DE102017124489A1 - Camshaft, camshaft module, method for friction-reducing operation of a camshaft and use of one or more piezo elements for the vibration excitation of a camshaft - Google Patents

Abstract

The present invention relates to a camshaft (10) having at least one vibration excitation unit (11) for generating mechanical vibrations, wherein the vibration excitation unit (11) is connected to the camshaft (10) such that the mechanical vibrations in the camshaft ( 10) einkoppelbar.Fern the invention relates to a camshaft module, a method for friction-reducing operation of a camshaft and a use of one or more piezoelectric elements for the vibration excitation of a camshaft.

Description

The invention relates to a camshaft, a camshaft module, a method for friction-reducing operation of a camshaft, and a use of one or more piezoelectric elements for the vibration excitation of a camshaft.

One goal of the further development of internal combustion engines is the reduction of consumption and the reduction of carbon dioxide emissions due to stricter legal regulations. The reduction of the friction losses of camshafts contributes significantly to the fulfillment of legal requirements.

A camshaft in the cylinder head of an internal combustion engine has various functional surfaces, such as the axial and radial bearing surfaces and the cam surfaces, where friction occurs. The axial and radial bearing of the camshaft is often realized with plain bearings due to the low cost and compact design. A disadvantage of the use of plain bearings is the occurring mixed and sliding friction. Mixed friction occurs, for example, during startup of the camshaft, in which the lubricant film is not completely formed in the plain bearing at the time of start-up rotation. As soon as the lubricant film is completely present, it is called the state of sliding friction. In order to reduce the friction losses due to mixed and sliding friction, rolling bearings are used at the bearing points of the camshaft in the prior art. On the running surfaces of the cams also mixed and sliding friction occurs. To reduce friction therefore roller cam follower with integrated roller bearing (cam roller) are used in which the cam surface rolls to actuate the inlet and outlet valves on the rolling bearing circumference. In both applications, the sliding and mixed friction is replaced by the lower rolling friction. On the other hand, the use of rolling bearings in the bearings and Rollenschlepphebeln has the disadvantage that a larger size of the cylinder head housing and the result of the internal combustion engine is required.

A roller rocker arm of the aforementioned type is for example off EP 0 950 799 A2 known. This essentially consists of a drag lever body and at least one rotatably mounted roller on which a respective cam of the camshaft rolls.

The invention is based on the object to provide a camshaft, which contributes to reducing the pollutant emission of the internal combustion engine. The invention is further based on the object to provide a camshaft module, a method for operating a camshaft and the use of one or more piezoelectric elements.

According to the invention this object is achieved with a view to the camshaft by the subject matter of claim 1. With regard to the camshaft module, the method and the use, the above-mentioned object is achieved by the subject matter of claim 12 (camshaft module), claim 14 (method) and claim 17 (use).

The invention is based on the idea of specifying a camshaft having at least one vibration excitation unit for generating mechanical vibrations. The vibration excitation unit is connected to the camshaft in such a way that the mechanical vibrations can be coupled into the camshaft.

The invention has several advantages:

The coupling of mechanical vibrations in the camshaft causes on the functional surfaces, such as the axial and radial bearing surfaces and the cam surfaces, a significant reduction in the occurring mixed and sliding friction. The reduction of the mixing and sliding friction takes place here by the, caused by the vibrations, periodic change of direction of the frictional force in the contact zones or friction zones of the functional surfaces. In other words, the vibration of the camshaft acts on the functional surfaces contact-releasing, whereby the mixing and sliding friction is reduced. Due to the reduction in friction, plain bearings can be used instead of roller bearings. Bearings are cheaper compared to bearings and have a more compact design. A reduction of the cylinder head housing is made possible and saved weight and material.

The invention has the further advantage that the reduction of mixed and sliding friction contributes to an increase in engine efficiency and a reduction in fuel consumption and pollutant emissions.

Preferred embodiments of the invention are specified in the subclaims.

In a particularly preferred embodiment of the invention, the vibration excitation unit is adapted to generate mechanical vibrations in the ultrasonic frequency range. The einkoppelbaren oscillations in the high frequency range allow a very small, in particular minimum amplitude. The vibration or vibration of the camshaft, in particular on the functional surfaces, in the ultrasonic frequency range allows a reduction of friction on the functional surfaces of the camshaft.

