WO2005119017A1

WO2005119017A1 - Device for modifying control times of an internal combustion engine

Info

Publication number: WO2005119017A1
Application number: PCT/EP2005/005902
Authority: WO
Inventors: Rainer Ottersbach; Uwe Gottschlig
Original assignee: Schaeffler Kg
Priority date: 2004-06-02
Filing date: 2005-06-01
Publication date: 2005-12-15
Also published as: DE102004026865A1

Abstract

The invention relates to a device (1) which is used to modify the control times of an internal combustion engine, wherein a rotor (3) is arranged inside a stator (2). The inner cover surface of the stator (2) is provided with cavities (5) wherein wings (11) protrude. The wings are arranged in the wing grooves (10) which are introduced into the rotor (3). The cavities (5) are embodied as pressure chambers and the wings (11) separate the pressure chambers in a first and a second pressure chamber (12, 13). The rotor (3) can be displaced in relation to the stator (2) by guiding pressure means to the first and/or second pressure chamber (12, 13). According to the invention, the wings (11) are only partially hardened in the region of the loading areas.

Description

Description of the invention Device for changing the timing of an internal combustion engine

description

Field of the Invention

The invention relates to a device for changing the timing of an internal combustion engine with a stator driven by the crankshaft and a rotor driving at least one camshaft, which is driven by the stator via a hydraulic actuator, the phase position between the crankshaft and the at least one camshaft via the actuator can be changed and wherein the actuator comprises at least one pressure chamber into which a wing attached to the rotor engages, the wing separating the pressure chamber into two hydraulic pressure chambers working against each other.

In internal combustion engines, camshafts are used to actuate the gas exchange valves. Camshafts are mounted in the internal combustion engine in such a way that cams attached to them rest on cam followers, for example bucket tappets, rocker arms or rocker arms. If a camshaft is set in rotation, the cams roll on the cam followers, which in turn actuate the gas exchange valves. The position and shape of the cams thus determine both the opening duration and amplitude, but also the opening and closing times of the gas exchange valves. Modern engine concepts tend to variably design the valve train. On the one hand, the valve lift and valve opening duration should be variable, up to the complete shutdown of individual cylinders. Concepts such as switchable cam followers or electrohydraulic or electric valve actuations are provided for this. Furthermore, it has proven to be advantageous to be able to influence the opening and closing times of the gas exchange valves during operation of the internal combustion engine. It is also desirable to be able to influence the opening and closing times of the intake and exhaust valves separately, for example, in order to be able to specifically set a defined valve overlap. By setting the opening and closing times of the gas exchange valves depending on the current map area of the engine, for example on the current speed or the current load, the specific fuel consumption can be reduced, the exhaust behavior can be positively influenced, the engine efficiency, the maximum torque and the maximum output increased become.

The described variability in the gas exchange valve timing control is brought about by a relative change in the phase position of the camshaft relative to the crankshaft. The camshaft is usually connected to the crankshaft via a chain, belt, gear drive or equivalent drive concepts. Between the chain, belt or gear drive driven by the crankshaft and the camshaft there is a device for changing the timing of an internal combustion engine, hereinafter referred to as the camshaft adjuster, which transmits the torque from the crankshaft to the camshaft. This device is designed in such a way that the phase position between the crankshaft and the camshaft is held securely during operation of the internal combustion engine and, if desired, the camshaft can be rotated in a certain angular range with respect to the crankshaft.

In internal combustion engines, each with a camshaft for the intake and exhaust valves, these can be equipped with a camshaft adjuster. This allows the opening and closing times of the inlet and outlet Intake gas exchange valves are shifted in time relative to each other and the valve overlaps are set specifically.

Modern camshaft adjusters are generally located at the drive end of the camshaft. It consists of a drive wheel which is driven by the crankshafts and has a fixed phase relationship to the drive wheel, a camshaft-fixed output part and an adjusting mechanism which transmits the torque from the drive wheel to the output part. The drive wheel can be designed as a chain, belt or gearwheel and is connected to the crankshaft in a rotationally fixed manner by means of a chain, a belt or a gearwheel drive. The adjustment mechanism can be operated electrically, hydraulically or pneumatically.

