JP7817846B2 - Cylinder block - Google Patents

Description

This invention relates to an engine cylinder block and is characterized by the structure of the blow-by gas passage.

In gasoline and diesel engines, a phenomenon occurs in which blow-by gas (PCV gas) blows through the gap between the piston and cylinder bore into the crankcase during the combustion process. To address this issue, the blow-by gas is recirculated to the intake system to return unburned gas to the cylinder bore, but because the blow-by gas contains oil, an oil separator (gas-liquid separation chamber) is installed midway through the recirculation of the blow-by gas to capture oil mist.

The placement of the oil separator can be broadly divided into two cases: one on one side of the cylinder block (see, for example, Patent Document 1), and one on the head cover (see, for example, Patent Document 2). When the oil separator is placed on the head cover, the volume of the oil separator can be increased, resulting in excellent oil collection performance.

When the oil separator is installed in the head cover, a blow-by gas passage is formed in the cylinder block, penetrating it vertically. The blow-by gas passage in the cylinder block and the blow-by gas passage in the head cover are connected via the cylinder head, and the blow-by gas is guided to the oil separator.

JP 2012-092729 A Japanese Patent Application Laid-Open No. 2009-250159

Hybrid engines are becoming more popular to improve fuel economy and reduce carbon dioxide emissions, but hybrid engines tend to generate more blow-by gas than conventional engines due to the increased frequency of high-load operation for charging and the increased frequency of cold operation in low-temperature environments. This raises concerns that the oil separator in the head cover may not be able to capture all the oil, causing oil mist to spray out of the PCV valve.

Furthermore, when the amount of blow-by gas generated increases, the blow-by gas and oil mist tend to mix, generating foamy mist, which can clog the blow-by gas passage in the cylinder block, blocking the passage or restricting the flow of blow-by gas through the passage. When this phenomenon occurs, the intake negative pressure causes a sudden rise in negative pressure in the oil separator, and a large amount of foamy mist containing oil in the blow-by gas passage is sucked into the oil separator, further deteriorating the oil mist collection performance.

In this regard, it would be possible to increase the volume of the oil separator by making the head cover larger, but doing so would raise new issues such as increased costs and weight, which would worsen fuel economy.

The present invention was made against this backdrop, and aims to disclose technology that can deal with increased blow-by gas using a simple structure.

The present invention is
"A cylinder block in which a blow-by gas passage is formed in part of the peripheral wall, the lower end of which opens into the crank chamber and the upper end of which opens onto the upper surface."
This cylinder block is intended for:
"At least a part of the blow-by gas passage is formed with an upper narrowed portion whose cross-sectional area at the upper end is smaller than that at the lower end,
The upper narrowed portion has a plurality of stepped discontinuous portions with abrupt changes in cross-sectional area, each having a different height.
In this basic configuration,
"An expansion chamber is formed in the blow-by gas passage at a height position located to the side of the cylinder bore, extending from the outer surface of the cylinder block toward the cylinder bore so as to cross the blow-by gas passage, and the open end of the expansion chamber is closed with a plug,
Furthermore, the discontinuous portions of the plurality of stages are formed in a portion below the extension chamber.
It has the following characteristics.

In the present invention, it is possible to form the entire length of the blow-by gas passage as a narrowed portion at the top (widened portion at the bottom), but it is preferable to form at least a portion near the bottom as a narrowed portion at the top. In other words, it is preferable for the widest part to open into the crankcase.

In claim 2 , in claim 1 ,
The configuration adopted is that "the multiple-stage discontinuous portion includes a first step portion and a second step portion, and the first step portion and the second step portion are formed on opposing surfaces across the axis of the blow-by gas passage."

In the present invention, first, by forming an upper narrowing section (or a lower widening section) in the blow-by gas passage, the flow velocity of blow-by gas entering the blow-by gas passage can be reduced. Therefore, even if oil mist turns into foam inside the crankcase, this foamy oil mist can be prevented or significantly suppressed from entering the blow-by gas passage. This prevents or significantly suppresses the phenomenon of the blow-by gas passage being blocked and the phenomenon of increased flow resistance of the blow-by gas.

