CA2560983A1 - Force transmission device with a hydraulic valve-clearance compensation device - Google Patents
Force transmission device with a hydraulic valve-clearance compensation device Download PDFInfo
- Publication number
- CA2560983A1 CA2560983A1 CA002560983A CA2560983A CA2560983A1 CA 2560983 A1 CA2560983 A1 CA 2560983A1 CA 002560983 A CA002560983 A CA 002560983A CA 2560983 A CA2560983 A CA 2560983A CA 2560983 A1 CA2560983 A1 CA 2560983A1
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- Canada
- Prior art keywords
- hydraulic medium
- valve
- force transmission
- transmission device
- face
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/12—Transmitting gear between valve drive and valve
- F01L1/14—Tappets; Push rods
- F01L1/143—Tappets; Push rods for use with overhead camshafts
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/20—Adjusting or compensating clearance
- F01L1/22—Adjusting or compensating clearance automatically, e.g. mechanically
- F01L1/24—Adjusting or compensating clearance automatically, e.g. mechanically by fluid means, e.g. hydraulically
- F01L1/245—Hydraulic tappets
- F01L1/25—Hydraulic tappets between cam and valve stem
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
- F01L13/0015—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque
- F01L13/0036—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque the valves being driven by two or more cams with different shape, size or timing or a single cam profiled in axial and radial direction
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L2307/00—Preventing the rotation of tappets
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Valve-Gear Or Valve Arrangements (AREA)
- Valve Device For Special Equipments (AREA)
Abstract
A force transmission device (2) with a hydraulic valve-clearance compensation device (17) for a valve drive of an internal combustion engine is proposed. The force transmission device (2) is guided longitudinally movably in a guide (5) inclined with respect to gravity (4) and has a bottom (11) which is secured against rotation about the longitudinal axis of the guide (5) and which, on an inside (23), supports over a large area a plane end face (22) of a compensating piston (18) of the valve-clearance compensation device (17) and on the inside (23) has a hydraulic medium overflow (29) which connects a hydraulic medium prespace (26) to a hydraulic medium reservoir (20) which runs within the compensating piston (18) and which serves for supplying a working space (19) of the valve-clearance compensation device (17). In this case, the hydraulic medium overflow (29) is always to run opposite the geodetically highest point of the end face (22) of the compensating piston (18), the end face (22) and the inside (23) of the bottom (11) cooperating in a hydraulically sealing manner outside the hydraulic medium overflow (29).
Description
Designation of the invention Force transmission device with a hydraulic valve-clearance compensation device Description Field of the invention The invention relates to a force transmission device with a hydraulic valve-clearance compensation device for a valve drive of an internal combustion engine. The force transmission device is guided longitudinally movably on an outer surface area in an internal combustion engine guide inclined with respect to gravity and on one end face has a bottom which is secured against rotation about the longitudinal axis of the guide and which, on an inside, supports over a large area a plane end face of a compensating piston of the valve-clearance compensation device and on the inside has a hydraulic medium overflow which connects a hydraulic medium prespace, connected to a hydraulic medium supply of the internal combustion engine, to a hydraulic medium reservoir which runs within the compensating piston and which serves for supplying a working space of the valve-clearance compensation device.
Background of the invention The functional readiness or functioning capacity, required in all operating states, including standstill and starting, of the internal combustion engine, of a hydraulic valve-clearance compensation device depends essentially on the properties of the hydraulic medium reservoir which has to supply sufficient hydraulic medium to the working space expanding during compensating movements of the valve-clearance compensation device. A particularly critical operating state in this regard is an operation to start a cold internal combustion engine which, as a rule, has been stopped by means of one or more opened gas-exchange valves, so that, under the action of the force of the gas-exchange valve spring, and depending on the duration of the intermediate standstill phase of the internal combustion engine, the compensating pistons of the associated valve-clearance compensation devices have partially or completely fallen out of the working space, at the same time largely displacing the hydraulic medium. Since, during the starting operation, the hydraulic medium pump also does not convey any or a sufficient hydraulic medium volume flow to the compensating pistons, essentially the sole task of the hydraulic medium reservoir is to cover fully the considerable requirement for hydraulic medium of the working space during its expansion out of the lowered position of the compensating piston into its working position. An insufficiently large or an insufficiently filled hydraulic medium reservoir would necessarily lead to a suction-intake of air bubbles or gas bubbles into the working space. The consequences of a working space containing air bubbles or gas bubbles for the functioning of the valve drive during the starting and operation of the internal combustion engine are known to a person skilled in the art and in acoustic terms are perceived disturbingly as what is known as valve-drive clattering, above all as a result of high set-down speeds of the gas-exchange valve during its closing action.
