EP0254058A2 - Camshaft for controlling the gas inlet and exhaust valves of an internal-combustion engine - Google Patents

Abstract

In an internal-combustion engine, in order to be able to vary the control times for opening and closing the gas inlet and outlet valves, the camshaft controlling the valves is constructed of two assemblies moving with respect to one another. A first assembly, supported on the internal-combustion engine, consists of a hollow outer shaft (1) with a first half of the control cams (5), for only the gas inlet or outlet valves, fixed thereto. The second assembly is an inner shaft (3), supported concentrically in the outer shaft (1), on which is mounted the second half of the control cams (4) via pins (7) protruding through radial slots in the outer shaft (1). The control cams (4) connected fixedly to the inner shaft (3) are supported on the outer shaft (1) such that they can rotate. By means of an adjusting device (10) integrated into the drive wheel (gear wheel 13), the angular position between the two halves of the control cams (4, 5) can be continuously adjusted over a predetermined range. The adjusting device (10) may be operated hydraulically or by means of an electrical stepping motor. The control signals for the adjusting device (10) are derived from selected engine operating data and namely, in particular, the air induction flow rate. <IMAGE>

Description

The invention relates to an adjusting device for a camshaft for controlling the gas intake and exhaust valves of internal combustion engines with variable control times for opening and closing the valves.

A positionally adjustable camshaft is known from the publication entitled "Variable valve control from Fiat" by Andrea Titolo in the magazine MTZ 47 (1986) No. 5, pages 185-188, with which the timing for opening and closing the valves can be changed are. With this camshaft, the control times are changed by axial displacement, whereby the individual control cams must have a conical outer jacket. In order to be able to transmit the control forces from these conical control cams to the valve tappets, sliding pieces designed as rockers must be used between the tappet and control cams. The use of such sliders results in a complicated and wear-prone connection between the control cam and valve tappet. In addition, the axial displacement of the camshaft requires a complicated adjustment mechanism.

Proceeding from this, the object of the invention is to change the control times of the gas inlet and outlet valves by a different design to achieve a camshaft also provided with a different adjustment mechanism.

This object is achieved by a camshaft designed according to the characterizing features of patent claim 1.

In the case of the camshaft actuated by the adjusting device according to the invention, the camshaft construction principle according to DE-OS 32 27 693 is used. In that publication, a camshaft is already described in which the individual cams are mounted on a finished hollow shaft and held in a shrink fit.

Appropriate embodiments of the adjusting device according to the invention are the subject of the subclaims. These individual embodiments will be discussed in more detail in the description of the embodiment.

Common to all of the embodiments, however, is that the angular position of the control cams controlling the exhaust valves on the one hand and the intake valves on the other hand can be changed in a simple manner relative to one another. The change can be achieved on the one hand by the fact that the angular position can be set to different values when the motor is at rest, or by the fact that the adjusting device is part of a control circuit by which the angular position between the control cams which are movable relative to one another depends on the prevailing motor operating data certain specifiable values is regulated.

• Fig. 1 einen Schnitt durch eine Nocken­welle mit einer Verstellein­richtung
• Fig. 2 einen Schnitt durch die Nocken­welle nach Linie II - II in Fig. 1
• Fig. 3 einen Schnitt durch die Nocken­welle nach Linie III - III in Fig. 1
• Fig. 4 einen Schnitt durch die Nocken­welle nach Linie IV - IV in Fig. 1
• Fig. 5 einen Schnitt durch eine alter­native Verstelleinrichtung
• Fig. 6 einen Schnitt durch eine weitere Variante einer Verstelleinrichtung
• Fig. 7 einen Schnitt durch noch eine weitere Ausführungsform der Verstelleinrichtung
• Fig. 8 eine Ansicht nach Pfeil VIII in Fig. 7 auf nur einen Ausschnitt aus dem mit der äußeren Welle verbundenen Flansch
• Fig. 9 eine Ansicht nach dem Pfeil IX in Fig. 7 auf einen Ausschnitt nur der mit der inneren Welle verbundenen Scheibe

An embodiment is shown in the drawing. Show it

• Fig. 1 shows a section through a camshaft with an adjusting device
• 2 shows a section through the camshaft according to line II - II in FIG. 1
• 3 shows a section through the camshaft according to line III-III in FIG. 1
• 4 shows a section through the camshaft according to line IV-IV in FIG. 1
• Fig. 5 shows a section through an alternative adjusting device
• Fig. 6 shows a section through a further variant of an adjusting device
• Fig. 7 shows a section through yet another embodiment of the adjusting device
• Fig. 8 is a view according to arrow VIII in Fig. 7 on only a section of the flange connected to the outer shaft
• Fig. 9 is a view according to the arrow IX in Fig. 7 on a section of only the disc connected to the inner shaft

