CN115901269A - Method for measuring assembling quality of reciprocating engine crankshaft and automatic measuring mechanism - Google Patents

Abstract

The invention provides a method for measuring the assembling quality of a reciprocating engine crankshaft, which comprises the following steps of S1: installing a crankshaft in a main shaft hole of an engine; s2: the measuring device respectively collects the starting torque, the average torque and the maximum torque of the crankshaft; s3: processing of measurement data: establishing a normal distribution model for the measured value, and defining a specific quantification range of the crankshaft cold-state dragging torque; normal distribution probability density of the sampling single value is calculated through the NORMDIST function, and the occurrence frequency of the sampling single value is calculated through the COUNTIF function; s4: if the difference value between the maximum torque and the minimum torque is less than 5N.m, the assembly quality of the engine crankshaft is detected to be qualified, and the measurement is finished; and if the difference value between the maximum torque and the minimum torque exceeds 5N.m, indicating that the assembling quality of the engine crankshaft is unqualified, and skipping the measurement program to the step S1. The method and the measuring device measure the torque in real time, and quantitatively evaluate the assembly quality of the shafting after processing and analyzing the data, thereby improving the overall assembly qualification rate of the engine and reducing the manufacturing cost.

Description

A method for measuring the assembly quality of a reciprocating engine crankshaft and an automatic measuring mechanism

technical field

The invention relates to a measurement method and an automatic measurement mechanism, in particular to a measurement method and an automatic measurement mechanism for the assembly quality of a reciprocating engine crankshaft, belonging to the technical field of assembly process control of a traditional reciprocating engine crankshaft.

Background technique

With the development of automobile technology, the control of engine factory quality becomes more and more important. The service life and quality of the reciprocating engine are determined by the comprehensive quality of the crankshaft assembly process. The crankshaft assembly is the core control process of the engine. The current traditional engine manufacturing industry generally guarantees its assembly by controlling the machining accuracy of the crankshaft and standardizing the operation process. Quality, this method is a control strategy that checks in advance.

However, in the actual crankshaft assembly procedure, even if the size of each part conforms to the tolerance range, factors such as coaxiality, roundness, and tightening torque between the shaft and the hole will still cause dynamic changes in the clearance between each other. Therefore, This method of verifying the assembly quality of the crankshaft will produce certain errors.

Another method is to verify the quality of engine crankshaft assembly through 100% hot test run, but this method will not only produce a lot of NOX, CH, PM and other substances, pollute the environment, but also consume a lot of fuel, oil and Coolant, thereby increasing the manufacturing cost of the engine.

Contents of the invention

The purpose of the present invention is to provide a method for measuring the assembly quality of the crankshaft of a reciprocating engine and an automatic measurement mechanism. The overall assembly pass rate reduces the manufacturing cost.

For realizing the above object, technical scheme of the present invention is:

A method for measuring the assembly quality of a reciprocating engine crankshaft, comprising the following steps:

S1: Install the crankshaft: select a crankshaft that meets the requirements of the process specification, install the crankshaft into the main shaft hole of the engine, and tighten the main bearing cap;

S2: The control system commands the guiding mechanism to drive the measuring mechanism to move towards the crankshaft. The docking interface of the measuring mechanism is connected to the output end of the crankshaft. After the measuring mechanism is started to drive the crankshaft of the engine to rotate, the starting torque, average torque and maximum torque of the crankshaft are collected respectively:

Measurement of start-up torque: the time for the crankshaft to rotate from a stationary state to a rotating state for 5 seconds, when its rotational speed increases from 0r/min to 30r/min, continuously collect the maximum torque in this state for 3-5 times;

Measurement of the average torque: the crankshaft rotates from a static state, and when its rotation speed reaches 180r/min, it keeps rotating at a constant speed for 10s, and the maximum torque in this state is continuously collected 10 times;

Measurement of the maximum torque: If the collected data suddenly increases sharply during the rotation of the crankshaft, the maximum torque at this time is collected;

S3: Processing of measurement data: using SKEW, KURT functions to constrain the skewness and kurtosis of the starting torque, average torque and maximum torque measured in step S2,

The processed measurement data is generated into a sample space and processed as follows:

(驱动扭矩N.m)：Take the sample mean of the measured data

(Drive torque Nm):

的前提下计算样本方差S²：taking the mean

Calculate the sample variance S ² under the premise of:

