GB2466513A - Computer controlled hydraulic and mechanical system for variable valve timing, valve lift and valve opening duration in car engines - Google Patents

Abstract

This system comprises computer, hydraulic and mechanical components with their subsets including central computer (ECU) 1, sensors 2,3,4, hydraulic pump 5, hydraulic valve, hydraulic pistons, spiral valve shaft (fig.3), intermediate gear (fig.4), regulating shaft (fig.6), valve 10 with a small spring 8 and a big spring 9 and semi-mobile pins (fig.9). The flexibility of this system in bringing about the necessary changes in the way valves open and close at various times provides the car with the ability to regulate timing of opening, duration of opening and degree of lift in intake valves at any given revolution in the best possible fashion.

Description

The Variable Valve Timing Lift and Duration of Opening System for Car Engine Valves (VVTL-D)

Technical background of the Invention

The present invention pertains to a part of feeding system to car engines which comprises the variable valve timing systems.

Relevant Prior Art

In general, fixed valve timing is a compromise between engine performance at maximum revolution (to attain maximum torque) and satisfactory engine performance at various revolutions. Therefore, in order to achieve maximum torque over a wide range of engine revolutions and decrease fuel consumption, designers started to think of using variable valve timing systems.

The common types of variable valve timing systems are as follows: * BMW VANOS -Varies intake and exhaust timing by rotating the camshaft in relation to the gear.

* Ford Variable Cam Timing -Varies valve timing by rotating the camshaft * GM DCVCP (Double Continuous Variable Cam Phasing) -Varies timing with hydraulic vane type phaser (see also Ecotec LE5).

* Honda VTEC -Varies intake, duration, and lift by using two different sets of cam lobes * Mitsubishi MIVEC -Varies valve lift * Nissan N-VCT -Varies the rotation of the cam(s) only, does not alter lift or duration of the valves.

* Porsche VarioCam Plus -Varies intake timing by adjusting tension of a cam chain as well as valve lift by different cam profiles * Toyota VVTL-i -Varies timing by advancing the cam chain and between two sets of cam lobes Evaluation of Present Technical Information The old fixed valve timing systems that do not change at various engine revolutions cannot meet the designers' needs. In fact the main concern of the designers is to remedy two deficiencies at low revolutions and specifically at high revolutions. Because of the very short period the fuel intake valve is open, even despite the effectuation of overlap; at high revolutions the volume yield of engines is still low.

That is why to correct the two aforementioned deficiencies; designers have turned to variable valve timing systems. The essential design of these systems is based on three changes in valves.

1. Regulating the valve shaft to open the fuel valve earlier than usual at high revolutions(variable timing) 2. Increase in the time when the valve is open( duration of opening) 3. Increase in valve lift (degree of opening) All the systems designed so far incorporate one or at most two of the three factors mentioned and furthermore due to lack of high flexibility to conform to different running conditions of the engine at various revolutions, these systems are incapable of simultaneously rectifying the low volume efficiency of the engine at very high and very low revolutions. The other problem of these systems in enhancing the volume efficiency at low revolutions is the prolongation of fuel valve opening at low revolutions. This prolongation does not improve the engine volume efficiency but rather it leads to problems such as difficult starting of engine and at low revolutions high pollution as well as non-smooth running of engine in addition to low power output. As a result these engines become obsolete and lose their efficacy. Since most sports cars achieve their maximum torque at high revolutions to be able to have more power at those revolutions while maintaining their dynamic capabilities, they continuously need to keep their revolutions at a high level and this leads them to having exorbitant fuel consumption.

Disclosure of Invention

This invention is a type of timing system-degree of lift and duration of opening for variable valves in car engines. The main aim of this design is achievement of the most desirable torque curve for an engine, one that would show the least oscillation in relation to the engine revolution. This means the engine would produce the highest possible torque at a wide range of its revolution. To attain this goal it is necessary to produce three simultaneous changes in the manner valves open in engines (timing of opening, degree of lift and duration valves remain open) along with high flexibility in effecting changes under various running conditions of the engine (revolution-load).