The camshaft consists of a hollow outer shaft 1 and a hollow inner shaft 3 mounted therein via bearings 2. Control cams 5 for either the intake or exhaust valves are shrunk on the outer shaft 1. The control cams 4 for the intake and exhaust valves, which are not actuated by the control cams 5, are rotatably mounted on the outer shaft 1 and are fixedly connected to the inner shaft 3 via a pin 7 projecting through a slot 6 in the outer shaft. Radial bores 8 and 9 are provided in the outer shaft 1 for lubricating the bearings 2 in the annular space between the outer shaft 1 and the inner shaft 3. The bores 9 each lie in areas in which the camshaft is supported via the outer shaft 1 on the internal combustion engine, of which it is a component, and serve to admit lubricating oil into the annular space. Through the holes 8, which are outside the bearing areas, the lubricating oil can leave the annular space again.

At one end of the camshaft, an adjusting device 10 is provided with which the outer and inner shafts 1, 3 can be rotated relative to one another.

In the embodiment according to FIGS. 1 and 2, the adjustment device is constructed as follows:

A flange 11 is firmly attached to the end of the outer shaft. The inner shaft 3 projects beyond the end of the outer shaft and the flange 11 connected to it. In the end region of the inner shaft 3 is on this rotatably applied a disc 12 which is axially spaced from the flange 11. An externally toothed gear 13 is rotatably mounted on the inner shaft between the flange 11 and the disk 12. About this gear 13, the camshaft is driven by the crankshaft by means of a toothed belt. In the gear 13 three slots 14 are provided in the same circumference on the same circumference. Through these slots 14 engage bolts 15 through which the flange 11 and the washer 12 are non-rotatably connected. The gear 13 serves as a planet carrier for planet gears 16 of a planetary gear. The planet gears 16, which are mounted on bearing journals 17 in the gear 13, are located axially between the gear 13 and the disk 12. The planet gears 16 are driven by a sun gear 18, which is fixedly connected to the inner shaft 3. Radially on the outside, the planetary gears 16 mesh in a ring gear 19 fixedly connected to the disk 12. The flange 11, the gear 13 and the disk 12 can be non-positively connected to the ring 20 via a nut 20 engaging the end of the inner shaft 3. Given by the tightened nut 20 a positive connection of the aforementioned parts, the toothed belt coming from the crankshaft drives the camshaft via the gearwheel 13, specifically the outer and inner shafts 1, 3 with a rigid connection to one another.

In order to change the circumferential angular position of the control cams 5 which are fixedly connected to the outer shaft 1 in relation to the control cams 4 which are fixedly mounted on the inner shaft 3, the adjusting device 10 is as follows to operate.

With the gear 13 locked in its circumferential position, the nut 20 is loosened when the inner shaft 3 is also locked in the circumferential direction, so that the non-positive connection between the disk 12 with the ring gear 19, the gear 13 and the flange 11 is canceled. With the circumferential position of the gear 13 still locked, the inner shaft 3 is rotated. In order to be able to turn or lock the inner shaft 3 in the circumferential direction, it is provided at its end with a gripping cam 21 for attaching a tool key.

By rotating the inner shaft 3 with the gear 13 locked at the same time, the sun gear 18, which is fixedly connected to the inner shaft 3, causes the planetary gears 16 to rotate, which in turn, via the ring gear 19, rotate the disk 12, which is firmly connected to the ring gear 19. With the disk 12, however, the flange 11 fixedly attached to the outer shaft 1 is non-rotatably connected. The outer shaft is thus rotated to the same extent as the disk 12.

The choice of the transmission ratio in the planetary gear can determine to what extent the outer shaft is rotated in the opposite direction when the inner shaft is rotated in one direction. The gear ratio can be set so that the inner and outer shafts 3, 1 are adjusted by the same angle of rotation in opposite directions. After mutual twisting of the inside and outside shaft 3, 1, the nut 20 is again tightened with the locked inner shaft 3 and locked gear 13 to produce a non-positive connection between the parts 11, 13 and 12.

At the end opposite the adjusting device 10, the inner shaft 3 is secured against sliding into the outer shaft 1 via an annular disk 22 screwed to it.

