WO2011039767A2

WO2011039767A2 - An engine torque damping system

Info

Publication number: WO2011039767A2
Application number: PCT/IN2010/000602
Authority: WO
Inventors: Samraj Jabez Dhinagar; Thalaku Pandian Manikandan; Srikumar Aravindakrishnan
Original assignee: M/S.Tvs Motor Company Limited
Priority date: 2009-09-30
Filing date: 2010-09-09
Publication date: 2011-04-07
Also published as: WO2011039767A3

Abstract

This invention provides an engine torque damping system for a two -wheeler with auto clutch transmission system comprising an electronic control unit (31), an engine speed sensor, a throttle position sensor, and a gear position sensor, wherein the said electronic control unit senses the engine transmission in first gear by means of said gear position sensor and throttle position beyond a predetermined first state by means of said throttle position sensor, and retards the ignition timing based on the rate of change of the engine speed.

Description

AN ENGINE TORQUE DAMPING SYSTEM

BACKGROUND OF THE INVENTION In any conventional motorcycle having a gear box, power transmission from the crankshaft to a drive shaft and finally to the wheel is achieved through a clutch and a series of reduction gears and chain drive. The gear shifting process involves disengagement of wet, multi-plate clutch, movement of shifter forks for changing gears and engagement of wet, multi-plate clutch. During the gear shifting, the rider needs to disengage the clutch by hand operated clutch lever. Hence in the manual transmission frequent operation of clutch lever and gear shift is necessitated by the rider causing discomfort especially under city traffic condition. In order to overcome this, semiautomatic manual (SMT) transmission system are used. In Semiautomatic Manual Transmission (SMT), wet clutch actuation as well as movement of shifter forks for changing gears is achieved using single mechanism. Additionally, SMT also includes a centrifugal clutch. In a SMT system, foot lever is used by the rider to shift gear. Once the rider has pressed the lever multi plate clutch is disengaged. Same gear-shift mechanism subsequently moves the gear shifting forks (not shown) and hence, shifts the gear. After this, clutch is engaged back due to wet multi-plate clutch springs. SMT system also has centrifugal clutch mounted on crankshaft. Whenever, engine or crankshaft rotational speed is below a particular threshold value, centrifugal clutch separates wet multi plate clutch and gear-box. Hence, engine does not stall. Thus, gear shift process is complete in SMT of a motor cycle. Hence use of SMT system eliminates the need for frequent operation of clutch lever (since the lever is redundant) under urban driving conditions. This gives an advantage over the manually operated clutch / gear shifting system. But however, such SMT system is predominately used in step through motorcycles incorporating horizontally mounted engines. Such step through vehicles is defined by having a step through space between the handle bar and the seat. (Refer Fig 1). Use of SMT system in motorcycles with nearly vertically mounted system in the range of 100-125 CC is unheard off. This is due to in instability especially during acceleration from the first gear in SMT motorcycle having vertically mounted engine. Motorcycles having vertically mounted engines are preferred by majority of Indian customers owing to their rugged appeal and aesthetics. Customers prefer these motorcycles for the following reasons inter alia; Comfortable seating and riding posture having the legs hugged on the side of fuel tank, thus reducing the overall fatigue; Better maneuverability over high speeds owing to longer wheel base and wider tyres.

However the customers using these of vehicles are denied of the convenience of SMT system due the above said problem of instability during acceleration from the first gear. In other words sudden acceleration in first and second gear condition generates a very high torque at the wheel, which can result in front wheel lifting. A heavy payload at the rear side of the vehicle can further aggravate the problem that may lead to accidents. However in case of a manual clutch system, the rider gradually releases the clutch in accordance with the increase in acceleration and the torque transmitted to the wheel is controlled in the first and second gear conditions. However this is not possible in case of semi-automatic manual transmission (SMT) system. Hence there is a need to address this problem so that users of such motorcycle get the benefit of the SMT system.

Also, customers using these vehicles with SMT will have to reduce the throttle during gear shifting to avoid sudden jerks. Although the clutch lever need not be depressed during gear shifting, throttle reduction is essential for vehicles with SMT. It will be comfortable for the rider if throttle reduction is not necessary during gear shifting. Then gear shifting can be done without any abnormalities even at high throttle conditions. BRIEF DESCRIPTION OF DRAWINGS

Fig.l illustrates a conventional, Two-wheeled vehicle;

Fig. 2 illustrates the perspective view of a SMT step-through two-wheeled vehicle;

Fig. 3 illustrates the gear shifting mechanism in a conventional SMT step-through vehicle;

Fig. 4 illustrates a centrifugal clutch is mounted on a crankshaft; Fig. 5 illustrates a Block diagram of the unit;

Fig. 6 illustrates the flow chart of the system;

Fig. 7 illustrates the continuation of the flow chart of the system as shown in Fig.6; and Fig. 8 illustrates the continuation of the flow chart of the system as shown in Fig.7.

