DK176152B1 - Method of activating an exhaust valve for an internal combustion engine and such an exhaust valve - Google Patents

Description

---- ^ DK 176152 B1

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method of activating an exhaust valve for an internal combustion engine, wherein the exhaust valve is opened by sliding the length of a control valve to connect a high pressure port to a first pressure chamber in an actuator in which an actuator piston is displaced in the direction of the exhaust valve. of the open position thereof, and where the slider of the control valve is longitudinally displaced to connect a low pressure port with the first pressure chamber 10 when the exhaust valve is to be closed.

From US Patent 3,209,737 such an exhaust valve is known in which the control valve is actuated by a cam on a camshaft or electronically by a solenoid valve. The control valve connects the first pressure chamber to the high-pressure port during the opening movement of the exhaust valve and continuously to the low-pressure port during its closing movement. The movements of the exhaust valve are thus controlled by the magnitude of the hydraulic pressures and by the length of time during which the pressures act on the actuator 20 having both an open area and a closing area.

The control valve has in fact only a position for opening the exhaust valve and a position for closing the exhaust valve, and is controlled at the time of opening and closing movements, respectively, with the hydraulic force on the actuator piston initiating the movement of the spindle and then the movement continuing while the control valve continues. remains standing in the open position. In operation, variations in the magnitude of the hydraulic pressure may occur, leading to 30 variations in the speed of movement of the spindle. The exhaust valve is controlled to move optimally at a particular engine load, such as at full load, and its open speed is not variable with the engine speed, so that at other engine loads it does not open at optimum timing. The braking of the spindle at the end of the closing movement is effected by the hydraulic fluid sprinkling through a slot caused by a pin on the spindle being pressed into a bore in a stationary housing.

It is an object of the present invention to provide a method which allows for more precise control of the exhaust valve, including control during its movement.

To this end, the invention is characterized in that the spindle valve spindle is displaced proportionally, such as in the ratio 1: 1, with the longitudinal displacement of the control valve slider, that the spindle is positionable in selected positions between fully open and fully closed position and that the spindle valve spindle is moved in it. 15 at the same time as the control valve slides between the exhaust valve closed and open positions.

By longitudinally displacing the spindle proportionally to the slider, an adjustment of the slider is transferred to a corresponding movement of the exhaust valve. Thus, there is a direct correlation between the instantaneous position of the slide and the instantaneous position of the valve stem, and thus the adjusting movements of the exhaust valve depend only on the setting of the slide and not influenced by variations in the hydraulic pressure or the periods during which the slide is stationary in a particular setting.

The slider can position the spindle in intermediate positions so that the spindle movement can be directly controlled while the spindle is between the outer positions. Furthermore, since the spindle is moved essentially 30 at the same time as the slider, the exhaust valve can be moved as desired in the motor cycle, independent of the current engine speed.

It is preferred that the termination of the exhaust valve closing movement is actively controlled by the control valve instead of braking the spindle with throttling, as the throttling results in an energy loss. If the control valve controls the closing of the closing movement and thus the slowing down of the spindle, the amount of energy that the high pressure hydraulic fluid delivers to the actuator of the exhaust valve 5 is reduced. The actuative design of the actuator is simplified in that there is no need for related, precisely designed parts to form the throttle gap.

Furthermore, it is possible that the speed of movement of the ejection spindle in one predetermined part of the movement path is changed from one motor cycle to the next. For example, the speed of movement of the exhaust valve may be increased at the start of the opening movement, which accelerates the valve opening. A large acceleration away from the closed position with fast spindle movement to the open position leads to less heating of the valve plate and of the stationary valve seat, because an advantageously large outflow area is quickly obtained. The ability to change the exhaust valve movement speeds during engine operation 20 permits continuous adaptation to the current operating conditions.

The method according to the invention provides an advantageous option to vary the position in which the spindle is kept open as desired, since the open movement of the ejector valve can be stopped in an open intermediate position before the fully open position is obtained. This can save on the consumption of hydraulic fluid and thus energy for pressurizing it. When the engine is running at partial load, the amount of exhaust gas is less per engine 30 cycle, and the engine rpm may be lower depending on the engine type, allowing longer exhaust gas emissions. Both conditions allow for reduction of the outflow area.

