System, method and device for measuring compression ratio of engine to be measured
By connecting the engine combustion chamber to the liquid storage container and using image acquisition and computing equipment to obtain changes in liquid volume, the problem of inaccurate compression ratio measurement in traditional methods is solved, and efficient and accurate compression ratio measurement is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-24
- Publication Date
- 2026-03-27
AI Technical Summary
Traditional methods are difficult to accurately measure the compression ratio of the engine under test, mainly because it is difficult to find the piston's top dead center and bottom dead center, resulting in large measurement errors.
By connecting the engine's combustion chamber to the liquid storage container, image acquisition equipment and computer equipment are used to acquire real-time changes in liquid volume, calculate the compression ratio, avoid manual confirmation of piston dead center, and use image analysis technology to obtain the maximum and minimum liquid volumes to calculate the compression ratio.
It improves the accuracy and efficiency of compression ratio measurement, reduces operational difficulty, minimizes human error, and avoids reliance on operator skills.
Smart Images
Figure CN121740447A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of vehicle technology, and in particular to a compression ratio measurement system, method and apparatus for an engine under test. Background Technology
[0002] Compression ratio is a crucial parameter affecting the performance of an engine under test. It is the ratio of the gas volume in the cylinder at bottom dead center to the gas volume at top dead center. Rapidly and accurately measuring the compression ratio of an engine under test is a key step in its development and calibration.
[0003] Currently, titration is the primary method used to measure the compression ratio of an engine under test. Titration requires accurately locating the piston's top and bottom dead centers, then using a burette to drip liquid into the cylinder to measure the cylinder volume, and finally calculating the compression ratio. However, in traditional techniques, it is difficult to accurately locate the piston's top and bottom dead centers, leading to significant measurement errors. Summary of the Invention
[0004] Therefore, it is necessary to provide a compression ratio measurement system, method, and apparatus for an engine under test that can improve the accuracy of engine compression ratio measurement, in order to address the aforementioned technical problems.
[0005] In a first aspect, this application provides a compression ratio measurement system for an engine under test. The engine under test includes a crankshaft, a cylinder, a piston, and a combustion chamber defined by the cylinder and piston. The system includes a liquid storage container, an image acquisition device, and a computer device. The liquid storage container is connected to the combustion chamber so that the internal space of the liquid storage container and the combustion chamber form a receiving space. The image acquisition device is connected to the computer device. The accommodating space is used to contain liquid so that the volume of liquid in the reservoir changes with the movement of the piston as the crankshaft drives the piston to move in the cylinder. Image acquisition equipment is used to acquire images of liquid in a storage container during the process of the crankshaft driving the piston to move inside the cylinder; The computer equipment is used to acquire images captured by the image acquisition equipment, obtain the maximum and minimum volumes of liquid in the storage container based on the images, and determine the compression ratio of the engine under test based on the maximum and minimum volumes.
[0006] In one embodiment, the liquid storage container includes a connector that is installed in the spark plug hole of the engine under test, and the liquid storage container is connected to the combustion chamber of the engine under test through the connector.
[0007] In one embodiment, the spark plug corresponding to the spark plug hole is a first spark plug; The connecting part includes a contoured portion configured to match the shape and installation posture of the first spark plug when it is installed in the spark plug hole.
[0008] In one embodiment, the system further includes a drive unit connected to either end of the crankshaft, the drive unit being used to drive the crankshaft to rotate.
[0009] In one embodiment, the number of liquid storage containers is the same as the number of combustion chambers in the engine under test, and each liquid storage container is connected to the corresponding combustion chamber to form multiple independent containment spaces.
[0010] Secondly, this application also provides a method for measuring the compression ratio of an engine under test. The engine under test includes a crankshaft, a cylinder, a piston, and a combustion chamber defined by the cylinder and the piston. The combustion chamber is connected to the internal space of a liquid storage container to form a liquid-containing storage space. The compression ratio measurement method of the engine under test includes: acquiring an image of the liquid in the reservoir while the crankshaft drives the piston to move inside the cylinder, so that the volume of liquid in the reservoir changes with the movement of the piston; Obtain the maximum and minimum volumes of liquid in the storage container from the image; The compression ratio of the engine under test is determined based on the maximum and minimum volumes of liquid in the storage container.
