Valve timing control system for internal combustion engine

Information

  • Patent Grant
  • 6802289
  • Patent Number
    6,802,289
  • Date Filed
    Friday, March 7, 2003
    21 years ago
  • Date Issued
    Tuesday, October 12, 2004
    20 years ago
Abstract
A valve timing control system for an internal combustion engine includes a housing having and a cover member mounted thereto, a phase adjusting mechanism accommodated in the housing to hydraulically change the rotation phase of a crankshaft and a camshaft, a supply/discharge rod arranged through a through hole of the cover member and connected to the phase adjusting mechanism, a seal ring engaged with the supply/discharge rod to hermetically seal a clearance between the supply/discharge rod and the phase adjusting mechanism, a taper surface formed on the periphery of the through hole to increase the diameter of the through hole toward the outside of the housing, and a protrusion formed with the cover member in a radially inside area thereof to protrude in the axial direction of the system, wherein the through hole is formed at the protrusion.
Description




BACKGROUND OF THE INVENTION




The present invention relates to a valve timing control system for an internal combustion engine, which controls an opening and closing timing of an intake valve and/or an exhaust valve in accordance with engine operating conditions.




Typically, the valve timing control system comprises a hydraulic phase adjusting mechanism accommodated in a housing and for changing the phase of rotation of a crankshaft and a camshaft, wherein supply/discharge of hydraulic fluid to/from the phase adjusting mechanism is carried out through a supply/discharge rod arranged through a cover member of the housing.




Specifically, the housing comprises a main body having a concave space and a cover member connected thereto so as to close the concave space. A through hole is formed in the center of the cover member to receive the non-rotatable supply/discharge rod. A seal ring having a spring force acting in the diameter increasing direction is engaged with the outer peripheral surface of the supply/discharge rod to hermetically seal a clearance between a front end of the supply/discharge rod and the phase adjusting mechanism by the seal ring. A taper surface is formed on the peripheral surface of the through hole of the cover member to increase the diameter of the through hole toward the outside of the housing, so that when inserting the supply/discharge rod into the through hole, the seal ring can easily be reduced in diameter along the taper surface.




SUMMARY OF THE INVENTION




With the typical valve timing control system, however, the cover member includes a flat plate member, so that if an attempt is made to enhance the insertion-ability of the seal ring by inclining the taper surface of the through hole in the direction to approach the axis of rotation, the cover member should be increased in thickness, which raises inconveniences such as increased weight of the entire system and lowered yield of materials.




It is, therefore, an object of the present invention to provide a valve timing control system for an internal combustion engine, which allows enhancement in the insertion workability of the seal ring without occurrence of increased weight of the entire system and lowered yield of materials.




The present invention provides generally a system for controlling a valve timing in an internal combustion engine, which comprises: a housing comprising a main body having a concave space and a cover member mounted to the main body to close the space, the cover member being formed with a through hole; a phase adjusting mechanism accommodated in the housing, the phase adjusting mechanism hydraulically changing a rotation phase of a crankshaft and a camshaft; a supply and discharge rod arranged through the through hole of the cover member, the supply and discharge rod being connected to the phase adjusting mechanism, the supply and discharge rod failing to be rotatable; a seal ring externally engaged with the supply and discharge rod, the seal ring hermetically sealing a clearance between the supply and discharge rod and the phase adjusting mechanism; a taper surface formed on a periphery of the through hole of the cover member, the taper surface increasing a diameter of the through hole toward the outside of the housing; and a protrusion formed with the cover member in a radially inside area thereof, the protrusion protruding in an axial direction of the system, the through hole being formed at the protrusion.











BRIEF DESCRIPTION OF THE DRAWINGS




The other objects and features of the present invention will become apparent from the following description with reference to the accompanying drawings, wherein:





FIG. 1

is a longitudinal section taken along the line I—I in

FIG. 3

, showing an embodiment of a valve timing control system for an internal combustion engine according to the present invention;





FIG. 2

is a front view of the valve timing control system as seen from arrow II in

FIG. 1

;





FIG. 3

is a cross section taken along the line III—III in

FIG. 1

;





FIG. 4

is a perspective view showing a cover member;





FIG. 5

is a side view showing the cover member;





FIG. 6

is a view similar to

FIG. 4

, showing a seal ring;





FIGS. 7A-7E

are schematic sectional views explaining a method of manufacturing the cover member; and





FIG. 8

is a fragmentary section showing a variation of the embodiment.