Preferably, the vibration excitation unit has at least one piezoelectric element for generating the mechanical vibrations in the ultrasonic frequency range. Piezo elements have the advantage that they allow response times in the microsecond range. Another advantage is their simple and robust construction, where they have no moving parts and are therefore wear-free.

The vibration excitation unit may comprise at least one resonance disc. This design contributes to the support of the mechanical vibrations, in particular the axial mechanical vibrations, and efficient functionality of the camshaft.

In a preferred embodiment, the camshaft has a carrier tube. This embodiment has the advantage that mounting space is created in the camshaft for the arrangement of the vibration excitation unit. Other benefits include weight reduction over massive camshafts, cost reduction through the combination of different materials and grades, transfer of high static and dynamic torques and savings in investment and manufacturing costs through reduced camshaft finishing and finishing costs.

The vibration exciter unit can be arranged on the inside and / or outside of the carrier tube. This design allows the coupling of the mechanical vibrations at different positions on the camshaft.

In a particularly preferred embodiment, one or more piezo elements are arranged at the axial end of the carrier tube. This design allows easy and direct accessibility to the power supply of the piezo elements.

In a further preferred embodiment, the camshaft has at least one energy transmission device which is coupled to the vibration excitation unit.

In a further embodiment, the energy transmission device can be integrated into the carrier tube of the camshaft. This can be arranged at the axial end of the support tube in spatial proximity to the piezoelectric element. The energy transfer device which can be integrated into the carrier tube makes possible a compact and space-saving design of the camshaft.

Preferably, the energy transmission device has at least one slip ring module.

For example, the slip ring module is preferably arranged on the inside or outside of the carrier tube of the camshaft at the axial end of the carrier tube. The design of the slip ring module integrated in the carrier tube enables a compact design of the camshaft. Slip ring modules are robust and compact in their design and reliable in power transmission.

Further preferably, the energy transmission device has at least one primary circuit and at least one secondary circuit. The energy transfer occurs through the inductive coupling of the two circuits. The secondary circuit is arranged on the inside and / or outside of the carrier tube of the camshaft, wherein the primary circuit of the secondary circuit is physically separated by a distance (gap). Due to the effect of the inductive coupling, a voltage is induced in the secondary circuit by the current-carrying primary circuit. The secondary circuit does not have its own voltage source. By coupling with the piezoelectric element is applied to this, the induced voltage. Because of the inverse piezoelectric effect, the applied voltage causes an expansion of the piezoelectric element, which causes the camshaft to vibrate. This embodiment has the advantage that a magnetic alternating field can be formed independently of the relative movement between the primary and secondary circuits. Advantageously, thus, independently of the operating state of the camshaft, a voltage is induced and the camshaft is set in oscillation. Due to the effect of the inductive coupling, the applied voltage on the primary circuit can be further advantageously transformed to a defined operating voltage on the secondary circuit for actuating the piezoelectric element.

In a particularly preferred embodiment, the energy transmission device has at least one magnet and at least one electrical coil, which are inductively coupled to one another. The coil is disposed inside the support tube of the camshaft, the magnet being physically separated from the coil by a gap. Through an alternating magnetic field, an electrical voltage is induced in the circuit of the coil. The magnetic alternating field is formed by a rotational movement of the coil. By coupling the coil with the piezoelectric element is applied to this an induced voltage. Because of the inverse piezoelectric effect, the applied voltage causes an expansion of the piezoelectric element, which causes the camshaft to vibrate. This design has the advantage that the arrangement of the coil in the support tube results in a compact and space-saving design of the camshaft. Advantageously, in this embodiment, the alternating magnetic field during operation of the camshaft is formed by the rotational movement of the electric coil and thereby induces a voltage. There is thus no external power source required.

The camshaft module according to the invention has at least one camshaft according to the invention.

A particularly preferred embodiment of the camshaft module has a housing, in particular a cylinder head housing, and at least one voltage source. The voltage source is coupled to the energy transmission device of the camshaft or coupled. In the housing at least one camshaft according to the invention is mounted mounted. The voltage source can be arranged, for example, outside or inside the housing. By the voltage source, the at least one piezoelectric element can be activated and deactivated. The advantage of the arrangement of the voltage source outside the housing is the easy accessibility during assembly and replacement in case of damage of the voltage source.

