JP4674519B2 - Intake valve for internal combustion engine - Google Patents

Description

  The present invention relates to an intake valve for an internal combustion engine.

  An intake valve for an internal combustion engine communicates and shuts off the intake manifold to which fuel is supplied and the combustion chamber, but promotes vaporization of the fuel supplied by the heat of the intake valve itself when shut off And has a function of enabling smooth intake of fuel and a combustible state.

  For example, in Patent Document 1 below, in order to promote such fuel vaporization, a coil is provided in the intake valve itself to actively heat the intake valve.

However, the intake valve moves smoothly and at high speed under high heat conditions, reliably opens and closes the combustion chamber, and must be closed without leakage when closed, so it is lightweight overall and has no accessories. It is required to be finished with high accuracy, and it is not preferable to provide a coil. Essentially, it is preferable to promote fuel vaporization from the shape and structure of the intake valve itself.
Japanese Patent Laid-Open No. 6-221112 (Summary, see FIG. 1 etc.)

  However, heat-resistant steels such as SUH1 to SUH11 are generally used as materials constituting the intake valve, with an emphasis on heat resistance (oxidation resistance at high temperatures) and fatigue strength. In order to reduce weight, eliminate loss during operation, and improve engine performance, a titanium alloy (Ti alloy) having a low specific gravity and excellent high-temperature strength may be used. In addition, the intake valve made of titanium alloy can be reduced in weight by about 40% from the current mainstream made of heat-resistant steel, and the high-speed motion performance is improved by about 10%.

  Such an intake valve made of heat-resistant steel or titanium alloy has a low thermal conductivity and cannot sufficiently exhibit the function of promoting fuel vaporization or atomization. For example, the heat conductivity of an intake valve made of heat-resistant steel is about 25 W / m · K, and about 8 W / m · K for titanium, and the heat transferred to the intake valve by combustion in the combustion chamber is transmitted to the outside. It is hard to be done.

  For this reason, there is a problem that the temperature of the combustion chamber is likely to rise, and it is difficult to obtain effects such as improvement in knocking performance of the internal combustion engine, fuel saving, and output improvement. In addition, since it is difficult to transfer heat to the back side of the intake valve, that is, the intake manifold side, the effect of atomizing the fuel accumulated here is poor, and if this fuel flows into the combustion chamber as it is, the ignitability is poor, There is also a problem that the variation in combustion increases and the thermal efficiency decreases.

  Furthermore, if the thickness of the umbrella portion is reduced in order to increase the thermal conductivity and reduce the temperature in the combustion chamber, the high temperature strength of the intake valve itself will decrease, causing deformation of the umbrella portion, fatigue cracks, etc. There is also.

  The present invention has been made in order to solve the problems associated with the above-described conventional technology, and can easily optimize the thickness of the umbrella portion of the intake valve itself, and has improved thermal conductivity and excellent heat resistance. Another object of the present invention is to provide an intake valve for an internal combustion engine that can sufficiently exhibit a fuel vaporization promoting function.

The invention according to claim 1 includes an umbrella portion and a valve shaft, and the umbrella portion reaches the valve shaft from the valve seat surface, the valve seat surface formed on the outer peripheral surface, the valve seat surface. An intake valve for an internal combustion engine having an arc-shaped connecting surface, the minimum radius r of a circumscribed circle that circumscribes the connecting surface around the intersection of the center line of the valve shaft and the surface on the combustion chamber; The ratio β (= r / D1 ) to the diameter D1 of the portion satisfies the following mathematical formula.