DETAILED DESCRIPTION OF THE INVENTION

Any known motorcycle such as the one illustrated in Fig. 1, (straddle type), can be divided into three major portions, the front portion F, the middle portion M and the rear/tail portion R. The front portion F comprises of the steering, front wheel 1 with necessary brakes, front suspension and fender, the middle portion M comprises of the handle bar 7, fuel tank 8, rider seat 9, foot rest for both the rider and the pillion member, starter motor 3, engine 4, chain wheel drive 5, gear shift lever, stand etc and the rear/tail portion R comprises of back wheel 2, chain wheel driven 6 with necessary suspension and rear fender. In such a motorcycle, a Semi automatic transmission is used only with horizontally placed engines and the use of the same in motorcycles having nearly vertically mounted engines is not known. Fig. 2 shows a perspective side view of a SMT step-through two-wheeled vehicle 10, interchangeably referred to as SMT vehicle 10 hereinafter. Among other components, the SMT vehicle 10 as shown includes a body mounted on two wheels 1 & 2, a gear-shift lever 11, and a handlebar 7, which is usually located just above the left foot-rest. The gearshift lever 11 is operated by the left foot movement of a rider riding the vehicle 10 in order to shift gear ratio. In order to change gears, the rider releases a throttle grip (not shown in the figure), which is usually present on a right-hand side of the handlebar 7, as seen from the rider's perspective, and pushes an end of the gear-shift lever 11 from his or her left foot in downwards direction. The end of the gear-shift lever 11 to be pushed to get the desired gear ratio or a transmission equivalent to the gear ratio depends on the make of the vehicle 10 and may vary from one vehicle to another. Fig. 3 shows the working of a gear shifting mechanism 11 in a conventional SMT step- through vehicle, such as vehicle 10. The release of the throttle grip and a subsequent push at either ends of the gearshift lever 12 mounted on shaft gear shift lever 13 in a downward direction actuates a gearshift mechanism 15. The gear shift mechanism 15 first disengages a multi-plate clutch 14 and moves gear shifting forks (not shown in the figure), which are housed inside a crankcase housing of an internal combustion (IC) engine of the vehicle 10, to shift a gear. The multi-plate clutch 14 is engaged back to its normal position once a gear is shifted due to the multi-plate clutch springs 16. In this way, a gear or gear ratio is shifted or changed, thus providing a transmission ratio required for the vehicle at an instance.

Fig. 4 illustrates a centrifugal clutch is mounted on a crankshaft. This type of transmission system also includes a centrifugal clutch 19. The centrifugal clutch uses centrifugal force to connect two concentric shafts, the drive shaft nested inside a driven shaft. As shown in Fig. 4, which indicates the cross sectional view of the gear box 17. The gear box 18 has a centrifugal clutch 19 is mounted on a crankshaft 20. When the IC engine reaches a certain RPM (revolutions per minute), the centrifugal clutch 19 engages. As the load increases, the RPM drops, thus disengaging the centrifugal clutch 19, letting the RPM rise again and reengaging the centrifugal clutch 19. In addition, whenever the rotational speed of the crankshaft 20 is below a particular threshold value, the centrifugal clutch 19 separates the wet multi-plate clutch 14 and the gear-box 18 so that the engine does not stall. In conventional motorcycles with vertical engines a centrifugal oil filter 27 is mounted on the crankshaft 20 beyond primary driven gear 22 to supply clean oil to big end bearing of connecting rod (not indicated). Where as in the SMT type of transmission also a centrifugal clutch mounted on crankshaft 20 also houses centrifugal oil filter 27 supply clean oil to connecting rod big end bearing (not indicated). The gear primary driven 22 is directly connected to crankshaft 20 in conventional gear box, where as it is connected to clutch drum 21 directly in SMT transmissions. When ever the engine is started the gear primary drive 23 fitted on crankshaft 20 starts rotating the gear primary driven 23 connected to manually actuated clutch 14 being disengaged by forward movement of clutch actuator 25 connected to clutch actuating lever (not shown) mounted on clutch cover 24 fitted on drive shaft 26. In conventional gear shifting the rider has to depress the clutch operating lever fitted on handle bar to disengage the manually actuated clutch 14 .The rider then needs to operate the gear shift lever 11 which in turn rotates the shifter drum (not shown) connected to shifter forks engaged with a set of gears fitted on drive shaft 26 engages with another set of gears fitted on driven shaft (not indicated) to effect different gear ratios based on gear shift fork position (not indicated). The first gear set 28 and 29 are shown as an illustration for having different number of teeth engaged to each other. The drive sprocket 30 fitted on driven shaft 26 is connected to chain wheel fitted on rear wheel.

