Abstract:
A camshaft adjuster for an internal combustion engine, having a stator, a rotor mounted rotatably in the interior of the stator, and a locking cover connected to the stator. A hydraulically actuatable locking element is received in the rotor and engages into the locking cover in at least one blocking position, so as to block a rotation of the rotor relative to the stator, and is arranged in at least one unlocking position so that the rotor can be rotated relative to the stator. A blocking pin acts in at least one hydraulic channel connected hydraulically to the locking element so that the hydraulic channel is connected to a recovery tank or is disconnected from the recovery tank depending on the position of the blocking pin, wherein the hydraulic channel has a first channel section in the locking cover, and the first channel section and the blocking pin are arranged so that the blocking pin seals the hydraulic channel from the recovery tank in at least one first end position, in a first pressure range which prevails in the hydraulic channel by way of contact with the locking cover.

Description:
[0001]    The present invention relates to a camshaft adjuster, namely preferably a vane-type hydraulic camshaft adjuster for an internal combustion engine, for example a gasoline or diesel engine, of a motor vehicle, such as a passenger car, truck, bus or agricultural commercial vehicle, including a stator, including a rotor rotatably supported in the interior of the stator as well as including a locking cover connected to the stator, a hydraulically actuatable locking element being accommodated in the rotor, which engages with the locking cover in at least one blocking position and blocks a rotation of the rotor relative to the stator and is situated in at least one unlocking position in such a way that the rotor is rotatable relative to the stator, a blocking pin acting in at least one hydraulic channel, which is hydraulically connected to the locking element, in such a way that the hydraulic channel is connected to a recovery tank or is disconnected from the recovery tank depending on the position of the blocking pin. 
       BACKGROUND 
       [0002]    In principle, camshaft adjusters of this type are already known in various designs from the prior art. These camshaft adjusters may be integrated into a timing drive of the internal combustion engine and be provided, for example, for chain or belt drives. 
         [0003]    DE 10 2005 024 242 A1 known from the prior art discloses a device for variably setting the timing of gas exchange valves of an internal combustion engine. This device includes a drive element, which is in drive connection with a crankshaft, and an output element, which is in drive connection with a camshaft, at least one pressure chamber being formed between the drive element and the output element, and each pressure chamber being divided into two oppositely acting pressure chambers by a vane which is rotatably fixedly situated or formed on the output element. First and second pressure medium lines are also present, pressure medium being conductible to or removable from the first pressure chambers via the first pressure medium lines, and pressure medium being conductible to or removable from the second pressure chambers with the aid of the second pressure medium line. A locking device is also present in the device, which includes a receptacle formed on the output element or the drive element, a slotted gate formed on the other component, a locking pin situated in the receptacle and a spring, which pushes the locking pin in the direction of the component on which the slotted gate is formed. The locking pin engages with the slotted gate in a defined locking position of the output element relative to the drive element, it being possible to push the locking pin back into the receptacle by the application of pressure medium to the slotted gate, and at least one pressure medium connection being provided between the slotted gate and the pressure chamber or the associated pressure medium lines, to which pressure medium is applied for the purpose of withdrawing the drive element from the locking position. Each pressure medium line is implemented with the aid of exactly one pressure medium channel, the pressure medium channel being connected to the pressure chamber or the pressure medium line, on the one hand, and to the slotted gate, on the other hand, one of the two connections being established in each position of the output element relative to the drive element, and the other connection and the connection between the pressure medium channel and the locking pin being established only when the output element is in the locking position relative to the drive element. 
       SUMMARY OF THE INVENTION 
       [0004]    The applicant is also aware of internal technology that has not yet been published, in which the hydraulic channel (also referred to as the control channel) is controlled with the aid of a kind of switching valve, and a relief of the hydraulic channel (also referred to as the C channel) takes place with the aid of a hollow pin. 
