Piston behavior analysis device and piston behavior analysis method

Abstract

To provide a piston behavior analysis device capable of analyzing a piston behavior with higher accuracy over a wider range (for example, between the bottom dead center and the top dead center).SOLUTION: A piston behavior analysis device 1 comprises: multiple gap sensors 30 which are arranged apart from each other along an axial direction on an inner surface of a cylinder 102 of an engine 10, and detect a distance to a piston 103; and an analysis unit 50 which determines an inclination (piston behavior) of the piston 103 on the basis of the distance to the piston 103 and a profile of a piston skirt 103a, which is acquired and stored in advance for each of the multiple gap sensors 30. The analysis unit 50 switches the gap sensors 30 and the profile of the piston skirt 103a to be used according to a crank angle, corrects the distance to the piston 103 using the profile of the piston skirt 103a, and determines the inclination of the piston 103 on the basis of the corrected distance to the piston 103.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a piston behavior analysis device and a piston behavior analysis method for analyzing the behavior of a piston. [Background technology]

[0002] In an engine, the reciprocating linear motion of the piston is converted into rotational motion by a connecting rod (hereinafter referred to as "connecting rod") and a crankshaft. In such an engine, a force (side thrust) acts on the piston, pressing the side of the piston against the inner wall of the cylinder due to the tilt of the connecting rod (according to its swing).

[0003] The inclination of the connecting rod reverses at the top dead center of compression, reversing the direction of the side thrust (side pressure), causing the piston to wobble. This causes the side of the piston to collide with the inner wall of the cylinder (piston slap), resulting in a piston slapping noise.

[0004] Incidentally, analysis of piston behavior is carried out when formulating countermeasures against piston slapping noise, confirming the effectiveness of those countermeasures, etc. For example, Patent Document 1 discloses a technology in which a gap sensor that measures the gap between the piston and the cylinder liner on the top dead center side of the piston is attached to the cylinder block, and piston behavior during engine operation is analyzed.

[0005] More specifically, in the technology described in Patent Document 1, in order to reduce the effect of heat on the gap sensors, a pair of gap sensors is arranged on the left and right sides of the piston, one above the other, and the other below, and these sensors are arranged across a water jacket that is arranged to surround the cylinder liner. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-329546 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, the technology described in Patent Document 1 can reduce the thermal effects on the gap sensor when analyzing piston behavior near top dead center. On the other hand, analyzing piston behavior over a wide range from bottom dead center to top dead center with high accuracy requires increasing the number of gap sensors. However, variations in the gap sensors (e.g., variations in characteristics and mounting positions) can increase errors (reduce accuracy). Furthermore, for example, the profile (shape) of the piston skirt is not necessarily linear, which can increase errors (reduce accuracy).

[0008] The present invention has been made to solve the above-mentioned problems, and aims to provide a piston behavior analysis device and a piston behavior analysis method that are capable of analyzing piston behavior with higher accuracy over a wider range (for example, between bottom dead center and top dead center). [Means for solving the problem]

[0009] A piston behavior analysis device according to one aspect of the present invention comprises a plurality of gap sensors arranged axially at predetermined intervals on the inner surface of an engine cylinder to detect the distance to the piston, and an analysis unit that calculates piston behavior, including piston inclination, based on the distance to the piston detected by each of the plurality of gap sensors and a piston skirt profile that is acquired in advance and stored for each of the plurality of gap sensors. The analysis unit switches the gap sensor and piston skirt profile to be used depending on the crank angle, and uses the piston skirt profile to correct the distance to the piston detected by the gap sensor, and calculates piston behavior, including piston inclination, based on the corrected distance to the piston.