A satisfactorily functioning hydraulic valve-clearance compensation device therefore presupposes both a sufficiently large and a sufficiently filled hydraulic medium reservoir. It has proved expedient in the dimensioning of the hydraulic medium reservoir to have a directional quantity according to which the volume of the hydraulic medium reservoir is to amount to a multiple of the volume of the working space, in order reliably to rule out the undesirable suction-intake of air bubbles or gas bubbles into the working space under all the operating conditions of the internal combustion engine. On the other hand, however, this directional quantity may be increasingly in conflict with the aim of further reducing the construction space and/or the mass of the force transmission device or of extending the functionality of the latter if the construction space remains unchanged. The latter instance includes, in particular, force transmission devices which are designed as reversible bucket tappets and which, depending on the switching state of their coupling means, can transmit strokes of different cams selectively to the gas-exchange valve and/or can completely cut out the stroke of a cam. For this purpose, tappet parts longitudinally displaceable with respect to one another and couplable to one another are nested one in the other such that the external and connection geometry of the bucket tappet can remain essentially unchanged. This may lead, however, to a reduction in the construction space of the hydraulic valve-clearance compensation device and consequently to a reduction in volume of the hydraulic medium reservoir enclosed by the compensating piston, along with the risk explained above and the consequences of a deficient supply of hydraulic medium to the working space.
Of course, a sufficiently filled hydraulic medium reservoir presupposes that the hydraulic medium reservoir is sufficiently protected against a loss of hydraulic medium due to leakage. It is difficult for this requirement to be fulfilled particularly when the force transmission device is installed in the internal combustion engine at an inclination with respect to gravity, and a usually large part of the hydraulic medium located in the hydraulic medium reservoir can flow out into the hydraulic medium prespace.
A force transmission device of this type, designed as a bucket tappet, is known from DE 196 03 915 A1 which is considered as forming the precharacterizing clause. The bucket tappet is installed, secured against rotation, in an internal combustion engine guide inclined with respect to gravity, and the hydraulic medium overflow between the hydraulic medium reservoir delimited by the compensating piston and the hydraulic medium prespace runs in relation to the geodetically lowest point of the end face of the compensating piston. To that extent, with the internal combustion engine at a standstill and with a pressureless supply of hydraulic medium, a leakage of hydraulic medium out of the hydraulic medium reservoir into the hydraulic medium prespace can be prevented only when the filling level of the hydraulic medium in the hydraulic medium prespace is at least at the level of the hydraulic medium overflow. The precondition for this is, again, a supply bore which runs well up in the housing of the bucket tappet and connects the hydraulic medium supply to the hydraulic medium prespace and the position of which prevents the hydraulic medium prespace from running empty. However, in order in this case to avoid a pressure loss within the hydraulic medium supply as a result of a free outflow of hydraulic medium from the hydraulic medium supply into the guide in the event of a deficient overlap by the longitudinally moved bucket tappet, the publication mentioned proposes a ring segment emanating from the bucket bottom. This ring segment is intended to block the supply of hydraulic medium even in the case of a maximum stroke of the bucket tappet. However, it is evident to a person skilled in the art that such a ring segment entails a considerable outlay in manufacturing terms, along with correspondingly high production costs, and, furthermore, also causes an undesirable increase in weight of the bucket tappet. Moreover, such a solution would presuppose shifting the hydraulic medium gallery, running mostly at great depth in the guide, to a higher position matching the supply bore. This, however, cannot be combined with an internal combustion engine architecture which, as a rule, is invariable or at most is only slightly variable.
Furthermore, DE 3500425 A1 proposes a bucket tappet provided with leakage protection of the hydraulic medium reservoir, in a guide likewise inclined with respect to gravity, although this bucket tappet is not secured against rotation in the guide. Leakage protection is based on a diametral arrangement of the supply duct, issuing in the hydraulic medium prespace, with respect to the hydraulic medium overflow to the hydraulic medium reservoir and is fully effective both in the position of the bucket tappet, in which the hydraulic medium overflow is located at the geodetically highest point and the issue of the supply duct is located at the geodetically lowest point, and, conversely, in the position in which the hydraulic medium overflow is located at the geodetically lowest point and the issue of the supply duct is located at the geodetically highest point. In the first instance, a leakage of hydraulic medium out of the hydraulic medium reservoir is prevented by the highest-lying hydraulic medium overflow itself, whilst, in the second instance, the hydraulic medium prespace, as far as possible filled completely, prevents a leakage of hydraulic medium out of the hydraulic medium reservoir.
