Valve actuation device for an internal combustion engine
The dual control surface valve actuation device addresses inefficiencies in existing systems by allowing variable valve timing based on engine conditions, enhancing efficiency and performance through optimized valve operation.
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- SCANIA CV AB
- Filing Date
- 2012-04-30
- Publication Date
- 2026-05-21
AI Technical Summary
Existing valve actuation systems in internal combustion engines do not allow for optimal opening and closing times of intake and exhaust valves across varying operating conditions, leading to inefficiencies and performance limitations.
A valve actuation device with a dual control surface mechanism, utilizing a connecting element to switch between two motion transmission mechanisms, enabling variable opening and closing times of valves based on engine operating parameters, and incorporating a hydraulic piston to bridge clearance for enhanced control.
Enhances engine efficiency by optimizing valve operation under different load and speed conditions, reducing energy losses, and improving exhaust gas temperature and boost pressure management.
Smart Images
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Abstract
Description
BACKGROUND OF THE INVENTION AND STATE OF THE ART
[0001] The subject of the present invention is a valve actuation device for an internal combustion engine according to claim 1.
[0002] The intake and exhaust valves (hereinafter also referred to as exhaust valves) of internal combustion engines are normally controlled by a rotating camshaft, whose cams act as control surfaces for a cam tappet. The cam tappets thus perform essentially vertical stroke movements, which, via suitable motion-transmitting components, cause stroke movements of the intake and exhaust valves. The opening and closing movements of the intake and exhaust valves are executed when the pistons of the various cylinders of the internal combustion engine are in fixed, predetermined positions. These fixed positions for opening and closing the valves are a compromise chosen to ensure that the internal combustion engine functions well regardless of load and speed. Consequently, the intake and exhaust valves do not always open and close at optimal times in all operating conditions of the internal combustion engine.
[0003] For example, controlling the intake valve closing timing can be advantageous for several reasons. Such control allows for the optimization of cylinder filling at different engine speeds, which is desirable under high engine loads. Controlling the intake valve closing timing also allows for control of the effective compression ratio. Advancing the intake valve closing time from the point that yields optimal filling results in a later start to compression, meaning that compression occurs over a shorter portion of the piston's stroke. The subsequent expansion, however, remains unchanged. This results in a higher expansion ratio than the compression ratio, which can improve efficiency under certain operating conditions.However, it is not possible to close the intake valves late under all operating conditions. For example, when starting an internal combustion engine with compression ignition, the compression ratio becomes so low that ignition does not occur.
[0004] Exhaust aftertreatment equipment often requires a high exhaust gas temperature to function properly. When the internal combustion engine is under light load, the airflow through the engine is high compared to the amount of fuel supplied, resulting in a low exhaust gas temperature. The exhaust gas temperature can be increased by reducing the amount of air supplied to the engine. A throttle valve is typically used to reduce the amount of air supplied to the engine. However, using a throttle valve results in losses. Controlling the closing time of the intake valves is an alternative way to control the airflow supplied to the engine.
[0005] Controlling the opening timing of the exhaust valves can be used to increase the exhaust gas temperature. By opening the exhaust valves earlier than normal, expansion is halted at a higher temperature, resulting in a higher exhaust gas temperature. In turbocharged combustion engines, the exhaust turbine is sized to generate high boost pressure at low engine speeds. This causes the turbine to run at excessively high speeds at high engine speeds and under heavy loads. To prevent this, a portion of the exhaust gas flow is diverted around the turbine via a wastegate. A wastegate is less necessary if the opening timing of the exhaust valves is delayed. This also increases efficiency.
[0006] In turbocharged combustion engines, opening the exhaust valves earlier provides more energy to the exhaust turbine, thus increasing the boost pressure. Opening the exhaust valves later provides more energy to the combustion engine, thereby increasing its efficiency. Consequently, the efficiency and power output of combustion engines can be modified by varying the opening timing of the exhaust valves. In transitional conditions, opening the exhaust valves earlier can also be advantageous to achieve a faster increase in boost pressure.
[0007] DE 42 13 855 A1 discloses a valve train for a variable opening characteristic of a valve of an internal combustion engine. A first cam and a second cam, as well as a first rocker arm, are provided, which serves to transmit a movement resulting from a change in the circumferential geometry of the first cam to the valve. Furthermore, a second rocker arm is provided to transmit a movement resulting from a change in the circumferential geometry of the second cam to the first rocker arm, provided a locking device is activated.
