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Title:
HIGH PRESSURE PUMP FOR FEEDING FUEL TO AN INTERNAL COMBUSTION ENGINE AND METHOD FOR CONTROLLING THE PUMP
Document Type and Number:
WIPO Patent Application WO/2018/073298
Kind Code:
A1
Abstract:
A high pressure pump for feeding fuel, preferably diesel fuel, to an internal combustion engine; the pump (1) comprising: a cylinder (4); a pumping piston (5) coupled to the cylinder (4) and comprising a head (18) and an opposite base portion; a sealing element (22) coupled to the base portion of the cylinder (4) for avoiding the exit of fuel from the cylinder (4); an intake valve (7) in communication with the cylinder (4); a space (23) arranged between the cylinder (4) and the sealing element (22); a feed line (6) that is configured for feeding low pressure fuel to the intake valve (7); a first duct (25) outside the cylinder (4) connected to one side to the space (23) and to the other side to the feed line (6); and a second duct (26) outside the cylinder (4) connected to one side to the feed line (6) and to the other side to the cylinder (4) between the sealing element (22) and the head of the cylinder (4).

Inventors:
FORTE, Angelo (Via Garigliano 24, Altamura, 70022, IT)
RONCONE, Massimiliano (Via Madre Teresa di Calcutta 21, Bitritto, 70020, IT)
TAVANI, Manuel (Thomas-Mann-Str. 21, Stuttgart, 70469, DE)
Application Number:
EP2017/076594
Publication Date:
April 26, 2018
Filing Date:
October 18, 2017
Export Citation:
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Assignee:
ROBERT BOSCH GMBH (Postfach 30 02 20, Stuttgart, 70442, DE)
International Classes:
F02M59/06; F02M53/00; F02M55/00; F02M59/10; F02M59/44; F02M63/00; F04B1/04
Domestic Patent References:
WO2015055332A12015-04-23
WO2015090676A12015-06-25
Foreign References:
EP1323919A22003-07-02
EP2620633A12013-07-31
EP1277951A22003-01-22
DE102014218992A12016-03-24
Other References:
None
Download PDF:
Claims:
CLAIMS

1. A high pressure pump for feeding fuel, preferably diesel fuel, to an internal combustion engine; the pump (1) comprising:

a cylinder (4);

a pumping piston (5) coupled to the cylinder (4) and comprising a head (18) and an opposite base portion;

a sealing element (22) coupled to the base portion of the cylinder (4) for avoiding the exit of fuel from the cylinder (4);

an intake valve (7) in communication with the cylinder (4);

a space (23) arranged between the cylinder (4) and the sealing element (22); a feed line (6) that is configured for feeding low pressure fuel to the intake valve (7);

a first duct (25) outside the cylinder (4) connected to one side to the space (23) and to the other side to the feed line (6); and

a second duct (26) outside the cylinder (4) connected to one side to the feed line (6) and to the other side to the cylinder (4) between the sealing element (22) and the head of the cylinder (4).

2. Pump as claimed in claim 1, wherein the cylinder comprises a groove (27) at the connecting point to the second duct (26).

3. Pump as claimed in claim 2, wherein the groove (27) is realized at the middle of the length of the cylinder (4). 4. Pump as claimed in claim 2, wherein the groove (27) is realized in the half of the cylinder (4) near to the sealing element (22) or near to the head of the cylinder (4).

5. Pump as claimed in any one of the foregoing claims, wherein the pump (1) comprises a pump body (2) and a head (3) assembled to the pump body (2); and wherein the cylinder (4), the first duct (25), and the second duct (26) are realized into the head (3). Method for controlling a high pressure pump for feeding fuel, preferably diesel fuel, to an internal combustion engine; the method comprising the steps of: a) providing a pump (1) comprising:

a cylinder (4);

a pumping piston (5) coupled to the cylinder (4) and comprising a head (18) and an opposite base portion;

a sealing element (22) coupled to the base portion of the cylinder (4) for avoiding the exit of fuel from the cylinder (4);

an intake valve (7) in communication with the cylinder (4);

a space (23) arranged between the cylinder (4) and the sealing element (22); a feed line (6) that is configured for feeding low pressure fuel to the intake valve (7);

a first duct (25) outside the cylinder (4) connected to one side to the space (23) and to the other side to the feed line (6); and

a second duct (26) outside the cylinder (4) connected to one side to the feed line (6) and to the other side to the cylinder (4) between the sealing element (22) and the head of the cylinder (4);

b) feeding fuel from the feed line (6) to the space (23) arranged at the base of the cylinder (4) through the first duct (25);

c) feeding fuel from an intermediate portion of the cylinder (4) between the head and the sealing element (22) to the feed line (6) through the second duct (26).