However, in all other intermediate positions outside these two limit positions of the bucket tappet, a leakage of hydraulic medium out of the hydraulic medium reservoir cannot be avoided, since, then, either the hydraulic medium overflow or the issue of the supply duct is removed from its geodetically optimal position in terms of leakage protection.
Object of the invention The object of the invention is, therefore, to configure a force transmission device of the type mentioned in the introduction, such that the disadvantages mentioned are eliminated by simple means. Accordingly, a sufficiently large hydraulic medium reservoir as far as possible protected completely against leakage is made available at all times to the working space of the valve-clearance compensation device, in order, in particular, to ensure a starting phase and warm-up phase of the internal combustion engine which are free of valve-drive clattering.
Summary of the invention This object is achieved by means of the characterizing features of the first claim, whilst advantageous developments and refinements may be gathered from the subclaims. According to the invention, therefore, the hydraulic medium overflow is always to run opposite the geodetically highest point of the end face of the compensating piston, the end face and the inside of the bottom cooperating in a hydraulically sealing manner outside the hydraulic medium overflow.
Owing to this positioning of the hydraulic medium overflow, the greatest possible filling level of the hydraulic medium reservoir is ensured, even when the force transmission device is installed in the internal _ 7 combustion engine at an inclination with respect to gravity, so that a sufficiently large hydraulic medium volume preventing the suction-intake of air bubbles or gas bubbles can always be made available to the working space. Furthermore, with the internal combustion engine at a standstill, the filling level of the hydraulic medium reservoir is Largely independent of the filling level of the hydraulic medium prespace, so that the functional readiness of the valve-clearance compensation device is not impaired, even when the hydraulic medium prespace is emptied completely into the hydraulic medium supply or the guide.
Whilst the force transmission device thus designed can 25 be acted upon with force in the longitudinal direction by any desired valve-drive members, in a preferred refinement of the invention the force transmission device is to be designed as a bucket tappet, an outside of the bottom serving as a cam contact face. Moreover, the latter may be designed in the form of a segment of a cylinder, as seen in the cam rotation direction. As compared with a plane bucket bottom, a cam contact face configured in this way allows a considerable reduction in diameter of the bucket tappet, since the pressure angles corresponding to the cam travel and determining the tappet diameter are considerably smaller, if the stroke profile of the bucket tappet is identical, than in the case of the plane bucket bottom.
Finally, the bucket tappet may be designed reversibly for the transmission of different cam strokes. In this case, the outer surface area belongs to an outer part, in which an inner part receiving the valve-clearance compensation device is mounted longitudinally displaceably counter to the force of a lost-motion spring tensioned between the outer part and the inner part and can be connected positively in the transmission direction to the outer part by means of a _ g _ locking mechanism. Such a bucket tappet is basically known, for example, from DE 44 92 633 C1, and, for reasons of construction space and of functioning, it is always advantageous to reduce further both the diameter of the inner part and the height of the valve-clearance compensation device. The reduction in volume of the hydraulic medium reservoir which necessarily accompanies this can be combined particularly advantageously with the positioning according to the invention of the hydraulic medium overflow, so that a hydraulic medium volume which, as before, is sufficient can be made available to the working space, even when the bucket tappet is installed at an inclination with respect to gravity.
Brief description of the drawing Further features of the invention may be gathered from the following description and from the drawing in which the force transmission device according to the invention is illustrated in longitudinal section by the example of a switchable bucket tappet installed in a guide of the internal combustion engine.
