DE102020128498B4 - Method for measuring the inside diameter of a large cylinder liner - Google Patents

Abstract

Method for measuring the inside diameter of a large cylinder liner (3), the cylinder liner (3) having at least one purge air slot (4), a pipe wall (6) and a piston (2) as well as a cylinder head gasket and the piston (2) between a lower turning point (8) and an upper turning point (7) can be moved by means of a device (1) comprising a housing (10), a base (13) and a sensor aligned with a tube wall (6) of the cylinder liner (3), the housing (10) is rotatably mounted about an axis of rotation on the base (13), the sensor being a non-contact rangefinder (11) which is aligned essentially perpendicular to the axis of rotation of the housing (10), the device (1) for measuring the inner diameter of the large cylinder liner (3) is placed on the piston (2) through a purge air slot (4), comprising the method steps - placing the device (1) approximately centrally on the piston (2), - moving the device (1) in a rotational movement and the beginning of the determination of measurement data through non-contact measurement between the device (1) and the pipe wall (6), - moving the piston (2) in the direction of the upper turning point (7) during the continuously continued, non-contact measurement of the distance between the device ( 1) and pipe wall (6), - after reaching the upper turning point (7), moving the piston (2) to the position at the lower turning point (8), - ending the measuring process, - removing the device (1) from the cylinder liner (3 ),- mathematical determination of the center of gravity from the measurement data and- calculation of the diameter of the cylinder liner (3) for different measuring planes (5) in the cylinder liner (3).

Description

The present invention relates to a method for measuring the inside diameter of a large cylinder liner of an engine, such as that used in ships. The cylinder liner must be measured regularly in order to detect damage and deformation in good time, particularly as a result of high temperatures. In this way, you can warn before serious damage occurs.

Presentation of the invention

According to the state of the art, the inside diameters of large cylinder liners are measured using an inside micrometer. To do this, the cylinder head must be dismantled in advance. This becomes more and more time-consuming as the size of the cylinder liner increases. In addition, the mass increases, so that complex devices for lifting the cylinder head from the cylinder liner are necessary. After dismantling, a person climbs onto the piston together with the internal micrometer and is brought into the position of a first measuring level by moving the piston using an electric motor, where the internal micrometer is used. All other levels specified by the design of the cylinder liner are then successively measured. Several parameters can negatively influence the measurement result. Errors often occur when handling the measuring device. In particular, the exact alignment of the device to the liner wall requires great precision, without which measurement errors occur. The very hot and very narrow environment doesn't make working any easier. After measuring the last inside diameter, the cylinder head is reassembled. Many wearing parts have to be replaced due to dismantling, so the costs of this type of testing skyrocket.

Newer processes do not require dismantling the cylinder head. This includes a procedure that is in Scripture WO 2009/152 851 A1 is described. This procedure involves positioning a measuring device on the piston. A complex substructure is required for positioning, which allows the device to be positioned centrally in the barrel bushing. The measuring device mounted on the substructure rotates around its own axis. The measuring device has a measuring arm at the end of which there is a touch sensor, which is regularly placed on the wall of the cylinder liner at predetermined positions. After a measurement, the touch sensor is retracted again. Position by position is approached until all measurements are completed. Operation takes place during the measuring process via a smartphone or a comparable device. For operation, the air intake valve at the upper end of the cylinder liner must be removed. A radio interface is hung in the resulting opening, which enables communication between the measuring device and the smartphone during the measuring process. The measuring method is therefore not completely disassembly-free and is associated with corresponding costs. The use of the touch sensor leads to a certain degree of uncertainty in the measurement results, since selective adhesions on the wall of the cylinder liner or adhesions picked up there on the button can falsify the result without knowledge during the measuring process.

The invention is therefore based on the object of measuring the inside diameter of the cylinder liner without dismantling components of the engine, whereby the method of measuring by means of sensors placed on the wall should be avoided. Furthermore, the invention is based on the object of providing a method according to which exact measured values for the inner diameter can be achieved from the determined data without the precise positioning of the device.

