fig. Figure 8 is a cross-sectional view of the engine 110 as seen from the rear. The engine 10 is mounted on a semi-trailer vehicle such as a motorcycle. The engine 110 is a four-stroke engine with four cylinders arranged in a line across the width of the vehicle. The engine 110 is located between the front and rear wheels of the motorcycle and is supported by the vehicle's frame. The engine 110 has a crankcase 112 and a cylinder section 113. The crankcase 112 accommodates a crankshaft 111. The crankshaft 111 extends across the width of the vehicle. The cylinder section 113 is connected to the crankcase 112. The cylinder section 113 extends upwards towards the front of the motorcycle from an upper section of a front section of the crankcase 112. The cylinder section 113 has a cylinder axis 113a. The cylinder axis 113a is inclined forwards with respect to a perpendicular direction.

[0050] A gearbox is housed in a rear section of the crankcase 112. The gearbox transmits a drive force from the engine 110 to the rear wheel at a reduced speed. An oil pan 115 is attached to a lower section of the crankcase 112.

[0051] The crankcase 112 is vertically divided into an upper case 112a and a lower case 112b. The upper case 112a and the lower case 112b are connected to each other to form the crankcase 112. The oil pan 115 is attached to a lower surface of the lower case 112b. The cylinder section 113 comprises a cylinder block section 117, a cylinder head 118, and a cylinder head cover 119. The cylinder block section 117 accommodates a piston 116. The cylinder head 118 is connected to an upper surface of the cylinder block section 117. The cylinder head cover 119 is attached to an upper surface of the cylinder head 118. The cylinder head section 117 is integrally formed with an upper section of the upper case 112a of the crankcase 112.

[0052] A valve chamber 120 is defined between the cylinder head 118 and the cylinder head cover 119. The valve chamber 120 accommodates an intake camshaft 121 and an exhaust camshaft 122. The intake camshaft 121 and the exhaust camshaft 122 are arranged so that they run parallel to the crankshaft 111. The intake camshaft 121 and the exhaust camshaft 122 are supported by an upper surface section of the cylinder head 118 and rotate by means of a operative connection with the crankshaft 111.

[0053] Cylinder section 113 comprises four cylinders 125. The cylinders 125 are arranged along an axis 111a of the crankshaft 111. Each cylinder 125 has a piston 116. The cylinders 125 are identical in design. In each cylinder 125, an intake system 123 is attached to a rear surface section of the cylinder head 118, and an exhaust pipe 124 is attached to a front surface section of the cylinder head 118.

[0054] The piston 116 is connected to the crankshaft 111 via a connecting rod 126. The piston 116 is connected to a distal end section of the connecting rod 126 via a piston pin 126a. The piston pin 126a is arranged such that it runs parallel to the crankshaft 111. The crankshaft 111 is rotatably supported by several support walls 127a. The support walls 127a are arranged in a crank chamber 127 of the crankcase 112.

[0055] The cylinders 125 each have a cylinder bore 128, a valve actuation unit 129, and a spark plug 130. The cylinder bore 128 is formed in the cylinder block section 117 and accommodates the piston 116. The valve actuation unit 129 is located in the cylinder head 118. The spark plug 130 is attached to the cylinder head 118. The cylinder bore 128 is cylindrical. The cylinder bore 128 has an axis that represents the cylinder axis 113a of the cylinder section 113. The connecting rods 126 are connected to the crankshaft 111 at intervals of 90 degrees to each other in the circumferential direction of the crankshaft 111. This arrangement allows an explosion to occur in one cylinder at irregular intervals relative to one of the other cylinders.

[0056] The cylinder head 118 has an intake port 132 and an exhaust port 133. The intake port 132 connects the intake system 123 to a combustion chamber 131 via an opening 132a located at the lower end of the cylinder head 118. The exhaust port 133 connects the combustion chamber 131 to the exhaust pipe 124 via an opening 133a located at the lower end of the cylinder head 118. A fuel injection unit 134 injects fuel into the intake port 132.