When changing gears the engine loses some speed and in order to increase its revolution and regain its previous state it must burn extra fuel. But if the torque power is high, fuel consumption decreases. One of the reasons for low fuel consumption in Diesel engines -in addition to their high density coefficient-is their possession of high torque at low revolutions.

In summary this system is divided in to three general components which in order are as follows: 1) computer and electrical 2) hydraulic 3) mechanical All the above components are also seen in today's cars. With regard to parts one and two, not much has been modified compared to present systems and only their mode of application in this system has changed.

1. Computer and electrical component: Today few cars can be found in which a device called central computer (ECU) is not used. All data from various parts of the car such as security system, automobile balance, air conditioning, engine etc reach this device which, in a short period analyzes all the information and under different sets of conditions makes the best decisions and conveys them to the executive systems. Using sensors in computers one can easily control the activities of the engine. Sensors in fact function similarly to the nervous system in vehicles by sending the information from different sections as a signal (a weak electrical current) to the vehicle's brain which is the micro-computer. Sensors have different functions depending on their location. The necessary sensors for this design consist of: 1. The engine revolution sensor: this sensor is the most important one. The precise time of valve opening and closure is regulated using the information from this sensor. It is normally mounted on the revolution gauge which is usually located on the injector pump or inside the gearbox.

2. Oil pressure sensor: this sensor has an important role in production of accurate hydraulic pressures and is mounted behind hydraulic pistons of pins.

3. Air pressure sensor: To have the proper volume efficiency in the engine, pressure and amount of entering air is a crucial factor. Therefore the intake air pressure should be continuously fed to the central computer so that under various running conditions of the engine, its amount and pressure can be regulated in the feeding system of the engine. This sensor is mounted inside the feeding system.

With the precise data received from the sensors, the central computer calculates the exact hydraulic pressure required by the pins and sends an exact hydraulic pressure via an electric pump and electric valves (solenoids) to the back of pins. To summarise, this component comprises three parts: * Sensors: to collect data from various parts of the engine * Micro-computer: to calculate and command * Electrical pump: to execute computer's orders and produce hydraulic pressure 2. Hydraulic component: This component comprises hydraulic pump, connector pipes, electric valves and hydraulic pistons. The network of connector pipes start from the pumps' outlet and ends at the electric valves which are under every pin. Hydraulic pumps are used to produce continuous hydraulic pressure in this design and for every row of cylinders one pump can be used. In this design for every pair of valves two pins are employed and since they act independently of each other they are known as pin number one and two. To move each one of these pins a hydraulic piston, and behind it an electric valve to produce precise hydraulic pressure have been used. Therefore, under various working conditions of the engine these two pins with the different hydraulic pressure that is applied to them create different combinations beside each other and this is essential to achieve the best volume efficiency.

3. Mechanical component: this comprises four main parts as follows: spiral valve shaft, the intermediate gear, regulating shaft and semi-mobile pins.

Spiral valve shaft: the main function of this part in the engine assembly is to open the valve for intake of fuel and air mixture and exit of burnt gases. This is done using the almond-shaped projections located on it. Of course these knobs are not in direct contact with the valve but rather with the position of the valve shaft in the engine which may be in the cylinder head or cylinder block, act via middle components such as typits and often via pins (valve hammer) which are located on horse shaft. In the proposed design the valve shaft cannot be called "knob" shaft due to its different shape. This is because in the valve shaft the almond-shaped knobs have been omitted and replaced by spiral-shaped gears. That is why the term "spiral "valve shaft has been used. The role of this shaft in this design is to rotate the small regulating shaft on the main valve. This rotation is eventually transmitted as pressure to the main valve through a gear that lies between the spiral valve shaft and the regulating shaft. The spiral cogs engage several cogs of the opposite gear simultaneously and increase the efficiency of movement transmission and bring about smoothness in transmission and decrease in noise. In the proposed design for every row of cylinders one valve shaft has been used which takes its rotational movement from crankshaft pulley using belts or chains.