[0010] According to one aspect of the present invention, a piston behavior analysis device includes a plurality of gap sensors arranged axially at predetermined intervals on the inner surface of an engine cylinder to detect the distance to the piston. This allows the distance to the piston to be detected over a wider range (e.g., between bottom dead center and top dead center). This allows for a wider range of piston behavior analysis. Furthermore, a piston skirt profile is acquired and stored in advance for each of the plurality of gap sensors. The gap sensor and piston skirt profile to be used are switched depending on the crank angle (piston position). The piston skirt profile is then used to correct the distance to the piston detected by the gap sensor. The piston behavior, including the inclination of the piston, is calculated based on the corrected distance to the piston. This reduces value jumps (steps) when switching between gap sensors, enabling highly accurate analysis of piston behavior. [Effects of the Invention]

[0011] According to the present invention, it is possible to analyze piston behavior with higher accuracy over a wider range (for example, between bottom dead center and top dead center). [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram illustrating a configuration of a piston behavior analysis device according to an embodiment. [Figure 2] 10A and 10B show examples of piston skirt profiles acquired by each gap sensor, where FIG. 10A shows an example of a profile acquired when the piston moves from bottom dead center to top dead center, and FIG. 10B shows an example of a profile acquired when the piston moves from top dead center to bottom dead center. [Figure 3] 10A and 10B are diagrams for explaining a method of switching gap sensors used when determining the inclination of a piston, etc. [Figure 4]5A to 5C are diagrams for explaining how the piston behavior analysis device according to the embodiment determines the inclination and translational movement amount of the piston. [Figure 5] 10A and 10B are diagrams showing an example of changes in piston inclination (piston behavior) with respect to the crank angle acquired by the piston behavior analysis device according to the embodiment, where (a) shows the results of a comparative example (when the piston skirt profile is not switched for each gap sensor), and (b) shows the results of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts will be designated by the same reference numerals. In addition, the same elements will be designated by the same reference numerals in each drawing, and redundant explanations will be omitted.

[0014] First, the configuration of a piston behavior analysis device 1 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of the piston behavior analysis device 1.

[0015] A cylindrical cylinder liner 102 is provided in a cylinder block 101 of the engine 10 to allow the piston 103 to reciprocate smoothly while maintaining airtightness between the cylinder and the piston 103. The cylinder liner 102 is made of, for example, cast iron, and is cast or press-fit into the cylinder block 101. The piston 103 is housed in the cylinder liner 102 so that it can reciprocate freely.

[0016] In the engine 10, a piston 103 reciprocates within a cylinder liner 102, repeatedly performing four strokes of intake, compression, expansion, and exhaust, thereby combusting a mixture of air and fuel to generate driving force.

[0017] The piston 103 is made of, for example, an aluminum alloy and is formed in a substantially cylindrical shape. Three rows of annular piston ring grooves are formed in the piston land on the outer peripheral surface of the piston along the axial direction. A piston ring 103b is fitted in each piston ring groove.

[0018] One end of a connecting rod 104 is rotatably connected to the piston 103. The other end of the connecting rod 104 is rotatably attached to a crank pin (not shown) of a crank arm. In the engine 10, the reciprocating linear motion of the piston 103 is converted into rotational motion by the connecting rod 104 and the crankshaft (not shown).

[0019] As described above, in engine 10, a force (side thrust (side pressure)) that presses the side of the piston against the inner wall of the cylinder acts on piston 103 due to the inclination (depending on the swing) of connecting rod 104. Here, the side on which the side thrust acts during the expansion stroke (immediately after top dead center of compression) is referred to as the "thrust side," and the opposite side is referred to as the "anti-thrust side."

[0020] The inclination of the connecting rod 104 reverses at the compression top dead center, and the direction of the side thrust (side pressure) reverses, causing the piston 103 to swing. Then, the side of the piston collides with the inner wall of the cylinder (piston slap occurs), generating a piston slapping noise (slap sound).

[0021] Therefore, the piston behavior analysis device 1 is used to analyze the behavior of the piston 103, for example, when formulating countermeasures against piston slapping noises and when confirming the effectiveness of those countermeasures.

[0022] In particular, the piston behavior analysis device 1 has the function of analyzing piston behavior with higher accuracy over a wider range (for example, between bottom dead center and top dead center).

