JB/T 7736-1995 Reliability assessment of four-wheeled agricultural transport vehicles
Some standard content:
Machinery Industry Standard of the People's Republic of China
JB/T7736-1995
Reliability Assessment of Four-wheeled Agricultural Transport Vehicles
Published on June 20, 1995
Ministry of Machinery Industry of the People's Republic of China
Implementation on January 1, 1996
JB/T7736-1995
This standard is formulated on the basis of the "Smart Measures for Product Quality Reliability Assessment of Agricultural Transport Vehicles" issued and implemented by the former Ministry of Machinery and Electronics Engineering Agricultural Machinery Department. Compared with the interim measures, there are major changes in the writing form and expression, and some adjustments and explanations have been made. This standard should be used as a supplement or specific explanation to Chapter 18 of JB/T7235-94 "Test Methods for Agricultural Transport Vehicles". Appendix A of this standard is the appendix of the standard.
This standard is proposed by the National Technical Committee for Tractor Standardization. This standard is drafted by the Luoyang Tractor Research Institute of the Ministry of Machinery Industry. The main drafters of this standard are Qian Jin, Guo Qingchen, Qi Liang, Fan Jianhua and Shang Shinian. This standard is entrusted to the Luoyang Tractor Research Institute of the Ministry of Machinery Industry for interpretation. 1 Scope
Machinery Industry Standard of the People's Republic of China
Reliability Assessment of Four-wheeled Agricultural Transport Vehicles
JB/T7736-1995
This standard specifies the definition, classification and judgment rules of the faults of four-wheeled agricultural transport vehicles (hereinafter referred to as agricultural vehicles), the reliability assessment method and test method.
This standard is applicable to the new product type test of agricultural vehicles (excluding special devices for agricultural vehicles) and the reliability assessment test of mass-produced agricultural vehicles.
2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown in the following standards are valid. All standards will be revised. All parties using this standard should explore the possibility of using the latest version of the following standards. GB 318782
GB7258-87
JB/T 7234 94
JB/T 723594
JB/T51025.1-92
3 Fault classification
Basic terms and definitions of reliability
Technical conditions for motor vehicle operation safety
General technical conditions for agricultural transport vehicles
Test methods for four-wheel agricultural transport vehicles
Product quality classification of agricultural transport vehicles
Quality grade
According to the degree of harm caused by agricultural vehicle faults and the difficulty of troubleshooting, faults are divided into fatal faults, serious faults, general faults and minor faults. Their categories, codes and classification principles are shown in Table 1. Table 1 Classification of agricultural vehicle faults
Fatal faults
Serious faults
General faults
Minor faults
4 Fault judgment rules
Classification principles
Threatening driving safety or causing personal injury or death, or causing the scrapping of major assemblies and causing major economic losses. Faults that affect driving safety, or cause important assemblies or parts to fail, and the specified important performance exceeds the limit, requiring shutdown for repairs, and the repair cost is high, and cannot be eliminated within a relatively short effective time (usually requires Faults that require disassembly of the machine body for repair and can only be eliminated) obviously affect normal use, or the specified performance exceeds the limit, and no important assembly or parts need to be replaced, and can be eliminated within a short effective time (usually occurring on external parts), or defects that obviously affect the appearance slightly affect normal use, generally will not cause suspension or performance degradation, and the repair cost is low, and the faults that can be easily eliminated by the on-board workers, or defects that slightly affect the appearance. When evaluating the reliability of agricultural vehicles, each fault that occurs during use should be counted and judged according to the following principles. 4.1 Only the essential faults that occur are counted. If the essential fault and the subordinate fault occur at the same time, it should be recorded once as the fault with the most serious consequences. Misuse faults are not counted in the number of faults, but should be recorded truthfully. Approved by the Ministry of Machinery Industry on June 20, 1995
Implementation on January 1, 1996
Fault definitions are shown in GB3187.
JB/T7736—1995
4.2 When judging the type of fault, it should be judged by the consequences it ultimately causes, and it can only be judged as one of the four types of faults. 4.3 Adjustments and maintenance carried out according to the instructions for use and replacement of spare parts on the vehicle that are due are not considered faults, but they should be well recorded. 4.4 For faults such as "three leaks" (i.e. oil, water, and air leakage) and loose hardware, when counting the number of faults, each joint surface is counted as one time.