[0011] In one embodiment, determining the compression ratio of the engine under test based on the maximum and minimum volumes of liquid in the reservoir includes: Obtain the total volume of the liquid, which is set based on the cylinder head combustion chamber volume and single-cylinder displacement; The compression ratio of the engine under test is determined based on the total volume of the liquid, the maximum volume of the liquid in the storage container, and the minimum volume of the liquid.
[0012] In one embodiment, the formula for determining the compression ratio of the engine under test based on the total volume, maximum volume, and minimum volume is as follows: CR = (V0 - Vmin) / (V0 - Vmax); Where CR is the compression ratio of the engine under test, V0 is the total volume of the liquid, Vmin is the minimum volume of the liquid in the storage container, and Vmax is the maximum volume of the liquid in the storage container.
[0013] In one embodiment, the cylinder head combustion chamber volume is the volume of the combustion chamber when the piston is at top dead center, and the single-cylinder displacement is the volume of the cylinder swept by the piston during the process of the piston moving from bottom dead center to top dead center in a single cylinder.
[0014] Thirdly, this application provides a compression ratio measuring device for an engine under test. The engine under test includes a crankshaft, a cylinder, a piston, and a combustion chamber defined by the cylinder and the piston. The combustion chamber is connected to the internal space of a liquid storage container to form a liquid-containing storage space. The compression ratio measuring device for the engine under test includes: The acquisition module is used to acquire images of the liquid in the storage container captured by the image acquisition device during the process in which the crankshaft drives the piston to move inside the cylinder, causing the volume of the liquid in the storage container to change with the movement of the piston. The processing module is used to obtain the maximum and minimum volumes of liquid in the storage container based on the image. The calculation module is used to determine the compression ratio of the engine under test based on the maximum and minimum volumes of liquid in the storage container.
[0015] The aforementioned compression ratio measurement system, method, and apparatus for the engine under test, through a structural design that connects the combustion chamber of the engine under test to a liquid storage container, transforms the change in cylinder volume into a dynamic change in the liquid volume within the storage container. Utilizing image acquisition and image analysis technology, the liquid volume is obtained, and the compression ratio of the engine under test is further calculated based on this liquid volume. This eliminates the need for manual repeated cylinder rotation to confirm the piston's top dead center and bottom dead center before measuring the cylinder volume, thus improving measurement efficiency. Furthermore, in traditional techniques, if the number of cylinder rotations is insufficient or the operation is improper, it is difficult to find the true top and bottom dead centers, easily leading to inaccurate measurement results. This application eliminates the need for manual confirmation of the piston's top and bottom dead centers, reducing measurement errors caused by human error, improving measurement accuracy, and avoiding the dependence on operator skill in traditional titration methods, thus reducing operational difficulty. Attached Figure Description
[0016] Figure 1 This is a structural block diagram of the compression ratio measurement system of the engine under test when the piston is at top dead center in some embodiments; Figure 2 This is a block diagram of the compression ratio measurement system of the engine under test when the piston is at bottom dead center in some embodiments; Figure 3 This is a flowchart illustrating the compression ratio measurement method for the engine under test in some embodiments; Figure 4 This is a structural block diagram of the compression ratio measuring device for the engine under test in some embodiments. Detailed Implementation
[0017] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.
[0018] In a first aspect, this application provides a compression ratio measurement system for an engine under test, such as... Figure 1As shown, a test engine 100 is used. The test engine 100 includes a crankshaft 19, a cylinder, a piston 22, and a combustion chamber 14 defined by the cylinder 21 and the piston 22. The compression ratio measurement system of the test engine includes a liquid storage container 11, an image acquisition device 12, and a computer device (not shown). The liquid storage container 11 is connected to the combustion chamber 14 so that the internal space of the liquid storage container 11 and the combustion chamber 14 form a receiving space. The image acquisition device 12 is connected to the computer device. The receiving space is used to contain liquid so that the volume of liquid in the liquid storage container 11 changes with the movement of the piston 22 as the crankshaft 19 drives the piston 22 to move in the cylinder 21. The image acquisition device 12 is used to acquire images of the liquid in the liquid storage container 11 as the crankshaft 19 drives the piston 22 to move in the cylinder 21. The computer device is used to acquire the images acquired by the image acquisition device 12, obtain the maximum and minimum volumes of the liquid in the liquid storage container 11 based on the images, and determine the compression ratio of the test engine 100 based on the maximum and minimum volumes.