[0008] US 2009 / 0266317 A1 discloses an arrangement for actuating two valves. A first actuating surface and a second actuating surface are formed on a cam. The first actuating surface is configured to contact a first part of a first rocker arm, thereby causing the first rocker arm to move and actuate the first valve. The second actuating surface is configured to contact a second part of a second rocker arm, thereby causing the second rocker arm to move and actuate both valves. A contact surface of the first rocker arm engages a yoke above the first valve. A contact surface of the second rocker arm engages the yoke centrally between the two valves. The yoke is pivotally mounted on the second valve and on the contact surface. The contact surface is formed on an actuated pin of the first rocker arm.
[0009] DE 10 2004 053 807 A1 relates to a variable valve train device that can be operated in a low-speed mode, in which a low-speed rocker arm is moved back and forth by a low-speed cam element over a roller or sliding piece to open or close an intake valve, and in a high-speed mode, in which a high-speed rocker arm is moved back and forth by a high-speed cam element over a roller or sliding piece, wherein a switching mechanism section on the side of the low-speed rocker arm is pressed by a switching mechanism section on the side of the high-speed rocker arm, thereby moving the low-speed rocker arm back and forth to open or close the intake valve.The axis of the switching mechanism section is arranged in the axial direction of the rocker arm shaft at the center of the width of the roller or sliding piece to prevent tilting of the high-speed rocker arm. SUMMARY OF THE INVENTION
[0010] The purpose of the present invention is to provide a valve actuation device for an internal combustion engine which enables a variable opening time and / or a variable closing time of two valves, which may be intake valves or exhaust valves.
[0011] This purpose is achieved by the valve actuation device in the embodiment described at the beginning of this description, which is characterized by the features specified in claim 1. According to the invention, the camshaft therefore has a first control surface with which normal opening and closing of the valves is possible, and a second control surface which can be connected to a component of the first motion transmission mechanism via a second motion transmission mechanism by moving a connecting element into a second position. The valves can be intake valves or exhaust valves. Under certain operating conditions, it is advantageous to give the intake and exhaust valves a different opening and closing time than the normal one.When the connecting element is in the first position, control movements are transmitted to the valves only from the first control surface via the first motion transmission mechanism. When the connecting element is in the second position, the second motion transmission mechanism is connected to a component of the first motion transmission mechanism such that the control surface that produces the greatest valve stroke at any given time is used to actuate the valves. Consequently, when the connecting element is in the second position, control movements can be transmitted to the valves from either the first or the second control surface. The second control surface can be configured to actuate the valves entirely when the connecting element is in the second position.Alternatively, the second control surface can be designed to actuate the valves only at specific camshaft angles where it is advantageous to keep the valves more open than normal. With the aid of the connecting element, the second motion transmission mechanism, and the second control surface, the valves can therefore be kept open at a greater number of camshaft angles than normal.
[0012] According to the present invention, the second motion transmission mechanism has sufficient clearance to prevent the control movements of the second control surface from being transmitted beyond this clearance. It includes a movable connecting element that maintains the clearance in the first position and bridges it in the second position, allowing control movements from the second control surface to be transmitted beyond the clearance. The clearance is advantageously located between two components of the second motion transmission mechanism. The connecting element may include a retractable piston. A retractable hydraulic piston can be quickly and easily moved from a retracted position to an extended position, where the clearance is bridged. In the extended position, a hydraulic piston is essentially a rigid unit that bridges the clearance.However, other designs of the connecting element can also be used.
[0013] According to the present invention, the first motion transmission mechanism and the second motion transmission mechanism have at least one common component connected to the valve. To reduce the number of components, it is advantageous for the motion transmission mechanisms to have at least one common component connected to the valve. Since two valves are activated, the common component is a valve head, and the second motion transmission mechanism has a rocker arm that can be connected to the valve head. In this case, the first motion transmission mechanism has a first rocker arm that can be connected to the valve head, and the second motion transmission mechanism has a second rocker arm that can be connected to the valve head.Rocker arms are a component used to transmit control movements from camshaft control surfaces to valves for actuating those valves. If an overhead camshaft is used, the rocker arms can receive control movements directly from a camshaft control surface. If inverted camshafts are used, the rocker arms can receive control movements from a pushrod and cam tappet that are in contact with a camshaft control surface.
