Patent Application
20120031358
This application claims the benefit of German patent application number DE 10 2010 033 296.8 filed on Aug. 4, 2010, which is incorporated herein by reference in its entirety and for all purposes.
The present invention relates to a valve train of an internal combustion engine with a double camshaft.
A rotary drive that is specifically made for an adjusting shaft of a variable valve train is known from EP 1 347 154 A2 (Applicant: Hydraulik-Ring GmbH; Priority date: Mar. 20, 2003). A first rotatory hydraulic drive is joined to a second rotatory hydraulic drive so that coarse and fine adjustments of an exact cam position within a valve train chain are possible. In other words, the rotary angle position to be adjusted is made possible by a two-stage system.
U.S. Pat. No. 2,911,956 (Applicant: Smith; Date filed: Jan. 7, 1959) describes a plate-type positioner, by means of which a pivoting movement of a first plate influences the pivoting range of a second plate, and so forth.
WO 01/12996 A1 (Applicant: Raikamo; Priority date: Aug. 17, 1999) shows in
One skilled in the art can derive from U.S. Pat. No. 5,233,948 (Applicant: Ford Motor Corporation; Date filed: Dec. 10, 1992) the advantages that can be found if the cams of superimposed camshafts can be adjusted relative to one another. Thus there has been the desire for several years to create valve trains that are configured so that they can individually control the events of several gas-exchange valves of a combustion chamber. The theoretical advantages can be derived from the Ford patent, but there is a lack of transferring these advantages to concrete proposals. By this reference, the principles theoretically disclosed in the Ford patent will apply as incorporated to the full extent in the present description of the invention.
Approaches for executing the teaching of U.S. Pat. No. 5,233,948 are known from
Another operating mode of a camshaft with adjustable double cam events is described in DE 10 2004 023 451 A1 (Applicant: General Motors Corp.; Priority date: May 16, 2003). Finally, the following two publications will be named: JP 11 17 31 20 (Applicant: Mitsubishi Motors Corp; Date filed: Dec. 8, 1997) and WO 1992/012 333 (Applicant: Porsche AG; Priority date: Jan. 12, 1991).
In summary, it can be seen that the following has been considered for many years: How can events in the gas-exchange valve train that are offset in time relative to one another be made adjustable in their phase positions?
DE 10 2005 014 680 A1 (Applicant: Mahle International GmbH, Priority date: Feb. 3, 2005) shows in several graphic representations a double camshaft that is equipped with a connected, grooved oil delivery unit in order to be able to further conduct the hydraulic oil to a hydraulic adjuster, which is not shown. Representatives of the Applicant company, Mahle International GmbH, presented technical descriptions of double camshafts that are described basically in DE 10 2005 014 680 A1 at the 16th Aachen Colloquium on Vehicle and Engine Technology 2007, showing figures and functional diagrams. As it was established at the colloquium, those skilled in the art have still not been able to successfully terminate their quest for suitable camshaft adjusters for appropriate double camshafts.
A camshaft adjuster for the relative rotating of a hollow camshaft and a second rotatable member disposed parallel to the first rotatable member is described in U.S. Pat. No. 6,253,719 B1 (Patent proprietor: Mechadyne PLC, Priority date: Feb. 18, 1999). Instead of arranging the two rotatable members with a type of disk structure next to one another, in the figures of U.S. Pat. No. 6,725,817 B2 (Patent proprietor: Mechadyne PLC, Priority date: Nov. 18, 2000), different embodiments of a nested adjuster lying in the same plane can be seen, whose first adjusting element can rotate a first set of cams of the concentric camshaft, while the second adjusting element is specific for the purpose of rotating a second set of cams of the concentric camshaft. In this way, the angular rotation of one set of cams influences the accessible angular region of the other set of cams. A similar presentation can also be taken from EP 1 234 954 A2 (Applicant: Mechadyne PLC, Priority date: Nov. 18, 2000). On the other hand, it would be more favorable if the sets of cams of the double camshaft could be adjusted as much as possible independently of one another in a further, larger adjustment range.
A type of connection for a double camshaft can be derived from EP 1 696 107 A1 (Applicant: Mechadyne PLC, Priority date: Feb. 23, 2005), in which both a camshaft adjuster as well as also an individual cam can be joined to the double-design camshaft by the use of cross-running pins. In this case, the pin is to be fitted with play in the crossbore of the camshaft.
