Special Issue Article
Variable-capacity matching of continuously variable-capacity double-impeller torque converter applied to a loader
Advances in Mechanical Engineering 2017, Vol. 9(2) 1–11 Ó The Author(s) 2017 DOI: 10.1177/1687814017690694 journals.sagepub.com/home/ade
Wen-Xing Ma1, Wen Xu2,3, Wei Cai1 and Li-peng You1
Abstract Variable-capacity matching of continuously variable-capacity double-impeller torque converter applied to a loader was studied in the article. Static variable-capacity matching of continuously variable-capacity double-impeller torque converter was performed under the two-impeller state and slipping state. Dynamic variable-capacity matching based on the Vshaped operating cycle was simulated in order to reflect the matching performance of the double-impeller torque converter more intuitively. The working speed of double-impeller torque converter together with engine was analyzed when the loader shoveled different materials, and the power performance and fuel economy of the whole machine were calculated. The continuously variable-capacity double-impeller torque converter applied to a loader could not only meet the requirements of matching different loader working conditions but also enhances the power performance and fuel economy of the whole machine in running condition compared with the original torque converter. Keywords Continuously variable capacity, double-impeller torque converter, loader, variable-capacity matching
Date received: 30 January 2016; accepted: 27 December 2016 Academic Editor: Roslinda Nazar
Introduction Currently, the capacity characteristics of torque converter (TC) of loader are invariable, and the matching performance of this kind of TC cannot achieve ideal results simultaneously in running condition and shovel mucking condition.1 In order to improve the power performance, the matching technology of a loader has received increasing concerns, which been widely studied in recent years.2 Variable-capacity matching technology has received wide attention, and variable-capacity matching can meet the matching requirements of a loader under different working conditions. Traditional double-impeller TC has two capacity states: singleimpeller and two-working-impeller states, but its capacity cannot change continuously. The doubleimpeller TC discussed in this article has continuously
variable-capacity characteristics. Double-impeller TC is not only adapted to the complex working conditions of the loader but also shows the advantage in fuel consumption. The study on the capacity matching of a loader started relatively earlier and achieved theoretical and technical results.3 Variable-capacity matching also had been studied on some level. For example, in order to 1
College of Mechanical Science & Engineering, Jilin University, Changchun, China 2 Dongfeng Automobile Co., Ltd, Guangzhou, China 3 Dongfeng Nissan Passenger Vehicle Company, Guangzhou, China Corresponding author: Wei Cai, College of Mechanical Science & Engineering, Jilin University, Changchun 130022, China. Email:
[email protected]
Creative Commons CC-BY: This article is distributed under the terms of the Creative Commons Attribution 3.0 License (http://www.creativecommons.org/licenses/by/3.0/) which permits any use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access pages (https://us.sagepub.com/en-us/nam/ open-access-at-sage).
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Figure 1. Engine universal characteristics. Figure 3. The whole structure of double-impeller torque converter. 1: wheel cover; 2: turbine T; 3: auxiliary impeller B2; 4: slip clutch; 5: stator seat; 6: turbine shaft; 7: main gear of oil pump; 8: clutch housing; 9: main impeller B1; 10: stator.
Figure 2. Engine external characteristics.
solve the wheel sliding problem during spading, doubleimpeller TC was applied to the loader (CAT988B, 992B, and 992C) by Caterpillar. Then, the research about continuously variable matching is less at home and abroad.
Figure 4. Relationship between auxiliary impeller torque and clutch slip ratio.
Engine characteristics The engine universal characteristics and external characteristics can reflect its comprehensive performance. Variable-capacity matching between engine and double-impeller TC was studied in this article. The engine universal characteristics and external characteristics of an engine are, respectively, shown in Figures 1 and 2. The rotation speeds under the maximum power, rated power, and the lowest fuel consumption are, respectively, 1800, 2100, and 1600 r/min. In order to make the most of engine power and give attention to fuel economy simultaneously, the optimum speed should be close to 1800 r/min when the engine works together with TC.