The possibility of precise control of the spindle movement 35 can conveniently be utilized for the spindle at DK 176152 B1 - ^. ___ 4 The closing of the closing movement is held in a ventilation position in which there is a ventilation gap between the seat surfaces of the exhaust valve, during a holding time, after which the spindle is moved to the fully closed position.

5 By keeping the exhaust valve open for a period of time, called the holding time, in almost fully closed position, outflow of relatively cold air passes past the seat surfaces subjected to vigorous cooling. The accompanying lowering of the average temperature of the valve materials leads to a longer service life of the exhaust valve, and possibly to other, cheaper valve seat materials can be used. The durability of the valve seats is further improved in that any residual particle can be blown away by the powerful flow of ventilation air, thereby reducing the appearance of impression marks.

The holding time may conveniently be in the range of 4 ms to 50 ms. This range is suitable for slow or medium speed motors with large 20 bore. If the holding time is less than 4 ms, the desired cooling may be too low and if the holding time exceeds 50 ms, the air consumption for the cooling may be too large.

It is preferred that the spindle in the ventilation position be held with the seat surfaces spaced apart from the range of 0.02 mm to 0.50 mm, which allows for a sonic velocity of air flow through the ventilation slot, and preferably in the range of 0. 05 mm to 0.2 mm, which limits the amount of flow of outflow air so that the compression pressure remains substantially unaffected.

It is possible to further reduce the occurrence of impression marks by first moving the spindle at the end of the closing movement to a substantially closed position and immediately thereafter moving briefly in the opening direction and then to the fully closed position. By first making the almost complete closure, any particles are crushed between the valve seat surfaces for dusty material, and when the spindle 5 is then briefly opened, a vigorous ventilation flow is produced which blows the crushed dusty material away with the exhaust gas. By the subsequent complete valve closure, the seat surfaces are cleaned of particles and the impression marks are prevented from forming.

The combined cooling and purification of the seat surfaces can be limited in time to limit the discharge of charge air to the short-term movement in the open direction and the movement to fully closed position 15 within a period of less than 1/10 of the period in which the exhaust valve is open.

The present invention further relates to an exhaust valve for an internal combustion engine, comprising a valve spindle with a hydraulic actuator having a stationary cylinder having at least a first pressure chamber and associated actuator piston, and a control valve which can at least connect the first pressure chamber with a high-pressure port or a low-pressure port in the control valve of the housing.

A more precise control is possible by designing the exhaust valve such that the control valve housing with the high and low pressure ports is longitudinally displaceable and that the longitudinal displacement of the control valve housing is proportional to the longitudinal displacement between open and closed position 30 of the exhaust valve spindle. The displacement of the housing together with the spindle means that the control valve can simply be hydraulically inactive when the spindle and thus the housing is in the desired position, which is determined by the current position of the slider.

It is preferred that the housing of the control valve is "longitudinally displaceable relative to the spindle of the exhaust valve, which causes the housing and the spindle to move in identical movements, i.e. proportionally in the ratio of 1: 1. Alternatively, the displacement of the spindle may be 5 is reinforced relative to the displacement of the control valve housing, for example such that the displacements occur proportionally in a predetermined ratio, such as 1: 2 or 1: 3, so that the slides of the control valve can have relatively small stroke length.

10 In a particularly simple embodiment, the control valve housing is constituted by the actuator piston. In this way, by allowing the actuator itself to be directly forcibly controlled by the slider of the control valve without any intermediate connecting elements, the control of the exhaust valve 15 becomes direct and without delaying elements. Due to the minimal number of parts in the control, the reliability is very high.

In one embodiment, the slider of the control valve is slidably mounted on the movable magnetic portion of a linear motor whose stationary coil portion is mounted coaxially in extension of the spindle of the exhaust valve. The use of a linear motor for adjusting the slider of the control valve provides an advantageous simple design of the mechanical elements because the linear motor can be freely controlled with respect to both the instantaneous position of the moving part and its speed on the basis of electronic signals from a control unit. As an alternative, the slider may be movable by a cam on a camshaft, but this requires mechanical synchronization between the camshaft and the crankshaft of the engine and limits the ability to operate freely to change the movement pattern of the exhaust valve during the motor cycle.