为样本均值，n为样本例数；S ² is the sample variance, (N ₁ , N _{2 .......} N _n ) is a random variable,

is the sample mean, n is the sample number;

Compute the sample standard deviation S:

(68.26％)范围内作为判断依据，划定曲轴冷态拖动扭矩的具体量化范围；To build a normal distribution model, in

(68.26%) range as the basis for judging to delineate the specific quantification range of the crankshaft cold drag torque;

Then use the NORMDIST function to calculate the normal distribution probability density of the sampling single value, and the COUNTIF function to calculate the occurrence frequency of the sampling single value;

S4: Judgment method of engine crankshaft assembly quality: According to the value obtained in step S3, if the difference between the maximum torque and minimum torque is less than 5N.m, it means that the engine crankshaft assembly quality inspection is qualified, and the measurement is over;

If the difference between the maximum torque and the minimum torque exceeds 5N.m, it means that the assembly quality of the engine crankshaft is unqualified, and the measurement procedure jumps to step S1.

Further, to tighten the main bearing cap in step S1, a biaxial tightening device is required to simultaneously tighten two powerful bolts on one main bearing cap.

Further, after the crankshaft is installed and the main bearing cap is tightened in step S1, manual pre-cranking is performed for 4-6 turns.

An automatic measuring mechanism for the assembly quality of a crankshaft of a reciprocating engine, including a guiding mechanism, a measuring mechanism and a control system, the guiding mechanism includes a control cylinder, a linear guide rail and a support plate, and the control cylinder is installed on one end of the support plate through a cylinder support frame, The upper end of the support plate is provided with a sliding mounting seat matched with the linear guide rail, which is hoisted on the KBK truss, and the lower part of the support plate is equipped with a motor mounting seat, a torque sensor bracket and a bearing seat.

The measuring mechanism includes a servo motor, a torque sensor, and a docking interface. The servo motor is connected to the support plate through a motor mount, the output shaft of the servo motor is connected to one end of the torque sensor through a coupling, and the other end of the torque sensor is connected to the torque sensor through a coupling. The second device is connected with the output shaft, the output end of the output shaft is equipped with a docking interface, and the docking interface is in clearance fit with the engine crankshaft, the torque sensor is installed on the torque sensor bracket, and the output shaft is installed on the bearing seat.

Further, the torque sensor and the docking interface are connected through a torque limiter.

Further, a speed reducer is arranged between the servo motor 1 and the coupling one.

Compared with the prior art, the beneficial effect of the present invention is: the method provides a solution for the reliability inspection of the engine, overcomes the traditional inspection method that must verify the reliability of the whole machine through the hot test run, and reduces the emission of the hot test run Exhaust gas pollutes the environment and saves fuel consumption. At the same time, the engine manufacturing cost is reduced, and it is especially suitable for the mass-produced engine manufacturing industry.

The measuring device of the present invention realizes the rigid connection between the measuring device and the engine body by docking the automatic measuring device on the free end of the engine cylinder, uses the control cylinder drive device to operate, the docking interface is locked with the crankshaft, and the coupling is driven by a servo motor With the torque sensor, the crankshaft is dragged to rotate according to the set rotation speed, the starting torque and constant speed torque are measured in real time and uploaded to the control system, and finally the accurate drag torque value is output, which is used to judge the assembly quality of the current crankshaft.

In engineering, the quantitative judgment of the abstract evaluation index of crankshaft assembly quality can be realized, and the actual measurement value can provide the basis for judging the health status of the shaft system. The algorithm and control logic are described in detail, and the initial development trend of several abnormal phenomena can be judged through the measurement of the drag torque. The specific processing procedure and algorithm based on measurement data are given, and the entire core algorithm based on hardware is integrated. The invention provides an inspection method for the comprehensive quality evaluation after the installation of the crankshaft of the reciprocating engine, which intervenes in advance in the quality monitoring process of the core process of the installation of the crankshaft according to the quantitative index, and improves the pass rate of one off-line.

Description of drawings

Figure 1 is a measurement diagram of crankshaft starting torque,

Figure 2 is a measurement diagram of the average torque of the crankshaft,

Figure 3 is a measurement diagram of the maximum torque of the crankshaft,

Fig. 4 is the front view of the present invention,

Fig. 5 is a perspective view of the present invention.