[0023] For this reason, the piston behavior analysis device 1 is provided with a plurality of gap sensors 30 (7 rows x 2 columns = 14 sensors in this embodiment) that are arranged (disposed) at predetermined intervals (spaced apart) along the axial direction (linearly) on the inner surface (inner peripheral surface) of the cylinder liner (cylinder) 102 of the engine 10. The plurality of gap sensors 30 (7 rows x 2 columns = 14 sensors) are arranged (disposed) with seven sensors on each of the thrust side and the anti-thrust side, and are arranged facing each other.

[0024] Each gap sensor 30 detects the distance (gap) between the inner surface (inner peripheral surface) of the cylinder liner (cylinder) 102 and the piston 103. For example, an eddy current type gap sensor can be suitably used as the gap sensor 30. Note that instead of the eddy current type gap sensor, a gap sensor of another type, for example, an optical type, may be used.

[0025] The plurality of gap sensors 30 are connected to an analysis unit 50. A detection signal (output signal) of each gap sensor 30 is input to the analysis unit 50. The analysis unit 50 is also connected to various sensors, such as a crank angle sensor 31 that is attached near the crankshaft of the engine 10 and detects the rotational position of the crankshaft (i.e., the movement position of the piston 103). The crank angle sensor 31 may be, for example, an electromagnetic pickup type.

[0026] An engine control unit (ECU), a personal computer (PC), or the like can be used as the analysis unit 50. In this embodiment, an ECU is used as the analysis unit 50. The analysis unit (ECU) 50 is configured to include, for example, a microprocessor that performs calculations, an EEPROM that stores programs and the like for causing the microprocessor to execute each process, a RAM that stores various data such as calculation results, a backup RAM that maintains the stored contents using a battery or the like, and an input / output I / F.

[0027] In particular, the analysis unit 50 functionally comprises a storage unit 50a and an analysis unit 50b in order to analyze piston behavior more accurately over a wider range (for example, between bottom dead center and top dead center). In the analysis unit 50, the functions of the storage unit 50a and the analysis unit 50b are realized by a microprocessor executing a program stored in an EEPROM or the like.

[0028] The storage unit 50a includes a memory such as an EEPROM, and stores profiles (data) of the piston skirt 103a acquired in advance for each of the plurality of gap sensors 30. More specifically, the storage unit 50a stores in advance, for each of the plurality of gap sensors 30, the profile (data) of the piston skirt 103a acquired when the piston 103 moves from the bottom dead center to the top dead center, and the profile (data) of the piston skirt 103a acquired when the piston 103 moves from the top dead center to the bottom dead center.

[0029] FIG. 2 shows an example of a profile of the piston skirt 103a acquired by each gap sensor 30 (more specifically, gap sensors 3001-3007 disposed on the thrust side). FIG. 2(a) shows an example of a profile acquired when the piston 103 moves from bottom dead center to top dead center, and FIG. 2(b) shows an example of a profile acquired when the piston 103 moves from top dead center to bottom dead center. In FIGS. 2(a) and 2(b), the horizontal axis represents the profile (mm) of the piston skirt 103a, and the vertical axis represents the distance (mm) from the bottom end of the piston skirt 103a. The data in FIGS. 2(a) and 2(b) was acquired by motoring at 100 rpm with compression pressure released (with the spark plug removed).

[0030] 2(a) and 2(b), the piston skirt 103a is formed in a shape that bulges outward (radially outward) in an arc near the center. Also, variations are observed in the profiles of the piston skirt 103a acquired by each gap sensor 30. Even with the same gap sensor 30, differences are observed between the profile of the piston skirt 103a acquired when the piston 103 moves from bottom dead center to top dead center and the profile of the piston skirt 103a acquired when the piston moves from top dead center to bottom dead center.

[0031] Therefore, the profile (data) of the piston skirt 103a used for correction is switched (details will be described later) for each gap sensor 30 and between before and after top dead center (i.e., when the piston 103 moves from bottom dead center toward top dead center and when it moves from top dead center toward bottom dead center). Note that the profile (data) of the piston skirt 103a is preferably stored as a map (lookup table), for example.