The problem is solved with the features of claim 1, with subclaims 2 to 7 describing further refinements.

According to the prior art, a device for measuring the inside diameter of a large cylinder liner comprises a housing, a base and a sensor, the housing being rotatably mounted on the base about an axis of rotation. The sensor is a non-contact range finder, which is aligned essentially perpendicular to the axis of rotation of the housing. This avoids the circumstance that measurements falsify the values due to buildup on the wall of the cylinder liner or even on the button. Furthermore, by means of a non-contact measurement, it can be achieved that the sensor system can be arranged in a comparatively small housing and easier handling is achieved by foregoing sensing devices whose length corresponds at least to the diameter of the cylinder liner.

A laser sensor is preferably used. These sensors can be used with high precision even under difficult conditions such as temperature and darkness. The reliability of the measured values is high, and the possibility of measuring a very large number of values within a very short time is an increase in accuracy.

The device can have a camera with which recordings can be made continuously during the measuring process, but also individually when damage or deformation of the cylinder liner is detected. To improve weight distribution on the rotating device, the camera is preferably aligned opposite to the working direction of the sensor. However, camera recordings and sensor readings can be mathematically linked to one another at any time.

The camera can be assigned a lighting device for illuminating the pipe wall. Although camera optics with appropriate technology can also be used for use in dark or poorly lit locations, the use of a lighting device allows the use of a conventional camera.

The device can have coupling means for a tool for insertion into the cylinder liner. Particularly in the case of cylinder liners with a very large diameter, inserting the device into the center of the piston is greatly simplified by using a tool that is attached to the coupling means. When inserting the device through a purge air slot, it may be necessary to stand the device upright in order to be able to insert it through the slot into the cylinder liner, which is why a coupling that allows it to slip off the tool is preferable.

The coupling means can be a metal element that can be coupled to an electromagnet. This also facilitates positioning approximately in the middle of the piston, since the device can be coupled to a tool using the electromagnet and can be set down at the push of a button when the rough location in the cylinder liner is reached.

The device can have a sensor for detecting the speed of the device. In particular, when continuously measuring the distance between the device and the wall of the cylinder liner, it must be determined at the appropriate time when the device has completed rotation about its own axis in order to be able to determine the diameter of the cylinder liner from the values measured during this rotation. The sensor that determines the speed takes this circumstance into account efficiently and accurately, especially if the completion of the revolution is also recorded, so that in post-processing each passage through such a point, which can be referred to as the zero point, can be clearly identified.

The device can have a storage medium. In order to make the device more independent during the measuring process and to free it from external interference with the measuring process, e.g. due to cables or additional weight of the device for radio data connection devices, a faster measurement can be achieved by storing the measurement data as well as photos , even if the relevant data has to be filtered out of the measurement results in post-processing.

Finally, the device can have an independent power supply. With an independent power supply, which can be in the form of a battery, for example, although commercially available batteries are not excluded, completely autonomous handling is possible, so that for the measuring process the user only has to roughly insert the device into the cylinder socket in order to adjust it at the end of the measurement.

For the method of measuring the inside diameter of a large cylinder liner using a previously described device, the device is placed on the piston through a purge air slot in the lower region of a cylinder liner, as is the case with other measuring methods according to the prior art. Unlike conventional methods, however, it is sufficient to place the device approximately in the middle of the piston; precise positioning in the center of the cylinder liner is not necessary. The device is then set in rotation and the determination of measurement data begins through non-contact measurement between the device and the pipe wall. The piston is then moved in the direction of the upper turning point, with the non-contact measurement of the distance between the device and the pipe wall being continued continuously during the process. After reaching the upper turning point, the piston is returned to the position at the lower turning point drive before the device can be removed from the cylinder liner after the measuring process has been completed. The center of gravity is mathematically determined from the measurement data, so that the calculation of the diameter of the cylinder liner for different heights of the piston in the cylinder liner can be determined from this mathematical displacement of the device into the longitudinal axis of the cylinder liner. The mathematical determination of the diameters required for testing purposes can in any case be described as faster and more accurate than can be derived directly from mechanically centered measuring devices or manually operated measuring devices. By making a very large number of measurements over the entire diameter and over all heights, the measurement also has a certain degree of robustness, since point deformations can be recorded and an incorrect or influenced size that is accidentally determined does not lead to an incorrect decision about the overall condition of the cylinder liner.