Double-impeller TC and its characteristics According to the combined degree of slip clutch, the working state of double-impeller TC is divided into three types: two-working-impeller state, single-workingimpeller state, and slipping state.4 The two-workingimpeller state shows the following characteristics. First, slip clutch is combined completely. Second, the main impeller and auxiliary impeller rotate at the same speed and both impellers transmit power. Under the slipping state, slip clutch is combined partly and the auxiliary impeller transmits the lower power than that under the two-working-impeller state while working together with the main impeller. The single-working-impeller state
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shows the following characteristics. First, slip clutch is separated completely. Then, auxiliary impeller enters the idling state without transmitting power and only the main impeller transmits power. Figure 3 shows the whole structure of doubleimpeller TC. The main impeller and the auxiliary impeller work together mainly through slip clutch.5–7 Working torques of each wheel are determined by slip ratio and speed ratio. When the value of slip ratio is 0, double-impeller TC works under the two-workingimpeller state. When the value of slip ratio is greater than 0, double-impeller TC working state is converted from two-working-impeller state into the slipping state, but the value of slip ratio cannot increase without limit under the slipping state. When the value of slip ratio rises to the value of idling slip ratio, auxiliary impeller will be idling without transmitting torque and then double-impeller TC will enter the single-workingimpeller state. As shown in Figure 4, if the value of slip ratio continues to rise, auxiliary impeller will transmit negative torque. As the negative torque has an adverse impact on the loader, it will not allow the auxiliary impeller to transmit the negative torque. Therefore, the idling slip ratio value is the maximum slip ratio. The speed ratio and slip ratio are calculated as follows
i = nnB1T d = 1 nnB2 B1
ð1Þ
where i is the speed ratio; d is the slip ratio; nB1 is main impeller speed, r/min; nB2 is auxiliary impeller speed, r/min; nT is turbine speed, r/min. Original characteristics of double-impeller TC in slipping state are shown in Figure 5. Torque ratio, efficiency, and impeller torque coefficient of doubleimpeller TC vary continuously with speed ratio and slip ratio. With an increase in the slip ratio, torque ratio and efficiency increase under the low-speed ratio and decrease under the high-speed ratio. Then, impeller torque coefficient decreases in the whole speed ratio range. Original characteristics of double-impeller TC under the two-working-impeller state and single-workingimpeller state are shown in Figure 6. Compared with the single-working-impeller state, the larger impeller torque coefficient, the higher efficiency, and the larger torque ratio are shown under the high-speed ratio in the two-working-impeller state. The larger impeller torque coefficient, the lower efficiency, and the smaller torque ratio are shown under the low-speed ratio. By analyzing original characteristics of doubleimpeller TC under two-working-impeller state, singleworking-impeller state, and the slipping state, the highest efficiency and impeller torque coefficient appear in the high-speed ratio arrange under the two-workingimpeller state. Therefore, the capacity characteristics of
Figure 5. Original characteristics in slipping state: (a) torque ratio K, (b) efficiency h, and (c) impeller torque coefficient lB.
double-impeller TC under the two-working-impeller state could meet the matching requirements of a loader in running conditions. When the double-impeller TC works under the slipping state, high efficiency and the small impeller torque coefficient appear in the low-speed ratio arrange. The capacity can be varied continuously by adjusting the slip ratio. Therefore, capacity characteristics of doubleimpeller TC under the slipping state could meet the
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Figure 6. Original characteristics in two-working-impeller state and single-working-impeller state.
matching requirements of a loader in shovel mucking condition. When the double-impeller TC works under the single-working-impeller state, the torque ratio is higher and the impeller torque coefficient is lower in the low-speed ratio arrange, which is suitable to solve the problem of tire slippage in shovel mucking condition.
