Abstract:
An internal combustion engine including a cylinder head having gas-exchange valves, at least one camshaft supported on the cylinder head, which camshaft is driven by a crankshaft to actuate corresponding gas-exchange vales on the cylinder head, and a camshaft adjuster arranged on the camshaft. The adjuster has a hydraulic pressure chamber and is configured to use hydraulic pressure to rotate position of the camshaft relative to the crankshaft to change control times of the gas-exchange valves. A feed device for hydraulic pressure is provided on the camshaft adjuster and is configured as a component separate from the cylinder head. The feed device has a ring for each camshaft, each ring having two grooves, each of the grooves being connected via associated hydraulic pressure channels in the feed device to a hydraulic pressure valve. Each ring is arranged to surround a section of the camshaft. Each surrounded section of the camshaft has two ring-shaped grooves, each of which is aligned with one of the grooves of the corresponding ring to form a pair. Each groove/ring-shaped groove pair of a ring is connected via associated hydraulic pressure channels in the camshaft to the hydraulic pressure chamber of the camshaft adjuster mounted on the camshaft.

Description:
PRIORITY CLAIM 
     This is a U.S. national stage of application No. PCT/EP00/08904, filed on Sep. 12, 2000. Priority is claimed on that application and on the following application: Country: Germany, Application No. 199 43 833.1, filed Sep. 13, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention pertains to an internal combustion engine with a cylinder head and at least one camshaft supported thereon, which shaft, driven by a crankshaft, actuates corresponding gas-exchange valves on the cylinder head. A camshaft adjuster, which uses hydraulic pressure to rotate the position of the camshaft relative to the crankshaft and thus to change the control times of the gas-exchange valves, is provided on the camshaft. A feed device for supplying hydraulic pressure to the camshaft adjuster is also provided. The invention also pertains to a feed device for supplying hydraulic medium to the camshaft adjuster of a camshaft of an internal combustion engine. The invention also pertains to a process for producing a feed device as indicated above. 
     A device for changing the control times of the gas-exchange valves of an internal combustion engine is known from DE 197-45,670 A1, where a camshaft adjuster is mounted on one end of a camshaft, which actuates the gas-exchange valves. By means of pressure medium channels provided in a housing cover, the camshaft adjuster is supplied with hydraulic pressure for rotating the position of the camshaft relative to a crankshaft, which drives the camshaft. The housing cover, however, is complicated and expensive to produce and install. 
     It is known from DE 197-47,244 A1 that ring-shaped grooves can be provided in the cylinder head at one end of a camshaft in the area where the camshaft is supported and that hydraulic medium can be supplied via these ring-shaped grooves to a camshaft adjuster mounted on the camshaft. To prevent losses in the area of the bearing of the camshaft when the hydraulic medium is tapped, a plain bearing ring is laid in a half liner of the bearing, this ring covering the half liner. This integration of the hydraulic medium supply system into the cylinder head itself makes it difficult and expensive to produce the cylinder head. In addition, because the hydraulic medium is supplied by way of the bearing liner of the bearing of the camshaft in the cylinder head, the bearing is weakened to a corresponding extent. 
     SUMMARY OF THE INVENTION 
     The present invention, therefore, is based on the task of making available an internal combustion engine, a feed device, and a process of the above-indicated type, where the disadvantages described above are overcome, so that an improved and functionally reliable camshaft adjusting function is available. 
     In an internal combustion engine of the type indicated above, it is provided in accordance with the invention that the feed device for hydraulic pressure is designed as a component separate from the cylinder head and that this device has a ring for each camshaft, each ring surrounding a certain section of the camshaft. Each ring has two grooves, and the associated surrounded section of the camshaft has two ring-shaped grooves, which are aligned with the grooves of the corresponding ring. Each groove/ring-shaped groove pair of a ring is connected via its own set of hydraulic pressure channels in the camshaft to a hydraulic pressure chamber of the camshaft adjuster mounted on this camshaft. Furthermore, each groove/ring-shaped pair of a ring is connected by its own set of hydraulic pressure channels in the feed device to a hydraulic pressure valve. 
     This has the advantage of making available a system for feeding hydraulic medium to camshaft adjusters which is both simple to produce and simple to install. 
