System and method for estimating roundness of cylinder bore

Abstract

To accurately estimate circularity of a cylinder bore.SOLUTION: An estimation system 1 includes a rotating shaft 3 rotating in a cylinder bore 11, wherein length measuring sensors 36A, 36B for measuring separation distances α, β from a facing inner peripheral surface 11a of the cylinder bore 11 are disposed at two positions opposed by 180° to each other across a center axis Os thereof. Every time the rotating shaft 3 rotates by a prescribed angle, a deviation amount δ1 of the center axis Os of the rotating shaft 3 with respect to a center axis Ob of the cylinder bore 11 is calculated on the basis of the separation distances α, β respectively calculated by the two length measuring sensors 36A, 36B, and a radius value of the cylinder bore 11 calculated on the basis of the separation distance α is corrected by the deviation amount δ1.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a system and method for estimating the roundness (cross-sectional shape) of a cylinder bore formed in a cylinder block of an engine. [Background technology]

[0002] As is well known, in a reciprocating engine, a piston disposed in a cylinder bore of a cylinder block reciprocates between top dead center and bottom dead center, and the intake, compression, expansion (combustion), and exhaust strokes are repeatedly performed, thereby continuously outputting rotational power. A piston ring such as an O-ring is fitted to the outer circumferential surface of the piston, and this piston ring slides on the inner circumferential surface of the cylinder bore as the piston reciprocates. If the cylinder bore is out of round, the sliding resistance of the piston ring against the cylinder bore (engine mechanical loss) increases, and the output efficiency of the engine decreases. For this reason, efforts are being made to measure the roundness of the cylinder bore and reflect the results in the design and processing (manufacturing) of the engine.

[0003] Japanese Patent Application Laid-Open Publication No. 2015-197296 (Patent Document 1) describes a system for measuring the roundness of a cylinder bore (its inner peripheral surface). This system is characterized in that it is possible to measure and calculate the roundness of a cylinder bore while heating the cylinder head and cylinder block from the combustion chamber and inside the cylinder bore, respectively, that is, it is possible to measure the roundness of a cylinder bore while keeping the temperature of the cylinder block close to the actual operating condition of an engine. This makes it possible to estimate the roundness of a cylinder bore in an operating engine, and to obtain data useful for engine design, etc.

[0004] In the above system, a rotating shaft that rotates around its central axis is coaxially arranged on the inner circumference of the cylinder bore, and a (single) gap sensor attached to the rotating shaft detects a radial gap formed between the outer circumferential surfaces of the opposing rotating shafts and the inner circumferential surface of the cylinder bore.Then, a control device obtains a detection value (gap value) by the gap sensor every time the rotating shaft rotates a predetermined angle (e.g., 5°), and calculates the roundness of the cylinder bore based on a plurality of gap values ​​(e.g., a total of 72 gap values ​​obtained during one rotation of the rotating shaft). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-197296 A Summary of the Invention [Problem to be solved by the invention]

[0006] The inventors obtained multiple gap values ​​using the technical means described in Patent Document 1 and created graphic data regarding the cross-sectional shape of the cylinder bore based on this. The graphic data obtained had large irregularities that could not actually exist, and there was a significant difference in shape between this and graphic data regarding the cross-sectional shape of the cylinder bore at room temperature, which was created for reference using a roundness measuring device.

[0007] It is speculated that the main reason why large irregularities (shape distortion) occurred in the graphic data created using the technical means of Patent Document 1 is that axial vibration occurs when the rotating member to which the gap sensor is attached is rotated, and the amount of vibration is reflected in the detection value by the gap sensor. Therefore, it can be said that the technical means described in Patent Document 1 is prone to large measurement errors, and there is a high possibility that it is not possible to appropriately obtain highly reliable data that can be effectively used for engine design, etc., and there is room for improvement.

