WO2017204769A2

WO2017204769A2 - Piezoelectric stack-driven inlet / exhaust valve

Info

Publication number: WO2017204769A2
Application number: PCT/TR2017/050214
Authority: WO
Inventors: Ali SÜRMEN
Original assignee: Sürmen Ali
Priority date: 2016-05-26
Filing date: 2017-05-23
Publication date: 2017-11-30
Also published as: TR201607052A2; WO2017204769A3

Abstract

In internal combustion engines, there is a inlet / exhaust valve (1) comprising a valve head (71) which controls the intake of the air-fuel mixture or only the intake of the air into the combustion chamber and the discharge of the burned exhaust gas by moving in a bi-directional manner within a body (6), a drive member (8) that applies a force for the valve head (71) to remain in the same position continuously and at least one piezoelectric stack (21) made of a piezoelectric material which performs the movement of the valve head (71) by defeating the force exerted by the said drive member (8), wherein it comprises at least one primary piston (4) transmitting the motion that it received from the piezoelectric stack (21), at least one hydraulic chamber (61) which applies the motion received from the said primary piston (4) over a large diameter duct (A) via its hydraulic fluid (61a) as a pressure force over a small diameter duct (B) that has a smaller area, and a control unit (3) which achieves a desired amount of elongation by applying electrical potential to the said piezoelectric stack (21) at the predetermined quantities according to the engine speed and thus enables it to be driven.

Description

Piezoelectric Stack-Driven Inlet / Exhaust Valve Technical Field

The invention relates to a design in an internal combustion engine, which can vary the opening and closing timings of the inlet / exhaust valves that control the intake of fuel-air mixture or only air into the combustion chamber and the discharge of the burned exhaust gas.

Different from conventional cam mechanisms, the invention particularly relates to a design which uses a stack manufactured from piezoelectric material consisting of layers in the form of plates as a drive source and magnifies the motion received from the piezoelectric block by double-stage hydraulic system as well as can vary the opening and closing timings of the inlet / exhaust valves.

Prior Art

Generally, valves are the components that regulate the flow of a fluid from one space to another by moving up and down or back and forth in a certain direction with the help of a spring. One of the most widespread uses of valves among many areas is the internal combustion engine. The inlet / exhaust valves used in the motors control the intake of the fuel-air mixture or only the air into the combustion chamber and the discharge of the burned exhaust gas. The valves, which are normally closed under the force of a spring, are actuated to open by cam or cams positioned on a camshaft. Patent application 2013/13298 entitled 'Variable Timing Cam with Curvilinear Surface' discloses that camshafts with the shape identified allow opening of valves by transmitting their circular movement via cams.

Since valve opening and closing times and valve lift or stroke in conventional cam systems is fixed with mechanical design of the cam, opening and closing times and valve lift cannot be varied with varied engine speed, which results with decrease in volumetric efficiency with varied speed. The mechanical system, on the other hand, exposes wear and tear problems as its elements must have a moving contact with each other.

Many different techniques have been tried to overcome these problems of classical cam mechanisms. Most of these techniques, which can be classified as staged variable and continuous variable, are mechanical but some of them are electro-mechanical or electro-hydraulic systems. However, those with satged variability have not found widespread use because they cannot provide continuous variability; some of those with continuous variability provide variability in a form that depends on their geometry, rather than in a speed-based optimized form; and some of those have performance problems at high speeds. In the current technique, piezoelectric materials are used for valve drive as an alternative to cam systems in some applications, particularly in internal combustion engine applications. Piezoelectric featured materials are materials of the kind that produce electric field or electric potential under mechanical effect. The opposite is also possible and such materials are capable of elongating when electrical potential is applied. This elongation can also be used as a drive source under certain conditions. Another feature of piezoelectric materials is that they have very high frequency and they can do this opening-closing motion thousands of times in a second. These two features enable the piezoelectric materials with a control unit to form an opening-closing timing that provides the highest volumetric efficiency designated according to the engine speed. Austrian patent document no AT29553 discloses a valve configuration using a piezoelectric control element as a drive source in the manner that is mentioned. Said configuration is a drive mechanism that sets the opening and closing motion of the valve according to the expansion occurring in the piezoelectric control element in the internal combustion engines. However, the stroke magnification in the drive mechanism is carried out mechanically, in other words with the known rocker mechanism. For this reason, as mentioned above, wear and fatique problems as well as delays in reaction time can occur. Japanese patent document no JP2001 159302 also uses piezoelectric material. In the said invention, the piezoelectric material is located within a driver and piezoelectric driven displacement motion of the driver takes place at a certain ultrasonic vibration level. This is an electromechanical system like the other.