Detailed description of the drawing The single Figure 1 shows a force transmission device 2, designed as a bucket tappet 1, for a valve drive of an internal combustion engine. The bucket tappet 1 is guided longitudinally movably on an outer surface area 3 in a guide 5 inclined with respect to gravity 4 and is designed reversibly for transmitting different cam strokes of a camshaft, not illustrated, to a gas-exchange valve, likewise not illustrated, as a function of the operating point. For this purpose, in an outer part 6, an inner part 7 is mounted longitudinally displaceably counter to the force of a lost-motion spring 8 tensioned between the outer part 6 _ g _ and the inner part 7 and can be connected positively in the transmission direction to the outer part 6 by means of a locking mechanism 9. Both a bottom 11 of the inner part 7, the said bottom running on an end face 10 of the bucket tappet 1, and a bottom 12 of the outer part 6 have outsides 13 and 14 which are designed in the form of a segment of a cylinder and which serve as cam contact faces 15 and 16. In addition to the hydraulic supply, explained later, it is necessary, if only because of the cam contact faces 15, 26 designed in this way, to secure the bucket tappet 1 against rotation about its longitudinal axis. Although this measure is not evident in the longitudinal section illustrated, an anti-rotation needle known in the prior art may be provided for this purpose, which projects radially beyond the outer surface area 3 of the bucket tappet 1 and runs in a complementary longitudinal groove of the guide 5.
The inner part 7 of the bucket tappet 1 serves for receiving a hydraulic valve-clearance compensation device 27 comprising a working space 19 which is delimited by a hollow-cylindrical compensating piston l8 and which is supplied with hydraulic medium, via a non-return valve 21, by a hydraulic medium reservoir 20 running within the compensating piston 18. The compensating piston 18 has an annular and plane end face 22 which is supported over a large area on an inside 23 of the bottom 11 of the inner part 7. The valve-clearance compensation device 17 is tied to a hydraulic medium supply of the internal combustion engine by means of a hydraulic gallery 24 intersecting the guide 5. The hydraulic medium passes from here, via a supply bore 25 running in the outer surface area 3 , first into a hydraulic medium prespace 26 which, on the one hand, is delimited by the bottom 12 of the outer part 6 and by a spring support plate 27 and, on the other hand, also comprises, in the inner part 7, an annular space 28 surrounding the compensating piston 18. Finally, the hydraulic tie-up of the hydraulic medium reservoir 20 to the hydraulic medium prespace 26 takes place via a hydraulic medium overflow 29 which runs on the inside 23 of the bottom 11 and which is designed as a circular bead. In this case, the hydraulic medium overflow 29 is always located opposite the geodetically highest point of the end face 22 of the compensating piston 18, since the inner part 7, too, is secured against rotation about its longitudinal axis with respect to the outer part 6 by known means not illustrated in any more detail here. The end face 22 of the compensating piston 18 and the inside 23 of the bottom 11 cooperate in a hydraulically sealing manner outside the hydraulic medium overflow 29, so that, during the standstill phase of the internal combustion engine, the hydraulic medium reservoir 20 is largely protected against leakage into the hydraulic medium prespace 26. In this case, ideally, it always has the greatest possible filling level 30, illustrated symbolically.
The activation of the locking mechanism 9 takes place separately with respect to the hydraulic supply of the valve-clearance compensation device 17 by means of pressure-modulated hydraulic medium from a second hydraulic gallery 31. This is connected, via a further supply bore 32 in the outer surface area 3 of the outer part 6, to a hydraulic chamber 33 which is separated from the hydraulic medium prespace 26 and from which the hydraulic medium arrives at the locking mechanism 9. On account of this two-flow hydraulic supply, too, securing of the bucket tappet 1 against rotation about its longitudinal axis is required.
List of reference numerals 1 Bucket tappet 2 Force transmission device 3 Outer surface area 4 Gravity Guide 6 Outer part 7 Inner part 8 Lost-motion spring 9 Locking mechanism End face 11 Bottom 12 Bottom 13 Outside 14 Outside Cam contact face 16 Cam contact face 17 Valve-clearance compensation device 18 Compensating piston 19 Working space Hydraulic medium reservoir 21 Non-return valve 22 End face 23 Inside 24 Hydraulic gallery Supply bore 26 Hydraulic medium prespace 27 Spring support plate 28 Annular space 29 Hydraulic medium overflow Filling level 31 Hydraulic gallery 32 Supply bore 33 Hydraulic chamber
Background of the invention The functional readiness or functioning capacity, required in all operating states, including standstill and starting, of the internal combustion engine, of a hydraulic valve-clearance compensation device depends essentially on the properties of the hydraulic medium reservoir which has to supply sufficient hydraulic medium to the working space expanding during compensating movements of the valve-clearance compensation device. A particularly critical operating state in this regard is an operation to start a cold internal combustion engine which, as a rule, has been stopped by means of one or more opened gas-exchange valves, so that, under the action of the force of the gas-exchange valve spring, and depending on the duration of the intermediate standstill phase of the internal combustion engine, the compensating pistons of the associated valve-clearance compensation devices have partially or completely fallen out of the working space, at the same time largely displacing the hydraulic medium. Since, during the starting operation, the hydraulic medium pump also does not convey any or a sufficient hydraulic medium volume flow to the compensating pistons, essentially the sole task of the hydraulic medium reservoir is to cover fully the considerable requirement for hydraulic medium of the working space during its expansion out of the lowered position of the compensating piston into its working position. An insufficiently large or an insufficiently filled hydraulic medium reservoir would necessarily lead to a suction-intake of air bubbles or gas bubbles into the working space. The consequences of a working space containing air bubbles or gas bubbles for the functioning of the valve drive during the starting and operation of the internal combustion engine are known to a person skilled in the art and in acoustic terms are perceived disturbingly as what is known as valve-drive clattering, above all as a result of high set-down speeds of the gas-exchange valve during its closing action.