[0008] In view of the above circumstances, an object of the present invention is to enable accurate estimation of the roundness (cross-sectional shape) of a cylinder bore formed in a cylinder block of an engine. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the present invention provides a system for estimating the roundness of a cylinder bore formed in a cylinder block, comprising a rotating shaft that rotates around its central axis within the cylinder bore, and a length measuring sensor attached to the rotating shaft and measuring the distance between the rotating shaft and the inner surface of the opposing cylinder bore, the length measuring sensors being arranged at least in two locations that are 180° opposed to each other on either side of the central axis of the rotating shaft, and each time the rotating shaft rotates a predetermined amount, the amount of deviation of the central axis of the rotating shaft from the central axis of the cylinder bore is calculated based on the distances measured by each length measuring sensor, and the radius value of the cylinder bore calculated based on the distances is corrected by this amount of deviation.

[0010] According to the above configuration, the deviation of the central axis of the rotating shaft from the central axis of the cylinder bore when the rotating shaft rotates a predetermined amount (the runout of the rotating shaft) can be calculated based on the measurement values ​​of the length measuring sensors arranged at two locations opposite to each other by 180° with respect to the central axis of the rotating shaft. This makes it possible to reduce the influence of the axial runout of the rotating shaft when calculating the inner diameter of the cylinder bore at each rotation angle. In addition, the radius value (inner diameter dimension) of the cylinder bore calculated based on the separation distance measured by the length measuring sensor is corrected by the deviation amount, thereby improving the accuracy (reliability) of the inner diameter dimension of the cylinder bore to be calculated at each rotation angle. In the present invention, the deviation calculation process and correction process are performed every time the rotating shaft rotates a predetermined amount, in other words every time the inner diameter dimension of the cylinder bore is calculated, so that the roundness (cross-sectional shape) of the cylinder bore can be estimated with high accuracy.

[0011] Two length measuring sensors can be attached to the rotation axis at a 180° pitch as described above, or four can be attached at a 90° pitch.

[0012] In addition, in order to achieve the above-mentioned object, the present invention provides a method for estimating the roundness of a cylinder bore formed in a cylinder block, characterized in that, when estimating the roundness of a cylinder bore formed in a cylinder block, length measuring sensors are attached to at least two locations of a rotating shaft that rotates around its central axis within the cylinder bore, which are opposed by 180° about the central axis, to measure the distance between the inner surface of the opposing cylinder bore, and each time the rotating shaft rotates a predetermined amount, a correction process is performed to correct the radius of the cylinder bore calculated based on the distance measured by each length measuring sensor, using the amount of deviation of the central axis of the rotating shaft from the central axis of the cylinder bore calculated based on the distances measured by each length measuring sensor.

[0013] This method also provides the same effects as the system according to the present invention described above. Effect of the Invention

[0014] As described above, according to the present invention, it is possible to accurately estimate the roundness (cross-sectional shape) of a cylinder bore provided in a cylinder block. [Brief description of the drawings]

[0015] [Figure 1] 1 is a diagram showing an overall schematic structure of a cylinder bore roundness estimation system according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a partially enlarged view of FIG. [Diagram 3] 2 is a block diagram showing an electrical connection state in the system shown in FIG. 1. [Figure 4] FIG. 3 is a schematic cross-sectional view taken along line AA in FIG. 2. [Diagram 5] FIG. 4 is a cross-sectional view showing a state in which a rotating shaft is eccentric with respect to a cylinder bore. [Figure 6] 11 is a diagram based on the measurement values ​​of a length measuring sensor. [Figure 7] 1 is a partial cross-sectional view of a system according to another embodiment of the present invention. [Figure 8]FIG. 11 is a cross-sectional view showing a state in which a rotating shaft is eccentric with respect to a cylinder bore in another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] FIG. 1 shows an overall schematic structure of an estimation system 1 according to an embodiment of the present invention, and FIG. 2 shows a partially enlarged view of the estimation system 1. The estimation system 1 shown in FIG. 1 etc. is a system used for estimating the roundness (cross-sectional shape) of a cylinder bore 11 formed in a cylinder block 10 of an engine. A cylinder head 12 is attached to the cylinder block 10. The cylinder head 12 has a combustion chamber 13 communicating with the cylinder bore 11, an intake port 14 and an exhaust port 15 communicating with the combustion chamber 13, and a plug housing chamber 16 for housing an ignition plug. The cylinder block 10 and the cylinder head 12 are formed with water jackets 17 and 18, respectively. Both the cylinder block 10 and the cylinder head 12 are made of cast iron or an aluminum alloy.