[0014] According to one embodiment of the present invention, the aforementioned clearance of the second motion transmission mechanism is located between the rocker arm and the valve head. It is easy to create a clearance of a suitable size at this point. The connecting element is advantageously arranged in the rocker arm. Alternatively, the connecting element can be arranged in the valve head. However, the aforementioned clearance can also be arranged at any point in the second motion transmission mechanism.
[0015] According to another embodiment of the valve actuation device, used solely for illustrative purposes, the first motion transmission mechanism and the second motion transmission mechanism share a common component in the form of a rocker arm. In this case, the second motion transmission mechanism can have a second rocker arm that can be appropriately connected to the common rocker arm. This allows the aforementioned clearance between the rocker arms to be created. The connecting element can be located in one of the rocker arms.
[0016] According to a further embodiment of the present invention, the valve actuation device has a control unit that serves to move the linkage mechanism into the first or second position using information relating to at least one operating parameter of the internal combustion engine. The intake and exhaust valves do not always open and close at optimal times in all operating conditions of the internal combustion engine. For example, using information about the load and speed of the internal combustion engine, the control unit can decide whether it is better to move the linkage mechanism into the first or the second position.
[0017] According to a preferred embodiment of the present invention, the second control surface is configured relative to the first control surface such that the valve closes at a later time when the linkage mechanism is in the second position. Under certain operating conditions, it may be advantageous, in particular to close an inlet valve at a later time. Under such conditions, the linkage mechanism is moved into the second position. The second control surface can also be configured relative to the first control surface such that the valve opens at an earlier time when the linkage mechanism is in the second position. Under certain operating conditions, it may be advantageous, in particular to open the exhaust valve at an earlier time than during normal operation. Under such conditions, the linkage mechanism is moved into the second position. DRAWING DESCRIPTION
[0018] Preferred embodiments of the invention are described below as examples with reference to the accompanying figures. The following applies to the figures: Fig. Figure 1 shows a valve actuation device according to the present invention. Fig. Figure 2 shows the camshaft with the two control surfaces in Fig. 1. Fig. 3 shows the valve head of Fig. 1 in detail. Fig. Figure 4 shows the valve lift of a valve as a function of the angular position of the camshaft. Fig. Figure 5 shows another embodiment of the valve actuation device, serving only for illustrative purposes. DETAILED DESCRIPTION OF PREFERRED EXECUTIONS OF THE INVENTION
[0019] Fig. Figure 1 shows part of a cylinder of an internal combustion engine. The cylinder has a combustion chamber 1, the size of which is determined by a movable piston 2. A valve 3 is visible in the cylinder. The valve 3 can be an intake valve, which controls the supply of air to the combustion chamber 1, or an exhaust valve, which controls the removal of exhaust gases from the combustion chamber 1. In this case, the cylinder has two intake valves and two exhaust valves, although only one valve is shown in the diagram. Fig. Figure 1 shows that each of the valves 3 is connected to a valve spring 4, which exerts a force to keep the valves 3 closed. In this embodiment, the internal combustion engine is equipped with a bottom camshaft 5, which rotates around the axis of rotation 5a at a speed that depends on the speed of the internal combustion engine. Alternatively, the internal combustion engine can be equipped with an overhead camshaft.
[0020] Fig. Figure 2 shows the camshaft 5 from a different perspective. The camshaft 5 has a peripheral first control surface 6 and a first cam tappet 7. The first cam tappet 7 has a contact element in the form of a first rolling element 8, which rolls in contact with the first control surface 6. A substantially vertically mounted first pushrod 9 is pivotally connected to the first cam tappet 7 at its lower end. The first pushrod 9 is connected at its upper end to a first joint element 10, which is rigidly mounted to a first rocker arm 11. The first joint element 10 has a spherical section that is located in a spherical socket of the first pushrod 9. The first joint element 10 also has an adjusting screw and a nut for adjustable fastening of the joint element 10 to the first end of the first rocker arm 11. The first rocker arm 11 is pivotally mounted in a central section about a first joint 12.The first rocker arm 11 has a contact area 13 at a second end on the opposite side of the joint 12, which serves to transmit movements to a valve head 14.
