Valve timing adjusting device

Details Valve timing adjusting device Valve timing adjusting device

2002-03-11

2003-07-15

Denion, Thomas (Department: 3748)

Internal-combustion engines

Poppet valve operating mechanism

With means for varying timing

C123S090150, C123S090180

Reexamination Certificate

active

06591799

ABSTRACT:

TECHNICAL FIELD
The invention relates to a valve timing control device as a hydraulic actuator mounted on an end of a camshaft, which modifies timing for the opening and closing of both or one of intake and exhaust valves depending on conditions when an engine is operated.
BACKGROUND ART
A vane-equipped or helical piston-equipped valve timing control device is known as a conventional hydraulic valve timing control device. The device is arranged between a timing chain or chain sprocket and a camshaft, the timing chain or chain sprocket defined as a valve-driving system rotating in synchronization with a crankshaft of an engine to drive the camshaft. Oil derived from an oil pump is controllably supplied to the valve timing control device and discharged to outside, by way of an oil control valve (hereafter, referred as an OCV). In this way, it is possible to modify relatively angular displacements of the camshaft with respect to those of the crankshaft. When the angular displacement of the camshaft is variably controlled in advanced or retarded direction, it is possible to optimize timing for the opening and closing of an intake or exhaust valve depending on the number of revolutions and loads of the engine. As a result, it is possible to reduce exhaust gas, to improve power and to increase gas mileage.
An actuator known as the hydraulic valve timing control device includes the vane-equipped and the helical piston-equipped devices. In the vane-equipped device, a plurality of hydraulic chambers is comprised of a vane-equipped rotor and a housing element accommodating the rotor and allowing rotation in a required range. Oil derived from the oil pump is controllably supplied to the hydraulic chambers and discharged to the outside, by way of the OCV. In this way, the hydraulic pressure is changed to shift angular displacement of the camshaft with respect to the crankshaft to advanced or retarded position. On the other hand, the helical piston-equipped device includes a first helical gear formed at a hydraulic piston moved reciprocally in an axial direction due to a hydraulic pressure derived from the OCV and a second helical gear engaged with the first helical gear. These gears are rotated in a required range on the basis of twisting of a helical spline in a housing element. In this way, it is possible to shift angular displacement of the camshaft with respect to the crankshaft to advanced or retarded position. In either case, timing for the opening and closing of an intake or exhaust valve is controlled due to the hydraulic pressure. For example, JP-A-92504/1989, JP-A-121122/1996, JP-A-60507/1997 and JP-A-280018/1997 are known as the former vane-equipped valve timing control device.
Especially, with an exhaust valve timing control device, a driving force derived from a crankshaft of the engine however exerts a force in lo a retarded direction on a camshaft. Moreover, at a time when the engine is started and so on, a pump of the engine is not yet actuated, and the hydraulic pressure is not functioned. Under the conditions, with the conventional device, the camshaft is rotated in the retarded direction when normal advance control cannot be performed due to the force in the same direction. As a result, timing for the opening of the exhaust valve is delayed to lead instability of idling such as a deterioration of starting characteristics of the engine. To solve the problems, a biasing means is arranged in the valve timing control device. Under the conditions of the engine that the hydraulic pressure is not functioned at a time when the engine is started, the biasing means biases the camshaft in the advanced direction against the force in the retarded direction exerted on the camshaft by the driving force derived from the crankshaft. In this way, the engine is started with stability. For example, JP-A-68306/1998 and JP-A-264110/1997 are concerned with the conventional device above.
The former gazette JP-A-68306/1998 discloses a device including a rotor rotatable in synchronization with a camshaft, a biasing means biasing the rotor to rotate a camshaft in an advanced direction with respect to a crankshaft, and a lock mechanism which allows to lock the rotor. With the device, the biasing force of the biasing means is set to be larger than the maximum torque on starting the engine and be larger than an average torque.
The latter gazette JP-A-264110/1997 discloses a device including a vane constituting a plurality of hydraulic chambers formed at inner peripheral sections of the device, and a biasing means biasing a camshaft so as to avoid opening both intake and exhaust valves at the same time. With the device, the biasing force of the biasing means is set to be smaller than a hydraulic pressure supplied to and discharged from the hydraulic chambers. When the hydraulic pressure is reduced, the biasing means also biases the camshaft in advanced direction.
FIG. 1
is a radial or lateral cross sectional view of an internal structure o f a vane-equipped device disclosed in the gazette JP-A-68306/1998. In the drawing, a reference numeral
100
denotes a shoe-equipped housing defined as a driving force transferring member and
101
denotes a vane-equipped rotor defined as the driving force transferring member rotatably arranged in a required range of the shoe-equipped housing
100
. Shoes
100
a
,
100
b
and
100
c
projected inwardly in a radial direction are arranged at an inner peripheral section of the shoe-equipped housing
100
. Vanes
101
a
,
101
b
and
101
c
projected outwardly in the radial direction are arranged at an outer peripheral section of the vane-equipped rotor
101
. The shoes
100
a
,
100
b
and
100
c
and the vanes
101
a
,
101
b
and
101
c
partition a space between the shoe-equipped housing
100
and the vane-equipped rotor
101
into a plurality of rotor-retarding side hydraulic chambers
102
,
103
and
104
and rotor-advance side hydraulic chambers
105
,
106
and
107
. Recesses
108
are formed at the shoes
100
a
,
100
b
and
100
c
facing the rotor-advance side hydraulic chambers
105
,
106
and
107
, respectively. Recesses
109
are formed at the vanes
101
a
,
101
b
and
101
c
facing the rotor-retarding side hydraulic chambers
102
,
103
and
104
, respectively. In each rotor-advance side hydraulic chamber
105
,
106
or
107
, spring members
110
defined as a biasing means are arranged between both recesses
108
and
109
. The shoe-equipped housing
100
is mounted rotatably on an exhaust camshaft corresponding to the exhaust valve and the vane-equipped rotor
101
is fixedly joined at an end of the exhaust camshaft with bolts so as to be rotated in synchronization with the exhaust camshaft.
Next, an operation will be explained.
First, a rotational driving force derived from a crankshaft (not shown) of the engine is transferred to the exhaust camshaft (not shown) by way of a timing chain or timing belt (hereafter, a driving force transferring means, not shown in either of the cases), the shoe-equipped housing
100
and the vane-equipped rotor
101
having a chain sprocket (not shown) or a timing chain (not shown) and defined as a driving force transferring member.
When the valve timing control device is actuated, the vane-equipped rotor
101
is rotated relative to the crankshaft
1
at a required angle due to a hydraulic pressure derived from the OCV (not shown). In this way, since the exhaust camshaft, which is rotated in synchronization with the vane-equipped rotor
101
, is rotated relative to the crankshaft, it is possible to control timing for the opening and closing of the exhaust valves (not shown).
Since the conventional valve timing control device has the construction as described above, there are problems as follows.
(1) That is, as disclosed in the JP-A-68306/1998, a biasing force of the spring
110
, which is defined as the biasing means biasing the camshaft in the advanced direction, is set to be larger than the maximum torque on starting the engine or an average torque. The size of the spring
110
generating such a large biasi

Affiliated with

Also associated with

Rating

Valve timing adjusting device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Valve timing adjusting device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Valve timing adjusting device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3056188