In the figure, 1. Servo motor, 2. Torque sensor, 3. Docking interface, 4. Control cylinder, 5. Motor mount, 6. Linear guide rail, 7. Support plate, 8. Cylinder support frame, 9. Bearing seat.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings.

As shown in Figures 1-3, the process parameters and data samples involved in this algorithm are derived from a certain type of diesel engine TBD620. For other types of engines, because the fit gap between the crankshaft and the bearing bush is generally in the range of 0.12-0.21 mm, which is a standard design gap, the calculation method involved in the present invention is applicable to most engines.

A method for measuring the assembly quality of a reciprocating engine crankshaft, comprising the following steps:

S1: Install the crankshaft: Confirm that the straightness, roundness, and size of the main journal of the crankshaft to be installed and the main shaft hole of the engine cylinder meet the technical requirements of the specification; apply lubricating oil evenly on the surface of the upper and lower crankshaft bearing bushes, and slowly drop the crankshaft to the main shaft In the hole, tighten the main bearing cap according to the process torque; in order to stabilize the friction damping of the shaft system, it is necessary to manually pre-crank 4-6 turns in advance to form a uniform oil film between the crankshaft and the bearing bush, so that the subsequent measurement steps can be obtained Accurate drag torque value;

S2: The measuring device is hoisted on the KBK truss, the control system commands the control cylinder 4 of the guiding mechanism to drive the measuring mechanism to move towards the crankshaft, and connects with the coaxial flywheel end of the engine, that is, the docking interface 3 is docked with the output flange of the crankshaft, and starts After the measuring mechanism drives the crankshaft of the engine to rotate, the starting torque, average torque and maximum torque of the crankshaft are respectively collected:

Measurement of starting torque: Increase the rotation speed of the measuring device from 0r/min to 30r/min within 5s, and measure the maximum driving torque of the crankshaft from stationary to rotating. The torque reflects the degree of compression and lubrication of the crankshaft and bearing bush. The starting torque is the momentary torque of the crankshaft from rest to motion, and it tends to decrease as the rotation speed increases. In order to ensure the accuracy of the measurement, the torque usually needs to be measured several times repeatedly, and this embodiment continuously collects 3-5 times; the actual measurement is shown in Figure 1, and it can be seen from the graph that the maximum torque is 2.73 to 4.61 N .m interval.

Measurement of average torque: the measuring device drives the crankshaft to rotate from a static state, and when the rotation speed reaches 180r/min, it keeps rotating at a constant speed for 10s, and continuously collects the maximum torque at this constant speed state for 10 times; the average torque reflects the crankshaft assembly Quality, flexibility of main journal and bearing shell rotation, motion characteristics of crankshaft and thrust mechanism friction; actual measurement is shown in Figure 2, and it can be seen from the graph that the average torque is in the range of 3.53 to 3.92 N.m .

S3: Maximum torque measurement: the maximum torque detected during the torque measurement process, such as the bearing bush assembly "wrong", the tile edge may have been scratched with the crank, at this time the measured data will suddenly increase sharply; during the measurement process If the torque variation exceeds 2 N.m (the actual measurement result is shown in Figure 3), the protection strategy should be triggered and the measurement should be stopped to find out the specific reason.

Processing of measurement data: For different types of engines, under the premise of ensuring that various quality parameters such as fit gaps are under control, the crankshaft drag torque value is collected many times, and the starting torque and average torque measured in step S2 are constrained by SKEW and KURT functions and the skewness and kurtosis of the maximum torque data; the processed measurement data is generated into a sample space and processed as follows:

(驱动扭矩N.m)：Take the mean of the measured data

(Drive torque Nm):

Continue to calculate the sample variance S ² and standard deviation S under the premise of the mean:

为样本均值，n为样本例数；S ² is the sample variance, S is the sample standard deviation, (N ₁ , N _{2 .......} N _n ) is a random variable,

is the sample mean, n is the sample number;

(68.26％)范围内作为判断依据，此处σ为总体标准差，划定曲轴冷态拖动扭矩的具体量化范围。再使用NORMDIST函数计算出采样单值的正态分布概率密度、COUNTIF函数计算出采样单值的出现频率；To build a normal distribution model, in

(68.26%) range as the basis for judgment, where σ is the overall standard deviation, delineating the specific quantification range of the crankshaft cold-state drag torque. Then use the NORMDIST function to calculate the normal distribution probability density of the sampling single value, and the COUNTIF function to calculate the occurrence frequency of the sampling single value;

