U.S. patent application number 12/688885 was filed with the patent office on 2010-07-22 for piston engine comprising member to cover bottom face of valve head of poppet valve.
Invention is credited to Yasuhito Yaoita.
Application Number | 20100180851 12/688885 |
Document ID | / |
Family ID | 42335948 |
Filed Date | 2010-07-22 |
United States Patent
Application |
20100180851 |
Kind Code |
A1 |
Yaoita; Yasuhito |
July 22, 2010 |
PISTON ENGINE COMPRISING MEMBER TO COVER BOTTOM FACE OF VALVE HEAD
OF POPPET VALVE
Abstract
To achieve high compression ratio and lower temperature of the
exhaust poppet valve in an engine provided with a poppet valve on
an extend part of a combustion chamber outside a main cylinder,
disclosed is a valve cover having a cylindrical side face and upper
face, an compression ring either the cylindrical side face and an
inner wall of the sub cylinder, means to contact closely a bottom
face of a poppet valve and the upper face of the valve cover, the
upper part of the valve cover occupying most part of the combustion
chamber facing with the bottom face, the valve cover moves along
with the poppet valve when the poppet valve is lifted, a
combination of overhead valves and the poppet valve including one
intake valve and one exhaust valve, and total number of the
overhead valve and poppet valve is not less than 3.
Inventors: |
Yaoita; Yasuhito; (Oota-ku,
JP) |
Correspondence
Address: |
Yasuhito Yaoita
6-104, 5-21, Haneda
Oota-ku
144-0043
JP
|
Family ID: |
42335948 |
Appl. No.: |
12/688885 |
Filed: |
January 17, 2010 |
Current U.S.
Class: |
123/188.2 ;
123/196R |
Current CPC
Class: |
F01L 1/252 20130101;
F01L 2001/0537 20130101; F01M 2011/022 20130101; F01L 1/28
20130101; F01L 2001/0535 20130101; F01L 3/20 20130101; F01L 1/46
20130101; F01L 2001/054 20130101 |
Class at
Publication: |
123/188.2 ;
123/196.R |
International
Class: |
F01L 3/00 20060101
F01L003/00; F01M 1/02 20060101 F01M001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 20, 2009 |
JP |
A2009-010427 |
Oct 21, 2009 |
JP |
A2009-241923 |
Claims
1. A piston engine with a member to cover a bottom face of a valve
head of a poppet valve, comprising: a combustion chamber defined
between a piston and a cylinder head, in which the combustion
chamber further extends outside a main cylinder; an inner wall of
the combustion chamber, comprising a first part and a second part,
the first part being a part facing with an upper face of the piston
provided inside the main cylinder, the second part being an
extended part outside the main cylinder a sub cylinder provided
outside the main cylinder; the poppet valve provided on the second
part, the poppet valve being provided with a second drive unit to
drive a stem of the poppet valve, in which a gas passes through a
gap between the poppet valve and a second valve sheet of the poppet
valve when the poppet valve is open; the member to cover the bottom
face of the valve head of the poppet valve, in which the member
reciprocates in the sub cylinder and comprises a cylindrical side
face, in which the valve head is located between the second valve
sheet and the member; a means to make the second valve sheet, the
valve head and the member contact closely one another, in which the
second drive unit and the means drive the poppet valve and the
member integrally, in which the member abuts the bottom face of the
poppet valve; a compression ring provided at a position wedged
between an inner wall of the sub cylinder and the cylindrical side
face of the member; and an overhead valve provided on the first
part, in which a gas passes through the a gap between the overhead
valve and a first valve sheet of the overhead valve when the
overhead valve is open, in which the overhead valve is provided
with a first spring and a first drive unit, wherein a combination
of the overhead valve and the poppet valve includes at least one
intake valve and one exhaust valve, and the total number of the
overhead valve and the poppet valve is not less than 3.
2. A piston engine with a member to cover a bottom face of a valve
head of a poppet valve, comprising: a combustion chamber defined
between a piston and a cylinder head, in which the combustion
chamber further extends outside a main cylinder; an inner wall of
the combustion chamber, comprising a first part and a second part,
the first part being a part facing with an upper face of the piston
provided inside the main cylinder, the second part being an
extended part outside the main cylinder a sub cylinder provided
outside the main cylinder; the poppet valve provided on the second
part, the poppet valve being provided with a second drive unit to
drive a stem of the poppet valve; the member to cover the bottom
face of the valve head of the poppet valve, in which the member
reciprocates in the sub cylinder and comprises a cylindrical side
face, in which the valve head is located between a second valve
sheet of the poppet valve and the member; a means to make the
second valve sheet, the valve head and the member contact closely
one another, in which the second drive unit and the means drive the
poppet valve and the member integrally, in which the member abuts
the bottom face of the poppet valve; a compression ring provided at
a position wedged between an inner wall of the sub cylinder and the
cylindrical side face of the member; and an overhead valve provided
on the first part, in which a gas passes through the a gap between
the overhead valve and a first valve sheet of the overhead valve
when the overhead valve is open, in which the overhead valve is
provided with a first spring and a first drive unit, wherein a
combination of the overhead valve and the poppet valve includes at
least one intake valve and one exhaust valve, a plurality of the
poppet valve are provided on the second part, all of the plurality
of poppet valves provided on the second part being exhaust poppet
valves, and at least one of the overhead valve provided on the
first part is an intake valve.
3. The piston engine with the member according to claim 1, wherein
a plurality of the poppet valve is provided on the second part, all
of the plurality of poppet valves provided on the second part being
intake poppet valves, and at least one of the overhead valve
provided on the first part is an exhaust valve.
4. A piston engine with a member to cover a bottom face of a valve
head of a poppet valve, comprising: a combustion chamber defined
between a piston and a cylinder head, in which the combustion
chamber further extends outside a main cylinder; an inner wall of
the combustion chamber, comprising a first part and a second part,
the first part being a part facing with an upper face of the piston
provided inside the main cylinder, the second part being an
extended part outside the main cylinder; a sub cylinder provided
outside the main cylinder; the poppet valve provided on the second
part, the poppet valve being provided with a second drive unit to
drive a stem of the poppet valve, in which a gas passes through a
gap between the poppet valve and a second valve sheet of the poppet
valve when the poppet valve is open; the member to cover the bottom
face of the valve head of the poppet valve, in which the member
reciprocates in the sub cylinder and comprises a cylindrical side
face, in which the valve head is located between the second valve
sheet of the poppet valve and the member; a means to make the
second valve sheet, the valve head and the member contact closely
one another, in which the second drive unit and the means drive the
poppet valve and the member integrally, in which the member abuts
the bottom face of the poppet valve; a compression ring provided at
a position between an inner wall of the sub cylinder and the
cylindrical side face of the member; and at least one or more
overhead valve provided on the first part, all of the overhead
valve provided on the first part being an intake overhead valve, in
which the overhead valve is provided with a first spring and a
first drive unit, wherein the total number of the overhead valve
and the poppet valve is not less than 3, and an exhaust poppet
valve is provided on the second part.