[0018] The estimation system 1 comprises a base 2A that fixedly holds a cylinder block 10 via a jig not shown, a bracket 2B that is movable up and down relative to the base 2A, a rotating shaft 3 that is rotatably supported on the bracket 2B, a rotational drive unit 4 that rotates the rotating shaft 3 around its central axis, and a control unit 5 (see Figure 3) that controls the operation of the rotational drive unit 4 and the like.

[0019] The cylinder block 10 is supported by the base 2A so that the crankcase side is disposed on the lower side and the central axes of the cylinder bores 11 are disposed along the vertical direction.

[0020] A high-temperature fluid supply unit 20 is connected to the cylinder block 10 held on the base 2A with the cylinder head 12 attached thereto, for supplying a fluid (e.g., oil) having a temperature higher than room temperature to the combustion chamber 13 (and the cylinder bore 11 communicating therewith) formed in the cylinder head 12. That is, the estimation system 1 of this embodiment further includes the high-temperature fluid supply unit 20. The high-temperature fluid supply unit 20 includes, for example, an oil tank (not shown) that stores oil, an oil pump 21 that pumps out the oil (high-temperature oil) stored in the oil tank, an oil supply pipe 22 having one end connected to a discharge port of the oil pump 21, and an oil drain pipe 23 having one end connected to a suction port of the oil pump 21. The high-temperature fluid supply unit 20 having such a configuration is electrically connected to the control unit 5, as shown in FIG. 3.

[0021] In this embodiment, the other end of the oil supply pipe 22 is connected to the plug accommodating chamber 16, the other end of the oil drain pipe 23 is connected to the exhaust port 15, and the intake port 14 is closed by a lid material (not shown). Therefore, high-temperature oil discharged from the oil pump 21 flows into the combustion chamber 13 and further into the cylinder bore 11 via the oil supply pipe 22 and the plug accommodating chamber 16, and the high-temperature oil that flows into the cylinder bore 11 flows back to the oil tank via the combustion chamber 13, the exhaust port 15, and the oil drain pipe 23. By circulating the high-temperature oil in the above manner, the cylinder bore 11 of the cylinder block 10 can be heated to a temperature higher than room temperature (a temperature corresponding to the oil temperature of the high-temperature oil).

[0022] The rotating shaft 3 is supported by the bracket 2B via bearings 6 in a vertical position (upright position) arranged coaxially with the cylinder bore 11, and includes a shaft portion 31 whose lower end is connected to the rotation drive portion 4, and a head portion 32 provided at the upper end of the shaft portion 31. The rotating shaft 3 is made of a material having a smaller linear expansion coefficient than the material from which the cylinder block 10 is made.

[0023] As shown in the enlarged view of FIG. 2, the head 32 has a cylindrical outer peripheral surface 33, which faces the inner peripheral surface 11a of the cylinder bore 11, which is formed in a cylindrical shape, with a radial gap 7 therebetween. An annular groove 34 is formed at the upper end of the outer peripheral surface 33 of the head 32, and an O-ring 35 pressed against the inner peripheral surface 11a of the cylinder bore 11 is fitted into the annular groove 34. Therefore, when the rotating shaft 3 rotates by receiving the output of the rotation drive unit 4, and when the rotating shaft 3 moves up and down with the upward and downward movement of the bracket 2B, the O-ring 35 slides on the inner peripheral surface 11a of the cylinder bore 11. In addition, since the O-ring 35 is provided in this manner, the space defined between the rotating shaft 3 and the cylinder bore 11 is sealed, so that the high-temperature oil supplied to the cylinder bore 11 can be prevented from leaking out. This allows the cylinder block 10 to be appropriately heated from within the cylinder bore 11.

