Patent Description:
Many industrial diesel engines and the like have a structure including a blow-by gas recirculation device configured to allow blow-by gas to pass through the inside of a cylinder head cover (hereinafter, abbreviated as a head cover) and then return to an intake path.

In the structure in which blow-by gas is allowed to pass through the inside of the head cover and then returned to the intake passage, a gas passage is generally provided on the upper side of a valve mechanism in the head cover. Since the gas passage inside the head cover tends to be a flat passage that is vertically narrow, an oil separator for trapping oil components from the blow-by gas is generally provided outside the head cover as a dedicated part (e.g., Patent Document <NUM>).

In the structure in which the oil separator is disposed on the side of a cylinder block, there is almost no limitation on space as inside the head cover, so that there is an advantage that the oil separator can have a sufficient capacity. However, the oil separator, which is a dedicated part, is added as an auxiliary machine of the engine, so that there arise the following problems.

That is, the size (bulk) of the entire engine tends to increase as much as the oil separator is attached. In addition, since the gas passage from the head cover to the intake passage, that is, an external pipe becomes large in length, the risk that the moisture contained in the blow-by gas may freeze in cold weather increases.

Patent Document <NUM>: <CIT> In addition, <CIT> and <CIT> disclose blow-by gas recirculation devices.

An object of the present invention is to provide a blow-by gas recirculation device that, while having a configuration in which a passage for blow-by gas is provided in a head cover and an oil separator is also provided, is improved, by devising a structure, in that an increase in size of an engine is suppressed and the risk of the freezing is avoided as much as possible by shortening the length of an external pipe for the blow-by gas.

In accordance with the present invention there is provided a blow-by gas recirculation device as claimed in claim <NUM>.

Other preferred or optional features are disclosed in the dependent claims, description and drawings.

According to the present invention, the oil separator is built into (housed in) the head cover, so that the bulk of the entire engine can be made smaller than a case where an oil separator is disposed outside the head cover as a dedicated part. Moreover, an external pipe for the blow-by gas from the head cover to the oil separator can be omitted, so that there is an advantage that the risk that the moisture in the blow-by gas may freeze in the external pipe in cold weather or the like is avoided.

Further, the blow-by gas outlet of the oil separator is overlapped on the blowby gas inlet portion of the pressure regulating valve provided on the blow-by gas outlet side of the head cover, so that a path that connects the separator and the pressure regulating valve becomes unnecessary, and a space necessary for disposing the separator and the pressure regulating valve, the space being minimized as much as possible, can be provided in the head cover.

As a result, it is configured such that the oil separator is provided in the head cover in a state of being overlapped on the passage for the blow-by gas and the pressure regulating valve, so that an increase in the size of an engine can be suppressed and the risk of the freezing can be avoided as much as possible by shortening the length of the external pipe for the blow-by gas, whereby an improved blow-by gas recirculation device can be provided.

Hereinafter, an embodiment of a blow-by gas recirculation device according to the present invention, when applied to an industrial diesel engine, will be described with reference to the drawings.

In a diesel engine E to be applied to industrial machines such as agricultural machines and construction machines, a cylinder head <NUM> is assembled on a cylinder block <NUM>, a cylinder head cover (hereinafter, abbreviated as a "head cover") <NUM> is assembled on the cylinder head <NUM>, and an oil pan <NUM> is assembled under the cylinder block <NUM>, as illustrated in <FIG>.

A transmission case <NUM> is assembled to a front end portion of the cylinder block <NUM>, an engine cooling fan <NUM> is disposed in a front portion of the transmission case <NUM>, and a flywheel housing <NUM> is disposed in a rear portion of the cylinder block <NUM>. The upper half portion of the cylinder block <NUM> is formed in a cylinder 1A, and the lower half portion is formed in a crankcase 1B.