A satisfactorily functioning hydraulic valve-clearance compensation device therefore presupposes both a sufficiently large and a sufficiently filled hydraulic medium reservoir. It has proved expedient in the dimensioning of the hydraulic medium reservoir to have a directional quantity according to which the volume of the hydraulic medium reservoir is to amount to a multiple of the volume of the working space, in order reliably to rule out the undesirable suction-intake of air bubbles or gas bubbles into the working space under all the operating conditions of the internal combustion engine. On the other hand, however, this directional quantity may be increasingly in conflict with the aim of further reducing the construction space and/or the mass of the force transmission device or of extending the functionality of the latter if the construction space remains unchanged. The latter instance includes, in particular, force transmission devices which are designed as reversible bucket tappets and which, depending on the switching state of their coupling means, can transmit strokes of different cams selectively to the gas-exchange valve and/or can completely cut out the stroke of a cam. For this purpose, tappet parts longitudinally displaceable with respect to one another and couplable to one another are nested one in the other such that the external and connection geometry of the bucket tappet can remain essentially unchanged. This may lead, however, to a reduction in the construction space of the hydraulic valve-clearance compensation device and consequently to a reduction in volume of the hydraulic medium reservoir enclosed by the compensating piston, along with the risk explained above and the consequences of a deficient supply of hydraulic medium to the working space.
Of course, a sufficiently filled hydraulic medium reservoir presupposes that the hydraulic medium reservoir is sufficiently protected against a loss of hydraulic medium due to leakage. It is difficult for this requirement to be fulfilled particularly when the force transmission device is installed in the internal combustion engine at an inclination with respect to gravity, and a usually large part of the hydraulic medium located in the hydraulic medium reservoir can flow out into the hydraulic medium prespace.
A force transmission device of this type, designed as a bucket tappet, is known from DE 196 03 915 A1 which is considered as forming the precharacterizing clause. The bucket tappet is installed, secured against rotation, in an internal combustion engine guide inclined with respect to gravity, and the hydraulic medium overflow between the hydraulic medium reservoir delimited by the compensating piston and the hydraulic medium prespace runs in relation to the geodetically lowest point of the end face of the compensating piston. To that extent, with the internal combustion engine at a standstill and with a pressureless supply of hydraulic medium, a leakage of hydraulic medium out of the hydraulic medium reservoir into the hydraulic medium prespace can be prevented only when the filling level of the hydraulic medium in the hydraulic medium prespace is at least at the level of the hydraulic medium overflow. The precondition for this is, again, a supply bore which runs well up in the housing of the bucket tappet and connects the hydraulic medium supply to the hydraulic medium prespace and the position of which prevents the hydraulic medium prespace from running empty. However, in order in this case to avoid a pressure loss within the hydraulic medium supply as a result of a free outflow of hydraulic medium from the hydraulic medium supply into the guide in the event of a deficient overlap by the longitudinally moved bucket tappet, the publication mentioned proposes a ring segment emanating from the bucket bottom. This ring segment is intended to block the supply of hydraulic medium even in the case of a maximum stroke of the bucket tappet. However, it is evident to a person skilled in the art that such a ring segment entails a considerable outlay in manufacturing terms, along with correspondingly high production costs, and, furthermore, also causes an undesirable increase in weight of the bucket tappet. Moreover, such a solution would presuppose shifting the hydraulic medium gallery, running mostly at great depth in the guide, to a higher position matching the supply bore. This, however, cannot be combined with an internal combustion engine architecture which, as a rule, is invariable or at most is only slightly variable.