[0024] As shown in FIG. 4, a length measuring sensor 36 capable of measuring the radial distance between the head 32 of the rotating shaft 3 and the inner peripheral surface 11a of the opposing cylinder bore 11 is attached below the annular groove 34. An even number of length measuring sensors 36 are attached to the head 32 at equal intervals in the circumferential direction, and in this embodiment, they are attached to two locations that are 180° opposed to each other across the central axis (center of rotation) Os of the rotating shaft 3. Each length measuring sensor 36 is electrically connected to the control unit 5 (see FIG. 3). The length measuring sensor 36 is also called a displacement sensor or gap sensor, and non-contact types such as laser type, LED type, ultrasonic type, and eddy current type are preferably used. In the following, when it is necessary to distinguish between the two length measuring sensors 36 attached to the head 32, one is called the first length measuring sensor 36A and the other is called the second length measuring sensor 36B.

[0025] The rotation drive unit 4 includes a motor 41 that generates rotational power for rotating the rotating shaft 3, a drive gear 42 provided on the output shaft of the motor 41, a passive gear 43 provided on the lower end of the shaft portion 31 of the rotating shaft 3 and meshing with the drive gear 42, a rotary encoder 44 as a rotation angle detection sensor, and an encoder gear 45 provided on the rotating shaft of the rotary encoder 44 and meshing with the passive gear 43. The rotation drive unit 4 having the above configuration is held by the bracket 2B, and moves up and down together with the rotating shaft 3.

[0026] The rotary drive unit 4 is electrically connected to the control unit 5, and the operation of the motor 41 is controlled by the control unit 5. When the motor 41 is driven and its output shaft and the drive gear 42 rotate together, the passive gear 43 meshed with the drive gear 42 and the rotating shaft 3 on which the passive gear 43 is provided rotate together. When the passive gear 43 rotates, the encoder gear 45 meshed therewith and the rotating shaft of the rotary encoder 44 on which the encoder gear 45 is provided also rotate. A signal (pulse signal) is output from the rotary encoder 44 every time the rotating shaft of the rotary encoder 44 rotates a predetermined angle, and this pulse signal is input to the control unit 5. It is also possible to use, as the motor 41, a servo motor in which, for example, a rotation detection sensor is integrally provided. In this case, it is not necessary to separately install the motor 41 and the rotary encoder 44 as in the illustrated example.

[0027] The roundness estimation system 1 of this embodiment has roughly the above-mentioned configuration, and measures and estimates the roundness of the cylinder bore 11 by following the procedure below.

[0028] First, as shown in Figures 1 and 2, the cylinder block 10 to which the cylinder head 12 is attached is held on the base 2A, and the bracket 2B supporting the rotating shaft 3 and the rotation drive unit 4 is raised and lowered to vertically position the head 32 of the rotating shaft 3 (the length measuring sensor 36 attached thereto) relative to the cylinder bore 11 formed in the cylinder block 10.

[0029] Next, the control unit 5 controls the high-temperature fluid supply unit 20 to supply high-temperature oil to the cylinder block 10 to which the cylinder head 12 is attached. When high-temperature oil is supplied, a temperature sensor (not shown) arranged around the cylinder bore 11 detects the temperature near the inner circumferential surface 11a of the cylinder bore 11, and the detected value is sent to the control unit 5. The control unit 5 issues a command to the high-temperature fluid supply unit 20 to adjust the oil temperature based on the detection value sent from the temperature sensor so that the temperature of the inner circumferential surface 11a of the cylinder bore 11 falls within a predetermined temperature range. Then, for example, when the control unit 5 determines that the temperature detected by the temperature sensor falls within the predetermined range, the motor 41 of the rotation drive unit 4 is driven to rotate the rotating shaft 3 around its central axis Os, and the two length measurement sensors 36 (first length measurement sensor 36A and second length measurement sensor 36B) attached to the head 32 of the rotating shaft 3 measure the separation distances α, β (see FIG. 4) between the inner circumferential surface 11a of the opposing cylinder bore 11.