A drive pulley <NUM> to be attached to a shaft end of a crankshaft (not illustrated), a fan pulley 6A for driving the engine cooling fan <NUM>, a transmission belt <NUM> extending over a passive pulley 9A of a dynamo (alternator) <NUM>, a water flange <NUM>, and the like are mounted on a front portion of the engine E. An exhaust manifold <NUM>, a supercharger <NUM>, a starter <NUM>, an EGR cooler <NUM>, and the like are mounted on the left side of the engine E. An intake manifold <NUM>, an oil filter <NUM>, and the like are mounted on the right side of the engine E. A compressor downstream suction passage (secondary air passage) <NUM> (see <FIG>) is disposed in an upper portion of the engine E.

An exhaust gas treatment device <NUM> is provided in an upper portion and a rear portion of the engine E. The exhaust gas treatment device <NUM> has an exhaust gas primary treatment device (DPF, etc.) 19A disposed in an upper portion of the flywheel housing <NUM> in the rear portion of the engine E, and an exhaust gas secondary treatment device (SCR, DOC, etc.) 19B disposed close to the rear portion of the head cover <NUM> in the upper portion of the engine E. The exhaust gas treatment device <NUM> is supported by a mounting frame <NUM> bolted to the cylinder block <NUM>.

An intake passage a is a general term including a compressor upstream suction passage <NUM>, the compressor downstream suction passage <NUM>, and the intake manifold <NUM>. The compressor upstream suction passage <NUM> is the intake passage a formed of a pipe connecting an air cleaner (not illustrated) and a compressor housing 12A of the supercharger (turbocharger) <NUM>. The compressor downstream suction passage <NUM> is the intake passage a formed of a pipe connecting the compressor housing 12A and the intake manifold <NUM>.

As illustrated in <FIG> and <FIG>, a blow-by gas recirculation device A that returns blow-by gas in the crankcase 1B to the intake passage a by using a blow-by gas passage w including an in-cover gas passage 3A (see <FIG>) formed inside the head cover <NUM> is mounted on the engine E. The blow-by gas passage w has a gas duct <NUM> connecting the upper left side of the head cover <NUM> and the compressor upstream suction passage <NUM>. The gas duct <NUM> is formed in a curved pipeline connecting a blow-by gas outlet (not illustrated) of the head cover <NUM> and a straight pipe <NUM>.

As illustrated in <FIG> and <FIG>, the compressor upstream suction passage <NUM> includes a connecting pipe <NUM> externally fitted to an inlet cylinder (not illustrated) of the compressor housing 12A, the straight pipe <NUM> internally fitted and connected to the connecting pipe <NUM>, and an air pipe (not illustrated) connecting the straight pipe <NUM> and the air cleaner (not illustrated). In the straight pipe <NUM>, an inrush pipe (not illustrated) serving as a terminal portion of the blow-by gas passage w is formed in a laterally branched shape, and a heating mechanism <NUM> capable of warming the inrush pipe portion in the straight pipe <NUM> by using cooling water r is integrally provided.

Next, the configuration of the portion of the head cover <NUM> in the blow-by gas recirculation device A will be described. As illustrated in <FIG> and <FIG>, the in-cover gas passage 3A mainly includes an oil separator <NUM> and a positive crankcase ventilation (PCV) valve (an example of a pressure regulating valve) B housed in an upper portion of the head cover <NUM> covering a valve mechanism F. The oil separator <NUM> that traps and removes oil from the blow-by gas and the PCV valve B provided in a gas outlet portion (an example of the "outlet side of the blow-by gas passage") in the head cover <NUM> are configured such that a separator outlet <NUM>, which is an outlet for the blow-by gas in the oil separator <NUM>, is overlapped on a blow-by gas inlet portion <NUM> of the PCV valve B.