[0019] Among them, the compression ratio of the engine under test is the ratio of the gas volume in cylinder 21 when piston 22 is at bottom dead center to the gas volume in cylinder 21 when piston 22 is at top dead center, which is an important parameter affecting the performance of the engine under test.
[0020] The combustion chamber 14 is a sealed space formed by the cylinder wall, piston top surface, cylinder head bottom surface and valve periphery structure.
[0021] Cylinder 21 is the core working chamber component of the engine under test 100, which is a cylindrical sealed space formed by the cylinder wall, cylinder head and piston.
[0022] The liquid storage container 11 is used to receive and store the liquid flowing into the combustion chamber 14 during the movement of the piston within the cylinder 21 driven by the crankshaft, providing a carrier for the visual detection of liquid volume changes. The liquid can be engine oil.
[0023] The image acquisition device 12 is an imaging device, such as a high-speed camera, that is connected to a computer device for real-time capture of changes in the liquid level or shape of the liquid in the liquid storage container 11 during the operation of the engine under test 100, and generates image data that can be used for volume analysis.
[0024] In this application, the image acquisition device 12 can take high-speed photos of the upper end of the liquid storage container 11 according to the required photo capture frequency, and can identify the liquid level in the photos and obtain the liquid volume in the liquid storage container 11 at that time. Specifically, the image acquisition device 12 can be a high-speed camera, and the frequency of the high-speed camera can be greater than or equal to 1Hz.
[0025] Computer equipment is a terminal device equipped with image analysis algorithms and compression ratio calculation programs. It has the functions of image reception, data processing, and result output, and is the core processing unit for realizing volume quantization and compression ratio derivation.
[0026] The maximum volume of liquid in the liquid storage container 11 corresponds to the total amount of liquid flowing into the liquid storage container 11 when the volume of the combustion chamber 14 of the engine under test 100 is the smallest, that is, when the piston 22 is at top dead center. At this time, the volume of the combustion chamber 14 is the smallest, and the volume of liquid discharged is the largest.
[0027] The minimum volume of liquid in the liquid storage container 11 corresponds to the total amount of liquid flowing into the liquid storage container 11 when the volume of the combustion chamber 14 of the engine under test 100 is at its maximum, that is, when the piston 22 is at the bottom dead center. At this time, the volume of the combustion chamber 14 is at its maximum, and the volume of liquid discharged is at its minimum.
[0028] in addition, Figure 1 The diagram also illustrates the cylinder head 20 of cylinder 21 of the engine under test 100, and the connecting rod 23 for connecting the piston 22 and the crankshaft 19. The cylinder head 20 has an injection port, which can be sealed using a sealing structure.
[0029] Specifically, the liquid storage container 11 in this application can be a container with openings at both ends. One end of the opening establishes a sealed connection with the combustion chamber 14 of the engine under test, ensuring that the liquid can flow bidirectionally between the combustion chamber 14 and the liquid storage container 11. The other end of the opening can be used to add a certain amount of liquid, such as engine oil, for subsequent compression ratio testing.
[0030] Furthermore, this application pre-establishes a communication connection between the image acquisition device and the computer device, and aligns the image acquisition device 12 with the visual area of the liquid storage container 11, such as the transparent cavity wall, to ensure that the entire container wall of the liquid storage container 11 can be captured, specifically the upper surface position of the liquid in the liquid storage container 11.
[0031] In this application, the liquid storage container 11, after being calibrated by titration, has a volume scale marked on its upper end. The volume of liquid in the liquid storage container 11 can be accurately read through this volume scale. The image acquisition device 12 needs to be placed at a position that can be aligned with the volume scale of the liquid storage container 11.
