A positioning method for the top dead center of a ship's main engine piston

Abstract

A method for locating the top dead center of a piston during assembly of a ship's main engine is characterized by combining a laser rangefinder, a data processing device, a reference plate, and laser ranging technology. The method uses cranking and continuously detecting the distance from a fixed point in the scavenging air box to the piston head. The maximum detected value of this distance is screened out through data processing, and the position of the piston head corresponding to this maximum detected value is located as the top dead center of the ship's main engine piston. The method includes the following steps: 1. cranking the engine to the bottom dead center and installing a positioning device; 2. cranking the engine to start measuring the distance 10° before the top dead center, and stopping measuring the distance 5° after the top dead center, outputting the maximum detected value; 3. Measuring the distance and reversing the engine until the displayed value reaches the maximum detected value, and locating this point as the top dead center of the piston. The method achieves fast and accurate positioning, improves on-site operation efficiency, reduces the labor intensity of on-site operators, avoids deviations caused by manual operation, and improves the manufacturing quality of the main engine. The method has the advantages of being simple to use, easy to install, and highly versatile.

Description

Technical Field

[0001] The invention relates to a manufacturing process of a marine diesel engine, in particular to a positioning method for the top dead center of a ship main engine piston, and belongs to the technical field of diesel engine manufacturing. Background Art

[0002] In the early stages of ship main engine assembly, it is necessary to perform processes such as piston top dead center positioning and centering. Among them, piston top dead center positioning is an important step and basis for main engine assembly, commissioning and operation. The traditional method of piston top dead center positioning in the current assembly process is to mark the frame guide and flywheel during cranking. It does not use electronic equipment and is a mechanical manual positioning method. Specifically, the ship main engine is cranked to about 10° before the top dead center of cylinder 1#, and marks are made on the flywheel and frame guide. Then, the piston disc is cranked straight through the top dead center. When the slider runs to the frame guide mark, cranking is stopped and the flywheel is marked again. Then, the circumference between the front and rear mark points on the flywheel is divided equally to find the midpoint. This midpoint is the positioning reference point of the top dead center. Finally, the flywheel dead center pointer is adjusted according to this midpoint.

[0003] However, the above-mentioned mechanical manual positioning method has complicated positioning steps, is prone to human error, and has poor working conditions for operators, resulting in painful working conditions. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a method for positioning the top dead center of the piston of a ship's main engine. By using an electronic positioning device installed inside the scavenging box and on the underside of the piston head, combined with laser ranging technology, the positioning work of the top dead center of the piston is completed conveniently, quickly and safely, achieving the effect of easy use and accurate positioning.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for locating the top dead center of a piston during assembly of a ship main engine, the ship main engine comprising a scavenge air box, a piston head, and a No. 1 cylinder. The method is characterized by combining a laser rangefinder, a data processing device, a reference plate, and laser ranging technology to continuously detect the distance from a fixed point in the scavenge air box to the piston head through a cranking operation, screening out the maximum detected value of the distance through data processing, and locating the position of the piston head corresponding to the maximum detected value as the top dead center of the ship main engine piston. The specific steps are as follows:

[0007] The first step is to run the piston head of the No. 1 cylinder to the bottom dead center by forward turning, fix the reference plate horizontally on the lower side of the piston head, fix the laser rangefinder to a fixed point in the scavenge air box and align it with the reference plate without obstruction, install the data processing device on the fuel side platform of the ship's main engine, connect the data processing device and the laser rangefinder via a cable, and then turn on the power supply to complete the installation of all laser rangefinder components;

[0008] In the second step, the piston head is continued to move to 10° before the top dead center by forward cranking, the data processing device is turned on, and the distance between the fixed point in the scavenging box and the piston head is continuously measured by laser using the laser rangefinder and the reference plate. The distance detection data is transmitted to the data processing device in real time, and the forward cranking and laser ranging are continued simultaneously. When the piston passes the top dead center and moves to 5° after the top dead center, the forward cranking and laser ranging are stopped. The data processing device screens and displays the maximum detection value of this distance measurement process on a display screen. The maximum detection value is the distance between the laser rangefinder and the reference plate corresponding to when the piston head is at the top dead center;

[0009] The third step is to turn on the laser rangefinder and data processing device again, measure the distance by laser while rotating the car in the reverse direction, and observe the real-time detection value of the distance displayed by the data processing device. When the displayed value reaches the maximum detection value in the second step, stop rotating the car in the reverse direction. At this time, the piston head is at the highest point, and the highest point is located as the top dead center of the piston.

[0010] Furthermore, in the first step, the fixed point is selected next to the piston stuffing box in the scavenging air box.