Where α: thermal conductivity of the material of the umbrella part x: fatigue strength measured by a rotary bending test after holding a test piece of the constituent material of the intake valve at 250 ° C. for 100 hours

According to the first aspect of the present invention, when the thickness of the umbrella portion of the intake valve for the internal combustion engine is set based on the formula (1), the thickness of the umbrella portion is increased in terms of improvement in heat conductivity and heat resistance. Ru can be optimized easily. The resulting intake valve not only has high fatigue resistance at high temperatures and excellent fracture strength characteristics, but also sufficiently reduces the temperature in the combustion chamber and fully demonstrates the fuel vaporization promotion function on the back side of the intake valve. In addition, the knocking property, fuel efficiency and output of the internal combustion engine are improved, and the valve itself can be easily molded. In particular, when the thickness (β) of the umbrella portion of the intake valve is determined from β ≦ α / 175, an increase in fuel consumption is prevented and the fuel consumption rate is reduced.
According to the second aspect of the present invention, since the thickness (β) of the umbrella portion of the intake valve is determined from β ≦ α / 250, the obtained intake valve has a fuel consumption amount in addition to the effect of the previous item. The increase is prevented and the fuel consumption rate decreases.
According to the third and fourth aspects of the invention, the umbrella portion of the intake valve is formed of aluminum alloy or rapidly solidified aluminum alloy powder, which is a material having high thermal conductivity and high temperature fatigue strength. Intake valve with excellent knocking performance.

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

  1 is a cross-sectional view showing an intake valve portion for an internal combustion engine according to an embodiment of the present invention, FIG. 2 is an explanatory view of the intake valve, and FIG. 3 is a schematic cross-sectional view showing stepwise the fuel vaporization function of the intake valve. 4A shows the fuel storage state, FIG. 4B shows the state in which combustion is supplied to the combustion chamber, FIG. 4C shows the combustion state in the combustion chamber, and FIGS. FIG. 6 is a correspondence diagram of similar states of a conventional intake valve.

  As shown in FIG. 1, the intake valve 1 for an internal combustion engine of the present embodiment is a flat head type valve having an umbrella part 2 and a valve shaft 3 provided on the back side of the umbrella part 2. In the figure, “4” is a spark plug, “5” is a cylinder, “6” is a cylinder head, “7” is a spring, and “8” is a valve cotter.

  The umbrella portion 2 communicates and shuts off the intake passage 9 and the combustion chamber 10 of the internal combustion engine. As shown in FIG. 2, the umbrella portion 2 has a flat combustion chamber side surface 2a facing the combustion chamber 10 and an intake passage. 9 has a valve seat surface 2b formed so as to be in close contact with the valve seat portion, which is the tip opening portion, and an arc-shaped connecting surface 2c extending from the valve seat surface 2b to the valve shaft 3.

  The intake valve 1 pushes up one end of a rocker arm by a push-up force of a push rod (both not shown), and pushes down a valve shaft 3 abutted against the other end against the elastic force of a spring 7 to suck an intake passage 9. And the combustion chamber 10 are communicated, and the elastic force of the spring 7 is returned by releasing the push-up force, thereby interrupting the communication. Therefore, the intake valve 1 faces the combustion chamber 10 where the fuel burns and reciprocates linearly at a high speed under high heat conditions. Therefore, the intake valve 1 is light in weight and can reliably seal and smoothly reciprocate. It is finished with high accuracy.

  In addition, the intake valve 1 has not only the opening / closing function of the combustion chamber 10 described above, but also a secondary function of fuel vaporization promoting function when shut off. The fuel vaporization promoting function is based on the heat stored in the intake valve 1 itself when the fuel F fed by the intake valve 9 being blocked by the intake valve 1 is accumulated on the back side of the intake valve 1. The function of vaporization or atomization contributes to lowering the temperature of the combustion chamber 10 by increasing the latent heat of vaporization of the intake valve 1.

