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1 Introduction

Nowadays people have much more requirements in vehicle performance including power, economy and safety, especially the vehicle comfort. Ride comfort and driving comfort are the two aspects in research of automobile comfort [1]. The analysis of car operating comfort mainly focuses on the pedal, driving environment and the seat [2]. Among them, quality of clutch pedal is directly related to the safety performance of the vehicle, as it is a car security part which separate or combine clutch and engine by trampling clutch pedal. In order to provide a more comfortable and easier operating clutch, the first job is to analyse the main factors influencing the clutch.

2 Analysis Factors Influencing the Comfort of Clutch Pedal

Pedal force and pedal motion stroke are the main factors influencing clutch manipulation. Main factors effecting pedal force and pedal stroke are diameter of both clutch main cylinder and sub-cylinder, leverage ratio of clutch pedal and clutch parameters.

Pedal force is definitely the force acting on the pedal by feet; joint pedal force is the main characteristics evaluating pedal comfort. Pedal motion stroke contains separating stroke and combining stroke showed in Fig. 1. Separating stroke is the travel form top limiting position to clutch separating point, while combining stroke is the pedal travel form bottom limiting position to combing point.

Fig. 1
figure 1

Schematic diagram of clutch separating system

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2.1 Motion Stroke of Clutch Pedal

A certain clutch separating bearing demands the moving distance during separating should between 7.5–8.5 mm, but there is abnormal sound when the pedal is trampling to the bottom according to road trial feedback which influences the driving comfort seriously (Fig. 2).

Fig. 2
figure 2

Schematic diagram of clutch pedal motion stroke

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Separating characteristics of this certain clutch show that total separating trip is 7.5 mm, separating point trip is about 2.4 mm, while combing point trip is not sure. Theoretical calculation is showed below in Table 1 case of separating point has the same position as combining point.

Table 1 System calculating
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Testing data of these above three schemes are showed in Figs. 3, 4, and 5.

Fig. 3
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Testing data of scheme 1

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Fig. 4
figure 4

Testing data of scheme 2

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Fig. 5
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Testing data of scheme 3

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Scheme 1 show that 134 mm total travel is much better, but the combining position is a little bit higher; scheme 2 present a worse driving comfort evaluation with no combining point and 138 total travel; while scheme give a too long total trip and higher combining position, shifting motion can go smoothly even though the pedal is not trampled during the last 20 mm trip.

2.2 Pedal Force

Combining point pedal force comfort need experienced drivers to evaluate subjectively as whether the pedal force is appropriate or not is related to drivers’ subjective sensation based on operating all sorts of devices through acting force during driving process.

84.9 N combining pedal force is accepted in scheme 1, scheme 2 gives 72.9 N pedal force, scheme 3 shows that 82.6 N pedal force is more proper through the above testing results and experienced drivers’ evaluation.

3 Conclusion

Above the theoretical calculation and practical test show that 100–125 mm separation trip is more appropriate. Clutch will separate excessively with a too short separating stroke which can lead friction between clutch diaphragm spring and clutch friction plate rivet. The proposal is presenting less than 50 mm combining stroke, too long combining stroke lead vehicles flameout easily because drivers feel the pedal combining position is too higher.

We can also conclude from the above analysis that 85–100 N combining pedal force is more suitable. The pedal can not provide enough support to feet if the pedal force is too light, while too heavy pedal force makes drivers tired easily.

Proper pedal feeling ensure driving safety, it is also the important factor influencing driving comfort that makes drivers keep steady mood and quick response to ensure driving safety and vehicle service life as well.