In the method according to the invention for friction-reducing operation of a camshaft, at least one vibration excitation unit couples mechanical vibrations into the camshaft and sets them in vibration.

In a preferred embodiment of the method, mechanical vibrations in tangential and / or longitudinal direction are coupled relative to the longitudinal axis of the camshaft. The combination of the directions of vibration or the generation of superimposed vibrations, causes a particularly strong reduction of friction.

In a further preferred embodiment of the method, the vibration excitation unit is temporarily activated during the operation of the camshaft. In this case, mechanical vibrations are coupled into the camshaft, especially at the time of occurrence of mixed friction. This has the advantage that the voltage source for activating the piezoelectric element is deactivated from the time of formation of a hydrodynamic lubricant film and energy is saved.

When using one or more piezoelectric elements according to the invention for the vibration excitation of a camshaft, it is vibrated in such a way that the mixing and sliding friction occurring on the functional surfaces of the camshaft is significantly reduced during operation.

In use, a voltage source is activated. The voltage source results in the flow of electrical current in the utility or primary circuit. By an energy transfer device, an electric current or an electrical voltage is transmitted to one or more piezo elements. The transmission of the electric current takes place due to a slip ring module. In the case of inductive coupling, in a first variant, an electrical voltage (induction voltage) is induced by the primary circuit in a secondary circuit and thus transmitted. In a second variant, a voltage is injected into the circuit of the coil by a rotating coil and a magnet. Due to the concern of the electrical voltage, the piezoelectric element is activated. Because of the inverse piezoelectric effect, the piezoelectric element expands, causing the camshaft to oscillate in the ultrasonic frequency range. The oscillating camshaft reduces the mixing and sliding friction on the functional surfaces of the camshaft.

For further advantages of the use according to the invention reference is made to the comments on the camshaft according to the invention.

The invention will be explained in more detail below with reference to exemplary embodiments with reference to the attached schematic drawings with further details.

• 1 eine schematische Detailansicht eines Querschnitts durch eine Nockenwelle nach einem bevorzugten erfindungsgemäßen Ausführungsbeispiel;
• 2 eine schematische Detailansicht eines Querschnitts einer Nockenwelle nach einem weiteren bevorzugten erfindungsgemäßen Ausführungsbeispiel; und
• 3 eine Detailansicht eines Querschnitts durch die Nockenwelle gemäß 2 für ein bevorzugtes erfindungsgemäßes Ausführungsbeispiel zur Energieübertragung.

In this show

• 1 a schematic detail view of a cross section through a camshaft according to a preferred embodiment of the invention;
• 2 a schematic detail view of a cross section of a camshaft according to another preferred embodiment of the invention; and
• 3 a detailed view of a cross section through the camshaft according to 2 for a preferred embodiment of the invention for energy transmission.

In the schematic detail view of the cross section according to 1 is a camshaft 10 shown a carrier tube 14 and a vibration exciter unit 11 includes. Furthermore, a power transmission device 15 and a resonance disc 13 intended.

The carrier tube 14 has a defined inner diameter and a defined Outside diameter on. The inner diameter and the outer diameter are in such a ratio that a maximum interior with a minimum outer diameter of the support ear 14 and in compliance with the component requirements of the support tube 14 is formed. The interior of the support tube 14 forms a mounting space 20 in which a part of the vibration excitation unit 11 and a part of the power transmission device 15 are arranged. In the mounting room 20 of the carrier tube 14 It is also possible for other mechanical components, functional components and / or further components to be arranged, which in 1 are not shown.

The vibration exciter unit 11 includes a piezo element 12 and a resonance disc 13 ,

The piezo element 12 has, for example, a cylindrical, in particular a hollow cylindrical, or another geometric design. The piezo element 12 may be formed by a piezoelectric membrane or more piezoelectric membranes. An outer surface or outer contour of the piezoelectric element 12 has a direct contact with the support tube 14 on, with the piezoelectric element 12 For example, frictional and / or positive and / or other types of connection rotationally fixed to the support tube 14 connected is. The piezo element 12 is adapted in such a way that generates mechanical vibrations in the ultrasonic frequency range and in the camshaft 10 can be coupled. The piezo element 12 is in the mounting room 20 of the carrier ear 14 in the region of an axial end 21 the camshaft 10 arranged. The piezo element 12 can also be at other positions in the mounting room 20 of the carrier tube 14 be arranged. This allows a coupling of vibrations in the camshaft 10 at different points of the carrier tube 14 , The axial end 21 the camshaft 10 may be through a first axial end and / or a second axial end of the camshaft 10 be formed. This applies to all embodiments.