According to an improved embodiment of the method according to the invention for measuring the inside diameter of a large cylinder liner, the measured data determined are stored on a storage medium and read out from the cylinder liner after the measurement has been completed and the device has been removed. In this way, a lot of data can be determined, and the storage allows the collection of significantly larger amounts of data than would be possible, for example, if the data were passed on after collection via a radio connection or something similar.

Furthermore, according to a special embodiment of the method according to the invention for measuring the inside diameter of a large cylinder liner, it is provided that the measurement is carried out both on the way from the lower turning point to the upper turning point and back. Recording measured values twice increases the quality and improves the robustness of the measured values. Statistical methods can be used to filter implausible measured values from the determined data.

According to a special embodiment of the method according to the invention for measuring the inside diameter of a large cylinder liner, the height of the piston in the cylinder liner is also measured. This can be done optically but also using mechanical means. By determining the height of the piston within the cylinder liner, it is possible to assign the measured values to specified target measurement levels within the cylinder liner.

According to a special embodiment of the method according to the invention for measuring the inside diameter of a large cylinder liner, the piston is stopped at a height during the movement between the lower turning point and the upper turning point and / or back at predetermined heights for measurement. Since the device would theoretically only generate measured values in a spiral shape with a continuous movement of the piston in the cylinder liner, it may seem sensible to specifically approach the heights determined by the test scenarios for the respective cylinder liner, stop them and then measure a clean circle at least once. The accuracy of the measurement results can be further increased.

According to a further special embodiment of the method for measuring the inside diameter of a large cylinder liner, camera recordings of the pipe wall are also carried out in addition to measuring the inside diameter of the cylinder liner. Particularly when determining unwanted deformation of the wall of a cylinder liner, it can also be helpful to also look at the areas of the cylinder liner in question. Taking appropriate photographs serves to increase the level of certainty when making statements about the quality of the cylinder liner.

Finally, for the method for measuring the inside diameter of a large cylinder liner, a further special embodiment provides that the mathematical determination of the center of area is carried out using a center of area method or a frequency or order analysis.

$$\text{schwepunkt}\_\text{y}=\text{sum}\left(\text{sek}\_\text{flaeche}.*\text{ys}\right)/\text{sum}\left(\text{sek}\_\text{flaeche}\right);$$

In einem letzten Rechenschritt werden die gemessenen Abstandswerte nun auf den Gesamtflächenschwerpunkt umgerechnet, wobei die Messwerte mit der ermittelten Aussermittigkeit des Teilflächenschwerpunktes gegenüber dem Gesamtflächenschwerpunkt verknüpft werden. Auf ähnliche Weise erfolgen vergleichbare Verfahren, wie z.B. das Linienschwerpunktverfahren.A completely central placement of the measuring device within the cylinder cannot be ensured by inserting it through a flushing slot if complex positioning using mechanical means is to be avoided. This means that the distance measurements are not carried out at the center of gravity of the cylinder liner. This means that the addition of the opposing distance values does not indicate the diameter, but rather a chord. Using the center of gravity method, the measured distance values are recalculated or corrected to the center of gravity of the measured object, so that the addition of opposing distance values results in the diameter.
The mathematical process takes place in three steps. First, the entire area is broken down into partial areas or circular sectors, for which the partial area centroids Xs(1...n) and Ys(1...n) and areas are calculated. From this, the total center of gravity is calculated in a second step using the following formulas: $$\text{focus}\_\text{x}=\text{sum}\left(\text{sec}\_\text{area}.*\text{xs}\right)/\text{sum}\left(\text{sec}\_\text{area}\right);$$

$$\text{focus}\_\text{y}=\text{sum}\left(\text{sec}\_\text{area}.*\text{ys}\right)/\text{sum}\left(\text{sec}\_\text{area}\right);$$