5. The piston engine with the member according to claim 1, wherein
one end of the sub cylinder is located adjacent to the second valve
sheet, a whole circumference of the cylindrical side face of the
member adjacent to the poppet valve is sectioned into two half
circumferences by a line which is perpendicular to a line
connecting a central axis of the main cylinder and a central axis
of the sub cylinder intersecting at the central axis of the sub
cylinder, the two half circumferences are referred to as a first
half circumference which is close to the central axis of the main
cylinder and a second half circumference which is away from the
central axis of the main cylinder, the cylindrical side face of the
member adjacent to the poppet valve is sectioned into two half
surrounding faces, the two half surrounding faces are a first half
surrounding face having the first half circumference and a second
half surrounding face having the second half circumference, a part
adjacent to the second valve sheet of the sub cylinder faces with
the second half surrounding face, a fixed wall, which is located
outside the combustion chamber extended outside the main cylinder,
is formed adjacent to an inner wall facing with the second half
surrounding face of the sub cylinder, the sub cylinder comprises a
opening in a vicinity of the one end of the sub cylinder, the
piston engine further comprises: a first gas path provided between
the second valve sheet and outside of the engine; and a second gas
path which communicates an inner space of the main cylinder and the
first gas path in a short distance when the poppet valve is open,
the second gas path including the opening, and the opening faces
with the first half surrounding face.
6. The piston engine with the member according to claim 2, wherein
one end of the sub cylinder is located adjacent to the second valve
sheet, a whole circumference of the cylindrical side face of the
member adjacent to the poppet valve is sectioned into two half
circumferences by a line which is perpendicular to a line
connecting a central axis of the main cylinder and a central axis
of the sub cylinder intersecting at the central axis of the sub
cylinder, the two half circumferences are referred to as a first
half circumference which is close to the central axis of the main
cylinder and a second half circumference which is away from the
central axis of the main cylinder, the cylindrical side face of the
member adjacent to the poppet valve is sectioned into two half
surrounding faces, the two half surrounding faces are a first half
surrounding face having the first half circumference and a second
half surrounding face having the second half circumference, a part
adjacent to the second valve sheet of the sub cylinder faces with
the second half surrounding face, a fixed wall, which is located
outside the combustion chamber extended outside the main cylinder,
is formed adjacent to an inner wall facing with the second half
surrounding face of the sub cylinder, the sub cylinder comprises a
opening in a vicinity of the one end of the sub cylinder, the
piston engine further comprises: a first gas path provided between
the second valve sheet and outside of the engine; and a second gas
path which communicates an inner space of the main cylinder and the
first gas path in a short distance when the poppet valve is open,
the second gas path including the opening, and the opening faces
with the first half surrounding face.
7. The piston engine with the member according to claim 3, wherein
one end of the sub cylinder is located adjacent to the second valve
sheet, a whole circumference of the cylindrical side face of the
member adjacent to the poppet valve is sectioned into two half
circumferences by a line which is perpendicular to a line
connecting a central axis of the main cylinder and a central axis
of the sub cylinder intersecting at the central axis of the sub
cylinder, the two half circumferences are referred to as a first
half circumference which is close to the central axis of the main
cylinder and a second half circumference which is away from the
central axis of the main cylinder, the cylindrical side face of the
member adjacent to the poppet valve is sectioned into two half
surrounding faces, the two half surrounding faces are a first half
surrounding face having the first half circumference and a second
half surrounding face having the second half circumference, a part
adjacent to the second valve sheet of the sub cylinder faces with
the second half surrounding face, a fixed wall, which is located
outside the combustion chamber extended outside the main cylinder,
is formed adjacent to an inner wall facing with the second half
surrounding face of the sub cylinder, the sub cylinder comprises a
opening in a vicinity of the one end of the sub cylinder, the
piston engine further comprises: a first gas path provided between
the second valve sheet and outside of the engine; and a second gas
path which communicates an inner space of the main cylinder and the
first gas path in a short distance when the poppet valve is open,
the second gas path including the opening, and the opening faces
with the first half surrounding face.
8. The piston engine with the member according to claim 4, wherein
one end of the sub cylinder is located adjacent to the second valve
sheet, a whole circumference of the cylindrical side face of the
member adjacent to the poppet valve is sectioned into two half
circumferences by a line which is perpendicular to a line
connecting a central axis of the main cylinder and a central axis
of the sub cylinder intersecting at the central axis of the sub
cylinder, the two half circumferences are referred to as a first
half circumference which is close to the central axis of the main
cylinder and a second half circumference which is away from the
central axis of the main cylinder, the cylindrical side face of the
member adjacent to the poppet valve is sectioned into two half
surrounding faces, the two half surrounding faces are a first half
surrounding face having the first half circumference and a second
half surrounding face having the second half circumference, a part
adjacent to the second valve sheet of the sub cylinder faces with
the second half surrounding face, a fixed wall, which is located
outside the combustion chamber extended outside the main cylinder,
is formed adjacent to an inner wall facing with the second half
surrounding face of the sub cylinder, the sub cylinder comprises a
opening in a vicinity of the one end of the sub cylinder, the
piston engine further comprises: a first gas path provided between
the second valve sheet and outside of the engine; and a second gas
path which communicates an inner space of the main cylinder and the
first gas path in a short distance when the poppet valve is open,
the second gas path including the opening, and the opening faces
with the first half surrounding face.
9. The piston engine with the member according to claim 1, wherein
a stroke length of the piston is not shorter than a diameter of the
piston.
10. The piston engine with the member according to claim 2, wherein
a stroke length of the piston is not shorter than a diameter of the
piston.
11. The piston engine with the member according to claim 3, wherein
a stroke length of the piston is not shorter than a diameter of the
piston.
12. The piston engine with the member according to claim 4, wherein
a stroke length of the piston is not shorter than a diameter of the
piston.
13. The piston engine with the member according to claim 5, wherein
a stroke length of the piston is not shorter than a diameter of the
piston.
14. The piston engine with the member according to claim 6, wherein
a stroke length of the piston is not shorter than a diameter of the
piston.
15. The piston engine with the member according to claim 7, wherein
a stroke length of the piston is not shorter than a diameter of the
piston.
16. The piston engine with the member according to claim 8, wherein
a stroke length of the piston is not shorter than a diameter of the
piston.
17. The piston engine with the member according to claim 1, further
comprising: a spray valve to spray oil toward a back face of a part
adjacent to the poppet valve of the member; and a third spring
abutting the back face.
18. The piston engine with the member according to claim 2, further
comprising: a spray valve to spray oil toward a back face of a part
adjacent to the poppet valve of the member; and a third spring
abutting the back face.
19. The piston engine with the member according to claim 3, further
comprising: a spray valve to spray oil toward a back face of a part
adjacent to the poppet valve of the member; and a third spring
abutting the back face.
20. The piston engine with the member according to claim 4, further
comprising: a spray valve to spray oil toward a back face of a part
adjacent to the poppet valve of the member; and a third spring
abutting the back face.
21. The piston engine with the member according to claim 5, further
comprising: a spray valve to spray oil toward a back face of a part
adjacent to the poppet valve of the member; and a third spring
abutting the back face.
22. The piston engine with the member according to claim 6, further
comprising: a spray valve to spray oil toward a back face of a part
adjacent to the poppet valve of the member; and a third spring
abutting the back face.
