JPH10184446A - Four-cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve performance by enhancing radiation ability of a combustion chamber, and to improve durability and reliability through the increase of the wear strength of a part. SOLUTION: In a four-cycle engine, a cylinder head 3 is made of an Al alloy and valve sets 16 and 17 arranged at the peripheral edges of intake and exhaust ports 12a and 13a are formed of a joint type valve seat. A piston 7 made of an Al alloy is slidably fitted in a sleeveless cylinder 6 formed at the cylinder block 3 made of an Al alloy. This constitution increases a quantity of heat transferred through intake and exhaust valves 14 and 15 and the joint type valve seats 16 and 17 directly to the cylinder head 3 and a quantity of heat transferred through the piston 7 directly to a cylinder block 2 and improves radiation ability of a combustion chamber S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-stroke engine for performing required gas exchange by opening and closing intake and exhaust ports formed in a cylinder head at appropriate timing by intake and exhaust valves.

[0002]

2. Description of the Related Art In such a four-cycle engine,
An Fe-based valve seat, on which intake and exhaust valves are to be intermittently seated, is generally mounted by press fitting on the periphery of the intake and exhaust ports of the cylinder head. A piston is slidably fitted in the cylinder formed in the cylinder block, but a sleeve made of cast iron (cylinder liner) with excellent seizure resistance and wear resistance is provided on the piston sliding surface of the cylinder. Was press-fitted.

[0003]

In recent years, cylinder heads, cylinder blocks,
Pistons etc. are made of lightweight aluminum alloy with good thermal conductivity, but press-fit valve seats and sleeves have a relatively large thickness due to the need to ensure the required strength and rigidity, so their heat capacity is large. And the thermal conductivity of itself is A
Since it is not high compared to cylinder heads and cylinder blocks made of alloy, the amount of heat transmitted from the combustion chamber to the cylinder head via the intake / exhaust valve and valve seat and the amount of heat transmitted to the cylinder block via the piston and sleeve are small. There is a problem that the heat radiation of the combustion chamber is poor.

[0004] As described above, if the heat radiation of the combustion chamber is poor,
The density of the air-fuel mixture introduced into the combustion chamber decreases, the charging efficiency decreases, engine performance decreases, and the wear resistance of valve seats and intake and exhaust valves decreases, and their durability and reliability deteriorate. I do. If the temperature of the combustion chamber is high, knocking is likely to occur, so that the compression ratio cannot be set high, which also lowers the engine performance.

Accordingly, an object of the present invention is to improve the performance by improving the heat radiation of the combustion chamber, and to improve the durability and reliability of the components by increasing the wear strength of the parts. It is to provide a cycle engine.

At the time of low temperature and low load, such as during warm-up operation immediately after the start of the engine, the oil temperature is low and the oil viscosity is large, so that the loss horsepower of the engine increases and the exhaust gas and characteristics deteriorate. There is.

Accordingly, an object of the present invention is to provide a four-stroke engine capable of reducing loss horsepower and improving fuel economy and exhaust gas characteristics by quickly raising the oil temperature during a warm-up operation. It is in.

[0008]

In order to achieve the above object, the invention according to the first aspect of the present invention requires a suction / exhaust port formed in a cylinder head to be opened and closed at an appropriate timing by an intake / exhaust valve. Gas exchange 4
In the cycle engine, the cylinder head is
The valve seat provided on the periphery of the intake / exhaust port of this alloy is made of a joint type valve seat, and a piston made of Al alloy is slidably mounted on a sleeveless cylinder formed on a cylinder block made of Al alloy. It is characterized by being fitted.

According to a second aspect of the present invention, in the first aspect of the invention, the water jacket is formed independently of the cylinder head and the cylinder block, and the flow rate of the cooling water on the cylinder head side is 60% to 90%. Is set.

According to a third aspect of the present invention, in the second aspect of the present invention, most of the cooling water flows to the cylinder head side during the warm-up operation.

Therefore, according to the first aspect of the present invention, the cylinder head, the cylinder block, and the piston are made of an aluminum alloy having high thermal conductivity, and the valve seat is made of a joint valve seat having a small thickness. Furthermore, the adoption of a sleeveless cylinder increases the amount of heat transmitted from the combustion chamber to the cylinder head via the intake / exhaust valve and the joint valve seat, and the amount of heat transmitted directly to the cylinder block via the piston, increasing the heat dissipation of the combustion chamber. In addition, the filling efficiency and the knocking resistance are enhanced to improve the engine performance, and the wear resistance of the intake / exhaust valves and the valve seats is enhanced, so that their durability and reliability are enhanced.