The resonance disc 13 has a defined inner diameter and a defined outer diameter. The resonance disc 13 is in cross section through one of the longitudinal axis of the resonant disc 13 formed in the direction of the peripheral surface web. The web has in the area of the outer diameter on a symmetrical shape extension. The resonance disc 13 is designed such that with minimum size of the resonant disc 13 an oscillation ability of the resonance disc 13 achieved in the ultrasonic frequency range. The resonance disc 13 allows a controlled amplification and / or stabilization of mechanical vibrations, in particular axial mechanical vibrations. Furthermore, the resonance disc 13 Not shown material recesses for weight reduction.

The resonance disc 13 is in the embodiment according to 1 in the region of the piezoelectric element 12 outside on the carrier tube 14 arranged. The resonance disc 13 is arranged such that the coupled oscillations of the piezoelectric element 12 controlled reinforced and / or stabilized. Furthermore, several resonance discs can also be used 13 at different positions on the outside of the carrier tube 14 be arranged. For example, the resonance disc 13 non-positively and / or positively with the support tube 14 connected. The resonance disc 13 can thereby rotatably by other types of connection with the support tube 14 be connected.

In the embodiment according to 1 has the energy transfer device 15 a magnet 16 and an electric coil 17 on, which may be formed by a winding package or multiple winding packages. The sink 17 has a defined number of windings. Furthermore, the magnet 16 comprise one or more permanent magnets, electromagnets or other magnets. The sink 17 is in the mounting room 20 at the axial end 21 of the carrier tube 14 arranged, with the coil 17 directly to the piezo element 12 borders. The sink 17 has a compact design. The sink 17 is with the piezo element 12 , For example, by cable lines or conductors, electrically connected. The magnet 16 is outside the carrier ear 14 the coil 17 arranged directly opposite one another. The magnet 16 can be integrally formed by a cylinder head housing and rotationally fixed, or held in rotation by an additional component. The sink 17 and the magnet 16 are physically separated by a distance, in particular by a gap.

As in 1 shown, the magnet points 16 and the coil 17 a cylindrical design. In particular, the coil can 17 be formed hollow cylindrical, wherein the outer diameter of the magnet 16 smaller than the inside diameter of the coil 17 is. The magnet 16 can also have a cylindrical, in particular hollow cylindrical, design. This allows a mesh of the magnet 16 and the coil 17 and thus a compact, integrated design of the energy transmission device 15 on the camshaft 10 , The physical separation between the magnet 16 and the coil 17 can also be formed by a distance, in particular a gap here. In general, the magnet can 16 and the coil 17 be formed by other geometric shapes.

In operation, this is due to a rotational movement of the camshaft 10 around a longitudinal axis the camshaft 10 at an angular velocity ω between the magnet 16 and the coil 17 an unrepresented alternating magnetic field formed. Due to an inductive coupling is in the windings of the coil 17 induces a voltage. The sink 17 forms with the piezo element 12 a closed circuit, whereby the induced voltage also at the piezo element 12 is applied. The piezo element 12 is activated by the applied induction voltage and performs an oscillating motion due to the inverse piezo effect. Due to the oscillating movement of the piezoelectric element 12 is via one or more contact surfaces or contact contours of the piezoelectric element 12 a mechanical vibration on the inner surface of the support tube 14 transferred and thus in the camshaft 10 coupled. The camshaft 10 is thereby vibrated in the ultrasonic frequency range, whereby a reduction in friction at the functional surfaces of the camshaft 10 results.

