DESC:FIELD
The present disclosure relates to the field of mechanical engineering. In particular, the present disclosure relates to a system for controlling the valve timings in vehicle engines.
DEFINITIONS
A poppet valve is a mechanical device used to control the flow of fluid in a combustion chamber.
A cam is a rotating piece of mechanical linkage that converts the rotary motion into linear motion.
BACKGROUND
The operational opening and closing of the combustion chamber valves are controlled by rocker arms. The rocker arms are oscillating devices whose oscillations are governed by a cam lobe. The rocker arm pivots about a shaft and whose one end actuates the opening and closing of the valve while the other end follows a cam lobe profile. Typically, the valve timings for the combustion engine are fixed and controlled by means of cam and rocker arm arrangement. With the vehicle moving with differing speeds and carrying varying loads, the valves continue to operate with the same timing and lift, which results in low performance, reduced efficiency, high operating costs, and fuel wastage.
Some vehicles use a system which keeps the valves open a little longer than required, thereby allowing additional air fuel mixture into the combustion chamber when the engine is running at higher speeds. This is critical, since an engine operating at high speeds with a fixed valve timing and operating with a predetermined cam lobe profile may result in lower quantity of air fuel mixture entering the combustion chamber, thereby affecting the performance and the fuel economy.
A conventional solution to the above mentioned drawbacks involves configuring the cam lobe profile in a manner so as to allow sufficient time for the air fuel mixture to enter the combustion chamber. However, even these solutions suffer from the ill effects of exhausting unburnt fuel while the engine is running at lower speeds. Hence, there is need for a solution which would time the opening and closing of the valves in direct correlation with the speed of the engine. A further requirement of the solution includes a system that would allow sufficient time for the air fuel mixture to enter the combustion chamber.
OBJECTS
Some of the objects of the system of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide a system for controlling valve timings in vehicle engines which improves the performance and fuel economy of the vehicles.
Another object of the present disclosure is to provide a system for controlling valve timings in vehicle engines which automatically adjusts the valve timings with the speed and load on the vehicle.
Yet another object of the present disclosure is to provide a system for controlling valve timings in vehicle engines which is reliable.
A further object of the present disclosure is to provide a system for controlling valve timings in vehicle engines which facilitates adequate time for opening and closing of the valves to allow adequate quantity of air fuel mixture to enter the combustion chamber.
Another object of the present disclosure is to provide a system for controlling valve timings in vehicle engines which avoids unburnt fuel to escape through the exhaust port.
Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure envisages a system for controlling valve timings in a vehicle engine, comprising a first rocker arm configured to perform the opening and closing of an exhaust valve. The system further comprises a second rocker arm configured to perform the opening and closing of an intake valve when the vehicle engine is operating at or below a first speed, and a third rocker arm configured to perform the opening and closing of the intake valve when the vehicle engine is operating at or above a second speed. The system further comprises a camshaft having three lobes configured thereon. A first lobe is functionally coupled with the first rocker arm and configured to perform a controlled oscillation of the first rocker arm. A second low-speed lobe is functionally coupled with the second rocker arm and configured to perform a controlled oscillation of the second rocker arm, thereby allowing the intake valve to be in open configuration for a first period of time. A third high-speed lobe is functionally coupled with the third rocker arm and configured to perform a controlled oscillation of the third rocker arm, thereby allowing the intake valve to be in open configuration for a second period of time. The system further comprises a coupling mechanism adapted to couple the third rocker arm with the second rocker arm, thereby enabling the third rocker arm to govern the opening and closing of the intake valve when the vehicle engine is operating at or above the second speed.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
A system for controlling valve timings in vehicle engines of the present disclosure will now be described with the help of the accompanying drawings, in which:
Figure 1 illustrates a top view of the system for controlling valve timings in vehicle engines in accordance with an embodiment of the present disclosure;
Figure 2a illustrates the front view of the system of Figure 1;
Figure 2b illustrates the front view of the system of Figure 1 with the pin not engaged;
Figure 2c illustrates the front view of the system of Figure 1 with the pin engaged;
Figure 3a illustrates an isometric view of the camshaft with three lobes of the system of Figure 1; and
Figure 3b illustrates a front view of the camshaft with three lobes of the system of Figure 1.
DETAILED DESCRIPTION
A preferred embodiment of the system for controlling valve timings in vehicle engines of the present disclosure will now be described in detail with reference to the accompanying drawings. The preferred embodiment does not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The following description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