Analysis of static variable-capacity matching characteristics Matching characteristics based on typical working conditions may be used to analyze the matching performance of a TC.8,9 After a loader was equipped with double-impeller TC, a static variable-capacity matching was conducted on a loader in running condition and shovel mucking condition (dry sand). At the same time, the matching performance of double-impeller TC under the two-working-impeller state and slipping state was analyzed particularly. In this article, the situation of tire slip was avoided, so the performance of doubleimpeller TC under the single-working-impeller state was not analyzed.
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Figure 7. Engine net torque.
The analysis results of original characteristics of double-impeller TC indicate that the two-workingimpeller state is the most appropriate for running condition and that the slipping working state is the most appropriate for shovel mucking condition. Co-work input features between engine and TC in the running condition and shovel mucking condition are, respectively, shown in Figures 8 and 9. Impeller load characteristics of double-impeller TC under the two-workingimpeller state are different from that under the slipping state, but impeller load characteristics of the original TC are unchanged. By analyzing co-work points between engine and double-impeller TC, it is showed that co-work speed in high-speed ratio range is lower in running condition. Therefore, the engine works in the high-power region and the low fuel consumption region. When the loader worked in shovel mucking condition, co-work input characteristics show little difference and co-work speed is close to 1800 r/min in low-speed ratio, which meets the matching requirement of the loader in shovel mucking condition.
Analysis of common working output characteristics Analysis of common working input characteristics The net torque of the engine is shown in Figure 7 when the loader works in running condition and shovel mucking condition. The shovel mucking condition involves three different materials: soft soil, dry sand, and gravel. In this article, the slip clutch was controlled according to three different rules, and three different capacity characteristic curves of double-impeller TC were obtained. The three capacity characteristic curves could be selected through adjusting material mode switch. The material mode switch was placed at optimum position 2 when the loader shoveled dry sand.
Co-work output characteristics in running condition and shovel mucking condition are, respectively, shown in Figures 10 and 11. In these figures, solid lines represent double-impeller TC and dotted line represents the original TC. Double-impeller TC shows different characteristics from the original TC. In running condition, turbine torque TT and turbine power PT are significantly increased, and engine fuel consumption ratio is decreased obviously. In shovel mucking condition, cowork output characteristics of double-impeller TC and original TC show little difference. Co-work input and output characteristics in running condition and shovel mucking condition were analyzed. The original TC mainly meets the matching
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Figure 8. Co-work input characteristics in running condition: (a) original TC and (b) double-impeller TC.
Figure 9. Co-work input characteristics in shovel mucking condition: (a) original TC and (b) double-impeller TC.
requirement of the loader in shovel mucking condition. Compared with original TC, double-impeller TC shows the basically unchanged matching performance in shovel mucking condition and the significantly improved matching performance in running condition.
Analysis of shovel mucking condition for different materials Capacity characteristics of the original TC are invariable. However, capacity characteristics of doubleimpeller TC can vary continuously under the slipping state, which can meet the matching requirements of the loader based on different materials in shovel mucking condition. In this article, capacity characteristics of double-impeller TC were divided into three kinds and controlled by material mode switch. When the loader shovels different materials, impeller load characteristics are different, thus leading to the change of co-work speed. Therefore, the matching performance of TC in shovel mucking condition might be gained according to co-work speed in low-speed ratio.10,11
Figure 10. Co-work output characteristics in running condition.
The co-work speed in shovel mucking condition is shown in Figure 12. The loader shovels, respectively, soft soil, dry sand, and gravel. When the loader shovels
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Figure 11. Co-work output characteristics in shovel mucking condition.
a certain material, the material mode switch is, respectively, placed at three different locations, and three different kinds of matching results are obtained. The results showed that capacity characteristics of the original TC were fixed and one matching result was obtained for a certain material. However, capacity characteristics of double-impeller TC might be selected by material mode switch and three different matching results were obtained for a certain material. Compared with original TC, double-impeller TC shows the same co-work speed (1800 r/min) when the loader shoveled soft soil in low-speed ratio range; when the loader shovels dry sand, the co-work speed of double-impeller TC is closer to 1800 r/min than that of the original TC; when the loader shovels gravel, the common working speed of double-impeller TC is significantly closer to 1800 r/min than that of the original TC, which shows the matching between the engine and TC is more reasonable.
