Abstract:
A device for generating pressure pulses, includes a pressure fluid source and a pressure fluid depression, a pressure fluid circuit, a valve body displaceably located in a chamber, a first branch and a second branch the branches leaving to opposite sides of the valve body, the chamber having an opening on one side of the valve body, the opening communicating with the first branch and permitting pressure fluid to flow out of the chamber. The valve body, under the action of the pressure fluid in the branches, is displaceable to a first position in which it closes the opening and to a second position in which it leaves the opening open for out-flow of the pressure fluid. The device includes a first valve member arranged to permit or interrupt communication between the chamber and the pressure fluid source through the second branch upstream of the chamber.

Description:
TECHNICAL FIELD 
   The present application relates to a method for controlling a pressure fluid flow in a pressure pulse generator. 
   The invention also relates to a device for generating pressure pulses. 
   The invention is applicable to all types of technical areas were pressure pulses are to be generated. In particular it is applicable to applications on which there are high requirements on the speed with which pulses can be generated and on the time period of the individual pulses. 
   Internal combustion engines define a field in which pressure pulses can be used for controlling and effecting the movements of the valves of the combustion engine instead of operating and controlling the movements of the inlet, outlet or fuel injection valves by means of a conventional transmission of the motion of the piston of the engine to the valves by means of a camshaft. The invention can also by used for controlling and operating a piston arranged for the purpose of achieving a variable compression in a combustion engine cylinder. 
   Accordingly, the invention will, by way of example, and not in a delimiting purpose, be described with reference to the application in which it is used for the control of and operation of the inlet or outlet valves of the combustion chamber of a combustion engine. 
   THE BACKGROUND OF THE INVENTION 
   Since a number of years designers of piston combustion engines have seen a need of being able to vary the valve times during engine operation, since this would result in great advantages with regard to, for example, fuel economy and emissions. 
   Therefore, extensive efforts have been made in order to replace conventional camshaft systems for the opening and closure of engine valves by systems that are based on the use of electromagnetism for controlling and operating the valves of the engine. The disadvantage of such solutions is that the high requirements on the speed by which the valves can be operated will result in high requirements on the electromagnets that are used. The mass that each electromagnet has to bring into motion corresponds to the mass of the valve. The valve must comprise a suitable magnetic material in order to be displaced by the action of one or more electromagnets, and such materials contribute to an increase of the mass of conventional valves. This often results in an evil circle in which an improvement of a valve from a magnetic point of view will result in a weight increase that, in its turn, results in a need of larger and more powerful electromagnets. Accordingly, in this way, it will be difficult to achieve an economically and practically good solution to obtaining a sufficiently fast control and operation of the valves of the engine. Moreover, it is well known that electromagnets will require a certain time for magnetising and demagnetising. 
   There are also efforts being made to obtain the requested movements of the engine valves by means of hydraulics. Today, such systems are tested by, amongst others, vehicle manufactures. The pressure fluid, here the hydraulic liquid, is in this case used in order to effect the engine valve movement. Thereby, it is required that the pressure pulse generator that is used has an ability to deliver the pressure pulses that cause the valve movements rapidly and with high precision. The present inventor does not know any pressure pulse generator according to prior art that has the performance required to satisfyingly cope with the valve control at the rotations per minute of the engine that are used today in two-stroke, and, in particular, four-stroke combustion engines. An obstacle to the accomplishing of such a pressure pulse generator may be the difficulty to achieve sufficiently rapid opening/closure movement of the valve or valves that is/are required in such a pressure pulse generator. Here, it should be mentioned that valves are often replaced by ports in modern two-stroke engine constructions, but that the present invention results in the possibility of using valve technology in two-stroke engines in a way corresponding to that of four-stroke engines. 
   In this context, it should also be mentioned that the pressure pulse generators that may come in question should be compact and occupy only a small space in combustion engine applications. 
   THE OBJECT OF THE INVENTION 
   One object of the present invention is to provide a method and a device that enable generation of pressure fluid pulses with very high frequency and precision. 
   A further object is to provide a method and a device that make it possible to deliver pressure pulses with high frequency and precision with maximum use of the pressure fluid, i.e. without any pressure fluid loses in the pressure fluid circuit or circuits. 
   A further object is to provide a method and a device that make it possible to, with so few and uncomplicated components as possible, in particular with as few electro magnets as possible, generate pressure pulses with high frequency and precision. 
   A further object of the invention is to provide a method and a device for pressure pulse generation that are applicable to combustion engines for controlling and operating individual inlet, outlet and injection valves (for fuel or water). The invention shall also be able to act as a driving apparatus for a piston for accomplishing a variable compression ratio in a combustion engine. 