DETAILED DESCRIPTION OF THE INVENTION




Referring to the drawings, a description is made about an embodiment of a valve timing control system for an internal combustion engine. Referring to

FIG. 1

, the internal combustion engine comprises a camshaft


1


rotatably supported by a cylinder head, not shown, and provided at the outer periphery of the axially center portion with a driving cam for opening and closing an intake valve or engine valve. The valve timing control system is arranged at the front end, i.e. left side in

FIG. 1

, of camshaft


1


. In this embodiment, the valve timing control system is applied to the drive system of the intake valve. Optionally, the system is applicable to the drive system of the exhaust valve.




The valve timing control system comprises a chain sprocket


2


driven by a crankshaft of the engine through a chain, not shown, a housing or driving rotator


3


having chain sprocket


2


integrated therewith, camshaft


1


having one end to which housing


3


is mounted relatively rotatably as required, a vane rotor


5


integrally connected to the front end of camshaft


1


by a cam bolt


4


and rotatably accommodated in housing


3


, and hydraulic supply/discharge means


6


for supplying/discharging hydraulic fluid to cause relative rotation of housing


3


and vane rotor


5


in accordance with the engine operating conditions. In this embodiment, camshaft


1


and vane rotor


5


constitute a driven rotator.




Housing


3


comprises main body


7


formed by connecting a rear plate


9




a


having at the outer periphery chain sprocket


2


integrated therewith to a peripheral wall member


9




b,


and a cover member


8


connected to the front surface of the main body


7


so as to close the front surface of a concave space of the main body


7


. Referring to

FIG. 3

, four partition walls


10


having trapezoidal section-are protrusively arranged on the inner peripheral surface of the housing main body


7


at intervals of roughly 90°. Cover member


8


is connected by bolts


30


to rear plate


9




a


and peripheral wall member


9




b


which constitute housing main body


7


.




Vane rotor


5


comprises four vanes


11


interposed between partition walls


10


,


10


adjacent in the circumferential direction of housing


3


, each vane


11


defining an advance-angle chamber


12


and a lag-angle chamber


13


in a space between partition walls


10


,


10


. A connection hole


15


is formed in the center of the front surface of vane rotor


5


, in which a supply/discharge rod


16


as will be described later is engaged. A first radial hole


17


and a second radial hole


18


have openings on the peripheral surface of connection hole


15


to communicate with advance-angle chamber


12


and lag-angle chamber


13


, respectively.




Supply/discharge rod


16


is axially protrusively arranged on the inner surface of a VTG cover


20


mounted to the front end of the cylinder head, and has therein a pair of inner passages


21




a.




21




b


communicating with first and second radial holes


17


,


18


of vane rotor


5


. supply/discharge of hydraulic fluid to/from advance-angle chamber


12


and lag-angle chamber


13


is carried out through supply/discharge rod


16


. Three annular grooves


31


are formed in the outer periphery of the front end of supply/discharge rod


16


, with which seal rings


32


are engaged to hermetically seal a clearance between supply/discharge rod


16


and connection hole


15


while allowing relative rotation therebetween. Referring to

FIG. 6

, seal ring


32


is of a resin material having excellent slide-ability and fluid-tightness, and has a slant incision


32




a


partly formed on the circumference. Seal ring


32


, having a resilient force acting in the diameter increasing direction, is engaged in connection hole


15


in the radially compressed state. In this embodiment, seal ring


32


is adopted having slant incision


32




a.


Optionally, other seal ring can be adopted having non-slant incision or having no incision on condition that it has a resilient force acting on the diameter increasing direction.