[0057] The valve actuation unit 129 comprises the intake camshaft 121, the exhaust camshaft 122, an intake valve 135, an exhaust valve 136, a valve spring 135a, and a valve spring 136a. The intake valve 135 opens and closes the opening 132a in the intake port 132. The exhaust valve 136 opens and closes the opening 133a in the exhaust port 133. The valve spring 135a forces the intake valve 135 into a valve closing direction. The valve spring 136a forces the exhaust valve 136 into a valve closing direction.

[0058] The intake valve 135 is provided in pairs for each of the cylinders 125. The intake valves 135 are arranged side by side in the axial direction of the crankshaft 111. The exhaust valve 136 is provided in pairs for each of the cylinders 125. The exhaust valves 136 are arranged side by side in the axial direction of the crankshaft 111. In particular, four valves 135 and 136 are arranged in each of the cylinders 125.

[0059] The intake valve 135 is driven by an intake cam 121a of the intake camshaft 121, which presses on the intake valve 135 to open the opening 132a within a specific time. The exhaust valve 136 is driven by an exhaust cam 122a of the exhaust camshaft 122, which presses on the exhaust valve 136 to open the opening 133a within a specific time.

[0060] The crankshaft 111 is equipped with a drive pinion 137. The drive pinion 137 is located at a shaft end section of the crankshaft 111 and projects outwards from the crankcase. A driving force from the crankshaft 111 is transmitted to the valve actuation unit 129 by a drive force transmission element 138. The drive force transmission element 138 connects the drive pinion 137 to the intake camshaft 121 and the exhaust camshaft 122. The engine 110 has a drive force transmission element receiving chamber 139. The drive force transmission element receiving chamber 139 is located at a point adjacent laterally to the outermost cylinder of the cylinders 125. The drive force transmission element 138 is received in the drive force transmission element receiving chamber 139. The drive force transmission element 138 is, for example, a chain.

[0061] The piston 116 performs a reciprocating motion in the cylinder bore 128 when a mixture supplied from the intake port 132 into the combustion chamber 131 is ignited and burned by the spark plug 130. The engine 110 has a combustion pressure sensor 140. The combustion pressure sensor 140 detects a pressure within the cylinder section 113.

[0062] Fig. Figure 9 is a top view of the cylinder block section 117 when viewed from the side of the cylinder head 118. Fig. Figure 10 is a cross-sectional view along line XX in Fig. 9. The combustion pressure sensor 140 comprises a main unit 140a, a pressure-sensitive section 140b, and a line section 140c. The main unit 140a is cylindrical. The pressure-sensitive section 140b is located at a distal end section of the main unit 140a. The line section 140c extends from a proximal end section of the main unit 140a. The pressure-sensitive section 140b has a smaller diameter than the diameter of the main unit 140a. The combustion pressure sensor 140 is, for example, a piezoelectric sensor. Pressure detected by the pressure-sensitive section 140b is converted by a circuit in the main unit 140a into a corresponding electrical signal and output to the engine 110 or a vehicle control unit via the line section 140c.

[0063] The cylinder block section 117 comprises the cylinder bores 128, an outer wall section 142, and cooling water jackets 143. The cylinder bores 128 are arranged along the axis 111a of the crankshaft 111. The outer wall section 142 surrounds the cylinder bores 128. The cooling water jackets 143 are located between the cylinder bores 128 and the outer wall section 142. The outer wall section 142 of the cylinder block section 117 has several mounting holes 117a formed in an upper surface section thereof. The mounting holes 117a accommodate bolts that connect the cylinder head 118 to the cylinder block section 117.