         [0005]    In the embodiments known from the prior art or previously, however, it is disadvantageous that long flow paths of the hydraulic medium (e.g., oil), in turn, are effectuated in the hydraulic channel, since relatively complex switching valves are used (for example, a separate, additional C port, a separate control channel being present for the locking pin/locking element). Due to these relatively long flow paths and the relatively complex design of the switching valves used, the flow resistance, i.e. the resistance in the flow channel, is relatively high, so that excessively long load times may occur when switching from the blocking position to the unblocking position and/or vice versa. When the engine stops, in particular, it is necessary to ensure a fast relief of the hydraulic channel/C channel by opening the hydraulic channel in the direction of the recovery tank. Also when the engine starts up, a rapid closing/locking of the hydraulic channel is to take place in the direction of the recovery tank to place the camshaft adjuster preferably quickly in the unblocking position, in which the rotor is rotatable again relative to the stator. 
         [0006]    It is an object of the present invention to eliminate the disadvantages known from the prior art or previously and to ensure a fast and safe closing/blocking behavior of the hydraulic channel in the direction of the recovery tank when the engine starts up. 
         [0007]    The present invention provides that the hydraulic channel includes a first channel section, introduced into the locking cover, the first channel section and the blocking pin being designed and situated relative to each other in such a way that the blocking pin seals the hydraulic channel from the recovery tank in at least one first end position, within a first pressure range prevailing in the hydraulic channel by way of contact with the locking cover. 
         [0008]    As a result, the blocking pin and the locking cover themselves are used directly as sealing elements, for example in the blocking position. The blocking pin as such may have a much simpler and more compact structural design. This, in turn, effectuates a faster response of the locking system when switching between the blocking and unblocking positions and vice versa. 
         [0009]    According to another specific embodiment, it is thus advantageous if the blocking pin is displaceable between the first end position, in which it is situated/pushed/placed up to a determined, first hydraulic pressure value, and a second end position, in which it is situated/pushed/placed upon reaching a second hydraulic pressure value (second hydraulic pressure value is preferably greater than the first hydraulic pressure value), in the axial direction within the rotor for the purpose of switching from the blocking position to the unblocking position. A particularly space-saving design may thus be implemented, as well as a blocking pin which has a blocking effect in both the first and the second end position and separates the hydraulic channel from the recovery tank. 
         [0010]    The blocking pin is furthermore provided in such a way that it hydraulically connects the hydraulic channel to the recovery tank in an intermediate position, i.e. a displacing position, between the first and second end positions. The particular settable intermediate position is dependent on the hydraulic pressure value prevailing in the hydraulic channel, the higher the hydraulic pressure value in the hydraulic channel upon exceeding the first hydraulic pressure value, the closer is the blocking pin displaced/pushed/positioned in the direction of the second end position until the blocking pin arrives at the second end position upon reaching the second hydraulic pressure value. This means that, together with the blocking pin, a pressure relief valve/pressure relief unit is made available with the aid of which hydraulic pressure may be built up and reduced within the hydraulic channel (depending on the position of the blocking pin). A particularly simple and space-saving system is facilitated thereby. 
         [0011]    In this connection, it is also advantageous if the blocking pin has a first end face facing the locking cover, which abuts the first channel section in a sealing manner in the first end position. Due to an end face of this type, the first channel section may be easily formed in the locking cover, whereby the manufacture of the camshaft adjuster is further simplified. 
         [0012]    It is also advantageous if the blocking pin has a second end face facing away from the locking cover in the operating state of the camshaft adjuster, which rests against the hydraulic channel in the second end position on the rotor side, thereby sealing the recovery tank. A second stop of the blocking pin is easily provided thereby, for the purpose of blocking/sealing the recovery tank even under the high operating pressure (namely the second hydraulic pressure value) upon the recovery tank during operation. The second end position is preferably assumed in the unblocking position, and the first end position is preferably assumed in the blocking position, the intermediate position being usable for the purpose of switching back and forth between the unblocking position and the blocking position. 