[0030] More specifically, when the motor 41 of the rotation drive unit 4 is driven, the control unit 5 rotates the rotating shaft 3 stepwise by a predetermined angle (for example, 5°) based on a pulse signal input from the rotary encoder 44. Every time the rotating shaft 3 rotates by a predetermined angle, the control unit 5 acquires a detection signal of the first length measuring sensor 36A, i.e., a signal related to a measurement value (separation distance α: see FIG. 4) measured by the first length measuring sensor 36A, and a detection signal of the second length measuring sensor 36B, i.e., a signal related to a measurement value (separation distance β: see FIG. 4) measured by the second length measuring sensor 36B. Then, while the rotating shaft 3 rotates once, a plurality of detection signals (72 in this example) are acquired from each of the length measuring sensors 36A and 36B.

[0031] In Figure 6, where the horizontal axis represents the rotation angle of the rotating shaft 3 and the vertical axis represents the above-mentioned separation distance measured by the length measuring sensor 36, a thin solid line represents a diagram based on the measurement value (separation distance α) measured by the first length measuring sensor 36A while the rotating shaft 3 makes one rotation, and a dashed line represents a diagram based on the measurement value (separation distance β) measured by the second length measuring sensor 36B while the rotating shaft 3 makes one rotation.

[0032] In both of the two graphs shown by the thin solid line and the dashed line in Fig. 6, the measurement values ​​by each length measuring sensor 36 differ greatly depending on the rotation angle of the rotating shaft 3. This means that the roundness of the inner peripheral surface 11a of the cylinder bore 11 is (very) low, but even if the inner peripheral surface 11a of the cylinder bore 11 is heated by high-temperature oil when the estimation system 1 is used, it is difficult to imagine that the inner peripheral surface 11a of the cylinder bore 11 is thermally deformed so greatly that the above two graphs wave greatly up and down (the roundness of the inner peripheral surface 11a is greatly reduced). Therefore, it is presumed that there is another factor that causes the measurement values ​​by each length measuring sensor 36 to differ greatly depending on the rotation angle of the rotating shaft 3.

[0033] Specifically, when the rotating shaft 3 is driven to rotate, the central axis Os of the rotating shaft 3 is radially displaced from the central axis Ob of the cylinder bore 11 (see FIG. 4), which is called axial runout, and it is believed that one of the major causes is that the radial movement amount due to the axial runout is reflected in the measurement value. It is considered that the axial runout can be suppressed, for example, by increasing the number of points where the rotating shaft 3 is supported by bearings, but due to the structure of the cylinder bore 11 formed in the cylinder block 10, it is not easy to take such measures.

[0034] Therefore, in the estimation system 1 according to the embodiment of the present invention, every time the rotating shaft 3 rotates a predetermined amount (predetermined angle), a deviation amount δ1 (see FIG. 5) of the central axis Os of the rotating shaft 3 relative to the central axis Ob of the cylinder bore 11 is calculated based on the distances α and β measured by each length measurement sensor 36 (36A, 36B), and the radius value of the cylinder bore 11 calculated based on the distance α (or β) is corrected by this deviation amount δ1. A specific procedure for this correction process will be described below with reference to FIG. 5.

[0035] [First step] First, the distance D between the center axis Os of the rotating shaft 3 (the center axis of the rotating shaft 3 at the axial position where the length measuring sensors 36A and 36B are attached; the same applies below in this paragraph) and the detection surface of the first length measuring sensor 36A SA , and the distance D between the central axis Os of the rotation shaft 3 and the detection surface of the second length measuring sensor 36BSB This measurement may be performed at the stage where the length measuring sensors 36A, 36B are attached to the head 32 of the rotating shaft 3. [Second step] After rotating the rotary shaft 3 by a predetermined angle (here, 5°), the distances α, β between the detection surfaces of the sensors and the inner circumferential surface 11a of the cylinder bore 11 at that rotation angle are measured by the length measuring sensors 36A, 36B. [Third Step] Measurement value D measured in the first and second steps SA ,D SB From α, β, the inner diameter dimension Db (=D SA +D SB +α+β). [Fourth step] The inner diameter dimension Db of the cylinder bore 11 based on the measurement value at that rotation angle, obtained in the third step, is divided in half (=Db / 2) to obtain the radial dimension of the cylinder bore 11 based on the measurement value at that rotation angle, in other words, the central axis Ob of the cylinder bore 11. [5th ​​step] The distance D measured in the first step SA ,D SB Based on this, the radius dimension of the rotation axis 3 (=(D SA +D SB From this radius dimension and the radius dimension of the cylinder bore 11 based on the measurement value at that rotation angle determined in the fourth step, the deviation δ1 between the central axis Os of the rotating shaft 3 and the central axis Ob of the cylinder bore 11 based on the measurement value at that rotation angle is determined. [Sixth Step] Distance D measured in the first step SA (or D SB ) and the distance α (or β) measured in the second step to obtain the radial dimension (=D SA +α) is corrected using the deviation δ1 obtained in the fifth step. Thereafter, the second to sixth steps are carried out in order each time the rotating shaft 3 rotates by a predetermined angle.