The key disadvantages of the traditional system of valve timing are low efficiency, low performance, and low fuel economy. The traditional system lacks a direct correlation between the valve timings, the speed, and load on the vehicle. Also, in case of a fully electronic valve timer, wherein individual cam lobes are independently activated by the Electronic Controller Unit (ECU), the system relies on the dependability of the ECU that is larger in size besides being expensive. In case of a fully mechanical valve timer, the system is bulky and requires frequent maintenance. Hence there is a requirement for a system with variable valve timing which takes the advantage of a mechanical device coupled with an ECU.
Referring to the accompanying drawings, the system for controlling valve timings in vehicle engines as illustrated in Figures 1, 2a, 2b, and 2c is generally represented with the reference numeral 100.
Figure 1 illustrates the top view of the system 100. The system 100 comprises an exhaust rocker arm, hereinafter referred to as the first rocker arm 102. The first rocker arm 102 is configured to perform the opening and closing of an exhaust valve 118. The system 100 further comprises an intake rocker arm, hereinafter referred to as the second rocker arm 104. The second rocker arm is configured to perform the opening and closing of an intake valve 120 when the vehicle engine is operating at lower speeds, say at or below a first speed, where the first speed is the lower threshold speed. The system 100 further comprises, a dummy rocker arm, hereinafter referred to as the third rocker arm 106. The third rocker arm 106 is configured to perform the opening and closing of an intake valve 120 when the vehicle engine is operating at higher speeds, say at or above a second speed, where the second speed is the higher threshold speed.
The system 100 further comprises a camshaft 116 having three lobes configured thereon. The camshaft 116 is supported for rotation about a camshaft axis. The function of the rocker arms is to convert the rotary movement of the camshaft 116 (as illustrated in Figure 3a and Figure 3b) to a linear movement of the exhaust valve 118 and the intake valve 120. A first lobe 116A, configured on the camshaft 116, is functionally coupled with the first rocker arm 102 and is configured to perform controlled oscillation of the first rocker arm 102. The controlled oscillation of the first rocker arm 102 causes the opening and closing of the exhaust valve 118. A second low-speed lobe 116B has a non-aggressive profile. The second low-speed lobe 116B is functionally coupled with the second rocker arm 104 and is configured to perform a first controlled oscillation of the second rocker arm 104, thereby causing the opening and closing of the intake valve 120. The second low-speed lobe 116B is configured to allow the intake valve to be in the open configuration for a first period of time. A third high-speed lobe 116C has an aggressive profile. The third high-speed lobe 116C is functionally coupled with the third rocker arm 106 and is configured to perform a second controlled oscillation of the third rocker arm 106, thereby causing the opening and closing of the intake valve 120. The second controlled oscillation of the third rocker arm 106 allows for a prolonged opening of the intake valve 120 as compared to the first controlled oscillation. The third high-speed lobe 116C is configured to allow the intake valve 120 to be in the open configuration for a second period of time. The second period of time is greater than the first period of time, to enable the intake valve to be in the open configuration for a longer period to allow an additional intake of the air-fuel mixture within the combustion chamber. Typically, the rocker arm oscillates about a rocker arm shaft (not shown) with one end driven by a mechanism chosen from a group consisting of pushrod (not shown) and camshaft 116. The other end of the rocker arm controls the operational opening and closing of the intake valve and the exhaust valve. In an embodiment, the intake valve and the exhaust valve are poppet valves.
The system 100 further comprises a coupling mechanism 122 that is adapted to couple the third rocker arm 106 with the second rocker arm 104 for simultaneous movement thereof, wherein only the third rocker arm is adapted to govern the opening and closing of the intake valve 120 when the vehicle engine is operating at or above the second speed. In an operative configuration, the third rocker arm 106 is constantly coupled with the third high-speed lobe 116C, but at operating speeds of the vehicle engine lower than the first speed, the third rocker arm 106 is not coupled with the second rocker arm 104, and the opening and closing of the intake valve is governed by the controlled oscillations of the second rocker arm 104. However, when the operating speed of the vehicle engine exceeds the second speed, the coupling mechanism 122 couples the second rocker arm 104 and the third rocker arm 106, thereby enabling the third rocker arm 106 to govern the opening and closing of the intake valve. The coupling mechanism 122 comprises a solenoid actuator 110, a fork 112 configured on the solenoid actuator 110, and a pin 114 coupled with the solenoid actuator 110 via the fork 112.
