FIELD OF THE INVENTION
[0001] The present invention relates to a detent device for two rocker arm shafts on which
rocker arms connecting intake and exhaust cams to intake and exhaust valves are swingably
carried in a valve-operating device in an internal combustion engine.
BACKGROUND ART
[0002] In general, in a valve-operating device in an internal combustion engine of an SOHC
type or the like, two rocker arm shafts are juxtaposed at a distance in a cylinder
head of an engine body, and intake and exhaust cams and intake and exhaust valves
are connected to each other by rocker arms swingably carried on the rocker arm shafts,
so that the intake and exhaust valves are opened and closed with a predetermined timing
by the rotation of the intake and exhaust cams (see Japanese Patent Application Laid-open
No.
2000-329002).
[0003] It should be noted here that in such valve-operating device, the two rocker arm shafts
on a valve-operating camshaft are supported by press-fitting into rocker arm shaft
bores defined in the cylinder head or by another means, but provided with a detent
means for prevention of the rotation with respect to the cylinder head. For example,
as shown in Fig. 5, and as disclosed in document
JP 09-177511, a central portion of a set plate is screwed to the cylinder head between the two
rocker arm shafts by a tightening bolt, and detent portions formed symmetrically on
lower surfaces of ends of left and right arms of the set plate are put into abutment
against notches of the two rocker arm shafts, so that the rotation of the two rocker
arm shafts is prevented.
[0004] However, such conventional detent means for the rocker arm shafts suffers from the
following problem: During tightening of a set plate by the tightening bolt, the set
plate is rotated in a tightening direction and hence, it is inevitable that a slight
gap
s is created between the notch of one of the rocker arm shafts located on the rear
side in the direction of tightening and rotating the set plate and the detent portion
of the set plate, and during operation of the engine, a striking sound is generated
by the free rotation of the rocker arm shafts due to such gap
s.
[0005] The following means are expected as a solution for such problem:
- (1) Separate detent set plates are mounted on the two rocker arm shafts; and
- (2) A detent O-ring is mounted between each of the rocker arm shafts and the rocker
arm shaft bore.
[0006] The means (1) suffers from another problem: the number of parts is increased, resulting
in an increase in cost, and moreover, a surplus space is occupied and hence, the layout
therefore is difficult. The means (2) also suffers from another problem: it is necessary
to subject the rocker arm shafts to a surplus working or processing, and moreover,
the number of parts is increased and further, a labor is taken for the assembling
operation.
DISCLOSURE OF THE INVENTION
[0007] The present invention has been accomplished with such circumstances in view, and
it is an object of the present invention to provide a new detent device for a rocker
arm shaft in a valve-operating device in an internal combustion engine, wherein all
of the above-described problems are solved.
[0008] To achieve the above object, according to the present invention, in a valve-operating
device in an internal combustion engine in which two rocker arm shafts are juxtaposed
at a distance in a cylinder head of an engine body, and rocker arms connecting intake
and exhaust cams to intake and exhaust valves are swingably carried on the rocker
arm shafts, so that the intake and exhaust valves are opened and closed with a predetermined
timing by the rotation of the intake and exhaust cams,
an intermediate portion of a detent plate, from which a first arm and a second arm
are extended integrally, is fixed in a tightened manner to the cylinder head at an
intermediate portion of the two rocker arm shafts by a threaded member, and the first
and second arms of the detent plate have engage portions provided thereon on a front
side in a direction of tightening rotation of the threaded member, respectively, so
that the engage portions are respectively brought into engagement with engaged portions
formed in oppositely turned attitudes on the two rocker arm shafts to prevent the
rotation of the rocker arm shafts. With such feature, the prevention of the rotation
of the two rocker arm shafts can be achieved properly by the tightening and fixing
of the detent plate to the cylinder head by the threaded member, thereby previously
preventing the generation of a striking sound due to the free rotation of the two
rocker arm shafts during operation of the engine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Fig. 1 is a vertical sectional view of essential portions of an internal combustion
engine including a detent device for rocker arm shafts in valve-operating device according
to the present invention; Fig. 2 is a sectional view taken along a line 2-2 in Fig.