As illustrated in <FIG>, the oil separator <NUM> has, in the head cover <NUM>, an outer shell shape similar to an inner upper portion of the head cover <NUM> so as to be fitted into a space portion formed in a vertical clearance between a top wall 3a and the valve mechanism F without a gap (or with a small gap). The oil separator <NUM> has a separator inlet <NUM> that opens downward in the rear portion thereof, an oil filter <NUM> for trapping oil, a droplet collecting portion <NUM> that collects the trapped oil and drops them from a through hole 37a, and a downward protrusion (an example of an oil dropping portion) <NUM> that drops the collected oil into the engine. The separator outlet <NUM> is a substantially D-shaped hole (see <FIG>) located above the downward protrusion <NUM>.

As illustrated in <FIG>, the oil separator <NUM> is formed in a long shape along the longitudinal direction (front-rear direction) of the head cover <NUM>, and can be divided into a separator rear portion 25A having the separator inlet <NUM>, a separator middle portion 25B having the droplet collecting portion <NUM>, and a separator front portion 25C having the separator outlet <NUM>. The oil filter <NUM> is located at a boundary between the separator rear portion 25A and the separator middle portion 25B, and the downward protrusion <NUM> is formed in a lower portion of the separator front portion 25C.

The separator rear portion 25A is provided with a plate-shaped wall 25a protruding rearward in a horizontal posture on the upper side of the separator inlet <NUM> located in the front portion of the separator rear portion 25A. Therefore, it is configured such that the blow-by gas that has entered from the separator inlet <NUM> is once detoured backward and then moved toward the oil filter <NUM> located in the upper front portion.

The oil filter <NUM> is configured to have an impactor structure including a plurality of nozzles 36a vertically lined in a horizontal posture and a collision plate 36b in a vertical posture disposed in front of the nozzles. The blow-by gas is accelerated by passing through the nozzle 36a, and when the accelerated blow-by gas vigorously collides with the collision plate 36b, the oil contained in the blow-by gas is separated from the gas and dropped. Note that an orifice or a small diameter portion having a constant diameter may be adopted instead of the nozzle 36a, and in short, a means (passage) for increasing the speed of the blow-by gas may be adopted. These (nozzle, orifice, small diameter portion) may be collectively expressed as a speed increase path.

The separator middle portion 25B is a portion where the oil that is trapped by the oil filter <NUM> and drops is dropped from the droplet collecting portion <NUM> to a shallow bottom wall. The separator middle portion 25B is configured such that the oil that hits a wall 25c above the boundary with the separator front portion 25C and drops can also be guided to the droplet collecting portion <NUM>. The oil that has dropped from the droplet collecting portion <NUM> can be stored on a shallow bottom wall 25b leading to the downward protrusion.

The separator front portion 25C leading to the separator middle portion 25B is provided with the separator outlet <NUM> in the upper portion, the downward protrusion <NUM> in the lower portion, and a partition wall 25d for forming the droplet collecting portion <NUM> in the vertical middle. In the separator front portion 25C, the separator outlet <NUM> is located at the highest position, and the height position of the upper surface (peripheral portion 27a described later) of a separator outlet 27d is set to be lower than the height positions of the upper surface of the separator rear portion 25A and the upper surface of the separator middle portion 25B, the height positions being the same as each other, for convenience in disposing the pressure regulating valve B.

As illustrated in <FIG>, an extension protrusion 38A further protruding downward is formed in the downward protrusion <NUM>, and a check valve <NUM> is provided below the extension protrusion. The oil dropped from the droplet collecting portion <NUM> can be stored in the downward protrusion <NUM> to some extent, and is returned into the engine from the lower end of the extension protrusion 38A through the check valve <NUM>. The valve mechanism F includes functional parts such as a camshaft <NUM>, a rocker arm <NUM>, and a supply/discharge valve <NUM>, and the downward protrusion <NUM> is provided to protrude toward a gap portion avoiding these functional parts.