         [0013]    If the first end face is furthermore provided with an annular design, and if the hydraulic pressure set in the hydraulic channel is applied to a portion of the first end face in the first end position, the switching behavior between the blocking position and the unblocking position may, in particular, be further improved. After all, the hydraulic pressure prevailing in the hydraulic channel thus does not act upon the entire first end face but only on one portion which is why a higher pressure value must initially be reached to displace the blocking pin than if the hydraulic pressure were to act upon the entire first end face. The hydraulic pressure prevailing in the hydraulic channel is thus not applied to another, second and/or third portion of the first end face in this first end position. This has the advantage that the blocking pin is accelerated and moved much faster upon reaching the first hydraulic pressure value, due to the higher level of the hydraulic pressure value required for moving the blocking pin. After all, when the blocking pin lifts off of the locking cover, the hydraulic pressure prevailing in the hydraulic channel is applied to the entire first end face, whereby an additional acceleration of the blocking pin occurs. The hydraulic pressure prevailing in the hydraulic channel acts upon the entire first end face in each intermediate position between the first and the second end positions. The corresponding hydraulic pressure/hydraulic pressure value then also acts upon the entire first end face in the second end position. 
         [0014]    In this connection, it is furthermore advantageous if the first end face of the blocking pin has a smooth/even design, whereby a sealing action in the first end position is further simplified. 
         [0015]    If the blocking pin is also designed as a hollow pin and has a continuous through-hole in the axial direction, the hydraulic connection between the first and the second end position is particularly easy to carry out in the intermediate positions of the blocking pin. 
         [0016]    In this connection, it is also advantageous if the blocking pin has a flow diaphragm which reduces the cross section of the through-hole. The flow diaphragm is preferably situated in the through-hole (viewed in the axial direction), adjacent to the first end face. The through-hole thus expands from a first diameter in the area of the first end face to a second diameter in the area of the second end face. The flow may be efficiently regulated thereby. 
         [0017]    In this connection, it is also advantageous if the axial width of the flow diaphragm is smaller than the length of the blocking pin. Alternatively or additionally, if the surface area of the flow diaphragm is smaller than the surface area of the through-hole, a particularly effective blocking and connection of the hydraulic channel is made possible in the direction of the recovery tank in the particular blocking or unblocking position of the camshaft adjuster. 
         [0018]    If the blocking pin is furthermore partially or entirely manufactured from a plastic material and/or a metal material, the blocking pin may furthermore be provided with a particularly lightweight and wear-resistant design, which, in turn, is advantageous with respect to the response time. 
         [0019]    It is also preferred if the through-hole is designed as a bore, namely a through-bore, whereby the manufacture of the through-hole is further simplified. 
         [0020]    It is also advantageous if the through-hole is situated and designed in such a way that a flow of hydraulic medium is prevented in the first end position of the blocking pin. The pressure in the area of the blocking pin may be particularly rapidly built up thereby for switching between the blocking position and the unblocking position, without a certain portion escaping through the through-hole. 
         [0021]    If the first channel section is hydraulically connected to a second channel section of the hydraulic channel introduced into the rotor, the locking cover need only be provided with the first channel section around a certain circumferential area, whereby its manufacturing costs are further reduced. This channel section is preferably pressed in or milled in or manufactured by sintering. 
         [0022]    It is furthermore advantageous if the blocking pin is spring-pretensioned in such a way that it abuts the locking cover in a supporting manner in the blocking position (in the first end position), thereby sealing the hydraulic channel from the recovery tank. As a result, a seal is ensured in the blocking position, which is reproducibly situated directly in the first end position for generating the unblocking position during the pressure buildup. The switching times are further shortened thereby. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The present invention is now described below on the basis of multiple figures, in which connection different specific embodiments are explained. 