In particular, aligning the lower end of the upper narrowing portion with the lower end of the blow-by gas passage and setting the opening area of the lower end of the blow-by gas passage to the largest possible size is advantageous, as it effectively prevents foamy oil mist from entering (being sucked up) into the blow-by gas passage.

Furthermore, in the present invention, by forming an upper narrowed portion in the blow-by gas passage, the opportunity for blow-by gas to come into contact with the inner surface of the upper narrowed portion is increased, thereby improving the oil collection function of the inner surface of the upper narrowed portion.

Furthermore, in the present invention, the upper tapered portion has multiple discontinuous portions, which causes blow-by gas flowing upward through the upper tapered portion to collide with the multiple discontinuous portions, increasing the opportunity for oil mist to come into contact with the inner surface of the upper tapered portion. In other words, the stepped discontinuous portions significantly enhance the effect of increasing oil mist capture achieved by forming the upper tapered portion.

In this way, the present invention can prevent or significantly suppress the flow of foamy oil mist into the blow-by gas passage, and can improve the oil collection function in the blow-by gas passage, so that even in engines that generate a large amount of blow-by gas, such as hybrid engines, the gas-liquid separation function of the oil separator can be ensured and the necessary ventilation performance can be ensured without increasing the size of the head cover.In fact, by forming the blow-by gas passage so that it widens downward, the thickness of the cylinder block can be reduced, thereby reducing its weight, which can also contribute to improving fuel efficiency.
In particular, when the first and second step portions are arranged to face each other as in claim 2 , a strong direction change effect is imparted to the blow-by gas, increasing the chances that the blow-by gas will come into contact with the blow-by gas passage, thereby greatly enhancing the oil mist collection effect (adhesion).

Furthermore, in the present invention , the flow velocity of blow-by gas decreases in the extension chamber as it ascends through the blow-by gas passage, increasing the opportunity for the blow-by gas to come into contact with the inner surface of the extension chamber, further improving the oil mist collection function. In other words, oil mist can be collected in two stages: in the upper narrowing section and in the extension chamber. There is no increase in flow resistance (increase in pressure loss) of the blow-by gas. Even if bubbly oil mist rises, it can be reliably captured in the extension chamber, effectively preventing the blow-by gas passage from being clogged with bubbly oil mist.

Furthermore, because the extension chamber is oriented to cross the blow-by gas passage, the blow-by gas is forced to enter the dead-end extension chamber, further improving the oil mist collection performance. In particular, if the blow-by gas passages are offset horizontally (in a direction intersecting the blow-by gas passage) above and below the extension chamber as in the embodiment, the blow-by gas is guided toward the inner part of the extension chamber without passing through it, which increases the opportunity for the blow-by gas to come into contact with the inner surface of the extension chamber, thereby significantly improving the oil mist collection function.

Furthermore, when the expansion chamber is formed in a position that crosses the blow-by gas passage as in the present invention , it has the effect of being able to reasonably increase the volume of the expansion chamber, the effect of being able to reduce the weight by reducing the cylinder block's thickness, and the effect of being able to transfer the heat of the cylinder bore to the blow-by gas during cold starting and cold operation, thereby promoting oil drainage.

The expansion chamber can be formed by a protrusion provided on the side mold when the cylinder block is cast, and the protrusion serves as a retaining member for the tip of the butt joint of the core pin of the blow-by gas passage that is inserted from above and below the cylinder block during casting. Furthermore, even if burrs are generated by providing the protrusion, the butt joint of the core pin can be deburred by drilling or punching after casting, so processing is easy and does not cause any manufacturing problems.

FIG. 1 is a bottom view of the embodiment. 2A is a cross-sectional view taken along line II-II in FIG. 1. FIG. 1A is a cross-sectional view taken along line IIIA-IIIA in FIG. 1, and FIG. 1B is a cross-sectional view taken along line IIIB-IIIB in FIG.