S4: Quantitative judgment method for engine crankshaft assembly quality: According to the value collected in step S3, if the crankshaft is installed during the installation process, if the main bearing cap is pressed unevenly or the bolt tightening torque is unqualified, it may cause the crankshaft rotation to measure the starting torque. large difference. In the actual installation process, the double-axis tightening equipment is used to tighten the two strong bolts on the same main bearing cap synchronously, which can obtain a relatively consistent tightening torque and eliminate the stress caused by the non-synchronous tightening of the strong bolts. The pressing force of the main bearing cap and the crankshaft is consistent, and the measurement result of the starting torque fluctuates less during the actual measurement process;

If the difference between the maximum torque and the minimum torque is too large, exceeding 5N.m, it means that there are "high points" and "low points" in the rotation process between the shaft systems, that is, the matching coaxiality between the multi-speed spindle hole and the crankshaft If it is out of tolerance, it means that the engine crankshaft assembly quality is unqualified, and the engine block or crankshaft needs to be repaired.

The average torque can reflect the pros and cons of assembly consistency, but poor consistency does not necessarily affect the reliable operation of the engine, because a certain process gap is allowed between the shaft and the bearing bush. Under the premise of a relatively appropriate fit gap, the average torque can be is a range. Similarly, if the range is smaller, it reflects that the consistency of assembly is higher and the quality control is more assured.

The relationship between starting torque, maximum torque and average torque: It can be seen from the statistical data that the normal distribution model is satisfied within the ±σ interval, the average torque is between 3.53 and 3.92 N.m, and the starting torque is distributed between 2.73- Between 4.61 N.m is a qualified state. According to the distribution of these data, the optimal rotation torque distribution range of the engine can be obtained, so as to obtain the method of controlling the engine assembly level, because on the premise that the assembly clearance meets the process requirements, three The smaller the torque difference, the better the machining accuracy of the engine main shaft hole, the more appropriate the clearance between the selected bearing bush and the crankshaft, and the more efficient the obtained oil film and lubrication, so it can be judged that the health of the shaft system is better; on the contrary, if it is not controlled If the machining and assembly quality of the crankshaft is limited, the fluctuation of the rotational torque obtained will be extremely large.

An automatic measuring mechanism for crankshaft assembly quality of a reciprocating engine, including a guiding mechanism, a measuring mechanism and a control system, the guiding mechanism includes a control cylinder, a linear guide rail and a support plate, and the control cylinder is installed on one end of the support plate through a cylinder support frame, The upper end of the support plate is provided with a sliding mounting seat matched with the linear guide rail, which is hoisted on the KBK truss, and the motor mounting seat, torque sensor bracket and bearing seat are installed on the lower part of the support plate.

The measuring mechanism includes a servo motor, a torque sensor, and a docking interface. The servo motor is connected to the support plate through a motor mount, the output shaft of the servo motor is connected to one end of the torque sensor through a coupling, and the other end of the torque sensor is connected to the torque sensor through a coupling. The second device is connected with the output shaft, the output end of the output shaft is equipped with a docking interface, and the docking interface is in clearance fit with the engine crankshaft, the torque sensor is installed on the torque sensor bracket, and the output shaft is installed on the bearing seat.

Further, the torque sensor and the docking interface are connected through a torque limiter. The function of the torque limiter is to protect the torque sensor and the servo motor. When the rotation torque is greater than the protection value of the torque limiter (the protection value can be set within a certain range), the inside of the torque limiter will automatically fall off, and the motor will run idling, thus playing a role Protective effects. The torque limiter works normally after manual reset. A reducer can be arranged between the servo motor 1 and the shaft coupling one.

During measurement, under the constraints of the linear guide rail, the control system pushes the automatic measuring device to the output side of the engine crankshaft by controlling the cylinder 4, and manually connects the docking interface 3 of the automatic measuring mechanism to the crankshaft of the engine, and connects it reliably. The servo motor 1 for drag torque detection starts to work according to the rotation speed set by the program, and the crankshaft is driven to rotate by the torque sensor 2, and the torque sensor 2 records the torque data. After the measurement is completed, the cylinder 4 is controlled to work, the measuring mechanism moves to the retreat position, the crankshaft is separated from the measuring mechanism, and the detection is completed.