23. The piston engine with the member according to claim 7, further
comprising: a spray valve to spray oil toward a back face of a part
adjacent to the poppet valve of the member; and a third spring
abutting the back face.
24. The piston engine with the member according to claim 8, further
comprising: a spray valve to spray oil toward a back face of a part
adjacent to the poppet valve of the member; and a third spring
abutting the back face.
25. The piston engine with the member according to claim 1, wherein
the sub cylinder comprises a groove for the compression ring, and
the compression ring is disposed on the groove.
26. The piston engine with the member according to claim 2, wherein
the sub cylinder comprises a groove for the compression ring, and
the compression ring is disposed on the groove.
27. The piston engine according to claim 4, wherein the sub
cylinder comprises a groove for the compression ring, and the
compression ring is disposed on the groove.
28. The piston engine with the member according to claim 1, wherein
a face contacting with the poppet valve of the member is a convex
curve, a face contacting with the member of the poppet valve is a
concave curve, and the two faces have a same curvature, the member
and the poppet valve are not integrally formed, and the member and
the valve head of the poppet valve contact with each other.
29. The piston engine with the member according to claim 5, wherein
a face contacting with the poppet valve of the member is a convex
curve, a face contacting with the member of the poppet valve is a
concave curve, and the two faces have a same curvature, the member
and the poppet valve are not integrally formed, and the member and
the valve head of the poppet valve contact with each other.
30. The piston engine with the member according to claim 6 wherein
the compression ring comprises: an upper compression ring provided
on an inner wall of the sub cylinder near the combustion chamber;
and a lower compression ring provided on the cylindrical side wall
of the member, wherein the upper compression ring is provided
between the lower compression ring and the combustion chamber, an
upper end of the lower compression ring is located adjacent to a
lower end of the upper compression ring when the poppet valve is
closed, the piston engine further comprises a oil ring provided on
the cylindrical side face of the member, and the lower compression
ring is provided between the oil ring and the upper compression
ring.
31. The piston engine with the member according to claim 7 wherein
the compression ring comprises: an upper compression ring provided
on an inner wall of the sub cylinder near the combustion chamber;
and a lower compression ring provided on the cylindrical side wall
of the member, wherein the upper compression ring is provided
between the lower compression ring and the combustion chamber, an
upper end of the lower compression ring is located adjacent to a
lower end of the upper compression ring when the poppet valve is
closed, the piston engine further comprises a oil ring provided on
the cylindrical side face of the member, and the lower compression
ring is provided between the oil ring and the upper compression
ring.
32. The piston engine with the member according to claim 8 wherein
the compression ring comprises: an upper compression ring provided
on an inner wall of the sub cylinder near the combustion chamber;
and a lower compression ring provided on the cylindrical side wall
of the member, wherein the upper compression ring is provided
between the lower compression ring and the combustion chamber, an
upper end of the lower compression ring is located adjacent to a
lower end of the upper compression ring when the poppet valve is
closed, the piston engine further comprises a oil ring provided on
the cylindrical side face of the member, and the lower compression
ring is provided between the oil ring and the upper compression
ring.
33. The piston engine with the member according to claims 1,
wherein the means is a device to bias the member toward the second
valve sheet, the device to bias the member toward the second valve
sheet is a third spring abutting the member, and the third spring
does not face with a space of the combustion chamber.
34. The piston engine with the member according to claims 5,
wherein the means is a device to bias the member toward the second
valve sheet, the device to bias the member toward the second valve
sheet is a third spring abutting the member, and the third spring
does not face with a space of the combustion chamber.
35. The piston engine with the member according to claims 6,
wherein the means is a device to bias the member toward the second
valve sheet, the device to bias the member toward the second valve
sheet is a third spring abutting the member, and the third spring
does not face with a space of the combustion chamber.
36. The piston engine with the member according to claims 7,
wherein the means is a device to bias the member toward the second
valve sheet, the device to bias the member toward the second valve
sheet is a third spring abutting the member, and the third spring
does not face with a space of the combustion chamber.
37. The piston engine with the member according to claims 8,
wherein the means is a device to bias the member toward the second
valve sheet, the device to bias the member toward the second valve
sheet is a third spring abutting the member, and the third spring
does not face with a space of the combustion chamber.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a piston engine comprising
a member to cover a bottom face of a valve head of a poppet valve.
When the combustion chamber extends outside the main cylinder, the
member occupies a space facing with the bottom face of the poppet
valve provided outside a main cylinder in a combustion chamber.
[0003] 2. Description of the Related Art
[0004] The suction resistance and exhaust resistance of a four
cycle engine are high when it rotates at high speed. The suction
lifts in this engine are extremely small in the initial stages of
the periods when the suction valve is open. The initial stages are
shorter when the engine rotates at a higher speed. This restricts
the inflow of suction gas. As a result, in the initial stages of
the periods when the suction valve is open, the pressure in the
cylinder is lower than the pressure at the back of the piston.
[0005] Under this condition, the piston keeps moving downward
against the pressure on it. As a result, the negative work
increases. This increases the loss caused by the suction
resistance, so that the torque lowers.
[0006] FIG. 14 shows the engine performance curves shown on page 90
of No. 434 issued in November, 1995 of a magazine entitled
"Internal Combustion Engine" published by Sankaido. With reference
to FIG. 14, the torque of a four cycle engine is lower than the
maximum torque points L1 and L2 on torque curves when the engines
rotate at speeds higher than those for these points.
[0007] The exhaust lifts in a four cycle engine are extremely
smaller in the initial stage of the period when the exhaust valve
is open until the piston reaches the bottom dead point of each
exhaust stroke than in the middle stage of this period.
Consequently, when the engine rotates at high speed, the pressure
created in the cylinder when the piston is at the bottom dead point
is high. As a result, just after the piston leaves the bottom dead
point, the exhaust resistance causes a great loss.
[0008] FIG. 15 shows the side valve engine disclosed in Patent
document 1. The main combustion chamber 127 of this engine has an
extension outside the cylinder. This makes it possible to fit
another suction valve and another exhaust valve that face the top
of the piston.
[0009] The space between the suction and exhaust valves is narrowed
to make the combustion chamber compact in Patent document 1.
[0010] However, the volume of the main combustion chamber is
increased by the space between the wall fitted with a side valve
and the surface facing the wall. The volume of this space increases
with the lift of the side valve. Consequently, the combustion
chamber having a suction valve facing the top of the piston and a
side valve cannot have a high combustion ratio, so that the engine
efficiency is low.
[0011] FIG. 17 shows a side valve engine described in patent
document 3. In FIG. 17, there is a space of a combustion chamber
between an edge of a guide hole facing with the combustion chamber
and a valve sheet for the intake valve. According to FIG. 17, the
combustion chamber extends outside the volume changing member 117
in a view observing from the central axis of the cylinder toward
the volume changing member. The volume of the combustion chamber
increases by this extended portion.
[0012] Reference numeral 118 denotes the guide hole. Reference
numeral 113 denotes the intake valve. Reference numeral 117 denotes
the volume changing member. Reference numeral 127 denotes the
combustion chamber.
[0013] The side valve internal combustion engine of patent document
3 is provided with a pair of an intake and exhaust valves provided
at the lateral periphery of the cylinder. Therefore, the total area
of the pair of intake and exhaust valves of the side valve internal
combustion engine of patent document 3 is smaller than that of an
engine provided with four valves at a wall facing with an upper
face of a piston in the wall of the combustion chamber.