Simulation of dynamic variable-capacity matching In order to reflect the matching performance of loader more intuitively, dynamic variable-capacity matching simulation model of the engine and double-impeller TC is established to simulate the V-shaped operating cycle.11–13 The dynamic variable-capacity matching principle of double-impeller TC is shown in Figure 13. Some parameters should be obtained before the simulation: the engine throttle opening (a) in every moment, deducted torque Tk, the rotational speed rate of TC i, working device state switch S1, material model switch S2, sliding mode switch S3, and so on. The engine net torques were obtained with the signals of a and Tk, and impeller load characteristics of double-impeller TC were obtained with the signals of i, S1, S2, and S3. Some parameters were calculated with several common working points
Figure 12. Co-work speed comparison of three kinds of materials: (a) soft soil, (b) dry sand, and (c) gravel.
between the engine and double-impeller TC, such as engine power Pe, impeller power PB, hydraulic system power Py, and instantaneous fuel consumption rate ge.10 In the practical operation, the loader conditions can be judged according to the outlet pressure of working
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Figure 13. Theory of dynamic variable matching.
impeller, and the working state of double-impeller TC can be changed through adjusting working device state switch S1 to adapt the current operating conditions of the loader. Meanwhile, according to different materials, appropriate capacity characteristic curve of doubleimpeller TC may be selected by adjusting material model switch S2. Therefore, capacity characteristics of double-impeller TC can vary continuously with the operating condition by adjusting the working device state switch S1 and material model switch S2.
Figure 14. Simulation model of dynamic variable matching.
Establishment of simulation model The dynamic variable-capacity matching simulation model established with Simulink is shown in Figure 14. The simulation model is mainly composed of TC module, matching calculation module, engine module, input and output signal module, and so on. Dynamic matching simulation model of original TC was also established. Compared with dynamic variable-capacity matching simulation model of the double-impeller TC, dynamic matching simulation model of original TC does not have the three parameters: the signal of working device state switch S1, the signal of material model switch S2, and the signal of sliding mode switch S3.
Preparation of simulation input signal In the V-shaped operating cycle, the parameters including the opening level of the throttle, the loss torque, and the speed ratio are varied dynamically. As shown in Figure 15, the time course of the input signal in a typical V-shaped operating cycle was formulated based on the tested data obtained when a loader shoveled dry sand.4 Dynamic matching simulation was carried out in the situation that loader shovels muck medium material without considering tire slide. Material model switch S2 was placed at position 2 and remained unchanged in the whole operation cycle. Moreover, sliding mode switch S3 was placed at the closed position. Regardless of the skid, the sliding mode switch S3 was not provided and the two signals are not expressed in Figure 15.
Figure 15. Input signal.
Analysis of simulation results The results of dynamic variable-capacity matching simulation are shown in Figures 16–22. In these figures, the solid lines represent double-impeller TC and dotted line represents the original TC. Compared with original TC, the performance of load-installed double-impeller TC is improved. For example, in stages V1, V3, and V6 in running condition, impeller torque, engine power, impeller power, and turbine power increase significantly; engine speed reduces and the engine tends to work in low fuel consumption area; hydraulic system power is not changed obviously. In stages V1 and V4 in shovel mucking condition, the above parameters are unchanged. Stage V5 (unloading) is beyond consideration. The above results show that when the loader is equipped with double-impeller TC, the matching performance of the loader is improved obviously in running condition and remains unchanged almost in shovel mucking condition.
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Figure 18. Impeller power. Figure 16. Impeller torque.