Claims (6)

1. A method for measuring the assembling quality of a crankshaft of a reciprocating engine is characterized by comprising the following steps:

s1: installing a crankshaft: selecting a crankshaft meeting the process specification requirement, installing the crankshaft into a main shaft hole of an engine, and screwing a main bearing cover;

s2: the control system commands the guide mechanism to drive the measuring mechanism to move towards the crankshaft direction, a butt joint interface (3) of the measuring mechanism is in butt joint with the output end of the crankshaft, and after the measuring mechanism is started to drag the crankshaft of the engine to rotate, starting torque, average torque and maximum torque of the crankshaft are respectively collected:

measurement of starting torque: continuously collecting the maximum torque in the state for 3-5 times when the rotation speed of the crankshaft is increased from 0r/min to 30r/min from the time of 5s from the static state to the rotation state;

measurement of mean torque: the crankshaft starts to rotate from a static state, when the rotating speed of the crankshaft reaches 180r/min, the crankshaft keeps rotating at a constant speed for 10s, and the maximum torque in the state is continuously collected for 10 times;

measurement of maximum torque: if the measured value of the torque suddenly and rapidly increases in the rotation process of the crankshaft, acquiring the maximum torque at the moment;

s3: processing the measurement data: skewness and kurtosis of the starting torque, the average torque and the maximum torque measured in the step S2 are constrained by using SKEW and a KURT function,

and generating a sample space by using the processed measurement data and processing the sample space as follows:

taking the sample mean value of the measured data

(drive torque n.m):

after taking the sample mean value

On the premise of calculating the sample variance S ² ：

S ² Is the sample variance, (N) ₁ ，N ₂ ...... _. N _n ) Is a random variable and is used as a reference,

is the sample mean value, and n is the sample number;

calculating a sample standard deviation S:

establishing a normal distribution model in

(68.26%) range as the judgment basis, and demarcating the concrete quantitative range of the crankshaft cold state dragging torque;

then normal distribution probability density of the sampling single value is calculated by using a NORMDIST function, and the occurrence frequency of the sampling single value is calculated by using a COUNTIF function;

s4: the method for judging the assembling quality of the engine crankshaft comprises the following steps: according to the numerical value obtained in the step S3, if the difference value between the maximum torque and the minimum torque is less than 5N.m, the assembly quality of the engine crankshaft is qualified, and the measurement is finished;

and if the difference value between the maximum torque and the minimum torque exceeds 5N.m, indicating that the assembling quality of the engine crankshaft is unqualified, and skipping the measurement program to the step S1.

2. The method as claimed in claim 1, wherein the tightening of the main bearing cap in step S1 is performed by using a double-shaft tightening device to simultaneously tighten two strong bolts of one main bearing cap.

3. The method of claim 1, wherein the crankshaft is manually pre-turned for 4-6 turns after the main bearing cap is assembled and tightened in step S1.

4. An automatic measuring mechanism for reciprocating engine crankshaft assembling quality is characterized by comprising a guide mechanism, a measuring mechanism and a control system,

the guide mechanism comprises a control cylinder (4), a linear guide rail (6) and a support plate (7), the control cylinder (4) is installed at one end of the support plate (7) through a cylinder support frame (8), the upper end of the support plate (7) is provided with a sliding installation seat matched with the linear guide rail (6), the linear guide rail (6) is hoisted on the KBK truss, the lower end of the support plate (7) is provided with a motor installation seat (5), a torque sensor support and a bearing seat (9),

the measuring mechanism comprises a servo motor (1), a torque sensor (2) and a butt joint interface (3), wherein the servo motor (1) is connected with a supporting plate (7) through a motor mounting seat (5), an output shaft of the servo motor (1) is connected with one end of the torque sensor (2) through a first coupler, the other end of the torque sensor (2) is connected with the output shaft through a second coupler, the butt joint interface (3) is installed at the output end of the output shaft, the butt joint interface (3) is in clearance fit with a crankshaft of an engine, the torque sensor (2) is installed on a torque sensor support, and the output shaft is installed on a bearing seat (9).

5. The automatic measuring mechanism of reciprocating engine crankshaft assembly quality according to claim 4, characterized in that torque sensor (2) and docking interface (3) are coupled through a torque limiter.

6. The automatic measuring mechanism of the assembly quality of the crankshaft of the reciprocating engine according to claim 4 or 5, characterized in that a reducer is arranged between the servo motor (1) and the first coupling.

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