In one embodiment of the adjusting device 10 according to FIG. 5, it is possible to change the angular position of the control cams 4 and 5 during the operation of the internal combustion engine. For this purpose, an electric stepper motor 23 is flanged to the disk 12. The output shaft 24 of this stepper motor is rigidly connected to the inner shaft 3 of the camshaft. If the angular position between the control cams 4 and 5 is to remain unchanged during motor operation, the stepper motor is controlled electrically so that it alternately exerts control pulses which rotate in opposite directions on the inner shaft 3, with the result that, with a sufficiently high pulse frequency, practically a rigid connection between the outer and inner shaft 1, 3 is given. To change the angular position, the stepper motor 23 only has to be controlled so that the output shaft 24 is rotated. The planetary gear, which corresponds to that of the adjusting device according to FIGS. 1 and 2, can be used to determine the extent to which the control cams 4, 5 are rotated relative to one another by the fixed transmission ratio. The translation ver Ratio in particular be chosen such that both types of control cams are adjusted by the same amount in opposite directions. The control current for the stepper motor is fed to it via sliding contacts. The stepper motor can be controlled via parameters dependent on specific motor operating states, as a result of which certain angular positions of the control cams 4, 5 can be set or regulated in relation to specific motor operating conditions.

A change in the angular position of the control cams 4, 5 depending on the engine operation is also possible with the adjusting devices to be described below.

6 corresponds to that of the embodiments according to FIGS. 1 and 2 and 5. Only the adjustment motor and its articulation to the adjustment device differ from the embodiment according to FIG. 5.

6, a hydraulic motor 25 fixedly attached to the internal combustion engine is used. In a plunger 26 of the hydraulic motor 25 which is displaceable along the camshaft axis, a bolt 27 is rotatably axially fixed. This bolt 27 projects axially into the inner shaft 3, the inner shaft 3 and the bolt 27 being rotatable and displaceable relative to one another. The bolt 27 is at the same time in a flange 28 fixedly connected to the disk 12 stores in which it is longitudinally displaceable but not rotatable. The bolt 27 is secured against rotation by a tongue and groove connection 29 between the bolt 27 and the flange 28. A spindle groove 30 is formed in the bolt 27, into which a ball 31 which is fixedly mounted in the inner shaft 3 engages. Between the flange 28 and the punch 26, a compression spring 32 engages, which loads the punch 26 in the direction away from the flange 28. In the event of a longitudinal displacement of the bolt 27, the inner shaft 3 is rotated via the ball 31 sliding in the spindle groove 30. Thus, the same angular position adjustment of the control cams 4, 5 can be achieved with the hydraulic motor 25 during motor operation as with the stepper motor 23 in the adjusting device according to FIG. 5. In particular, the same control pulses can be supplied to the hydraulic motor 25 as the stepper motor.

In the adjusting device according to FIG. 7, the change in the angular position between the control cams 4, 5 is also adjustable during engine operation as a function of the engine operating data. In contrast to those described above, this embodiment does not use a planetary gear. The adjustment device according to FIG. 7 is constructed in detail as follows.

As in the previous embodiments, a flange 11 is fixedly mounted on the outer shaft 1. A disk 12 is rigidly connected to the inner shaft 3 at an axial distance from the flange 11. The rigid connection of the disk 12 to the inner shaft 3 takes place via a shaft stub 33 fixedly mounted on the end of the inner shaft 3. Between the flange 11 and the disk 12, a guide disk 34 is rotatably mounted on the stub shaft 33 and can be rotated against the flange 11 and the disk 12. An externally toothed gear 35 is fastened to the guide disk 34 by means of screws 36.

In order to be able to rotate the outer shaft 1 against the inner shaft 3, it is necessary to rotate the flange 11 and the disk 12, these parts being firmly connected to one of the two shafts, against one another. For this purpose, guide pieces 37 arranged in a radially movable manner are used in the guide disk 34. These guide pieces 37 are cylindrical bodies which can be displaced in a radial bore 38. The bores 38 are closed radially on the outside. Radially on the inside, the bores 38 can be acted upon by hydraulic oil, which enters the bores 38 from a pressure source via a ring connection 39 fixedly mounted on the internal combustion engine through the stub shaft 33, which is rotatably supported in the ring connection 39.

On the guide pieces 37 axially parallel to the camshaft drive pins are attached, which are movable in the slots provided radially in the guide disk 34 and project axially through these slots from the guide disk 34. The axially protruding ends of the driver pins 40 protrude on one side of the guide disk into a respective guide slot 41 in the flange 11 and on the other side of the guide disk 34 also into a respective guide slot 42 in the disk 12.