In an alternative embodiment of the energy transmission device 15 is the magnet 16 rotatably connected to a motor shaft, not shown, in particular a shaft of an electric motor connected. This allows a rotational movement of the magnet 16 , whereby even with a stationary camshaft 10 a voltage in the windings of the coil 17 can be induced. The camshaft 10 can thus be set in vibration before the operation of the internal combustion engine. In other words, the camshaft 10 already at the time of the start of the rotational movement of the camshaft 10 vibrated and an occurring mixed friction at the contact surfaces of the camshaft 10 be counteracted.

The alternative embodiment of the energy transmission device 15 may comprise a device for generating a magnetic and / or an electromagnetic alternating field, wherein the device, the alternating field independent of a rotational movement of the camshaft 10 generated.

In 2 is a camshaft on the basis of a schematic detail view of a cross section 10 shown according to a preferred embodiment of the invention. The camshaft 10 has a carrier tube 14 as in the embodiment according to 1 described, and a vibration exciter unit 11 on.

The vibration exciter unit 11 includes two piezo elements 12 and a resonance disc 13 , which has an external toothing, for example a helical toothing. The resonance disc 13 can in the embodiment according to 2 have a dual function. On the one hand, the resonance disc 13 the camshaft 10 in a rotational movement and on the other hand, amplify mechanical vibrations and / or stabilize, in the camshaft 10 be coupled. The dual function of the resonance disc 13 therefore allows a weight reduction of the camshaft 10 by minimizing the number of components.

The resonance disc 13 is outside at the axial end 21 of the carrier tube 14 arranged, with the resonance disc 13 non-positively and / or positively and / or non-rotatably by other types of connection with the support tube 14 connected is. The resonance disc 13 can be a cross-sectional shape as in the embodiment according to 1 respectively.

The piezo elements 12 form as in 2 well recognizable, a mating and are in the mounting room 20 of the carrier tube 14 directly adjacent to each other at the axial end 21 of the carrier tube 14 arranged. The piezo elements 12 and the resonance disc 13 are at the same axial end 21 of the carrier tube 14 arranged at the same height. The resonance disc 13 is designed such that an oscillatory ability, for example. A controlled amplification and / or stabilization of mechanical vibrations, in particular axial mechanical vibrations in the ultrasonic frequency range through the resonant disc 13 is guaranteed. For example, vibrations of other frequency ranges can be controlled amplified and / or stabilized. The piezo elements 12 are connected to each other, for example. In a series circuit or a parallel circuit, signal-connected and can frictionally and / or positively and / or other types of connection rotation with the support tube 14 be connected.

Furthermore, the piezo elements 12 , in the embodiment according to 2 , a second part of a secondary circuit 19 on that with a first part of the secondary circuit 19 a power transmission device, not shown 15 is coupled and forms a closed secondary circuit. The second part of the secondary circuit 19 is, for example, formed by flexible and / or rigid lines. The lines are doing through the support tube 14 For example, through holes or other openings in the support tube 14 guided and with the first part of the secondary circuit 19 connected.

The activation of the piezo elements 12 done by a on the piezo elements 12 applied induced voltage. The induction voltage is in the embodiment according to 2 by an energy transfer device 15 , as in 3 shown, then to the embodiment according to 3 closer will be received. The coupling of the mechanical vibrations in the camshaft 10 through the piezo elements 12 takes place as in the embodiment according to 1 described.

In the detail view of the cross section according to 3 is a camshaft 10 according to 2 shown a carrier ear 14 according to 1 and a power transmission device 15 having. The energy transfer device 15 includes a current-carrying primary circuit 18 and a first part of a secondary circuit 19 connected to the second part of the secondary circuit of the two piezo elements 12 , in the 2 are shown, a closed secondary circuit 19 forms. For example, the primary circuit 18 and the secondary circuit 19 each formed by one or more coils. The secondary circuit 19 is outside the carrier tube 14 arranged and with the support tube 14 rotatably connected. In this case, the secondary circuit 19 be formed by a closed or a split design, both types of the support tube 14 can enclose. The primary circuit 18 is from the carrier tube 14 decoupled. The primary circuit 18 can also be formed by a closed or split design, here also both types of support tube 14 can enclose. The primary circuit 18 and the secondary circuit 19 can also be in another arrangement form on or around the support tube 14 be arranged.

