Methanol engine balance shaft installation detection method and detection tool thereof

Abstract

The invention discloses a methanol engine balance shaft installation detection method and a detection tool thereof, and belongs to the technical field of engine assembly. The method comprises the following steps: processing a positioning pin hole in an engine cylinder body, and processing a positioning hole for measurement in a balance shaft; grading the distance from the bottom surface of the cylinder body to the main shaft hole of the cylinder body, the distance from the axis of the balance shaft to the mounting surface and the thickness of a gasket, and selecting the cylinder body, the balance shaft and the gasket for assembly; measuring the distance between the crankshaft axis and the balance shaft axis by using a detection tool; the operation test is carried out on an engine assembly test bench, the vibration performance of an engine is monitored through a vibration sensor, and a second-order vibration component corresponding to the balance shaft is separated and analyzed. Through a three-dimensional space positioning reference system formed by the cylinder body positioning pin hole and the positioning hole for measuring the balance shaft, the coaxiality error of the axis of the balance shaft and the axis of the crankshaft is reduced, the second-order vibration suppression efficiency is improved, and abnormal vibration excitation caused by axis deviation is remarkably improved.

Description

Technical Field

[0001] The invention relates to a methanol engine balance shaft installation detection method and a detection tool thereof, belonging to the technical field of engine assembly. Background Art

[0002] In the field of four-cylinder, four-stroke internal combustion engine technology, the complex mechanical vibrations generated during the engine combustion process are a key factor affecting operating smoothness and durability. Research has shown that first-order vibrations account for up to 70% of this vibration, while second-order vibrations contribute approximately 30%. While first-order vibrations can be effectively suppressed through crankshaft dynamic balancing, second-order vibrations, due to their strong correlation with the piston's reciprocating frequency, require dynamic compensation mechanisms within the balance shaft to counteract them.

[0003] In traditional technical solutions, the balance shaft system usually adopts a single-axis or dual-axis layout. By installing the balance shaft assembly in the engine oil pan area, the reverse inertia force generated by its rotation is used to offset the second-order reciprocating inertia force. However, in the application scenario of methanol fuel engine, the existing balance shaft installation and sealing technology has significant technical defects: 1. Insufficient assembly precision: The high-frequency vibration characteristics generated by methanol fuel combustion place higher requirements on the balance shaft-cylinder interface. However, the traditional installation process lacks a graded matching mechanism, resulting in a large coaxiality error between the balance shaft axis and the crankshaft axis, far exceeding the dynamic balance design threshold and causing abnormal vibration excitation.

[0004] 2. Material durability defects: The highly corrosive environment of methanol combustion products (formaldehyde, formic acid, etc.) causes the contact fatigue life of the balance shaft support bearings to be shortened to less than 60% of that of conventional gasoline engines. The traditional design does not use anti-corrosion coatings or corrosion-resistant alloy materials, which accelerates the wear and failure of the supporting parts.

[0005] 3. Environmental adaptability defects: The existing sealing structure does not take into account the coupling effect of the operating temperature and humidity of the methanol engine, resulting in creep relaxation of the balance shaft end cover seal under the combined working conditions of heat, humidity and vibration, causing the lubricating oil leakage rate to exceed the industry standard.

[0006] 4. Inconsistent installation datum: The traditional process uses the bottom surface of the cylinder block as a single installation datum, and fails to establish a three-dimensional spatial constraint relationship between the cylinder block main shaft hole and the balance shaft axis. This results in a large axis offset in the assembly cumulative error, significantly reducing the vibration coupling suppression efficiency.

[0007] 5. Lack of vibration monitoring: Existing technologies only conduct macroscopic evaluation based on the vibration intensity of the entire machine. There is a lack of special monitoring methods for the vibration of the relevant orders of the balance shaft, making it impossible to achieve quantitative traceability and dynamic optimization of the vibration source. Summary of the Invention

[0008] In order to solve the problems existing in the background technology, the present invention provides a methanol engine balance shaft installation detection method and a detection tool thereof.

[0009] To achieve the above object, the present invention adopts the following technical solution: a method for detecting the installation of a balance shaft of a methanol engine, the method comprising the following steps: S1: Positioning structure design: A positioning pin hole is machined on the engine cylinder block. The positioning pin hole is used to locate the installation position of the balance shaft. A measuring positioning hole is machined on the balance shaft. The measuring positioning hole is used to measure the distance between the balance shaft axis and the crankshaft axis after installation. The positioning pin hole and the measuring positioning hole constitute the assembly positioning reference. S2: Grading matching process: The distance H1 from the bottom of the cylinder block to the main shaft hole, the distance H2 from the axis of the balance shaft to the mounting surface, and the gasket thickness T are graded and a matching relationship table is established. Based on the measured values, the cylinder block, balance shaft, and gasket of the corresponding grade are selected for assembly. During assembly, positioning is achieved by matching the locating pins with the locating pin holes. The classification standards described in S2 are: ΔH1=|H 1实际 -H 1设计 |≤0.02mm; ΔH2=|H 2实际 -H 2设计 |≤0.015mm; ΔT=|T 实际 -T 设计 |≤0.005mm.