           [0024]      FIG. 1  shows a front view of a camshaft adjuster according to the present invention according to a first specific embodiment, the camshaft adjuster being illustrated from a side on which the locking cover is situated, and the camshaft adjuster being situated in a blocking position, in which the locking elements engage with locking gates of the transparently illustrated locking cover; 
           [0025]      FIG. 2  shows a detailed view of the area of the end face of the blocking pin identified by II in  FIG. 1 , the contact of the blocking pin in the first end position being apparent in particular, in which the through-hole of the blocking pin is hydraulically separated from the hydraulic channel; 
           [0026]      FIG. 3  shows a front view of the camshaft adjuster according to the present invention, as illustrated in  FIG. 1  above, but with the locking cover removed in this case; and 
           [0027]      FIG. 4  shows a side view of the locking cover installed in  FIG. 1 , which is illustrated from an inside, i.e. a side facing the rotor in the operating state, and, in particular, the course of the first channel section as well as the arrangement thereof with respect to the locking gates, are readily apparent. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    The figures are only of a schematic nature and are used exclusively for the sake of understanding the present invention. Identical elements are provided with identical reference numerals. 
         [0029]    Camshaft adjuster  1  according to the present invention is clearly apparent in  FIG. 1  according to a first specific embodiment. The camshaft adjuster as such is designed, in principle, like the one disclosed in DE 10 2005 024 242 A1, the disclosure being therefore regarded as incorporated by reference herein. Camshaft adjuster  1  is thus provided for an internal combustion engine of a motor vehicle and includes both a stator  2 , which is rotatably fixedly connected to a crankshaft of the internal combustion engine in the operating state, preferably with the aid of a timing drive (belt or chain drive), and which is drivable thereby, and a rotor  3 , which is fastened to a camshaft of the internal combustion engine in the operating state and is rotatably supported in the interior of stator  2 . A hydraulically actuatable first locking element  4  as well as a likewise hydraulically actuatable second locking element  5  are accommodated in the rotor. In a blocking position, first and second locking elements  4  and  5  each engage with a locking cover  6 , which is rotatably fixedly connected to stator  2 , in such a way that a rotation of rotor  3  relative to stator  2  is avoided/blocked in this blocking position. In an unblocking position of camshaft adjuster  1 , these locking elements  4  and  5  are situated in such a way that rotor  3  is able to rotate relative to stator  2 . The blocking position in this case is designed as a central locking position, for which reason, in the blocking position, vanes  7  of rotor  3  are situated centrally in the particular working chambers  8  formed in stator  2 . 
         [0030]    A hydraulic channel  9  is furthermore provided between locking cover  6  and rotor  3 . This hydraulic channel  9  includes a channel section, hereinafter referred to as second channel section  11 , which is formed/introduced/milled in on the side of rotor  3  facing locking cover  6  (in the operating state). This second channel section  11  is hydraulically connected to an inlet/inlet opening  12 , which is further connected to a delivery pump. Hydraulic channel  9  also includes a first channel section  10 , which is (hydraulically) connected to second channel section  11  and which is formed by a channel-shaped recess on the end face facing rotor  3  in the operating state. First channel section  10 , which is formed in the manner of a slotted gate, as is further apparent in  FIG. 1 , runs from second, essentially annular channel section  11  inwardly to an outlet opening  13  in the radial direction, from two areas which are spaced a distance apart along the circumference. 
         [0031]    A blocking pin  14 , which is displaceable in the axial direction, is situated in outlet opening  13 . Outlet opening  13  also extends essentially in the axial direction (i.e., along the rotation axis of camshaft adjuster  1 ). Second channel section  11  of hydraulic channel  9  is hydraulically connected to the two locking elements  4  and  5 , on the one hand, and to first channel section  10 , on the other hand. Blocking pin  14  is situated in such a way and acts upon hydraulic channel  9  in such a way that hydraulic channel  9  is connectable to a recovery tank, which is not illustrated in greater detail here for the sake of clarity, or is disconnectable from the recovery tank, depending on its position. First channel section  10  and blocking pin  14  are designed and situated relative to each other in such a way that blocking pin  14  seals hydraulic channel  9  from the recovery tank in at least one first end position, as illustrated in  FIGS. 1 and 2 , within a first pressure range set in the hydraulic channel, by way of contact with locking cover  6 . 
