Abstract:
Camshaft adjusters according to the swivel motor principle may be provided with a bar which arrests the rotor in a position relative to the stator. A bar according to the invention is provided with two portions, between which a change of power transmission takes place during the arresting process.

Description:
CROSS REFERENCE 
     This application claims priority to German application number 10 2005 004 281, filed Jan. 28, 2005. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a camshaft adjuster with play-free locking according to the preamble of Claim  1 . 
     There are numerous camshaft adjusters. Apart from helically toothed camshaft adjusters, camshaft adjusters according to the swivel motor principle are widely used. As a rule swivel motor camshaft adjusters have a housing which is also called a stator and in which a rotor with an arbitrary number of blades can move. Chambers for accommodating a hydraulic fluid such as, for example, a motor oil, are formed between webs of the stator and the blades of the rotor. The freedom of motion between the rotor and the stator may optionally be limited or impeded by a bar. Bars of this kind or locking pins are frequently spring-biased. The bar is only moved into an unlocked position when a spring force is overcome. A hydraulic pressure acting on the blade or blades of the rotor then allows a swivelling movement to take place within an angle of rotation by means of which a connected camshaft of an internal combustion engine is changed in terms of its position and therefore its opening and closing times with respect to a driving shaft, such as a crankshaft. A torque is transmitted via the stator from the crankshaft or another shaft of the internal combustion engine to rotor and the connected camshaft. The locking bar must be designed such that the entire torque can be transmitted via the bar. The bar should also lock securely if required and not jam such that unlocking is not guaranteed in another state. 
     Numerous proposals for locking pins, which are frequently biased by a spring, can be found in the patent literature. FIG. 2 of U.S. Pat. No. 5,836,276 shows a pin parallel to the camshaft which is to lock a rotor with respect to a cover. The end which projects into the cover is of frustoconical formation. The receptacle in the cover is distinctly larger. A pin of this kind would also have to be adjustable frequently during operation, and a non-superaudible rattling noise would probably be perceptible under load changes on account of the play between the housing, the cover and the pin. 
     Similar dimensions would also appear to be found in the case of the multi-stepped pin of FIG. 4 from DE 101 49 056 A1. The lower end is frustoconical in order to accommodate the bevelled ends of the pin. The frustoconical end of the receptacle of the cylindrically shaped tip of the locking pin is of larger dimensions than the actual cylindrical tip. Rattling noises can also be heard in this kind of configuration of the locking unit of a camshaft adjuster, 
     FIG. 5 a  of U.S. Pat. No. 6,497,208 B2 shows that the frustoconical tip of the locking pin can be pushed into a round trough of approximately the same dimensions. There is only slight line contact between the two components. The entire torque must be transmitted via the line contact between the two connected shafts of the internal combustion engine. Pins which have receptacles and are better adapted to one another in terms of their dimensions can be found in JP 2001050018 A, DE 100 38 082 A1, in particular FIG. 11, U.S. Pat. No. 6,474,280 B2, in particular FIG. 1, and FIG. 3 of DE 197 42 947 A1. The Japanese publication shows a cylindrical pin with a cylindrical receptacle. In U.S. Pat. No. 6,474,280 B2 and DE 100 38 082 A1 the frustoconical tip of the locking pin engages in the locking state in a frustoconical trough which is dimensioned to correspond exactly to the pin. DE 197 42 947 A1 comprises further dimensioning of a pin, the multiform contour of which can only be produced at a high cost. 
     DE 196 23 818 A1, in particular FIG. 1, discloses a locking pin which presents an oval torsion-like surface in its front part. Manufacturing qualities have to be taken into account here too for the purpose of exact play. 
     SUMMARY OF THE INVENTION 
     It is obvious that the professional world has for a long time been searching for a locking pin or bar which, during operation, even at high angle of rotation velocities, is securely caught, equally securely unlocked, can be easily produced, can transmit the entire torque from the stator to the rotor and generates as little rattling noise as possible under substantial load changes. 
     A locking bar according to the invention with a corresponding receptacle according to Claim  1  approaches these idealized requirements by way of inevitable compromises between the numerous requirements. Advantageous developments can be found in the dependent claims. 