[0021] Fig. Figure 3 shows the valve head 14 in detail. The valve head 14 has a central section 14a that is in contact with the contact area 13 of the first rocker arm 11. The valve head 14 has two arms that transition into the side sections 14b and 14c, respectively. Each side section has contact surfaces that transmit movements to one of the valves 3. The valve head 14 has a guide pin 14d that is mounted in a guide groove (not shown). The valves 3 are actuated by means of the guide pin when the first rocker arm 11 pushes the valve head 14 downwards. The first cam tappet 7, the first roller 8, the first pushrod 9, the first joint 10, the first rocker arm 11, and the valve head 14 are components of a first motion transmission mechanism that serves to transmit control movements from the first control surface 6 to the valves 3.
[0022] The camshaft 5 also has a peripheral second control surface 6a and a second cam tappet 7a. The second cam tappet 7a has a contact element in the form of a second rolling element 8a, which rolls in contact with the second control surface 6a. A second pushrod 9a, mounted essentially vertically, is pivotally connected to the second cam tappet 7a at its lower end. The second pushrod 9a is connected at its upper end to a second joint element 10a, which is fixedly mounted to the second rocker arm 11a. The second joint element 10a has a spherical section that is pivotally arranged in a spherical socket of the second pushrod 9a. The second rocker arm 11a is pivotally mounted in a central section about a second joint 12a.The second rocker arm 11a has a contact area 13a at a second end on the opposite side from joint 12a, which can come into contact with one of the side sections 14b of the valve head 14. The second cam tappet 7a, the second roller 8a, the second pushrod 9a, the second joint 10a, the second rocker arm 11a and the valve head 14 are components of a second motion transmission mechanism, which serves to transmit control movements from the second control surface 6a to the valves 3.
[0023] The second motion transmission mechanism, however, has a clearance 15. In this case, the clearance 15 is located between the contact area 13a of the rocker arm and the side section 14b of the valve head 14. The clearance 15 is dimensioned such that the control movements received by the second rocker arm 11a during operation cannot be transmitted from the contact area 13a of the second rocker arm 11a to the valve head 14. A connecting element in the form of a hydraulic piston 16 is arranged at the second end of the second rocker arm 11a. When the hydraulic piston 16 is activated, it is pushed outwards, so that the contact area 13a is moved from an inactive position, in which it is not in contact with the side section 14b of the valve head 14, to an active position, in which the contact area 13a is in contact with the side section 14b of the valve head 14.When the contact area 13a is in the active position, the hydraulic piston 16 bridges the gap 15 and the movements of the second rocker arm 11a can be transmitted to the valve head 14. A control unit 17 serves to control the activation of the hydraulic piston 16 using information 18 relating to one or more parameters connected with the operation of the internal combustion engine. The control unit 17 can receive information regarding the load and speed of the internal combustion engine.
[0024] The second motion transmission mechanism can alternatively have play at another point within the second motion transmission mechanism. Such play 15a can be created between the first end of the second rocker arm 11a and the second joint 10a. The joint 10a can be arranged so that it can be moved between two positions in the second rocker arm 11a by means of a hydraulic piston 16a. Another alternative play 15b can be created between the second cam tappet 7a and the second roller 8a. The roller 8a can be rotatably arranged on a shaft that is attached to the second cam tappet 7a in such a way that it can be moved between two positions by means of a hydraulic piston 16b. Connecting elements other than hydraulic pistons 16a can be used to bridge the play 15.