As shown in

FIG.1

, hydraulic supply/discharge means


6


comprise two hydraulic passages: first hydraulic passage


22


for supplying/discharging hydraulic fluid to/from advance-angle chamber


12


through inner passage


21




a


of supply/discharge rod


16


and first radial hole


17


of vane rotor


5


and second hydraulic passage


23


for supplying/discharging hydraulic fluid to/from lag-angle chamber


13


through inner passage


21




b


of supply/discharge rod


16


and second radial hole


18


of vane rotor


5


. A supply passage


24


and a drain passage


25


are connected to hydraulic passages


22


,


23


, respectively, through a solenoid-controlled selector valve


26


for switching between the passages. Referring to

FIG. 1

, reference numeral


27


designates an oil pan arranged on the bottom of the engine,


28


designates an oil pump, and


29


designates an electronic control unit (ECU) for controlling selector valve


26


.




In this embodiment, the phase adjusting mechanism comprises vane rotor


5


, advance-angle and lag-angle chambers


12


,


13


, and hydraulic supply/discharge means


6


.




Referring to

FIG. 4

, cover member


8


of housing


3


has in the axial center portion a through hole


33


for receiving supply/discharge rod


16


. Referring also to

FIG. 5

, through hole


33


is formed at a protrusion


34


arranged on cover member


8


to protrude axially outward of housing


3


. As shown in

FIG. 1

, a taper surface


33




a


is formed on the peripheral surface of through hole


33


to increase the diameter of through hole


33


toward the outside of housing


3


. When inserting supply/discharge rod


16


into connection hole


33


of vane rotor


5


, taper surface


33




a


serves as a guide for reducing the diameter of seal ring


32


. Taper surface


33




a


may be formed either axially partly or entirely in the area of through hole


33


. In this embodiment, taper surface


33




a


is only partly formed at the front end of protrusion


34


due to working as will be described later.




In this embodiment, cover member


8


in its entirety, including protrusion


34


, is obtained by press forming.




Referring to

FIGS. 7A-7E

, a method of manufacturing cover member


8


is described. Referring to

FIG. 7A

, a disk-like plate material


36


is provided having a hole


35


previously formed in the position corresponding to through hole


33


and a bolt hole, not shown. Referring to

FIG. 7B

, using a first cylindrical punch


37


, first press forming is applied to an edge of hole


35


of plate material


36


. First press forming is to expand the edge of hole


35


axially cylindrically as shown in FIG.


7


C.




Then, referring to

FIG. 7D

, using a second taper punch


38


, second press forming is applied to plate material


36


which has been subjected to first press forming. Second press forming is to extend like a taper a cylindrical wall


39


of plate material


36


in its entirety in conformity with second punch


38


by inserting second punch


38


into the front end of cylindrical wall


39


.




Referring to

FIG. 7E

, cover member


8


shaped in such a way comprises protrusion


34


formed by cylindrical wall


39


extended like a taper and through hole


33


with taper surface


33




a


formed on the inner peripheral surface of cylindrical wall


39


.




Although cover member


8


can be obtained by casting or cutting, press forming allows easy shaping of cover member


8


without relying upon a high-priced mold or complicated cutting work, resulting in a great reduction in manufacturing cost.




Referring to

FIG. 1

, a lock mechanism


40


is arranged to restrict relative rotation of housing


3


and vane rotor


5


at starting of the engine. Lock mechanism


40


comprises a pin hole


41


axially formed in one vane


11


of vane rotor


5


, a lock pin


42


slidably accommodated in pin hole


41


, a spring or biasing means


43


accommodated, together with lock pin


42


, in pin hole


41


and for biasing lock pin


42


toward rear plate


9




a


of housing


3


, i.e. the bottom of housing main body


7


, a lock hole


44


formed in the inner surface of rear plate


9




a


and for receiving the front end of lock pin


42


when vane rotor


5


is in the most lag-angle position, and a hydraulic passage, not shown, for making the lock releasing hydraulic pressure act on lock pin


42


.