  The mechanism of such a function will be described in detail. FIG. 3 shows the case of an intake valve with good thermal conductivity as in the present invention, and FIG. 4 shows the case of an intake valve with poor thermal conductivity. For example, in the case of an intake valve with poor thermal conductivity, as shown in FIG. 4A, fuel F accumulates on the back side of the intake valve 1, but in the intake valve 1, the intake valve itself is connected to the combustion chamber 10. The heat generated by the combustion of the fuel is not sufficiently transferred to the fuel F, and as shown in FIG. 4 (B), even if a large amount of the fuel F flows into the combustion chamber 10 in a liquid state or vaporizes as it is. Even if the vaporized fuel distribution is biased and ignited, as shown in FIG. 4C, the variation in the combustion period increases due to the variation in the air-fuel mixture distribution. As a result, the ignitability is poor, the variation in combustion increases, knocking occurs, the output decreases, and the fuel consumption also increases.

  However, in the case of an intake valve having good thermal conductivity, as shown in FIG. 3A, when fuel F is accumulated on the back side of the intake valve 1 when the intake valve 1 is closed, the umbrella portion 2 of the intake valve 1 is used. The temperature of the rear side of the fuel is likely to rise, and the heat promotes the vaporization of the fuel, and the vaporized fuel diffuses in the intake passage 9 to generate a homogeneous air-fuel mixture. On the other hand, in the intake valve 1, the latent heat of vaporization increases as the fuel vaporizes, and the temperature in the combustion chamber 10 also decreases. When the intake valve 1 is opened, as shown in FIG. 3 (B), the fuel F in the air-fuel mixture flows into the combustion chamber 10, and the homogeneous air-fuel mixture spreads throughout the combustion chamber 10 and is in the liquid state. The amount of fuel adhering to the inner surface of the combustion chamber 10 is reduced. When this fuel is ignited, as shown in FIG. 3C, the ignitability is improved due to the air-fuel mixture, and the temperature in the combustion chamber 10 is lowered, so that normal flame propagation is prevented. Until completion, the pre-combustion reaction of the unburned mixture (end gas) is suppressed, there is little variation in the combustion period, and knocking that occurs due to abrupt combustion of the end gas in front of the flame propagation is prevented. Further, if the temperature in the combustion chamber 10 is lowered, the fuel charging efficiency is also increased, the reduction in output and the increase in fuel consumption are prevented, and the thermal efficiency is improved by the early combustion.

  Thus, since it is preferable that the intake valve 1 has a high thermal conductivity so that the fuel vaporization promoting function can be sufficiently exerted, the present inventors have intensively studied, and as a result, have conducted heat of the constituent material of the intake valve 1. Focusing on the conductivity and fatigue strength, the inventors succeeded in deriving a predetermined relational expression regarding the thickness of the intake valve 1 (umbrella).

  If the thickness of the umbrella part is determined based on this relational expression, the umbrella part can be easily optimized, the function of smoothly opening and closing the high-temperature combustion chamber 10 which is the original function of the intake valve 1, and the function of promoting fuel vaporization The intake valve 1 that exhibits the above can be easily created.

  The relational expression for optimizing the thickness of the umbrella part was determined from the measurement results such as the damage state of the umbrella part, the fuel consumption, the inner surface temperature of the cylinder head when operating with various intake valves attached to the internal combustion engine. Therefore, the relationship between these individual measurement objects will be described below.

<Various intake valves>
Five types of materials were used as materials for the intake valve 1. The characteristics of thermal conductivity and high temperature strength of each material are as shown in Table 1 below. Here, since the high temperature strength is fatigue strength at a high temperature of 250 ° C., it is hereinafter referred to as high temperature fatigue strength. This high temperature fatigue strength is obtained after holding a test piece made from each material at 250 ° C. for 100 hours. It is the value measured using the Ono type rotary bending test.

  In manufacturing the intake valve 1 using each material, as shown in FIG. 2, the contact surface 2c is circumscribed around the intersection O between the center line of the valve shaft 3 and the combustion chamber side surface 2a of the umbrella portion 2. A plurality of types of intake valves 1 having different thicknesses of the umbrella portions 2 were produced by changing the minimum radius r of the circumscribed circle. The other conditions such as the diameter D1 of the umbrella part 2 and the diameter d of the valve shaft 3 were the same.