According to the second or third aspect of the present invention,
Cooling water is mainly flowed to the cylinder head side for cooling, so that the temperature of the oil flowing through the cylinder block is quickly raised to a set value, and as a result, the viscosity of the oil is reduced and the loss horsepower of the engine is reduced. Accordingly, fuel economy and exhaust gas characteristics are improved.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a cutaway front view of a four-cycle engine according to the present invention, FIG. 2 is an enlarged sectional view of a combustion chamber portion of the four-cycle engine, and FIG. 3 is a partial bottom view of a cylinder head of the four-cycle engine. .

[0015] Four-cycle engine 1 according to the present embodiment
Is a multi-cylinder five-valve engine, in which a cylinder block 2 is integrally cast of an Al alloy, and a cylinder head 3 also integrally cast of an Al alloy is attached to an upper portion of the cylinder block 2. Yes,
A crankcase 4 is attached to a lower part. An oil pan 5 is attached to a lower portion of the crankcase 4.

A plurality of cylinders 6 are arranged in the cylinder block 2 in a direction perpendicular to the plane of FIG. 1. Each of the cylinders 6 constitutes a sleeveless cylinder. Several tens of μm of nickel plating is applied, and a sleeve (cylinder liner) is not press-fitted in this. A piston 7 made of an Al alloy is slidably fitted in each cylinder 6, and each piston 7 is connected to a crankpin 9 a of a crankshaft 9 via a connecting rod 8. The crankshaft 9 is disposed in the crank chamber 10 so as to be long in the direction perpendicular to the plane of FIG. Further, a water jacket 11 through which cooling water passes is formed in the cylinder block 2.

On the other hand, the cylinder head 3 is formed with three intake passages 12 and two exhaust passages 13 for each cylinder, respectively. As shown in FIG. 3, each intake passage 12 serves as an intake port 12a. Each exhaust passage 13 opens to the combustion chamber S as an exhaust port 13a. The three intake ports 12a and the two exhaust ports 13a for each cylinder are opened and closed at appropriate timing by the same number of intake valves 14 and exhaust valves 15 made of Ti alloy, respectively. Is made. In addition, while the inclination angles of the two exhaust valves 15 are set to be the same for each cylinder,
The three intake valves 14 have different inclination angles at the center (center valve) and on both sides (side valves), and these intake valves 14 constitute a so-called radiation valve.

As shown in detail in FIG. 2, an intake valve 14 is provided on each of the plurality of intake ports 12a and exhaust ports 13a which open to each combustion chamber S of the cylinder head 3.
And valve seats 16 and 17 on which the exhaust valve 15 and the exhaust valve 15 are to be intermittently seated, respectively. These valve seats 16 and 17 have a thickness of several hundred μm to several thousand μm.
m, which are impact resistant,
It is formed in a ring shape from an Fe-based sintered material having excellent wear resistance and high-temperature strength, and is metallurgically joined to the cylinder head 3 by a resistance heat joining method. In order to impart high thermal conductivity and impact resistance to the joint type valve seats 16 and 17, a metal such as Cu is filled into the Fe-based sintered material, which is a material of the valve seats 16 and 17, by infiltration. Have been.

As shown in FIG. 1, the intake valve 14 and the exhaust valve 15 are provided with valve guides 18 and 1 respectively.
9 are slidably inserted and held, and are urged in the closing direction by valve springs 20 and 21. And, the intake valve 14 and the exhaust valve 15
Each of the rotating cams 22 and 23 is driven and opened / closed at an appropriate timing.

The cylinder head 3 is formed with a water jacket 24 through which cooling water passes.
The water jacket 11 is formed independently of each other. In the four-stroke engine 1 according to the present embodiment, cooling water is supplied as a cooling system by using the water jacket 11 on the cylinder block 2 side and the cylinder head 3 side. The so-called split cooling that flows separately through the water jacket 24 is adopted.

Further, as shown in FIG. 1, one end of an intake manifold 25 is connected to the intake passage 12 of each cylinder of the cylinder head 3, and a flange 25a at the other end of the intake manifold 25 is not connected. The illustrated throttle body is attached. An injector 26 for injecting fuel into each intake passage 12 is attached to each cylinder on the intake side of the cylinder head 3.

An exhaust manifold 27 is connected to each exhaust passage 13 on the exhaust side of the cylinder head 3.
A cam cap 28 is attached to an upper portion of the cylinder head 3, and a plug hole 28 a through which a spark plug (not shown) attached to each cylinder is inserted into the top of the cylinder head 3. Are formed.

On the other hand, an oil pump 29, an oil cooler 30, and an oil filter 31
The oil in the oil pan 5 is sucked from the oil strainer 32 into the oil suction pipe 33, guided to the oil pump 29, pressurized by the oil pump 29, and then passed through the oil discharge pipe 34 to each part. Supplied and provided for lubrication.