[0064] The mounting holes 117a are designed at positions in front of and behind the cylinder bores 128 such that they are arranged along the axis 111a of the crankshaft 111. Specifically, the mounting holes 117a are located on the front and rear sides of outer lateral surface sections of the two cylinder bores 128, which are attached to the outside of the cylinder bores 128 arrangement, as well as on the front and rear sides of connections between the adjacent cylinder bores 128. The cylinder bores 128 are arranged in the direction in which the axis 111a of the crankshaft 111 runs. Furthermore, a longitudinal direction of the cylinder bores 128 extends perpendicular to the axis 111a in the top view. Fig. 9.

[0065] The engine coolant 110 flows through the cooling water jackets 143. The cooling water jackets 143 are arranged at the front and rear of the cylinder bores 128 and cover the cylinder bores 128 from both the front and the rear. The cooling water jackets 143 extend between the mounting holes 117a, which are adjacent to each other in the axial direction of the crankshaft 111.

[0066] The cylinder block section 117 has a bridging section 144 that connects the cylinder bore 128 to the outer wall section 142 in the radial direction of the cylinder bore 128 at an upper end section of the cooling water jackets 143. The bridging section 144 is arranged for each of the cooling water jackets 143 on the front and rear sides of the cylinder bore 128. The bridging sections 144 are arranged on a plane that bisects the cylinder bore 128 in the direction in which the cylinder bores 128 are arranged. Furthermore, the bridging sections 144 have upper surfaces that are flush with an upper surface of the cylinder block section 117. The upper surface of the cylinder block section 117 serves as a connecting surface between the cylinder block section 117 and the cylinder head 118. The bridging sections 144 increase the stiffness of the cylinder block section 117.

[0067] Fig. 11 is an enlarged cross-sectional view of parts around the in Fig. The combustion pressure sensor 140 shown in Figure 10 is located around the cylinder block section 117. The cylinder block section 117 has a sensor support hole 145 at a position near the combustion chamber 131 on an upper section of the cylinder block section 117. The sensor support hole 145 supports the combustion pressure sensor 140. The sensor support hole 145 extends through the cylinder block section 117 in the radial direction of the cylinder bore 128. The sensor support hole 145 is located upstream of the cylinder bore 128 and is oriented perpendicular to the axis 111a of the crankshaft 111 and the cylinder axis 113a.

[0068] The sensor support hole 145 extends through the outer wall section 142, the bridging section 144, and the cylinder bore 128. Part of the sensor support hole 145 is located within the bridging section 144. The sensor support hole 145 comprises a support hole section 145a and a sensing hole 145b. The support hole section 145a extends from an outer surface of the outer wall section 142 inward toward the side of the cylinder bore 128. The sensing hole 145b provides a connection between the support hole section 145a and an inner surface of the cylinder bore 128.

[0069] The pressure-sensitive section 140b and the main unit 140a of the combustion pressure sensor 140 are inserted into and supported in the support hole section 145a. The sensing hole 145b is designed to have a smaller diameter than the diameter of the pressure-sensitive section 140b of the combustion pressure sensor 140. The combustion pressure sensor 140 is inserted into the support hole section 145a from the outside on the rear side of the cylinder block section 117. An outer circumferential section of a distal end face of the pressure-sensitive section 140b is then brought into contact with a shoulder between the sensing hole 145b and the support hole section 145a. The pressure-sensitive section 140b is exposed to the inside of the cylinder bore 128 via the sensor support hole 145.

[0070] The combustion pressure sensor 140 is arranged in the sensor support hole 145 such that a sensor axis 140d of the combustion pressure sensor 140 is aligned orthogonally in one direction to the axis 111a of the crankshaft 111 and the cylinder axis 113a. The combustion pressure sensor 140 is located behind the cylinder bore 128. The sensor axis 140d passes through the center point of the pressure-sensitive section 140b and the main unit 140a. The combustion pressure sensor 140 is secured in the sensor support hole 145 in such a way that it hermetically seals the cylinder bore 128. The combustion pressure sensor 140 is shown, by way of example, secured in the sensor support hole 145 using a threaded section provided for the combustion pressure sensor 140. This fastening method serves only for illustration and is not limiting.