[0025] Fig. Figure 4 shows a curve 19, represented as a continuous line, which indicates the movement d that the valves 3 execute with the aid of the first control surface 6 and the first motion transmission mechanism during operation of the internal combustion engine. The valves 3 can be intake valves or exhaust valves. In this case, the valve actuation travel d begins when the angular position v of the camshaft is approximately -50°. The control surface 6 initially has a shape that causes the valve actuation travel d to increase successively from this angular position until the angular position v of the camshaft 5 is approximately 0°. When the camshaft 5 is in this angular position v, the actuation travel d of the valves 3 is at its maximum. The control surface 6 then has a shape that causes the actuation travel d of the valves 3 to decrease successively.When the angular position v of the camshaft 5 is approximately 50°, the actuation movement ends and the valves 3 close. Fig. Figure 4 shows a dashed curve 20, which indicates the valve movement d to which the second control surface 6a can move the valves 3 at different camshaft angles v. The curve begins when the angular position v of the camshaft is approximately -25°. The second control surface 6a has a shape that causes the valve actuation travel d to increase from this angular position until the angular position v of the camshaft 5 is approximately 25°. When the camshaft 5 is in this angular position v, the second control surface can effect a maximum actuation travel d of the valves 3. The second control surface 6a then has a shape that causes the actuation travel d of the valves 3 to decrease successively. When the angular position v of the camshaft 5 is approximately 75°, the actuation travel ends and the valves 3 close.In this case, the valves 3 will therefore close at a later time than if the valves 3 were controlled by the first motion transmission mechanism. This can be advantageous if the valves 3 are inlet valves.
[0026] During operation of the internal combustion engine, the control unit 17 receives information 18 about the load and speed of the internal combustion engine. Based on this information, the control unit 17 decides whether the valves 3 should close at the normal time or at a later time. If the control unit 17 decides that the valves 3 should close at the normal time, the hydraulic piston 16 is moved into a first position. The gap 15 in the second motion transmission mechanism prevents the movements of the second rocker arm 11a from being transmitted to the valve head 14. In this case, the actuation movement d of the valves 3 is therefore effected exclusively by the first control surface 6 and the first motion transmission mechanism. The valve actuation movement d thus begins when the camshaft 5 has an angular position v of -50° and ends when the camshaft 5 has an angular position v of 50°.
[0027] When the control unit 17 receives information 18 indicating that it is expedient to close the valves 3 at a later time, the hydraulic piston 16 is activated. The hydraulic piston 16 moves the contact area 13a so that it comes into contact with the side section 14b of the valve head 14, thus bridging the clearance 15. Both the first rocker arm 11 and the second rocker arm 11a are now in contact with the valve head 14. The downward displacement movement of the valve head 14 and the actuation movement of the valves 3 are controlled in this case by the control surface 6 / 6a and by the rocker arm 11 / 11a that gives the valves 3 the greatest actuation travel d. The rocker arm 11 / 11a that gives the valves 3 the least actuation travel d temporarily loses contact with the valve head 14. In this case, valve actuation d begins when the angular position of the camshaft is approximately -50°.The control surface 6 of the first motion transmission mechanism controls the actuating movement according to curve 19 in . Fig. 4. The first control surface 6 controls the actuating movement until the angular position v of the camshaft is approximately 50°. At this angular position, the second control surface 6a takes over the actuating of the valves 3 via the second motion transmission mechanism. The second control surface 6a then takes over the remaining part of the valve actuating d. When the angular position v of the camshaft 5 is approximately 75°, the actuating movement ends and the valves 3 are closed. In this case, the valves 3 are therefore closed at a later time than in normal operation.
[0028] Fig. Figure 4 also shows a dotted curve 21, which indicates the valve actuation travel d that the valves 3 receive with an alternative second control surface 6a. In this case, the valve actuation d begins when the angular position of the camshaft is approximately -75°. The second control surface 6a has a shape that causes the valve actuation travel d to increase from this angular position until the angular position v of the camshaft 5 is approximately -25°. When the camshaft 5 is in this angular position v, the valves 3 have a maximum actuation travel d. The second control surface 6a then has a shape that causes the actuation travel d of the valves 3 to decrease successively. When the angular position v of the camshaft 5 is approximately 25°, the actuation movement is complete and the valves 3 are closed.In this case, the valves 3 will therefore open at an earlier time than if the valves 3 were controlled by the first motion transmission mechanism. This can be advantageous if the valves 3 are exhaust or flue gas valves.