When using a linear motor, it is preferred that the movable portion of the linear motor has a greater stroke than the maximum travel of the exhaust valve between closed and fully open position. This provides very good opportunities to compensate for changes in the length of the exhaust valve due to wear, varying temperature conditions 5 etc. and also provides more precise control because a linear motor may have variations in its characteristics in the areas near the outer positions.

The invention will now be explained in more detail with reference to the very schematic drawing, in which FIG. 1 is an illustration of an exhaust valve according to the invention; FIG. 2-4 examples of movement steps performed with the exhaust valve of FIG. 1, and FIG. 5 shows a section of an embodiment shown in more detail.

In FIG. 1, the top of a cylinder 1 is seen in an internal combustion engine which may be a two or four stroke engine with a large cylinder bore, such as a bore of at least 200 mm and typically a bore in the range of 20 240-1200 mm. For example, the engine may be a direct-pressure, two-stroke cross-head motor for propelling a ship or for stationary power generation. An exhaust valve 2 is mounted in the upper part of the cylinder in a cylinder cover 3. The cylinder is longitudinally flushable, ie. there are rinsing air ports in a lower section of the cylinder. The exhaust valve may also be located other than centrally in the cylinder cover. For example, it may be located in the side wall of the cylinder or there may be multiple exhaust valves mounted in the same cover.

The exhaust valve comprises a spindle 4 with a valve plate having an upwardly extending circumferential seat surface which may be sealingly against a downwardly stationary seat surface of the cover 3. In the closed position, the exhaust valve interlocks the connection between 8 DK 176152 B1 and an ejection passage 6, and in the open position the spindle 4 is longitudinally displaced downward.

A high pressure line 7 with hydraulic fluid at a high pressure, such as in the range of 100-500 bar, typically 150-300 bar, leads to a high pressure port 8 (see the example in Figure 5) in a control valve housing, as shown in An embodiment is integrated with the spindle 4. A low pressure line 10 connects a low pressure port 11 in the control valve housing with a drain or return line for hydraulic fluid used. A drain at the top of the cover 3 at the bottom of an outer valve housing 12 may be connected to the low pressure conduit 10 to remove any leakage fluid. The low-pressure line may be located coaxially outside the high-pressure line, which is especially advantageous for large motors, where there may be several meters of lead path from the exhaust valve housing down to a high pressure line longitudinally on the engine, which can also supply hydraulic drives for fuel injection with 20 hydraulic fluid. In addition to achieving better space conditions by placing the low and high pressure lines coaxially, the low pressure line also acts as a shielding jacket around the high pressure line in the event of a breach thereof.

In the illustrated embodiment, an air spring piston 25 13 is fixed to the spindle 4 and slidably mounted in an air spring cylinder 5 so that under the piston is an air spring chamber 14 provided with compressed air from an air pressure line 15. The air spring continuously affects the spindle 4 with an upward force. in the direction of the 30 closed position.

An electronic control unit 16 associated with the current cylinder receives information from a signal generator 17 for when to open and close the exhaust valve. This may be an activation signal determined by another control unit, which may be central to the entire engine, or information about the crankshaft instantaneous rotation position for use of opening and closing times in the control unit 16 on the basis of signals received from another signal source 5 18, such as information about the instantaneous load of the engine and, optionally, that the engine is running in a certain of several predetermined operating states requiring actuation of the exhaust valve in a certain way that deviates from the standard operation.

The control unit 16 provides, via a signal line 19, setting signals for the exhaust valve as required during the movement of the spindle between closed and open position, and via a line 20 the control unit can receive a position signal from a sensor measuring the instantaneous position of the spindle 15, either on the spindle itself or on an element connected to a slider 21 in the control valve.

An electromechanical transducer 22 converts the electrical signals from the controller to a linear displacement of the slider in the control valve. The control valve 20 is located in a not shown embodiment separate from the spindle 4, which means that there are relatively long connecting channels between the control valve gates and the pressure chambers in the actuator described below. However, the separation allows the longitudinal axis of the control valve to be oriented in directions other than coaxial with the longitudinal axis of the spindle, such as in a horizontal direction. The separation also allows the transducer 22 to be a unit which does not move the stomach to the spindle, but instead performs a short movement which, in an amplifier unit, translates into a linear motion of the same size as the desired displacement of the spindle 4.