     In a preferred embodiment, the feed device for hydraulic pressure in the separate component comprises the following integral parts: at least one hydraulic pressure connection, at least one hydraulic tank connection, at least one socket for a hydraulic pressure valve, and corresponding hydraulic pressure channels, which are designed in such a way that they connect each hydraulic pressure connection to a socket which holds a hydraulic pressure valve, each hydraulic pressure valve to a groove/ring-shaped groove pair of a ring, and each socket for a hydraulic pressure valve to a hydraulic tank connection. The socket which holds the hydraulic pressure valve can be, for example, either parallel or perpendicular to the axis of the ring. 
     Designing the hydraulic pressure valve as a 4/2-port proportional distributing valve makes it possible to provide the camshaft with the capacity to rotate to any desired intermediate position between the two end positions of the camshaft and also to provide it at the same time with a wide rotational range extending over more than, for example, 60°. 
     It is advisable to design the feed device in such a way that it can be attached to the cylinder head. 
     In a feed device of the type indicated above, it is provided according to the invention that this feed device is designed as a component separate from the cylinder head and attachable to it, and that the device has a ring for each camshaft, each ring surrounding a certain section of the camshaft. Each ring has two grooves, which are connected to hydraulic pressure channels in the feed device to a hydraulic pressure valve. 
     This offers the advantage that, with the use of ring-shaped grooves appropriately provided in the surrounded section of the camshaft and hydraulic pressure channels, a system for supplying hydraulic medium to the camshaft adjuster is provided which is simple both to produce and to install. 
     In a preferred embodiment, the separate component has the following elements as integral parts: at least one hydraulic pressure connection, at least one hydraulic tank connection, at least one socket for a hydraulic pressure valve, and corresponding hydraulic pressure channels, which are designed in such a way that they connect each hydraulic pressure connection to a socket which holds a hydraulic pressure valve, each hydraulic pressure valve to a groove/ring-shaped groove pair of a ring, and each socket for a hydraulic pressure valve to a hydraulic tank connection. The socket which holds the hydraulic pressure valve can be, for example, either parallel or perpendicular to the axis of the ring. 
     Designing the hydraulic pressure valve as a 4/2-port proportional distributing valve makes it possible to provide the camshaft with the capacity to rotate to any desired intermediate position between the two end positions of the camshaft and also to provide it at the same time with a wide rotational range extending over, for example, more than 60°. 
     To produce the feed device mentioned above, the separate component is, for example, cast as a single piece with the ring or rings and with the socket or sockets for hydraulic pressure valve or valves, and then the hydraulic pressure connection and the hydraulic pressure channels are formed in the separate component by drilling blind holes and through-holes. The ends of the blind holes and through-holes forming the various hydraulic pressure channels which are open toward the outside are then sealed off. The open ends of the through-holes are advisably sealed off by pressing in close-fitting balls, and each hydraulic pressure connection is provided with a nonreturn valve. So that a good seal is provided between the separate component and the cylinder head on which it is mounted, appropriate flange surfaces are produced on the separate component afterwards by grinding, for example, in the areas where the component will rest on the cylinder head. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional features, advantages, and advantageous embodiments of the invention can be derived from the dependent claims as well as from the following description of the invention on the basis of the attached drawings: 
     FIG. 1 is a front view of a preferred embodiment of a feed device according to the invention; 
     FIG. 2 is a rear view; 
     FIG. 3 is a side view in the direction of arrow III of FIG. 1; 
     FIG. 4 is a view from underneath in the direction of arrow IV of FIG. 1; 
     FIG. 5 is a side view in the direction of arrow V of FIG. 1; 
     FIG. 6 is a view from above in the direction of arrow VI of FIG. 1; 
     FIG. 7 is a sectional view along line A—A of FIG. 1; 
     FIG. 8 is a sectional view along line B—B of FIG. 1; 
     FIG. 9 is a sectional view along line C—C of FIG. 6; 
     FIG. 10 is a sectional view along line D—D of FIG. 5; 
     FIG. 11 is a sectional view along line E—E of FIG. 6; 
     FIG. 12 is a sectional view along line H—H of FIG. 1; 
     FIG. 13 is a sectional view along line J—J of FIG. 1; 
     FIG. 14 is a schematic, functional block diagram of a hydraulic circuit of the feed device according to the invention; 
     FIG. 15 is a schematic side view of a mounted feed device during operation; and 
     FIG. 16 is a schematic connection diagram of an automatic control system. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     So that the relationships of the individual views according to FIGS. 3-8 and  13  to each other can be understood more clearly, broken lines identified with an “x” are drawn in each of these figures for reference. The preferred embodiment of a feed device according to the invention for supplying hydraulic medium illustrated in FIGS. 1-13 on a camshaft adjuster (not shown) is designed as a separate component  10  with two rings  12 ,  13  and sockets  14 ,  15  for hydraulic pressure valves (not shown). The rings  12 ,  13  surrounded predetermined sections of the associated camshafts (not shown) and serve as transfer points for hydraulic medium to the camshaft and to the camshaft adjuster connected to the camshaft, as will be explained in greater detail below. 