As illustrated in <FIG>, a peripheral portion 52a of a surrounding space portion <NUM>, which is the blow-by gas inlet portion <NUM> of the pressure regulating valve B, and the peripheral portion 27a of the separator outlet <NUM> are in vertical contact with each other. As a result, the surrounding space portion <NUM> and the separator outlet <NUM> are configured to communicate with each other. Therefore, in the head cover <NUM>, the blow-by gas that has entered the oil separator <NUM> from the separator inlet <NUM> flows in the order of the oil filter <NUM>, the separator outlet <NUM>, the pressure regulating valve B, and a gas outlet portion <NUM>. In addition, the oil trapped by the oil separator <NUM> is dropped into the engine from the extension projection 38A, but may be dropped from the separator inlet <NUM>.

As illustrated in <FIG>, the PCV valve B acting on the in-cover gas passage 3A is configured in the head cover <NUM> in a state of using the top wall 3a of the head cover <NUM>. As illustrated in <FIG>, the PCV valve B is a diaphragm valve, and a cover lid <NUM> made of sheet metal material that enables assembly and removal of a diaphragm <NUM> is detachably attached to the top wall 3a of the head cover <NUM> by screwing or the like. By providing the PCV valve B on the head cover <NUM> in a state of being exposed to the outside, there is an advantage that maintenance of the inside of the valve (replacement of the diaphragm <NUM> or the like) can be performed by attaching and detaching the cover lid <NUM> without removing the head cover <NUM>.

In the blow-by gas passage w of the blow-by gas recirculation device A, the configuration in which the PCV valve B having a diaphragm valve structure (may be referred to as a breather valve) is provided in the head cover <NUM> is a well-known technique in <CIT>, <CIT>, and the like, and here the structure of the PCV valve B will be described briefly.

The PCV valve B is provided on the top wall 3a using a valve installation hole <NUM> formed in the top wall 3a, and the blow-by gas that has passed through the in-cover gas passage 3A and the PCV valve B flows out from the gas outlet portion <NUM> formed below the valve installation hole <NUM> in a state of facing left front, and flows to the gas duct <NUM>. That is, the PCV valve B is disposed in the gas outlet portion <NUM> in a state where most constituent elements thereof are formed on the top wall 3a itself. Note that in <FIG> and <FIG>, reference numeral <NUM> denotes an annular valve seat, reference numeral <NUM> denotes a surrounding space portion communicating with the in-cover gas passage 3A, reference numeral <NUM> denotes a discharge passage, and reference numeral 53a denotes a discharge passage inlet. In addition, a plurality of nut portions 3c for bolting the cover lid <NUM> to the top wall 3a are formed near the periphery of the valve installation hole <NUM>.

As illustrated in <FIG>, a temperature raising mechanism C capable of warming the PCV valve B is provided in the head cover <NUM>. The temperature raising mechanism C is configured by forming a flow path <NUM> for flowing the cooling water r near the PCV valve B on the top wall 3a of the head cover <NUM>. The flow path <NUM> is configured by forming a deep hole (lateral hole) that opens on the right side surface and extends leftward and laterally toward the PCV valve B in a thick width of the top wall 3a. The flow path <NUM> having a deep hole shape includes a deep hole portion 44A that extends laterally (leftward) and deeply in the rear portion of the hole, a shallow hole portion 44B that extends forward from the left-right intermediate portion of the deep hole portion 44A, and an opening portion 44C that is long in the front-rear direction and extends over the opening sides of both the hole portions 44A and 44B. The flow path <NUM> is formed in a lateral hole having an L shape in plan view (see <FIG>).

As illustrated in <FIG>, <FIG>, and <FIG>, a lid body <NUM> capable of closing the opening portion 44C of the flow path <NUM> is detachably attached to the head cover <NUM> by two bolts <NUM> and <NUM>. The lid body <NUM> is configured by integrally attaching an inlet pipe <NUM> and an outlet pipe <NUM> to a lid body portion 45A, and is liquid-tightly attached to a vertical mounting surface 3b formed on the right side of the top wall 3a using two mounting holes 45a and 45a of the lid body portion 45A long in the front-rear direction. A gasket (not illustrated) may be provided between the mounting surface 3b and the lid body <NUM> as necessary.