The statement of the problem in U.S. Pat. No. 6,076,492 (Applicant: Yamaha Hatsudoki Kabushiki Kaisha, Priority date: Mar. 27, 1998) explains that in simply constructed camshaft adjusters of an axial displaceable type, there is a problem only in permanently aligning the camshaft adjuster, the cylinder head, the control valve and the camshaft in a stationary manner. Even for sufficiently known camshaft adjusters, there is a fear of jamming the individual components relative to one another.
Rotors with a broadened base are known from the publications DE 103 46 446 A1 and DE 103 46 448 A1 (Applicant: Daimler-Chrysler AG; Date filed: Oct. 7, 2003), the bases of which are fanned out opposite the vane width for reasons of stability or for conducting oil.
How camshaft adjusters can be connected to divided camshafts is shown in the drawings of DE 101 02 767 A1 (Applicant: Volkswagen AG; Date filed: Jan. 23, 2001). Each camshaft controls one type of gas-exchange valve. Thus, there is a camshaft adjuster for the gas inlet valves and a camshaft adjuster for the gas outlet valves. Each camshaft adjuster is disposed on the half of the camshaft belonging to it.
The presented embodiments of two gas-exchange valve actuation means that can be displaced or adjusted relative to one another in a control shaft are incorporated by their reference within the scope of the present description of invention, in order to increase the readability of the description of the invention in this way and thus to be able to emphasize the aspects of the present invention given below. The scope of their disclosure will be fully incorporated by their reference in the present description.
A gas-exchange valve control shaft, which is constructed from two camshafts that are disposed so that they engage in each other, preferably coaxially, the outer camshaft surrounding the inner camshaft, is also occasionally called a double camshaft. A double camshaft is a camshaft that is constructed in duplicate. Persons skilled in the art associate the term camshaft most frequently to a single shaft extending lengthwise on which all cams are disposed in a stationary manner relative to one another.
The problem to be solved by the present invention is to create a means by which a camshaft adjuster can be joined to a corresponding camshaft in order to operate the valve train of an internal combustion engine in a reliably flexible and optionally repeatedly exchangeable manner. Ideally, the camshaft adjuster can be adjusted or aligned to the camshaft during assembly. The individual groups of cams and the individual cams are to be reliably aligned to one another, to the remaining cams and groups of cams, particularly in the case of a double camshaft.
The technical problem will be solved by a device according to the present invention. Advantageous example embodiments can be derived from the description below.
A rotor, which is disposed in a specific angular range and can be moved between crosspieces of a stator that can also be configured as a part of the surrounding housing, can also be called a rotating vane. The term rotating vane refers rather to the vane-type construction of the central, middle, pivoting camshaft connecting member which is frequently referred to as the driven member, whereas the term rotor refers rather to the rotating property of the driven member in contrast to otherwise conventional axial-linear adjusting elements.
The camshaft adjuster is a part of a variable valve train of an internal combustion engine. The internal combustion engine has at least one gas-exchange valve control shaft. The gas-exchange valve control shaft has two concentrically disposed camshafts, which can be adjusted in a rotary manner relative to one another, i.e., at least two cams can be angularly rotated relative to one another. The camshaft is set in a relative relationship to a reference shaft that is dependent on the angle of rotation. It is particularly advantageous if the two camshafts can be considered as camshafts that are independent of one another. Each camshaft has a maximum angular range, which can be swept over independently of the other camshaft.
For reasons of exhaust technology, the valve train of an internal combustion engine is frequently constructed with a camshaft and a pivoting-rotor camshaft adjuster for changing the relative position of the camshaft to a second shaft. The second shaft is a crankshaft or drive shaft. The camshaft adjuster at least has the rotation components of a rotor and a stator. The components can be referred to as rotation components, since they can be variably rotated relative to one another and thus can assume different phase relationships relative to one another. Hydraulic chambers with variable, particularly opposite-running volumes, are formed between the rotor components. The respective chamber is larger or smaller due to a pivoting-rotor movement. At least one of the rotation components is joined to the camshaft by a pin engaging in the camshaft in such a way that positional changes of the rotor relative to the stator are transferred onto the camshaft by the pin or by a pin-like joining means. It has been shown, especially for double camshafts, that very long extended camshafts tend toward jamming and sticking. The invention proposes a solution in which the additional jamming can be reduced by a connected camshaft adjuster. Also, the connection will be produced rapidly and reliably during the assembly process. The connection can also be dismantled. The connection permits adjusting the camshaft relative to the camshaft adjuster.
The adjuster operating in a pivoting-rotor manner is also occasionally called an adjuster operating as a pivoting motor, although it is not a motor function that is carried out, but only a selection of position by means of the camshaft adjuster, operating particularly according to the rotating vane principle.