(1) Structure of the embodiment Next, an embodiment of the present invention will be described with reference to the drawings. This embodiment is applied to a hybrid engine. In the following, the terms "front-rear" and "left-right" are used to specify directions, but the front-rear direction is the crankshaft direction, and the left-right direction is the direction perpendicular to the crankshaft direction and the cylinder bore axis (the engine width direction). Regarding "front" and "rear," the side where the timing chain is located is referred to as the front, and the side where the transmission is located is referred to as the rear. Directions are indicated in the drawings as necessary.

The basic structure of the cylinder block 1 is the same as that of a conventional cylinder block, with multiple cylinder bores 2 aligned in the crankshaft direction. Partition walls 3 are formed between adjacent cylinder bores 2, and crank journal holders 5 provided on end walls 4 and partition walls 3 rotatably hold crank journals of a crankshaft 6 via crank caps 7 and metal bearings 8. The crank caps 7 are fixed to the cylinder block 1 with bolts 9, and the underside of the cylinder block 1 is provided with a group of female-threaded holes 9a into which the crank cap bolts 9 are screwed.

An oil pan 10 is fastened to the underside of the cylinder block 1 with oil pan bolts 11. Therefore, a group of oil pan female threaded holes 12 into which the oil pan bolts 11 are screwed is arranged on the underside of the flange provided on the side wall 1a of the cylinder block 1.

Although only a portion is shown in Figure 2, a cylinder head 13 is fastened to the top surface of the cylinder block 1 by a group of head bolts 15 via a gasket 14. Furthermore, the cylinder block 1 is formed with a water jacket 16 that surrounds the group of cylinder bores 2.

A blow-by gas passage 17 is formed to penetrate vertically through the intake-side side wall 1a of the cylinder block 1 in a portion that overlaps with the rear partition wall 3. As shown in Figure 2, the blow-by gas passage 17 is composed of an expansion chamber 18 located at an intermediate height, a first portion 19 located below the expansion chamber 18, and a second portion 20 located above the expansion chamber 18. Note that the second portion 20 is not visible in the bottom view of Figure 1.

The cylinder block 1 is manufactured by casting or die-casting using an upper mold overlapping from above, an upper mold overlapping from below, and multiple horizontal molds overlapping from the sides based on the product. The first portion 19 of the blow-by gas passage 17 is formed by a core pin (or protrusion) provided on the lower mold, the second portion 20 is formed by a core pin (or protrusion) provided on the upper mold, and the expansion chamber 18 is formed by a protrusion provided on one of the horizontal molds.

The horizontal protrusions used to form the expansion chamber 18 serve as retaining members against which the tips of the core pins on the upper and lower dies come into contact, making it easy to form the blow-by gas passage 17 by casting or die-casting. Furthermore, even if burrs form where the core pins on the upper and lower dies overlap with the horizontal protrusions, they can be removed by drilling or punching after molding, making post-processing easy.

In this embodiment, the first portion 19 corresponds to the upwardly tapered portion described in the claims. The second portion 20 is depicted as straight, but in reality, it is slightly tapered upward due to the draft angle of the cast pin used during manufacturing.

The second portion 20 is positioned closer to the cylinder bore 2 than the first portion 19. Therefore, the first portion 19 is offset relative to the second portion 20. In this case, in a plan view (and bottom view), the first portion 19 and the second portion 20 are offset so as not to overlap across the expansion chamber 18, but they may also be configured so as to partially overlap. In addition, the plan area (cross-sectional area) of the second portion 20 is smaller than the plan area of the upper end of the first portion 19.

The expansion chamber 18 has a circular horizontal hole shape that crosses the blow-by gas passage 17 and opens toward the outer wall of the cylinder block 1, with the open end closed by a plug 21. The expansion chamber 18 is composed of a main portion 18a that communicates with the first portion 19 and the second portion 20 and a rear portion 18b that has a smaller diameter than the main portion 18a, and the rear portion 18b extends below the head bolt 15 and the water jacket 16. Therefore, the expansion chamber 18 is located at the same height as the lower portion of the cylinder bore 2. The cross-sectional area of the main portion 18a that constitutes the expansion chamber 18 (the cross-sectional area when the expansion chamber 18 is cut vertically) is larger than the plan area of the upper end of the first portion 19 (see FIG. 3B in particular).