[0029] When the control unit 17 receives information 18 indicating that it is advantageous to open the valves 3 at an earlier time, the hydraulic piston 16 is activated. The hydraulic piston 16 moves the contact area 13a so that it comes into contact with the side portion 14b of the valve head, thus bridging the clearance 15. The downward displacement movement of the valve head 14 and the actuation movement d of the valves 3 are now controlled by the control surface 6, 6a, which gives the valves 3 the longest actuation stroke d. In this case, the valve actuation d begins when the angular position of the camshaft is approximately -75°. The alternative second control surface 6 controls the actuation movement of the valves 3 according to the curve 21 in Fig. 4. The alternative second control surface 6 controls the actuating movement of the valves until the angular position v of the camshaft is approximately -25°. At this angular position, the first control surface 6 takes over the actuating movement for the remaining part of the actuating travel d. When the angular position v of the camshaft 5 is approximately 50°, the actuating movement ends and the valves 3 close. In this case, the valves 3 therefore open at an earlier time than in normal operation.
[0030] Fig.Figure 5 shows another embodiment of the valve actuation device, used solely for illustrative purposes. In this case, the first rocker arm 11a has an element 22 dimensioned such that a portion of the element 22 is located below the second rocker arm 11a with a clearance 15. A hydraulic piston 16 is arranged in the second rocker arm 11a. When the control unit 17 receives information 18 indicating that normal valve opening is advantageous, the first motion transmission mechanism transmits control movements from the first control surface 6 to the valves 3. If the control unit 17 receives information 18 indicating that later closure of the valves 3 is advantageous, the hydraulic piston 16 is activated, shifting the contact area 13a so that it comes into contact with the element 22.The clearance 15 is bridged and the valves receive control movements from the control surface 6, 6a, which at the current angular position v of the camshaft 5 gives the valves 3 the longest actuation path d.
[0031] The invention is in no way limited to the embodiments described in the drawings, but can be freely varied within the scope of the patent claims.
Claims
[1] Valve actuation device for an internal combustion engine, comprising: a rotatable camshaft (5), a first control surface (6) on the camshaft (5), a first motion transmission mechanism (7, 8, 9, 10, 11, 14) for transmitting control movements from the first control surface (6) to actuate two valves (3) of the internal combustion engine, a second control surface (6a) on the camshaft (5), and a second motion transmission mechanism (7a, 8a, 9a, 10a, 11a, 14) for transmitting control movements from the second control surface (6a) to actuate the valves (3) of the internal combustion engine, wherein the valve actuation device comprises a linkage mechanism (15, 16) that is displaceable into a first position in which it prevents control movements from the second control surface (6a) from being transmitted to the valves from the first control surface (6a). (3) affect transferred control movements,and is displaceable into a second position in which it allows the control surface (6, 6a), which gives the valves (3) the longest actuation travel (d) at the current angular position (v) of the camshaft (5), to be used for actuating the valves (3), wherein the first motion transmission mechanism (7, 8, 9, 10, 11, 14) and the second motion transmission mechanism (7a, 8a, 9a, 10a, 11a, 14) have a common valve head (14) on the valves (3), wherein the first motion transmission mechanism (7, 8, 9, 10, 11, 14) has a first rocker arm (11) that is connectable to the valve head (14), and wherein the second motion transmission mechanism (7a, 8a, 9a, 10a, 11a, 14) has a second rocker arm (11a) that is connectable to the The valve head (14) is connectable, has a clearance (15) and a movable connecting element (16) which maintains the clearance (15) in the first position, which is dimensioned such thatthat control movements from the second control surface (6a) cannot be transmitted beyond the play (15), and in the second position the play (15) is bridged, so that control movements from the second control surface (6a) can be transmitted beyond the play (15). [2] Valve actuation device according to claim 1, characterized by , that the connecting element (16) has a retractable piston (16). [3] Valve actuation device according to claim 1, characterized by , that the play (15) of the second motion transmission mechanism (7a, 8a, 9a, 10a, 11a, 14) is located between the second rocker arm (11a) and the valve head (14). [4] Valve actuation device according to one of the preceding claims, characterized by, that the valve actuation device has a control unit (17) which moves the linking mechanism (15, 16) into the first position or into the second position on the basis of information (18) relating to at least one operating parameter of the internal combustion engine. [5] Valve actuation device according to one of the preceding claims, characterized by , that the second control surface (6a) is designed in relation to the first control surface (6) such that the valve (3) closes at a later time when the connecting mechanism (15, 16) is in the second position. [6] Valve actuation device according to one of the preceding claims, characterized by , that the second control surface (6a) is designed in relation to the first control surface (6) such that the valve (3) opens at an earlier time when the connecting mechanism (15, 16) is in the second position.