   Another object is to provide a method and a device for pressure pulse generation, that create the conditions for or, in practice, permits a transition from two-stroke operation to four-stroke operation and vice versa in a combustion engine the valves of which are controlled by a device according to the invention that operates in accordance with the method according to the invention. 
   SUMMARY OF THE INVENTION 
   The main object of the invention is achieved by means of the initially defined method, having the features that are defined in the characterising portion of patent claim  1 , and by means of a device as initially defined, having the features that are defined in the characterising portion of patent claim  12 . 
   Preferred embodiments of the method that contributes to the achievement of the objects of the invention are defined in the dependent patent claims  2 – 11 . 
   Preferred embodiments of the device that contribute to the achievement of the object of the invention are defined in the dependent claims  13 – 25 . 
   Further features and advantages of the method and the device according to the invention will be seen from the following, detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention shall now be described by way of example with reference to the annexed drawings on which: 
       FIG. 1  is a diagram that shows a first embodiment of a device according to the invention, schematically and in cross section, in a start position, 
       FIG. 2  is a diagram corresponding to the one of  FIG. 1 , but with the device shown during a first stage, 
       FIG. 3  shows the device according to  FIGS. 1 and 2  during the end of the first step, 
       FIG. 4  shows the device according to  FIGS. 1–3  during a continued motion, 
       FIG. 5  shows the device according to  FIGS. 1–4  during a second stage, 
       FIG. 6  shows an alternative embodiment of a part of a circuit of the inventive device, 
       FIG. 7  shows a second embodiment of the device according to the invention, in a first stage, with the circuit shown in  FIG. 6  included, 
       FIG. 8  shows the device according to  FIG. 7 , in a second stage, 
       FIG. 9  shows a third embodiment of the device according to the invention, in a first stage, and 
       FIG. 10  shows the device according to  FIG. 9  in a second stage. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a first embodiment of a device according to the invention, the device being generally designated with  1  and comprising a pressure fluid circuit  2 , a first valve body  3 , which is positioned in a first chamber  4 , a second valve body  5 , which is positioned in a second chamber  6 , a pressure fluid source  7 , a pressure fluid depression  8 , a first valve that comprises an electro magnet  9  and a third valve body  10  driven by said electro magnet, a second valve that comprises a second electro magnet  11  and a fourth valve body  12  driven by the latter. 
   Further, the device comprises a cylinder  13  and an actuator piston  14  which is displacebly arranged in the latter. The pressure fluid circuit  2  communicates with and is arranged to deliver pressure fluid pulses on one side of the piston  14 , for the displacement of the latter. The piston  14  is, via a valve shaft  16 , connected with a valve  17 , to a combustion chamber of a combustion engine. The valve  17  could, however, as well be a valve for injection of fuel to the combustion chamber of a combustion engine or could be connected with or form a piston in a cylinder connected with the combustion chamber for the purposes of accomplishing a variable compression ratio, the position of the valve and variable compression piston respectively in relation to a cylinder of the combustion engine being controlled by the pressure fluid pulses. 
   Preferably, the pressure fluid is gaseous and, most preferably, it is constituted by air or carbon dioxide. In the applications referred to above, the pressure fluid source  7  is, preferably, a compressor with a tank associated thereto, or a pressure tank exclusively, associated to the combustion engine, and the pressure fluid depression is any site that has a lower pressure than the air pressure generated by the compressor or the pressure existing in the pressure tank. 
   The pressure fluid circuit  2  comprises a first branch  18  and a second branch  19 , which branch off from the pressure fluid source  7  and extend to opposite sides of the first valve body  3  in the first chamber  4 . From one of the sides of the first valve body  3  in the first chamber  4  a conduit  20  leads to the pressure fluid depression, and on the other side of the first valve body  3  there is an opening  21 , the periphery of which forms a seat for the valve body  3 , the first chamber, or the high pressure side of the pressure fluid circuit  2 , being able to communicate with the cylinder chamber  15  through opening  21 . The first branch communicates with a first chamber  4  on the side of the first valve body  3  where the opening  21  is located. 
   In the shown embodiment, a first chamber  4  is in constant communication with the pressure fluid source  7  branch  18  via the first branch. 