     The separate component can be attached to the cylinder head (not shown) by means of screws (not shown), which pass through the holes  16 . The surfaces shown shaded or hatched in FIG. 2 form the corresponding surfaces which come into contact with the cylinder head. A bracket  18  for a slide rail (not shown) for a chain or belt drive (not shown), mounted between a crankshaft (not shown) and the camshafts surrounded by the rings  12 ,  13 , is attached to the component  10 . 
     According to the invention, the component  10  has a system of hydraulic pressure channels, which is explained in the following. After the component  16  has been produced by means of, for example, casting, this system of hydraulic pressure channels is formed in the component  10  by the introduction of corresponding blind holes and through-holes. An opening to the outside is thus necessarily produced for each blind hole and through-hole. To the extent that these openings are not required for the operation of the component  10 , they are sealed off in a pressure-tight manner by pressing balls or bolts into them. Balls  112  are shown in FIG. 15 by way of example. 
     As can be seen especially clearly in FIG. 2, the component  10  has two separate hydraulic pressure connections  20 ,  22  on the rear side, i.e., on the side facing the cylinder head, which connections receive hydraulic pressure from the cylinder head. The first hydraulic pressure connection  20 , as can be seen especially in FIG. 10, is connected by a first hydraulic pressure channel  24  to the first socket  14 , and the second hydraulic pressure connection  22 , as can be seen especially in FIGS. 7 and 10, is connected to a second hydraulic pressure channel  26  to the second socket  15 . The first hydraulic pressure channel  24 , starting from the bracket  18 , passes through the first socket  14  and arrives at the first hydraulic pressure connection  20  and is sealed off pressure-tight at the bracket end. The second hydraulic channel  26  extends laterally (from the left in FIGS. 7 and 10) through the second hydraulic pressure connection  22  and arrives at the second socket  15  and is also sealed off pressure-tight at the external hole. 
     The first socket  14 , as can be seen especially clearly in FIGS. 8,  9 , and  12 , is connected by a third hydraulic pressure channel  28 , a fourth hydraulic pressure channel  30 , a fifth hydraulic pressure channel  32 , a sixth hydraulic pressure channel  34 , and a seventh hydraulic pressure channel  36  to a first groove  38  in the first ring  12 . The first socket, furthermore, as can also be seen in FIGS. 11 and 12, is connected by an eighth hydraulic pressure channel  40  to a second groove  42  of the first ring  12 . 
     The second socket  15 , as can be seen especially in FIGS. 9,  11 ,  12 , and  13 , is connected by a ninth hydraulic pressure channel  44 , a tenth hydraulic pressure channel  46 , an eleventh hydraulic pressure channel  48 , and a twelfth hydraulic pressure channel  50  to a first groove  52  of the second ring  13 . The second socket  15 , furthermore, as can be seen especially in FIGS. 7,  11 , and  12 , is connected by a thirteenth hydraulic pressure channel  54 , a fourteenth hydraulic pressure channel  56 , and a fifteenth hydraulic pressure channel  58  to a second groove  60  of the second ring  13 . 
