Information
-
Patent Grant
-
6481270
-
Patent Number
6,481,270
-
Date Filed
Thursday, August 31, 200024 years ago
-
Date Issued
Tuesday, November 19, 200221 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Armstrong, Westerman & Hattori, LLP
-
CPC
-
US Classifications
Field of Search
US
- 073 116
- 073 1172
- 073 1173
- 073 1181
- 340 438
-
International Classifications
-
Abstract
There is provided a construction for a cam rotation sensor attaching portion where a cam rotation sensor is attached which detect the rotation angles of camshafts (1, 3) supported on cam holders (lower cam holder 12, upper cam holder 13), the construction being characterized in that portions to be detected (projections 18) are provided on thrust plates (17) fixed to axial ends of the camshafts so as to be brought into abutment with an axial end face (a thrust receiving face 31) of the cam holder for regulating axial positions of the camshafts, and that a sensor (a proximity sensor 23) for detecting the passage of the portions to be detected from an axial direction of the camshafts is attached to a member (a sensor attaching wall 20) which is integrated into the cam holder. According to this construction, since the relative positioning accuracy between the portions to be detected and the sensor attaching portion with respect to the axial direction of the camshafts can easily be improved, a high detection accuracy can be obtained. Moreover, since the sensor and the head cover can be attached to and detached from the cylinder head without affecting each other, the maintenance and servicing properties thereof can be enhanced.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a construction for a cam rotation sensor attaching portion where a cam rotation sensor is attached which detects rotation angles of camshafts supported on cam holders.
2. Description of the Related Art
A fuel injection engine is provided with a sensor for detecting the rotation angle or angles of a camshaft or camshafts for synchronizing the operation timings of injection valves with the rotation angles of the camshaft or camshafts. Japanese Patent Unexamined Publication No. Hei. 4-287841(JP-A-4-287841) discloses a construction in which a cam rotation sensor is attached to a cylinder head cover.
According to the above conventional construction, however, the cylinder head cover is connected to a cylinder head via a seal member comprising a soft rubber material or the like which is interposed between the head cover and the cylinder head, and therefore, the sensor is liable to be affected by vibrations of the engine. Additionally, no high assembling accuracy is required for assembling the head cover to the cylinder head, and therefore, when attempting at improving the positioning accuracy of the sensor relative to the camshaft or camshafts, this leads to another drawback that an extra cost has to be involved.
SUMMARY OF THE INVENTION
The invention was made with a view to solving the problems inherent in the prior art, and a primary object thereof is to provide a construction for a camshaft rotation sensor attaching portion which can facilitate the improvement in positional accuracy relative to camshafts.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a schematic see-through perspective view of an engine to which the invention is applied;
FIG. 2
is a vertical sectional view showing a main part of the invention;
FIG. 3
is a top view showing the main part of the invention with a head cover being removed;
FIG. 4
is an elevational view showing the main part of the invention;
FIG. 5
is a bottom view of a lower cam holder; and
FIG. 6
is a vertical sectional view taken along the line VI—VI of FIG.
5
.
DETAILED DESCRIPTION OF THE PREFERED EMBODIMENT
With a view to attaining the above object, according to an aspect of the invention, there is provide a construction for a cam rotation sensor attaching portion where a cam rotation sensor is attached which detects the rotation angles of camshafts (
1
,
3
) supported on cam holders (lower cam holder
12
, upper cam holder
13
), in the construction of the present invention, portions to be detected (projections
18
) are provided on thrust plates (
17
) fixed to axial ends of the camshafts so as to be brought into abutment with an axial end face (a thrust receiving face
31
) of the cam holder for regulating axial positions of the camshafts, and that a sensor (a proximity sensor
23
) for detecting the passage of the portions to be detected from an axial direction of the camshafts is attached to a member (a sensor attaching wall
20
) which is integrated into the cam holder. According to this construction, since the relative positioning accuracy between the portions to be detected and the sensor attaching portion with respect to the axial direction of the camshafts can easily be improved, a high detection accuracy can be obtained. Moreover, since the sensor and the head cover can be attached to and detached from the cylinder head without affecting each other, the maintenance and servicing properties thereof can be enhanced.