Another application is a Chinese patent application no CN103953415A. The said system includes a single-stage structure. It has a structure that occupies a dimensionally larger volume. It has a design difficulty in the engine head. The amount of elongation that occurs when electrical potential is applied to piezoelectric materials is not enough to move the valve. For this reason, as mentioned above, some mechanical techniques are used to increase this movement. However, high efficiency cannot be obtained due to delays and sensitivity limitations. One of the most important problems is to transfer the piezoelectric drive to the valve stem without losing by increasing it. The use of hydraulic fluid for this is one of the recommended methods. As a result, in contrast to conventional cam mechanisms, the need for inlet / exhaust valves that use a stack manufactured from piezoelectric material as drive source and amplify the amount of reciprocating movement from the piezoelectric block by a two-stage hydraulic system and inadequacy of existing solutions necessitate making improvements in the relevant technical field.

Object of the Invention

The present invention relates to a system, which meets the above-mentioned requirements, which is capable of providing infinite inlet / exhaust valve opening-closing variation with respect to all kinds of engine parameters, especially engine speeds, and eliminates all disadvantages of the prior systems.

The main purpose of the inlet / exhaust valve according to the invention is to use a stack manufactured from piezoelectric material as a valve actuating element and to increase the drive from the said stack by means of the piston system using hydraulic fluid. In this way, by taking the advantage of the ability of piezoelectric materials to open-close at the desired time and at any desired engine speed, the opening-closing timing can be changed with infinite flexibility according to the desired parameter as well as all problems including high speed operation of all existing valve-driven systems are eliminated by reaching the lifting lengths required by the valves. This means that the highest power that could be obtained from the engine at every speed can be achieved. Thus, since the engine can run at a lower speed to achieve the same power, mechanical efficiency of the engine and therefore overall efficiency is also increased. Since the developed mechanism does not require the use of a gas throttle, the losses during inlet and exhaust processes (pumping) of engines are reduced and therefore thermal overall efficiency is increased once again. A further contribution to the overall efficiency of the engine is that with the present invention, the average thermodynamic efficiency will increase as the effective compression ratio of the engine can be changed.

Another object of the invention is to transfer the elongation length of the piezoelectric stack to a valve by amplifying via contacting with the stepped pistons in chambers, where hydraulic fluids are present, due to the wider A surfaces, from which the drive is taken, than B surfaces, to which the drive is given. By this way, an elongation in the range of 30-60 microns can be converted into an amount of valve lift in the range of 5-12 mm, which is necessary for the valves by selecting the appropriate piston surface areas. The purpose of using double-staged magnification in the present invention is to be able to design this system in the dimensions of piezoelectric injectors which are still widely used and therefore to produce the system inexpensively by using their production technology. Depending on the diameter of the valve stem, it would be possible to achieve the system in a typical injector size by using a ratio of A/B=4/1 in each magnification step in a typical automobile engine.

Another object of the invention is to set the valve opening parameters according to a certain speed by determining them at different speeds of the motor through the control unit. In doing so, by applying electrical potential to the piezoelectric block in the direction of the predetermined values specific to the speed values, the amount of elongation and consequently the amount of drive are instantly adjusted. In this way, the highest volumetric efficiency at each speed can be guaranteed. Moreover, since the compression and expansion ratios can be adjusted in engines independently, designs at fixed and low compression ratios can be prevented for fear of knocking. Engines would be able to run at the highest possible compression ratio depending on the operating conditions. This will be another factor that provides the highest increase in thermodynamic efficiency.

Another object of the invention is to provide the electric potential of the piezoelectric stack to be uniformly applied to every point by keeping it in a sheath made of an electrically conductive material. This makes it possible to fully utilize the elongation property of the piezoelectric material and to eliminate possible losses.