The intermediate gear: The function of this gear is to transmit the movements of valve shaft to the upper mobile valve which is the same as the regulating shaft. This gear bears both circumferential outer cogs which engage spiral valve shaft and inner cogs which engage the cogs on the adjusting shaft inside this gear. It is positioned in the cylinder head using two metal pieces which envelope the gear from above and below and in order for it to be able to rotate easily in its bed and avoid displacement, ball-bearings have been utilized on either side and in-between the inner and outer cogs. By rolling on the surrounding metal pieces, these bearings stop any contact between them and the gear and at the same time give the gear freedom to rotate easily in its bed and carry out its function.

*The regulating shaft: in general valves have identical forms and functions in all cars, however to achieve a high torque in a wide range of the engine's revolution changes have been made to the set of valves in this design. In this invention valve has been divided in to two parts namely regulating shaft and main valve. Due to its connection to the spiral valve shaft, the regulating shaft continuously revolves around its vertical axis and the main valve which is a miniaturised version of the current valves is fixed in its place and functions similarly to other valves.

The second change can be seen at the end of the regulating shaft. At the end of the shaft there is a wavy prominence situated at the side of adjusting shaft. The role of this prominence in this set is that with every rotation of the adjusting shaft around its axis it hits an opposing object namely the semi-mobile pins leading to pushing down of the regulating shaft followed by the main valve.

The third change that has occurred in the set of valves is the use of two small and big springs under the main valve tray to close the valve. But the major difference between this and current designs is that one of the springs is bigger than the other.

The main point regarding the enhancement of engine efficiency at low revolutions which had not been resolved in previous systems can be stated as follows" To increase the volume efficiency of the engine at low revolutions, the volume of mixture entering cylinder should be increased without any increase in the duration of valves remaining open and only via an increase in the degree of valve lift".

This system increases volume of mixture entering cylinder only through increasing the degree of valve opening at the appropriate time for low revolutions. This has resolved the weakness in the old systems. Having stated the above points, the difference in size between the bigger and smaller springs under the valve can be justified. In this design, the main valve has a tray similar to all other valves. The bigger spring is sandwiched between the valve tray and the body of cylinder head and functions like other springs and when the engine revolves normally, it is the spring's job to return the valve to its original position. But when the engine at low revolutions requires an increase in volume efficiency or its preservation, this can be done through increased opening of intake valve and in order for the duration of valve opening not to exceed the usual period for that revolution a small spring has also been positioned inside the main spring which allows quicker closure of the valve at these moments. Normally this small spring has no contact with the tray and stays at a defined distance from it and is not under pressure. But when the valve opens more than usual, this spring is pressed similarly to the main spring and on recoil closes the valve more quickly.

* The pins: The role of the pins in this design is similar to that in present engines i.e. transmission of pressure from valve shaft to the valve. However its mode of action is different. In this design the pressing agents at the end of pins are not the cams of valve shaft or typits. But rather the pressing agents are the hydraulic pistons which are moved by oil pressure and control precisely the degree of movement of the pins. In this design for every pair of intake valves two small pins which are stuck together have been used. In this invention the extent of pin movement has been markedly reduced and is only limited to when the need for change in duration and timing of valve opening is felt necessary. Various combinations of the way these two pins are positioned beside each other offers the optimal state for valve opening and consequently the most suitable volume efficiency for engines. The design used for the pins is that when the two pins stand side by side and in contact with each other the path that the prominence on the adjusting shaft follows to hit these two pins is a curve. All the variable timing systems work on the basis of regulating the valve shaft for premature opening of the fuel valve at high revolutions, increase in valve lift or duration of valve remaining open. In this invention all three methods have been utilised to increase volume efficiency. That is to say, the up and down movement of the first pin not only adjusts the minimum and maximum opening of valves but also controls the timing of their opening. The more the first pin moves downwards the earlier the prominence on the adjusting shaft contacts this pin and consequently the earlier the valve opens and vice versa. The second pin is also in charge of the duration of patency of valves. The position of the second pin along the first affords the best possible timing to the engine for filling of cylinder with petrol and air mixture. The maximum time for the valve remaining open is when the two pins are aligned in one row and in contact. At low revolutions only the first pin opens the valve and the second one plays no role. That is because at low revolutions cylinders require large amounts of air intake during a short period. That is why at this revolution the valve should remain widely open for a short period. To achieve this, the first pin assumes its lowest position so that the prominence on the regulating shaft moves down on the slope after hitting this pin and opens the valve maximally. After the above steps, the prominence on the regulating shaft passes the first pin and since at this revolution the valve opening time is short and the second pin is at its highest position with no contact with the prominence, the intake valve moves up quickly due to the two springs mounted below it and shuts the valve opening. At high revolutions in order to solve the problem in timing of valves and also compensating for the inadequate amount of air in manifolds, the intake valves should open to a larger extent and for longer than normal. For this to happen, the arrangement of the pins is such that both pins-to the same extent, alongside each other-are widely pushed to their lowest limits by the hydraulic pistons.