The so-called rotary piston adjuster is a widespread embodiment. The drive wheel is connected in a rotationally fixed manner to a stator. The stator and a rotor are arranged concentrically to one another, the rotor being connected to a camshaft, an extension of the camshaft or an intermediate shaft in a force-fitting, form-fitting or material-locking manner, for example by means of a press fit, a screw or welded connection. The radial space between the rotor and the stator takes up at least one, but usually a plurality of cavities spaced apart in the circumferential direction. The cavities are delimited pressure-tight in the axial direction by side covers. A vane connected to the rotor extends into each of these cavities. This wing divides each cavity into two pressure chambers. The phase of the camshaft can be adjusted or held relative to the crankshaft by specifically connecting the individual pressure chambers to a hydraulic medium pump or to a hydraulic medium outlet.

To control the camshaft adjuster, sensors record the engine's characteristic data, such as the load condition and engine speed. This data is fed to an electronic control unit which, after comparison of the

Data with a characteristic data field of the internal combustion engine, the adjusting motor of the Controls camshaft adjuster or the inflow and outflow of hydraulic fluid to the various pressure chambers.

Devices for changing the control times are known in which a stator is rotatably mounted on a rotor. The stator and the rotor are each limited in the axial direction by a side cover. Several recesses are made in the inner jacket surface of the stator, these recesses being designed as pressure spaces. In other words, the rotor, the stator and the two side covers enclose the pressure chambers in a pressure-tight manner. Axially running vane grooves are made in the outer circumferential surface of the rotor, in each of which a vane is arranged. The wings extend radially outward from the base of the groove. A wing is arranged in each pressure chamber. Each wing divides a pressure chamber into two counteracting pressure chambers, the wing being freely displaceable within the pressure chamber. By means of a control valve and pressure medium lines, each pressure chamber can optionally be connected to a pressure medium pump or a pressure medium reservoir. If the pressure chambers, which are seen from the respective wing in the drive direction of the stator, are connected to the pressure medium pump and the other pressure chambers are connected to the pressure medium reservoir, the wings move within the pressure chamber against the drive direction of the stator, causing the opening and closing times of the Gas exchange valves is set to "late". Similarly, the opening and closing times of the gas exchange valves are shifted to an early point in time when the pressure medium flow direction is reversed.

By applying pressure medium to the individual pressure medium chambers, a force is exerted on each wing, which force is transmitted to the rotor within the wing groove of the rotor. As a result, the wing is subjected to high material stress in the area of the contact points to the rotor. In particular, the areas of the sash that lie against the edges and corners of the sash groove are subjected to high stress. For reasons of durability, it is envisaged that the wings are made of hardened steel. Thereby, Usually the wing is first formed from a sheet metal part and then hardened as a whole in a hardening furnace.

In addition to the high costs and the long throughput times of this hardening process, there is a risk that the material will warp due to thermal stresses. This has the consequence that the surfaces of the wing, which are provided as sealing surfaces, have to be reworked, making the manufacture of such wings extremely expensive. Summary of the invention

The invention is therefore based on the object of avoiding the disadvantages described and thus creating vanes for use within a device for changing the timing of an internal combustion engine, which are both inexpensive to produce and durable.

According to the invention, this object is achieved in that the wing is only partially hardened. Furthermore, it is provided that the wing is arranged in an axially extending wing groove, which is formed in the outer circumferential surface of the rotor, and the areas of the wing are hardened, which in the assembled state are located in the area of the axially extending groove edges of the wing groove. Alternatively, the wing can be arranged in an axially extending wing groove, which is formed in the outer circumferential surface of the rotor, and the wing can be hardened in the regions which, in the assembled state, are located in the region of the axial ends of the axially extending groove edges of the wing groove. Furthermore, it is provided that an end of the wing facing away from the rotor, which abuts the stator, is hardened. In an advantageous further development of the invention, an end of the wing located in the wing groove is hardened. In this embodiment it is provided that the spring is acted upon by a spring element, which is arranged between the groove base of the wing groove and the end of the wing located in the wing groove, with a radially outward force and the contact point of the wing with the spring element is hardened. A laser hardening method is advantageously used for partial hardening.