In accordance with an example embodiment of the present invention, the valve train comprises a double camshaft with an inner camshaft and an outer camshaft. The two camshafts are preferably designed coaxially. By means of a rotatory change in position of the inner camshaft to the outer camshaft, the angular position of at least one cam of the inner camshaft is adjusted or set relative to a cam or the outer camshaft. Advantageously, the cam of the inner camshaft is mounted on the outer camshaft, bound by means of a pin to the inner camshaft, so that it can pivot. The larger bearing surface of the outer camshaft can be utilized, while the event position of the valve train is made possible by an adjustment of the inner camshaft that possesses less mass.
The valve train can be adjusted variably to a reference shaft. The valve train comprises at least two camshafts. The valve train has at least one first camshaft and one second camshaft. The camshafts are disposed in .such a way that two of the camshafts are present as a coaxially configured double camshaft. The double camshaft is observed from the outside as a unified camshaft, the cams of which can be adjusted differently. The cams are divided into sets, which can occupy cam positions that are variable relative to one another. There is a camshaft adjuster for this purpose. The camshaft adjuster is preferably a pivoting-rotor camshaft adjuster. The camshaft adjuster is attached by its center to one of the two camshafts with a first set of rotatable components by a connection means that passes through the center of the camshaft adjuster and engages to a first (inner) of the two camshafts, the connection means comprising one of a screw or a central valve. The camshaft adjuster has different sets of components that are rotatable relative to one another, such as a rotor with vanes, at least one locking pin and oil conducting channels. A maximum radius is formed by a rim-type mounting flange to the second (outer) camshaft. There is at least one additional connecting means inside the radius that passes through the camshaft adjuster and engages the mounting flange. This additional connection means can be a screw. Ideally, there are several of such additional connection means that pass through and engage the mounting flange of the second camshaft second set of rotatable components of the camshaft adjuster. One part of the camshaft adjuster is rotatory concurrently with the first camshaft. The other part of the camshaft adjuster is rotatory concurrently with the second camshaft. A double camshaft can be conveniently, reliably and rapidly connected to a suitable camshaft adjuster in this manner.
In a valve train according to an example embodiment of the invention, the mounting flange can be shaped in one piece to the outside of the two camshafts. The outer camshaft can thus be a forged camshaft. The mounting flange is formed radially outward at one end of the camshaft. The screws can be introduced into the mounting flange in several places around it. The screws engage for a form-fit connection. Torque is introduced uniformly on the camshaft. The torque introduced on the camshaft adjuster via the driving force of the valve train, such as, for example, the chain drive, can thus be transferred to the entire outer camshaft.
The camshaft adjuster comprises a first set of rotatable components. A rotor may belong to the first set. The rotor serves for the formation of hydraulic chambers together with at least one additional component of the camshaft adjuster, such as a stator. The stator belongs to the second set of rotatable components. A free cut space is provided in one of the parts of the component sets. The free cut space is disposed in alignment with the orientation of the camshaft. A long, easy-to-attach component is formed. The at least one free cut space serves for the uptake of the connection means to be aligned axially to the camshaft. The type of fastening of camshaft adjuster and double camshaft according to the present invention requires no additional space for the connection means. The mounting flange can simultaneously serve as a bearing.
The free cut space in the camshaft adjuster has a certain length. The length of the free cut space is based on a complete removal of the connection means from the mounting flange. The diameter of the free cut space is larger than the widest place on the connection means. The free cut space transitions into a narrow-mouth guide channel. The narrow-mouth guide channel has an opening size that allows the fastening means that passes through to engage with as little play as possible. The free cut space narrows to a guide channel. The guide channel has the form of the back of the throat; it has narrow opening. The guide channel provides the access opening for a manipulating means. The manipulating means during fastening can be a screwdriver bit.
The outer, enveloping component of the camshaft adjuster, such as, for example, the stator, is equipped with a free cut space in one example embodiment. The free cut space can simultaneously represent an oil chamber. During operation, the hydraulic fluid can penetrate into the free cut space. A portion of the connection means that passes through the camshaft adjuster and engages with the mounting flange is to be lowered in the free cut space. During the phase when the camshaft adjuster is joined with the camshaft, the free cut space is utilized by the one or more connection means. No additional mounting space needs to be available.
The additional one or more connection means that pass through the camshaft adjuster and engage with the mounting flange is or are located within a radius. The imaginary radius or radius to be formed runs inside the camshaft adjuster. The radius is also disposed centrally around the central fastening means. The radius is smaller than the inner wall of the stator. In one example embodiment, the radius may be as small as possible, e.g., at a maximum, as large as the rotor core. All connection means are found in the center of the camshaft adjuster. The inertia of the camshaft adjuster is reduced in this way.