  Specifically, the diameter D1 of the umbrella part 2 is 31.7 mm, the outermost peripheral diameter D2 of the connecting surface 2c is 28.8 mm, and the diameter d of the valve shaft 3 is 5.3 mm.

  Incorporating each intake valve into an actual engine and measuring the damage state of the umbrella 2, the fuel consumption, and the inner surface temperature of the cylinder head, the engine operation time is 4 hours, and the accelerator is fully open (WOT, The engine rotation speed was changed to 1200 rpm, 2000 rpm, 4000 rpm, and 6400 rpm every time 1 hour from the start of the test, and the rotation speed in each section time was constant.

<Umbrella damage>
The umbrella part 2 was damaged by visual observation. The results are shown in Table 2 and FIG.

Here, the thickness of the umbrella part 2 is expressed using a ratio β (= r / D1 ) of the minimum radius r to the diameter D1 of the umbrella part 2.

  As can be seen from Table 2, in the rapidly solidified aluminum alloy with comparatively low high-temperature fatigue strength as document 5, no damage was observed in the umbrella part 2 when β ≧ 0.2, but failure occurred when β ≦ 0.15. Was recognized. In S45C of Document 3, which has higher high-temperature fatigue strength than the rapidly solidified aluminum alloy, no damage was observed in the umbrella part 2 when β ≧ 0.15, but damage was observed when β ≦ 0.13. In the titanium alloy of Document 1 having a higher high-temperature fatigue strength than S45C, no damage was observed in the umbrella part 2 when β ≧ 0.13, but damage was observed when β ≦ 0.12.

  That is, it was found that the thicker the umbrella part 2 (the larger the value of β), the more difficult it is to break, and when the umbrella part 2 has the same thickness, the higher the high-temperature fatigue strength, the harder it is to break.

As shown in FIG. 5, the horizontal axis represents the high temperature fatigue strength (x) and the vertical axis represents the thickness (β) of the umbrella part 2, when there is no damage (OK zone) and when the damage occurs (NG When the boundary line with the zone) is shown in a graph, a curve A is obtained. If the relationship between the high temperature fatigue strength (x) and the thickness (β) of the umbrella portion is obtained from this curve A, the following formula 2 is obtained.

Therefore, when the high temperature fatigue strength (x) and the thickness of the umbrella part (β) are determined so as to satisfy the mathematical formula 2 , the umbrella part 2 can be made to be excellent in fracture strength characteristics without damage. become.

<Fuel consumption>
FIG. 6 is a graph showing the fuel consumption of each material. Next, as a result of testing the fuel consumption for each material, the results shown in FIG. 6 were obtained. In FIG. 6, the vertical axis represents the fuel consumption rate (%), and the horizontal axis represents the ratio of α / β. α is a heat transfer coefficient (W / m · K), and α / β corresponds to a heat transfer state corresponding to the thickness of the umbrella 2, that is, a temperature reduction capability in the combustion chamber 10.

As is clear from FIG. 6, the fuel consumption rate is lower as α / β is larger. When α / β is 250 or more, the fuel consumption reduction rate is 2% or more, and the fuel consumption rate is significantly reduced. Turned out to be. As a result, the larger α / β is, the higher the temperature reduction effect in the combustion chamber is, and the fuel consumption is reduced. Therefore, the thermal conductivity α and the thickness of the umbrella portion (β) are satisfied so as to satisfy the following Equation 3. If it is determined, it is possible to obtain an intake valve that is excellent in thermal conductivity and can obtain a significant fuel saving effect of 2% or more.

When this Equation 3 is combined with Equation 2 , the relationship of the following Equation 4 is established.

  When the thickness (β) of the umbrella part 2 is determined by using Equation 4, the high temperature fatigue strength is excellent, the thermal conductivity is improved, the internal temperature of the combustion chamber is lowered, the fuel consumption rate can be reduced, and the engine It is possible to obtain an intake valve with improved thermal efficiency and knocking resistance.