     A camshaft adjuster which operates according to the swivel motor principle has a rotor and a stator. A driving shaft is connected to the rotor, and the driven shaft is connected to the stator. Together the stator and the rotor form at least two hydraulic chambers acting in opposition. If one hydraulic chamber expands, the other hydraulic chamber is reduced accordingly. Ideally the pressure of one hydraulic chamber acts on one side of a blade of the rotor and thus moves the rotor in the direction of the other hydraulic chamber. The camshaft adjuster also comprises an arresting unit. The arresting unit has components such as a plate, a biasing means and a bar. If the biasing means is a spring means, the plate forms a spring plate. The arresting unit may be disposed both in the rotor and in the stator. The bar has a corresponding receiving opening in the respective other component, stator or rotor, which corresponds to the shape of the bar tip, which can enter the receiving opening. The function of the arresting unit is to afford a firm connection or anchorage when the rotor is in a certain position relative to the stator. The rotor and the stator are arrested. The actual bar may be divided into a plurality of portions. A first portion is an advance power transmission portion. As the bar may have a round or an oval or an elliptical shape, the first portion has a first diameter. This diameter is either the absolute diameter or an average diameter of an elliptical shape, depending on the shape. In addition to the first portion, the bar has a further, second portion. The second portion performs the wedging function. The rotor and the stator are arrested once wedging has taken place. The wedging portion has a particular diameter. Both the first diameter and the second diameter are in the corresponding receiving opening when the camshaft adjuster is in the arrested state and are enclosed by the subassembly lying opposite an arresting unit. The actual receiving opening has a larger diameter than the first portion, the advance power transmission portion. If the arresting unit enters the receiving opening on account of, for example, the reduction of hydraulic pressure against the biasing means on the bar, arresting firstly takes place via the advance power transmission portion. However this arresting process is still subject to play. The second portion, the wedging portion, takes hold when the bar enters further. A change in the arresting action takes place. The power which is introduced into the stator is diverted following the change of power transmission from the advance power transmission portion to the wedging portion. One of the advantageous aspects of the power transmission change lies in the fact that an advance power transmission portion which initially exhibits substantial play ensures that the rotor is securely caught in position relative to the stator at high rotational speeds. The rotor is firstly braked relative to the stator. The wedging portion takes over the power transmission function in the course of the arresting process. Play is minimized by the wedging action. It is hardly possible for further rattling noises to occur. Few transverse forces occur on account of the low level of play during wedging. Wear is minimized. However the catching process, which is subject to play, is carried out with a large bar diameter. More material is available during the catching process. 
     It is advantageous to dispose the arresting unit horizontally relative to the driving shaft. However the principle of the invention can also be applied to a vertical arresting unit which is disposed perpendicularly to the driving shaft. 
     According to an advantageous aspect of the invention, the wedging counterpiece for the wedging portion may be formed from a mandrel which points in the direction of propulsion, the direction of movement into the locking position, contrary to the bar. The reversal of direction between the wedging counterpiece and the bar results in a saving in construction space, and the housing or cover can therefore be of a thinner design. The shortest construction space is achieved if the mandrel and the longitudinal axis of the bar lie on one and the same axis. 
     The actual mandrel may be circular overall. It may have a frustoconical partial contour. It may consist of straight portions in part. The important factor is to provide a sufficient wedging face. A combination of a circular portion and a straight portion is favourable in the case in which an additional underflow face is to be offered for the bar in order that the bar can be pushed back into its non-arrested position against the biasing means via a hydraulic medium. 
     The dual functionality of the same bar regions can also be characterized in that the two diameters, the diameter for the advance power transmission portion and the diameter for the wedging portion, lie in one and the same plane of the bar. 
     The wedging portion has a contour such that the wedging effect is derived through surface contact. Frustoconical portion contours are particularly suitable, as the contours are easy to produce in terms of manufacturing engineering. The corresponding receiving opening is designed such that it fits together with the contour of the wedging portion by means of a positive engagement. 
     Considered from the outside, the bar may have the shape of a cylindrical rod which has a frustoconical diameter in the region of the wedging portion. In this case the first diameter is a diameter of a circular plane and the second diameter is the diameter of a cone frustum. 
     Because the camshaft adjuster is to be easily lockable and also easily unlockable, the bar is provided with pressure faces under which a hydraulic medium can easily flow. By means of appropriate duct structures and the provision of further bearing faces or pressure faces such as, for example, a circumferential collar, the pressure faces can be widened against the biasing force in order to apply the required counterforce against the biasing spring with a lower pressure. The circumferential collar is dimensioned in terms of its width such that it simultaneously assumes a guide function for the mobile pin. In a sectional representation the bar has the appearance of a cap with an increased tip. The cap shape forms a central opening which can serve as a receiving space for the biasing means. The material saving which is achieved makes the bar as a whole lighter, and it can therefore be moved and displaced by a smaller force, both the biasing force and the restoring force. The action of the biasing means on the plate creates a stationary position for the biasing means. 