The guide slots 41, 42 must be in one direction run, which lies between a diametrical alignment on the one hand and an alignment in the circumferential direction on the other. This is the only way to rotate the flange 11 or the disk 12 in which they are arranged. If both shafts are not to be rotated at the same time, but rather only one shaft or one shaft is to be adjusted first and the other only subsequently, the guide slot in the flange 11 or the disk 12, in particular in the disk 12, can also be at least partially aligned diametrically.

For a radial back and forth movement of the guide pieces in engine operation, exposure to hydraulic fluid from only one side is sufficient. It is particularly advantageous to act upon the guide body hydraulically from the radial inside. The countermovement, i.e. the movement radially inward is generated automatically by the transmission system with correctly aligned guide slots 41, 42.

The aforementioned automatic return can be explained as follows.

The gear 35, by means of which the camshaft is driven by the crankshaft with the aid of a timing belt, transmits the driving forces to the flange 11 and the disk 12 via the driving pins 40. Since the camshaft is supported by the outer shaft 1, it must be carried out on the flange 11 attacking driving pins 40 are transmitted a greater driving torque than by engaging in the disc 12 Driving pins 40. The radial position which the guide pieces 37 assume from the radial inside due to the driving pins 40 and the hydraulic loading is thus determined by the guidance of the driving pin 40 in the flange 11.

A force plan entered in FIG. 8 with regard to the transmission of force in the guide slot 41 clearly shows the restoring force acting radially inwards on the guide pieces 37. In the force map, F _{U represents} the circumferential force emanating from the driver on the flange 11. Within the slot, this circumferential force is divided into two components, namely a normal force F _N acting on the slot path and a force F _S acting in the longitudinal direction of the slot. The force F _S causes the guide piece 37 to move radially inward in the direction of rotation of the flange 12 shown in FIG. 8 when there is no hydraulic counterforce. In this consideration, it has initially been disregarded that a centrifugal force counter to the force F _{S also} acts on the guide pieces 37. Frictional forces between the driver and the guideway have also been disregarded. If these opposing forces are taken into account, in order to ensure a radially inward movement of the guide pieces, only the force F _{S has to be} greater than the counter forces mentioned, which is regularly the case in practice for camshafts for internal combustion engines.

Fig. 9 shows the arrangement of the guide slot 42 in the disc 12. Taking into account the direction of rotation of the disc 12 shown in Fig. 9, it can be seen that the guide slot 42 with respect to the direction of rotation of the camshaft has an opposite inclination with respect to the guide slot 41.

If the inclinations of the guide slots 41 and 42 are exactly opposite, the control cams 4 and 5 are rotated by the same amount in opposite directions. The course and the interdependency of the timing of the cams 4 and 5 can be varied as desired by different positions and shapes of the guide slots.

The hydraulic pressure for adjusting and controlling the guide body 37 is determined by a processor on the basis of measured engine operating data. The processor emits a proportional current via a power unit, which is used to control an adjustable pressure relief valve with the aid of a proportional magnet. The pressure released by the pressure limiting valve on the hydraulic fluid then acts on the guide pieces 37. Between the ring connection 39, into which the hydraulic fluid enters via the opening 43 and the guide pieces 37, the hydraulic fluid passes through an annular channel 44 in a cap 45 attached to the stub shaft 33, a blind hole 46 in the stub shaft 33, a through hole 47 also in the stub shaft 33, a further ring channel 48 and an inlet hole 49 leading into the hole 38.

Claims (12)