1; Fig.3 is an enlarged sectional view taken along a line 3-3 in Fig.1; Fig.4 is a
sectional view taken along a line 4-4 in Fig. 1; and Fig. 5 is a sectional view similar
to Fig. 4 but showing a conventional valve-operating device.
BEST MODE FOR CARRYING OUT THE INVENTION
[0010] The mode for carrying out the present invention will now be described by way of an
embodiment shown in the accompanying drawings.
[0011] First, an embodiment of the present invention will be described with reference to
Figs.1 to 4.
[0012] Referring to Figs . 1 and 2, an engine body E of an SOHC-type air-cooled 4-cycle
internal combustion engine includes a cylinder block 1 having a cylinder bore 2 provided
therein, a cylinder head 3 which is fixed to a deck surface of the cylinder block
1 and has a combustion chamber 4 defined therein to confront the cylinder bore 2,
and a crankcase 5 fixed to a lower surface of the cylinder block 1. A valve-operating
device V, which will be described hereinafter, is mounted in the cylinder head 3,
and a head cover 6 is mounted on the cylinder head 3 to cover the valve-operating
device V. A piston 8 is slidably received in the cylinder bore 2 with a cylinder sleeve
7 interposed therebetween, and is connected to a crankshaft which is not shown through
a connecting rod 10.
[0013] This internal combustion engine is of a uni-flow type, and the cylinder 3 is provided
with an intake port 11 which opens into one side of the cylinder head 3, and an exhaust
port 12 which opens into the other side of the cylinder head. The intake port 11 and
the exhaust port 12 are opposed to each other. An intake system In is connected to
the intake port 11, and an exhaust system Ex is connected to the exhaust port 12.
An intake valve 13 is mounted in the intake port 11 for opening and closing an intake
valve bore permitting the intake port 11 and the combustion chamber 4 into communication
with each other, and an exhaust valve 14 is mounted in the exhaust port 12 for opening
and closing an exhaust valve bore permitting the exhaust port 12 and the combustion
chamber 4 into communication with each other. The intake and exhaust valves 13 and
14 are retained as usual in their closed positions by valve springs 15 and 16, respectively.
A spark plug 17 is threadedly mounted in a wall surface of the cylinder head 3 surrounding
the combustion chamber 4 with its electrode facing into the combustion chamber 4.
[0014] A single valve-operating camshaft 19 is rotatably carried in a central portion of
a valve-operating chamber defined above the cylinder head 3 with bearings 23 and 24
interposed therebetween. An intake cam 20 and an exhaust cam 21 are integrally formed
at an axially intermediate portion of the valve-operating camshaft 19.
[0015] A timing transmitting chamber 25 is defined in one side (a left side in Figs. 2 and
3) of and astride the cylinder block 1 and the cylinder head 3, and a timing driven
gear 26 is fixed at one end (a left end in Figs.2 and 3) of the valve-operating camshaft
19 within the timing transmitting chamber 25. The gear 26 is operated in operative
association with a timing driving gear fixed on a crankshaft (not shown) through an
endless timing chain 27, so that the rotation of the crankshaft is transmitted at
a reduction ratio of 1/2 to the valve-operating camshaft as usual. A bolt 28 passed
through a sidewall of the cylinder head 3 is inserted through the hollow valve-operating
camshaft 19, and a cover 29 is threadedly mounted to an end of the bolt 28 to cover
an opening in the timing transmitting chamber 25 on the side of the cylinder head
3.
[0016] Intake-side and exhaust-side two rocker arm shaft bores 30 and 31 are provided in
the cylinder head 3 to extend laterally above the valve-operating camshaft 19 in parallel
to the valve-operating camshaft 19. The intake-side and exhaust-side two rocker arm
shaft bores 30 and 31 are formed as blind bores which open into the timing transmitting
chamber 25, as shown in Fig.3. In the present embodiment, the exhaust-side rocker
arm shaft bore 31 is formed longer than the intake-side rocker arm shaft bore 30.