When sensor is attached to cam holder at upper side, cumulative errors tend to be increased while assembling steps and measurements at upper side tend to be increased, therefore the head cover become larger. On the other hand, when the axial end face to which said sensor is attached are provided below the center of said camshafts, it is possible to overcome such an inconvenience.
Referring to the accompanying drawings, the invention will be described in detail below.
FIG. 1
shows an inline four-cylinder DOHC engine to which the invention is applied. Provided for each of the four cylinders on a cylinder head of this engine E are two intake valves driven by an intake camshaft
1
and two exhaust valves
4
driven by an exhaust camshaft
3
. A first valve operation characteristics changing device
5
or a first variable valve timing and lift device for changing in two steps the valve lift and opening angle of the respective valves
2
,
4
in reply to the rotation speed of the camshafts is provided between the intake camshaft
1
and the intake valve
2
and between the exhaust camshaft
3
and the exhaust valve
4
, respectively. Additionally, a second valve operation characteristics changing device
6
or a second variable valve timing and lift device for advancing or retarding the opening and closing timings of the intake valves
2
in a stepless fashion is provided at an axial end of the intake camshaft
1
.
These intake camshaft
1
and exhaust camshaft
3
are interlockingly connected via a chain/sprocket mechanism
10
to a crankshaft
9
to which four pistons
8
are connected via connecting rods
7
and are driven to rotate at a rotating speed of one half the rotating speed of the crankshaft
9
.
Camshaft rotation detecting devices
11
for detecting the rotation angles of the two camshafts
1
,
3
individually are provided at axial ends of those camshafts
1
,
3
which are opposite to other axial ends thereof where the chain/sprocket mechanism
10
is provided. Additionally, these camshaft rotation detecting devices
11
and the second valve operation characteristics changing device
6
are provided at the opposite axial ends of the camshafts, respectively. Thus, since the camshaft rotation detecting devices
11
are provided at the opposite end of the camshafts to the chain/sprocket mechanism
10
and the second valve characteristics changing device
6
is provided at the opposite end of the camshafts to those camshaft rotation detecting devices
11
, a high space utilizing efficiency can be obtained.
As shown in
FIGS. 2
to
4
, the two camshafts
1
,
3
are supported by lower cam holders
12
and upper cam holders
13
which are each vertically divided at a plane which passes through the axial centers of the respective camshafts. Therefore, bearing holes
15
for supporting journal portions
14
of the two camshafts
1
,
3
are also divided into two halves, respectively.
The lower cam holders
12
are joined to an upper surface of the cylinder head
16
, and the upper cam holders
13
are joined to upper surfaces of the lower cam holders
12
, these cam holders
12
,
13
being secured to the cylinder head
16
with four through bolts B
1
.
Thrust plates
17
are integrally connected to the axial ends of the two camshafts
1
,
3
, respectively. These thrust plates
17
are formed into a disc-like shape and are brought into sliding contact with an axial end face of the lower cam holder
12
which is located at a most outboard position or remotest position of the respect camshafts from the chain/sprocket mechanism
10
which is located below the center of the camshafts, whereby the axial movement of the respective camshafts
1
,
3
toward the chain/sprocket mechanism
10
is regulated. In addition, a plurality of projections
18
which axially project are formed on a peripheral portion of each of the thrust plates
17
for generating pulse signals to an electromagnet-type proximity sensor, which will be described later (in this embodiment, four projections are formed on the peripheral portion of each thrust plate at intervals of 90 degrees).
An extended portion
19
is formed on a lowest portion of the lower cam holder
12
that is to be joined to the cylinder head
16
in such a manner as to extend in a direction opposite to the chain/sprocket mechanism. Then, a sensor attaching wall
20
rising vertically is connected to an end of the extended portion
19
which is opposite to the chain/sprocket mechanism. In other words, the lower cam holder
12
and the sensor attaching wall
20
are formed integrally.