In doing so, the intake valve also starts moving down earlier than normal (regulation of opening time) and as the two pins are at their lowest point, the valve returns to its original position (change in degree of lift) and eventually since the pins are positioned alongside each other at the same level, the valve will experience its longest duration of opening( regulation of duration of remaining open) Useful effects of the Invention * Engines that use the variable valve timing for valves can regulate the duration of air valve suction and its steps according to load and speed of engine in an optimal fashion.

* With separate control of each of these pins, production of constant rotational torque at high levels and through a wide range of engine's revolution can be achieved * With the use of two springs in different sizes and also the regulating shaft above the main valve, this system can maximally open the fuel valve to increase the volume efficiency at low revolutions * The application of two pins allows one to be used for timing regulation of valve opening and the other for duration of valve remaining open * This system has less vibration due to having a two-spring valve and the valve closes faster.

* The use of curved prominence on the adjustment valve allows the system to increase the extent of fuel valve opening at various rotations.

* The use of two pins alongside each other allows intake valve lift to its maximal level * This system through increase in the volume of mixture entering the cylinder allows maximum use of a system and as a result reduces design and production cost of engines * This system is highly flexible in variation of each of three factors (variation in timing of fuel valve opening, variation in degree of valve lift, variation in duration of valve being open) at every engine revolution * By shutting down some of the engine's cylinders and using high torque power, this system needs fewer gear changes and less fuel Presentation of Invention mechanism This invention comprises three components: electrical (figure 1), hydraulic (figure 2) and mechanical (figure 3).The computer and electrical component deals with recognition of engine's running conditions and decision-making. As shown in figure (1), this component comprises three parts of engine revolution sensors(2), oil pressure (3) and air pressure (4) as information -collecting and transmitting part from required areas, central computer(1) as the decision-making unit and finally electric pump (5) to produce hydraulic pressure. The result of activity of this part is transmission of electrical command from the central computer to the electric pump to produce hydraulic pressure behind electric valves (6).In general, in a four-cylinder four-valved engine one central computer, a few sensors of engine revolution, air and oil pressure and an electric pump are used.

Electric valves or solenoids (1) in figure (2) have the most important role in hydraulic component.

These valves using orders they receiver from central computer dispatch a precise amount of oil to the back of hydraulic pistons of every pin in order to regulate the position of pins. In this system every pin has a separate function and consequently to regulate each one an electric valve is directly connected to the central computer and overall in a four-cylinder engine with four valves eight small electric valves are needed to regulate eight intake valve pins.

The mechanical component is the most important part of this system and comprises the spiral valve shaft as in figure (3) number (1), intermediate gear (figure 4), the gear-supporting pieces (figure 7), regulating shaft (figure 6) and semi-mobile pins (figure 9). In this system the knobs on the valve shaft have been omitted and replaced by semi-spiral gears. The function of this shaft is to turn the intermediate gear on which the regulating shaft is located. Figure (5) number (1) and figure (8) number (1) illustrate how this is done. It must be mentioned that the valve shaft is mounted on the cylinder head in a Double Over Head Cam (DOHC) fashion.

In a linear four-cylinder engine, one valve shaft with four spiral gears is used to open eight valves.