When the supplied hydraulic pressure is greater than a set pressure as during the ordinary engine operation, engagement of lock mechanism


40


in lock hole


44


is released by that hydraulic pressure. On the other hand, when the supplied hydraulic pressure is smaller than set pressure as at stopping or starting of the engine, and that vane rotor


5


is returned to the most lag-angle position, lock pin


42


is engaged in lock hole


44


, thereby locking relative rotation of vane rotor


5


and housing


3


.




Next, operation of this embodiment is described. At starting of the engine, lock mechanism


40


mechanically locks vane rotor


5


and housing


3


with vane rotor


5


being rotated to the most lag-angle side with respect to housing


3


, so that torque of the crankshaft input to chain sprocket


2


is transmitted to camshaft


1


as it is. Therefore, camshaft


1


opens and closes the intake valve at a lag-angle timing.




In this state, when, after starting of the engine, operation of selector valve


26


causes communication between supply passage


24


and advance-angle chamber


12


and between drain passage


25


and lag-angle chamber


13


, high-pressure hydraulic fluid is introduced into advance-angle chamber


12


, and locking of lock mechanism


40


is released by that hydraulic pressure. With this, vane rotor


5


is rotated to the advance-angle side with respect to housing


3


under the hydraulic pressure within advance-angle chamber


12


, so that camshaft


1


opens and closes the intake valve at an advance-angle timing.




On the other hand, in this state, when operation of selector valve


26


causes communication between supply passage


24


and lag-angle chamber


13


and between drain passage


25


and advance-angle chamber


12


, vane rotor


5


is rotated to the lag-angle side with respect to housing


3


under the hydraulic pressure within lag-angle chamber


13


, so that camshaft


1


opens and closes the intake valve at a lag-angle timing.




In this embodiment, since protrusion


34


is arranged in a radially inside area of cover member


8


of housing


3


, and through hole


33


is formed at protrusion


34


, sufficiently great axial length of through hole


33


can be secured with the thickness of cover member


8


in its entirety held small. In this embodiment, therefore, the angle of inclination of taper surface


33




a


of through hole


33


can be increased in the direction of the axis of rotation without raising inconveniences such as increased weight of cover member


8


and thus the entire system and lowered yield of materials, resulting in enhancement in the insertion workability of seal ring


32


during assembling. Moreover, as described above, the thickness of cover member


8


can be reduced sufficiently without sacrificing the insertion workability of seal ring


32


, having the advantage of easy press working itself during manufacturing.




Further, protrusion


34


integrated with cover member in the radially inside area serves as an annular reinforcing rib for reinforcing an inner peripheral edge of cover member


8


, so that even if the thickness of cover member


8


is reduced as a whole, cover member


8


is free from deformation, allowing prevention of interference of cover member


8


with vane rotor


5


due to deformation. Particularly, with the type of system wherein cover member


8


is connected to housing main body


7


by bolts


30


as in the embodiment, cover member


8


, particularly, in the radially inside area facing the concave space of housing main body


7


is apt to be deformed by tightening of bolts


30


. In this embodiment, such deformation can largely be reduced by the reinforcing function of protrusion


34


.




Furthermore, with the type of system, since the head of bolts


30


for connecting cover member


8


to housing main body


7


is located on the front surface of cover member


8


, VTC cover


20


should be disposed largely distant from the engine main body so as to prevent interference of the head of bolts


30


with the inner surface of VTC cover


20


. In this embodiment, since the thickness of cover member


8


is reduced as a whole with protrusion


34


arranged at the inner peripheral edge of cover member


8


, the head of bolts


30


can be located in the position displaced backward to the engine main body, obtaining VTC cover


20


approaching the engine main body. Therefore, in this embodiment, a further reduction can be achieved in the overall axial length of the engine, including VTC cover


20


.




Further, in this embodiment, lock hole


44


of lock mechanism


40


is not arranged in cover member


8


, but in housing main body


7


on the bottom, i.e. rear plate


9




a,


having the advantage of a further reduction in the thickness of cover member


8


. Specifically, since lock hole


44


for receiving the front end of cover member


8


needs a certain depth, a member having lock hole


44


should be increased in thickness inevitably. In this embodiment, since lock hole


44


is arranged in the bottom of housing main body


7


, the thickness of cover member


8


can be reduced sufficiently without being subject to constraints of the depth of lock hole


44


.