Furthermore, DE 3500425 A1 proposes a bucket tappet provided with leakage protection of the hydraulic medium reservoir, in a guide likewise inclined with respect to gravity, although this bucket tappet is not secured against rotation in the guide. Leakage protection is based on a diametral arrangement of the supply duct, issuing in the hydraulic medium prespace, with respect to the hydraulic medium overflow to the hydraulic medium reservoir and is fully effective both in the position of the bucket tappet, in which the hydraulic medium overflow is located at the geodetically highest point and the issue of the supply duct is located at the geodetically lowest point, and, conversely, in the position in which the hydraulic medium overflow is located at the geodetically lowest point and the issue of the supply duct is located at the geodetically highest point. In the first instance, a leakage of hydraulic medium out of the hydraulic medium reservoir is prevented by the highest-lying hydraulic medium overflow itself, whilst, in the second instance, the hydraulic medium prespace, as far as possible filled completely, prevents a leakage of hydraulic medium out of the hydraulic medium reservoir.
However, in all other intermediate positions outside these two limit positions of the bucket tappet, a leakage of hydraulic medium out of the hydraulic medium reservoir cannot be avoided, since, then, either the hydraulic medium overflow or the issue of the supply duct is removed from its geodetically optimal position in terms of leakage protection.
Object of the invention The object of the invention is, therefore, to configure a force transmission device of the type mentioned in the introduction, such that the disadvantages mentioned are eliminated by simple means. Accordingly, a sufficiently large hydraulic medium reservoir as far as possible protected completely against leakage is made available at all times to the working space of the valve-clearance compensation device, in order, in particular, to ensure a starting phase and warm-up phase of the internal combustion engine which are free of valve-drive clattering.
Summary of the invention This object is achieved by means of the characterizing features of the first claim, whilst advantageous developments and refinements may be gathered from the subclaims. According to the invention, therefore, the hydraulic medium overflow is always to run opposite the geodetically highest point of the end face of the compensating piston, the end face and the inside of the bottom cooperating in a hydraulically sealing manner outside the hydraulic medium overflow.
Owing to this positioning of the hydraulic medium overflow, the greatest possible filling level of the hydraulic medium reservoir is ensured, even when the force transmission device is installed in the internal _ 7 combustion engine at an inclination with respect to gravity, so that a sufficiently large hydraulic medium volume preventing the suction-intake of air bubbles or gas bubbles can always be made available to the working space. Furthermore, with the internal combustion engine at a standstill, the filling level of the hydraulic medium reservoir is Largely independent of the filling level of the hydraulic medium prespace, so that the functional readiness of the valve-clearance compensation device is not impaired, even when the hydraulic medium prespace is emptied completely into the hydraulic medium supply or the guide.
Whilst the force transmission device thus designed can 25 be acted upon with force in the longitudinal direction by any desired valve-drive members, in a preferred refinement of the invention the force transmission device is to be designed as a bucket tappet, an outside of the bottom serving as a cam contact face. Moreover, the latter may be designed in the form of a segment of a cylinder, as seen in the cam rotation direction. As compared with a plane bucket bottom, a cam contact face configured in this way allows a considerable reduction in diameter of the bucket tappet, since the pressure angles corresponding to the cam travel and determining the tappet diameter are considerably smaller, if the stroke profile of the bucket tappet is identical, than in the case of the plane bucket bottom.
Finally, the bucket tappet may be designed reversibly for the transmission of different cam strokes. In this case, the outer surface area belongs to an outer part, in which an inner part receiving the valve-clearance compensation device is mounted longitudinally displaceably counter to the force of a lost-motion spring tensioned between the outer part and the inner part and can be connected positively in the transmission direction to the outer part by means of a _ g _ locking mechanism. Such a bucket tappet is basically known, for example, from DE 44 92 633 C1, and, for reasons of construction space and of functioning, it is always advantageous to reduce further both the diameter of the inner part and the height of the valve-clearance compensation device. The reduction in volume of the hydraulic medium reservoir which necessarily accompanies this can be combined particularly advantageously with the positioning according to the invention of the hydraulic medium overflow, so that a hydraulic medium volume which, as before, is sufficient can be made available to the working space, even when the bucket tappet is installed at an inclination with respect to gravity.
