阅读说明：本技术 用于向内燃机供给燃料的泵单元 (Pump unit for supplying fuel to an internal combustion engine ) 是由 M·A·扬努齐 J·克努斯特 于 2018-06-11 设计创作，主要内容包括：一种用于向内燃机供给燃料、特别是柴油燃料的泵单元；所述泵单元包括：头部(2),在头部(2)内沿轴线(A)形成用于容纳滑动泵送活塞(4)的缸；进入阀(8),其位于进入室(9)和压缩室(10)之间的进入孔内,进入室和压缩室分别相应地处于进入孔的上游和下游；塞(11),其在进入阀的区域中压靠头部(2),用于封闭进入室；内部排出通道(15),其形成在头部中并且在一端处连通到收集室(14),用于收集沿着缸渗出的燃料,并且在另一端处连通到形成在塞(11)中的外部排出通道(16)。(A pump unit for supplying fuel, in particular diesel fuel, to an internal combustion engine; the pump unit includes: a head (2) in which a cylinder is formed along an axis (A) for housing a sliding pumping piston (4); an inlet valve (8) located in the inlet bore between an inlet chamber (9) and a compression chamber (10), the inlet and compression chambers being respectively upstream and downstream of the inlet bore; a plug (11) which is pressed against the head (2) in the region of the inlet valve for closing the inlet chamber; an internal drain channel (15) formed in the head and communicating at one end to a collection chamber (14) for collecting fuel seeping along the cylinder and at the other end to an external drain channel (16) formed in the plug (11).)

1. A pump unit for supplying a fuel, in particular diesel fuel, to an internal combustion engine, the pump unit (1) comprising:

-a head (2) in which a cylinder (3) for housing a sliding pumping piston (4) is formed along an axis (a);

-an inlet valve (8) located in the inlet orifice (7) between the inlet chamber (9) and the compression chamber (10), the inlet chamber (9) and the compression chamber (10) being respectively upstream and downstream of the inlet orifice (7);

-a plug (11) which is pressed against the head (2) in the region of the inlet valve (8) for closing the inlet chamber (9);

-an internal drain channel (15) formed in the head (2) and communicating at one end to a collection chamber (14) for collecting the fuel seeping along the cylinder (3) and at the other end to an external drain channel (16) formed in the plug (11).

2. Pump unit according to claim 1, wherein the external discharge channel (16) is configured to discharge the fuel upstream of the inlet chamber (9) outside the pump unit (1) or inside the pump unit (1).

3. Pump unit according to any one of the preceding claims, wherein said external discharge channel (16) comprises an upstream section (16'), said upstream section (16') extending inside a sleeve portion that protrudes from the plug (11) towards the inside of the pump unit (1) and being embedded in a drop seat (21) of the head (2).

4. Pump unit according to claim 3, wherein the sleeve portion projecting from the plug (11) towards the inside of the pump unit (1) extends parallel to the axis (A) in alignment with the compression chamber (10).

5. Pump unit according to any one of the preceding claims, wherein said external discharge channel (16) comprises a downstream section (16 "), said downstream section (16") extending inside a sleeve portion projecting from the plug (11) towards the outside of the pump unit (1).

6. Pump unit according to claim 5, wherein the downstream section (16 ") has a cross section greater than that of the respective upstream section (16').

7. Pump unit according to any one of the preceding claims, wherein the collection chamber is annular and arranged substantially at the inner end of the cylinder (3).

8. Pump unit according to any of the preceding claims, wherein the pump unit (1) comprises a seal (13) in the region of a collection chamber (14).

Technical Field

The invention relates to a pump unit for supplying fuel, preferably diesel fuel, to an internal combustion engine.