[0014] In the side valve internal combustion engine of patent
document 3, a part protruding into the combustion chamber of the
volume changing member is heated to high temperature by the
combustion gas while the intake valve is closed.
[0015] Combustion occurs intermittently in a piston engine. An
inner wall of a combustion chamber is cooled by intake gas in a
piston engine. In a spark-ignition engine, mixture gas thus forms a
quench zone along with an inner wall of a combustion chamber. This
quench zone prevents high heat from flowing to the inner wall of
the combustion chamber.
[0016] When the exhaust poppet valve opens, both a bottom face of a
valve head of the exhaust poppet valve and an upper face facing
with a gas passage of the valve head are exposed to the combustion
gas. The temperature of the exhaust poppet valve thus gets high.
When the piston is under high load, the quench zone is poorly
formed along with the bottom face of the valve head of the exhaust
poppet valve. Therefore, the mixture zone along with the bottom
face self-ignites. When the amount of self-ignited mixture
increases, the quench zone is broken also at a part facing with the
inner wall of the combustion chamber other than the bottom face. As
a result, knocking occurs.
[0017] FIG. 16 shows the engine of patent document 2.
[0018] When the sliding valve shown in the third aspect of patent
document 2 is used as an exhaust valve, both upper and lower faces
of a first compression ring of the sliding valve are exposed to the
combustion gas at the beginning of exhaust strokes. Reference
numeral 8 denotes the first compression ring. Thus, the first
compression ring is heated to the ignition temperature of the
lubricant or more. The first compression ring is then seized up.
The engine of Japanese patent application No. 2008-120801 comprises
a sub cylinder outside the main cylinder.
[0019] If the strokes of the piston are longer than its diameter,
the combustion gas conversion efficiency is high, but the suction
efficiency is low when the engine rotates at high speed. The low
suction efficiency leads to low torque. If the piston strokes are
shorter than the piston diameter, the suction efficiency is high
when the engine rotates at high speed, but the combustion gas
conversion efficiency is low.
[0020] Therefore, long strokes of the pistons of conventional spark
ignition engines have been incompatible with torque increases that
may be caused when the engines rotate at high speed.
[0021] Patent document 1: Japanese Patent Application Publication
No. 2000-282814 (JP2000-282814A)
[0022] Patent Document 2: Japanese Patent Application No.
2008-120801, Japanese Patent No. 4230529
[0023] Patent document 3: Japanese Patent Application Publication
No. 2001-355470
SUMMARY OF THE INVENTION
[0024] A first object is to raise compression ratio of an engine
which comprises a valve on a wall of an extended part of a
combustion chamber outside a main cylinder.
[0025] A second object is to lower a temperature of the valve when
it is used as an exhaust valve.
[0026] A third object is to improve fuel efficiency of a piston
engine.
[0027] Hereinafter described is a structure of a piston engine
according to a first aspect of the present invention.
[0028] The piston engine of the present invention comprises a
cylinder head, a cylinder block, a main cylinder, a piston, a sub
cylinder, an overhead valve and a poppet valve. A member to cover a
bottom face of a valve head of the poppet valve is provided.
[0029] The piston reciprocates in the main cylinder. A combustion
chamber is defined between the piston and the cylinder head. The
combustion chamber further extends outside the main cylinder. An
inner wall of the combustion chamber comprises a first part and a
second part. The first part represents a part of the inner wall
which faces with an upper face of the piston. The second part
represents the inner wall of an extended part outside the main
cylinder. The sub cylinder is provided outside the main
cylinder.
[0030] The poppet valve is provided on the second part of the inner
wall. The poppet valve is provided with a second drive unit to
drive a stem of the poppet valve. When the poppet valve is open,
gas passes through between the poppet valve and a second valve
sheet of the poppet valve.
[0031] The member reciprocates in the sub cylinder, and includes a
cylindrical side face.
[0032] The valve head positions between the second valve sheet and
the member.
[0033] Means to contact the second valve sheet, the member and the
valve head intimately with one another is provided. The means may
be a combination of the poppet valve integrally formed with the
member and a device to shift the member toward the second valve
sheet, or may be a device to bias the member toward the second
valve sheet.
[0034] The device to shift the member toward the second valve sheet
may be one of a third spring provided with abutting the member, a
pneumatic unit provided with abutting the member, a hydraulic unit
provided with abutting the member and a second spring provided with
abutting the stem of the poppet valve.
[0035] The device to bias the member toward the second valve sheet
may be one of a third spring provided with abutting the member, a
pneumatic unit provided with abutting the member and a hydraulic
unit provided with abutting the member.
[0036] The second drive unit and the means drive the poppet valve
and the member integrally.
[0037] A compression ring is provided at a position wedged between
an inner wall of the sub cylinder and the cylindrical side face of
the member.
[0038] The member is located with abutting the bottom face of the
poppet valve.
[0039] The overhead valve is provided on the first part of the
inner wall. The overhead valve is provided with a spring and a
first drive unit. When the overhead valve is open, gas passes
through between the overhead valve and a valve sheet of the
overhead valve. When the poppet valve is open, gas passes through
between the poppet valve and a second valve sheet of the poppet
valve. The gas is either intake gas flowing into the combustion
chamber or combustion gas flowing out from the combustion
chamber.
[0040] A combination of the overhead valve and the poppet valve
includes at least one intake valve and one exhaust valve.
[0041] The total number of the overhead valve and poppet valve is
not less than 3.
[0042] About a structure of a piston engine according to a second
aspect of the present invention, only the difference from the first
aspect is described below.
[0043] The sub cylinder is provided at a position where one end
thereof is located adjacent to the second valve sheet.
[0044] The whole circumference of the cylindrical side face of the
member adjacent to the poppet valve is sectioned into two half
circumferences by a line which is perpendicular to a line
connecting the central axis of the main cylinder to the central
axis of the sub cylinder intersecting at the central axis of the
sub cylinder.
[0045] The two half circumferences are referred to as a first half
circumference which is close to the central axis of the main
cylinder and a second half circumference which is away from the
central axis of the main cylinder.
[0046] The cylindrical side face of the member adjacent to the
poppet valve is sectioned into two half surrounding faces. The two
half surrounding faces are a first half surrounding face having the
first half circumference and a second half surrounding face having
the second half circumference.
[0047] A part adjacent to the second valve sheet of the sub
cylinder faces with the second half surrounding face.
[0048] A fixed wall, which is located outside the combustion
chamber extended outside the main cylinder, is formed adjacent to
the inner wall facing with the second half surrounding face of the
sub cylinder.
[0049] An opening of the sub cylinder is provided in the vicinity
of the one end of the sub cylinder.
[0050] A first gas path is provided between the second valve sheet
and outside of the engine. A second gas path is provided which
communicates a space inside the main cylinder and the first gas
path in a short distance when the poppet valve is open, and the
second gas path includes the opening.
[0051] The opening faces with the first half surrounding face.
[0052] According to the piston engine of the second aspect, the
area heated by the combustion gas is reduced in the cylindrical
side face of the valve cover 7 compared to that of the engine of
patent document 3, and thus the amount of thermal loss is reduced
in this engine. As a result, the third object is achieved in the
second aspect.