Brief description of the drawing Further features of the invention may be gathered from the following description and from the drawing in which the force transmission device according to the invention is illustrated in longitudinal section by the example of a switchable bucket tappet installed in a guide of the internal combustion engine.
Detailed description of the drawing The single Figure 1 shows a force transmission device 2, designed as a bucket tappet 1, for a valve drive of an internal combustion engine. The bucket tappet 1 is guided longitudinally movably on an outer surface area 3 in a guide 5 inclined with respect to gravity 4 and is designed reversibly for transmitting different cam strokes of a camshaft, not illustrated, to a gas-exchange valve, likewise not illustrated, as a function of the operating point. For this purpose, in an outer part 6, an inner part 7 is mounted longitudinally displaceably counter to the force of a lost-motion spring 8 tensioned between the outer part 6 _ g _ and the inner part 7 and can be connected positively in the transmission direction to the outer part 6 by means of a locking mechanism 9. Both a bottom 11 of the inner part 7, the said bottom running on an end face 10 of the bucket tappet 1, and a bottom 12 of the outer part 6 have outsides 13 and 14 which are designed in the form of a segment of a cylinder and which serve as cam contact faces 15 and 16. In addition to the hydraulic supply, explained later, it is necessary, if only because of the cam contact faces 15, 26 designed in this way, to secure the bucket tappet 1 against rotation about its longitudinal axis. Although this measure is not evident in the longitudinal section illustrated, an anti-rotation needle known in the prior art may be provided for this purpose, which projects radially beyond the outer surface area 3 of the bucket tappet 1 and runs in a complementary longitudinal groove of the guide 5.
The inner part 7 of the bucket tappet 1 serves for receiving a hydraulic valve-clearance compensation device 27 comprising a working space 19 which is delimited by a hollow-cylindrical compensating piston l8 and which is supplied with hydraulic medium, via a non-return valve 21, by a hydraulic medium reservoir 20 running within the compensating piston 18. The compensating piston 18 has an annular and plane end face 22 which is supported over a large area on an inside 23 of the bottom 11 of the inner part 7. The valve-clearance compensation device 17 is tied to a hydraulic medium supply of the internal combustion engine by means of a hydraulic gallery 24 intersecting the guide 5. The hydraulic medium passes from here, via a supply bore 25 running in the outer surface area 3 , first into a hydraulic medium prespace 26 which, on the one hand, is delimited by the bottom 12 of the outer part 6 and by a spring support plate 27 and, on the other hand, also comprises, in the inner part 7, an annular space 28 surrounding the compensating piston 18. Finally, the hydraulic tie-up of the hydraulic medium reservoir 20 to the hydraulic medium prespace 26 takes place via a hydraulic medium overflow 29 which runs on the inside 23 of the bottom 11 and which is designed as a circular bead. In this case, the hydraulic medium overflow 29 is always located opposite the geodetically highest point of the end face 22 of the compensating piston 18, since the inner part 7, too, is secured against rotation about its longitudinal axis with respect to the outer part 6 by known means not illustrated in any more detail here. The end face 22 of the compensating piston 18 and the inside 23 of the bottom 11 cooperate in a hydraulically sealing manner outside the hydraulic medium overflow 29, so that, during the standstill phase of the internal combustion engine, the hydraulic medium reservoir 20 is largely protected against leakage into the hydraulic medium prespace 26. In this case, ideally, it always has the greatest possible filling level 30, illustrated symbolically.
The activation of the locking mechanism 9 takes place separately with respect to the hydraulic supply of the valve-clearance compensation device 17 by means of pressure-modulated hydraulic medium from a second hydraulic gallery 31. This is connected, via a further supply bore 32 in the outer surface area 3 of the outer part 6, to a hydraulic chamber 33 which is separated from the hydraulic medium prespace 26 and from which the hydraulic medium arrives at the locking mechanism 9. On account of this two-flow hydraulic supply, too, securing of the bucket tappet 1 against rotation about its longitudinal axis is required.