[0032] The analysis unit 50b determines the piston behavior, including the inclination and translational movement of the piston 103 for each crank angle, based on the distance (gap) to the piston 103 detected by each of the multiple gap sensors 30 and the profile (data) of the piston skirt 103a acquired in advance for each of the multiple gap sensors 30 and stored in the memory unit 50a.

[0033] At this time, the analysis unit 50b switches (selects) the profile of the gap sensor 30 and piston skirt 103a to be used depending on the crank angle (movement position of the piston 103), and uses the switched (selected) profile of the piston skirt 103a to correct the distance (gap) to the piston 103 detected by the switched (selected) gap sensor 30, and calculates the piston behavior including the inclination and translational movement amount of the piston 103 based on the corrected distance (gap) to the piston 103.

[0034] More specifically, as indicated by hatching in Fig. 3, the analysis unit 50b sequentially switches between the two pairs of gap sensors 30 to be used in accordance with the crank angle (the position of the piston 103) (i.e., in accordance with the movement of the piston 103). More specifically, as the piston 103 moves from the bottom dead center to the top dead center, the analysis unit 50b sequentially switches from the gap sensor 3007 (3014) on the bottom dead center side to the gap sensor 3001 (3008) on the top dead center side. On the other hand, as the piston 103 moves from the top dead center to the bottom dead center, the analysis unit 50b sequentially switches from the gap sensor 3001 (3008) on the top dead center side to the gap sensor 3007 (3014) on the bottom dead center side. Note that Fig. 3 is a diagram for explaining a method of switching between the gap sensors 30 used to determine the inclination, etc., of the piston 103.

[0035] Furthermore, the analysis unit 50b sequentially switches the profile (data) of the piston skirt 103a used for correction depending on the crank angle and the moving direction of the piston 103. That is, the analysis unit 50b switches the profile (data) of the piston skirt 103a used for correction between when the piston 103 moves from the bottom dead center to the top dead center and when the piston 103 moves from the top dead center to the bottom dead center.

[0036] 4, the analysis unit 50b determines (calculates) piston behavior including the inclination θ and translational movement amount x of the piston 103 for each crank angle based on distances (gaps) G1' and G2' from the piston 103 detected by each of a pair of axially adjacent gap sensors 30 disposed on the thrust side, and distances (gaps) G8' and G9' from the piston 103 detected by each of a pair of axially adjacent gap sensors 30 disposed on the anti-thrust side opposite the pair of gap sensors 30, and profiles (data) of the piston skirt 103a acquired in advance and stored by the two pairs of gap sensors 30. Here, FIG. 4 is a diagram for explaining how the piston behavior analysis device 1 determines the inclination θ and translational movement amount x of the piston 103.

[0037] The inclination angle θ of the piston 103 can be calculated from the following equation (1). θ=tan -1 [{G2-G1}+(G8-G9)] / 2a] ···(1) G1, G2, G8, and G9 are the gaps after correction, and a is the gap between adjacent pairs of gears. The distance (spacing) in the axial direction of the cap sensor. Here, the above equation (1) is based on the assumption that the profile of the piston skirt 103a is linear. However, as mentioned above, in reality the profile of the piston skirt 103a is rounded, so the detected gap values ​​(G1', G2', G8', G9') are corrected.

[0038] Here, since the inclination of piston 103 is unknown at first, gaps (distances from piston 103) G1', G2', G8', and G9' are corrected assuming that piston 103 is not inclined, and the inclination angle θ of piston 103 is found using the corrected gaps G1, G2, G8, and G9. Next, the inclination angle θ is used to correct gaps G1', G2', G8', and G9', and the inclination angle θ is found using the corrected gaps G1, G2, G8, and G9. This calculation is repeated until the inclination angle θ converges, and the inclination angle θ of piston 103 (inclination angle θ when converged) is found.