[0053] About a structure of a piston engine according to a third
aspect of the present invention, only the difference from the first
aspect is described below.
[0054] According to the engines of the first and second aspects, a
stroke length of the piston is not shorter than a diameter of the
piston.
[0055] According to the piston engine of the third aspect
conversion efficiency of the combustion gas is improved compared to
short stroke engines. Also, decrease of intake efficiency is
improved, which occurs in long stroke engines rotating at high
speed. As a result, it becomes possible to strike the improvement
of conversion efficiency and increase of torque in balance. Thus,
the third object is achieved in the third aspect.
[0056] The piston engines according to the three aspects of the
present invention may be spark-ignition engines or
compression-ignition engines, and the spark-ignition engines may be
2-stroke engines or 4-stroke-engines. When the engine of the
invention is a spark-ignition engine, a spark plug may be provided
anywhere on the wall of the combustion chamber.
[0057] According to the engines of the three aspects of the present
invention, the volume of the combustion chamber reduces by the
volume of an upper part of the member which protrudes into the
space in the combustion chamber which would face with the closed
poppet valve if the member were not provided. Therefore, the
engines can achieve high compression ratio of the combustion
chamber. Thus, the first object is achieved.
[0058] Further, a total area of the intake and exhaust valves of
the engine according to the three aspects of the present invention
is larger than engines provided with overhead valves only in a main
cylinder. Therefore, intake and exhaust resistance reduces
especially when rotating at high speed. Output power of the engine
of the invention thus can increase.
BRIEF DESCRIPTION OF THE DRAWINGS
[0059] FIGS. 1 to 3 are views showing the first embodiment,
wherein:
[0060] FIG. 2 is a view when the poppet valve is open.
[0061] FIGS. 4 to 7 are views showing modifications of the first
embodiment.
[0062] FIGS. 8 and 9 are views showing the second embodiment.
[0063] FIGS. 10 to 13 are views showing embodiments to improve the
first to fifth embodiments.
[0064] FIGS. 14 to 17 are views showing prior art, wherein:
[0065] FIG. 14 is a graph showing power output and torque of the
3RZ-FE engine and 22R-E engine;
[0066] FIG. 15 is a view of the combustion chamber of Japanese
patent application publication No. 2000-282814;
[0067] FIG. 16 is a view of the engine according to the third
aspect of Japanese patent application No. 2008-120801; and
[0068] FIG. 17 is FIG. 2 of Japanese patent application publication
No. 2001-355470.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0069] A first embodiment will be described.
[0070] The first embodiment is included in the first aspect.
[0071] A piston engine shown in FIGS. 1 and 2 comprises a cylinder
head 5, a cylinder block 6, a main cylinder 1, a piston 26, a sub
cylinder 4, overhead valves 25A and 25B, and a poppet valve 2.
[0072] The piston 26 reciprocates in the main cylinder 1. A
combustion chamber 27 is defined between the cylinder head 5 and
the piston 26. The combustion chamber 27 further extends outside
the main cylinder 1. An inner wall of the combustion chamber 27
comprises a first part and a second part. The first part represents
the inner wall which faces with an upper face of the piston 26. The
second part represents the inner wall of the extended part outside
the main cylinder 1.
[0073] The combustion chamber 27 may extend both right and left
sides outside the main cylinder 1.
[0074] The sub cylinder 4 is installed in the cylinder block 6
which locates outside the main cylinder 1.
[0075] The overhead valves 25A and 25B are provided in the first
part which faces with the upper face of the piston 26. When the
overhead valves 25A and 25B are open, gas passes through gaps
between the overhead valves 25A and 25B and valve sheets of
them.
[0076] The overhead valves 25A and 25B are provided with springs
29A and 29B respectively. The overhead valves 25A and 25B are
respectively provided with cams 28A and 28B as a first drive unit
to lift the overhead valves 25A and 25B.
[0077] When the overhead valve 25A is configured as an intake valve
and the overhead valve 25B is configured as an exhaust valve, the
overhead valve 25A opens by the cam 28A during an intake stroke of
the piston 26 and the overhead valve 25B opens by the cam 28B
during an exhaust stroke of the piston 26.
[0078] The cams 28A and 28B of the overhead valves 25A and 25B may
be replaced with electromagnetic units or hydraulic units.
[0079] The poppet valve 2 is provided on the second part extended
outside the main cylinder 1. A plurality of poppet valves 2 may be
provided in the second part. A bottom face 3 of the poppet valve 2
denotes a bottom face of a valve head of the poppet valve 2. At the
periphery of an upper face of the valve head, the poppet valve 2
has a face which intimately contacts with a second valve sheet 16
of the poppet valve 2 when the poppet valve 2 is closed. An opening
is provided inside the second valve sheet 16 of the poppet valve 2,
and the opening communicates to outside of the engine. When the
poppet valve 2 is closed, the valve head of the poppet valve 2
positions at the opening. The poppet valve 2 is provided with a cam
30 which abuts the poppet valve 2.
[0080] When the poppet valve 2 is open, intake or exhaust gas
passes though a gap between the poppet valve 2 and the second valve
sheet 16. That is, the poppet valve 2 can be used as either an
intake valve or an exhaust valve.
[0081] When the poppet valve 2 is used as an intake valve, it opens
by the cam 30 during an suction stroke of the piston 26.
[0082] When the poppet valve 2 is used as an exhaust valve, it
opens by the cam 30 during an exhaust stroke of the piston 26.
[0083] The cam 30 functions as a second drive unit to lift the
poppet valve 2.
[0084] The cam 30 of the poppet valve 2 may be replaced with an
electromagnetic unit or a hydraulic unit.
[0085] Three examples of providing the intake and exhaust valves
will be described. The three examples relate to the overhead valves
25A and 25B and poppet valve 2.
[0086] The features shown in the three examples are not disclosed
in patent document 3.
[0087] In the three examples, the total number of the overhead
valve and the poppet valve is not less than 3.
[0088] In the first example, a plurality of exhaust poppet valves
are provided on the second part, and the poppet valves provided on
the second part are limited to exhaust poppet valves. This feature
is not disclosed in patent document 3. At least one overhead intake
valve is provided on the first part.
[0089] Therefore, in the first example, it becomes possible to
increase the number and the area of the exhaust poppet valves
provided on the second part compared to the engines of patent
documents 1 and 3.
[0090] When the exhaust poppet valves are open, the bottom faces 3
are covered with the upper face 8 of the valve cover 7 described
below and the bottom faces 3 do not contact with the combustion
gas. The temperature of the exhaust poppet valves thus does not
rise high compared to the exhaust valve of the patent document 1.
It is possible to lower the temperature of only the exhaust poppet
valves provided on the second part. Therefore, the second object is
partly achieved in this engine.
[0091] The upper and lower faces of the compression ring 9 are not
exposed to the combustion gas at a time. Therefore, the temperature
of the compression ring 9 does not rise high compared to the third
aspect of patent document 2 where the sliding valve is used as an
exhaust valve.
