Patent Publication Number: US-2015083066-A1

Title: Camshaft phaser system

Description:
The present invention relates to a camshaft phaser system including an output drive element non-rotatably connected to a camshaft, and a control valve disposed in a central receptacle of the output drive element, the control valve extending axially into a central bore of the camshaft and being formed with at least a first operating port and a second operating port axially spaced apart therefrom. 
     BACKGROUND  
     In an internal combustion engine of a motor vehicle, the gas-exchange valves are typically operated using a camshaft drivingly connected to a crankshaft. It has proved to be advantageous to be able to control the opening and closing times of the gas-exchange valves during the operation of the internal combustion engine. By adjusting the opening and closing points as a function of, for example, the instantaneous rotational speed, it is possible, in particular, to reduce fuel consumption, to positively influence the emission performance, and to increase the efficiency of the engine. 
     The variability of the timing of the gas-exchange values is normally achieved by changing the phase relationship between the crankshaft and the camshaft. To this end, typically, a so-called camshaft phaser is integrated into the drive train via which torque is transmitted from the crankshaft to the camshaft. Modern camshaft phasers are positioned, for example, at the driven end of the camshaft or an extension thereof, on an intermediate shaft, a non-rotating component, or on the crankshaft. The camshaft phaser is typically comprised of a drive wheel which is driven by the crankshaft and which maintains a fixed phase relationship with respect thereto, an output drive element drivingly connected to the camshaft, and an in particular hydraulic positioning system which transmits the torque from the drive wheel to the output drive element. 
     The camshaft phaser is designed such that the phase relationship between the crankshaft and the camshaft is reliably maintained during operation and that, when necessary, the camshaft can be rotated relative to the crankshaft within a certain angular range. To this end, the hydraulically controllable camshaft phaser is essentially formed with at least two oppositely acting pressure chambers. By selectively connecting the pressure chambers with a pressure medium pump or a pressure medium reservoir, respectively, the phase of the camshaft relative to the crankshaft can be adjusted or maintained. 
     The supply and discharge of pressure medium to and from the pressure chambers is generally controlled by a control valve, which is usually in the form of a multi-way slide valve and typically includes, as essential components, a control sleeve and a control piston which is axially movably received in the control sleeve and is actuated by an actuator, typically an electromagnet. Moreover, the control valve has, in particular, a pressure medium port, a discharge port, as well as operating ports via which the pressure medium may be introduced into or discharged from a pressure chamber. 
     Depending on the position of the control piston, one of the pressure chambers is, for example, connected to the supply port via one of the operating ports and is filled with pressure medium. 
     At the same time, the oppositely acting pressure chamber communicates, via the operating port associated therewith, with the discharge port on the control valve and is emptied in the process. 
     In a conventional design, such a control valve is configured, for example, as a so-called central valve, which is inserted into a central receptacle formed in the camshaft phaser as a central bore and is screwed to the camshaft. 
     A camshaft phaser system of the type mentioned at the outset is disclosed, for example, in German Patent Application DE 10 2005 481 A1. There, the positioning system designed as a camshaft phaser essentially includes a drive wheel, a stator, and an output drive element arranged concentrically therewith. The output drive element is comprised of a wheel hub having five vanes formed on its outer periphery. The vanes extend radially outwardly and, together with the stator, form pressure chambers. In particular, the output drive element is non-rotatably connected to the camshaft by a central screw. 
     Positioned within the central screw is a control valve which, together with the central screw, is disposed in a bore of the output drive element, which serves as a central receptacle. The central screw and the control valve extend axially into a central bore formed in the camshaft as a receptacle. An externally threaded portion of the central screw is threadedly engaged with an internal thread in the central bore. The control valve is provided with two operating ports which are formed as radial openings in the cylindrical peripheral surface of the central screw and axially located in the output drive element. Thus, the central screw, together with the control valve, extends axially beyond the output drive element, as a result of which the camshaft phaser system requires a certain axial space. The operating ports communicate with annular channels which are formed on the central receptacle of the output drive element and which, in turn, communicate with the pressure chambers via pressure medium conduits. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a camshaft phaser system that is improved in terms of the axial space required. 