   The device  1  also comprises a third branch  22  and a fourth branch  23 , which branch off from the pressure fluid depression  8  and pressure fluid source  7  respectively and extend to opposite sides of the second valve body  5  in the second chamber  6 . A fifth branch  24  extends from the pressure fluid depression  8  to one side of the second valve body  5  in the second chamber  6 , and on the other side of the second valve body  5  there is an opening the periphery of which forms a seat for the valve body  5 , the second chamber, or the low pressure side of the pressure fluid circuit, being able to communicate with the cylinder chamber  15  through the opening  25 . 
   The third branch communicates with the second chamber  6  on the side of the second valve body  5  where the opening  25  is located. That of the areas of the valve bodies  3  and  5  onto which the pressure fluid of the pressure fluid circuit acts in one direction, here the closure direction, is larger than the opposite area in chambers  4  and  6  on which the pressure fluid acts in the opposite direction, when valve bodies  3  and  5  rest against the periphery of the openings, i.e. a region or an edge around the openings  21 ,  25 , and close the latter. Moreover, the surface that covers the opening  21 ,  25  is smaller than the first-mentioned area of each individual valve body. The valve bodies  3 ,  5  are designed as disk valves. 
   In the embodiment shown, the second chamber  6  is in constant communication with the pressure fluid depression  8  via the third branch  22 . 
   The device comprises a first electrically activateable valve member for opening/interrupting of the communication between the first chamber  4  and the pressure fluid source  7 , and a second electrically activateable valve member for the opening/interruption of the communication between the first chamber  4  and the pressure fluid depression via said conduit. The first and the second valve members are formed by the first electro magnet  9  and the valve body  10  driven by the latter, said valve body defining a decompressed slide valve. The first valve member is arranged to open when the second valve member closes and vice versa. This is achieved as the valve body  10  is a equipped with at least one channel or passage (not shown) that, upon activation of the electro magnet, is displaced in front of (an exact centring is not required but is preferred) of one of the conduit  20  or the second branch  19 , and is displaced to a position in front of the other one of the conduit  20  and the branch  19  deactivation of the electro magnet  9 . 
   The device comprises a spring element  26  for displacing the first valve body  10  when the electro magnet  9  is deactivated. This will be explained more in detail later. 
   According to the alternative embodiment shown in  FIGS. 6–10 , the device comprises a third valve member formed by the second electro magnet  11  and the valve body  12  associated thereto, said third valve member being provided for opening/interruption of the communication between the first chamber  4  and the pressure fluid depression  8  through the conduit  20 . In this case, the third member is located upstream the second valve member. Upon activation of the second electro magnet  11 , the third valve member opens for communication in the conduit  20 , and upon deactivation of the electromagnet said valve member interrupts the communications. 
   The device, according to all the embodiments shown, further comprises a fourth valve member formed by the second electro magnet  11  and the valve body  12  associated thereto, the fourth valve member being arranged for opening/interruption of the communication between the pressure fluid source  7  and the second chamber  6  through the fourth branch  23 . Furthermore, the device comprises a fifth valve member formed by the second electro magnet  11  and the valve body  12  associated thereto, said fifth valve member being arranged for opening/interrupting the communication between the second chamber  6  and the pressure fluid depression  8 . The fourth valve member is arranged to open when the fifth valve member interrupts and vice versa. This can be achieved by letting the valve body  12  comprise at least one channel or opening that, upon activation of the second electro magnet  11 , is displaced to a position opposite to one of the fourth branch  23  and the fifth branch  24 , and, upon deactivation of the same is displaced to a position in which it is located opposite to the second one of the fourth and fifth branch  23 ,  24 . 
   In the embodiments according to  FIGS. 7–10 , the third valve member is arranged to open in the conduit  20  when the fourth valve member opens for communication between the pressure fluid source  7  and the second chamber  6  through the fourth branch  23 , that is when the fourth member closes for communication between the pressure fluid depression  8  and the second chamber through the fifth branch  24 . 
   The device comprises a spring element  27  for displacing the second valve body  12  when the second electro magnet  11  is deactivated. This will be explained more in detail later. 
   In the third embodiment that is shown in  FIGS. 9 and 10 , the device comprises a sixth branch  28 , through which the first chamber  4  communicates with the pressure fluid source  7 , and a sixth valve member, formed by the second electro magnet  11  and the valve body  12  associated thereto, for the purpose of enabling and interrupting the communication between the first chamber  4  and the pressure fluid source  7  through the sixth branch  28 . The sixth valve member is arranged to open when the fifth valve member opens, i.e. when the fourth valve member closes. 