The inlet pipe <NUM> is liquid-tightly and penetratingly supported by the rear portion of the lid body portion 45A, and a tip portion 47a thereof is provided in a state of having a large insertion amount so as to reach a hole bottom 44a portion of the deep hole portion 44A. The outlet pipe <NUM> is an outlet for a fluid with respect to the deep hole, and is liquid-tightly and internally fitted in an outlet protrusion 45B formed in the front portion of the lid body portion 45A. On the inner surface of the lid body portion 45A, a discharge introduction recess <NUM> located in the outlet protrusion 45B and a flat recess <NUM> that is long in the front-rear direction and extremely shallow are continuously formed. When the lid body <NUM> is assembled to the head cover <NUM>, the discharge introduction recess <NUM> and the flat recess <NUM> are configured such that they face the opening portion 44C with substantially the same dimensions.

In the temperature raising mechanism C, the cooling water r enters the hole bottom 44a portion of the deep hole portion 44A from the inlet pipe <NUM>, and then flows to the deep hole portion 44A, the shallow hole portion 44B, the discharge introduction recess <NUM>, and the outlet pipe <NUM>. When the cooling water r flows through the flow path <NUM>, the heat of the cooling water r is conducted to a valve structure portion <NUM> and a surrounding portion <NUM> of the PCV valve B on the head cover <NUM>, so that the temperature of the PCV valve B can be quickly and efficiently raised. A supply pipe <NUM> for the cooling water r is connected to the inlet pipe <NUM>, and a discharge pipe <NUM> is connected to the outlet pipe <NUM> [see <FIG>].

With the temperature raising mechanism C, the temperature of the cooling water r is quickly raised with the start of the engine, and the PCV valve B is warmed from the inside by the cooling water r that has become a warm fluid, even if the PCV valve B whose lid body <NUM> is exposed to the outside freezes in extremely cold weather such as winter. Therefore, the moisture in the blow-by gas is prevented from freezing in the PCV valve B, and the blow-by gas recirculation device A in which the PCV valve B works well can be realized. In addition, the flow path <NUM> is formed in the head cover <NUM> itself, so that it is not necessary to provide another dedicated flow path and the temperature raising mechanism C that is economical and space-saving can be realized, and the temperature of the PCV valve B can be quickly and efficiently raised from the valve structure portion <NUM> that is the central portion thereof.

As illustrated in <FIG>, <FIG>, a base portion <NUM> for an air bleeding portion (air bleeding) D to act on the blow-by gas passage w is formed in the lid body <NUM>. The air bleeding portion D includes the base portion <NUM> and a bleeding operation tool <NUM> attached to the base portion. The base portion <NUM> is formed in the outlet protrusion 45B in a state of having a vertical hole 56a communicating with the discharge introduction recess <NUM>. The bleeding operation tool <NUM> illustrated in <FIG> [not illustrated in <FIG>] is configured by, for example, a screw plug or a union bolt, but is not limited thereto.

Since the PCV valve B and the lid body <NUM> are located at the highest position in the blow-by gas passage w, there is a merit that air bleeding for the blow-by gas passage w can be performed by one air bleeding portion D provided in the lid body <NUM>. Moreover, the lid body <NUM> has a reasonable structure that serves as both a constituent member of the temperature raising mechanism C and a main part (base portion <NUM>) of the air bleeding portion D, which is advantageous in terms of cost reduction, size reduction, simplification of configuration, and the like.

As illustrated in <FIG>, a heating mechanism <NUM> capable of heating a recirculation passage portion k in which the blow-by gas passage w is communicatively connected to the intake passage a is mounted. The recirculation passage portion k is configured as a portion where the inrush pipe <NUM>, which is the terminal portion of the blow-by gas passage w, and the straight pipe <NUM> (intake passage a) are obliquely and communicatively connected.