[0092] In the first example, the amount of the combustion gas
passing through each poppet valve provided on the second part is
reduced compared to the exhaust poppet valve of patent document 3,
and the highest temperature of the plurality of exhaust poppet
valves becomes lower. Therefore, resistance to knocking of the
first example is improved compared to patent document 3.
[0093] The second example will be described.
[0094] A plurality of intake poppet valves are provided on the
second part, and the poppet valves provided on the second part is
limited to intake valves. This feature is not disclosed in patent
document 3. At least one exhaust overhead valve is provided on the
first part. Therefore, in the second example, it becomes possible
to increase the number and the area of the intake valves compared
to the engines of patent documents 1 and 3.
[0095] The third example will be described with reference to FIG.
3.
[0096] One or more overhead valve is provided on the first part of
the inner wall of the combustion chamber 27, and all overhead valve
provided in the first part is the intake poppet valve 33. The
exhaust poppet valve 34 is provided on the second part extended
outside the main cylinder 1. It becomes possible to prevent the
temperature of the exhaust poppet valve 34 from rising high
according to the same ground described in the first example for
explaining the temperature of the exhaust poppet valves. The
exhaust valve 34 does not lower filling rate of intake. Therefore,
the second object is perfectly achieved in this engine. The
temperature of the intake valve 33 does not rise high.
[0097] According to this feature, the wall of the combustion
chamber does not have in any part a higher temperature than the
exhaust valves described in the description of the related art.
Therefore, when the piston is under a high load, a quench zone is
formed along with the entire wall of the combustion chamber.
[0098] As a result, in the case of a spark-ignition engine,
resistance to knocking is improved compared to the engines of
patent documents 1 and 3. Then, it becomes possible to increase a
compression ratio of this engine, and thermal efficiency of this
engine is thus improved. Therefore, the third object is achieved in
this engine.
[0099] Piston engines can operate at least with a combination of
one intake valve and one exhaust valve. Therefore, when a
combination of the overhead valves 25A and 25B and poppet valve 2
includes at least one intake valve and one exhaust valve, the
piston engine of the first embodiment can operate whether the other
valve than the combination is configured as an intake valve or an
exhaust valve.
[0100] The total number of the overhead valves and the poppet valve
is not less than 3.
[0101] It is described that the embodiment comprises the two
overhead valves 25A and 25B. However, when the total number of the
overhead valve and poppet valve is not less than 3, the number of
the overhead valve may be any number more than one. Also, when the
total number of the overhead valve and poppet valve is not less
than 3, the configuration of intake and exhaust valves may be
modified differently from the above three examples.
[0102] The piston engine of the first embodiment comprises a valve
cover 7.
[0103] The valve cover 7 reciprocates in the sub cylinder 4. The
valve cover 7 covers the bottom face 3 of the poppet valve 2. The
valve cover 7 positions with its upper part being protruded into an
inner space of the combustion chamber 27.
[0104] The valve cover 7 comprises a cylindrical side face, an
upper face and a back face. The back face abuts a spring 12. A
lower part of the cylindrical side face faces with an inner wall of
the sub cylinder 4.
[0105] The valve cover 7 and poppet valve 2 are driven by the cam
30 which lifts the poppet valve 2. The cam 30 functions as a second
drive unit.
[0106] A central axis of a stem of the poppet valve 2 is identical
to or approximately parallel to a central axis of the sub cylinder
4. Therefore, when the cam 30 lifts the poppet valve 2, the valve
cover 7 moves along with the poppet valve 2 and the lower part of
the valve cover 7 accordingly moves inside the sub cylinder 4.
Therefore, the cam 30 of the poppet valve 2 also functions as a
drive unit to lift the valve cover 7.
[0107] A space is defined between the valve sheet 16 of the poppet
valve 2 and an upper end 10 of the sub cylinder 4. The upper end 10
faces with the space of the combustion chamber 27.
[0108] A ring groove for a compression ring 9 is provided on the
cylindrical side face of the valve cover 7. The compression ring 9
is disposed to this ring groove. This feature is not shown in
patent document 3.
[0109] When the poppet valve 2 is closed, the compression ring 9 is
wedged between the inner wall of the sub cylinder 4 and the ring
groove. Since the compression ring 9 is wedged between the inner
wall of the sub cylinder 4 and the cylindrical side face of the
valve cover 7 when the poppet valve 2 is closed, the combustion
chamber 27 is sealed with the compression ring 9 so that combustion
gas does not leak from the combustion chamber 27 through the gap
between the valve cover 7 and the inner wall of the sub cylinder 4
into a space where the valve cover 7 does not occupy in the sub
cylinder 4.
A spring 12 for the valve cover 7 is provided with abutting the
back face of the valve cover 7, in order that the upper face 8 of
the valve cover 7 intimately contacts with the bottom face 3 of the
poppet valve 2. The spring 12 biases the valve cover 7 to let it
abut the bottom face 3 of the poppet valve 2. The valve cover 7 and
poppet valve 2 are consequently driven integrally by the cam 30 and
spring 12.
[0110] The spring 12 is one of means to let the second valve sheet
16, poppet valve 2 and valve cover 7 contact intimately with one
another.
[0111] The spring 12 biases the valve cover 7 toward the second
valve sheet 16.
[0112] The spring 12 also functions as a valve spring of the poppet
valve 2 which may be provided with abutting the poppet valve 2. In
the embodiment shown in FIG. 1, the valve spring in contact with
the poppet valve 2 is not provided. By providing the spring 12 for
the valve cover 7, the valve spring abutting the poppet valve 2 can
be omitted. That is, the valve spring abutting the stem of the
poppet valve 2 is not essential. As a matter of course, the valve
spring abutting the stem of the poppet valve 2 may be further
provided.
[0113] While the piston is in compression and combustion strokes,
combustion gas flows toward the ring groove through the gap between
the cylindrical side face of the valve cover 7 and the inner wall
of the sub cylinder 4. The combustion gas flows in one direction.
Then, the compression ring 9 is subjected to a force in the
direction to compress the spring 12. Accordingly, the combustion
gas blows the valve cover 7. Therefore, it is necessary that the
spring 12 is stronger than the combustion gas pressure applied to
the compression ring 9.
[0114] The valve cover 7 is not driven when the poppet valve 2 is
closed. The valve cover 7 thus does not move while the piston is in
a combustion stroke. As a result, the valve cover 7 is hard to
seize up.
[0115] In FIG. 1, the upper face 8 of the valve cover 7 and the
bottom face 3 of the poppet valve 2 are in intimate contact with
each other, and a boundary of the valve cover 7 and poppet valve 2
is drawn by a solid line. In FIG. 1, two lead lines refer the solid
line showing the intimate contact. The upper lead line is for
reference numeral 8 and the lower one is for reference numeral 3.
The solid line represents both the upper face of the valve cover 7
and the bottom face 3 of the poppet valve 2. Therefore, the two
lead lines are drawn in the opposite direction with each other.
[0116] When the upper face 8 of the valve cover 7 and the bottom
face 3 of the poppet valve 2 are in intimate contact with each
other, combustion gas does not break into the boundary between the
valve cover 7 and the bottom face 3 of the poppet valve 2. It is
preferable that the upper face 8 of the valve cover 7 and the
bottom face of the poppet valve 2 have the same size. In this case,
the upper face 8 of the valve cover 7 is not subjected to
combustion gas pressure. If the upper face 8 of the valve cover 7
is larger than the bottom face 3 of the poppet valve 2, the upper
face 8 of the valve cover 7 is subjected to the combustion gas
pressure.