Referring to

FIG. 8

, there is shown a variation of the embodiment wherein an edge of connection hole


15


of vane rotor


5


is removed to provide a cut corner


50


, then cut corner


50


in the obtuse-angle area close to connection hole


15


is chamfered to form a chamfered portion


51


having circular section. In this variation, an inconvenience can surely be prevented that seal ring


32


makes contact with the edge of connection hole


15


during assembling of seal ring


32


, allowing further enhancement in the assembling workability of seal ring


32


.




Having described the present invention with regard to the preferred embodiment, it is noted that the present invention is not limited thereto, and various changes and modifications can be made without departing from the scope of the present invention. By way of example, in the embodiment, the phase adjusting mechanism is constructed such that the hydraulic pressure is applied-to vane


11


of vane rotor


5


to cause relative rotation of the driving rotator and the driven rotator. Optionally, the phase adjusting mechanism may be constructed such that using a helical gear and the like, displacement of a hydraulically operated piston is converted to relative rotation of the driving rotator and the driven rotator. Moreover, the taper surface


33




a


may be curved as viewed in the section along the axial direction.



Claims
  • 1. A system for controlling a valve timing in an internal combustion engine, comprising:a housing comprising a main body having a concave space and a cover member mounted to the main body to close the space, the cover member being formed with a through hole; a phase adjusting mechanism accommodated in the housing, the phase adjusting mechanism hydraulically changing a rotation phase of a crankshaft and a camshaft; a supply and discharge rod arranged through the through hole of the cover member, the supply and discharge rod being connected to the phase adjusting mechanism, the supply and discharge rod failing to be rotatable; a seal ring externally engaged with the supply and discharge rod, the seal ring hermetically sealing a clearance between the supply and discharge rod and the phase adjusting mechanism; and a protrusion formed with the cover member, the protrusion having the through hole formed therethrough, the protrusion protruding from an inner periphery of the through hole in an axial direction of the system, the protrusion having inner and outer peripheries extending to increase a diameter of the through hole toward the outside of the housing.
  • 2. The system as claimed in claim 1, wherein the main body and the cover member of the housing are connected through bolts.
  • 3. The system as claimed in claim 2, wherein each bolt has a head disposed on a front surface of the cover member.
  • 4. The system as claimed in claim 1, wherein the housing is arranged to be rotatable together with at least one rotator of the crankshaft and the camshaft.
  • 5. The system as claimed in claim 4, wherein the phase adjusting mechanism comprises a vane rotor arranged to be rotatable together with another rotator of the crankshaft and the camshaft, advance-angle and lag-angle chambers arranged on both sides of a vane of the vane rotor, and a hydraulic supply and discharge device communicating with the advance-angle and lag-angle chambers and selectively supplying and discharging a hydraulic pressure to and from the advance-angle and lag-angle chambers.
  • 6. The system as claimed in claim 1, wherein the supply and discharge rod is axially protrusively arranged on an inner surface of a VTC cover mounted to a front end of a cylinder head.
  • 7. The system as claimed in claim 1, wherein the seal ring has a resilient force acting in a direction of increasing diameter thereof.
  • 8. The system as claimed in claim 1, wherein the seal ring is of a resin material and has a slant incision partly formed on the circumference.
  • 9. The system as claimed in claim 1, wherein the taper surface is curved as viewed in a section along the axial direction of the system.
  • 10. The system as claimed in claim 1, wherein the protrusion is tapered from head to base by press forming.
  • 11. The system as claimed in claim 5, further comprising a lock pin which is engaged, when a supplied hydraulic pressure is smaller than a predetermined pressure, with the housing and the vane rotor so as to lock relative rotation of the two.
  • 12. The system as claimed in claim 11, wherein a lock hole is formed in a bottom of the main body of the housing, the lock pin having an end detachably engaged with the lock hole.
  • 13. The system as claimed in claim 5, wherein the vane rotor has in the center of a front surface a connection hole in which the supply and discharge rod is engaged, the connection hole having an edge removed to provide a cut corner.