         [0032]    For switching from the blocking position into the unblocking position, blocking pin  14  is displaceably supported in the axial direction within rotor  3  between the first end position, in which blocking pin  14  is situated up to a certain first hydraulic value (measured in hydraulic channel  9 ), and a second end position, in which it is situated upon reaching a second hydraulic pressure value, which is greater than the first hydraulic pressure value. In both the first end position and the second end position, blocking pin  14  has a blocking/obstructing effect on hydraulic channel  9  and prevents a pressure fluid flow from hydraulic channel  9  to the recovery tank and vice versa. 
         [0033]    As is furthermore clearly apparent in interaction with  FIGS. 2 and 3 , blocking pin  14  has an essentially circular outer circumferential surface. Centrically, blocking pin  14  has a through-hole  15  designed as a through-bore, which completely penetrates blocking pin  14  over its entire length. 
         [0034]    As is also clearly apparent in connection with  FIGS. 1 and 2 , through-hole  15  is introduced into blocking pin  14  in such a way, and blocking pin  14  abuts a projection area  16  introduced into first channel section  10  by a first annular end face  17  acting as a sealing surface in such a way that no hydraulic medium flows between hydraulic channel  9  and through-hole  15 . 
         [0035]    First channel section  10  is interrupted by projection area  16  and is thus divided geometrically into two parts. Projecting area  16  has an essentially circular design and forms an essentially circular elevation, which forms a flat surface, on which blocking pin  14  rests planarly with its end face  17 , as is apparent in  FIG. 2 . The contact between projection area  16  and a first portion  18  of first end face  17  thus forms a seal. In other words, through-hole  15  is hydraulically separated from hydraulic channel  9  in the first end position. 
         [0036]    In a second portion  19  and a third portion  20 , first channel section  10  circumvents first end face  17  in the first end position, where it acts upon first end face  17  with the aid of the hydraulic pressure of hydraulic channel  9 . The two second and third portions  19  and  20  particularly preferably occupy approximately one third of the total area of first end face  17 . Blocking pin  14  is also referred to as a hollow pin, due to the formation of through-hole  15 . 
         [0037]    A flow diaphragm  21  abuts first end face  17  directly in through-hole  15 . In other words, through-hole  15  forms flow diaphragm  21  in the area of first end face  17 . Flow diaphragm  21  extends only over a certain length of blocking pin  14 , the (first) diameter of flow diaphragm  21  expanding to a second diameter, which is larger than the first diameter, with respect to second end face of blocking pin  14  facing away from first end face  17 . 
         [0038]    The second end face, which is not illustrated herein for the sake of clarity, in turn, abuts a rotor-fixed component, i.e. on the rotor side, in a second end position of blocking pin  14 , again sealing the recovery tank against hydraulic channel  9 . Blocking pin  14  is furthermore spring-elastically pretensioned with the aid of a spring element, which is also not illustrated herein for the sake of clarity, in such a way that it is pressed out of outlet opening  13  in the direction of locking cover  6 . The spring force of this spring element is selected in such a way that blocking pin  14  is supported in the first end position within a first pressure range below a certain first hydraulic pressure value. 
         [0039]    To switch from the blocking position into the unblocking position, the hydraulic pressure in hydraulic channel  9  is initially increased until the first hydraulic pressure value within hydraulic channel  9  is reached. If the first hydraulic pressure value is exceeded, first end face  17  lifts away from projection area  16 , and through-hole  15  is unblocked. 
         [0040]    This makes it possible for hydraulic medium to flow between hydraulic channel  9  and the recovery tank in an intermediate position/intermediate point between the second and first end positions of blocking pin  14 . Due to the lifting action, the particular hydraulic pressure of hydraulic channel  9  no longer acts only upon the two second and third portions  19  and  20  of blocking pin  14  but also upon entire first end face  17 , i.e. upon first portion  18 , whereby the force against the spring element is increased. As a result, an even faster displacement of blocking pin  14  occurs when switching from the blocking position into the unblocking position. 