In another embodiment, the additional connection means that pass through and engage can be located in crosspiece-type sections of the enveloping part of the camshaft adjuster. They can also be partially placed in the crosspiece-type sections. The connection means or the screws can be located both partially in the crosspieces and partially outside-the crosspieces, thus, e.g., in the hydraulic chambers.
If the different types of connection means are oriented in opposite directions, then the connection means can be introduced from different sides into the camshaft adjuster and the valve train. The same side of the camshaft adjuster is not always perforated.
The camshaft adjuster has at least one trough-like configured recess in the crosspiece-type sections. Preferably, each crosspiece has a trough-like recess. The recesses may be present for expanding or widening the hydraulic chambers. The head of the additional connection means that passes through the camshaft adjuster and engages the mounting flange of the second camshaft can rest therein in form-fitting fashion by its side associated with the camshaft. Any material weakness worthy of note does not need to be considered if the hydraulic chambers transition into the recesses.
The camshaft adjuster that can be used particularly in a valve train according to an example embodiment of the invention has at least one rotor and at least one stator. In an alternative example embodiment, the camshaft adjuster has at least two rotors and one stator. Rotor and stator are rotatable together. The stator and the at least one rotor form hydraulic chambers that run opposite to one another and can be braced differently. The sizes of the hydraulic chambers are formed by a pivoting-rotor movement of the rotor. The camshaft adjuster is equipped with a central connection means that passes through the camshaft adjuster and engages with the first camshaft, for fastening to a double camshaft. The rotor has at least one free cut space. The free cut space is adapted in its dimensions to another connection means for fastening the stator to one of the two camshafts of the double camshaft for possible disassembly. An easy-to-mount compact unit is nevertheless formed from the camshaft adjuster and the double-design camshaft, the double camshaft.
According to one aspect, the invention is characterized in that even high torques can be transferred. A double camshaft can be driven with a previously known, conventional pivoting-rotor camshaft adjuster, if connection means of the second type are provided at the locations designated according to the invention inside the camshaft adjuster. All the trials and extensive experience over many years from the field of pivoting-rotor camshaft adjusters can be transferred to the valve train with a double camshaft. A double camshaft permits adjusting an event, thus modifying the opening and closing behavior of the gas-exchange valves, within a single valve train.
The present invention will hereinafter be described in conjunction with the appended drawing figures, wherein like reference numerals denote like elements, and:
Similar objects and functionally equivalent parts are disclosed by the same reference characters in all embodiment examples (increased by 200 in each case) for aiding in understanding, although slight differences may be indicated between the individual embodiments.
The ensuing detailed description provides exemplary embodiments only, and is not intended to limit the scope, applicability, or configuration of the invention. Rather, the ensuing detailed description of the exemplary embodiments will provide those skilled in the art with an enabling description for implementing an embodiment of the invention. It should be understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the invention as set forth in the appended claims.
In an alternative embodiment, as shown in
The rotor vanes 140, 142, 144, 146, 148, together with stator vanes 128, 130, 132, 134, 136, which are also designated as stator crosspieces, form chambers 174, 176 between them. The chambers 174, 176 appear several times in the camshaft adjuster 100. To the extent that one of the chambers 174 increases in size due to a hydraulic loading, the size of the other chamber 176 decreases. A relative position of the rotor 104 to the stator 102 is established between the vanes 140, 142, 144, 146, 148 and 128, 130, 132, 134, 136 due to hydraulic pressure. The stator 102 is composed not only of the stator housing 108, but other components, such as, for example, an insert plate 110 (see
The stator 102 is configured as rotatory. Different rims 122, 124 along the radius 126 of the camshaft adjuster 100 (seen virtually) can be associated therewith. The camshaft adjuster 100 has a center 120, which can be subtracted from the radius 126. Radii that are designated as first rim 122 and as second rim 124 are formed on radius 126. The second rim lies beyond the first rim 122, e.g., it has at least double the circumference of the first rim 122. The camshaft adjuster 100 has different connection means 156, 158, 160. The connection means 156, 158, 160 lie inside a maximum radius 126, which is defined by the inner wall 114 of the stator 102. The connection means 156, 158, 160 take over different tasks. A first connection means 156, in a force-fitting manner, produces the connection between rotor 104, more precisely rotor core 106, and one of the camshafts 184, 186. Ideally, the inner camshaft 184 is joined to the rotor 104 via the connection means 156. The other connection means 158 (see