     In the sections surrounded by the rings  12  and  13 , the camshaft (not shown in FIGS. 1-13) has corresponding ring-shaped grooves, which are aligned with the grooves  38 ,  42  of the first ring  12  and with the grooves  52 ,  60  of the second ring  13 , respectively. These ring-shaped grooves are connected in turn to hydraulic pressure channels in the camshaft, which are connected to corresponding hydraulic pressure chambers of a camshaft adjuster mounted on this camshaft. The application of hydraulic pressure via the first grooves  38 ,  52  of the rings  12 ,  13  and via the above-mentioned hydraulic pressure channels causes the corresponding camshaft to rotate its position with respect to the crankshaft in one direction, and the application of hydraulic pressure via the second grooves  42 ,  60  of the rings  12 ,  13  and the above-mentioned hydraulic pressure channels causes the corresponding camshaft to rotate its position with respect to the crankshaft in the corresponding opposite direction. One direction loads to an “early” position; that is, the valves are actuated earlier or in advance of the movement of the crankshaft, and the corresponding other direction leads to a “late” position; that is, the valves are actuated later or trailing the movement of the crankshaft. 
     As a result of the 4/2-port proportional distributing valves provided in the sockets  14 ,  15 , it is also possible to arrive at a stable intermediate position between these two extremes, i.e., between the extreme early and the extreme late position. It is advisable for the camshaft adjuster to be locked in the extreme late position, so that this position can be maintained without the need for pressure and also so that it will not be influenced by the forces acting on the camshaft as a result of valve actuation. 
     So that the positions of the camshafts turning in the rings  12 ,  13  can be rotated, the hydraulic pressure valves mounted in the sockets  14 ,  15 , which are driven by a control unit (not shown), which will be explained below with reference to FIG. 16, apply pressure through corresponding hydraulic pressure channels proceeding away from the sockets  14 ,  15 . If, for example, the position of the camshaft turning in the first ring  12  is to be rotated in a certain direction (e.g., to an early position), then the hydraulic pressure valve mounted in the socket  14  sends pressure through the hydraulic pressure channels  28 ,  30 ,  32 ,  34 , and  36  (see FIGS. 8 and 9, in this sequence). This pressure is then conducted onwards via the first groove  38  in the first ring  12  to the camshaft and thus to a corresponding hydraulic pressure chamber of the camshaft adjuster. If the position of the camshaft turning in the first ring  12  is to be rotated in the other direction (e.g., to a late position), then the hydraulic pressure valve mounted in the socket  14  applies pressure to the hydraulic pressure channel  40  (see FIGS.  11  and  12 ), which pressure is then sent on via the second groove  42  in the first ring  12  to the camshaft and thus to the corresponding hydraulic pressure chamber of the camshaft adjuster. If an intermediate position between early and late is to be produced, the hydraulic pressure valve mounted in the socket  14  applies pressure to both the hydraulic pressure channels  28 ,  30 ,  32 ,  34 ,  36  and to the hydraulic pressure channel  40  and automatically regulates the two pressures in such a way that the desired positional rotation or adjustment of the camshaft results. 
     If the camshaft rotating in the second ring  13  is to be rotated in a certain direction (e.g., to an early position), the hydraulic pressure valve mounted in the socket  15  applies pressure to the hydraulic pressure channels  44 ,  46 ,  48 , and  50  (compare FIGS. 13 and 9, in this sequence), and this pressure is then transmitted via the first groove  52  in the second ring  13  to the camshaft and thus to a corresponding hydraulic pressure chamber of the camshaft adjuster. If the position of the camshaft turning in the second ring  13  is to be rotated in the other direction (e.g., to a late position), the hydraulic pressure valve in socket  15  applies pressure to the hydraulic pressure channels  54 ,  56 ,  58  (see FIGS. 7 and 11, in this sequence), which is then transmitted via the second groove  60  in the second ring  13  to the camshaft and thus to the corresponding hydraulic pressure chamber of the camshaft adjuster. If an intermediate position between the early and late positions is to be produced, the hydraulic pressure valve in the socket  15  applies pressure both to the hydraulic pressure channels  44 ,  46 ,  48 , and  50  and to the hydraulic pressure channels  54 ,  56 ,  58  and regulates the two pressures in such a way that the desired positional rotation or adjustment of the camshaft results. 