[0117] The poppet valve 2 is closed during a compression stroke of
the piston 26. The valve cover 7 is located with abutting the
bottom face 3 of the poppet valve 2. The upper part of the valve
cover 7 occupies the most space of the extended part of the
combustion chamber 27 outside the main cylinder 1, which would face
with the bottom face 3 of the poppet valve 2 if the valve cover 7
were not provided. As a result, the volume of the combustion
chamber 27 reduces by the volume of the upper part of the valve
cover 7 which protrudes into the combustion chamber 27. Compared to
the engine of patent document 1, compression ratio of the
combustion chamber 17 becomes high. Therefore, the first object is
achieved by this engine.
[0118] Regarding FIG. 2, when the cam 30 lifts the poppet valve 2,
the valve cover 7 moves along with the poppet valve 2. When the
poppet valve 2 lifts to the maximum, the most part of the valve
cover 7 positions inside the sub cylinder 4. When the poppet valve
2 is open, the combustion chamber 27 facing with the upper face of
the piston communicates to outside of the engine.
[0119] In the first embodiment, the poppet valve 2 is provided on
the wall of the first part extended outside the main cylinder 1 of
the combustion chamber 27. Further, the total number of the
overhead valves and poppet valve is not less than three. Therefore
in the engine of first embodiment, the total area of the intake and
exhaust valves increases compared to the conventional art which
does not have a poppet valve outside a main cylinder. In the first
embodiment, the overhead valves 25A and 25B face with the upper
face of the piston. Therefore in the engine of the first
embodiment, the total area of the intake and exhaust valves
increases compared to the side valve engine of patent document
3.
[0120] Therefore, when the engine of the first embodiment rotates
at high speed, efficiency of intake and exhaust increases compared
to the conventional art. This advantage is not disclosed in patent
documents 1 and 3.
[0121] It is not disclosed in patent document 3 to increase the
area of intake or exhaust side valves.
[0122] It is disclosed in patent document 2 to provide both
overhead valve and sliding valve. However, this feature is
different from the first embodiment.
[0123] Second to fifth embodiments are modifications of the first
embodiment. The first object is achieved in these embodiments.
[0124] For these embodiments, only the difference from the first
embodiment will be described.
[0125] The second embodiment will be described.
[0126] In FIG. 4, the sub cylinder 4 is provided in the cylinder
head 5. In this case, the gas path contacting with the poppet valve
2 is provided in the cylinder block. The poppet valve 2 provided
outside the cylinder is a side valve.
[0127] The third embodiment will be described.
[0128] In FIG. 5, a pneumatic unit, hydraulic unit 19,
electromagnetic unit or electric unit is employed in place of the
spring 12. These units bias the valve cover 7 so that the upper
face 8 presses the bottom face of the poppet valve 2. These units
and the third spring 12 are to bias the valve cover 7 toward the
valve sheet 16.
[0129] In FIG. 5, the compression ring 9 is subject to the pressure
of the combustion gas so that the valve cover is pushed downwards.
The valve cover and the bottom face of the poppet valve are not
separated from each other by the pressing force.
[0130] The above-described units including the hydraulic unit 19
bias the valve cover toward the valve sheet 16 of the poppet valve
2 with a force not less than this pressing force.
[0131] The fourth embodiment will be described.
[0132] In FIG. 6, the poppet valve 2 and valve cover 7 are
integrally formed.
[0133] In FIG. 6, a dashed dotted line shows a phantom joint face
between the poppet valve 2 and valve cover 7. Actually, the joint
face shown by the dashed-dotted line does not exist.
[0134] In FIG. 6, when the third spring 12 to push the valve cover
7 is not provided, the second spring 31 abutting the stem of the
poppet valve 2 functions as a replacement of the third spring 12.
The second spring 31 pulls the poppet valve 2. The spring 12 may be
thus omitted.
[0135] Conversely, when the third spring 12 is provided, the second
spring 31 abutting the stem of poppet valve 2 may be omitted.
[0136] The fifth embodiment will be described.
[0137] In FIG. 7, a ring groove for the compression ring 9 is
provided on an inner wall of the sub cylinder 4. The compression
ring 9 is disposed onto the ring groove.
[0138] In order that the compression ring 9 seals the combustion
gas, the compression ring 9 is wedged between the cylindrical side
face of the valve cover 7 and the inner wall of the sub cylinder 4.
A ring groove is not provided on the cylindrical side face of the
valve cover 7. Therefore in this engine, the force of the
combustion gas given to the compression ring 9 does not push the
valve cover 7 downward. Therefore in the engine shown in FIG. 7, a
weaker spring may be employed than the spring of the engine shown
in FIG. 1.
[0139] The following sixth to tenth embodiments show additional
features to the first to fifth embodiments. The sixth to tenth
embodiments are to further modify the first to fifth
embodiments.
[0140] The sixth to tenth embodiments are not disclosed in patent
documents 1 and 3.
[0141] The sixth and eighth to tenth embodiments are not disclosed
in patent document 2.
[0142] The sixth embodiment will be described with reference to
FIGS. 8 and 9.
[0143] The sixth embodiment is included in the second aspect.
[0144] The end 10 of the sub cylinder 4 is disposed at a position
adjacent to the second valve sheet 16 of the poppet valve 2. The
part adjacent to the poppet valve 2 of the sub cylinder 4 may be
formed integrally with the part facing with the compression ring 9
of the sub cylinder 4, or may be formed as a part of the cylinder
head. When the poppet valve 2 is open, the valve head of the poppet
valve 2 is located inside the sub cylinder 4.
[0145] The whole circumference of the cylindrical side face of the
valve cover 7 adjacent to the poppet valve 2 is sectioned into two
half circumferences by a dashed-four dotted line 38 which is
perpendicular to a dashed-three dotted line 39 connecting the
central axis 37 of the main cylinder 1 and the central axis of the
sub cylinder 4 intersecting at the central axis of the sub cylinder
4.
[0146] The two half circumferences are referred to as a first half
circumference which is close to the central axis 37 of the main
cylinder 1 and a second half circumference which is away from the
central axis 37 of the main cylinder 1.
[0147] The cylindrical side face of the valve cover 7 adjacent to
the poppet valve 2 is sectioned into two half surrounding faces.
The two half surrounding faces are a first half surrounding face 40
having the first half circumference and a second half surrounding
face 35 having the second half circumference.
[0148] A part adjacent to the second valve sheet of the sub
cylinder 4 faces with the second half surrounding face 35. The part
is drawn as the sub cylinder referred by reference numeral 4 in
FIG. 9.
[0149] A fixed wall, which is located outside the combustion
chamber extended outside the main cylinder 1, is provided adjacent
to the inner wall facing with the second half surrounding face 35
of the sub cylinder 4.
[0150] When the part adjacent to the poppet valve 2 of the sub
cylinder 4 is formed integrally with a part facing with the
compression ring 9 of the sub cylinder 4, the fixed wall located
outside the combustion chamber extended outside the main cylinder 1
is constituted by a fixed wall which is adjacent to the outer face
36 facing with the second half surrounding face 35 of the sub
cylinder 4 and the sub cylinder 4 which faces with the second half
surrounding face 35.