Background

As is known, a pump unit for feeding an internal combustion engine with fuel, preferably diesel fuel, comprises a head in which at least one cylinder is formed for housing an associated sliding pumping piston. One end of the pumping piston, in particular the inner end with respect to the pump unit, is connected to an actuator, typically a camshaft, which actuates the movement of the piston. Suitable springs are provided for keeping the shafts pressed against the respective actuators. As the piston reciprocates along the cylinder, it performs an intake stroke during which fuel is drawn into the cylinder, and a compression stroke during which fuel trapped in the cylinder is compressed. The portion of the cylinder that performs compression is referred to as a compression chamber. Typically, fuel is fed into the cylinder through the inlet holes while the discharge of compressed fuel is carried out along the transverse or delivery holes. The outer portion of the head for receiving the fuel that has to be delivered to the cylinder is called the inlet chamber, which is closed externally by a suitable plug or closure that is sealingly fixed on the head. Along the inlet or delivery openings there are suitable valves for regulating the correct fuel flow. Outside the head, the delivery valve is preferably connected to the engine by means of a common manifold provided with a plurality of injectors.

An inlet chamber connected to the cylinder by means of an inlet valve communicates with an inlet channel for sucking fuel from a fuel tank by means of a low-pressure pump, typically a gear pump. The pump unit further comprises a filtering system, for example an annular filter at the inlet of the inlet chamber, for protecting the components of the high-pressure pump from impurities present in the fuel fed by the low-pressure pump.

The lubrication of the piston sliding inside the cylinder is ensured by the fuel itself seeping between the piston and the cylinder from the compression chamber to the bottom of the cylinder where the piston interacts with the camshaft. Since the camshaft is lubricated by an oil bath, the cylinder bottom must be provided with a seal capable of preventing contact between the oil below and the seeping fuel accumulated at the cylinder bottom.

In addition, this seeping fuel that accumulates at the bottom of the cylinder must be periodically removed from the cylinder because its high temperature can damage the seals that are precisely located at the bottom of the cylinder.

According to the prior art, the seepage fuel accumulated at the bottom of the cylinder is again supplied to the intake chamber. For this purpose, a special channel is formed in the head and connects the inlet chamber to a fuel collection chamber at the bottom of the cylinder.

The known solution of the above kind has a number of limitations, in particular at least two disadvantages. A first drawback is that the temperature of the fuel entering the chamber increases due to mixing with the hot fuel coming from the collection chamber at the bottom of the cylinder. This increase in temperature into the chamber reduces the efficiency and reliability of the head and cylinder bottom seals. A second drawback consists in that the pressure peaks present in the intake chamber propagate to the fuel collection chamber at the bottom of the cylinder, with the direct effect of reducing the recirculation efficiency of the fuel. As an indirect effect of this drawback, an increase in the temperature of the cylinder bottom is caused, with the result that the seals and the head may be damaged.

Based on this prior art, the object of the present invention is to provide an innovative pump unit which overcomes the above-mentioned problems.

Disclosure of Invention

According to the invention, a pump unit for supplying fuel, in particular diesel fuel, to an internal combustion engine is provided. The pump unit includes:

-a head inside which a cylinder for housing a sliding pumping piston is formed along an axis a;

-an inlet valve located in the inlet bore between the inlet chamber and the compression chamber, the inlet chamber and the compression chamber being respectively upstream and downstream of the inlet bore;

a plug which presses against the head in the region of the inlet valve for closing the inlet chamber;

an internal drain channel formed in the head and communicating at one end to a collection chamber for collecting the fuel seeping along the cylinder and at the other end to an external drain channel formed in the plug.

Advantageously, in this way, the hot fuel accumulated in the collection chamber is not discharged into the inlet chamber, thereby avoiding overheating of the inlet chamber and the transfer of pressure peaks from the inlet chamber to the collection chamber. According to an embodiment of the invention, the external drain channel is configured to drain fuel outside the pump unit or inside the pump unit upstream of the inlet chamber.

Drawings

Further features and advantages of the invention will become apparent from the following description of non-limiting examples of embodiments with reference to the accompanying drawings, in which:

figure 1 is a schematic cross-sectional view of a portion of a pump unit for feeding fuel to an internal combustion engine according to the present invention;

figure 2 is a schematic cross-sectional view of a plug for closing the access chamber of the pump unit shown in figure 1;

figure 3 is a schematic cross-sectional view of the head of the pump unit shown in figure 1.