Method as claimed in claim 6, wherein the step c) of feeding fuel from an intermediate portion of the cylinder (4) between the head and the sealing element (22) to the feed line (6) through the second duct (26) is performed with closed intake valve (7) during the compression phase of the piston (5).

Method as claimed in claim 6 or 7, wherein the step b) of feeding fuel from the feed line (6) to the space (23) arranged at the base of the cylinder (4) through the first duct (25) is performed with closed intake valve (7) during the compression phase of the piston (5) and with opened closed intake valve (7) during the suction phase of the piston (5).

9. Method as claimed in claim 8, wherein during the suction phase of the piston (5) the first duct (25) is fed only by fuel fed by a low pressure pump (28) in the feed line (6). 10. Method as claimed in claim 8, wherein during the compression phase of the piston (5) the first duct (25) is fed by fuel that is a mixture of the fuel fed by low pressure pump (28) in the feed line (6) and the fuel that enters the feed line (6) from the second duct (26).

Description:
DESCRIPTION

Title

HIGH PRESSU RE PUMP FOR FEEDING FU EL TO AN INTERNAL COMBUSTION ENGINE AND METHOD FOR CONTROLLING THE PUMP

The present invention relates to a high pressure pump for feeding fuel to an internal combustion engine, and to a method for controlling such a pump.

Generally, high pressure pumps have a pumping piston and comprise a pump body; a head assembled to the pump body; a cylinder made in the head; a pumping piston engaged slidingly in the cylinder; an intake valve for selectively controlling the supply of fuel to the cylinder; and an outlet valve for sending the high pressure fuel compressed by the piston to the internal combustion engine. High pressure pumps further comprise a sealing element arranged at the base of the cylinder around the pumping piston. The purpose of the sealing element is to prevent the possibility of fuel drawn between the cylinder and the piston exiting the cylinder and entering the lubricating oil chamber that houses moving parts of the pump. Note that it is desirable for the fuel to be drawn along the cylinder as described above, in order to lubricate the components of the pump.

One drawback of the prior art is that the high pressure pump reaches a very high temperature at the base of the cylinder also due to the fuel drawn along the cylinder and deposited in a special space made at the seal. The aim of the present invention is to produce a high pressure pump for feeding fuel, preferably diesel fuel, to an internal combustion engine which prevents excessive overheating at the base of the cylinder.

According to the present invention, a high pressure pump for feeding fuel, preferably diesel fuel, to an internal combustion engine is thus produced; the pump comprising: a cylinder;

a pumping piston coupled to the cylinder and comprising a head and an opposite base portion;

a sealing element coupled to the base portion of the cylinder for avoiding the exit of fuel from the cylinder;

an intake valve in communication with the cylinder;

a space arranged between the cylinder and the sealing element; a feed line that is configured for feeding low pressure fuel to the intake valve;

- a first duct outside the cylinder connected to one side to the space and to the other side to the feed line; and

a second duct outside the cylinder connected to one side to the feed line and to the other side to the cylinder between the sealing element and the head of the cylinder.

The method according to the invention for controlling such a pump comprises the steps of:

feeding fuel from the feed line to the space arranged at the base of the cylinder through the first duct;

feeding fuel from an intermediate portion of the cylinder between the head and the sealing element to the feed line through the second duct.

In this way, the space made at the foot of the piston and at the seal is fed with low pressure fuel at a low temperature taken from the feed line fed by the pre-feeding pump, while the drawn fuel, which, when compressed, reaches a high pressure and a high temperature, is evacuated into the second duct and thus cyclically away from the cylinder. This therefore prevents a high temperature being reached at the base of the piston at the seal.