[0032] Furthermore, during the process of crankshaft 19 driving piston 22 to move within cylinder 21, the reciprocating motion of piston 22 drives the volume of combustion chamber 14 to change periodically. When piston 22 moves downward, the volume of combustion chamber 14 increases, the internal pressure decreases, and liquid in liquid reservoir 11 flows into combustion chamber 14 through opening 13, reducing the volume of liquid in liquid reservoir 11. When piston 22 moves upward, the volume of combustion chamber 14 decreases, the internal pressure increases, and liquid in combustion chamber 14 is squeezed back into liquid reservoir 11, increasing the volume of liquid in liquid reservoir 11. During this process, image acquisition device 12 continuously acquires real-time images of the liquid in liquid reservoir 11 and transmits the image data to computer equipment in real time.
[0033] Furthermore, after receiving the image data, the computer equipment extracts the liquid volume data corresponding to each image through image analysis algorithms, such as liquid level recognition and pixel quantization. From the volume data of the entire cycle, the maximum and minimum liquid volumes in the liquid storage container 11 are selected. The maximum liquid volume in the liquid storage container 11 corresponds to the minimum volume of the combustion chamber 14, and the minimum liquid volume in the liquid storage container 11 corresponds to the maximum volume of the combustion chamber 14. According to the definition of compression ratio, the compression ratio of the engine under test 100 is calculated by formula, and the result is stored or output.
[0034] In one embodiment, please continue to refer to Figure 1 The liquid storage container 11 includes a connecting part 15, which is installed in the spark plug hole 16 of the engine under test 100. The liquid storage container 11 is connected to the combustion chamber 14 of the engine under test 100 through the connecting part 15.
[0035] Among them, the spark plug hole 16 of the engine under test 100 is a pre-set threaded mounting hole on the cylinder head 20 of the engine under test 100. Its original function is to install spark plugs, and in this application it is used as a mounting hole for the connection part.
[0036] The connecting part 15 is a detachable adapter structure on the liquid storage container 11, such as a column with sealing threads. Its shape matches the size and structure of the spark plug hole 16, and it is used to achieve mechanical fixation and fluid sealing communication between the liquid storage container 11 and the engine under test. Specifically, the connecting part 15 can be a hollow design with openings at both ends, with openings 13 and 24. The liquid storage container 11 is connected to the combustion chamber 14 of the engine under test 100 through the openings at both ends of the connecting part 15.
[0037] Specifically, this application constructs a sealed communication channel between the liquid reservoir 11 and the combustion chamber 14 by fitting the connecting part 15 with the spark plug hole 16 of the engine under test 100. During the movement of the piston 22 within the cylinder 21 driven by the crankshaft 19, the reciprocating motion of the piston 22 causes periodic changes in the volume of the combustion chamber 14. When the volume of the combustion chamber 14 increases, the liquid in the liquid reservoir 11 flows into the combustion chamber 14 through the opening 13 of the connecting part 15; when the volume of the combustion chamber 14 decreases, the liquid in the combustion chamber 14 is guided back to the liquid reservoir 11 through the opening 13 of the connecting part 15. Through this dynamic fluid exchange process, the volume change of the combustion chamber 14 is transformed into a volume change of the liquid in the liquid reservoir 11, providing a physical basis for subsequent image acquisition and compression ratio calculation.
[0038] The beneficial effects of this embodiment are as follows: the connecting part 15 and the spark plug hole 16 adopt an adaptive structural design, which can realize the sealed communication between the combustion chamber 14 and the liquid storage container 11, avoiding measurement errors caused by liquid leakage. By using the original spark plug hole 16 of the engine under test 100 as the assembly interface, there is no need to perform additional processing on the core structures such as the cylinder head 20 of the cylinder 21 and the combustion chamber 14. The connecting part can be directly adapted and installed, which is efficient in disassembly and assembly and does not damage the original performance of the engine under test 100.
[0039] In one embodiment, such as Figure 1 As shown, the spark plug corresponding to the spark plug hole 16 is the first spark plug, and the connecting part 15 includes a contouring part, which is configured to match the shape and installation posture of the first spark plug when it is installed in the spark plug hole 16.
[0040] The first spark plug refers to the spark plug that is compatible with the spark plug hole 16 of the engine under test, and is the core component of the gasoline engine ignition system.