[0011] Furthermore, a magnetic suction cup for adsorption installation is provided at the bottom of the laser rangefinder, and the main body of the reference plate is a flat plate, which serves as a reference for distance detection; the laser rangefinder emits a laser toward the reference plate, and the laser is reflected back to the laser rangefinder by the reference plate, thereby the laser rangefinder obtains a distance detection value and transmits it to the data processing device, which processes the data and displays it on the display screen.

[0012] Furthermore, the data processing device is used for personnel operation and reading of distance detection values ​​obtained by laser ranging, and is provided with buttons and a display screen.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. The combined use of positioning device and laser ranging technology avoids the deviation caused by existing human operation, improves the accuracy of positioning, and ensures the assembly quality of the main machine.

[0015] 2. The positioning operation is simple, which reduces the labor intensity of on-site workers and improves production efficiency.

[0016] 3. Compared with the existing method, it saves many tedious operating steps, saves production time and reduces production costs.

[0017] 4. The present invention has high versatility and strong practicality, and can be applied to main machines of different cylinder diameters and types.

[0018] In short, the present invention has quick and accurate positioning, improves on-site operation efficiency, reduces the labor intensity of on-site operators, avoids deviations caused by manual operation, improves the manufacturing quality of the host, and has the advantages of simple use, easy installation, and high versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural diagram of a laser rangefinder.

[0020] Figure 2 It is a structural diagram of a data processing device.

[0021] Figure 3 It is a structural diagram of the reference plate.

[0022] Figure 4 It is a schematic diagram of the method of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments, but the scope of protection claimed in the present invention shall not be limited thereby.

[0024] The invention is used for positioning the top dead center of a piston during the assembly process of a ship main engine.

[0025] The present invention first adopts a positioning device consisting of three components: a laser rangefinder, a data processing device and a reference plate. The three components are installed inside the scavenging box and on the lower side of the piston head. Then, during the turning process, the distance from a fixed point in the scavenging box to the lower side of the piston head is continuously detected. The maximum detection value is screened out by the data processing device, and then the turning is reversed. When the piston moves up to the maximum value displayed on the rangefinder, it is the top dead center of the piston, thereby completing the positioning of the top dead center of the piston of the ship's main engine conveniently, quickly and safely.

[0026] The positioning device is an automatic distance laser detection device, which requires each component to be used in combination with a specific method to complete the positioning operation.

[0027] See also Figure 1The illustrated laser rangefinder 1 is a conventional, compact instrument. It is mounted within the scavenge air box of the main engine (next to the piston stuffing box) via a magnet on its bottom. Its primary function is to measure the distance between itself and the reference plate. A wired connection is established between the laser rangefinder 1 and the data processing device for data transmission, and the data processing device provides it with a 24V DC power supply.

[0028] See also Figure 2 The data processing device 2 shown in the figure is a prior art, which is used to record and filter data. It is a device for personnel to operate and read data. It is placed on the platform on the fuel side outside the scavenge air box to facilitate personnel to operate and view data. The data processing device 2 has a rectangular shape with a display screen and operation buttons on the front. It is wired to the laser rangefinder 1 and is powered by 24V DC charging.

[0029] See also Figure 3 The illustrated reference plate 3 is horizontally attached to the underside of the piston via a magnet. It serves as the reference (end point) for laser ranging, and its size varies with the main engine cylinder diameter. The main body of the reference plate 3 is a flat plate with a magnet mounted on its upper portion, which connects to the main engine piston. During operation, the reference plate 3 remains horizontal throughout the piston's movement. This plate effectively protects the piston assembly and the interior of the cylinder liner, preventing damage.

[0030] The laser rangefinder 1 and the reference plate 3 must be completely level and aligned with each other during installation, and there should be no obstruction to the laser between the laser rangefinder 1 and the reference plate 3 .

[0031] The operating principle of the positioning device is as follows: when an operator presses the start button on the data processing device 2, the laser rangefinder 1 begins operating, emitting a laser beam toward the reference plate 3. The laser beam is reflected by the reference plate 3 and returned to the laser rangefinder 1. The laser rangefinder 1 then obtains a distance value, which is transmitted to the data processing device 2 for processing and displayed on the display screen of the data processing device 2 in real time. After the positioning device is installed on the main engine of the vessel, the distance measured between the laser rangefinder 1 and the reference plate 3 continuously changes as the main engine rotates. When the operator presses the stop button, the laser rangefinder 1 stops measuring distance, and the data processing device 2 selects the maximum distance value from the measured data and displays it on the display screen.