Another object of the invention is to prevent the electrical losses due to the package of the piezoelectric stack being manufactured from an electrically insulated material and to ensure that the block fulfills its mission completely.

Another object of the invention is to ensure that the valve head is kept in a closed position consistently by using a drive element such as a spring as in the existing systems. In this way, decrease in the engine efficiency is prevented by bringing the closing process faster and serialize.

Another object of the invention is to provide that the elongation movement is carried out in only one direction by means of a buffer provided on one end of the piezoelectric block. In this way, the drive can be provided only in the desired direction.

A further object of the invention is the Chinese patent application no CN103953415A having a single step structure, the said invention having a double stage structure. It has also a very narrow cross section due to two steps. In order to achieve the above-mentioned purposes in the most general way, different from traditional cam mechanisms, a inlet / exhaust valve which uses a stack manufactured from piezoelectric material as a motion actuator and magnifies the motion received from the piezoelectric stack by double-stage hydraulic system is developed. The developed inlet / exhaust valve includes a body; a valve plate which moves in a bi-directional manner and controls the intake of the air-fuel mixture or only the intake of the air into the combustion chamber and the discharge of the burned exhaust gas; a drive member that applies a force for the valve plate to remain in the same position continuously; at least one piezoelectric stack made of a piezoelectric material which performs the movement of the valve plate by defeating the force exerted by the drive member; at least one primary piston transmitting the motion that it received from the piezoelectric block; at least one hydraulic chamber which applies the motion received from the primary piston over a duct with a large dimeter via its hydraulic fluid as a pressure force over a duct with a small diameter that has a smaller area; and a control unit which achieves a desired amount of elongation by applying electrical potential to the piezoelectric stack at the predetermined times and quantities according to the engine speed and thus enables it to be driven.

Structural and characteristic features and all advantages of the invention will become apparent via the below drawings and detailed description that is written by making reference to these drawings and thus, the evaluation should also be performed by taking these drawings and detailed description into account.

Brief description of the drawings

For better understanding the structuring of the present invention and its advantages with additional elements, the invention should be evaluated together with the drawings described below.

Figure - 1 : The cross-sectional view of the piezoelectric triggered inlet / exhaust valve and the hydraulic motion amplification mechanisms according to the invention.

Reference Numbers

1 Inlet / exhaust valve

2 Piezoelectric actuator body

21 Piezoelectric stack

22 Electrification sheath

23 Buffering base

24 Electrical insulator

3 Control unit

4 Primary piston

5 Secondary piston 5.1 Narrow section

5.2 Wide section

6 Body

61 Hydraulic chamber

61 a Hydraulic fluid

7 Valve stem

71 Valve head

8 Drive member

9 Pressure balancing chamber

91 Pressurized gas

92 Pressure balancing fluid

93 Balancing chamber tap

94 Hydraulic connection ducts

A Large diameter duct

B Small diameter duct

Detailed Description of the Invention

In the internal combustion engine according to the existing technique, there are inlet / exhaust valves (1 ) includes a valve head (71 ) which controls the intake of the air-fuel mixture or only the intake of the air into the combustion chamber and the discharge of the burned exhaust gas by moving in a bi-directional manner within a body (6), a drive member (8) that applies a force for the valve head (71 ) to remain in the same position continuously and at least one piezoelectric stack (21 ) made of a piezoelectric material which performs the movement of the valve head (71 ) by overcoming the force exerted by the said drive member (8). In the present invention, different from the known applications, there is most commonly at least one primary piston (4) transmitting the motion that it received from the piezoelectric stack (21 ), at least one hydraulic chamber (61 ) which applies the motion received from the primary piston (4) over a large dimeter duct (A) via its hydraulic fluid (61 a) as a pressure force over a small diameter duct (B) that has a smaller area, and a control unit (3) which achieves a desired amount of elongation by applying electrical potential to the piezoelectric stack (21 ) at the predetermined quantities according to the engine speed and thus enables it to be driven.