For example, the primary circuit 18 by a cylinder head housing or an additional component, which is not shown rotatably held. The primary circuit 18 and the secondary circuit 19 are physically separated by a distance, in particular by a gap. The live primary circuit 18 generates an unillustrated electromagnetic field. By the rotational movement of the camshaft 10 and thus the secondary circuit 19 with the angular velocity ω the electromagnetic field acts like an electromagnetic alternating field, whereby a voltage is induced in the windings of the secondary circuit. The induction voltage generated lies directly on the piezo elements 12 according to 2 on, causing the piezo elements 12 to be activated. In the embodiment according to 3 Can also with a stationary camshaft 10 by an inductive coupling a voltage in the secondary circuit 19 be induced.

In an alternative embodiment of the vibration excitation unit 11 , the vibration exciter unit can 11 a device, not shown, comprising a vibration converter, which converts electrical vibrations into mechanical vibrations in the ultrasonic frequency range. The vibration converter is vibrationally connected to a booster unit, whereby the booster unit can amplify or reduce the amplitude of the mechanical vibration. Furthermore, the booster unit is vibrationally connected to a sonotrode which controls the mechanical vibrations in the camshaft 10 couples. The camshaft 10 is thereby vibrated in the ultrasonic frequency range.

In addition to the embodiments according to 1 and 3 is to mention that the camshaft 10 not to an embodiment of the energy transmission device 15 is restricted. For example, the camshaft 10 also one or more combinations (s), not shown, of the energy transmission device 15 according to 1 and 3 respectively. Furthermore, the energy transmission device 15 be formed by a slip ring module in another embodiment.

LIST OF REFERENCE NUMBERS

10

camshaft

11

Vibration exciter unit

12

piezo element

13

resonance disc

14

support tube

15

Energy transfer device

16

magnet

17

Kitchen sink

18

Primary circuit

19

Secondary circuit

20

mounting space

21

axial end

ω

angular velocity

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0950799 A2 [0004]

Claims (17)

Camshaft (10) with at least one vibration exciter unit (11) for generating mechanical vibrations, wherein the vibration excitation unit (11) with the camshaft (10) is connected such that the mechanical vibrations in the camshaft (10) can be coupled. Camshaft to Claim 1 characterized in that the vibration excitation unit (11) is adapted to generate mechanical vibrations in the ultrasonic frequency range. Camshaft to Claim 1 or 2 characterized in that the vibration excitation unit (11) has at least one piezoelectric element (12). Camshaft according to one of the preceding claims, characterized in that the vibration excitation unit (11) has at least one resonance disc (13). Camshaft according to one of the preceding claims, characterized in that the camshaft (10) has a carrier tube (14). Camshaft according to one of the preceding claims, characterized in that the vibration excitation unit (11) inside and / or outside of the support tube (14) is arranged. Camshaft according to one of the preceding claims, characterized in that one or more piezo elements (12) at the axial end of the support tube (14) are arranged. Camshaft according to one of the preceding claims, characterized in that the camshaft (10) has at least one energy transmission device (15) which is coupled to the vibration excitation unit (11). Camshaft to Claim 8 characterized in that the energy transfer device (15) has at least one slip ring module. Camshaft to Claim 8 characterized in that the energy transfer device (15) at least one primary circuit (18) and at least one secondary circuit (19) which are inductively coupled together and the secondary circuit (19) inside and / or outside of the support tube (14) is arranged. Camshaft to Claim 8 characterized in that the energy transfer device (15) at least one magnet (16) and at least one electrical coil (17), which are inductively coupled together, and the coil (17) is arranged inside the support tube (14). Camshaft module with at least one camshaft (10) after Claim 1 , Camshaft module after Claim 12 characterized in that the camshaft module has a housing, in particular a cylinder head housing, and at least one voltage source, wherein the voltage source with the energy transmission device (15) of the camshaft (10) is coupled or coupled. Method for friction-reducing operation of a camshaft, in which mechanical vibrations are coupled into the camshaft (10) by at least one vibration excitation unit (11) and the camshaft (10) is vibrated. Method according to Claim 14 characterized in that the mechanical vibrations in tangential and / or longitudinal direction relative to the longitudinal axis of the camshaft (10) are coupled. Method according to Claim 14 characterized in that the vibration excitation unit (11) is temporarily activated during operation of the camshaft (10). Use of one or more piezo elements for the vibration excitation of a camshaft (10) for friction-reducing operation.

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