As is common in the prior art, in this invention the blades are made from sheet metal by cutting or stamping. In a step following the shaping, the particularly stressed areas of the wing are hardened by means of a laser hardening process. Partially hardened areas in the form of dots or lines can be produced in any shape. This step eliminates the need for conventional, costly thermal hardening processes while reducing the cycle time. A further advantage results from the fact that less thermal energy is introduced into the material in the proposed method, whereby a material distortion of the wings can be avoided. This eliminates the machining steps that are otherwise customary after hardening.

The areas of high material stress to be hardened are primarily in the contact area between the blade and the rotor or between the blade and the stator. The areas that come into contact with the axially extending groove edges of the wing groove should be mentioned above all. It is therefore proposed to harden the wing within this line-like area by means of a laser hardening process. Due to tolerances occurring between the rotor and the wing in the wing groove, it can be assumed that slight tilting can occur between the wing and the rotor during operation of the device. It is therefore proposed in an alternative embodiment to harden the end faces of the wing lying in the axial direction of the rotor in the region of the axially extending groove edges of the wing groove. In comparison to the first embodiment, there is not a region to be hardened in a linear manner, but only two regions to be hardened in a punctiform manner, whereby the hardening cycle time can be further reduced.

Furthermore, it may prove necessary to harden the wing on the contact surface with the stator. This contact zone must be as pressure-tight as possible to avoid leakage between the pressure chambers. For this reason, a spring element is arranged between the groove base of the wing groove and the wing itself, which acts on the wing radially outward with a force. In addition to heavy stress on the wing on the contact surface with the stator, this also results in a high load on the contact surface of the spring. In order to keep wear as low as possible, it is also proposed to harden this area by means of a laser hardening process. Brief description of the drawings

Further features of the invention result from the following description and from the drawings, in which exemplary embodiments of the invention are shown in simplified form. Show it:

1 shows a longitudinal section through a device according to the invention for changing the timing of an internal combustion engine according to the line I-1 from Figure 2, Figure 2 shows a cross section through an inventive device for changing the timing of an internal combustion engine according to Figure 1 along the line

FIG. 3 shows an enlarged view of the detail Z from FIG. 2,

Figure 4, Figure 5 different versions of partially hardened wing. Detailed description of the drawings

1 and 2 show a device 1 according to the invention for changing the control times of an internal combustion engine. The device 1 essentially consists of a stator 2 and a rotor 3 arranged concentrically thereto. A drive wheel 4 is connected to the rotor in a rotationally fixed manner and, in the embodiment shown, is designed as a chain wheel. Embodiments of the drive wheel 4 as a belt or gear are also conceivable. The stator 2 is rotatably mounted on the rotor 3, five recesses 5 spaced apart in the circumferential direction being provided on the inner circumferential surface of the stator 2 in the embodiment shown. The recesses 5 are delimited in the radial direction by the stator 2 and the rotor 3, in the circumferential direction by two side walls 6 of the stator 2 and in the axial direction by a first and a second side cover 7, 8. Each of the recesses 5 is closed pressure-tight in this way. The first and the second side covers 7, 8 are connected to the stator 2 by means of connecting elements 9, for example screws.

Axially extending vane grooves 10 are formed on the outer circumferential surface of the rotor 3, a radially extending vane 11 being arranged in each vane groove 10. A vane 11 extends into each recess 5, the vanes 11 abutting the stator 2 in the radial direction and the first and second side covers 7, 8 in the axial direction. Each vane 11 divides a recess 5 into two pressure chambers 12, 13 working against each other. In order to ensure that the vanes 11 bear against the stator 2 in a pressure-tight manner, spring elements 15 are attached between the groove bases 14 of the vane grooves 10 and the vanes 11 apply a force in the radial direction.

By means of first and second pressure medium lines 16, 17, the first and second pressure chambers 12, 13 can be connected to a pressure medium pump, also not shown, or a pressure medium reservoir, also not shown, via a control valve (not shown). This means that Oil drive 18 is formed, which enables a relative rotation of the stator 2 with respect to the rotor 3. It is provided that either all of the first pressure chambers 12 are connected to the pressure medium pump and all of the second pressure chambers 13 are connected to the pressure medium reservoir, or the exactly opposite configuration. If the first pressure chambers 12 are connected to the pressure medium pump and the second pressure chambers 13 to the pressure medium reservoir, the first pressure chambers 12 expand at the expense of the second pressure chambers 13. This results in a displacement of the wings 11 in the circumferential direction, in the direction shown by the arrow 19. By moving the blades 11, the rotor 3 is rotated relative to the stator 2.