         [0041]    If the hydraulic pressure in hydraulic channel  9  is further increased to a second hydraulic pressure value, which is greater than the first hydraulic pressure value, blocking pin  14  strikes against the second end position. In this second end position, it again blocks hydraulic channel  9  from the recovery tank. At the same time, the two first and second locking elements  4  and  5  are pressed out of gate receptacles in locking cover  6  in the second end position, whereby rotor  3  is rotatable relative to stator  2 . 
         [0042]    Upon again switching from the unblocking position into the blocking position, the pressure is initially reduced via inlet line  12 , whereby the pressure in the area of hydraulic channel  9  and thus also at first end face  17  is likewise reduced until blocking pin  14  is again moved back into the first end position due to the spring action of the spring element. As a result, the two locking elements  4  and  5 , which are designed as locking pins, are again inserted into corresponding gate receptacle  22  in locking cover  6 . The arrangement of inlet opening  12  relative to blocking pin  14  is, in turn, illustrated particularly clearly in  FIG. 3 . 
         [0043]    The course of first channel section  10  is also clearly apparent in  FIG. 4 , which is situated along the circumference, offset with respect to the two slotted gate receptacles  22 . 
         [0044]    In other words, a hollow pin (blocking pin  14 ), including diaphragm/flow diaphragm  21 , may thus be integrated into a C channel (first channel section  10 ) of a camshaft adjuster  1 , so that it is possible to cover diaphragm opening (through-hole  15 ) with the aid of a slotted gate (first channel section  10 , including projection area  16 ) in the locking position/blocking position. Hollow pin  14  seals C channel  10  against the tank/recovery tank in the operating state. Upon dropping below a minimum pressure, hollow pin  14  moves in the direction of the tank as a result of the spring force of the spring element and thus opens C channel  10 . Diaphragm opening  15  is covered when starting from the locking position/blocking position. This achieves the fact that the pressure buildup in C channel  10  upon engine startup is able to take place without the oil/hydraulic medium flowing out directly through diaphragm  21 , which may cause problems with the starting functionality, in particular in the case of low viscosity oil. Due to the partial coverage of the contact surface (end face  17 ) of pin/hollow pin  14  in this position, a higher pressure is needed to set pin  14  in motion. Due to the subsequent release of a larger active surface (circular ring surface of the entire pin head immediately upon insertion of the pin), the action of force upon pin  14  is further increased by the oil pressure. A fast and secure closing of the C-T port thus occurs during startup, even at very low viscosities. The coordination of the starting and closing dynamic of pin  14  takes place via the configuration of spring force and the negotiation of covered pin surface/end face  17  with the released surface. 
         [0045]    The hollow pin preferably has an axial passage (through-hole  15 , preferably designed as a bore). This passage  15  may be provided with a diaphragm  21 . The position of diaphragm  21  is axially freely selectable as needed. The axial width of diaphragm  21  is preferably smaller than the pin length/length of pin  14 . The surface area of diaphragm (diameter)  21  is smaller than the surface area/diameter of through-hole  15 . The material of the pin may be plastic or another material, depending on the application. The slotted gate (first channel section  10 ) and projection area  16  are introduced into cover/locking cover  6  in such a way that a connection between pin  14  and C channel  10  exists even in the locking position/blocking position and only a covering of diaphragm bore  15 / 21  of pin  14  is achieved. Pin  14  preferably has a smooth head, i.e., a smooth/even end face  17 , preferably without indentations, to prevent a transverse inflow into diaphragm bore  15 . This requires a special indentation/a special projection area  16  in C channel  10  for flowing out into diaphragm opening  15  in the case of a shutdown outside the locking position. 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
           1  camshaft adjuster 
           2  stator 
           3  rotor 
           4  first locking element 
           5  second locking element 
           6  locking cover 
           7  vane 
           8  working chamber 
           9  hydraulic channel 
           10  first channel section 
           11  second channel section 
           12  inlet opening 
           13  outlet opening 
           14  blocking pin 
           15  through-hole 
           16  projection area 
           17  first end face 
           18  first portion 
           19  second portion 
           20  third portion 
           21  flow diaphragm 
           22  slotted gate receptacle