The first portion 19 of the blow-by gas passage 17 is formed across the partition wall 3 and outer wall of the cylinder block 1, and is basically shaped approximately symmetrically in the front-to-rear direction across the center line that divides the partition wall 3 into front and rear halves.

In a longitudinal cross section cut along a plane including the centerline of the partition wall 3, the inner surface of the first portion 19 is non-linear. That is, as shown in Figures 3(A) and 2, the first portion 19 is composed of a lower stage 23 whose inner surface 23a is generally parallel to the axis of the cylinder bore 2, a middle stage 24 whose inner surface 24a is continuous with the upper end of the lower stage 23 and slopes outward, and an upper stage 25 whose inner surface 25a is continuous with the upper end of the middle stage 24 and is generally parallel to the axis of the cylinder bore 2.

In a longitudinal cross-sectional view taken along a plane including the centerline of the partition wall 3 (as shown in Figure 3(A)), the outer surfaces 23b, 24b, and 25b of the steps 23, 24, and 25 are continuous as a series of inclined surfaces tilting inward at a constant rate.

Therefore, the first portion 19 of the blow-by gas passage 17 narrows upward (widens downward) when cut along a plane including the centerline of the partition wall 3. The inner surface 23a of the lower section 23 and the inner surface 25a of the upper section 25 are slightly tilted outward due to the draft angle applied to the core pins during manufacturing.

3(B) (longitudinal side cross-sectional view) in which the first portion 19 is cut along a vertical plane parallel to the crank axis, the rear surfaces 23c, 24c of the lower stage 23 and the middle stage 24 are continuous as inclined surfaces tilted forward at a certain rate, but the front surface 23d of the lower stage 23 and the front surface 24d of the middle stage 24 are discontinuous such that the front surface 24d of the middle stage 24 is shifted backward. Therefore, a first step 26, which is an example of a discontinuous portion as defined in the claims, is formed at the boundary between the two.

In the state shown in Figure 3(B), the relationship between the middle section 24 and the upper section 25 is such that the front surface 24d of the middle section 24 and the front surface 25d of the upper section 25 are continuous as an inclined surface tilted backward at a certain rate, but the rear surface 24c of the middle section 24 and the rear surface 25c of the upper section 25 are discontinuous, with the rear surface 25c of the upper section 25 shifted forward. Therefore, the boundary between the two also forms a second step portion 27, an example of a discontinuous portion as defined in the claims.

As shown in FIG. 1, the lower step 23 of the first section 19 expands to surround one of the oil pan female threaded holes 12. Therefore, the lower step 23 has outward bulges 23e that expand outward in the left-right direction on both the front and rear sides of the oil pan female threaded hole 12.

2, in a longitudinal rear view in which the outer surface of the outward bulging portion 23e of the lower step portion 23 appears, the outer surface 24b of the middle step portion 24 and the outer surface 25b of the upper step portion 25 are inclined inward at the same rate, while the outer surface 23b' of the lower step portion 23 is shifted outward relative to the outer surface 24b of the middle step portion 24. Therefore, a first step portion 26 also exists at the boundary between the outer surface 23b' of the outward bulging portion 23e of the lower step portion 23 and the outer surface 24b of the middle step portion 24.

As shown in Figure 2, the cylinder head 13 also has a blow-by gas passage 17 that communicates with the blow-by gas passage 17 of the cylinder block 1. A head cover (not shown) is fixed to the top surface of the cylinder head 13, and the head cover also has a blow-by gas passage that communicates with the blow-by gas passage 27 of the cylinder head 13. The blow-by gas passage of the head cover communicates with an oil separator formed by the head cover and a baffle plate. The blow-by gas that passes through the oil separator flows into the intake system (e.g., the intake manifold) via the PCV valve.