[0041] The contoured section refers to a specially designed structural segment on the connecting part 15 that matches the external shape of the first spark plug. The external shape refers to the external geometry and dimensions.
[0042] The installation posture refers to the spatial arrangement of the first spark plug after it has been tightened and fixed in the spark plug hole 16, including its installation position, axial direction, radial angle, and relative positional relationship with the cylinder head combustion chamber wall.
[0043] Specifically, the geometry, dimensions, and spatial position angle of the contoured part are consistent with the state when the first spark plug is actually installed in the spark plug hole 16, so as to ensure that the connecting part 15 can be precisely installed into the spark plug hole 16 like a spark plug.
[0044] In one embodiment, the connecting part 15 can be designed by 1:1 conforming to the spark plug structure of the engine under test 100.
[0045] In one embodiment, such as Figure 1 As shown, the liquid storage container 11 also includes a liquid storage section 17, and the liquid storage section 17 and the connecting section 15 are detachably connected.
[0046] Among them, the liquid storage section 17 is the core volume carrier of the liquid storage container 11. It is used to store the liquid flowing into the combustion chamber 14 through the connection section 15 during the operation of the engine under test 100, providing a space for dynamic changes in liquid volume. At the same time, it can have visualization characteristics such as transparent materials or structural design adapted to image acquisition, ensuring that the image acquisition device 12 can clearly capture changes in the liquid surface, providing a basis for computer equipment to analyze the maximum and minimum volumes.
[0047] Specifically, the connecting part 15 can be a hollow device with openings at both ends, one opening 13 communicating with the liquid storage part 17 and the other opening 24 communicating with the combustion chamber of the engine under test 100. The liquid storage container 11 and the combustion chamber 14 of the engine under test 100 are connected through the connecting part 15.
[0048] The separate design of the reservoir 17 and the connecting part 15 allows for the replacement of only the connecting part according to the spark plug structure for different types of engines. Alternatively, when the reservoir is worn, contaminated, or needs to be adapted to engines with different volume requirements, the reservoir can be disassembled and replaced separately without replacing the entire reservoir or connecting part, thus reducing consumable consumption and maintenance costs. In addition, the removable reservoir facilitates regular cleaning of residual liquid or impurities inside, preventing dirt from affecting the accuracy of liquid level recognition.
[0049] In one embodiment, such as Figure 1 As shown, the system also includes a drive device 18, which is connected to any end of the crankshaft 19 of the engine under test 100. The drive device 18 is used to drive the crankshaft 19 of the engine under test to rotate.
[0050] Among them, crankshaft 19 refers to the core power transmission component of the engine under test 100, which converts the reciprocating linear motion of piston 22 into rotational motion. Its rotation directly drives the periodic change of the volume of combustion chamber 14, and is the mechanical power source for realizing the flow of liquid between combustion chamber 14 and liquid storage container 11.
[0051] The drive unit 18 is a power output device connected to one end of the crankshaft 19 of the engine under test 100. It is used to actively provide rotational power to drive the crankshaft 19 to rotate at a preset speed or stroke, so as to ensure the stability and controllability of the volume change of the combustion chamber 14.
[0052] Specifically, in this application, the drive unit 18 is connected to the rear end of the crankshaft 19 of the engine under test 100 by bolts or other means. The drive unit 18 and the image acquisition device 12, such as a high-speed camera, are turned on. The drive unit 18 drives the crankshaft 19 to rotate at a fixed angular velocity, such as 1 degree / s. The high-speed camera records the volume V1, V2, ... V360 of the oil in the reservoir 11 at a frequency of 1Hz. After 360s, the maximum and minimum volumes among V1 to V360 are extracted and recorded as Vmax and Vmin, respectively. The compression ratio of the engine under test 100 is further determined based on the maximum and minimum volumes.
[0053] The beneficial effect of this embodiment is that the crankshaft 19 can be driven to rotate independently by the drive device 18, without the need to manually rotate the crankshaft 19. The rotation speed can be precisely controlled, ensuring the consistency of the volume change of the combustion chamber 14, providing a stable basis for liquid volume measurement, and improving the accuracy of the measurement results.