4.5 For the same fault that recurs after the fault is eliminated, the number of faults is counted according to the actual number of times it occurs during the test of the finalized products produced in batches; for repeated faults that occur during the type test of new products, if the fault recurs after replacing the original manufactured parts without improving the design or manufacturing process, the number of faults is counted as one time, and the mileage is counted according to the mileage when it first occurs. The rest should be recorded truthfully. 4.6 When judging the type of fault, you can refer to Appendix A (Appendix to the Standard). However, due to the different structures of various agricultural vehicles, the consequences of the same fault and the difficulty of troubleshooting will vary greatly, so it cannot be completely copied. It should be judged according to the classification principle, reference examples, and specific circumstances.
5 Reliability Assessment Method
The reliability assessment test of agricultural vehicles adopts a fixed-range tail-off test with replacement. According to the faults and related data that occurred in the fixed-range tail-off driving test of agricultural vehicles, the following indicators are calculated to evaluate its reliability. However, if a fatal fault occurs during the test, its reliability will be counted as unqualified, and it is not necessary to calculate the various indicators. 5.1 Mean First Failure Result Time MTTFF
refers to the average single-distance driving of the agricultural vehicle when the first fault occurs (except for minor faults). 5.1.1 Point estimate of MTTFF S,
[>s, +(nr)S,
Where: S—point estimate of mean first failure mileage MTTFF, km;
S—number of test vehicles with first failure (except minor failure) during the test period;
S—accumulated mileage when the first test vehicle had first failure (except minor failure), kmn—total number of test vehicles;
S—prescribed fixed-range tail test load-cutting mileage, km. If all tested agricultural vehicles reach the prescribed mileage and no failure (except minor failure) occurs, S is specified to be >nS. 5.1.2 One-sided confidence lower limit of MTTFF SnS
[s, + (nr)S,
-r)S]
Where: Sn is the one-sided confidence limit of the mean first failure mileage MTTFF, km, α is the risk coefficient, also known as the significance level, which is uniformly taken as 0.35 in this method: b is the total number of failures, which is r here; Www.bzxZ.net
is the quantile of the distribution with a confidence level of (1-α) and a degree of freedom of (26+2). When a=0.35, the values are shown in Table 2. Table 24 Values when a=0.35
Total number of failures
Total number of defects6
5.2 Average The failure interval mileage MTBF
refers to the average mileage interval between two consecutive failures (excluding minor failures) of agricultural vehicles. 2
5.2.1 MTBF point estimate S
JB/T7736—1995
Where: S, the point estimate of the mean failure interval mileage MTBF, km: (3)
B, —- the total number of failures (excluding minor failures) that occurred in n test vehicles during the fixed-range truncation test. When all the tested agricultural vehicles reach the specified When the mileage is free of faults (except for minor faults), it is stipulated that S,>\S.
5.2.2 Single-sided confidence limit of MTBF S
Where: Sr
The single-sided confidence limit of MTBF, km: 6——Total number of faults, here is r.
5.3 Comprehensive score of no fault Q
Q=100-
Where: Q--Comprehensive score of no fault·points (4)
S. —— The MTBF target value of the superior products specified in the agricultural vehicle quality classification standard is km; the current value is 4000km; ro
Total number of various types of faults;
The criticality coefficient of the th fault is specified as; Severe fault K=40
General fault K=10
Minor fault K=2
The mileage coefficient of the th fault is calculated by the following formula: 2S.
S, the cumulative mileage of the tested vehicle when the th fault occurs, km. 5.4 Average warranty cost rate pwc
Where: pwc
-Average warranty cost rate:
×100%
Zc-—The cumulative repair cost of all test vehicles during the entire test period, RMB; C,——The approved factory retail price of a vehicle, RMB. 6 Reliability test method
6.1 Test equipment and parameter measurement accuracy 6.1.1 Test equipment
Mainly includes five-wheel meter, fuel consumption meter, smoke meter, precision sound level meter, timer and steel tape measure. 6.1.2 Parameter measurement accuracy
Should meet the relevant provisions of JB/T7235.