As shown by the dashed line in Figure 2, a baffle plate 28 against which the blow-by gas collides can be placed below the blow-by gas passage 17. The baffle plate 28 can be installed independently, or it can be attached to the oil level control baffle plate.

(2) Summary This embodiment has the above-described configuration, and compared to a conventional non-hybrid engine, the cross-sectional area of the second portion 20 is the same as the conventional one, but the area of the lower end of the first portion 19 (the opening area of the lower end of the blow-by gas passage 17) is significantly increased.

Although the first portion 19 is generally tapered upward , the opening area at the lower end of the first portion 19 is larger than in the conventional case, and therefore, as shown by the arrow in Fig. 2, the flow rate of the blow-by gas when it flows into the first portion 19 is significantly lower than in the conventional case. Therefore, even if the blow-by gas becomes turbid with the oil mist and a large amount of foamy oil mist is generated in the crank chamber, the foamy oil mist has low buoyancy (because it is heavier than simple oil mist), so the flow of the foamy oil mist into the first portion 19 is prevented or significantly suppressed. This makes it possible to prevent the first portion 19 from becoming clogged.

Furthermore, in this embodiment, since the two step portions 26, 27 are formed, the blow-by gas that flows into the first portion 19 collides with the two step portions, the first step portion 26 and the second step portion 27, and is subjected to a direction change action, increasing the chance of contact with the first portion 19 and achieving a high oil mist collection effect. In particular, even if foamy oil mist flows into the first portion 19, it collides with the step portions 26, 27 and is destroyed, thereby reliably preventing the occurrence of a blockage phenomenon.

In particular, in this embodiment, the first step portion 26 and the second step portion 27 are disposed on both the front and rear sides (opposite each other), which provides a strong direction change effect to the blow-by gas, increasing the chances that the blow-by gas will come into contact with the first portion 19. Therefore, the oil mist capturing effect (adhesion) can be greatly improved.

More specifically, because the first portion 19 narrows upward as a whole, the flow velocity of the blow-by gas increases as it rises, but since the blow-by gas collides alternately with the front and rear step portions 26, 27 while increasing its flow velocity, the direction change action is ensured and the opportunity for oil mist to come into contact with the first portion 19 can be increased. In this respect as well, the oil mist collection effect is excellent.

Furthermore, in this embodiment, the extension chamber 18 is provided at a mid-height portion of the blow-by gas passage 17, so that the flow velocity of the blow-by gas that has passed through the blow-by gas passage 17 decreases in the extension chamber 18, increasing the chance of the blow-by gas coming into contact with the inner surface of the extension chamber 18. This allows a large amount of oil mist to be collected in the extension chamber 18.

In particular, when the first part 19 and the second part 20 are offset to the left and right across the expansion chamber 18, as in the embodiment, the blow-by gas flows into the expansion chamber 18 and then changes direction in a crank-like manner, becoming turbulent, thereby further increasing the opportunity for oil mist to come into contact with the inner surface of the expansion chamber 18 and significantly improving the oil mist collection function.

Furthermore, because the expansion chamber 18 has a deep portion 18b that is deeper inward than the second portion 20, blow-by gas that flows into the main portion 18a of the expansion chamber 18 tends to flow into the deep portion 18b of the expansion chamber 18. This further improves the oil mist collection effect. Also, because the deep portion 18b of the expansion chamber 18 is close to the inter-bore portion 1b, the heat from the cylinder bore 2 warms the blow-by gas, improving the adhesion of oil mist to the expansion chamber 18 during operation in a low-temperature environment.

Furthermore, because the cross-sectional area of the expansion chamber 18 is sufficiently larger than the cross-sectional area of the upper end of the first section 19 and the cross-sectional area of the lower end of the second section 20, there is no increase in flow resistance (increase in pressure loss) when the blow-by gas changes direction in the expansion chamber 18 and flows into the second section 20.

As described above, in this embodiment, even if a large amount of blow-by gas is generated or oil mist combines with the blow-by gas to form bubbles, the blow-by gas can be sucked up into the blow-by gas passage 17 without causing clogging of the blow-by gas passage 17, and a large amount of oil mist can be collected in the blow-by gas passage 17. Therefore, blow-by gas in which a large amount of oil mist has been collected can be sent to the oil separator provided in the head cover.