     FIG. 14 illustrates schematically the hydraulic pressure circuit provided in the separate component  10  according to the invention with the hydraulic pressure connections  20 ,  22  of the hydraulic pressure valves  62 ,  64 , where each hydraulic pressure connection  20 ,  22  has a nonreturn valve  66 ,  68  and is connected to a hydraulic pump  70 . The hydraulic pressure valves  62 ,  64  are designed either as 4/2-port S/W distributing valves or as 4/2-port proportional distributing valves. Each hydraulic pressure valve  62 ,  64  is also connected to a hydraulic tank connection  72 . 
     FIG. 15 illustrates the function of the hydraulic pressure valves  62 ,  64  and the function of the combined effect of component  10 , of the camshaft  74 , and of the camshaft adjuster  76 . This diagram of FIG. 15 is to understood only in schematic terms and does not show the exact spatial relationships of the hydraulic pressure valves  62 ,  64 , as would be in FIGS. 1-13 after the hydraulic pressure valves have been inserted into the sockets  14 ,  15 . The arrangement of the hydraulic pressure channels does not completely correspond to that according to FIGS. 1-13 either. The hydraulic pressure valve  64  is mounted in the socket  15  of the component  10 ; this valve has a piston  78 . This piston  78 , depending on its position, connects a hydraulic pressure feed across the socket  15  via the hydraulic pressure connection  22  and hydraulic pressure channel  24  either to the hydraulic pressure channels  44 ,  46 , and  48  or to the hydraulic channel  56 . In addition, the hydraulic pressure valve  64  has the hydraulic tank connection  72 . The camshaft  74 , which is connected by means of a screw  80  to the component  10  and to the camshaft adjuster  76 , has two ring-shaped grooves  82 ,  84 . Inside the ring  13 , which extends completely around a section of the camshaft  74 , the first ring-shaped groove  82  is in fluid-conducting connection with the hydraulic pressure channel  48 , whereas the second ring-shaped groove  84  is connected to the hydraulic pressure channel  56 . The grooves  52 ,  60  of the second ring  13  are not shown in FIG.  15 . The first ring-shaped groove  82  is connected via a hydraulic pressure channel  86 , which is formed in the camshaft  74  around the screw  80 , to a first hydraulic pressure chamber  88  of the camshaft adjuster  76 . The second ring-shaped groove  84  is connected via a hydraulic pressure channel  90  to a second hydraulic pressure chamber  92 . Depending on which of the two hydraulic pressure chambers  88 ,  92  is put under pressure, the camshaft adjuster  76  turns the camshaft  74  relative to a wheel  94 , which is connected via a drive (toothed-wheel or belt drive, not shown) to a crankshaft (not shown), in one or the other direction. In the diagram according to FIG. 15, the system is not under pressure, and the camshaft adjuster  76  is locked by means of a bolt  96  in the late position. 
     The position of the camshaft  74  is rotated into an early position relative to the crankshaft when the second hydraulic pressure chamber  92  is put under pressure via the hydraulic pressure channels  24 ,  56 ,  84 ,  90 . The bolt  96  in this case is not engaged with the wheel  94 . In contrast, the position of the camshaft  74  is rotated back to the late position when the first hydraulic pressure chamber  66  is put under pressure via the hydraulic pressure channels  24 ,  44 ,  46 ,  48 ,  82 , and  86 . The bolt  96  not latches with the wheel  94  again, and the pressure can be released from the system. To the extent that the second hydraulic pressure chamber  92  is put under pressure via the hydraulic pressure channels  24 ,  56 ,  84 , and  90  and the first hydraulic pressure chamber  88  via the hydraulic pressure channels  24 ,  44 ,  46 ,  48 ,  82 , and  86 , the system is in the automatic control position, and an intermediate point between the extreme early and the extreme late position is automatically adjusted according to the value specified by the automatic control system. 
     FIG. 16 illustrates schematically an automatic control system of this type. A CPU  98  (Central Processing Unit) receives data from a throttle valve  100 ; from an oil temperature sensor  102 , which measures the temperature of the oil in the area of the engine oil pump  104 ; from a crankshaft sensor  106 ; and from a camshaft sensor  108 , which cooperates with a signal transmitter  110  to determine the position of the camshaft  76 . On the basis of these data, the CPU  98  actuates the hydraulic pressure valve  64  accordingly to produce the desired rotational angle of the camshaft  74  between the extreme early and the extreme later positions.