6.2 Test sample vehicle
6.2.1 Sample vehicle requirements
Should meet the relevant provisions of GB7258 and JB/T7234. (6
6.2.2 Number of test vehicles
The number of test vehicles for each vehicle type is 2. 6.2.3 Sampling method
JB/T 77361995
During the type test of new products, the test sample vehicles shall be provided by the factory. For mass-produced agricultural vehicles, the test sample vehicles shall be supervised by the sampling personnel of the test responsible unit and shall be selected from the finished products that are normally produced and have passed the inspection and are put into storage. The sampling base shall not be less than 20 vehicles, and 3 vehicles shall be randomly selected from them, of which 2 vehicles are test vehicles and one vehicle is sealed for standby. During the surprise inspection, the sampling location and sampling base are not limited. 6.2.4 Sample delivery vehicle
The test sample vehicle shall be delivered to the test site by the factory. Each vehicle shall have a factory certificate, instruction manual, spare parts and tools, etc.
6.2.5 Use of spare vehicle
When one of the following situations occurs, the spare sample vehicle may be used with the consent of the test responsible unit: a) The sample vehicle is damaged during the sample delivery:
b) The sample vehicle is damaged by an accident or man-made accident during the test. 6.3 Test conditions
The test conditions shall meet the requirements of Chapter 3 of JB/T7235. However, considering the safety and feasibility of the test, it is uniformly stipulated that the driving test should be carried out in a temperature of -5 to 35℃, without ice, snow or fog. 6.4 Test
6.4.1 Acceptance
Acceptance shall be carried out in accordance with the items specified in Table 3, and the problems found during the acceptance shall be recorded in detail. If repair or adjustment is required, it shall be approved by the responsible unit of the test.
6.4.2 Running-in and maintenance
For the qualified sample vehicles, the running-in shall be carried out in accordance with the provisions of the instruction manual: if there is no running-in specification, the running-in can be carried out in accordance with the running-in specification recommended in Table 4, and all gears shall be used.
During the running-in driving period and the entire test period, the test vehicle shall be maintained and serviced in accordance with the provisions of the instruction manual, and the situation shall be recorded.
6.4.3 Verify odometer
According to the method specified in 4.3 of JB/T7235, verify the odometer of each test sample vehicle. 6.4.4 Performance test
Carry out the following performance tests before and after the driving test, and record the test results in Table 5. 6.4.4.1 Power performance test
Measure the lowest stable vehicle speed and the highest vehicle speed at the highest gear according to the methods specified in 7.3.1 and 7.3.2 of JB/T7235. 6.4.4.2 Braking performance
Under full load, carry out the ramp parking test and the cold braking performance test at maximum pedal operating force according to the methods specified in 12.3.1 and 12.3.2 of JB/T7235. 6.4.4.3 Fuel economy test
The test is carried out according to the method specified in 8.3.1a of JB/T7235, and the average fuel consumption of six working conditions is measured at the same speed. The difference between the actual driving speed and the required speed under each working condition should not exceed ±0.5km/h. 6.4.4.4 Environmental pollution measurement
According to the methods specified in 13.3.1, 13.3.3 and 13.3.4 of JB/T7235, the acceleration driving noise outside the test vehicle, the noise at the driver's operating position and the free acceleration smoke are measured. 6.4.5 Driving test
6.4.5.1 Driving test mileage
JB/T 7736-1995
For agricultural vehicles produced in batches, the full-load driving mileage of each test vehicle is: 10,000km for models with a maximum speed of less than 30km/h and 15,000km for other models. For new product type tests, the mileage shall be in accordance with the provisions of 18.3.3a of JB/T7235. 6.4.5.2 Driving roads
According to the provisions of 18.3.3b of JB/T7235.