   Further, the device comprises a sensor  29 , for example an optical or inductive sensor, which registers the position of the actuator piston  16  or any part connected thereto. The sensor  29  is operatively connected with a control unit (not shown) that, based on the signal from the sensor, activates or deactivates the first and the second electro magnet  9 ,  11 . Furthermore, the device comprises a sensor (not shown) for sensing the position of that cylinder of a combustion engine to which the valve actuator is associated. The control unit, which is also operatively connected with this sensor, may then be arranged to control the electro magnets  9 ,  11  based on the information from this sensor. 
   As has been mentioned earlier, the device comprises spring elements  26 ,  27  that act for a redisplacement of the valve bodies  10 ,  12  that have been displaced when the electro magnets  9 ,  11  have been deactivated, that is when the latter let the valve bodies  10 ,  12  loose. In this case, the spring elements  26 ,  27  are pressure fluid regulated as one surface of the valve bodies  10 ,  12  associated thereto can communicate through a branch or a conduit, in this case constantly, with pressure fluid source  7 , and a second, opposite surface can communicate through a further branch or conduit, in this case constantly, with the pressure fluid depression  8 . The high pressure side is, in this case, arranged to counteract the electro magnet and redisplace the valve body  10 ,  12  upon said deactivation. It is also conceivable that one of the surfaces communicates with the atmosphere and that the other surface communicates with the pressure fluid depression, given that the latter has a higher pressure than the atmosphere pressure (we assume that the surfaces are equally large). 
   Apart from the components already mentioned, the device preferably comprises at least one hydraulic brake and locking arrangement, that comprises a hydraulic circuit that consists of a conduit  30  that runs from a pressure source (not shown), which for example may comprise the oil pump of a combustion engine, to a chamber  31 , in which a piston shaft  32  connected with actuator piston  16  penetrate at least some time during the displacement of the actuator piston, preferably when the inlet valve  17  associated to the latter reaches a home position in which it is positioned in its seat in the cylinder top. The device has a valve, preferably a non return valve  41 , that opens for communication between the liquid source and the chamber  31  through the hydraulic liquid conduit  30  and closes in the opposite direction. Furthermore, there is a down stream conduit  33  through which the chamber  31  can communicate with a low pressure side  34  in the hydraulic circuit, for example the oil pan of a combustion engine. 
   The chamber  31  comprises a constriction  37 , through which the piston shaft  32  will move, the constriction  37  or the piston shaft being arranged in such a way that a slot is generated between them, said slot being reduced during said motion. For example, this is achieved by, as here, the end of the piston shaft  32  being conical. In that way, an increasing braking effect is achieved in said direction as the liquid that is forced away by the piston shaft  32  in the chamber  31  get an increasingly small slot for its removal as the piston motion continues. The hydraulic liquid that is heated during the braking is thereby transported away through the downstream conduit  33 . 
   The device comprises an activatable valve  35  for opening/interruption of the communication through the downstream hydraulic liquid conduit  33 . The valve  35  forms a decompressed slave valve and is, through a seventh branch  36 , connected with the second chamber  6 , or with the fourth branch and fifth branch that for the moment opens for pressure fluid communication between the second chamber and pressure fluid source or pressure fluid depression respectively. The pressure fluid in the seventh branch  36  acts against the surface of the valve  35  for the purpose of displacing the latter in a direction towards a position in which it closes. On an opposite surface there is a counter force, in this case constituted by the hydraulic liquid in the downstream hydraulic liquid conduit  33 , for the purpose of displacing the valve to a position in which it closes, i.e. interrupts, the communication with the downstream conduit  33 . The pressures and areas of the surfaces that are effected by pressure fluid and the pressure liquid respectively are adapted in such a way the slave valve  35  opens for communication through the conduit  33  when the seventh branch  36  communicates with the pressure fluid depression  8 , and closes said conduit  33  when the seventh branch  36  communicates with the pressure fluid source  7 . 
   A cycle of the device according to the invention according to a first embodiment will now be explained with reference to, primarily,  FIGS. 1–5 . 
   In  FIG. 1 , the device is shown in a starting position in which the two electro magnets  9 ,  11  and the valve bodies  10 ,  12  associated thereto are deactivated, whereby the engine valve  17  is in its home position, in which it rests against its seat. The pressure fluid source  7  communicates with the first chamber  4  on both sides of the first valve body  3 , and since the side of the body  3  that is directed away from the opening  21  is larger than the area of the opposite side the valve is closed. In a corresponding way, the pressure fluid depression communicates with the second chamber  6  on both sides of the second body  5 , which, accordingly, closes the opening  25  associated thereto. 