In a final calculation step, the measured distance values are now converted to the overall center of gravity, whereby the measured values are linked to the determined eccentricity of the partial center of gravity compared to the overall center of gravity. Comparable methods, such as the line centroid method, are carried out in a similar manner.

Implementation of the invention

• 1 Eine Schnittdarstellung einer Zylinderlaufbuchse mit eingesetzter Vorrichtung,
• 2 eine Seitenansicht der Vorrichtung im Innern einer Zylinderlaufbuchse,
• 3 eine schematische Darstellung des Aufbaus der Vorrichtung in einer Draufsicht und
• 4 eine schematische Darstellung des Flächenschwerpunktverfahrens.

The invention is explained using an exemplary embodiment. Show this

• 1 A sectional view of a cylinder liner with the device inserted,
• 2 a side view of the device inside a cylinder liner,
• 3 a schematic representation of the structure of the device in a top view and
• 4 a schematic representation of the center of area method.

In 1 A large cylinder liner 3 of a ship's engine is shown in section, with the illustration of a cylinder head gasket at its upper end being omitted. On its inside, the cylinder liner 3 has a pipe wall 6 that is to be checked to provide a statement about the quality of the cylinder liner 3. In the figure, a piston 2 is shown in the lower area, which moves back and forth between a lower turning point 8 and an upper turning point 7 during operation of the ship's engine. In addition, a ring of purge air slots 4 is shown, which are distributed around the circumference of the cylinder liner 3. Through such a purge air slot 4, a device 1 according to the invention can be inserted and placed on the piston 2, with a largely central arrangement on the piston 2 making sense. Precise mechanical centering can be omitted according to the method according to the invention. To determine the measurement data, the piston 2 with the device 1 sitting on it is moved from the lower turning point 8 to the upper turning point 7. The movement of the piston 2 can be stopped at the level of the measuring planes 5 specified by the manufacturer of the cylinder liner for a measurement with the device 1.

2 shows a device 1 according to the invention, which is inserted into a cylinder liner 3. It rests with its base 13 on the piston 2. The housing 10 is rotatably mounted on the base 13 so that it can rotate about the vertical axis through the device 1 during the measuring process. A distance meter 11 is arranged on one side of the housing 10 and uses a laser beam 12 to scan the tube wall of the cylinder liner 3 without contact. Opposite the rangefinder 11, a camera 14 is arranged in the housing 10, with which photos of the wall of the cylinder liner 3 can be taken.

Furthermore, in 3 a top view of the schematic structure of the device is shown. The device 1 has a housing 10. A camera 14 is arranged next to a lighting device 15 on one side of the housing. Images recorded with the camera 14 can be sufficiently illuminated by the lighting device 15. Opposite this device, the rangefinder 11 is shown, next to which a coupling means 16 is arranged, via which the device 1 can be inserted into a cylinder liner, but can also be removed again. A motor 19 is arranged inside the housing 10, which, due to its location approximately in the center of gravity of the housing 10 and in the axis of rotation of the base 13 arranged below the housing 10, ensures an optimal rotational movement of the housing 10 with a high level of smooth running for good measurement results. A speed sensor 17 detects every full revolution of the housing 10 around the axis of rotation. Furthermore, a control unit 18 is arranged in the housing 10, which on the one hand controls the data acquisition using the range finder 11 and camera 14, but also regulates the data storage on the storage medium 20. All components that require a power supply are supplied with power by the power supply 21.