[0071] The piston 116 comprises, in one piece, a piston head section 150, a skirt section 151, and a piston pin attachment section 152. The piston head section 150 is disc-shaped. The skirt section 151 extends from a portion of an outer circumferential section 150a of the piston head section 150 toward the side of the crankshaft 111. The piston pin attachment section 152 is located on a rear surface of an upper surface 116a of the piston head section 150. Several piston rings 153a, 153b, and 153c are successively inserted into grooves in the outer circumferential section 150a of the piston head section 150, starting from the side of the upper surface 116a.

[0072] The piston pin 126a is guided through a hole in the piston pin extension section 152. The skirt section 151 extends below a front section and a rear section of the piston head section 150. In particular, the skirt section 151 is formed into sections of the piston 116 that are arranged orthogonally to the piston pin 126a in one direction. The piston pin extension section 152 extends towards the side of the skirt section 151 and is connected to a rear surface of the skirt section 151.

[0073] The piston head section 150 has a recess 155 formed in an upper section of the outer circumferential section 150a. The recess 155 extends inwards in the radial direction of the piston 116. The recess 155 is continuous, so that it abuts the upper surface 116a of the piston 116. The recess 155 has a bottom surface which consists of a flat surface extending parallel to the axis 111a of the crankshaft 111. The recess 155 can be formed, for example, by machining a portion of the outer circumferential section 150a to create a shoulder.

[0074] The recess 155 is formed at a location between the piston ring 153a, which is closest to the upper surface 116a, and the upper surface 116a. This arrangement allows the recess 155 to be formed while the piston ring 153a is positioned at a suitable location. The recess 155 has a depth less than the thickness t1 in the radial direction of the piston ring 153a. Furthermore, the recess 155 has a length in the axial direction of the piston 116 that is greater than the wall thickness t2 of the piston ring 153a.

[0075] The recess 155 is arranged such that, under a condition where the piston 116 is at top dead center, it lies on an extension of the sensor axis 140d of the combustion pressure sensor 140. Thus, under the condition where the piston 116 is at top dead center, the pressure-sensitive section 140b of the combustion pressure sensor 140 is exposed to the inside of the recess 155 and lies opposite the recess 155 via the sensing hole 145b.

[0076] Additionally, when the piston 116 is at top dead center, a gap 156 is formed between the upper surface 116a of the piston 116 and a lower surface of the cylinder head 118, and this gap 156 is connected to the recess 155. When the piston 116 is at top dead center, the pressure-sensitive section 140b of the combustion pressure sensor 140 is connected to the combustion chamber 131 via the sensing hole 145b, the recess 155, and the gap 156. Consequently, when the piston 116 is at top dead center, the combustion pressure sensor 140 can detect pressure in the combustion chamber 131.

[0077] Under a condition where the piston 116 is in a position other than top dead center, for example, under a condition where the piston 116 is at bottom dead center, the pressure-sensitive section 140b of the combustion pressure sensor 140 is exposed to the inside of the cylinder bore 128 via the sensing hole 145b. Consequently, the combustion pressure sensor 140 can detect pressure inside the cylinder bore 128.

[0078] Fig. Figure 13 is a functional block diagram illustrating an embodiment of the main components of a misfire detection device according to one embodiment of the present invention. Components identical to those shown in the preceding drawings are described using the same reference numerals as those used in the preceding drawings.

[0079] Misfire detection is one of the functions performed by an electronic control unit (ECU). An output from the pulse generator sensor 67 is applied to a misfire detection device 200 of the ECU. The misfire detection device 200 comprises a NE calculation unit 201, a combustion pressure-based detection unit 202, and an angular velocity-based detection unit 203. The NE calculation unit 201 calculates an engine speed NE using the output from the pulse generator sensor 67. The combustion pressure-based detection unit 202 performs a combustion pressure-based detection of a misfire in a cylinder in which the combustion pressure sensor 40 or 140 is located, using the output from the combustion pressure sensor 40 (140).The angular velocity-based detection unit 203 performs an angular velocity-based detection of a misfire in the remaining cylinder in which the combustion pressure sensor 40 (140) is not located, using a change in the crank angular velocity ω.