Figure -1 shows the cross-sectional view of the piezoelectric triggered inlet / exhaust valve (1 ) and the hydraulic motion magnifier (6) according to the invention. In a preferred embodiment of the invention, the piezoelectric stack (21 ) is positioned within the electrification sheath (22) which is made of electrically conductive material that mediate the feeding of the piezoelectric stack (21 ) with electric potential by covering it and of which extensions are formed between the piezoelectric layers. Around the electrification sheath (22), there is an electrical insulator (24) and a piezoelectric stack (21 ), a piezoelectric actuator body (2) that serves as a support and guard for the

electrification sheath (22) and electrical insulator (24). The electrical insulator (24) is manufactured from this material and prevents possible losses from the electrification sheath (22) to the piezoelectric actuator body (2) made of high-quality steel. A buffering base (23) is placed in the piezoelectric actuator body (2), which rests on the piezoelectric stack (21 ) at least one side so as to limit its movement to that side. Buffering base (23) may consist of hydraulic or mechanical elements and prevents the piezoelectric stack (21 ) to elongate in that direction as well. The piezoelectric stack (21 ) is directly connected to the control unit (3) and can elongate in proportion to the electric charge directed from the control unit (3). The said inlet / exhaust valve mechanism (1 ) comprises a construction with variable drive.

The piezoelectric actuator body (2) is in direct contact with the body (6) on which the hydraulic chambers (61 ) are located. The piezoelectric stack (21 ) is in contact with the primary piston (4) and applies the extension motion as a pushing force. Since the hydraulic fluid in the hydraulic chamber (61 ) where the primary piston (4) is contacted over the large diameter duct (A) is incompressible, the movement from the primary piston (4) is transmitted from the large diameter duct (A) to the small diameter duct (B), which has a narrower section, as a magnified motion at the ratio of cross- sectional areas. In a preferred embodiment, a one fourth ratio of the diameter of the large diameter duct (A) to the diameter of the small diameter duct (B) is compatible with other existing

piezoelectric motor applications. In a preferred embodiment of the invention, a second hydraulic chamber (61 ) is placed and there is a secondary piston (5) which transmits the pressure applied over the small diameter duct (B) across the large diameter duct (A), which is wider, by providing force transmission between them. The secondary piston (5) in its present form resembles a T shape. The small diameter duct (B), which is not in contact with the primary piston (4) or the secondary piston (5) in the hydraulic chamber (61 ), is in contact with the valve stem (7) and applies force under pressure. The valve head (71 ) formed on the valve stem (7) is located at the inlet of the combustion chamber as mentioned above and controls the intake of fuel-air mixture or only air and the discharge of the burned exhaust gas. The drive member (8) preferably in the form of a spring and acting as a driving member, applies a continuous compulsory force to the valve stem (7) and hence to the valve head (71 ) to remain in the same position continuously. The said hydraulic chamber (61 ) has a conical structure extending from the large diameter duct (A) to the small diameter duct (B). The secondary piston (5) has also a structure extending from the narrow section (5.1 ) to the wide section (5.2). At a certain engine speed, a current is applied through the electrification sheath (22) that covers the piezoelectric stack (21 ) by reading the most suitable time for that speed via the control unit (3) when the time comes. The piezoelectric stack (21 ), approximately 5 to 8 cm in length, can elongate 30 to 40 microns under the current due to its material property requirement. The piezoelectric stack (21 ) will not elongate upward and will naturally advance the primary piston (4) approximately 30 to 40 microns depending on the buffering base (23) formed in the piezoelectric actuator body (2). The primary piston (4) likewise pushes the hydraulic fluid (61 a) in the hydraulic chamber (61 ), to which it is connected, in the same way by 30 to 40 microns. In the hydraulic chambers (61 ), the elongation movement is increased incrementally because the large diameter duct (A) is four times larger in diameter than the small diameter duct (B) to which the pressure is applied. Since the volume of the displaced hydraulic fluid (61 a) is proportional to the 'square of the diameter x push distance', 480-640 microns movement, which is 16 fold of the distance pushed by the primary piston (4), is given to the secondary piston (5). Movement of the secondary piston (5) in the shape of T is once again increased by 16 fold if the large diameter duct (A), which is in contact with the other hydraulic chamber (61 ), has again four times larger diameter than from the small diameter duct (B) and a total of about 7680 - 10240 microns, i.e. 7.68-10.24 mm, of movement can be obtained. This is a sufficient lifting distance for the valve head (71 ). When the electric potential from the piezoelectric stack (21 ) is drawn, there is no elongation and the valve head (71 ) returns to its original state by the effect of the driving member (8).