Therefore, in this embodiment, even in hybrid engines that generate a large amount of blow-by gas, the blow-by gas can be accurately processed without increasing the size of the head cover. In fact, the weight reduction achieved by increasing the volume of the blow-by gas passage 17 and by providing the expansion chamber 18 contributes to improved fuel economy.

One possible way to increase the volume of the first portion 19 in the blow-by gas passage 17 is to widen the lower end of the first portion 19 inward, but this would result in the partition wall 3 becoming thicker in parts.

In contrast, by expanding the lower step 23 of the first portion 19 in the circumferential direction of the oil pan female threaded hole 12, as in this embodiment, the area of the lower end of the first portion 19 can be increased without reducing the fastening strength between the oil pan 10 and the cylinder block 1 or adding parts that increase weight, such as adding a boss portion. This is also one of the advantages of this embodiment.

As described above, the extension chamber 18 exhibits a high oil collection effect, but if the extension chamber 18 is provided midway between the top and bottom of the blow-by gas passage 17, a considerable proportion of oil mist can be collected from the extension chamber 18 at a stage before the blow-by gas reaches the cylinder head 13 and dropped or trickled down from the first section 19. In other words, a considerable proportion of oil mist from the blow-by gas can be pre-treated in the first section 19 and the extension chamber 18. This reduces the burden on the oil separator provided in the head cover, and enables high oil collection performance to be achieved overall.

When the blow-by gas passage 17 is provided at the partition wall 3 as in this embodiment, the space below the blow-by gas passage 17 is covered from the inside by the crank cap 7, which has the advantage of preventing splashes generated by the rotation of the crankshaft 6 from directly entering the blow-by gas passage 17.

Although the embodiments of the present invention have been described above, the present invention can be embodied in various other ways. For example, the entire length of the blow-by gas passage can be formed so as to taper upward. The lower end of the blow-by gas passage can be formed straight, and the portion above that can be formed so as to taper upward. The discontinuous portion such as the stepped portion can be formed in three or more steps.

In the embodiment, the blow-by gas passage is formed in the side wall of the cylinder block 1, but the blow-by gas passage can also be formed in the end wall (front wall) of the cylinder block. The present invention can also be applied to cylinder blocks of non-hybrid engines.

The present invention can be embodied in a cylinder block, and therefore has industrial applicability.

REFERENCE SIGNS LIST 1 Cylinder block 1a Cylinder block side wall 2 Cylinder bore 3 Partition wall 4 End wall 6 Crankshaft 10 Oil pan 11 Oil pan bolt 12 Oil pan female threaded hole 13 Cylinder head 15 Head bolt 16 Water jacket 17 Blow-by gas passage 18 Expansion chamber 19 First section 20 Second section 21 Plug 23 Lower step of first section 24 Middle step of first section 25 Upper step of first section 26 First step section 27 Second step section

Claims (2)

A blow-by gas passage is formed in a part of the peripheral wall, the lower end of which opens to the crank chamber and the upper end of which opens to the upper surface .
an upper narrowed portion having a cross-sectional area at an upper end smaller than a cross-sectional area at a lower end is formed in at least a part of the blow-by gas passage,
a cylinder block in which a stepped discontinuous portion in which the cross-sectional area changes suddenly is formed at a plurality of levels with varying heights in the upper tapered portion,
an expansion chamber extending from an outer surface of the cylinder block toward the cylinder bore is formed in the blow-by gas passage at a height position located to the side of the cylinder bore so as to cross the blow-by gas passage, and an open end of the expansion chamber is closed by a plug;
The discontinuous portions of the plurality of stages are formed in a portion below the extension chamber.
Cylinder block. the plurality of step discontinuous portions include a first step portion and a second step portion, and the first step portion and the second step portion are formed on surfaces facing each other across an axis of the blow-by gas passage.
2. The cylinder block according to claim 1.