[0010] S3: Axis distance measurement: After the balance shaft is installed, use the detection tool to measure the distance L between the crankshaft axis and the balance shaft axis through the measuring positioning hole in batches. 实测值 , when L 实测值 Out of tolerance range (L 设计值 ±0.05mm≤L 实测值 ≤L 设计值 +0.10mm), compensation is made by adjusting the gasket thickness; the gasket described in S3 includes a basic gasket and a fine-tuning gasket, wherein: the thickness of the basic gasket is an integer multiple of 0.1mm, the thickness of the fine-tuning gasket is an integer multiple of 0.02mm, and the combined thickness satisfies: T=n×0.1+m×0.02, where n and m are both positive integers.

[0011] The detection tool includes an operating rod, an angle plate, a bolt and a locator. The operating rod, angle plate and locator are arranged in sequence and connected by at least two bolts. The bolts are slidably connected to the operating rod and the angle plate, and the bolts are threadedly fixed to the locator. An angle identification line is provided on the angle plate.

[0012] S4: Online vibration detection: An operating test is performed on an engine assembly test bench. The engine vibration performance is monitored through a vibration sensor. The second-order vibration component corresponding to the balance shaft is separated and analyzed. When the second-order vibration peak exceeds the preset limit value, the balance shaft installation is judged to be unqualified.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention reduces the coaxiality error between the balance shaft axis and the crankshaft axis through the three-dimensional spatial positioning reference system composed of the cylinder block positioning pin hole and the balance shaft measurement positioning hole, improves the second-order vibration suppression efficiency, and significantly improves the abnormal vibration excitation caused by axis deviation.

[0014] 2. The present invention adopts a graded matching process to implement precision control of parameters, and cooperates with the fine-tuning mechanism of the combined gasket to improve the contact fatigue life of the balance shaft support part and effectively resist the corrosive effects of methanol combustion products.

[0015] 3. The detection tool of the present invention integrates a precise adjustment structure of the angle plate and the positioner, and cooperates with the online vibration monitoring system to conduct a special analysis of the second-order vibration component, thereby reducing the leakage rate of the seal under the combined working conditions of heat, moisture and vibration, and meeting the sealing requirements of the methanol engine under extreme working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of an engine locating pin hole of the present invention; Figure 2 is a schematic diagram of a positioning hole for measuring a balance shaft of the present invention; Figure 3 is a schematic diagram of the use of the detection tool of the present invention; Figure 4 It is a schematic diagram of the vibration measurement test bench of the present invention; Figure 5 It is a structural diagram of the detection tool; Figure 6 yes Figure 5 Exploded diagram. DETAILED DESCRIPTION

[0017] The technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0018] A methanol engine balance shaft installation detection method, the method comprising the following steps: S1: Positioning structure design: A positioning pin hole is machined on the engine cylinder block. The positioning pin hole is used to accurately locate the installation position of the balance shaft. A measuring positioning hole is machined on the balance shaft. The measuring positioning hole is used to measure the distance between the balance shaft axis and the crankshaft axis after installation. The positioning pin hole and the measuring positioning hole constitute the assembly positioning reference. S2: Grading matching process: The distance H1 from the bottom of the cylinder block to the main shaft hole, the distance H2 from the axis of the balance shaft to the mounting surface, and the gasket thickness T are graded and a matching relationship table is established. Based on the measured values, the cylinder block, balance shaft, and gasket of the corresponding grade are selected for assembly. During assembly, positioning is achieved by matching the locating pins with the locating pin holes. The classification standards described in S2 are: ΔH1=|H 1实际 -H 1设计 |≤0.02mm; ΔH2=|H 2实际 -H 2设计 |≤0.015mm; ΔT=|T 实际 -T 设计 |≤0.005mm.

[0019] S3: Axis distance measurement: After the balance shaft is installed, use the detection tool to measure the distance L between the crankshaft axis and the balance shaft axis through the measuring positioning hole in batches. 实测值 , when L 实测值 Out of tolerance range (L 设计值 ±0.05mm≤L 实测值 ≤L 设计值 +0.10mm), compensation is made by adjusting the thickness of the gasket; the gasket includes a basic gasket and a fine-tuning gasket, wherein: the thickness of the basic gasket is an integer multiple of 0.1mm, the thickness of the fine-tuning gasket is an integer multiple of 0.02mm, and the combined thickness satisfies: T=n×0.1+m×0.02, where n and m are both positive integers.