[0054] In one embodiment, the number of liquid storage containers 11 is the same as the number of combustion chambers 14 in the engine under test 100, and each liquid storage container 11 is connected to the corresponding combustion chamber 14 to form multiple independent accommodating spaces.
[0055] Specifically, the engine 100 to be tested in this application can be a multi-cylinder engine, such as a four-cylinder or a six-cylinder engine, with each cylinder working independently and having the same structure.
[0056] In this application, for multi-cylinder engines, the same number of liquid storage containers 11 can be equipped according to the number of cylinders of the engine to be tested, so that the compression ratio of each cylinder can be measured simultaneously, which greatly improves efficiency.
[0057] Specifically, each cylinder of the multi-cylinder engine has an independent combustion chamber 14, and the piston 22 of each cylinder 21 is driven by the same crankshaft 19, synchronously completing the periodic change of volume. This application configures multiple liquid storage containers 11 corresponding to the number of cylinders 21. When the drive device 18 drives the crankshaft 19 to rotate, the volume of the combustion chamber 14 of each cylinder 21 changes independently, driving the liquid to flow dynamically between the corresponding liquid storage container 11 and the combustion chamber 14, realizing a one-to-one correspondence between the volume change of each cylinder 21 and the volume change of the liquid in the corresponding liquid storage container 11. Finally, through image acquisition and computer analysis, the compression ratio of each cylinder 21 is obtained.
[0058] The beneficial effect of this embodiment is that, for multi-cylinder engines, the compression ratio of each cylinder 21 can be measured simultaneously or separately, avoiding the tedious repetition of the traditional single-cylinder measurement method and improving testing efficiency.
[0059] In one embodiment, to reduce measurement time, the rotational speed of the crankshaft 19 can be increased to 6 degrees / s, and the shooting frequency of the image acquisition device 12 can be adjusted to 6Hz, thereby reducing the measurement time to 1 minute.
[0060] This application also provides a schematic diagram of the piston 22 at the bottom dead center, such as... Figure 2 As shown, in Figure 2 The engine compression ratio measurement system includes a liquid reservoir 31, an image acquisition device 32, a computer device, and a drive unit 34. The liquid reservoir 31 includes a liquid storage section 40 and a connecting section 33. The connecting section 33 has an opening, through which the liquid reservoir 31 communicates with the combustion chamber of the engine under test. The cylinder 37 of the engine under test includes a cylinder head 36, and the connecting section 33 is located within the spark plug hole of the cylinder head 36. The engine under test also includes a piston 38 and a connecting rod 39 connecting the piston 38 and the crankshaft 35. When the piston 38 is at bottom dead center, most of the liquid is introduced into the combustion chamber of the engine under test, at which point the liquid volume in the liquid reservoir 31 is at its minimum.
[0061] In a second aspect, this application provides a method for measuring the compression ratio of an engine under test. The engine under test includes a crankshaft, a cylinder, a piston, and a combustion chamber defined by the cylinder and piston. The combustion chamber is connected to the internal space of a liquid reservoir to form a liquid-containing space, such as... Figure 3 As shown, the method for measuring the compression ratio of the engine under test includes: Step S31: During the process of the crankshaft driving the piston to move inside the cylinder, so that the volume of liquid in the storage container changes with the movement of the piston, an image of the liquid in the storage container is acquired by the image acquisition device.
[0062] Step S32: Obtain the maximum and minimum volumes of the liquid in the storage container based on the image.
[0063] Step S33: Determine the compression ratio of the engine under test based on the maximum and minimum volumes of liquid in the storage container.
[0064] During the process of the crankshaft driving the piston to move inside the cylinder, the image acquisition device continuously captures real-time images of the liquid in the liquid storage container at a preset frame rate, generating a sequence of images containing changes in liquid level. The acquired image data is transmitted to the computer device in real time and stored via wired or wireless communication. The image timestamp is synchronized with the combustion chamber volume change cycle.
[0065] Furthermore, the computer device calls image analysis algorithms such as edge detection and pixel calibration to preprocess the received sequence of images, accurately identify the liquid surface boundary and the inner wall contour of the liquid storage container in each image, and read the real-time liquid volume corresponding to each image based on the volume scale lines of the liquid storage container.