For example, it is possible that the slider's displacement is converted into the amplifier unit to four times the displacement of the spindle, ie. that the slider and the spindle 35 are displaced lengthwise in a ratio of 1: 4.

10 DK 176152 B1

By the length of the spindle 4 being proportional to the displacement of the slider and the slider and thus the spindle being positioned at selected intermediate positions, the control unit 16 can brake or accelerate the spindle at any time of its movement via the electromagnetic transducer 22. The selected positions may be predetermined intermediate positions or may be positions calculated continuously by the control unit on the basis of the current operating state of the engine and / or 10 on the basis of measurements of the actual valve flow path. Referring to FIG. 2, an example is shown of a course of movement in which the curve shows the downward displacement of the spindle 1 as a function of time t. continuing smoothly to the point b, where the speed of the slider is slowed so slowly that the closing force 20 of the air spring is substantially sufficient to slow the spindle 4 to a standstill in the fully open position lmax at the point c. The spindle is then stationary until the closing movement begins at point d, as transducer 22 begins to slide the slider back in the direction of the initial position. As the spindle approaches the closed position, the control unit 16 can slow the speed of the slider until the spindle is stopped at the point e at such a short distance from the closing position that there is a ventilation gap of 30, for example, 0.3 mm between the seat surfaces. In this narrow gap, the outflow air has sonic velocity, which produces vigorous cooling, but the mass flow of air is very small because the gap is very narrow. The cooling can be carried out without noticeable loss of compression pressure in the combustion chamber 35 above the piston 23. The exhaust valve is completely closed at DK 176152 B1 ^^ 11 point f after a holding time which can be freely adjusted by the control unit depending on empirical values for the relationship between the current operating state and the cooling demand. , or can be set based on actual measurements of the seat material temperature, which can conveniently be done by means of temperature sensors located in the stationary valve seat.

If, under certain operating conditions, a faster cylinder emptying or a more powerful flushing 10 with flushing air is desired, the control unit 16 can wait longer to slow down the spindle 4 and instead make a stronger braking from point b 'as indicated by the dotted line. Similarly, with a dashed line, it is shown that the closing movement as required, eg 15 due to temporarily changed operating conditions, can be accelerated by moving the slider more quickly towards the initial position until valve closure at point f '.

In FIG. 3, a closure process is seen, where the spindle is first briefly at the point f '' brought to the closed position to immediately reopen to the ventilation position marked at point e. This, as mentioned above, gives a crushing and blowing of any particles trapped between the closing valve seats. Valve seats are only subjected to excessive force when the combustion pressure starts to act on the valve plate, and the temporary valve closure therefore cannot load the seat material so hard that impression marks are formed. After a suitable holding time, the spindle 30 4 is moved to the fully closed position illustrated at point f '".

When the engine is running at partial load, only a small amount of gas must be ejected per engine speed. Therefore, there is no need to move the spindle to the fully open position. By allowing the controller 16 to activate the slider 1 / DK 176152 B1 12 for faster braking to a standstill, as illustrated in FIG. 4, the spindle 4 is moved only a short distance downward, which reduces the consumption of hydraulic fluid. The shorter open movement can also be selected in 5 cases when the control unit receives an alarm signal about abnormally small amount of hydraulic fluid in line 7.

In the following description of other embodiments of the invention, for simplicity, the same reference numerals as above are used for features having the same function.

In FIG. 5, the top of the spindle 4 is shown integrated with both the actuator piston part and the control valve. In the left half of the figure, the control valve and actuator are shown in the starting position where the exhaust valve is closed, and 15 in the right half in an open position. The spindle 4 is pressure-sealed up into a lower section 25 of a central bore in an actuator housing 24 which carries a top cover 26 with a downwardly tubular sheath 27 for the transducer 22 mounted coaxially with the spindle 20, for example. be a linear motor type LinMot (trademark) of the brand Sulzer Electronics AG, Switzerland and model P01-23 x 160, which can have a maximum stroke length of up to 140 mm. The transducer has a stationary coil portion and a displaceable movable magnetic portion 31 in the form of a magnet on a rod, on whose lower end a slider in the control valve is mounted longitudinally displaceable relative to the portion 31.