Figure 19. Turbine power.
Figure 17. Engine power.
Calculation of machine power performance and fuel economy Static and dynamic matching of original TC and doubleimpeller TC were analyzed in this article. Compared with original TC, the matching performance–installed double-impeller TC is unchanged in shovel mucking condition (dry sand) and significantly improved in running condition. Therefore, machine power performance and fuel economy of the loader are calculated in running condition.14,15
Calculation of machine power performance Loader traction characteristics are shown in Figure 23, and the acceleration variation of the loader along with the speed under each gear is shown in Figure 24. Acceleration time required in 100 m is shown in Figure 25. In the figure, solid lines represent doubleimpeller TC and dotted line represents the original TC. Compared with original TC, double-impeller TC allows
Figure 20. Instantaneous fuel consumption.
the increased traction of the loader under the same gear and the maximum traction value is 271 kN, which was 14.83% higher than that of the original TC, 236 kN. Moreover, double-impeller TC allows the increased acceleration under the same gear and the maximum speed is 42.61 km/h, which was 7.85% higher than that of the original TC, 39.51 km/h. Double-impeller TC
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Figure 21. Engine speed.
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Figure 23. Loader traction characteristics.
Figure 24. Loader acceleration curve. Figure 22. Hydraulic system power.
allows the decreased acceleration time of the loader required in 100 m, 14.25 s, which was 7.95% less than that of the original TC, 15.48 s. By comparing three power performance indicators including maximum traction, maximum speed, and acceleration time, the power performance of loader equipped with double-impeller TC is improved more than that of the original machine.
Calculation of machine fuel economy Constant-speed fuel consumption of 100 km under gear 3 and gear 4 is shown in Figure 26. Solid lines represent double-impeller TC and dotted line represents the original TC. Compared with the loader equipped with original TC, the loader equipped with double-impeller TC allows the speed of 15 km/h (gear 3), the constant-speed fuel consumption of 100 km was 118.5 L/100 km, which was 5.95% less than that of the loader equipped with original TC, 126.0 L/100 km. When the loader equipped
Figure 25. Range—accelerate time.
with double-impeller TC drives at the speed of 30 km/h (gear 4), constant-speed fuel consumption of 100 km of the loader was 101.1 L/100 km, which was 5.78% lower than that of the loader equipped with original TC, 107.3 L/100 km. The results show that the fuel economy in running condition is improved significantly when the loader is equipped with double-impeller TC.
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Advances in Mechanical Engineering Through the calculation of maximum traction force, maximum speed, acceleration time, and fuel consumption per 100 km of the whole machine, it will be found the loader equipped with double-impeller TC shows that the loader’s power performance and fuel economy have improved significantly. Declaration of conflicting interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This project was supported by the Key Technology for Earth-Moving Machinery Powertrain Design in whole life cycle of China (2014AA041502).
References
Figure 26. Loader uniform 100 km fuel consumption: (a) gear 3 and (b) gear 4.
Conclusion A static variable-capacity matching on the loader and dynamic variable-capacity matching based on the V-shaped operating cycle were conducted in the running condition and shovel mucking condition (dry sand). The original TC mainly meets the matching requirement of a loader in shovel mucking condition. The loader equipped with double-impeller TC shows the basically matching performance keeps invariable in shovel loading condition, and the matching performance is improved significantly in running condition. In a word, double-impeller TC can satisfy the requirements of two kinds of typical working conditions. The co-work speed in shovel mucking condition was analyzed when the loader, respectively, shoveled soft soil, dry sand, and gravel. Capacity characteristics of the original TC are unchanged and could meet the matching requirements for shoveling soft soil and dry sand. However, the matching performance for shoveling gravel was significantly less than others. When the loader was equipped with double-impeller TC, the capacity characteristic curves might be selected by means of material model switch. The capacity characteristics of doubleimpeller TC could meet the matching requirements when the loader shoveled three different materials.
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