In the embodiment shown, the stator 2 is driven by the crankshaft by means of a chain drive, not shown, which engages with its drive wheel 4. The drive of the stator 2 by means of a belt or gear drive is also conceivable. The rotor 3 is non-positively, positively or materially connected, for example by means of a press fit or by a screw connection by means of a central screw, to a camshaft, not shown. A phase shift between the camshaft and the crankshaft results from the relative rotation of the rotor 3 relative to the stator 2 as a result of the supply and discharge of pressure medium to and from the pressure chambers 12, 13. The control times of the gas exchange valves of the internal combustion engine can thus be varied in a targeted manner by specifically introducing or discharging pressure medium into the pressure chambers 12, 13.

In the embodiment shown, the pressure medium lines 16, 17 are designed as essentially radially arranged bores, which extend from a central bore 20 of the rotor 3 to its outer lateral surface. A central valve (not shown) can be arranged within the central bore 20, via which the pressure chambers 12, 13 can be selectively connected to the pressure medium pump or the pressure medium reservoir. Another possibility is to arrange a pressure medium distributor within the central bore 20, which distributes the pressure medium lines 16, 17 Connects pressure medium channels and ring grooves with the connections of an externally attached central valve.

The essentially radially extending side walls 6 of the recesses 5 are provided with formations 21 which extend into the recesses 5 in the circumferential direction. The formations 21 serve as a stop for the vanes 11 and ensure that the pressure chambers 12, 13 can be supplied with pressure medium, even if the rotor 3 assumes one of its extreme positions relative to the stator 2, in which the vanes 11 rest on one of the side walls 6 ,

In the event of insufficient supply of pressure medium to the device 1, for example during the starting phase of the internal combustion engine, the rotor 3 is moved in an uncontrolled manner relative to the stator 2 due to the alternating torques which the camshaft exerts thereon. In a first phase, the alternating torques of the camshaft urge the vanes 11 in the direction opposite to the direction of rotation 17 until they strike the side walls 6. Furthermore, the moments that change rapidly in the direction that the camshaft exerts on the rotor 3 cause the rotor 3 and thus the wing 11 to swing back and forth in the recesses 5. These phenomena lead to greater wear and to a higher noise level Device 1. In order to prevent these effects, a locking element 22 is attached in device 1. For this purpose, a piston 24 is arranged in an axial bore 23, which is acted upon by a spring 25 in the axial direction with a force. The spring 25 is supported in the axial direction on one side on a ventilation element 26 and is arranged with its axial end facing away from it within the cup-shaped piston 24. Within the first side cover 7, a link 27 is arranged such that the piston 24 is pushed into the link 27 by means of the spring 25 if the pressure medium supply to the device 1 is insufficient, when the rotor 3 assumes a position relative to the stator 2 that corresponds to the position take the two components to each other during the starting phase of the internal combustion engine. Means are also provided to ensure that the piston 24 is adequately supplied with the to push back direction 1 with pressure medium in the axial bore 23 and thus release the lock. This is usually accomplished with pressure medium, which is directed via pressure medium lines (not shown) into a recess 28 which is formed on the end face of the piston 24 on the cover side. In order to be able to discharge leakage oil from the spring chamber of the axial bore 23, the ventilation element 26 is provided with axially extending grooves, along which the pressure medium can be guided to a bore in the second side cover 8.

In Figure 2 and Figure 3, the arrangement of the wings 11 within the wing groove 10 is shown. If hydraulic fluid is now applied to the first or the second pressure chambers 12, 13, a first region 29 of the wing 11 is pressed against the axially extending groove edge 30 of the wing groove 10, as a result of which this first region 29 is exposed to heavy loads.