[0066] Furthermore, the volume data throughout the entire cycle is filtered to extract the maximum and minimum volumes of the liquid in the storage container. The compression ratio of the engine under test is then determined based on the maximum and minimum volumes of the liquid in the storage container.
[0067] In one embodiment, determining the compression ratio of the engine under test based on the maximum and minimum volumes of liquid in the reservoir includes: obtaining the total volume of liquid, which is set according to the cylinder head combustion chamber volume and single-cylinder displacement; and determining the compression ratio of the engine under test based on the total volume, the maximum and minimum volumes of liquid in the reservoir.
[0068] The total volume refers to the total volume of liquid pre-filled into the storage container.
[0069] Specifically, this application can predetermine the total volume of the liquid, wherein the total volume of the liquid can be equal to the cylinder head combustion chamber volume of the cylinder plus the single-cylinder displacement of the engine under test plus a preset threshold, wherein the preset threshold can be set to 50~100ml to ensure that the liquid storage container still has a temperature when the piston is at bottom dead center.
[0070] In one embodiment, the cylinder head combustion chamber volume is the volume of the combustion chamber when the piston is at top dead center, and the single-cylinder displacement is the volume of the cylinder swept by the piston during the process of the piston moving from bottom dead center to top dead center in a single cylinder.
[0071] The cylinder head combustion chamber volume refers to the volume of the enclosed space between the piston top and the cylinder head bottom when the piston reaches top dead center (TDC). Top dead center (TDC) is the position in an engine where the piston top is at its maximum distance from the crankshaft center. TDC is the highest point of the piston stroke.
[0072] Single-cylinder displacement refers to the volume swept by the piston in a single cylinder from bottom dead center to top dead center. Bottom dead center is the position where the piston is closest to the crankshaft center during cylinder movement, corresponding to the lowest point of the piston.
[0073] In one embodiment, the formula for determining the compression ratio of the engine under test based on the total volume, maximum volume, and minimum volume of the liquid is as follows: CR = (V0 - Vmin) / (V0 - Vmax); Where CR is the compression ratio of the engine under test, V0 is the total volume of the liquid, Vmin is the minimum volume of the liquid in the reservoir, representing the volume of the liquid in the reservoir when the piston is at bottom dead center, and Vmax is the maximum volume of the liquid in the reservoir, representing the volume of the liquid in the reservoir when the piston is at top dead center.
[0074] In this application, the change in cylinder volume is converted into a dynamic change in the volume of liquid in the reservoir. Image acquisition and image analysis technology are used to obtain the volume of liquid in the reservoir. Based on the volume of liquid in the reservoir, the compression ratio of the engine under test is calculated. This eliminates the need for manual repeated cylinder rotation to confirm the top dead center and bottom dead center of the piston, improving testing efficiency, avoiding errors caused by manual operation, and improving measurement accuracy.
[0075] In a third aspect, this application provides a compression ratio measuring device for an engine under test. The engine under test includes a crankshaft, a cylinder, a piston, and a combustion chamber defined by the cylinder and the piston. The combustion chamber is connected to the internal space of a liquid reservoir to form a liquid-containing space. The compression ratio measuring device for the engine under test includes: The acquisition module 41 is used to acquire an image of the liquid in the storage container captured by the image acquisition device during the process in which the crankshaft drives the piston to move in the cylinder, so that the volume of the liquid in the storage container changes with the movement of the piston. Processing module 42 is used to obtain the maximum and minimum volumes of liquid in the storage container based on the image; The calculation module 43 is used to determine the compression ratio of the engine under test based on the maximum and minimum volumes of liquid in the liquid storage container.
[0076] In one embodiment, the calculation module 43 can obtain the total volume of liquid pre-filled in the liquid storage container, the total volume being set according to the cylinder head combustion chamber volume and single-cylinder displacement, and determine the compression ratio of the engine under test based on the total volume, the maximum volume, and the minimum volume.
[0077] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.
[0078] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0079] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.