     The arresting unit may comprise further ducts in order that a hydraulic medium may flow under further faces, for example at the receiving opening. One variant consists, for example, in the mandrel of the receiving space being of a smaller height than the space which is enclosed by the wedging portion. The hollow space which is formed from this is intended for a hydraulic medium. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more easily understood with reference to the figures, wherein 
         FIG. 1  is a section through a camshaft adjuster according to the invention with indicated camshaft, 
         FIG. 2  is a plan view with a sectional marking for  FIG. 1 , 
         FIG. 3  represents a partly sectional camshaft adjuster along the section BB of  FIG. 1 , 
         FIG. 4  represents a partly sectional camshaft adjuster along the section CC of  FIG. 1 , 
         FIGS. 5 ,  6  and  7  represent different views of a first embodiment of a camshaft adjuster according to the invention with arresting unit, 
         FIG. 8  represents a further embodiment of a camshaft adjuster according to the invention with arresting unit, 
       and  FIG. 9  represents a third embodiment of an arresting unit according to the invention of a camshaft adjuster. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 2  is a plan view onto one side of a camshaft adjuster which is outlined in  FIG. 1  with indicated camshaft. Further sections can be seen in  FIG. 3  and  FIG. 4 . The camshaft adjuster  1  is engaged with a shaft  15 , on which a cam  17  is represented.  FIG. 1  shows that the camshaft adjuster can be connected both by a connecting screw  25  and by a non-positive engagement between the shaft  15  and the sprocket wheel  23 . The cover  21  of a camshaft adjuster  1  is held together by fastening means such as clamping screws  27 . The housing  19  and the cover  21  close off hollow spaces which are represented as hydraulic chambers  11  and  13  in  FIGS. 3 and 4 . The chambers  11 ,  13  can be supplied with a hydraulic medium through oil ducts  31 . The clamping screws  27  pass through screw guides  29  which are provided in the stator  3  of the camshaft adjuster  1 . The screw guides  29  of the stator  3  may advantageously lie in webs  5 . The rotor  7 , which may have one or more blade(s)  9 , is located in the stator  3 . According to  FIG. 3  and  FIG. 4 , an arresting unit  50  with a bar  56  may lie in a blade  9 . In the locked position the bar  56  enters the receiving opening  58 , which may be provided in the housing  19 . The locked position is a first-stage position resulting from a biasing means  54  pressing onto the bar  56 , supported against the plate  52 , and thus pushing a part of the bar  60  into the receiving opening  58  with a biasing force. 
       FIGS. 5 ,  6  and  7 , which represent a bar  100  and a receiving opening  116  under a cover  21 , are to be referred to for an easier understanding of an appropriate embodiment. The bar  100  has a hollow-drilled shape through which a central opening  134  is formed. The helical spring  136  lies in the central opening  134 . The arresting unit  148  is composed of many components, including the bar  100 , the helical spring  136 , the plate  52  and the receiving opening  116 . The actual bar  100  can be divided into a plurality of portions and regions, a first portion  104 , a second portion  110 , one end  128  of the bar, a collar  130  and a tip  140 . The tip  140  is circular such that a space of the wedging portion  142  at one end of the bar is formed as a hollow space. The receiving opening  116  has a particular contour which forms a mandrel  118  having a circular portion  120  and a straight portion  124 . The circular portion  120  may be shaped as a frustoconical partial contour  122 . The straight portion  124  of the mandrel  118  of the receiving opening  116 , together with a part of the second portion  110  of the bar  100 , forms an oil duct which opens into the underflow duct  132  communicating with a hydraulic chamber  11  or  13 . A positive engagement is formed by means of the frustoconical partial contour  122  together with the second portion  110  of the bar  100  when the arresting unit  148  is in the locked state. The first portion  104  of the bar has a first diameter  106 , which lets the bar  100  enter the receiving opening  116  with the diameter  114 . The bar can be cut at the plane F which is set back, the mandrel depth, for example, which can be determined as the plane  126  of the bar. If the first diameter  106  and the second diameter  112  of the second portion  110  of the bar  100  are compared with one another in this plane  126 , the first diameter  106  is larger than the second diameter  112 . The part  102  of the bar which lies in the receiving opening  116  performs the locking function. A collar  130  extends around the end  128  of the bar  100  and is supported at a wall of the arresting unit or at a hole wall of the blade  9 .  FIG. 7  is a plan view onto or a partial section through the tip  140  of the bar  100 . It can be seen that the wall thickness  138  of the tip  140  of the bar  100  is determined by the two diameters  106  and  112 . Only a part of the inside diameter is seated on a part of the contour of the mandrel  118 . A hollow space or a recess Y is formed where the bar  100  is not seated, in the free region, which space or recess may communicate with the underflow duct  132  in order to enable oil to push back the bar  100  against the helical spring  136  in the entire inside diameter X.  FIG. 6  shows the oil chamber which is present while the bar is seated on the mandrel. A further approach duct  144  conveys the hydraulic medium under the collar  130 . It is located in the region of the end  128  of the bar  100 . 