Lug pieces
22
are provided so as to project axially from a lowest portion of the sensor attaching wall
20
which is joined to the cylinder head
16
in such a manner as to correspond to bosses
21
provided so as to project from an end face of the cylinder head
16
which is opposite to a pulley end thereof. The sensor attaching wall
20
which is integral with the lower cam holder
12
is integrally connected to the cylinder head by securely screwing bolts B
2
extending through these lug pieces
22
into the bosses
20
.
A proximity sensor
23
is attached to the sensor attaching wall
20
in such a manner as to correspond to the respective intake and exhaust camshafts. Namely, the proximity sensor
23
is attached below the center of the camshafts. This proximity sensor
23
is attached to such a position that a detecting surface
24
thereof can confront distal ends of the projections
18
on the thrust plates
17
, whereby the proximity sensor can catch a magnetic pulse signal generated when the projections
18
pass in front of the detecting surface
24
as the thrust plates
17
rotate, thereby making it possible to detect the rotation angles of the respective camshafts
1
,
3
.
The proximity sensor
23
is fixed to the sensor attaching wall
20
in such a manner that a coil case portion
26
thereof is fitted in a hole
25
formed in the sensor attaching wall
20
and that bolts B extending through stay portions
27
are securely screwed into the sensor attaching wall
20
. Note that the left and right lug pieces
22
for fastening the sensor attaching wall
20
to the cylinder head
16
are connected to each other by a rib
28
passing through the bolt fastened portions of the stay portions
27
of the proximity sensor
23
.
As shown in
FIG. 5
, excess metal of the extended portion
19
for connecting the lower cam holder
12
to the sensor attaching wall
20
is cut away at its joining surface to the cylinder head
16
to reduce the weight of the engine, and openings
29
are also formed in the extended portion
19
in such a manner as to be continuous with oil dropping holes formed in the cylinder head
16
. In addition, a triangular hollow closed cross-sectional portion
30
is integrally formed at a central portion of the extended portion
19
, whereby weight reduction is compatible with high rigidity at a high level. The extended portion
19
is provided so as to be located where the lug pieces
22
of the sensor attaching wall
20
are provided and where the proximity sensor
23
is attached, whereby the originally intended rigidity can be obtained with the lowest possible weight.
As shown in
FIG. 6
, smoothly cut thrust receiving surfaces
31
are formed on the surface of the lower cam holder
12
where the thrust plates
17
are brought into sliding contact.
An upper edge of the sensor attaching wall
20
is formed into a curved surface which is convexed upwardly, and the head cover
34
is placed on the cylinder head
16
with a gasket
33
comprising a rubber material being held between the curved upper edge surface
32
of the sensor attaching wall
20
and portions of the upper surface of the cylinder head
16
which protrude from both sides of the sensor attaching wall
20
and the head cover in order to improve seal-off properties.
Thus, according to the invention, since the projections are provided on the thrust plates which are fixed to the axial ends of the camshafts so as to be brought into abutment with the thrust receiving surfaces of the cam holder for regulating the axial positions of the camshafts and since the proximity sensor for detecting the passage of the projections in the axial direction of the camshafts is attached to the sensor attaching wall which is integral with the cam holder, the relatively positioning accuracy between the thrust plates and the proximity sensor can easily be enhanced, whereby there is provided an advantage that the detection accuracy and stability can be enhanced considerably. Moreover, since the proximity sensor and the head cover can be attached to and detached from the cylinder head without interfering with each other, the high maintenance and servicing properties can be obtained.
In addition, when an axial end face to which the thrust is brought into abutment with and said portion where the sensor is attached are provided below the center of the camshafts, since cumulative errors are prevented form being increased, and measurements at upper side are also prevented form being increased as compared with the case that the proximity sensor is attached to the side of the upper cam holder, therefore it is possible to prevent the head cover from making large.
Claims
- 1. A structure, comprising:a camshaft; a plurality of cam holders for supporting the camshaft; a cam rotation sensor for detecting rotation angles of said camshaft; and a thrust plate being fixed to an axial end of said camshaft, and being brought into abutment with an axial end face of one of said camholders for regulating axial positions of said camshaft, wherein a first plurality of portions to be detected are provided on said thrust plate, said cam rotation sensor opposes to said thrust plate in an axial direction of said camshaft to detect a passage of each of said first plurality of portions from an axial direction of said camshaft, and said cam rotation sensor is directly attached to a member which is integrated into said cam holder.