Claims
1. A compression ratio measurement system for an engine under test, the engine under test comprising a crankshaft, a cylinder, a piston, and a combustion chamber defined by the cylinder and the piston, characterized in that, The system includes a liquid storage container, an image acquisition device, and a computer. The liquid storage container is connected to the combustion chamber so that the internal space of the liquid storage container and the combustion chamber form a receiving space. The image acquisition device is connected to the computer. The accommodating space is used to accommodate liquid so that, during the process of the crankshaft driving the piston to move in the cylinder, the volume of the liquid in the liquid storage container changes with the movement of the piston. The image acquisition device is used to acquire images of the liquid in the storage container during the process of the crankshaft driving the piston to move inside the cylinder; The computer device is used to acquire images acquired by the image acquisition device, obtain the maximum and minimum volumes of liquid in the liquid storage container based on the images, and determine the compression ratio of the engine under test based on the maximum and minimum volumes of liquid in the liquid storage container.
2. The system according to claim 1, characterized in that, The liquid storage container includes a connecting part, which is installed in the spark plug hole of the engine under test, and the liquid storage container is connected to the combustion chamber of the engine under test through the connecting part.
3. The system according to claim 2, characterized in that, The spark plug corresponding to the spark plug hole is the first spark plug; The connecting portion includes a contoured portion configured to match the shape and installation posture of the first spark plug when it is installed in the spark plug hole.
4. The system according to claim 1, characterized in that, The system also includes a drive unit connected to either end of the crankshaft, which is used to drive the crankshaft to rotate.
5. The system according to claim 1, characterized in that, The number of liquid storage containers is the same as the number of combustion chambers in the engine under test, and each liquid storage container is connected to the corresponding combustion chamber to form multiple independent accommodating spaces.
6. A method for measuring the compression ratio of an engine under test, characterized in that, The engine under test includes a crankshaft, a cylinder, a piston, and a combustion chamber defined by the cylinder and the piston. The combustion chamber is connected to the internal space of a liquid storage container to form a liquid-containing space. The method includes: acquiring an image of the liquid in the storage container while the crankshaft drives the piston to move within the cylinder, causing the volume of the liquid in the storage container to change with the movement of the piston; The maximum and minimum volumes of the liquid in the storage container are obtained from the image. The compression ratio of the engine under test is determined based on the maximum and minimum volumes of liquid in the storage container.
7. The method according to claim 6, characterized in that, Determining the compression ratio of the engine under test based on the maximum volume and the minimum volume includes: The total volume of the liquid is obtained, and the total volume of the liquid is set according to the cylinder head combustion chamber volume and single-cylinder displacement of the cylinder; The compression ratio of the engine under test is determined based on the total volume of the liquid, the maximum volume of the liquid in the storage container, and the minimum volume of the liquid.
8. The method according to claim 7, characterized in that, The formula for determining the compression ratio of the engine under test based on the total volume of the liquid, the maximum volume and the minimum volume of the liquid in the storage container is as follows: CR = (V0 - Vmin) / (V0 - Vmax); Wherein, CR is the compression ratio of the engine under test, V0 is the total volume of the liquid, Vmin is the minimum volume of the liquid in the storage container, and Vmax is the maximum volume of the liquid in the storage container.
9. The method according to claim 7, characterized in that, The cylinder head combustion chamber volume is the volume of the combustion chamber when the piston is at top dead center, and the single-cylinder displacement is the volume of the cylinder swept by the piston during the process of the piston moving from bottom dead center to top dead center in a single cylinder.
10. A compression ratio measuring device for an engine under test, characterized in that, The engine under test includes a crankshaft, a cylinder, a piston, and a combustion chamber defined by the cylinder and the piston. The combustion chamber is connected to the internal space of a liquid storage container to form a liquid-containing space. The device includes: The acquisition module is used to acquire an image of the liquid in the storage container captured by the image acquisition device during the process in which the crankshaft drives the piston to move in the cylinder, so that the volume of the liquid in the storage container changes with the movement of the piston. The processing module is used to obtain the maximum and minimum volumes of the liquid in the storage container based on the image; The calculation module is used to determine the compression ratio of the engine under test based on the maximum and minimum volumes of liquid in the liquid storage container.