[0039] The translational movement amount x of the piston 103 can be calculated using the following equations (2) to (4). x=[{(G1-G8)+ε s1}+{(G2-G9)+ε s2}] / twenty two) ε s1 =(h1-hp)tanθ (3) ε s2 =(hp-h2)tanθ (4) Here, h1 is the distance (high) from a certain reference plane to the gap sensor 3001 (3008). h2 is the distance (height) to the gap sensor 3002 (3009), and hp is the piston This is the distance (height) to the center of the tonnage.

[0040] When determining the tilt and translational movement amount (piston behavior) of the piston 103, the analysis unit 50b preferably performs the following corrections (i) to (iv) in addition to the above-mentioned corrections. (i) Correction of the mounting position deviation of the gap sensor 30: Correct the deviation of the distance between the gap sensor 30 and the inner wall of the cylinder liner 102 (0 mm reference position). (ii) Temperature drift correction of the gap sensor 30: The fluctuation of the output value (output characteristics) of the gap sensor 30 in response to temperature changes is corrected. (iii) Correction of the shape (waviness) of the cylinder liner 102: Correct the bore shape (waviness of the cylinder liner 102). (iv) Thermal expansion correction of the piston 103 and the cylinder liner 102: The gap difference between the cold state and the fully warmed state (amount of expansion from the cold state to the fully warmed state) is corrected.

[0041] Next, a piston behavior analysis method will be described. First, in a detection step, a distance (gap) between the inner surface of the cylinder liner (cylinder) 102 and the piston 103 is detected by a plurality of gap sensors 30 that are arranged (disposed) in a line at predetermined intervals (spaced apart) along the axial direction (linearly) on the inner surface (inner peripheral surface) of the cylinder liner (cylinder) 102 of the engine 10.

[0042] Next, in the analysis step, the piston behavior, including the inclination and translational movement amount of the piston 103 for each crank angle, is determined (calculated) based on the distance (gap) to the piston 103 detected in the detection step and the profile (data) of the piston skirt 103a previously acquired and stored for each of the plurality of gap sensors 30.

[0043] In this analysis step, the profile (data) of the gap sensor 30 and piston skirt 103a to be used is switched (selected) depending on the crank angle (movement position of the piston 103), and the profile (data) of the switched (selected) piston skirt 103a is used to correct the distance (gap) to the piston 103 detected by the switched (selected) gap sensor 30, and the piston behavior including the inclination and translational movement amount of the piston 103 is determined based on the corrected distance (gap) to the piston 103.

[0044] More specifically, the two pairs of gap sensors 30 used for the calculation are switched sequentially according to the crank angle (movement position of the piston 103) (i.e., as the piston 103 moves). Also, the profile (data) of the piston skirt 103a used for the correction is switched sequentially according to the crank angle and the movement direction of the piston 103. That is, the profile (data) of the piston skirt 103a used for the correction is switched between when the piston 103 moves from the bottom dead center to the top dead center and when the piston 103 moves from the top dead center to the bottom dead center.

[0045] Then, piston behavior including the inclination and translational movement amount of piston 103 for each crank angle is determined (calculated) based on the distance (gap) to piston 103 detected by each of a pair of gap sensors 30 arranged on the thrust side and adjacent to each other in the axial direction, the distance (gap) to piston 103 detected by each of a pair of gap sensors 30 arranged on the anti-thrust side and adjacent to each other in the axial direction, and profiles (data) of piston skirt 103a acquired in advance by the two pairs of gap sensors 30. Note that the method for determining the inclination and translational movement amount of piston 103 is as described above, and therefore a detailed description thereof will be omitted here.

[0046] As described above in detail, according to this embodiment, a plurality of gap sensors 30 are arranged at predetermined intervals along the axial direction on the inner surface of the cylinder liner 102 of the engine 10 to detect the distance (gap) between the inner surface of the cylinder liner 102 and the piston 103. This makes it possible to detect the distance to the piston over a wider range (for example, between bottom dead center and top dead center). In other words, it is possible to analyze piston behavior over a wider range.