In the actuator housing is fixed an end bottom 28 for a first pressure chamber 29, and an annular wall 30 in the top 30 of the spindle 4 protrudes sealingly between a cylindrical inner surface 37 of the end floor and a cylindrical outer surface of the casing 27. An actuator piston comprises a first piston part 32 with an upwardly opening first area 33 determined by the outer and inner diameter of the annular piston 35 and a second piston part 34 having an upwardly opening open area 35. In its initial position, the first piston portion abuts an annular upwardly facing surface of the second piston portion, the total open area corresponds to the area of the annular 5 cross-section bounded by the outside of the piston portion 32 sliding pressure-sealing along the chamber interior and the exterior of the wall 30 sliding pressure-sealing along the cylindrical inner surface of the end 37.

During the downward movement of the actuator piston 10, the first piston part 32 lands on a shoulder 38 in the inside of the actuator cylinder and is stopped, after which only the second piston part continues the movement. During this remaining portion of the open movement, the open area is reduced to the area of the annular cross section 15 delimited by the outside of the piston member 34 sliding pressure-sealing along the inside of the cylinder 36 and the outside of the wall 30.

The actuator piston further has a closure area 39 which corresponds to the area of the annular cross section 20 defined by the outside of the spindle 4 which slides pressure-sealing along the lower portion 25 of the actuator housing and the outside of the piston member 34 which slides along the inside 36. The closure area is located in another pressure chamber 4 0.

The high pressure conduit 7 is connected to the actuator housing at the second pressure chamber 40 and a duct 41 leads to the high pressure port 8. The low pressure conduit 10 is connected to the actuator housing cavity over the end floor 28 and a duct 42 connects the low pressure port 11 to the cavity.

The control valve slides 21 have a smaller diameter center section and two cylindrical end portions which are pressure-sealing against the inside of a cylindrical bore in the control valve housing 45, which in the embodiment shown in FIG. 5 is formed directly in the upper section of the spindle 4. A control port is permanently connected to the first pressure chamber via a short duct 43 Γ -Ζ - - DK 176152 B1 14. In the neutral position of the control slider, the two end sections of the slider can precisely block the high and low pressure ports. When the slider 21 is displaced downwardly relative to the actuator 5 piston, the high pressure port is exposed so that fluid flows into the first pressure chamber, causing the actuator piston with the spindle 4 to shift downward until the high pressure port is closed again. When the slider 21 is displaced upwardly relative to the actuator piston, the low pressure port 10 is exposed so that fluid flows out of the first pressure chamber, causing the actuator piston with the spindle 4 to shift upwardly until the low pressure port is closed again. The actuator piston is thus forcibly controlled to precisely follow the shear movements of the slider 15 21.

As a result of the forced control, the opening and closing areas of the actuator piston can be made relatively large, thereby providing a power surplus for adjusting the spindle 4, which ensures quick and precise adjusting movements. Since there may be a power surplus, the size of the piston areas can be calculated from the minimally adjustable pressure in the high pressure line 7, so that pressure variations in the line can only lead to increased power surplus.

25 When the actuator performs adjusting movements, there is a flow of liquid which cools the actuator.

The FIG. 5 with the control valve built into the actuator piston gives the advantage that the channel 43 from the control port to the chamber 29 has a minimum length of 30, so that the control connection between the slider setting and the actuator piston movement becomes directly inelastic and with minimal power loss.

A drainage channel 44 may keep the space under the first piston portion 32 free of any leaking fluid. The embodiment of FIG. 5 need not be used with a --- ------ I - · DK 176152 B1 15 air spring on the spindle 4. If an air spring is used, the first closing area 39 may be omitted or, when determining the area, size is taken into account that there is also a closing force from the 5 air spring.

The aforementioned methods for holding the exhaust valve in a final cooling ventilation position and for crushing and blowing away any particles are also applicable to other actuators, such as a cam controlled actuator, but the above embodiments are particularly good for practicing the method because is very precise acting.