Two, i.e., intake-side and exhaust-side hollow rocker arm shafts 32 and 33 are press-fitted
into the two rocker arm shaft bores 30 and 31 from the sides of their openings. Intake-side
and exhaust-side rocker arms 34 and 35 are swingably supported at their intermediate
portions on the two rocker arm shafts 32 and 33 with their positions displaced from
each other in axial directions of the rocker arm shafts 32 and 33, respectively. The
intake-side rocker arm 34 is connected at its outer end to an upper end of the intake
valve 13 through a tappet 37 and at its inner end to a cam face of the intake cam
20 on the valve-operating camshaft 19 through a roller 39 pivotably supported at such
inner end. On the other hand, the exhaust-side rocker arm 35 is connected at its outer
end to an upper end of the exhaust valve 14 through a tappet 38 and at its inner end
to a cam face of the exhaust cam 21 on the valve-operating camshaft 19 through a roller
40 pivotably supported at such inner end. Therefore, the rotation of the valve-operating
camshaft 19 causes the intake-side and exhaust-side rocker arms 34 and 35 to be swung
about the rocker arm shafts 32 and 33, respectively, whereby the intake valve 13 and
the exhaust valve 14 are opened and closed with a predetermined timing by cooperation
with the valve springs 15 and 16 to conduct the operation of the internal combustion
engine.
[0017] However, the two intake-side and exhaust-side rocker arm shafts 32 and 33 are provided
with detent means, so that the rocker arm shafts 32 and 33 are prevented from being
freely rotated within the rocker arm shaft bores 30 and 31, even if the valve-operating
device V is operated. More specifically, as shown in Figs. 3 and 4, a detent plate
42 is fixed at its central portion in a tightened manner by a threaded member, namely,
a tightening bolt 43 immediately above and in parallel to the valve-operating camshaft
19. The detent plate 42 is integrally formed with a first arm 42a extending toward
the intake-side rocker arm shaft 32, and a second arm 42b extending toward the exhaust-side
rocker arm shaft 33, and has a lower surface formed as an arcuate recessed surface
substantially concentric with the valve-operating camshaft 19. Flat engage portions
42c and 42d capable of being engaged with engaged portions 32a and 33a (which will
be described hereinafter) of the two rocker arm shafts 32 and 33 are formed on the
first and second arms 42a and 42b of the detent plate 42 at side faces of ends of
the detent plate 42 on a front side in a direction of tightening rotation of the tightening
bolt 43. As shown in Fig. 4, the engage portion 42c of the first arm 42a is formed
in a downward turned attitude on the side face of the end, while the engage portion
42d of the second arm 42b is formed in an upward turned attitude on the side face
of the end. The engaged portions 32a and 33a notched in a semi-circular shape are
formed at one ends of the two rocker arm shafts 32 and 33 corresponding to the detent
plate 42. As is shown in Fig. 4, when the tightening bolt 43 is rotated in the tightening
direction (a direction indicated by an arrow a in Fig.4) to fix the detent plate 42
in the tightened manner to the cylinder head 3 by the tightening bolt 43, the detent
plate 42 is also rotated in the same direction (a direction indicated by an arrow
b in Fig. 4), whereby the engage portions 42c and 42d at the opposite ends of the
detent plate 42 are closely engaged with the engaged portions 32a and 33a of the two
rocker arm shafts 32 and 33. In this manner, the two rocker arm shafts 32 and 33 are
prevented reliably from being rotated by the rotated tightening of the threaded member,
i.e., the tightening bolt 43 for the detent plate 42, whereby the generation of a
striking sound due to the free rotation of the two rocker arm shafts 32 and 33 during
operation of the engine can be prevented previously.
[0018] Although the embodiment of the present invention has been described, it will be understood
that the present invention is not limited to the above-described embodiment, and various
embodiments may be made within the scope of the invention. For example, the detent
device for the rocker arm shafts according to the present invention has been described
as being carried out in the SOHC-type internal combustion engine in the above-described
embodiment, but it is of course that the detent device is applicable to another internal
combustion engine including two rocker arm shafts.