     The present invention provides a camshaft phaser system including an output drive element non-rotatably connected to a camshaft, and a control valve disposed in a central receptacle of the output drive element, the control valve extending axially into a central bore of the camshaft and being formed with at least a first operating port and a second operating port axially spaced apart therefrom. The control valve is axially disposed such that the first operating port is axially positioned in the camshaft. 
     The present invention is based on the realization that, due to cost and space considerations, in automotive applications in particular, components and assemblies should be configured and arranged to require minimum space. The modifications required to achieve smaller dimensions should be implementable in the simplest and most economical way possible, in particular in a mass production environment. In a further step, the present invention contemplates that the design and configuration of the control valve should preferably not be altered for reasons of cost. 
     Therefore, the present invention proposes to reduce the axial space required for the camshaft phaser system by disposing the control valve in particular axially further inwardly toward the camshaft and in such a way that the first operating port is axially positioned in the camshaft. The axial space required by the camshaft phaser system can thereby be reduced in a simple manner. 
     The camshaft and, in particular, the output drive element have a common axis of rotation. The output drive element may, for example, be a rotor or a hub of a camshaft phaser. 
     The two operating ports are, in particular, axially spaced-apart radial bores in the control valve. The first operating port is located further axially inwardly than the second operating port. 
     The operating ports each open into a respective annular channel formed on the central receptacle of the output drive element and on the central bore of the camshaft, respectively. The first operating port and a first annular groove together form a first fluid channel, and the second operating port and a second annular groove together form a second fluid channel. 
     The design according to the present invention has the advantage that it improves the camshaft phaser system in terms of the axial space required. Because the control valve is axially disposed such that the first operating port is axially positioned in the camshaft, the axial dimensions of the camshaft phaser system are reduced. 
     In an advantageous embodiment, the camshaft has a first annular groove in the region of the first operating port. Thus, the first operating port opens directly into the first annular groove. In particular, the first annular groove is formed in the central bore of the camshaft at the end face facing the output drive element. The first annular groove may in particular be an annular circular recess at the end face, so that the diameter of the central bore of the camshaft is enlarged in the region of the first recess. The first annular groove extends axially at least in such a way that the first operating port is at least partially cleared by the first annular groove. 
     In accordance with the present invention, the axial arrangement of the control valve such that the first operating port is axially located in the camshaft can basically be achieved by disposing the control valve axially further into the central receptacle of the output drive element, and thus also further into the corresponding central bore of the camshaft, whereby in particular the axial extent of the output drive element can be reduced. 
     In an advantageous embodiment, the control valve is disposed within a central screw, the radially outer peripheral surface of the central screw having formed thereon a radially outwardly extending shoulder, this shoulder being located within a recess formed in the end face of the output drive element and bearing axially against the output drive element. In the region of the operating ports, the central screw has radial bores which, together with the annular channels, each form a respective fluid channel. The first recess is an in particular annular circular recess located centrally at the end face of the output drive element that faces away from camshaft. This easy-to-form recess of the output drive element allows the central screw, and thus also the control valve, to be positioned axially further inwardly in a simple manner and such that the first operating port of the control valve is located in the camshaft. 
     Advantageously, the output drive element has a number of first bores extending angularly from radially outward to radially inward toward the camshaft for connection of the first operating port to a pressure chamber. These angularly extending first bores provide a simple connection between the first operating port located within the camshaft and the corresponding pressure chamber without having to provide additional special components that are complex to manufacture, and without having to modify the design of the control valve. 
     Advantageously, at the end facing the camshaft, the first bores each open into a respective axial connection opening which is fluidically connected to the first annular groove. Due to the axial connection opening, the boundary edge between the axial end face and the inner peripheral surface of the output drive element is removed, and in particular such that a bevel is formed in the region of the first bore. This axial connection opening promotes in particular the passage of pressure medium. 