[0036] A diagram based on the values ​​corrected by following the above procedure is shown by the thick solid line in Figure 6. In this diagram, too, the "distance" value shown on the vertical axis varies depending on the rotation angle of the rotating shaft 3, but the difference between the maximum and minimum values ​​is considerably small. Therefore, it is considered that the diagram shown by the thick solid line in Figure 6 accurately reflects the cross-sectional shape of the inner circumferential surface 11a of the cylinder bore 11 (cylinder bore 11 heated to a temperature higher than room temperature).

[0037] After the rotating shaft 3 has been rotated once (after the roundness of the cylinder bore 11 at a predetermined vertical position has been determined), the bracket 2B supporting the rotating shaft 3 and the rotation drive unit 4 is raised and lowered to change the vertical position of the head 32 of the rotating shaft 3 relative to the cylinder bore 11. Then, at the new vertical position, the roundness of the inner circumferential surface 11a of the cylinder bore 11 is determined as described above.

[0038] In the roundness estimation system 1 according to the present embodiment described above, the deviation δ1 of the central axis Os of the rotating shaft 3 relative to the central axis Ob of the cylinder bore 11, i.e., the runout amount of the rotating shaft 3, is calculated based on the separation distances α and β measured by each of the length measurement sensors 36 (first length measurement sensor 36A and second length measurement sensor) arranged at two locations opposing each other by 180° across the central axis Os of the rotating shaft 3. This makes it possible to reduce the influence of the axial runout of the rotating shaft 3 when calculating the inner diameter dimension of the cylinder bore 11 at each rotation angle of the rotating shaft 3. Furthermore, the deviation δ1 is used to calculate the radius value (=D SA +α) is corrected, the accuracy and reliability of the inner diameter dimension of the cylinder bore 11 to be calculated at each rotation angle of the rotating shaft 3 is improved.

[0039] In particular, the system 1 of this embodiment has a high-temperature fluid supply unit 20 that supplies a fluid (high-temperature oil) that is hotter than room temperature to the cylinder block 10, and each time the rotating shaft 3 rotates a predetermined angle around the inner circumference of the cylinder bore 11 in a state where the high-temperature oil supplied to the cylinder bore 11 has heated the temperature to a temperature higher than room temperature, the deviation calculation process (steps 2 to 5 above) and the correction process (step 6 above) are performed, so that the roundness (cross-sectional shape) of the cylinder bore 11 in an operating engine can be accurately estimated.

[0040] Although the roundness estimation system 1 and the estimation method for the cylinder bore 11 according to one embodiment of the present invention have been described above, the embodiment of the present invention is not limited to the above-described one.

[0041] For example, as shown in Fig. 7, in addition to the first length measurement sensor 36A and the second length measurement sensor 36B arranged at two locations facing each other at 180° across the central axis Os of the head 32 of the rotating shaft 3, a third length measurement sensor 36C and a fourth length measurement sensor 36D may be attached at positions shifted 90° to one side and the other side in the circumferential direction from the first length measurement sensor 36A. In other words, four length measurement sensors 36 can be attached to the head 32 of the rotating shaft 3 at 90° intervals. Note that the third length measurement sensor 36C and the fourth length measurement sensor 36D are sensors that measure the distance from the inner circumferential surface 11a of the opposing cylinder bore 11, similar to the first length measurement sensor 36A.