Detailed Description

With reference to the description of the figures indicated above, fig. 1 shows a schematic cross-sectional view of an example of embodiment of a pump unit for feeding fuel to an internal combustion engine according to the invention. According to this example, the pump unit 1 comprises a head 2, inside which head 2 a cylinder 3 is formed having an axis a for housing a sliding pumping piston 4. An inlet channel 5 (only partially visible) for feeding fuel from a tank external to the pump to the cylinders 3 and a delivery channel (not shown) for discharging compressed fuel from the cylinders 3 are also formed in the head 2.

An actuating means (not shown), such as a camshaft, is provided at the inner end or bottom of the piston 4 for actuating the reciprocating movement of the piston 4 within the cylinder 3. For this purpose, the piston is pressed against the camshaft by means of a spring 6. The camshaft is lubricated by an oil bath. At the other end or head of the piston 4, the cylinder 3 is provided with an axial hole 7 along the axis a for housing an intake valve 8, the intake valve 8 communicating a compression chamber 10 of the cylinder 3 to an intake chamber 9 located outside the head 2, the intake chamber 9 being supplied with fuel via an intake channel 5. The inlet valve 8 is in this case a stem-like closure member, which projects with one side into the compression chamber 10 and with the other side into the inlet chamber 9. Outside the head 2, the access chamber 9 is closed by a plug 11 against the head 2 by a ring nut 12. The sealing connection of the plug 11 with respect to the head 2 and the connection between the ring nut 12 and the plug 11 are known.

At the inner end of the cylinder 3, the pump unit 1 comprises a seal 13. The purpose of this seal 13 is to prevent fuel that has leaked between the cylinder 3 and the piston 4 from flowing downwards and thus to define a collection chamber 14 in the head 2 for collecting the leaked fuel. Preferably, the collection chamber 14 has an annular shape with respect to the axis a.

As can be seen in fig. 1, an internal discharge channel 15 is formed inside the head 2 and extends from the collection chamber 14 to the intake chamber 9. However, the fuel supplied from the collection chamber 14 to the inner discharge passage 15 is discharged not to the inlet chamber 9 but to the outer discharge passage 16 formed in the plug 11. The external outlet channel 16 thus extends from the outer surface of the plug 11 in contact with the head 2 towards the outside of the plug 11 into the inlet chamber 9.

Fig. 2 shows a cross-sectional view of the plug 11 of fig. 1. It can be seen that the outer discharge channel 16 comprises two sections, an upstream section 16' and a downstream section 16 ", which have different cross-sections. The cross-section of the upstream section 16' is smaller than the cross-section of the corresponding downstream section 16 ". The terms "upstream" and "downstream" relate to the flow of fuel through the channels and are schematically illustrated by the arrows in fig. 1. According to the example shown in fig. 2, the downstream section 16 "of the external discharge channel 16 extends into an associated sleeve portion, which extends parallel to the axis a outside the plug 11, i.e. from its outer surface 19. The upstream section 16' of the external discharge channel 16 extends inside the plug 11 and continues into the associated sleeve portion, which extends inside the head 2 beyond the usual contact surface of the plug 11 with the head 2. This contact surface is schematically indicated in fig. 2 by reference numeral 20. In other words, the contact point between the inner channel 15 and the outer channel 16 is located along the axis a at a height level closer to the inside of the pump than the inlet of the hole 8 for feeding fuel into the inlet chamber. According to the example shown, the contact point between the inner channel 15 and the outer channel 16 is aligned along the axis a at the same height level or perpendicular to the axis a as the compression chamber 10 or as the inner surface of the cylinder 3 of the stem inlet valve 8.

Fig. 3 shows a sectional view of the head 2 shown in fig. 1. It can be seen that in the region of the access chamber 9, the head comprises a drop seat 21 parallel to the axis a, and this drop seat 21 is configured for receiving a corresponding projecting portion of the external discharge channel 16. In particular, the side wall of the drop seat 21 is in lateral contact with a sleeve portion projecting from the plug 11, which defines the projecting portion of the external discharge channel 16.

It will be apparent that the invention described herein may be modified and varied without departing from the scope of the appended claims.