<Inner surface temperature of cylinder head>
Moreover, the internal surface temperature of the cylinder head was measured for each material. As the inner surface temperature of the cylinder head 6, the inner surface temperature of the cylinder head at an intermediate position between the exhaust hole provided with the exhaust valve and the spark plug 4 was measured. As a result, Table 3 and FIG. 7 were obtained.

  Table 3 shows the measured inner surface temperature of the cylinder head in terms of the thermal conductivity (α) of the material and the thickness (β) of the umbrella 2. As shown in Table 3, if the thickness (β) of the umbrella part 2 is the same, the higher the thermal conductivity α, the lower the inner surface temperature of the cylinder head and the thinner the umbrella part 2 (β is The smaller the temperature, the lower the inner surface temperature of the cylinder head.

  FIG. 7 shows the relationship between the value (α / β) of the ratio of the thermal conductivity (α) to the thickness (β) of the umbrella part and the inner surface temperature of the cylinder head, and as α / β increases. The inner surface temperature has decreased. Therefore, it can be seen that the inner surface temperature of the cylinder head decreases as the thickness of the umbrella portion 2 decreases (β decreases) and the thermal conductivity increases (α increases).

  That is, as shown in FIG. 3A, the fuel F accumulated on the back side when the intake valve 1 is closed becomes an air-fuel mixture in the intake passage 9 when the temperature of the umbrella portion 2 of the intake valve 1 rises. Vaporization promoting function is improved. On the other hand, with the vaporization of the fuel, the latent heat of vaporization of the intake valve 1 increases, thereby lowering the temperature in the combustion chamber 10.

  As shown in FIG. 3B, when the intake valve 1 is opened and the air-fuel mixture flows into the combustion chamber 10, a homogeneous air-fuel mixture spreads throughout the combustion chamber 10. When this fuel is ignited, as shown in FIG. 3C, the temperature in the combustion chamber 10 is lowered, and therefore, the pre-combustion reaction of the unburned mixture (end gas) until normal flame propagation ends. Is suppressed, there is little variation in the combustion period, knocking caused by abrupt combustion of the end gas in front of the flame propagation is prevented, and if the temperature in the combustion chamber 10 decreases, the fuel charging efficiency increases. As a result, a decrease in output and an increase in fuel consumption are prevented, and the thermal efficiency is improved by accelerating combustion. In addition, since the volumetric efficiency is improved when the thickness (β) of the umbrella portion is reduced, the fuel charging efficiency is further improved.

<Fuel vaporization rate>
FIG. 8 is a graph showing the relationship between the fuel vaporization rate and α / β. As described above, when α / β increases, the inner surface temperature of the combustion chamber 10 decreases, the fuel charging efficiency increases, and the reduction in output and increase in fuel consumption are prevented. The relationship with the fuel vaporization rate was also verified. As a result, as shown in FIG. 8, it was proved that the fuel vaporization rate was improved as α / β increased.

FIG. 9 is a graph showing the relationship between the fuel consumption rate and the fuel vaporization rate. Vaporization of the fuel F accumulated on the back side of the umbrella portion 2 is directed to the point that greatly affects the fuel consumption was also verified the relationship between the fuel evaporation rate and fuel consumption rate. As shown in FIG. 9, when the fuel vaporization rate is about 38% or more, the reduction rate of the fuel consumption is 0.5% or more, and it has been demonstrated that the reduction of the fuel consumption rate is remarkable.

  FIG. 10 is a graph showing the relationship between the fuel consumption rate and α / β. FIG. 8 demonstrates that the fuel vaporization rate increases as α / β increases, but the relationship between the fuel consumption rate and α / β was also verified. As a result, as shown in FIG. 10, when α / β is 175 or more, the fuel consumption reduction rate is 0.5% or more, and it is proved that the rate of reduction of the fuel consumption rate is large.

From the results, so as to satisfy the following formula 5, when the determined thermal conductivity (alpha) and the thickness of the umbrella portion (beta), will be able to reduce the fuel consumption rate.