In particular, the step of feeding fuel from an intermediate portion of the cylinder between the head and the sealing element to the feed line through the second duct is performed with closed intake valve during the compression phase of the piston. The step of feeding fuel from the feed line to the space arranged at the base of the cylinder through the first duct is performed with closed intake valve during the compression phase of the piston and with opened intake valve during the suction phase of the piston. This ensures a frequent cycle of renewal of the fuel collected in the space in both the compression phase and the suction phase. Moreover, during the compression phase, the fuel collected in the space is expelled, along with the drawn fuel, by the second duct.

In particular, during the suction phase of the piston, the first duct is fed only with fuel fed by the pre-feeding pump in the feed line. In this phase, the fuel does not enter the second duct because the low pressure in the suction chamber summons the fuel into the compression chamber.

Thus, during the suction phase, the space is fed with low pressure fuel at a low temperature.

In particular, during the compression phase of the piston the first duct is fed by fuel that is a mixture of the fuel fed by low pressure pump in the feed line and the fuel that enters the feed line from the second duct.

In this way, because the fuel that enters the feed line from the second duct is, in terms of volume ratio, much less than the fuel fed by the pre-feeding pump in the feed line, even in the compression phase the space is fed with fuel at a low temperature, i.e. lower than the temperature of the fuel flowing in the second duct. During the compression phase, the pressure inside the groove into which the second duct emerges is generally higher than the pressure in the seat that defines the suction chamber.

In particular, the cylinder comprises a groove at the connecting point to the second duct.

Thus, the fuel which is drawn and runs along the cylinder is collected in the groove and does not continue on to the seal, except for a small amount, thus preventing increases in temperature in said area fed only with fuel diverted from the feed line.

Preferably, the groove is realized at the middle of the height of the cylinder more or less equidistant between the sealing element placed at the base of the cylinder and the compression chamber. This ensures a balance between efficiency and having a low temperature at the base of the cylinder.

Alternatively, the groove is realized in the half of the cylinder near to the sealing element placed at the base of the cylinder, i.e. in the distal half of the cylinder with respect to the compression chamber.

This improves the efficiency of the pump. To be specific, the drawn fuel lubricates the cylinder properly over almost the whole length thereof and in the compression phase even the fuel contained in the space is easily sucked out and fed into the second duct, leaving the space free for new low temperature fuel diverted from the feed line.

Alternatively, the groove is realized in the half of the cylinder near to the compression chamber, i.e. in the distal half of the cylinder with respect to the sealing element placed at the base of the cylinder.

In particular, the pump comprises a pump body and a head assembled to the pump body; wherein the first duct and the second duct are made well within the head.

In this way, the first and second ducts are protected from other sources of heat.

The present invention shall now be described with reference to the attached drawings, which illustrate non-limiting embodiments of the invention, in which:

figure 1 is a view in section, with parts cut away for clarity, of an embodiment of a high pressure pump according to the present invention.

With reference to the figure, reference sign 1 indicates, as a whole, a high pressure pump for feeding fuel, preferably diesel fuel, to an internal combustion engine (not shown) from a pre-feeding pump or low pressure pump 28. The pre- feeding pump 28 and the high pressure pump 1 define a system 29 for feeding the fuel to the internal combustion engine. The pump 1 comprises a pump body 2; a head 3 which extends along an axis Al and is assembled to the pump body 2; a cylinder 4 which extends along the axis Al; at least one pumping piston 5 which extends along the axis Al and is coupled to the cylinder 4 in such a way as to slide back and forth along the cylinder 4; a feed line 6 that is configured for feeding fuel to the high pressure pump 1 from the pre-feeding pump 28; an intake valve 7 for regulating the passage of the fuel to the piston 5; and an outlet valve (not shown in the attached figures) for discharging fuel pumped by the piston 5.