Finally it's in 4 a schematic representation of the center of area method is shown, where 4a) shows the position of the device and its measured values as well as the partial area centroids derived therefrom and 4b) shows the mathematical shift in the overall area centroid. After inserting the device 1 into the cylinder liner 3 on the piston 2, the device 1 carries out measurements 30 on the pipe wall 6. A partial area 35 can be formed from two adjacent measurements 30 and the partial section of the cylinder liner 3, which has a partial area center of gravity 31. From two measurements 30 each, a large number of partial area centroids 31 can be derived, which are used for further calculation. From the large number of partial area centers of gravity 31, an overall area center of gravity 32 can be determined, which should lie in the longitudinal axis of the cylinder liner 3. This is at a distance 33 from the location of the device when measured. From the total center of gravity 32, the pipe wall distances 34 that are now adapted to the total center of gravity 32 can be determined, with opposite pairs of pipe wall distances 34 always forming a diameter of the cylinder liner 3.

Reference symbol list

1

contraption

2

Pistons

3

Cylinder liner

4

Purge air slot

5

Measurement levels

6

pipe wall

7

upper turning point

8th

lower turning point

10

Housing

11

Rangefinder

12

laser beam

13

Stand

14

camera

15

Lighting device

16

coupling agent

17

Speed sensor

18

Control unit

19

engine

20

storage medium

21

Power supply

30

Measured value

31

Partial area centroid

32

Total area center of gravity

33

Distance

34

Pipe wall distance

35

partial area

Claims (7)

Method for measuring the inside diameter of a large cylinder liner (3), the cylinder liner (3) having at least one purge air slot (4), a pipe wall (6) and a piston (2) as well as a cylinder head gasket and the piston (2) between a lower turning point (8) and an upper turning point (7) can be moved by means of a device (1) comprising a housing (10), a base (13) and a sensor aligned with a tube wall (6) of the cylinder liner (3), the housing (10) being rotatable is mounted on the base (13) about an axis of rotation, the sensor being a non-contact rangefinder (11) which is aligned essentially perpendicular to the axis of rotation of the housing (10), the device (1) for measuring the inside diameter of the large Cylinder liner (3) is placed on the piston (2) through a purge air slot (4), comprising the method steps - placing the device (1) approximately centrally on the piston (2), - setting the device (1) in a rotational movement and Beginning of the determination of measurement data through non-contact measurement between the device (1) and the pipe wall (6), - moving the piston (2) in the direction of the upper turning point (7) during the continuously continued, non-contact measurement of the distance between the device (1) and the pipe wall (6), - after reaching the upper turning point (7) moving the piston (2) to the position at the lower turning point (8), - termination of the measuring process, - removal of the device (1) from the cylinder liner (3), - mathematical Determination of the center of gravity from the measurement data and calculation of the diameter of the cylinder liner (3) for different measuring planes (5) in the cylinder liner (3). Method for measuring the inside diameter of a large cylinder liner (3). Claim 1 , characterized in that the determined measurement data are stored on a storage medium (20) and are read out from the cylinder liner (3) after the measurement has been completed and the device (1) has been removed. Method for measuring the inside diameter of a large cylinder liner (3) according to one of the preceding claims, characterized in that the measurement is carried out both on the way from the lower turning point (8) to the upper turning point (7) and back. Method for measuring the inside diameter of a large cylinder liner (3) according to one of the preceding claims, characterized in that the height of the piston (2) in the cylinder liner (3) is also measured. Method for measuring the inside diameter of a large cylinder liner (3) according to one of the preceding claims, characterized in that the piston (2) when moving between the lower turning point (8) and the upper turning point (7) and / or back in predetermined measuring planes ( 5) is stopped at a height for measurement. Method for measuring the inside diameter of a large cylinder liner (3) according to one of the preceding claims, characterized in that, in addition to measuring the inside diameter of the cylinder liner (3), camera images of the pipe wall (6) are also taken. Method for measuring the inside diameter of a large cylinder liner (3) according to one of the preceding claims, characterized in that the mathematical determination of the center of area is carried out using a center of area method or a frequency or order analysis.

Images