When the secondary piston (5) is pushed downward, vacuum occurs in the upper part. It is possible for this vacuum to create some mechanical problems, such as cavitation, during advanced operating phases and especially at high speed. To prevent this, the system is equipped with a pressure balancing chamber (9). The pressurized gas (91 ) compressed into the pressure balancing chamber (9) from the inlet closed by the balancing chamber tap (93) while the system is running, transmits the pressure balancing fluid (92) underneath over the hydraulic connection ducts (94) to the space formed by the piston and prevents vacuum formation. Since the secondary piston (5) has its own weight and is under the gas pressure from above, there must be some more pre- stressing force than these two forces when the drive member (8) presses the valve head (71 ) into its slot so that the system do not move downwards by these forces while it is not desired to move.

Claims

In internal combustion engines, a inlet / exhaust valve (1 ) comprising a valve head (71 ) which controls the intake of the air-fuel mixture or only the intake of the air into the combustion chamber and the discharge of the burned exhaust gas by moving in a bidirectional manner within a body (6), a drive member (8) that applies a force for the valve head (71 ) to remain in the same position continuously and at least one piezoelectric stack (21 ) made of a piezoelectric material which performs the movement of the valve head (71 ) by overcoming the force exerted by the said drive member (8), characterized in that it comprises,

- at least one primary piston (4) transmitting the motion that is received from the piezoelectric stack (21 ),

- a hydraulic chamber (61 ) which applies the motion received from the said primary piston (4) over a large dimeter duct (A) via its hydraulic fluid (61 a) as a pressure force over a small diameter duct (B) that has a smaller area,

- at least one secondary piston (5) which transmits the pressure received from the small diameter duct (B) over the large diameter duct (A), which is wider, by positioning between them, when the said hydraulic chamber (61 ) is used more than once,

- an electrical insulator (24) configured around the said piezoelectric stack (21 ),

- a piezoelectric actuator body (2) configured on the said piezoelectric stack (21 ) and the electrical insulator (24),

- a control unit (3) which achieves a desired amount of elongation by applying electrical potential to the said piezoelectric stack (21 ) at the predetermined quantities according to the engine speed and thus enables it to be driven.

The inlet / exhaust valve (1 ) according to claim 1 , characterized in that one fourth ratio between the diameter of the said large diameter duct (A) and the diameter of the said small diameter duct (B) is kept constant.

The inlet / exhaust valve (1 ) according to claim 1 , characterized in that it comprises a hydraulic chamber (61 ) having a conical structure extending from the said large diameter duct (A) to the said small diameter duct (B).

The inlet / exhaust valve (1 ) according to claim 1 , characterized in that it comprises a secondary piston (5) having a structure extending from the narrow section (5.1 ) to the wide section (5.2). The inlet / exhaust valve (1 ) according to claim 1 , characterized in that it comprises at least one electrification sheath (22) made of electrically conductive material that mediate the feeding of the said piezoelectric stack (21 ) with electric potential by covering it.

The inlet / exhaust valve (1 ) according to claim 1 , characterized in that it comprises a buffering base (23) resting on the piezoelectric stack (21 ) at least one side so as to limit its movement to that side.

The inlet / exhaust valve (1 ) according to claim 1 , characterized in that it comprises a valve stem (7) that transmits the pressure force from the hydraulic chamber (61 ) by connecting with the said valve head (71 ).

The inlet / exhaust valve (1 ) according to claim 1 , characterized in that the said drive member (8) is a spring.

The inlet / exhaust valve (1 ) according to claim 1 , characterized in that the said inlet / exhaust mechanism (1 ) comprises a variable driven structure.

The inlet / exhaust valve (1 ) according to claim 1 , characterized in that it comprises a pressure balancing chamber (9) that prevents mechanical problems, such as cavitation, at high speeds.

The inlet / exhaust valve (1 ) according to claim 10, characterized in that it comprises pressurized gas (91 ) compressed into the pressure balancing chamber (9), an balancing chamber tap (93) and pressure balancing fluid (92) that transmits to the space formed by the piston and prevents vacuum formation, and hydraulic connection ducts (94).