The speed and pattern of the operational opening and closing of the intake and exhaust valves depend on the profile of the lobes on the camshaft 116. Typically, when the engine (not shown) is operating at lower speeds, at or below the first speed, the second low-speed lobe 116B of the camshaft 116, having a non-aggressive profile, becomes operational. Similarly, when the engine is running at higher speeds, at or above the second speed, the third high-speed lobe 116C having an aggressive profile, becomes operational. The camshaft 116 with three such lobes is illustrated in Figure 3a and Figure 3b. As per the current disclosure, the second low-speed lobe 116B having a less aggressive profile actuates the intake valve 120 adhering to the less speed and differing load conditions on the engine. With the increase in engine speed, the third high-speed lobe 116C having an aggressive profile, actuates the third rocker arm 106, thereby causing the opening and closing of the intake valve 120 with a different timing. The aggressiveness of a cam lobe profile is defined by the lift and the duration of the opening of the valve. An aggressive cam lobe profile provides a higher lift and a longer duration of opening to the valve, relative to a non-aggressive cam lobe profile. In the present embodiment, the second low-speed lobe 116B has a non-aggressive profile, and the third-high speed lobe 116C has an aggressive profile.
The camshaft 116 is supported for rotation about a camshaft axis. The actuation of the exhaust valve 118 is controlled by the first rocker arm 102 that is adapted to be functionally coupled with the first lobe 116A configured on the camshaft 116. The actuation of the exhaust valve is governed only by the first lobe 116A configured on the camshaft 116. Whereas, the actuation of the intake valve 120 can be selectively governed either by the second rocker arm 104 or the third rocker arm 106 by coupling or decoupling the second and third rocker arms 104, 106. The second rocker arm 104 is adapted to be functionally coupled with the second low-speed lobe 116B configured on the camshaft 116, and the third rocker arm 106 is adapted to be functionally coupled with the third high-speed lobe 116C configured on the camshaft 116. The coupling and the decoupling of the second rocker arm 104 and the third rocker arm 106 depends upon the operating speeds of the vehicle engine. Below the first speed of the vehicle engine, the third rocker arm 106 and the second rocker arm 104 are decoupled, and above the second speed of the vehicle engine 106, the second and the third rocker arms are coupled and the actuation of the intake valve is governed by the third rocker arm 106. The coupling and the decoupling of the second rocker arm 104 and the third rocker arm 106 is controlled by the coupling mechanism 122. The pin 114 of the coupling mechanism 122 is adapted to pass through through-holes configured in the second rocker arm 104 and the third rocker arm 106. In an extended configuration, the pin 114 couples the second rocker arm 104 and the third rocker arm 106. In a retracted configuration, the pin 114 decouples the third rocker arm 106 with the second rocker arm 104. The extension and the retraction of the pin 114 are controlled by the solenoid actuator 110 of the coupling mechanism 122. The pin 114 is connected to the solenoid actuator 110 by means of the fork 112.
The system 100 includes an ECU (not shown) which monitors the speed and load requirements. Alternatively, the use of a controlled digital ignition (CDI) system is envisaged for monitoring the speed and load requirements. The ECU controls the lateral movement of the pin 114 with the help of the solenoid actuator 110. In an embodiment where the engine is operating at or below the first speed, the third rocker arm 106 is disconnected from the system 100, i.e., the solenoid actuator 110 is de-energized with the pin 114 in a retracted position. The speed of the engine starts decreasing until reaching a value lower than the first speed, after which the speed is maintained for more than two seconds following which the crank angle information is fed to the ECU which in turn signals the retraction of the pin 114. The retraction of the pin 114 causes the disconnection between the second rocker arm 104 and the third rocker arm 106. With the pin 114 retracted, the third rocker arm 106 is disconnected, and the opening and closing of the intake valve 120 is governed by the second rocker arm 104 that follows the second low-speed lobe 116B of the camshaft 116, thereby allowing sufficient air fuel mixture intake into the combustion chamber.
In another embodiment, the speed at which the vehicle engine operates is higher than the second speed. When the high speed is maintained for more than 0.5 second and the crank angle reaches a pre-determined value, the ECU energizes the solenoid actuator 110. It can thus be concluded that the second time period is greater than the first time period by at least 0.5 second. The solenoid actuator 110 pushes the pin 114 via a fork 112, thereby connecting the second rocker arm 104 and the third rocker arm 106 when both the rockers are on their base circle. The third rocker arm 106 that follows an aggressive profile of the third high-speed lobe 116C is further connected with an energy absorbing mechanism. Typically, the energy absorbing mechanism is a spring 108. The spring 108 adds on to the aggressive oscillation of the third rocker arm 106 and also maintains constant contact between the third rocker arm 106 and the third high-speed lobe 116C. Typically, the activation and de-activation of the system 100 is separated by 500 rpm to avoid the continuous activation and de-activation of the pin, i.e., the second speed is greater than the first speed by at least 500 rpm. Thus, the solution provided reduces fuel wastage by avoiding unburnt fuel to escape through the exhaust port and improve vehicle performance.