Thus, in the four-stroke engine 1 configured as described above, the cylinder block 2, the cylinder head 3, and the piston 7 are made of a lightweight and highly heat-conductive Al.
The valve seats 16 and 17 are made of a joint type valve seat having a small thickness.
As a result, the combustion chamber S
The amount of heat transmitted to the cylinder head 3 via the intake / exhaust valves 14, 15 and the joint type valve seats 16, 17 and the amount of heat transmitted directly to the cylinder block 2 via the piston 7 are increased, and the heat radiation of the combustion chamber S is improved. In addition, the charging efficiency and the knocking resistance are enhanced, the performance of the four-stroke engine 1 is improved, and the intake / exhaust valves 14, 15
And the wear resistance of the valve seats 16 and 17 is enhanced, and their durability and reliability are enhanced.

Further, in the multi-cylinder four-stroke engine 1 according to the present embodiment, the valve seats 16 and 17 are formed of a joint type valve seat having a small thickness, and the cylinder 6 employs a sleeveless cylinder. The distance between them (bore pitch) can be reduced, and the four-stroke engine 1 can be reduced in size and size.

Next, a cooling system of the four-stroke engine 1 according to the present embodiment will be described with reference to FIG. FIG. 4 is a schematic diagram showing the configuration of the cooling system of the four-cycle engine.

As shown in FIG. 4, the engine cooling system has a cooling circuit that forms a closed loop including a cooling water pump 35 and a radiator 36. The cooling circuit includes a cooling circuit from the discharge side of the cooling water pump 35. A cooling water passage 37a to be derived;
The cooling water passage 3 branched from the cooling water passage 37a and connected to each inlet side of the water jackets 11, 24 formed independently of the cylinder block 2 and the cylinder head 3, respectively.
7b, 37c and cooling water passages 37d, 37e connected to the respective outlet sides of the water jackets 11, 24, respectively.
And cooling water which flows separately through the water jackets 11 and 24 to join the cooling water used for cooling the cylinder block 2 and the cylinder head 3, respectively, and guides the cooling water to the radiator 36, and is cooled by the radiator 36. Cooling water passage 37 for returning the cooled water to cooling water pump 35
g, and a thermostat valve 38 is provided in the middle of a cooling water passage 37 g close to the cooling water pump 35,
A control valve 39 is provided in the middle of the cooling water passage 37d.

A bypass passage 37h branches off from the cooling water passage 37f. The bypass passage 37h is connected to a cooling water pump 35.

The control valve 39 controls the flow rate of the cooling water flowing on the cylinder block 2 side (the flow rate of the cooling water flowing on the cylinder block 2 side and the cylinder head 3 side). The ECU 40 is driven by a unit (hereinafter abbreviated as ECU) 40, and controls the opening of the control valve 39 in accordance with the coolant temperature detected by the coolant temperature sensor 41 provided in the coolant passage 37f to control the cylinder block 2 The flow rate of the cooling water flowing between the side and the cylinder head 3 is adjusted.

When the four-stroke engine 1 is started, the oil pump 29 and the cooling water pump 35 are driven by the crankshaft 9 to supply oil and cooling water to the cylinder block 2 and the cylinder head 3, respectively. To provide lubrication and cooling for each part.
During the warm-up operation immediately after the start of the engine, the cooling water temperature detected by the water temperature sensor 41 is low, the thermostat valve 38 is closed, and the ECU 40
9 is controlled to reduce the opening.

Accordingly, the cooling water discharged from the cooling water pump 35 flows through the water jackets 11 and 24 formed independently of the cylinder block 2 and the cylinder head 3 via the cooling water passages 37a to 37c, and the respective parts are cooled. Although cooling is performed, the opening degree of the control valve 39 is set to a small value as described above.
Cooling water is supplied to the water jacket 2 on the cylinder head 3 side.
4 and a small amount (for example, 10% in flow rate) of cooling water flows through the water jacket 11 on the cylinder block 2 side. The cooling water, which has cooled the cylinder block 2 and the cylinder head 3 and has become hot,
After returning to the cooling water pump 35 after passing through 7 h, the temperature is gradually increased since it is not circulated and guided to the radiator 36 in the same manner.

On the other hand, when the oil pump 29 shown in FIG. 1 is driven, the oil in the oil pan 5 is sucked from the oil strainer 32, reaches the oil pump 29 through the oil suction pipe 33, and is boosted by the oil pump 29. The oil that has passed through the oil discharge pipe 34 passes through the oil cooler 30 and the oil filter 31 to reach an oil main gallery (not shown) formed in the cylinder block 2, and is supplied from the oil main gallery to the respective parts, and the respective sliding parts After being subjected to lubrication, the oil is dropped on the oil pan 5 and collected.