     The control valve advantageously has a control port for controlling a locking device, the output drive element having a number of second bores extending angularly from radially inward to radially outward toward the camshaft for connection of the control port to the locking device. The locking device may in particular serve to non-rotatably couple the output drive element to an input drive element during certain operating phases in order to prevent uncontrolled vibrations, which could lead, for example, to noise emissions and increased wear. Such coupling may be released by acting on the locking device with pressure medium. 
     In the case that the control valve is disposed within a central screw, the output drive element preferably has a bevel located between the radially inner peripheral surface of the output drive element and the radially extending end face thereof that is created by the recess. This bevel forms a channel between the radially outer peripheral surface of the central screw and its radial shoulder and the output drive element, this channel communicating with the second bores and the control port. Moreover, preferably a concave recess is formed circumferentially along a boundary line between the radially outer peripheral surface of the central screw and the face of the central screw&#39;s radial shoulder that faces the camshaft. This recess, together with the control port, the bevel and a respective one of the second bores, forms a channel for the pressure medium. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention are described in more detail below with reference to the drawing, in which: 
         FIG. 1  shows a cross section of a camshaft phaser system; 
         FIG. 2  shows an output drive element of the camshaft phaser system of  FIG. 1 ; 
         FIG. 3  shows a cross section of an alternative embodiment of a camshaft phaser system; and 
         FIG. 4  shows an output drive element of the camshaft phaser system of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , a camshaft phaser system  2  is shown in a cross-sectional view. Camshaft phaser system  2  includes a hydraulic camshaft phaser  6  of an internal combustion engine (not specifically shown), the hydraulic camshaft phaser being mounted to an end face of a camshaft  4  at a free end thereof. The rotatably mounted camshaft  4  is provided with cams for operating gas-exchange valves of the internal combustion engine (not shown). Camshaft phaser  6  serves to alter a relative phase angle between a crankshaft (not shown) and camshaft  4 . 
     Camshaft phaser  6  includes an output drive element  8  configured as a rotor. A central screw  12  is disposed in a central receptacle  10  of output drive element  8 . Output drive element  8  is non-rotatably attached to the end face of camshaft  4  by a central screw  12  screwed into a central bore  14  of camshaft  4 . 
     A control valve  15  for controlling the flows of pressure medium in camshaft phaser  6  is disposed within central screw  12 , the control valve  15  being able to receive a pressurized medium, such as, for example, oil, from a pressure medium feed line P of a hydraulic system. Control valve  15  essentially includes a casing  16  made of a plastic material, and a hollow cylindrical control sleeve  18  disposed therein. A control piston  20  is axially movably disposed in the control sleeve. In addition, control valve  15  has a first operating port  22  and a second operating port  24 , which are communicatingly connected to oppositely acting pressure chambers of camshaft phaser  6 . 
     Control valve  15  is axially disposed such that first operating port  22  is axially positioned in camshaft  4 . To this end, output drive element  8  has recess  26  at the end face thereof, and a radially outwardly extending shoulder  28  formed on the radially outer peripheral surface of central screw  12  bears axially against output drive element  8 . The easy-to-form recess  26  of output drive element  8  allows central screw  12 , and thus also control valve  15 , to be positioned axially further inwardly and in such a way that first operating port  22  of control valve  15  is axially located in camshaft  4 . The axial dimension of camshaft phaser system  2 , and thus the axial space required by it, are thereby reduced in a simple manner. 
     A first annular groove  30  is formed in the radially inner peripheral surface of camshaft  4 , and a second annular groove  32  is formed in the radially inner peripheral surface of output drive element  8 . First annular groove  30  is an annular circular recess at the end face, so that the diameter of central bore  14  of camshaft  4  is enlarged in the region of this recess, and first annular groove  30  is axially open toward output drive element  8 . The two annular grooves  30 ,  32  are each axially disposed in such a way that operating ports  22 ,  24  open into the respective annular grooves  30 ,  32  via radial bores in central screw  12 . 