The head 3 has a compression chamber 8 made at one end of the cylinder 4; and a seat 9 in the form of a funnel that extends along the axis Al and is in communication with the compression chamber 8. The seat 9 defines, along with the other components of the pump 1, a suction chamber which, for the purposes of the invention, forms part of the feed line 6. The intake valve 7 is housed in the seat 9 and is clamped against an internal surface 11 of the head 3 by means of a connector 12. The intake valve 7 comprises a valve body 13, a shut-off member 14, an elastic member 15 and a disc 16. The valve body 13 is in abutment against the head 3, in particular against the internal surface 11. The shut-off member 14 is housed inside the valve body 13 and is coupled to the disc 16. The elastic member 15 is arranged between the disc 16 and the valve body 13. The intake valve 7 comprises an intake duct 17 made inside the valve body 13 which receives fuel from outside the intake valve 7 and feeds it to the compression chamber 8. The shut-off member 14 is configured to allow or block the passage of the fuel into the combustion chamber 8 through the intake duct 17. The piston 5 comprises, at one end, a head 18 at the compression chamber 8; and a foot 19 at the opposite end. The pump 1 comprises a cam 20 that rotates about an axis A2, which is transverse with respect to the axis Al, and a shoe 21 connected to the foot 19 of the piston 5 and in contact with the cam 20. When the cam 20 rotates, it pushes the piston 5 back and forth along the axis Al.

The pump 1 comprises a sealing element 22 arranged between the piston 5 and the cylinder 4 to prevent fuel from exiting from the cylinder 4 and running along the piston 5. In particular, the sealing element 22 is associated with the base of the cylinder 4 not far from the foot 19, base in this case meaning in general a portion of the cylinder opposite the head but not necessarily at the end thereof. The high pressure pump 1 comprises an elastic member 24 interposed between the sealing element 22 and the shoe 21 of the piston 5.

The pump 1 comprises a space 23 for receiving fuel, made between the cylinder 4, seal 22 and head 3, and a first duct 25 for feeding fuel from the feed line 6, in particular downstream of the pre-feeding pump 28, to the space 23.

The pump 1 further comprises a second duct 26 for feeding fuel from an intermediate portion of the cylinder 4, in particular in correspondence with a groove 27 in the cylinder 4, to the feed line 6, in particular to the seat 9.

Both ducts 25 and 26 are made inside the head 3 and outside the cylinder 4.

In use, during the suction phase of the piston 5, the fuel enters the pump 1, fed by the pre-feeding pump 28, through the feed line 6. In particular, during said suction phase the valve 7 is open and the fuel arrives in the seat 9, enters the intake duct 17 of the intake valve 7 before passing by the shut-off member 14 and reaching the compression chamber 8. During said suction phase, some of the fuel coming along the feed line 6 is diverted into the duct 25 and thus reaches the space 23.

During the compression phase, on the other hand, the piston 5 is moved in the other direction along the axis Al towards the intake valve 7, thereby increasing the pressure of the fuel in the compression chamber 8. The fuel is then discharged, via the outlet valve (not shown) out of the pump 1.

During the compression phase, the fuel drawn along the cylinder 4 as far as the groove 27 is pushed into the second duct 26 and flows into the feed line 6 fed with low pressure fuel by the pre-feeding pump 28.

Therefore, the hot fuel at high pressure flowing in the second duct 26 is mixed with the low pressure fuel in the feed line 6, thus feeding the first duct 25 with fuel at a medium temperature with respect to the fuel fed by the pre-feeding pump 28 and the fuel flowing in the second duct 26. Since the volume ratio between these two converging lines is sharply in favour of the feed line 6, the fuel flowing in the second duct 26 being only the drawn fuel collected in the groove 27 and that contained in the space 23, the temperature of the fuel which, when the valve 7 is closed, flows into the first duct 25 and reaches the space 23, is only slightly higher than the temperature of the fuel fed by the pre-feeding pump 28 and well below the temperature of the fuel flowing in the second duct 26.

Consequently, according to the invention, the space 23 is fed with fuel diverted from the feed line 6 which comes from the pre-feeding pump 28 both during the suction phase and during the compression phase.

In particular, during the suction phase the space 23 is fed only with low pressure fuel leaving the pre-feeding pump 28, while during the compression phase it is fed with fuel which is still at low temperature with respect to the high pressure fuel, as a result of mixing the low pressure fuel leaving the pre-feeding pump 28 with the fuel leaving the second duct 26.

Moreover, it is clear that the present invention also covers embodiments not described in the detailed description and equivalent embodiments that fall within the scope of protection of the attached claims.