  • 14. The system as claimed in claim 13, wherein the cut corner in an obtuse-angle area close to the connection hole is chamfered to form a chamfered portion having a circular section.
  • 15. The system as claimed in claim 1, wherein the protrusion is smaller in thickness than the cover member.
  • 16. The system as claimed in claim 1, wherein the protrusion has a substantially uniform thickness.
  • 17. The system as claimed in claim 1, wherein the cover member is substantially flat, and the protrusion comprises a ring member extending from a front facing of the cover member.
  • 18. An internal combustion engine, comprising:a crankshaft; a camshaft; a housing comprising a main body having a concave space and a cover member mounted to the main body to close the space, the cover member being formed with a through hole; a phase adjusting mechanism accommodated in the housing, the phase adjusting mechanism hydraulically changing a rotation phase of the crankshaft and the camshaft; a supply and discharge rod arranged through the through hole of the cover member, the supply and discharge rod being connected to the phase adjusting mechanism, the supply and discharge rod failing to be rotatable; a seal ring externally engaged with the supply and discharge rod, the seal ring hermetically sealing a clearance between the supply and discharge rod and the phase adjusting mechanism; and a protrusion formed with the cover member, the protrusion having the through hole formed therethrough, the protrusion protruding from an inner periphery of the through hole in an axial direction of the system, the protrusion having inner and outer peripheries extending to increase a diameter of the through hole toward the outside of the housing.
  • 19. The internal combustion engine as claimed in claim 18, wherein the cover member is substantially flat, and the protrusion comprises a ring member extending from a front facing of the cover member.
  • 20. A system for controlling a valve timing in an internal combustion engine, comprising:a housing comprising a main body having a concave space and a cover member mounted to the main body to close the space, the cover member being formed with a through hole; a phase adjusting mechanism accommodated in the housing, the phase adjusting mechanism hydraulically changing a rotation phase of a crankshaft and a camshaft; a supply and discharge rod arranged through the through hole of the cover member, the supply and discharge rod being connected to the phase adjusting mechanism, the supply and discharge rod failing to be rotatable; a seal ring externally engaged with the supply and discharge rod, the seal ring hermetically sealing a clearance between the supply and discharge rod and the phase adjusting mechanism; a taper surface formed on a periphery of the through hole of the cover member, the taper surface increasing a diameter of the through hole toward the outside of the housing, the taper surface being curved as viewed in a section along the axial direction of the system; and a protrusion formed with the cover member in a radially inside area thereof, the protrusion protruding in an axial direction of the system, the through hole being formed at the protrusion.
  • 21. A method of manufacturing a cover member for use in a system for controlling a valve timing in an internal combustion engine, the method comprising:preparing a disk-like plate material having a hole previously formed in a position corresponding to the through hole of the cover member; applying a first press forming to an edge of the hole of the plate material using a first cylindrical punch, the first press forming expanding the edge of the hole axially cylindrically; and applying a second press forming to the plate material using a second taper punch, the second press forming extending like a taper a cylindrical wall of the plate material in its entirety in conformity with the second punch by inserting the second punch into an end of the cylindrical wall, whereby a taper surface is formed on a periphery of the through hole of the cover member, the taper surface increasing a diameter of the through hole toward the outside of the housing, the protrusion is formed with the cover member in a radially inside area thereof, the protrusion protruding in an axial direction of the system, and the through hole is formed at the protrusion.
Priority Claims (1)
Number Date Country Kind
2002-061727 Mar 2002 JP
US Referenced Citations (7)
Number Name Date Kind
5588404 Lichti et al. Dec 1996 A
6012419 Iwasaki et al. Jan 2000 A
6176256 Nakajima et al. Jan 2001 B1
6254356 Yamada et al. Jul 2001 B1
6269785 Adachi Aug 2001 B1
6418895 Miyasaka et al. Jul 2002 B1
6532665 Parker Mar 2003 B2