   In  FIG. 2 , the device is shown in a position just after that the first electro magnet  9  has been activated following an order from a control unit based on a sensor measurement of the position of the piston in the combustion engine cylinder in question. As a result of the activation of the first electro magnet  9 , the first valve body  10 , interrupts the communication between the first chamber  4  and the pressure fluid source  7  through the second branch. The pressure by which the pressure fluid acts on the first valve body  3  through the first branch makes the valve body move away from the opening  21  and, thereby, permits pressure fluid to flow into the chamber  15  and, thereby, displace the actuator piston  14  and the valve  17  from the home position. The displacement of the valve from the home position takes places, in a conventional way, against the action of a valve spring  40 . 
   Also the second electro magnet  11  has been activated and, thereby, permits a communication between the pressure fluid source  7  and the second chamber  6  through the fourth branch  23 . Thereby, the second valve body  5  is prevented from being displaced from the opening  25  associated thereto, which would result in the fluid being able to flow from the chamber  15  through said opening  25 . 
   In  FIG. 3  there is shown a subsequent stage, during which the first electro magnet  9  has been deactivated and the valve body  10  associated thereto has been redisplaced to its starting position through the action of the spring element  26 . The first valve member is once again open for communication between the first chamber  4  and the pressure fluid source  7  through the second branch  19 , resulting in the first valve body  3 , which is located in the first chamber, having been redisplaced to a position in which it closes the first opening  21 . Due to the continued expansion of the pressure fluid in the chamber  15 , and to the kinetic energy of the displaced mass, the motion of the actuator piston  14  and the valve  17  continues a bit further. 
   It should be noted that the slave valve  35 , through the seventh branch  36  and through the fourth branch  23 , communicates with the pressure fluid source  7 , thereby interrupting any evacuation of hydraulic liquid through the downstream conduit  33 , but that an inflow through the upstream conduit  30  is permitted. This results in the hydraulic circuit being able to act as a lock when the valve  17  reaches its remote position or lower dead, up to the point when the slave valve  35  is once again brought to its opening position. 
   In  FIG. 4 , only the continued motion of the actuator piston  14  and the valve  17  associated thereto towards the remote position is shown, the valve possibly being temporarily locked before the deactivation of the second electro magnet. 
   In  FIG. 5  the device is shown in a subsequence stage, after the deactivation of the second electro magnet  11  and the displacement of the valve body  12  associated thereto through the action of the associated spring element  27  to a position in which the second chamber  6  once again communicates with the pressure fluid depression  8  through the fifth branch  24 . The valve body  5  located in the second chamber  6  has, by the pressure from the fluid in the chamber  15 , been displaced away from the opening  25 , and pressure fluid is permitted to flow out from the chamber  15  through the third branch  22  to the pressure fluid depression  8  while the actuator piston  14  and the valve  17  connected thereto are displaced towards the home position. 
   It should be noted that the slave valve  35  has been displaced to its opening position and, thus, does not any longer lock the valve  17  in its remote position, since the seventh branch  36  is now communicating with the pressure fluid depression  8  through the fifth branch  24 . 
   When the pressure in the chamber  15  has been reduced to such a degree that the valve has reached its home position, the second valve body is closed due to the effect of the gravitational force and/or its upper side once again being brought into communication with the pressure fluid source before the next cycle. Thereby, a return to the starting position of  FIG. 1  is achieved. 
   It should be realized, as also has been shown in the drawings, that each of the valve bodies  10 ,  12  may comprise a plurality of openings or passages for the accomplishment of a communication in the conduits and branches in question in accordance with the teaching of the application in general. 
   It should be realized that the electro magnets used may be a pushing type or pulling type of magnets. 
   In the case in which the device is used for accomplishing a variable compression ratio, the valve  17  should be replaced by a corresponding piston in such a device. The piston is then arranged in a cylinder that directly communicates with the combustion chamber. Also in the case when the device forms an injection valve, the valve  17  should be replaced by a piston. 
   The device may also be used for the expansion of gases, whereby the gas/air pulses that are created can be used in air motors, and in general for the transmission of gas pulses into mechanical movement. 
   A particular advantage of the invention is that it uses a minimum number of electro magnets and valve bodies associated thereto for the opening/interruption of the described conduits and branches in the pressure fluid circuit  2 . Accordingly, one electro magnet  9  is used for the opening/closure of the second branch  19  and the conduit  20  through a displacement of the valve body  10  associated thereto. A further electro magnet  11  is used for the opening/closure of the forth and fifth branch  23 ,  24  and of the conduit  20  and the sixth branch  28  through the displacement of the valve body  12  associated thereto.