6.4.5.3 Driving operations
Under the premise of ensuring safety, the vehicle shall be driven at a higher speed as much as possible. The average speed during the entire test period shall not be less than 60% of the maximum speed, of which the average speed on bad roads shall not be less than 50% of the maximum speed (for vehicles with a rated load plate of 1 t) or 40% (for vehicles with a rated load of <1 t); the night mileage shall not be less than 10% of the total mileage. Each shift or day shall be filled in according to the requirements of Table 14 and Table 15 of JB/T7235. Operate and maintain according to the requirements of the instruction manual, and do not arbitrarily adjust or change the technical status of the test vehicle. 6.4.5.4 Fault record
During the entire test process (including integration, performance test and idle running), all abnormal phenomena of the test vehicle shall be carefully observed. For all faults that occur, the fault registration form should be filled in according to the requirements of Table 16 of JB/T7235, and classified according to the provisions of Chapters 3 and 4 of this standard, and the time of occurrence and the cumulative full-load mileage of the test vehicle should be recorded. Faults that occur before the test (including performance tests before running-in and driving tests) are measured according to the zero public list: Faults that occur during performance tests after the test and are discovered during the final inspection are measured according to the test end mileage. 6.4.5.5 Termination of test
During the entire test process, if one of the two test vehicles has a fatal fault, the test is terminated and its reliability is unqualified. 6.4.5.6 Final inspection
After the test, the test vehicle should be fully inspected, and all newly discovered faults should be recorded and classified. 6.5 Test results and reports
6.5.1 Fault summary
Fill in the fault summary table for all essential faults (including performance index exceeding or deteriorating) found during the test according to the order of occurrence and the requirements of Table 17 in JB/T7235. 6.5.2 Index calculation
According to the relevant provisions of Chapter 5 of this standard, calculate the reliability index of the test vehicle and record it in Table 19 of JB/T7235. 6.5.3 Result judgment
According to the relevant provisions of JB/T51025.1, judge the reliability level of the test vehicle. 6.5.4. Report Writing
Write the test report in the following format and requirements: a) Report cover: Follow the format specified by the test standard: b) Report inner page and inspection conclusion format specified by the test standard: c) The third page of the report should follow the format shown in Figure 1: d) Report body
List the following contents in sequence:
1) Table of Contents List the main contents of the test report and their corresponding page numbers: 2) Foreword:
3) Fill in the main technical specifications of the test vehicle according to the items listed in Table 6: 4) Test conditions and test conditions:
5) The test results should include Table 3, Table 5 and JB/T7235 Table 17, Table 18, Table 19, etc.; 6) Failure mode and its impact analysis (conduct when necessary); 7) Other necessary instructions,
JB/T 7736-1995
Test vehicle appearance photo
This report is written after testing in accordance with the test method specified in Chapter 6 of JB/T7736-1995 "Reliability Assessment of Four-wheeled Agricultural Transport Vehicles". Test number:
Report writer:
Test person in charge:
Figure 1 Format of the third page of the report
Table 3 Summary of test vehicle acceptance and running-in results Transport vehicle model
Acceptance location
Test vehicle chassis number
Engine number
Manufacturer
Acceptance date
Whether the sampling registration form is consistent with the actual product
Whether there is a factory certificate and instruction manual
Chrome seals and Is the paint seal complete
Are the spare parts on the vehicle complete
Are the tools on the vehicle complete
Is the vehicle equipment complete
Are there any silicone scratches on the exterior
Are the important connecting parts tight
Is the engine running normally
Is the transmission system running normally
Is the steering system working normally
Is the braking system working normally
Is the operating mechanism working properly
Is the walking system normal
Is the electrical meter system suspension correct
Is the driver's seat glass safety glass
Matching date
Run-in mileage
Odometer correction coefficient
Brief description of the matching situation;
Remarks.
Signature of acceptance personnel:
Signature of customer service personnel:
Factory date
Test number
Cumulative mileage km
200~500
500~1000
1000~1500
Agricultural vehicle model
Power performance
Braking performance
Fuel economy
Environmental pollution control
Test date
Test additional points
High speed km/h
JB/T 7736-1995
Table 4 Test vehicle running-in specification (recommended)
Load
Manufacturer
Test items
Minimum stable speed at highest gear km/h
Test date
Test location
Whether the test vehicle moves on the test ramp
Braking distance at specified speed m
Drifting amount cm
Road surface requirements
Flat road
Flat road||t t||Uneven dirt road
Performance test results summary table
Test number
Test date
Test location
Six-condition constant speed fuel consumption rate 1/(t·100km)Test date
Test location
Accelerating barge external noise:
Noise at the driver's operating position
Free acceleration smoke Rb
Before test
Throttle opening
After test
Before test
After test
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.