[0151] An opening 18 of the sub cylinder 4 is provided in the
vicinity of the one end 10 of the sub cylinder 4.
[0152] A first gas path 11 is provided between the second valve
sheet 16 of the poppet valve 2 and outside of the engine.
[0153] A second gas path 21 is provided which communicates the
space inside the main cylinder 1 and the first gas path 11 in a
short distance when the poppet valve 2 is open. The opening 18
constitutes the second gas path 21. In FIG. 9, the opening 18 is
shown by a dashed-two dotted line.
[0154] The opening 18 faces with the first half surrounding face
40.
[0155] The second gas path 21 is included in the combustion chamber
surrounded by the second part.
[0156] A plurality of the combinations of the valve cover 7, sub
cylinder 4 and the opening 18 may be provided in the second part
which extends outside the main cylinder 1.
[0157] In the sixth embodiment, the volume of the combustion
chamber extended outside the main cylinder is decreased compared to
the engines disclosed in patent documents 1 and 3, and the
compression ratio is thus high.
[0158] The cylindrical side face of the valve cover 7 is subject to
the heat of the combustion gas in a part of its upper part during
combustion strokes and expansion strokes.
[0159] A part adjacent to the poppet valve 2 of the cylindrical
side face of the valve cover 7 is subject to the pressure of the
combustion gas in a direction from the central axis of the main
cylinder 1 to the central axis of the sub cylinder 4 during
combustion strokes and expansion strokes. When the part adjacent to
the poppet valve 2 of the cylindrical side face of the valve cover
7 is divided into two sections, the second half surrounding face 35
is pressed to and contacts closely with the part of the sub
cylinder 4 comprising the outer face 36. The part comprising the
outer face 36 of the sub cylinder 4 faces with the second half
surrounding face 35. The combustion gas does not flow in between
the contacted two faces. The heat of the combustion gas does not
flow into the contacted two faces.
[0160] Consequently in the sixth embodiment, the area which is
subjected to the heat of the combustion gas in the cylindrical side
face of the valve cover 7 is reduced compared to the engine
disclosed in patent document 3, and the thermal loss of this engine
is thus reduced. The larger the area in close contact is, the lower
the temperature of the cylindrical side face becomes. Therefore,
the fuel efficiency is improved and the resistance to knocking is
also improved compared to the engine disclosed in patent document
3.
[0161] The seventh embodiment will be described.
[0162] The seventh embodiment is included in the third aspect.
[0163] The problems relating to a balance of conversion efficiency
improvement and torque enhancement is described in the description
of the related art.
[0164] This problem can be solved by the following feature. The
engines of the first to sixth embodiments are further configured
such that the length of the piston stroke is not shorter than the
diameter of the piston. That is, the length of the piston stroke is
approximately same as or longer than the diameter of the main
piston in these engines.
[0165] By this feature, the conversion efficiency of combustion gas
is improved compared to short stroke engines. Also, decrease of
intake efficiency which occurs in long stroke engines rotating at
high speed is improved. As a result, it becomes possible to strike
improvement of conversion efficiency and increase of torque at high
speed in balance. The third object is thus achieved.
[0166] The eighth embodiment will be described with reference to
FIG. 10.
[0167] The part adjacent to the poppet valve 2 of the valve cover 7
is heated by the combustion gas in combustion strokes. In the case
of a spark-ignition engine, knocking is caused by a high
temperature part in a combustion chamber. In the case of a piston
engine, a filling rate of intake decreases due to a high
temperature part in a combustion chamber.
[0168] In order to solve these problems, a spray valve 41 is
further provided to the engines of the first to seventh
embodiments. The spray valve 41 sprays oil to the back face of the
part adjacent to the poppet valve 2 of the valve cover 7. Further,
the spring 12 is provided with abutting the back face. Thus, the
temperature of the part adjacent to the poppet valve 2 of the valve
cover 7 becomes low, and knocking occurs less. Then, it becomes
possible to configure the compression ratio higher, and the heat
efficiency is thus improved. As a result, the third object is
achieved.
[0169] Further, the filling rate of intake does not decrease.
[0170] The ninth embodiment will be described.
[0171] The following feature of the engine shown in FIG. 11 may be
added to any embodiments except the fourth embodiment.
[0172] The face abutting the poppet valve 2 of the valve cover 7 is
a convex curve, and the face contacting with the valve cover 7 of
the poppet valve 2 is a concave curve. These two faces have a same
curvature.
[0173] In the engine shown in FIG. 1, if the pressure in the
combustion chamber increases sharply, the part adjacent to the
poppet valve of the valve cover 7 is pressed in a direction toward
the opposite side of the piston 26. The part adjacent to the poppet
valve 2 of the valve cover 7 may be thus deformed. The bottom 3 of
the poppet valve 2 is not deformed. On the other hand, a gap does
not formed between the two curved faces in the engine shown in FIG.
11. A solid line shows the state that the two faces closely
contacted with each other. Even if the pressure in the combustion
chamber increases sharply, the two faces shown in FIG. 11 do not
separate from each other.
[0174] The tenth embodiment will be described.
[0175] In the engine shown in FIG. 7, when oil is supplied to the
inner wall of the sub cylinder 4, the oil penetrates into the gap
between the cylindrical side face of the valve cover 7 and the
inner wall of the sub cylinder 4 by capillarity and movement of the
valve cover 7. The oil penetrated into the gap is sucked into the
combustion chamber during intake strokes. As a result, oil
consumption increases.
[0176] On the other hand, when an oil ring 22 is provided on the
cylindrical side face of the valve cover 7 as shown in FIG. 12, the
oil consumption can be controlled. However, the compression ring 9
provided on the inner wall of the sub cylinder does not move.
Accordingly, the compression ring 9 does not transfer the oil.
Therefore, in the case shown in FIG. 12, the compression ring 9
provided at the closer side to the combustion chamber lacks its
lubrication.
[0177] This problem is solved by adding the following feature.
[0178] As shown in FIG. 13, the upper compression ring 23 is
provided on the inner wall of the sub cylinder at the closer side
to the combustion chamber 27, and the lower compression ring 24 is
provided on the cylindrical side face of the valve cover 7. The
upper compression ring 23 is provided between the lower compression
ring 24 and combustion chamber 27. When the poppet valve 2 is
closed, the upper end of the lower compression ring 24 is located
adjacent to the lower end of the upper compression ring 23. The
lower compression ring 24 is provided between the oil ring 22 and
the upper compression ring 23. The oil ring 22 is provided on the
cylindrical side face of the member.
[0179] When the valve cover 7 moves, the lower compression ring 24
also moves. The moving lower compression ring 24 transfers the
residual oil which is not removed by the oil ring to the lower end
of the upper compression ring 23. The upper compression ring 23 is
thus lubricated.
[0180] A spray hole of oil is provided between the position of the
lower compression ring 24 when the cam shifts the valve cover 7 at
the maximum and the position of the oil ring 22 when the poppet
valve 2 is closed. Thus, the amount of oil which the lower
compression ring 24 transfers increases.
* * * * *