A spring element 15 is arranged between the groove base 14 of the wing groove 10 and a first end face 31 of the wing 11 arranged within the wing groove 10. The spring element 15 is advantageously designed as a leaf spring, wherein, supported on the groove base 14 of the wing groove 10, the first radial end face 31 of the wing 11 is subjected to a radially directed force. This first end face 31 is also exposed to great loads. The action on the blade 11 with a radially directed force has the result that it is pressed against the stator 2 with a second radial end face 32. The second radial end face 32, which is formed on the side of the wing 11 facing away from the first end face 31, likewise experiences a high load due to the contact pressure. In order to increase the life of the wings 11 and thus the device 1, the wings 11 are hardened. This is usually accomplished by means of a thermal hardening process, for example by passing through a hardening furnace. In addition to the high throughput times and the high costs of this process, the introduction of thermal energy leads to a distortion of the material of the wings 11, as a result of which the side walls of the wings 11 sealing the pressure chambers 12 and 13 must be machined. Therefore it is suggested conditions that the wings 11 are only partially hardened in the loaded areas.

This is shown in Figures 4 and 5. The figures each show a wing 11, only certain areas of the wing 11 being hardened. FIG. 4 shows an embodiment in which the first and second end faces 31, 32 are hardened. Furthermore, a line-shaped area is hardened, which corresponds to the first area 29 which, in the assembled state of the wing 11, bears against the axially extending groove edge 30 of the wing groove 10. Since, when the pressure conditions in the pressure chambers 12, 13 are reversed, the load occurs on the opposite side wall of the wing 11, the wing 11 is hardened on both sides in the first region 29.

A second embodiment of the wing 11 is shown in Figure 5. The first and second end faces 31, 32 are also hardened here. In addition, only the sections 33 of the first region 29 are hardened, which, in the assembled state, bear against the axial ends of the axially extending groove edges 30 of the wing groove 10. The wing 11 is normally arranged with a certain play within the wing groove 10. In operation, this means that the wing 11 is tilted slightly about an axis running radially relative to the rotor 3. As a result, only the sections 33 abut the groove edges 30 of the wing groove 10. This partial hardening can be carried out, for example, by means of laser hardening. Areas of the wing 11 of any shape can be hardened.

In addition to a reduction in cycle time and costs, the lower heat input during the hardening process means that the wing 11 can no longer be machined after the hardening process. reference numeral

Device 26 venting device

Stator 27 backdrop

Rotor 28 recess

Drive wheel 29 first area

Recesses 30 groove edge

Side wall 31 first end face first side cover 32 second end face second side cover 33 section

connecting element

vane

Wing first pressure chamber second pressure chamber

groove base

Spring element first pressure medium line second pressure medium line

actuator

arrow

central bore

formations

locking element

axial bore

piston

feather

Claims

claims

1. Device (1) for changing the timing of an internal combustion engine

- A stator (2) and driven by the crankshaft (3)

- a rotor (3) driving at least one camshaft (4),

- which is driven by the stator (2) via a hydraulic actuator (18),

- The phase position between the crankshaft (3) and the at least one camshaft (4) can be changed via the actuator (18) and

- The actuator (18) comprises at least one pressure chamber,

- In which a wing (11) attached to the rotor (3) engages, - The wing (11) separating the pressure chamber into two hydraulic pressure chambers (12, 13) working against each other, characterized in that

- The wing (11) is only partially hardened.

2. Device (1) according to claim 1, characterized in that

- The wing (11) in an axially extending wing groove (10), which is formed in the outer surface of the rotor (3), is arranged and

- The areas (29) of the wing (11) are hardened, which are in the assembled state in the region of the axially extending groove edges (30) of the wing groove (10).

3. Device (1) according to claim 1, characterized in that

- The wing (11) is arranged in an axially extending wing groove (10) which is formed in the outer circumferential surface of the rotor (3) and - The wing (11) is hardened in the sections (33) which are in the assembled state located in the area of the axial ends of the axially extending groove edges (30) of the wing groove (10).

4. The device (1) according to claim 1, characterized in that an end of the wing (11) which faces away from the rotor (3) and which lies against the stator (2) is hardened.

5. The device (1) according to claim 1, characterized in that one end of the wing (11) located in the wing groove (10) is hardened.

6. The device (1) according to claim 5, characterized in that

- The wing (11) of a spring element (15), which is arranged between the groove base (14) of the wing groove (10) and the end of the wing (11) located in the wing groove (10), with a radially outward directed force is applied and

- The contact point of the wing (11) with the spring element (15) is hardened.

7. The device (1) according to claim 1, characterized in that a laser hardening process is used.