- 2. The structure according to claim 1, wherein said axial end face to which said thrust plate is brought into abutment with and said member where said sensor is attached to are provided below an axis of said camshaft.
- 3. The structure according to claim 1, further comprising:a cylinder head; and a rib, wherein a second plurality of portions where said member is fastened to said cylinder head are each connected to said rib by a bolt fastened portion.
- 4. The structure according to claim 1, further comprising:a cylinder head; and a rib, wherein a fastened portion where said member is fastened to said cylinder head is connected to a bolt fastened portion by said rib.
- 5. The structure according to claim 1, further comprising:a cylinder head; an extended portion for connecting said cam holder to said member; wherein a surface of said extended portion joining a cylinder head is cut away.
- 6. The structure according to claim 5, further comprising:a triangular hollow closed cross-sectional portion; wherein the triangular hollow closed cross-sectional portion is integrally formed at said extended portion.
- 7. The structure according to claim 6, wherein said extended portion is provided at a center portion of said cam holder.
- 8. The structure according to claim 5, wherein said extended portion is provided at a fastened portion where said member is fastened to said cylinder head.
- 9. The structure according to claim 5, wherein said extended portion is attached to said member.
- 10. The structure according to claim 1, wherein an upper edge surface of said member is formed into a curved surface which is convexed upwardly.
- 11. The structure according to claim 10, further comprising:a gasket; a cylinder head; and a head cover; wherein said head cover is provided on said cylinder head with said gasket being held between the curved surface of said member and said head cover.
- 12. The structure according to claim 1, further comprising:a head cover; wherein said sensor is attached to said member from an outside of said member without being connected to said head cover.
- 13. The structure according to claim 2, further comprising:a cylinder head; and a rib, wherein a second plurality of portions where said member is fastened to said cylinder head are each connected to said rib by a bolt fastened portion.
- 14. The structure according to claim 2, further comprising:a cylinder head; and a rib, wherein a fastened portion where said member is fastened to said cylinder head is connected to a bolt fastened portion.
- 15. The structure according to claim 2, comprises an extended portion for connecting said cam holder to said member where said sensor is attached to, wherein a surface of said extended portion which joints to a cylinder head is cut away.
- 16. The structure according to claim 2, wherein an upper edge surface of said member is formed into a curved surface which is convexed upwardly.
- 17. The structure according to claim 2, further comprising:a head cover; wherein said sensor is attached to said member from an outside of said member without being connected to said head cover.
- 18. The structure according to claim 12, further comprising:a cylinder head; and a rib, wherein a fastened portion where said member is fastened to said cylinder head is connected to a bolt fastened portion by said rib.
- 19. The structure according to claim 12, further comprising:a cylinder head; and an extended portion for connecting said cam holder to said member, wherein a surface of said extended portion joining said cylinder head is cut away.
- 20. The structure according to claim 19, wherein said extended portion is provided for attaching said sensor.
Priority Claims (1)
Number |
Date |
Country |
Kind |
11-250532 |
Sep 1999 |
JP |
|
US Referenced Citations (5)
Number |
Name |
Date |
Kind |
4883027 |
Oikawa et al. |
Nov 1989 |
A |
5627464 |
Shinjo et al. |
May 1997 |
A |
6230675 |
Kobayashi et al. |
May 2001 |
B1 |
6277045 |
Waters Scheuer et al. |
Aug 2001 |
B1 |
6343580 |
Uchida |
Feb 2002 |
B2 |
Foreign Referenced Citations (6)
Number |
Date |
Country |
0 802 323 |
Oct 1997 |
EP |
04-287841 |
Oct 1992 |
JP |
10-176506 |
Jun 1998 |
JP |
11-201011 |
Jul 1999 |
JP |
11-257124 |
Sep 1999 |
JP |
11-311111 |
Nov 1999 |
JP |