TECHNICAL ADVANCEMENTS
The technical advancements offered by the present disclosure include the realization of:
• a system for controlling valve timings in vehicle engines which improves the performance and fuel economy of the vehicles;
• a system for controlling valve timings in vehicle engines which automatically adjusts the valve timings with the speed and load on the vehicle;
• a system for controlling valve timings in vehicle engines which is reliable;
• a system for controlling valve timings in vehicle engines which facilitates adequate time for opening and closing of the valves to allow adequate quantity of air fuel mixture to enter the combustion chamber;
• a system for controlling valve timings in vehicle engines which avoids unburnt fuel to escape through the exhaust port;
• a system for controlling valve timings in vehicle engines which takes less time to be activated and de-activated; and
• a system for controlling valve timings in vehicle engines which allows the use of multiple lobes on the camshaft.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
The numerical values given of various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the disclosure unless there is a statement in the specification to the contrary.
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. ,CLAIMS:1. A system for controlling valve timings in a vehicle engine, said system comprising:
• a first rocker arm configured to perform the opening and closing of an exhaust valve;
• a second rocker arm configured to perform the opening and closing of an intake valve when the vehicle engine is operating below a first speed;
• a third rocker arm configured to perform the opening and closing of said intake valve when the vehicle engine is operating above a second speed;
• a camshaft supported for rotation about a camshaft axis, said camshaft having three lobes configured thereon, wherein:
- a first lobe is functionally coupled with said first rocker arm and configured to perform a controlled oscillation of said first rocker arm;
- a second low-speed lobe functionally coupled with said second rocker arm and configured to perform a first controlled oscillation of said second rocker arm, thereby allowing said intake valve to be in open configuration for a first period of time;
- a third high-speed lobe functionally coupled with said third rocker arm and configured to perform a second controlled oscillation of said third rocker arm, thereby allowing said intake valve to be in open configuration for a second period of time; and
• a coupling mechanism adapted to couple said third rocker arm with said second rocker arm for simultaneously movement thereof, wherein only said third rocker arm is adapted to govern the opening and closing of said intake valve when the vehicle engine is operating at or above said second speed.

2. The as claimed in claim 1, wherein said coupling mechanism comprises:
• a solenoid actuator having a fork configured thereon; and
• a pin coupled with said solenoid actuator via said fork, said pin adapted to be actuated in an extended configuration and a retracted configuration, wherein said pin couples said second rocker arm and said third rocker arm in said extended configuration.

3. The system as claimed in claim 1, wherein said second speed is greater than said first speed by at least 500 rpm.

4. The as claimed in claim 1, wherein said coupling mechanism is actuated to couple said third rocker arm with said second rocker arm when the vehicle engine is operating at said second speed for a period of at least 0.5 second.

5. The as claimed in claim 1, wherein said second period of time is greater than said first period of time by at least 0.5 second.

6. The system as claimed in claim 1, further comprising a spring functionally coupled with said third rocker arm to maintain constant contact between said third rocker arm and said third high-speed lobe.

7. The system as claimed in claim 1, wherein said intake valve and said exhaust valve are poppet valves.