     Further embodiments can be seen in  FIGS. 8 and 9  of a bar  200  and  300 , respectively, according to the invention. Similar parts and components have numbering increased by 100 and 200, respectively, when compared with the constructional variant according to  FIGS. 5 ,  6  and  7 . The arresting units  248 ,  348  differ in details which are to be seen in particular in the region of the tip  240 ,  340  of the bar  200 ,  300 . The arresting units  248 ,  348  comprise plates  52 , helical springs  236 ,  336  and receiving openings  216 ,  316 . The diameters of the receiving openings  214 ,  314  are larger than the first diameters  206 ,  306  of the first portions  204 ,  304  of the bars  200 ,  300 . The two bars  200 ,  300  have similar ends  228 ,  328 . There are collars  230 ,  330 , to which approach ducts  244 ,  344  lead, in the vicinity of the ends  228 ,  328 . 
     The bar  200  according to  FIG. 8  has a part  202  in which the first portion  204  of the bar  200  with its first diameter  206  can be found. A continuation comprises the second portion  210  of the bar  200 , which has a second diameter  212 . The diameter  214  of the receiving opening  216  is larger than the first diameter  206  of the first portion  204  of the bar  200 . The receiving opening  216  passes into the arresting opening  218 . In the represented example both openings, the receiving opening  216  and the arresting opening  218 , are disposed coaxially one behind the other along the axis G. It is also conceivable, although this is not represented, for the arresting opening  218  to be disposed eccentrically relative to the receiving opening  216 . A circular portion  220  at the tip  240  of the bar  200  is disposed such that it fits into the frustoconical partial contour  220  of the arresting opening  218  such that locking between the tip  240  of the bar  200  and the surface of the arresting opening  218  can be achieved by means of a non-positive engagement. An underflow duct  232  is provided in order to release the non-positive engagement. The underflow duct  232  is supplied with pressurised hydraulic medium. The hydraulic medium passes under the bar  200  and can release it from its press fit against the helical spring  236 , which lies in the central opening  234  of the bar  200 . The action is augmented by the flow under the collar  230  via the approach duct  244 . This enables virtually the entire cross-sectional area of the bar  200  to be used hydraulically. 
     The tip  340  of the bar  300  according to  FIG. 9  differs in part from the tip  240  of the bar  200 . One end of the helical spring  336  lies in the central opening  334 , the other end of which spring lies against the plate  52 . The underflow duct  332  consists of two cross-drilled longitudinal holes which pass into one another and hydraulically connect one hydraulic chamber to the tip of the mandrel  318  in order to enable the bar  300  to be hydraulically pushed into the unlocked position with the underflow via the approach duct  344  under the collar  330 . The part  302  of the bar  300  also comprises a first portion  304  with a first diameter  306  and a second portion  310  with a second diameter  312 . The diameter  314  of the receiving opening  316  is formed such that the entire part  302  of the bar  300  can be accommodated therein. The mandrel  318 , which likewise has a circular portion  320  and a frustoconical partial contour  322 , has a mandrel depth which is greater than the mandrel depth F of the embodiment according to  FIGS. 5 ,  6  and  7 . The two diameters  306 ,  312  lie in the same plane  326  of the bar  300 . However the plane  326  lies as a whole higher than the plane  126  of the bar  100 . Looking into the space  342  of the wedging portion of the bar  300 , the tip  340  of the bar  300  is comparable with a pot or a cup, in which pot the mandrel  318  engages. The wall thickness  338  of the bar  300  is defined by means of the differences in the two diameters  306  and  312 . The wall thickness  338  may be very small, as long as the first diameter  306  of the bar  300  is dimensioned such that the first portion  304  of the bar  300  securely catches and can transmit the occurring load moment during the locking process. The wall thickness  238  of the bar  200  of  FIG. 8  is similarly dimensioned. However in this case the wall thickness  238  also predetermines the underflow face via the underflow duct  232 . 
     Although only three embodiments have been discussed in detail, it is self-evident that, according to one aspect of the invention, these also include bars of a camshaft adjuster in the case of which the presence of two different diameters enables a power transmission change from a static component to a rotating component of the camshaft adjuster to take place during the arresting and wedging process. The simultaneous presence of both diameters in one plane is of advantage. If optimum utilization of the construction space is not important, the diameters for catching and for wedging may be disposed in different planes along one longitudinal axis.