Therefore, if the thermal conductivity (α) and the thickness of the umbrella portion (β) of the intake valve are determined so as to satisfy Formula 1 obtained by combining Formula 2 and Formula 5, the fuel consumption rate is more reliably ensured. Lower.

Therefore, in determining the thickness (β) of the umbrella portion of the intake valve, when the purpose is to reduce the fuel consumption rate, Formula 1 is used, and the high temperature fatigue strength and the high thermal conductivity of the engine are used. Formula 4 may be used to achieve excellent thermal efficiency and knock resistance.

  In particular, in order to obtain an intake valve excellent in engine thermal efficiency and knock resistance, it is better to use a material having a higher thermal conductivity (α) and a material having a higher high temperature fatigue strength (x). As apparent from Table 3, for example, an aluminum alloy (Document 4) or a rapidly solidified aluminum alloy powder (Document 5) is preferable.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. For example, in the above-described embodiment, the intake valve 1 is a flat head valve, but is not necessarily limited thereto, and may be various types of intake valves such as a bowl shape and a tulip shape.

It is sectional drawing which shows the intake valve part for internal combustion engines which concerns on embodiment of this invention. It is explanatory drawing of the same intake valve. FIG. 4 is a schematic cross-sectional view showing the fuel vaporization function of the intake valve in stages, where (A) is a fuel storage state, (B) is a state in which combustion is supplied to the combustion chamber, and (C) is a combustion state in the combustion chamber. Each is shown. It is a schematic sectional view showing the fuel vaporization function of a conventional intake valve step by step, (A) is a fuel storage state, (B) is a state in which combustion is supplied to the combustion chamber, (C) is a combustion in the combustion chamber Each state is shown. It is a graph which shows the measurement result of the damage state of an umbrella part. It is a graph which shows the fuel consumption of each data. It is a graph which shows the measurement result of the cylinder head inner surface temperature. It is a graph which shows the relationship between a fuel vaporization rate and (alpha) / (beta). It is a graph which shows the relationship between a fuel vaporization rate and a fuel consumption rate. It is a graph which shows the relationship between a fuel consumption rate and (alpha) / (beta).

Explanation of symbols

1 ... intake valve for internal combustion engine,
2 ... Umbrella,
2a ... Combustion chamber side surface of umbrella part,
2b ... The valve seat surface of the umbrella part,
2c: Contact surface,
3 ... Valve shaft,
D ... Umbrella diameter,
r: Minimum radius of the circumscribed circle from the center of the umbrella to the contact surface,
x: Fatigue strength of the material of the umbrella at 250 ° C,
α… The thermal conductivity of the umbrella material,
β: Ratio of the minimum radius r to the umbrella diameter D (= r / D).

Claims (4)

An internal combustion engine comprising an umbrella part and a valve shaft, the umbrella part having a combustion chamber side surface, a valve seat surface formed on an outer peripheral surface, and an arc-shaped connecting surface extending from the valve seat surface to the valve shaft An intake valve for an engine,
A ratio β (= r / D ₁ ) between a minimum radius r of a circumscribed circle that circumscribes the connecting surface centering on an intersection of the valve shaft center line and the combustion chamber side surface, and a diameter D _{1 of the} umbrella portion, An intake valve for an internal combustion engine characterized by satisfying the following mathematical formula 1 .
Where α is the thermal conductivity of the umbrella material
x: Holding the test piece of the constituent material of the intake valve at 250 ° C. for 100 hours
Fatigue strength measured by rotating bending test after 2. The intake valve for an internal combustion engine according to claim 1, wherein the β satisfies the following formula 2 .
  The intake valve for an internal combustion engine according to claim 1, wherein the umbrella portion is formed of an aluminum alloy.   The intake valve for an internal combustion engine according to claim 2 or 3, wherein the umbrella portion is formed of rapidly solidified aluminum alloy powder.