[0042] According to this configuration, the deviation δ2 (see FIG. 8) of the central axis Ob of the rotating shaft 3 relative to the central axis Os of the cylinder bore 11 can be calculated based on the measurement values ​​(above-mentioned separation distance) by the third length measurement sensor 36C and the fourth length measurement sensor 36D, which are arranged at two locations that are 180° opposed to each other across the central axis Os of the rotating shaft 3. This deviation δ2 is a deviation in a direction perpendicular to the deviation δ1 calculated based on the measurement values ​​by the first length measurement sensor 36A and the second length measurement sensor 36B. Therefore, according to the configuration of this embodiment, when calculating the inner diameter dimension of the cylinder bore 11, the axial runout of the rotating shaft 3 in two mutually perpendicular directions can be taken into consideration. Therefore, the roundness (cross-sectional shape) of the inner peripheral surface 11a of the cylinder bore 11 can be estimated with even greater accuracy.

[0043] The estimation system 1 according to an embodiment of the present invention can be used not only to estimate the roundness of a cylinder bore 11 heated by high-temperature oil supplied from a high-temperature fluid supply section 20 (a cylinder bore 11 in a warm or hot state), but also to estimate the roundness of a cylinder bore 11 at room temperature (a cylinder bore 11 in a cold state). [Explanation of symbols]

[0044] 1. Estimation System 3 Rotation Axis 4 Rotation drive unit 5. Control section 10 Cylinder block 11 Cylinder bore 11a Inner surface 12. Cylinder head 20 High temperature fluid supply section 32 Head 36 Length measuring sensor Ob Cylinder bore axis Os Central axis of rotation α Separation distance β separation distance δ1 deviation amount

Claims

1. A system for estimating the roundness of a cylinder bore formed in a cylinder block, comprising: a rotating shaft that rotates about its central axis within the cylinder bore; a length measuring sensor attached to the rotating shaft and configured to measure a distance between the rotating shaft and an inner peripheral surface of the opposing cylinder bore; The length measuring sensors are disposed at least at two locations that are opposed to each other by 180° with respect to the central axis of the rotation shaft, Each time the rotating shaft rotates by a predetermined amount, a deviation of the central axis of the rotating shaft from the central axis of the cylinder bore is calculated based on the distances measured by each length measuring sensor, and the radius value of the cylinder bore calculated based on the distances is corrected by the deviation. A cylinder bore roundness estimation system characterized in that the central axis of the cylinder bore used to calculate the amount of deviation is obtained based on the distance between the detection surfaces of two length measuring sensors arranged to face each other at 180° on either side of the central axis of the rotation shaft and the central axis of the rotation shaft, and the distance measured by the two length measuring sensors.

2. 2. The cylinder bore roundness estimation system according to claim 1, wherein the length measuring sensors are equally spaced at four positions in a circumferential direction of the rotating shaft.

3. When estimating the roundness of a cylinder bore formed in a cylinder block, A length measuring sensor is attached to at least two locations of a rotating shaft that rotates around a central axis in the cylinder bore, the length measuring sensor measuring a distance between the rotating shaft and an inner peripheral surface of the cylinder bore, the rotating shaft being opposed to the central axis by 180°. a correction process is performed each time the rotating shaft rotates a predetermined amount, in which a radius value of the cylinder bore calculated based on the distances is corrected based on a deviation amount of the central axis of the rotating shaft from the central axis of the cylinder bore calculated based on the distances measured by each length measuring sensor; A method for estimating the roundness of a cylinder bore, characterized in that the central axis of the cylinder bore used to calculate the amount of deviation is obtained based on the distance between the detection surfaces of two length measuring sensors arranged to face each other at 180° on either side of the central axis of the rotation shaft and the central axis of the rotation shaft, and on the distance measured by the two length measuring sensors.

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