The heating mechanism <NUM> is formed by attaching a pipeline <NUM> through which the cooling water r passes to the recirculation passage portion k, and a cooling water inlet portion (not illustrated) made of a metal pipe is liquid-tightly provided below the pipeline <NUM> made of a metal pipe, and a cooling water outlet portion <NUM> made of a metal pipe is liquid-tightly provided above the pipeline <NUM>. The pipeline <NUM> is attached in a state of straddling and being in contact with both the straight pipe <NUM> and the inrush pipe <NUM> by welding (welding or the like).

A first connection tube <NUM> that connects a branched pipe (reference sign is omitted) from an EGR cooler cooling water pipe <NUM> and a cooling water inlet portion (not illustrated) and a second connection tube <NUM> that connects a water pump <NUM> and the cooling water outlet portion <NUM> are provided. For example, the cooling water r enters the pipeline <NUM> from the cooling water inlet portion on the lower side (not illustrated), is thermally conducted to the recirculation passage portion k when passing through the pipeline <NUM>, and then exits from the cooling water outlet portion <NUM> on the upper side.

It is possible to obtain an advantage that troubles, in which in extremely cold weather the moisture in the blow-by gas recirculated into the inrush pipe <NUM> and the straight pipe <NUM> freezes by being cooled by low-temperature fresh air and the internal passage of the inrush pipe <NUM> is narrowed or clogged by the freezing, does not occur. The straight pipe <NUM>, the inrush pipe <NUM>, and the pipeline <NUM> are metal pipes, and the recirculation passage portion k is excellent in thermal conductivity, so that blow-by gas g and cold fresh air can be warmed by the heat of the cooling water r.

The oil filter <NUM> to be installed in the oil separator <NUM> may have a structure other than the impactor structure.

Claim 1:
A blow-by gas recirculation device configured to guide blow-by gas from a crankcase (1B) to an intake passage through an in-cover gas passage (3A) formed inside a head cover (<NUM>), wherein
an oil separator (<NUM>) that traps and removes oil from the blow-by gas is attached to an inside of the head cover (<NUM>),
a pressure regulating valve (B) is provided on an outlet side of the in-cover gas passage (3A) in the head cover (<NUM>), and
a separator outlet (<NUM>), which is an outlet for the blow-by gas in the oil separator (<NUM>), is overlapped on a blow-by gas inlet portion of the pressure regulating valve (B),
wherein the oil separator (<NUM>) includes a separator inlet (<NUM>) through which the blow-by gas is introduced, an oil filter (<NUM>), an oil dropping portion (<NUM>), and the separator outlet (<NUM>) through which the blow-by gas is discharged,
the oil separator (<NUM>) includes a separator rear portion (25A) having the separator inlet (<NUM>), a separator middle portion (25B), the oil filter (<NUM>) located at a boundary between the separator rear portion (25A) and the separator middle portion (25B), a separator front portion (25C) having the separator outlet (<NUM>), and a partition wall (25d), when a longitudinal direction of the head cover (<NUM>) is defined as a front-rear direction, with one of the front-rear direction being front and another one being rear, characterized in that:
the separator front portion (25C) is provided with the separator outlet (<NUM>) in an upper portion and a downward protrusion which serves as the oil dropping portion (<NUM>) in a lower portion, the partition wall (25d) extends in the front-rear direction in both the separator front portion (25C) and the separator middle portion (25B) and is positioned between the separator outlet (<NUM>) and the oil dropping portion (<NUM>), the partition wall (25d) is provided with a droplet collecting portion (<NUM>) and a bottom of the droplet collecting portion (<NUM>) is provided with a through hole (37a) in the separator middle portion (25B), and oil collected in the droplet collecting portion (<NUM>) returns into the engine via the through hole (37a) and the oil dropping portion (<NUM>).