Fig. 5 illustrates a Block diagram of the unit. The Engine Torque Damping System of the present invention, which is designed primarily for a vertically mounted engine with auto clutch transmission system, comprises an electronic control unit 31 that receives inputs from an engine speed sensor 32, throttle position sensor 33, gear position sensor 34 and optionally from an engine temperature sensor 35. The electronic control unit provides a signal to an ignition unit 36, which in turn generates the spark through the spark plug assembly 37 in the internal combustion engine. The instant of spark generation is thus controlled by the electronic control unit. The functioning of the system can also be observed from the flowchart shown in Fig.6, in combination with Fig. 5.

In an experiment conducted on an 110CC four stroke engine whose objective is to avoid jerk in the same, the parameters listed below are found to be the optimum values for the corresponding engines. TI - 30% ; STI - 5 degrees; N - 10 Revolutions; SI - 15%; S2- 20%; Al - 100RPM; Dl - 1 degree.

The Electronic Control Unit (ECU) 31 reads the gear position signal 38 from the gear position sensor 34. Whenever there is a change in the gear position 39, the ECU 31 checks the Throttle Position Sensor (TPS) signal 40. If the TPS signal is greater than Tl% 41, then the spark ignition timing is retarded by STI degrees 42 for predetermined N engine crankshaft revolutions 43. The value of 'N' is experimentally identified for the particular engine fixed on the respective vehicle. Retarding the ignition timing thus eliminates jerks due to sudden change in engine load during gear shifting at high throttle.

As shown in Fig.7 (continuation of the flowchart as shown in Fig.6), the ECU 31 then reads the gear position signal and checks if the transmission is in 1^st Gear 50. If the transmission is in 1^st Gear 51 then the ECU reads the throttle position sensor (TPS) 52 output. If the TPS output is beyond a predetermined value (Sl%), 52 the ECU calculates the engine acceleration 54 from the engine speed sensor output 53. The ECU then retards the spark ignition timing based on a look up table 55.

If the transmission is in 2^nd Gear 56 then the ECU 31 reads the TPS output. If TPS output is beyond a predetermined value (S2%) 57, then the ECU calculates the engine acceleration 54 from the engine speed 53 sensor output. The ECU then retards the spark ignition timing 55 based on the look up table.

After retardation of the spark ignition timing for 1^st Gear or 2^nd Gear, the engine acceleration 58 is calculated and checked if the acceleration goes below a predetermined value Al 59 (Ά different for 1^st Gear and 2^nd Gear) as shown in Figure 8 (continuation of the flowchart as shown in Fig.7). If the engine acceleration goes below the predetermined value, the spark ignition timing is gradually increased 60 to the default ignition timing for the respective engine speed.

The above processes do not stop the spark ignition but only change the timing when certain conditions (mentioned above) are met. If any of the conditions are not met, the ECU continues to check the gear position from the gear position sensor signal. The checking is a parallel process (can be an interrupt controlled event) and does not stop the ECU from performing other normal engine control operations i.e., calculating engine speed, sensing engine temperature, sensing throttle position, signalling spark ignition, etc. The values in the look up table, the predetermined TPS values (Tl%, Sl%, S2%), the predetermined engine acceleration values ( refer the table given below) and the rate of ignition timing advancement Dl are all identified based on experimental data corresponding engine fixed on the corresponding vehicle.

ENGINE TORQUE DAMPING

Gear Engine Speed Engine Ignition

(rpm) Acceleration Retardation

(rpm/sec) (degrees)

1 <2000 <1000 2

1000-2000 4

2000-3000 6

>3000 8

>2000 No Change No Change

2 <2000 <2000 2

2000-3000 4

>3000 6

>2000 No Change No Change

Claims

CLAIMS:

1. An engine torque damping system for a two and three wheeled motorcycle comprising auto clutch transmission system comprising an electronic control unit (31), an engine speed sensor (32), a throttle position sensor (33), and a gear position sensor (34).

2. An engine torque damping system as< claimed in claim 1, including an engine temperature sensor (35).

3. An engine torque damping system as claimed in claim 1, wherein the said electronic control unit provides a delayed signal to an ignition unit for spark ignition in the internal combustion engine.

4. An engine torque damping system as claimed in claim 1, wherein the said electronic control unit senses the engine transmission in first gear by means of said gear position sensor and throttle position beyond a predetermined first state by means of said throttle position sensor, and retards the ignition timing based on the rate of change of the engine speed.

5. A two wheeled motorcycle including an engine torque damping system comprising auto clutch transmission system comprising an electronic control unit (31), an engine speed sensor (32), a throttle position sensor (33), and a gear position sensor (34).

A three wheeled motorcycle including an engine torque damping system comprising auto clutch transmission system comprising an electronic control unit (31), an engine speed sensor (32), a throttle position sensor (33), and a gear position sensor (34).