In the case of hydraulic undersupplies in the chambers 174, 176, a fastening means 150 for the positionally rigid fixation of the rotor 104 to the stator 102 is in a locked position. In order to increase the sealing effect between the individual chambers 174, 176, sealing strips 154 can be provided in individual vanes 146. With a suitably precise manufacture, the sealing strips 154 may be omitted in most vanes. Since the stator 102 is composed of several parts such as the stator housing 108 and the drive wheel 200, additional connection means, third connection means 160, must brace the individual, enveloping parts 112 of the camshaft adjuster 100. For this purpose, the stator vanes 128, 130, 132, 134, 136 have special recesses 138, so that the connection means 160 of the third type can pass through and engage from one part of the stator 102 into the other part of the stator 102. Offset relative to the connection means 160, the connection means 158 of the second type are placed in the camshaft adjuster 100, oriented further in the direction to the center 120. The connection means 158 all lie on rim 122 of rims 122, 124, which are enclosed by the inner wall 114 of the stator. The recess 138 lies approximately in the middle of the stator vane 132. For the supply of the chambers 174, 176, hydraulic-fluid channels 178 are made in the rotor 104, and these channels are protected against leakage at transition regions between the first set of rotatable components 116 and the second set 118 of rotatable components by additional hydraulic-fluid channel covers 180 that produce the seals. The connection means 158 of the second type lying on the rim 122 open up into free cut spaces 204. It is particularly advantageous if the individual connection means 156, 158, 160 are produced by screw connections by means of screws 162, 164, 166. It is particularly advantageous if at least one screw 166 of the screws 162, 164, 166 has an orientation that is different than the remaining screws 162, 164. The orientation 170 of the screws 166 runs anti-parallel to the orientation 168 of the largest screw 162, which joins the rotor 102 with the double camshaft 182 on its end 190 by screwing onto the inner camshaft 184. The double camshaft 182 has a mounting flange 198, in which the screws 164 of the second type can be screwed in.
As can be seen in
Due to the narrow-mouth configuration of the guide channel 214, the guide channel 214 is narrower than the normal width 210 of the free cut space 204, and thus narrower than the width 212 of the connection means; it cannot be lost when the camshaft adjuster 100 is detached from the mounting flange 198 of the double camshaft 182. If the camshaft adjuster 100 is assembled, then fastening screws 164 for the mounting flange 198 are placed in each free cut space. The camshaft adjuster 100 is held together in its compact form by the screws 166 of the third type. The screws 166 brace the drive wheel 200 to another part of the stator 102, such as the stator trough. When the camshaft adjuster 100 is mounted on the double camshaft 182, in order to form a valve train 222, one of the two screw types 162, 164 can be joined alternately to one of the two camshafts 184, 186. The camshaft adjuster 100 thus is mounted on the double camshaft 182 after the first fastening step, but the double camshaft can still be adjusted with respect to the exact cam position of the cams 194 relative to the cams 196 of the second type. For this purpose, a fastening tool, such as a torque wrench, engages through the guide channels 214 into the respective heads 172 of the screws 164. The head 172 of the connection means specific for the mounting flange 198 is broader in its width 212 than the guide channel 214 but slightly narrower than the width 210 of the free cut space 204. Numerous seals 216, 218, 220 and components such as the hydraulic-fluid channel cover 180 with a sealing function are placed in the valve train 222, in order for the hydraulic fluid to flow, as much as possible without loss, along the channels, such as the bearing channel 192, into the chambers, such as chamber 174. Thus the cover 202 to be introduced subsequently can further reduce the leakage of the camshaft adjuster 100; at least one seal 216, ideally two seals 216, 218, is or are inserted into the cover 202 between stator housing 208 and cover 202. One of the seals 216, 218 can simultaneously be designed as a snap ring or spring seal in order to brace the cover 202 with the stator housing 108 in a snap-in manner. Despite the three screws 162, 164, 166 lying within circles, the camshaft adjuster 100 does not need to be much longer than comparable camshaft adjusters which are provided only for single camshafts instead of a double camshaft 182. The compact form of the camshaft adjuster 100 can be retained, although it can control a double camshaft 182. The circumstance is produced, inter alia, in that the free cut space 204 is disposed parallel to one chamber 174.
In
Another example embodiment can be seen in the two
As can be derived from the further example embodiment shown in the two
It should now be appreciated that the present invention provides advantageous embodiments of a camshaft adjuster.
Although the invention has been described in connection with various illustrated embodiments, numerous modifications and adaptations may be made thereto without departing from the spirit and scope of the invention as set forth in the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2010 033 296 | Aug 2010 | DE | national |