During the warm-up operation, as described above, the opening of the control valve 39 is reduced and the flow rate of the cooling water to the cylinder block 2 is set to a small value. The temperature of the oil flowing through the oil main gallery quickly rises, the viscosity of the oil falls, the loss horsepower accompanying the friction loss of the four-cycle engine 1 is reduced, and the fuel economy and exhaust gas characteristics are improved.

On the other hand, when the temperature of the cooling water gradually rises as described above, the thermostat valve 38 opens, and the cooling water whose temperature has increased by cooling the engine 1 is guided to the radiator 36 through the cooling water passage 37f. After being cooled by the radiator 36, the cooling water is returned to the cooling water pump 35 from the cooling water passage 37g. Thereafter, the same operation is repeated to keep the temperature substantially constant. Control the opening of the control valve 39 in accordance with
The flow rate of the cooling water to the cylinder head 3 side is 60 to 90
Set to%. As described above, by setting the flow rate of the cooling water flowing to the cylinder head 3 side to be large and reducing the flow rate of the cooling water flowing to the cylinder block 2 side, the temperature of the oil is kept high in the entire operation range, and the four-cycle engine A reduction in loss horsepower and an improvement in fuel efficiency and exhaust gas characteristics are achieved in all operating ranges.

In this embodiment, the ECU 40 controls the opening degree of the control valve 39 in accordance with the detected coolant temperature to adjust the flow rate of the coolant to the cylinder block 2 and the cylinder head 3. However, a thermostat valve may be used instead of the control valve 39.

As shown in FIG. 5, the cooling water passage 37a
By setting the cross-sectional area of the cooling water passage 37 j toward the cylinder head 3 to be larger than the cross-sectional area of the cooling water passage 37 k toward the cylinder block 2 in the cooling water passage 27 i in the engine 1 connected to the cylinder head 3. The flow rate of the cooling water flowing to the side may be set to 60% to 90% (fixed).

[0037]

As is apparent from the above description, claim 1
According to the described invention, the cylinder head, the cylinder block, and the piston are made of an Al alloy having high thermal conductivity, and the valve seat is made of a thin joint type valve seat, and a sleeveless cylinder is used.
The amount of heat transmitted from the combustion chamber to the cylinder head via the intake / exhaust valve and the joint type valve seat and the amount of heat transmitted directly to the cylinder block via the piston are increased, and the heat dissipation of the combustion chamber is enhanced, and the charging efficiency and knocking resistance are improved As a result, the engine performance is improved, and the wear resistance of the intake / exhaust valve and the valve seat is increased, so that the durability and reliability of the valve are improved.

According to the second or third aspect of the present invention,
Cooling water is mainly flowed to the cylinder head side for cooling, so that the temperature of the oil flowing through the cylinder block is quickly raised to a set value, and as a result, the viscosity of the oil is reduced and the loss horsepower of the engine is reduced. This has the effect of improving fuel economy and exhaust gas characteristics.

[Brief description of the drawings]

FIG. 1 is a cutaway front view of a four-stroke engine according to the present invention.

FIG. 2 is an enlarged sectional view of a combustion chamber portion of a four-cycle engine according to the present invention.

FIG. 3 is a partial bottom view of the cylinder head of the four-stroke engine according to the present invention.

FIG. 4 is a schematic diagram showing a configuration of an engine cooling system of a four-cycle engine according to the present invention.

FIG. 5 is a schematic diagram showing another configuration of the engine cooling system of the four-cycle engine according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 4 cycle engine 2 Cylinder block 3 Cylinder head 6 Sleeveless cylinder 7 Piston 11, 24 Water jacket 12a Intake port 13a Exhaust port 14 Intake valve 15 Exhaust valve 16, 17 Joint valve seat

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02F 1/36 F02F 1/36 Z

Claims (3)

[Claims] 1. A four-stroke engine for performing a required gas exchange by opening / closing an intake / exhaust port formed in a cylinder head with an intake / exhaust valve at an appropriate timing, wherein the cylinder head is made of an Al alloy. The valve seat provided on the periphery of the intake / exhaust port is constituted by a joint type valve seat, and an Al alloy piston is slidably fitted in a sleeveless cylinder formed in an Al alloy cylinder block. Features a 4-cycle engine. 2. A water jacket is formed on a cylinder head and a cylinder block independently of each other.
60% to 90% of the flow rate of cooling water on the cylinder head side
The four-stroke engine according to claim 1, wherein the four-stroke engine is set to: 3. The four-stroke engine according to claim 2, wherein most of the cooling water flows to the cylinder head side during the warm-up operation.