[0080] In the combustion pressure-based sensing unit 202, a crank angle sensing part 202a detects a crank angle to obtain a displacement volume of each cylinder. A combustion pressure sensing part 202b calculates a combustion pressure in the cylinder based on the output from the combustion pressure sensor 40 (140). The IMEP (mean effective pressure) calculation part 202c receives, as in Fig. Figure 14 shows a specified diagram (pressure-volume (PV) diagram) based on a relationship between a displacement volume value obtained using the crank angle and the output of the combustion pressure sensor 40 (140) and calculates, as IMEP, the value of a range within a curve drawn from a top dead center (TDC) on the compression stroke through a bottom dead center (BDC) on the expansion stroke to a TDC on the exhaust stroke, and further from a BDC on the intake stroke back to the TDC on the compression stroke.

[0081] Fig. Figure 14 illustrates exemplary diagrams that demonstrate the relationship between displacement volume and cylinder pressure when combustion occurs normally ( Fig. 14(a)) and if a misfire occurs ( Fig. 14(b)). The mean effective pressure IMEP is defined as the area of ​​an enclosed region (hatched section) drawn from the BDC on the intake stroke to the BDC on the expansion stroke via the TDC of the intake stroke.

[0082] When combustion occurs normally, the IMEP has a predetermined range, as shown in Fig. 14(a) shown. If, on the other hand, a misfire occurs, a mixture that is adiabatically compressed on the compression stroke does not burn and is thus adiabatically expanded. Consequently, the same line is followed, and this essentially leads to a zero region, as shown in Fig. Figure 14(b) illustrates this. Thus, a misfire can be detected by setting a threshold value IMEP_ref with a tolerance range.

[0083] A misfire detection unit 202d compares the IMEP with the predefined threshold value IMEP_ref. If it detects that IMEP < IMEP_ref, then the misfire detection unit 202d detects a misfire condition in the corresponding cylinder. Alternatively, the misfire detection unit 202d can compare the IMEP_n-1 calculated in a previous cycle with the IMEP_n calculated in the current cycle, and if it detects that IMEP_n is significantly lower than IMEP_n-1, the misfire detection unit 202d can detect a misfire condition.

[0084] In the angular velocity-based detection unit 203, an angular velocity detection part 203a calculates the crank angular velocity ω at each crank angle based on a pulse time. A misfire parameter calculation part 203b calculates a suitable misfire parameter using the crank angular velocity ω. A misfire detection part 203c detects a misfire based on the misfire parameter and a change in the crank angular velocity ω.

[0085] According to the embodiment of the present invention, angular velocity-based detection of a misfire is performed without installing a combustion pressure sensor for the cylinder in which the expansion stroke period does not overlap and angular velocity-based misfire detection is possible, and combustion pressure-based detection of a misfire is performed by installing the combustion pressure sensor for the cylinder in which the expansion stroke period overlaps and thus angular velocity-based misfire detection is difficult to perform. This arrangement reduces the number of combustion pressure sensors used compared to the prior art, in which all cylinders are equipped with combustion pressure sensors.Thus, misfire detection can be achieved with high accuracy through simple configuration and at low cost.

[0086] Furthermore, according to the embodiment of the present invention, a PV diagram is obtained based on the relationship between the displacement value obtained from the crankshaft angle sensor and the output of the combustion pressure sensor, and a misfire condition is detected based on the IMEP within the curve drawn from the TDC on the compression stroke to the BDC on the expansion stroke in the specified diagram. This approach enables a quantitative determination of engine combustion conditions, thus allowing for meaningful misfire detection.