[0032] Example

[0033] See also Figure 4 The method for positioning the piston top dead center during assembly of a ship main engine according to the present invention comprises the following specific steps:

[0034] first step,

[0035] First, turn the piston of cylinder No. 1 to the bottom dead center, and then install all the components of the positioning device: install the laser rangefinder 1 next to the piston rod stuffing box, install the reference plate 3 on the underside of the piston head, and place the data processing device 2 on the platform on the fuel side of the ship's main engine. Then, connect the data processing device 2 to the laser rangefinder 1 via a cable and turn on the power supply.

[0036] In the second step, the piston of cylinder No. 1 is cranked to about 10° before the top dead center, and the laser rangefinder 1 and the data processing device 2 are turned on. The laser rangefinder 1 and the reference plate 3 continuously perform laser distance measurement of the distance between them, and the data is transmitted to the data processing device 2. The cranking is continued until the piston passes the top dead center and runs to about 5° after the top dead center. The cranking is stopped and the laser distance measurement of the distance is stopped. The data processing device screens and displays the maximum distance in this measurement on its display screen; the maximum distance is the distance between the laser rangefinder 1 and the reference plate 3 corresponding to the piston at the top dead center.

[0037] The third step is to turn on the laser rangefinder 1 and the data processing device 2 again, and reverse the car while observing the real-time distance displayed on the display screen of the data processing device 2. When the display value of the display screen reaches the maximum distance displayed on the display screen in the second step, stop turning the car. At this time, the piston has reached and is at the highest point. Confirm that the highest point is the top dead center of the piston. Finally, adjust the dead center pointer of the flywheel.

[0038] The present invention has quick and accurate positioning, improves on-site operation efficiency, reduces the labor intensity of on-site operators, avoids deviations caused by manual operation, improves the manufacturing quality of the host, and has the advantages of simple use and convenient installation.

[0039] The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent changes and modifications made based on the content of the present invention should fall within the technical scope of the present invention.

Claims

1. A method for locating the top dead center of a piston during assembly of a ship main engine, wherein the ship main engine comprises a scavenging air box, a piston head, and a No. 1 cylinder, characterized in that: A laser rangefinder, a data processing device, a reference plate, and laser ranging technology are used in combination. The distance from the fixed point in the scavenging air box to the piston head is continuously detected through a cranking operation. The maximum detection value of the distance is screened out through data processing. The position of the piston head corresponding to the maximum detection value is located as the top dead center of the piston of the ship's main engine. The specific steps are as follows: The first step is to run the piston head of the No. 1 cylinder to the bottom dead center by forward turning, fix the reference plate horizontally on the lower side of the piston head, fix the laser rangefinder to a fixed point in the scavenge air box and align it with the reference plate without obstruction, install the data processing device on the fuel side platform of the ship's main engine, connect the data processing device and the laser rangefinder via a cable, and then turn on the power supply to complete the installation of all laser rangefinder components; In the second step, the piston head is continued to move to 10° before the top dead center by forward cranking, the data processing device is turned on, and the distance between the fixed point in the scavenging box and the piston head is continuously measured by laser using the laser rangefinder and the reference plate. The distance detection data is transmitted to the data processing device in real time, and the forward cranking and laser ranging are continued simultaneously. When the piston passes the top dead center and moves to 5° after the top dead center, the forward cranking and laser ranging are stopped. The data processing device screens and displays the maximum detection value of this distance measurement process on a display screen. The maximum detection value is the distance between the laser rangefinder and the reference plate corresponding to when the piston head is at the top dead center; The third step is to turn on the laser rangefinder and data processing device again, measure the distance by laser while rotating the car in the reverse direction, and observe the real-time detection value of the distance displayed by the data processing device. When the displayed value reaches the maximum detection value in the second step, stop rotating the car in the reverse direction. At this time, the piston head is at the highest point, and the highest point is located as the top dead center of the piston.

2. The method for positioning the piston top dead center during assembly of a ship main engine according to claim 1, characterized in that: In the first step, the fixed point is selected beside the piston stuffing box in the scavenging air box.

3. The method for positioning the piston top dead center during assembly of a ship main engine according to claim 1, characterized in that: The bottom of the laser rangefinder is provided with a magnetic suction cup for adsorption installation. The main body of the reference plate is a flat plate, which serves as a reference for distance detection. The laser rangefinder emits a laser towards the reference plate, and the laser is reflected back to the laser rangefinder by the reference plate. The laser rangefinder thereby obtains a distance detection value and transmits it to the data processing device, which processes the data and displays it on a display screen.

4. The method for positioning the piston top dead center during assembly of a ship main engine according to claim 1, characterized in that: The data processing device is used for personnel operation and reading of distance detection values ​​obtained by laser ranging, and is provided with buttons and a display screen.

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