[0047] Furthermore, a profile of the piston skirt 103a is acquired and stored in advance for each of the gap sensors 30. The profile of the gap sensor 30 and the piston skirt 103a to be used is switched (selected) depending on the crank angle (movement position of the piston 103). The profile of the switched (selected) piston skirt 103a is then used to correct the distance (gap) to the piston 103 detected by the switched (selected) gap sensor 30. The piston behavior, including the inclination and translational movement of the piston 103, is calculated based on the corrected distance (gap) to the piston 103. This improves value jumps (reduces steps) when the gap sensor 30 is switched, enabling piston behavior to be analyzed with high accuracy. As a result, piston behavior can be analyzed with high accuracy over a wider range (for example, between bottom dead center and top dead center).

[0048] In addition (especially), according to this embodiment, a profile (data) of the piston skirt 103a when the piston 103 moves from bottom dead center to top dead center and a profile (data) of the piston skirt 103a when the piston 103 moves from top dead center to bottom dead center are acquired in advance and stored for each of the plurality of gap sensors 30, and the profile of the piston skirt 103a used for correction is switched between when the piston 103 moves from bottom dead center to top dead center and when the piston 103 moves from top dead center to bottom dead center. Therefore, the piston behavior when the piston 103 moves from bottom dead center to top dead center and the piston behavior when the piston 103 moves from top dead center to bottom dead center can be analyzed with higher accuracy.

[0049] FIG. 5 shows an example of the change in inclination of the piston 103 (piston behavior) relative to the crank angle acquired by the piston behavior analysis device 1. FIG. 5(a) shows the results of a comparative example (when the piston skirt profile is not switched for each gap sensor 30), and FIG. 5(b) shows the results of this embodiment. The horizontal axis of FIGS. 5(a) and 5(b) is the crank angle (deg. ATDC), and the vertical axis is the inclination angle (deg.) of the piston 103. In FIGS. 5(a) and 5(b), the dashed line shows the moving average of the acquired inclination angle of the piston 103 (solid line graph).

[0050] As shown in Figure 5(a), in the comparative example, that is, when the piston skirt profile is not switched for each gap sensor 30 (for example, when a single piston skirt profile obtained by a three-dimensional measuring device is used), when the gap sensor 30 used for angle calculation is switched, the value (tilt angle of the piston 103) jumps (a step occurs), making it difficult to accurately analyze the actual behavior.

[0051] On the other hand, according to this embodiment, that is, for each of the plurality of gap sensors 30, a profile of the piston skirt 103a when the piston 103 moves from bottom dead center to top dead center and a profile of the piston skirt 103a when the piston 103 moves from top dead center to bottom dead center are acquired and stored in advance, and the profile is switched for each gap sensor 30 according to the crank angle, and the profile used for correction is switched separately for when the piston 103 moves from bottom dead center to top dead center and when it moves from top dead center to bottom dead center. As shown in Figure 5(b), it has been confirmed that value jumps when the gap sensor 30 is switched can be improved (steps can be reduced), and piston behavior can be analyzed with high accuracy.

[0052] Furthermore, according to this embodiment, multiple gap sensors 30 are disposed on the thrust side and the anti-thrust side, respectively, and are disposed facing each other, so that the inclination of the piston 103 in the thrust direction and the anti-thrust direction (which may cause piston slapping noise) (piston behavior) and the like can be accurately grasped.

[0053] According to this embodiment, the two pairs of gap sensors 30 to be used are switched sequentially according to the crank angle (movement position of the piston 103) (according to the movement of the piston 103), and the profile (data) of the piston skirt 103a is switched sequentially according to the crank angle and the movement direction of the piston 103. Then, piston behavior, including the inclination and translational movement amount of the piston 103, is determined based on the distance (gap) from the piston 103 detected by each of a pair of gap sensors 30 arranged on the thrust side and adjacent to each other in the axial direction, the distance (gap) from the piston 103 detected by each of a pair of gap sensors 30 arranged on the anti-thrust side opposite the pair of gap sensors 30, and the profile (data) of the piston skirt 103a acquired in advance by the two pairs of gap sensors 30 and stored. Therefore, by using two pairs (four) of gap sensors 30, piston behavior can be analyzed with even higher accuracy.