The function of intermediate gear in this system is to transmit the valve shaft rotation to the regulating shaft and it is positioned in between two supporting pieces (figure 7). This component (intermediate gear) is used according to the number of cylinders in the engine complex.

The regulating shaft (figure 6) is of particular importance due to its role in this system. This piece is constantly rotating around its axis in the intermediate gear. Due to presence of four stage cycle, its speed of rotation is half that of crankshaft. The size of the curved prominence on this shaft depends on the maximum lift and duration of valve opening. In this system two intake valves are joined via a connector. The regulating shaft does not directly sit on the valve but rather sits on the connector between the two valves and pushes it down. But in the figure for better understanding of the system, the regulating shaft sits directly on the valve and is illustrated as such. In fact the assembly of two pins, a regulating shaft and a gear produces the simultaneous pressing down of the two intake valves. In this system the size of the valves is smaller than usual as they are not in direct contact with the pins. There are two springs under the valve; a big one as in Figure (3) and a small one as in figure (3) number (8). The big spring is in direct contact with the valve tray but the size of the small spring is determined by the maximum lift of the valve. The distance of small spring from the tray in normal revolutions depends on the extent of valve lift in these revolutions. The small spring is made of harder and stronger material than the big one. This property allows it to gather more potential energy when being compressed and to be able to show a quick response in returning the valve.

In this system as in figure (5) number (2), the semi-mobile pins are mounted in pairs on a shaft called horse shaft and opposite the upper part of the regulating shaft which bears a curved prominence and their first part which is cut in a crescent shape covers part of the regulating shaft. In figure (8) number (4) the mode of positioning of these two pieces beside each other is shown. The diameter of the imaginary circle that forms the crescentic part of the pins is equal to that of regulating shaft. In this system as in figure (8) number (3) a pair of pins is responsible for opening two intake valves of a cylinder. These pins with their independent free up and down movement on the horse shaft as in figure (8) number (2) form different combinations of positions alongside each other and in so doing can regulate the exact time of opening, duration of opening and degree of lifting the valves. The range of movement of these pins has a direct relationship to the maximum opening of valves. When there is no need for valve opening they stand at their highest point in line with the upper part. The power for these pins is supplied by a hydraulic piston which is attached to end of each one of them and fed by electric valves.

Claims (10)

1. Claims 1. The timing, lift and variable valve opening duration system in car engines which comprises three main components namely computer, hydraulic and mechanical can change the three major factors in variable valve timing systems i.e. timing of opening, degree of lift and duration of opening in any revolution of the engine to achieve the maximum volume efficiency.
2. 2. The computer component of the system mentioned in Claim no. 1 has sensors for engine revolution, oil pressure, air pressure and temperature in order to recognise the working conditions of engine and it also has a central computer (ECU) for decision-making and issuing commands to the hydraulic part and an electric pump to exert hydraulic pressure.
3. 3. In view of claim number 1, the hydraulic system is made up of oil-transmitting conduits and solenoid valves which are highly sensitive to commands received from central computer and channel a precise amount of oil under hydraulic pistons controlling each pin according to issued commands.
4. 4. In view of claim number 1, the mechanical component of this system consists of spiral valve shaft with spiral threads instead of knob, intermediate gear, supporting pieces, intermediate gear, regulating shaft with curved prominence at the top, main valve two springs of different sizes and semi-mobile pins with crescentic groove at the proximal end.
5. 5. In view if claim number 4, in this system the knobs on main valve shaft have been omitted and replaced by spiral (butterfly-shaped) gears.
6. 6. In view of claim number 4, the role of intermediate gear in this system is transmission of valve shaft to the regulating shaft.
7. 7. In view of claims number 4 and 6, the system has supporting pieces to hold the intermediate gear in place.
8. 8. In view of claim number 4, the regulating shaft in this system bears threads for contact with gear and also a curved projection at its proximal end.
9. 9. In view of claim number 4, the semi-mobile pins that in the mechanical component are controlled by hydraulic pistons are used in pressing down the regulating shaft and main valve.
10. 10. In view if claim number 4, this system has two different-sized springs (big and small) under the main valve tray to close the valve at the appropriate time.