1. In a valve-operating device in an internal combustion engine in which two rocker arm
shafts (32, 33) are juxtaposed at a distance in a cylinder head (3) of an engine body
(E), and rocker arms (34, 35) connecting intake and exhaust cams (21, 22) to intake
and exhaust valves (13, 14) are swingably carried on said rocker arm shafts (32, 33),
so that said intake and exhaust valves (13, 14) are opened and closed with a predetermined
timing through said rocker arms (34, 35) by the rotation of said intake and exhaust
cams (21, 22),
a detent device for the rocker arm shafts, wherein an intermediate portion of a detent
plate (42), from which a first arm (42a) and a second arm (42b) are extended integrally,
is fixed in a tightened manner to the cylinder head (3) at intermediate portions of
said two rocker arm shafts (32, 33) by a threaded member (43), and said first and
second arms (42a, 42b) of said detent plate (42) have engage portions (42c, 42d) provided
thereon on a front side in a direction of tightening rotation of said threaded member
(43), respectively, so that said engage portions (42c, 42d) are respectively brought
into engagement with engaged portions (32a, 33a) formed in oppositely turned attitudes
on said two rocker arm shafts (32, 33) to prevent the rotation of said rocker arm
shafts (32, 33).
1. In einer Ventilbetätigungsvorrichtung in einem Verbrennungsmotor, in welchem in einem
Zylinderkopf (3) eines Motorkörpers (E) zwei Kipphebelwellen (32, 33) um einen Abstand
nebeneinander angeordnet sind, und Einlass- und Auslassnocken (21, 22) mit Einlass-
und Auslassventilen (13, 14) verbindende Kipphebel (34, 35) auf den Kipphebelwellen
(32, 33) derart schwenkbar getragen sind, dass die Einlass- und Auslassventile (13,
14) durch die Kipphebel (34, 35) mittels Drehen der Einlass- und Auslassnocken (21,
22) mit einer vorbestimmten Zeitsteuerung geöffnet und geschlossen werden,
eine Feststellvorrichtung für die Kipphebelwellen, in welcher ein Zwischenabschnitt
einer Feststellplatte (42), von welchem ein erster Arm (42a) und ein zweiter Arm (42b)
integral ausgehen, mittels eines Gewindeglieds (43) fest an dem Zylinderkopf (3) befestigt
ist, und zwar an Zwischenabschnitten der beiden Kipphebelwellen (32, 33), und die
ersten und zweiten Arme (42a, 42b) der Feststellplatte (42) Eingriffsabschnitte (42c,
42d) aufweisen, die jeweils auf einer vorderen Seite in einer Richtung der Befestigungsdrehung
des Gewindeglieds (43) daran vorgesehen sind, so dass die Eingriffsabschnitte (42c,
42d) jeweils mit in Eingriff stehenden Abschnitten (32a, 33a), die auf den Kipphebelwellen
(32, 33) voneinander abgewandt angeordnet ausgebildet sind, in Eingriff gebracht werden,
um die Drehung der Kipphebelwellen (32, 33) zu verhindern.
1. Dans un dispositif d'actionnement de soupape dans un moteur à combustion interne,
dans lequel deux axes de culbuteur (32, 33) sont juxtaposés à une certaine distance
dans une culasse (3) d'un corps de moteur (E), et des culbuteurs (34, 35) reliant
des cames d'admission et d'échappement (21, 22) aux soupapes d'admission et d'échappement
(13, 14) sont supportés de manière oscillante sur lesdits axes de culbuteur (32, 33),
de sorte que lesdites soupapes d'admission et d'échappement (13, 14) sont ouvertes
et fermées avec une distribution prédéterminée à travers lesdits culbuteurs (34, 35)
par la rotation desdites cames d'admission et d'échappement (21, 22),
un dispositif d'encliquetage pour les axes de culbuteur, dans lequel une partie intermédiaire
d'une plaque d'encliquetage (42), à partir de laquelle un premier bras (42a) et un
second bras (42b) sont étendus de manière solidaire, est fixée d'une manière serrée
à la culasse (3) dans des parties intermédiaires desdits deux axes de culbuteur (32,
33) par un élément fileté (43), et lesdits premier et second bras (42a, 42b) de ladite
plaque d'encliquetage (42) ont des parties de mise en prise (42c, 42d) prévues sur
celle-ci sur un côté avant dans une direction de rotation de serrage dudit élément
fileté (43), respectivement, de sorte que lesdites parties de mise en prise (42c,
42d) sont respectivement amenées en contact avec les parties de mises en prise (32a,
33a) formées dans des attitudes entraînées en rotation de manière opposée sur lesdits
deux axes de culbuteur (32, 33) pour empêcher la rotation desdits axes de culbuteur
(32, 33).