Performing the Ise s shape shown in FIG. 5 can also be modified. The actuator piston may, for example, be manufactured separately and separately from the spindle 4 and mounted in extension thereof, such as by means of a bolt joint, a screw-in screw or a locking pin inserted in a transverse bore passing through both parts or by another form for mechanical fixation 20 in the axial direction. In addition, in the actuator piston itself, the housing of the control valve may be designed as a separate element which is inserted and fixed in a bore in the actuator piston. For example, the fixing can be done by the outside of the housing being tapered and the bore in the piston having a corresponding tapered surface against which the housing is pressed firmly or the parts can be shrunk or screwed together.

Claims (14)

A method of activating an exhaust valve (2) for an internal combustion engine, wherein the exhaust valve is opened by sliding the length of a control valve (21) longitudinally to connect a high pressure port (8) to a first pressure chamber (29) in an actuator , in which an actuator piston (32, 34) is displaced together with the spindle (4) of the exhaust valve in the direction of its open position, and wherein the slide of the control valve (21) is longitudinally displaced to connect a low pressure port (11) to the first pressure chamber ( 29) when the exhaust valve is to be closed, characterized in that the spindle (4) of the exhaust valve is displaced proportionally, such as in the ratio 1: 1, with the longitudinal displacement of the control valve slider (21), that the spindle is positionable in selected positions between fully open and fully closed position and that the exhaust valve spindle (4) is moved substantially simultaneously with the control valve slider (21) between the exhaust valve open and closed positions. The method according to claim 1, characterized in that the termination of the closing movement of the exhaust valve is actively controlled by the control valve. Method according to one of claims 1-2, characterized in that the speed of movement of the exhaust valve 25 in one predetermined part of the path of movement is changed from one motor cycle to the next. Method according to one of Claims 1 to 3, characterized in that the opening movement of the exhaust valve is stopped in an open intermediate position before the fully open position is reached. Method according to one of claims 2-4, characterized in that the spindle (4) is held, at the end of the closing movement, in a ventilation position, in which there is a ventilation gap between the seat surfaces of the exhaust valve 35, during a holding time, after which the spindle is moved to fully closed position. . Method according to claim 5, characterized in that the spindle (4) is held in the ventilation position for a holding time in the range of 4 ms to 50 ms. Method according to claim 5 or 6, characterized in that the spindle (4) is held in the latent position with the seat surfaces at a distance spaced from the range of 0.02 mm to 0.50 mm, preferably from 0, 05 mm to 0.2 mm. Method according to one of claims 3-7, characterized in that the spindle (4) at the end of the closing movement is first moved to the substantially closed position and immediately thereafter moved briefly in the opening direction and then to the fully closed position. The method according to claim 8, characterized in that the short-term movement in the open direction and the movement to the fully closed position is carried out within a period of less than 1/10 of the period in which the exhaust valve is open. Exhaust valve for an internal combustion engine, comprising a valve stem (4) with a hydraulic actuator having a stationary cylinder having at least a first pressure chamber (29) and an associated actuator piston (32, 34), and a control valve as in can at least connect the first pressure chamber to a high pressure port (8) or a low pressure port (11) in the control valve housing, characterized in that the control valve housing with the high and low pressure gates is longitudinally displaceable and that the longitudinal displacement of the control valve housing is proportional to the longitudinal displacement between open 30 and closed position of the exhaust valve spindle (4). Exhaust valve according to claim 10, characterized in that the housing (45) of the control valve is longitudinally displaceable relative to the spindle of the exhaust valve. Exhaust valve according to claim 10 or 11, characterized in that the housing (45) of the control valve is constituted by the actuator piston. DK 176152 B1 Exhaust valve according to one of claims 10-12, characterized in that the slider (21) of the control valve is longitudinally mounted on a movable magnetic part (31) of a linear motor, whose stationary coil part is mounted coaxially in extension of the spindle (4) of the exhaust valve. Exhaust valve according to claim 13, characterized in that the movable part (31) of the linear motor has a greater stroke than the maximum 10 travel of the exhaust valve between closed and fully open position.