[0054] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications are possible. For example, in the above embodiments, the present invention is applied to an engine 10 having a cylinder in which a cylinder liner 102 is provided in a cylinder block 101, but it can also be applied to an engine having a linerless cylinder. When applied to such an engine, the gap sensor 30 is attached to the peripheral wall of the cylinder formed in the cylinder block (for example, a peripheral wall on which a predetermined treatment is applied to the sliding surface of the cylinder).

[0055] In the above embodiment, an ECU (a control unit dedicated to engine control) is used as the analysis unit 50, but for example, a PC (personal computer) or the like may also be used.

[0056] In the above embodiment, two pairs (four pieces) of gap sensors 30 are used to determine the inclination of piston 103, but one pair (two pieces) of gap sensors 30 may be used to determine the inclination of piston 103. Also, in the above embodiment, an eddy current type gap sensor 30 is used, but other types, such as an optical type, may also be used. Furthermore, the number of gap sensors 30 is not limited to the above embodiment, and can be set arbitrarily according to required requirements, etc. [Explanation of symbols]

[0057] 1 Piston behavior analysis device 10 Engine 101 Cylinder block 102 Cylinder liner (cylinder) 103 Piston 103a Piston skirt 103b Piston ring 104 Connecting rod 30(3001~3014) Gap sensor 31 Crank angle sensor 50 Analysis Unit (ECU) 50a storage section 50b Analysis Department

Claims

1. a plurality of gap sensors arranged at predetermined intervals along the axial direction on the inner surface of the cylinder of the engine, for detecting a distance from the piston; an analysis unit that determines piston behavior including piston inclination based on the distances to the piston detected by each of the plurality of gap sensors and piston skirt profiles that are acquired in advance for each of the plurality of gap sensors and stored; The analysis unit switches the gap sensor and piston skirt profile to be used depending on the crank angle, corrects the distance to the piston detected by the gap sensor using the piston skirt profile, and determines piston behavior including piston inclination based on the corrected distance to the piston.

2. a piston skirt profile acquired when the piston moves from the bottom dead center to the top dead center and a piston skirt profile acquired when the piston moves from the top dead center to the bottom dead center are stored in advance for each of the plurality of gap sensors; 2. The piston behavior analysis device according to claim 1, wherein the analysis unit switches the piston skirt profile used for correction depending on whether the piston is moving from bottom dead center to top dead center or top dead center to bottom dead center.

3. 3. The piston behavior analyzer according to claim 2, wherein the plurality of gap sensors are disposed on the thrust side and the counter-thrust side, respectively, and are disposed opposite each other.

4. The analysis unit Piston behavior including inclination of the piston is determined based on the distances to the piston detected by each of a pair of axially adjacent gap sensors, the distances to the piston detected by each of a pair of axially adjacent gap sensors disposed opposite the pair of axially adjacent gap sensors, and piston skirt profiles previously acquired and stored by the two pairs of gap sensors; The two pairs of gap sensors to be used are switched sequentially depending on the crank angle, and the piston skirt profile is switched sequentially depending on the crank angle and the moving direction of the piston.

4. The piston behavior analysis device according to claim 3.

5. a detecting step of detecting a distance between the piston and the inner surface of the cylinder of the engine using a plurality of gap sensors arranged side by side at predetermined intervals along the axial direction on the inner surface of the cylinder of the engine; an analysis step of determining piston behavior including piston inclination based on the distance to the piston detected in the detection step and piston skirt profiles previously acquired and stored for each of the plurality of gap sensors, In the analysis step, the gap sensor and piston skirt profile to be used are switched depending on the crank angle, and the piston skirt profile is used to correct the distance to the piston detected by the gap sensor, and the piston behavior including piston inclination is determined based on the corrected distance to the piston.

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