1. Adjustment device for a camshaft for controlling the gas inlet and exhaust valves of internal combustion engines with variable control times for opening and closing the valves, in which the camshaft has the following features
- two shafts are rotatably mounted concentrically one inside the other,
the outer of the two shafts (outer shaft) is rotatably mounted in axially fixed bearings on the internal combustion engine,
on the axially extending outer surface, the outer shaft has control cams firmly connected to it for actuating either only the inlet or the outlet valves,
the control cams required for controlling the valves that are not actuated by the control cam that is permanently connected to the outer shaft are rotatably mounted on the outer shaft so that they can be rotated,
the outer shaft has slots in the circumferential direction, through which fitting pieces, which can be displaced in the circumferential direction over a predeterminable angle, project radially,
the adapters connect the control cams rotatably mounted on the outer shaft to the inner shaft,
The outer and inner shafts can be adjusted relative to one another via a rotation angle corresponding to the displacement path of the fitting pieces, and can be fixed in any position that can be achieved thereby,
characterized by a device for mutually rotating the two shafts with the following features: (a) a drive wheel (13) rotatably mounted on the inner or outer shaft (3, 1) can be locked circumferentially against both shafts (1, 3) as a planet carrier of a planetary gear, (b) the planet gears (16) mounted in the revolving carrier engage on the one hand with a sun gear (18) rigidly attached to a first of the two shafts (1, 3) and on the other hand with a ring gear (19) rigidly connected to the second shaft. 2. Adjusting device according to claim 1,
characterized by
that the drive wheel (13) between two non-positively attachable webs (11, 12) lies, one of which can be rigidly connected to the inner shaft and one to the outer shaft (3, 1). 3. Adjusting device according to claim 2,
characterized by
that a flange (11) rigid with the outer shaft (1) and with bolts projecting axially with play in the circumferential direction through the drive wheel (13) without rotation with a disk (12) mounted on the inner shaft (3) and carrying the ring gear (19) of the planetary gear is connected, which can be non-positively connected to the latter via a fastening means (20) acting on the inner shaft (3). 4. Adjusting device according to claim 3,
characterized by
that the fastener is a nut (20). 5. Adjusting device according to claim 3,
characterized by
that the fastening means is an electric stepper motor (23), of the gas housing with the disc (12) and the drive shaft (24) with the inner shaft (3) are rigidly connected. 6. Adjusting device according to claim 3,
characterized by a fastener with the following features: (a) a bolt (27) provided with a spindle groove 30 projects into the inner shaft (3), (b) the bolt (27) is non-rotatably but axially displaceable relative to the disk (12), (c) inner shaft (3) and bolt (27) are rotatable and longitudinally displaceable relative to one another, (d) a ball (31) fixedly mounted in the inner shaft (3) engages in the spindle groove (30) of the bolt (27), (e) the bolt (27) is axially fixed and rotatably mounted on a plunger (26) which can be displaced along the camshaft axis of a hydraulic motor fixedly attached to the internal combustion engine, (f) a compression spring (32) acts between the stamp (26) and the disk (12), (g) the axial position of the plunger (26) can be adjusted by pressurizing the hydraulic motor (25). 7. Adjusting device according to claim 5 or 6,
characterized by
that the stepper motor (23) or the plunger (26) of the hydraulic motor (25) can be controlled as a function of engine operating data, such as, in particular, the amount of intake air. 8. adjusting device according to the preamble of claim 1,
characterized by a device for mutually rotating the two shafts with the following features: (a) on the inner or outer shaft (3, 1) a drive wheel consisting of a guide disk (34) and a gear wheel (35) firmly connected to it is rotatably mounted, (b) a flange (11) rigidly mounted on the outer shaft (1) bears against a first end face of the guide disk (34) and a washer (12) rigidly connected to the inner shaft (3) on the second end face, (c) in relation to the flange (22) and the disk (12), the guide disk (34) can be rotated in a predeterminable way, (d) radially uniformly displaceable guide pieces (37) are mounted in the guide disk (34), (e) the guide pieces (37) have drivers (40) engaging in guide slots (41, 42) of the flange (11) and the disk (12), (f) the guide slots (41, 42) run in the direction lying between the diametrical and circumferential direction of the flange (11) or the disk (12), (g) the position of the guide pieces (37) is adjustable. 9. Adjusting device according to claim 8,
characterized by
that the guide pieces (37) are hydraulically adjustable stamps, a hydraulic motor being fixedly attached to the internal combustion engine being provided for the hydraulic application. 10. Adjusting device according to claim 9,
characterized by
that the guide slots (41, 42) on the flange (11) rigidly connected to the outer shaft (1) are inclined so that with respect to an imaginary connecting line between the radially outer end of the guide slot (41) with the respective center point of the flange (11 ) the radially inner end of the guide slot (41) in the flange (11) circumferential direction is in each case in front of this imaginary line and that the guide pieces (37) are only hydraulically loaded from the radial inside. 11. Adjusting device according to claim 9 or 10,
characterized by
that the guide slots (41, 42) in the flange (11) and the disc (12) are inclined differently with respect to the circumferential direction. Adjusting device according to one of claims 8-11,
characterized by
that the hydraulic motor can be controlled to act on the guide pieces (37) as a function of engine operating data, in particular the amount of intake air.

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