     In order to connect first operating port  22  further to the corresponding pressure chamber  33 , output drive element  8  has, as a pressure medium conduit, a number of first bores  38  extending angularly from radially outward to radially inward toward camshaft  4  for connection of first operating port  22  to a pressure chamber  33 . These angularly extending first bores  38  provide a simple connection between the first operating port  22  located within camshaft  4  and the corresponding pressure chamber  33  without having to provide additional special components that are complex to manufacture, and without having to modify the design of control valve  15 . 
     At the end facing camshaft  4 , first bores  38  each open into a respective axial connection opening  40  which is fluidically connected to first annular groove  30 . Due to the axial connection opening  40 , the boundary edge between the axial end face and the inner peripheral surface of output drive element  8  is removed such that a bevel is formed in the region of first bore  38 . This axial connection opening  40  promotes in particular the passage of pressure medium. 
       FIG. 2  illustrates an output drive element  8  of the camshaft phaser system  2  of  FIG. 1 . Visible here is the central receptacle  10 , which serves in particular to receive control valve  15 . Also shown are four angularly extending first bores  38 , which are circumferentially spaced apart from each other and serve as pressure medium conduits to connect a first operating port  22  to a corresponding pressure chamber  33 . Also visible are the respective axial connection openings  40 , into which open the respective first bores  38 . 
       FIG. 3  shows an alternative embodiment of a camshaft phaser system  2  in a cross-sectional view. The camshaft phaser system  2  shown here is substantially similar to that shown in  FIG. 1 . 
     In contrast to the latter, the control valve  15  inserted in central screw  12  additionally has, in particular, a control port  42  for controlling a locking device, the control port opening into an oblique bore  44  in the central screw. The locking device (not shown) serves, in particular, to non-rotatably couple output drive element  8  to an input drive element during certain operating phases in order to prevent uncontrolled vibrations, which could lead, for example, to noise emissions and increased wear. Such coupling may be released by acting on the locking device with pressure medium. Control valve  15  is axially disposed such that a first operating port is axially positioned in camshaft  4 , whereby the axial space required by camshaft phaser system  2  is reduced. 
     Output drive element  8  has a number of second bores  46  extending angularly from radially inward to radially outward toward camshaft  4  for connection of the control port  42  to the locking device. In addition, a circumferential bevel  48  is formed between the radially inner peripheral surface of output drive element  8  and the radially extending end face thereof that is created by recess  26 . This bevel  48  forms a channel between the radially outer peripheral surface of central screw  12  and its radial shoulder  28  and output drive element  8 , this channel communicating with second bores  46  and control port  42 . Moreover, a concave recess  50  is formed circumferentially along a boundary line between the radially outer peripheral surface of central screw  12  and the face of the radial shoulder  28  of central screw  12  that faces camshaft  4 . This recess  50 , together with control port  42 , bevel  48  and a respective one of the second bores  46 , forms a channel for the pressure medium for controlling the locking device. 
       FIG. 4  shows an output drive element  8  of the camshaft phaser system  2  of  FIG. 3 . Visible here is the central receptacle  10 , which serves in particular to receive control valve  15 . There are also shown two angularly extending second bores  46 , which are circumferentially spaced apart from each other and serve as pressure medium conduits to connect a control port  42  to a locking device. Also shown is the bevel  48 , which serves to create a channel between the radially outer peripheral surface of a central screw  12  and its radial shoulder  28  and output drive element  8 , and which communicates with second bore  46  and control port  42 . 
     LIST OF REFERENCE NUMERALS 
       2  camshaft phaser system 
       4  camshaft 
       6  camshaft phaser 
       8  output drive element 
       10  receptacle 
       12  central screw 
       14  central bore 
       15  control valve 
       16  casing 
       18  control sleeve 
       20  control piston 
       22  first operating port 
       24  second operating port 
       26  recess 
       28  shoulder 
       30  first annular groove 
       32  second annular groove 
       33  pressure chamber 
       34  radial bore 
       36  axis of rotation 
       38  first bores 
       40  axial connection opening 
       42  control port 
       44  oblique bore 
       46  second bores 
       48  bevel 
       50  recess 
     P pressure medium feed line