List of reference numerals 1 Bucket tappet 2 Force transmission device 3 Outer surface area 4 Gravity Guide 6 Outer part 7 Inner part 8 Lost-motion spring 9 Locking mechanism End face 11 Bottom 12 Bottom 13 Outside 14 Outside Cam contact face 16 Cam contact face 17 Valve-clearance compensation device 18 Compensating piston 19 Working space Hydraulic medium reservoir 21 Non-return valve 22 End face 23 Inside 24 Hydraulic gallery Supply bore 26 Hydraulic medium prespace 27 Spring support plate 28 Annular space 29 Hydraulic medium overflow Filling level 31 Hydraulic gallery 32 Supply bore 33 Hydraulic chamber
Claims (4)
1. Force transmission device (2) with a hydraulic valve-clearance compensation device (17) for a valve drive of an internal combustion engine, which force transmission device (2) is guided longitudinally movably on an outer surface area (3) in an internal combustion engine guide (5) inclined with respect to gravity (4) and on one end face (10) has a bottom (11) which is secured against rotation about the longitudinal axis of the guide (5) and which, on an inside (23), supports over a large area a plane end face (22) of a compensating piston (18) of the valve-clearance compensation device (17) and on the inside (23) has a hydraulic medium overflow (29) which connects a hydraulic medium prespace (26), connected to a hydraulic medium supply of the internal combustion engine, to a hydraulic medium reservoir (20) which runs within the compensating piston (18) and which serves for supplying a working space (19) of the valve-clearance compensation device (17), characterized in that the hydraulic medium overflow (29) always runs opposite the geodetically highest point of the end face (22) of the compensating piston (18), the end face (22) and the inside (23) of the bottom (11) cooperating in a hydraulically sealing manner outside the hydraulic medium overflow (29).
2. Force transmission device according to Claim 1, characterized in that the force transmission device (2) is designed as a bucket tappet (1), an outside (13) of the bottom (11) serving as a cam contact face (15).
3. Force transmission device according to Claim 2, characterized in that the cam contact face (15) is designed in the form of a segment of a cylinder, as seen in the cam rotation direction.
4. Force transmission device according to Claim 2, characterized in that the bucket tappet (1) is designed reversibly for the transmission of different cam strokes, in that the outer surface area (3) belongs to an outer part (6), in which an inner part (7) receiving the valve-clearance compensation device (17) is mounted longitudinally displaceably counter to the force of a lost-motion spring (8) tensioned between the outer part (6) and the inner part (7) and can be connected positively in the transmission direction to the outer part (6) by means of a locking mechanism (9).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE102005046062A DE102005046062A1 (en) | 2005-09-27 | 2005-09-27 | Power transmission device with hydraulic valve clearance compensation device |
| DE102005046062.3 | 2005-09-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2560983A1 true CA2560983A1 (en) | 2007-03-27 |
Family
ID=37520285
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002560983A Abandoned CA2560983A1 (en) | 2005-09-27 | 2006-09-26 | Force transmission device with a hydraulic valve-clearance compensation device |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP1767748A3 (en) |
| JP (1) | JP2007092752A (en) |
| CA (1) | CA2560983A1 (en) |
| DE (1) | DE102005046062A1 (en) |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3500425A1 (en) * | 1985-01-09 | 1986-07-10 | Motomak Motorenbau, Maschinen- u. Werkzeugfabrik, Konstruktionen GmbH, 8070 Ingolstadt | HYDRAULIC CUPS FOR COMBUSTION ENGINES |
| DE4314619A1 (en) * | 1993-05-04 | 1994-11-10 | Schaeffler Waelzlager Kg | Pestle |
| DE19603915A1 (en) * | 1996-02-03 | 1997-08-07 | Schaeffler Waelzlager Kg | Tappet for a valve train of an internal combustion engine |
| DE19603916A1 (en) * | 1996-02-03 | 1997-08-07 | Schaeffler Waelzlager Kg | Tappet for the valve train of an internal combustion engine |
| DE19705726A1 (en) * | 1997-02-14 | 1998-08-20 | Schaeffler Waelzlager Ohg | Valve train of an internal combustion engine |
| DE10028100B4 (en) * | 2000-06-07 | 2006-07-27 | Dr.Ing.H.C. F. Porsche Ag | Plunger for actuating a valve of an internal combustion engine |
-
2005
- 2005-09-27 DE DE102005046062A patent/DE102005046062A1/en not_active Withdrawn
-
2006
- 2006-08-10 EP EP06118699A patent/EP1767748A3/en not_active Withdrawn
- 2006-09-21 JP JP2006255582A patent/JP2007092752A/en active Pending
- 2006-09-26 CA CA002560983A patent/CA2560983A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| EP1767748A3 (en) | 2010-01-20 |
| EP1767748A2 (en) | 2007-03-28 |
| DE102005046062A1 (en) | 2007-03-29 |
| JP2007092752A (en) | 2007-04-12 |
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