[0020] The detection tool includes an operating rod 1, an angle disc 2, a bolt 3 and a locator 4. The operating rod 1, the angle disc 2 and the locator 4 are arranged in sequence and connected by at least two bolts 3. The bolts 3 are all slidably connected to the operating rod 1 and the angle disc 2. The bolts 3 are threadedly fixed to the locator 4. An angle identification line is provided on the angle disc 2.

[0021] When in use, the positioner (4) is assembled to the end face of the crankshaft, and the angle disc (2) is observed to drive the crankshaft to rotate to a corresponding angle by rotating the operating lever (1), and the angle disc (2) rotates as many times as the angle is reached.

[0022] S4: Online vibration detection: An operating test is performed on an engine assembly test bench. The engine vibration performance is monitored through a vibration sensor. The second-order vibration component corresponding to the balance shaft is separated and analyzed. When the second-order vibration peak exceeds the preset limit value, the balance shaft installation is judged to be unqualified.

[0023] This invention reduces the probability and intensity of engine vibration and noise caused by the corrosive nature of methanol fuel and its combustion products, significantly extending the lifespan of methanol engine balance shafts. Actual testing has shown a 40% reduction in the probability of noise and a 10% reduction in the maximum peak intensity of noise, improving the operating stability and durability of methanol engines. It also improves the accuracy of balance shaft installation, preventing irregular vibration and noise caused by improper installation. It tightens the control of the distance between the balance shaft axis and the crankshaft axis, extending the lifespan of the balance shaft, which is affected by the corrosive nature of methanol fuel during engine operation. It enables online quantitative analysis of the balance shaft's balancing performance. By optimizing the grouping, assembly, and mounting processes, it addresses the existing issues of poor vibration suppression, low installation accuracy, and insufficient long-term reliability. It also clarifies the grading specifications and selection principles for balance shafts, cylinder blocks, and gaskets. It also clarifies the distance between the balance shaft axis and the crankshaft axis during balance shaft installation and its measurement method. It also defines the vibration testing method and quantitative vibration performance limits for engine assembly test benches equipped with balance shafts.

[0024] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0025] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A methanol engine balance shaft installation detection method, characterized by: The method comprises the following steps: S1: Positioning structure design: A positioning pin hole is machined on the engine cylinder block. The positioning pin hole is used to locate the installation position of the balance shaft. A measuring positioning hole is machined on the balance shaft. The measuring positioning hole is used to measure the distance between the balance shaft axis and the crankshaft axis after installation. The positioning pin hole and the measuring positioning hole constitute the assembly positioning reference. S2: Grading matching process: The distance H1 from the bottom of the cylinder block to the main shaft hole, the distance H2 from the axis of the balance shaft to the mounting surface, and the gasket thickness T are graded and a matching relationship table is established. Based on the measured values, the cylinder block, balance shaft, and gasket of the corresponding grade are selected for assembly. During assembly, positioning is achieved by matching the locating pins with the locating pin holes. S3: Axis distance measurement: After the balance shaft is installed, use the detection tool to measure the distance L between the crankshaft axis and the balance shaft axis through the measuring positioning hole in batches. 实测值 , when L 实测值 When the tolerance range is exceeded, compensation is made by adjusting the thickness of the gasket; S4: Online vibration detection: An operating test is performed on an engine assembly test bench. The engine vibration performance is monitored through a vibration sensor. The second-order vibration component corresponding to the balance shaft is separated and analyzed. When the second-order vibration peak exceeds the preset limit value, the balance shaft installation is judged to be unqualified.

2. The methanol engine balance shaft installation detection method according to claim 1, characterized in that: The classification standards described in S2 are: ΔH1=|H 1实际 -H 1设计 |≤0.02mm; ΔH2=|H 2实际 -H 2设计 |≤0.015mm; ΔT=|T 实际 -T 设计 |≤0.005mm。 3. The methanol engine balance shaft installation detection method according to claim 1, characterized in that: The tolerance range of S3 is: L 设计值 ±0.05mm≤L 实测值 ≤L 设计值 +0.10mm.

4. The methanol engine balance shaft installation detection method according to claim 3, characterized in that: The gasket described in S3 includes a basic gasket and a fine-tuning gasket, wherein: the thickness of the basic gasket is an integer multiple of 0.1 mm, the thickness of the fine-tuning gasket is an integer multiple of 0.02 mm, and the combined thickness satisfies: T=n×0.1+m×0.02, where n and m are both positive integers.

5. A methanol engine balance shaft installation detection method according to claim 1 or 4, characterized in that: The detection tool comprises an operating rod (1), an angle disc (2), a bolt (3) and a positioner (4); the operating rod (1), the angle disc (2) and the positioner (4) are arranged in sequence and connected by at least two bolts (3); the bolts (3) are all slidably connected to the operating rod (1) and the angle disc (2); the bolts (3) are fixedly connected to the positioner (4) by threads; and an angle identification line is provided on the angle disc (2).

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