[0087] Furthermore, according to the embodiment of the present invention, the combustion pressure sensor is arranged in the cylinder head between adjacent cylinders, and the pressure-sensitive section 40b (140b) of the combustion pressure sensor is exposed for a connection path that is in contact with the combustion chamber of the cylinder for which a misfire is to be detected. This arrangement allows the sensor to be mounted in a position that is uniform for different engine types, even if misfire detection is only to be carried out in one of the adjacent cylinders at a time, and allows the shape of the connection path to be varied between different engine types.

[0088] Furthermore, the embodiment of the present invention has been described for an arrangement in which the combustion pressure sensor is located only in the cylinder of the cylinder pair in which the explosion occurs first, where the expansion cycles overlap. This exemplary arrangement serves only for illustration and is not limiting. The combustion pressure sensor can nevertheless be located only in the cylinder in which the explosion occurs later, or it can be located in both cylinders. Furthermore, in an embodiment with several cylinder pairs in which the expansion cycles overlap, the combustion pressure sensor can be located either in one or in both cylinders of each pair. List of reference symbols:

[0089] 10(110)...Engine, 11(111)...Crankshaft, 13(113)...Cylinder section, 17(117)...Cylinder block section, 18(118)...Cylinder head, 30(130)...Spark plug, 40(140)...In-cylinder combustion pressure sensor, 40b(140b)...Pressure-sensitive section, 45(145)...Sensor support hole, 53...Pulse generator ring, 67...Pulse generator sensor, 125...Cylinder, 200...Misfire detection device, 201...NE calculation unit, 202...Combustion pressure-based detection unit, 203...Angular velocity-based detection unit

Claims

[1] A misfire detection device for a four-stroke multi-cylinder engine having a pair of cylinders in which explosion occurs sequentially and which has an explosion timing characteristic of partially overlapping periods of an expansion stroke, the misfire detection device comprising: means (53, 66, 67) for detecting an angular velocity of a crank; a combustion pressure sensor (40, 140) arranged in at least one cylinder of the cylinder pair; a combustion pressure-based detection device (202) for detecting a misfire in the cylinder in which the combustion pressure sensor is arranged, using an output from the combustion pressure sensor; and angular velocity-based detection means (203) for detecting a misfire in each of the remaining cylinders in which the combustion pressure sensor is not arranged, using the crank angular velocity. [2] Misfire detecting device according to claim 1, wherein the engine is an irregular burst interval engine with a pair of cylinders in which the burst intervals are less than 180 degrees. [3] Misfire detecting device according to claim 2, wherein the engine is an irregular burst interval engine with a pair of cylinders in which burst intervals are 90 degrees. [4] A misfire detection device according to any one of claims 1 to 3, wherein the combustion pressure-based detection means (202) comprises: means (202a) for detecting a crank angle; means (202b) for detecting combustion pressure in a cylinder using an output from the combustion pressure sensor; means (202c) for calculating the IMEP (indicated mean effective pressure) using a PV (pressure-volume) diagram representing a relationship between a displacement value based on the crank angle and an output of the combustion pressure sensor; and a misfire detecting means (202d) for detecting a misfire condition using the IMEP. [5] Misfire detecting device according to claim 4, wherein the misfire detection means (202d) compares an IMEP obtained in a current cycle with a misfire detection threshold IMEP_ref, and upon detecting that IMEP < IMEP_ref, the misfire detection means (202d) detects a misfire condition. [6] A misfire detecting apparatus according to claim 4, wherein the misfire detecting means (202d) compares an IMEP_n-1 calculated in a previous cycle with the IMEP_n calculated in a current cycle, and upon detecting that IMEP_n is smaller than IMEP_n-1, the misfire detecting means (202d) detects a misfire condition. [7] A misfire detecting device according to any one of claims 1 to 6, wherein the combustion pressure sensor (40, 140) is arranged in a cylinder head between cylinders which are adjacent to each other, and a pressure-sensitive portion (40b, 140b) of the combustion pressure sensor (40, 140) is exposed to a communication path communicating with a combustion chamber.

Images