|Title of Invention||
"FUEL ADJUSTMENT AND FILTERING DEVICE FOR A HIGH-PRESSURE PUMP"
|Abstract||ABSTRACT The device comprises at least one cartridge (38) carrying a filtering body (37) and removably housed in a corresponding casing (41). The device further comprises a shut-off solenoid valve (27) for metering the fuel and a pressure control valve (32) of such fuel. The solenoid valve (27) and possibly also the control valve (32) are housed in a block (54) separate from the pump (7) and either fixed to or integrated with the casing (41) of the cartridge (38) . The casing (41) is provided with a lid (46) , on which a union (52) for the connection to a supply pipe (10) is fixed. The block (54) comprises two unions (62 and 72) to connect the solenoid valve (27) and the control valve (32) to the pump (7), and a group of internal pipes (63) to connect the solenoid valve (27) upstream of the valve (32) in the direction of flow of the fuel. (figures 4 and 5)|
|Full Text||The present invention relates to a fuel adjustment and filtering device for a high-pressure pump in an injection system for an internal combustion engine.
As it is known, fuel injection systems of the aforesaid type comprises a low-pressure fuel pump to take the fuel from the usual tank and send it to the high-pressure pump. This sends the pressurised fuel to a common rail connected to the various engine cylinder injectors. The system further comprises a fuel filter and devices for controlling the rail fuel pressure.
Injection systems are known in which the high-pressure pump is of the variable flow rate type controlled so as to avoid pumping fuel in excess with respect to that required by the injectors, thus reducing the work performed by the high-pressure pump and therefore increasing the engine efficiency. In a known system, the high-pressure pump flow rate is metered by a shut-off solenoid valve, arranged on the intake pipe of the pump and controlled by a control unit, according to the operative conditions of the engine.
It has also been proposed to insert, in the intake pipe of the high-pressure pump, a control valve adapted to adjust the pressure of the fuel, upstream of the shut-off solenoid valve, to a predetermined value. This valve sends the fuel in excess, received from the low-pressure
pump, to the usual case of the high-pressure pump, from where it is discharged into the fuel tank. In such a way, the fuel in excess lubricates and cools the operating mechanism of such pump before returning to the tank. Furthermore, in order to avoid load losses and hydraulic resonance waves between the two pumps, the shut-off solenoid valve and the pressure control valve of the fuel to intake must be reciprocally arranged as close as possible.
In the high-pressure pumps of the known art, in general the fuel filter is arranged between the low-pressure pump and the high-pressure pump. Furthermore, the shut-off solenoid valve and the pressure control valve are integrated with the high-pressure pump and are accommodated in a common casing, which comprises the high-pressure crankcase, forming the usual pump body in which the various pumping elements are housed. Such an integration however creates a considerable complexity in the hydraulic connection of the adjustment valve and of the shut-off valve. The pump body therefore appears relatively heavy and cumbersome, thus requiring a complicated and costly manufacture.
For motorcar engines, in which the injection system must be assembled within the usual engine housing, it also appears difficult to find space for such high-pressure pump near the usual common rail on the engine head. Finally, as it is known, the shut-off solenoid valve comprises some delicate electrical components, some
plastic electrical connectors, and some other parts more fragile than the pump body, which is generally formed by cast iron. The solenoid valve can be subjected to damage both during assembly on the engine and in the case of motorcar collisions or accidents, endangering its operation. In the case of motorcar accident, a dangerous leakage of fuel may further be generated.
It is the object of the present invention to provide a fuel adjustment and filtering device for a high-pressure pump of an injection system, which is easy to manufacture and to assemble and of low cost, eliminating the drawbacks of the devices of the known art.
According to the invention, this object is reached by a fuel adjustment and filtering device for a high-pressure pump as defined by claim 1 or by claim 2.
For a better understanding of the invention, a preferred embodiment will be described hereinafter by way of example, with the help of the accompanying drawings, in which:
figure 1 is a partial diagram of an injection system incorporating a fuel adjustment and filtering device according to the invention;
figure 2 is a perspective top view of the adjustment and filtering device;
figure 3 is a top view of the device in figure 2;
figure 4 is a section taken along line IV-IV of figure 3;
figure 5 is a section taken along line V-V of figure 3.
With reference to figure 1, numeral 6 generically indicates a fuel injection system for an internal combustion engine, for example a four-stroke diesel cycle engine, which comprises a plurality of injectors connected to the usual pressurised fuel common rail (not shown in figure 2) . The common rail is supplied with high-pressure fuel by a high-pressure pump, generically indicated by numeral 7, by means of a delivery pipe 8. In turn, high-pressure pump 7 is supplied by a low-pressure pump, for example a pump 9, by means of a supply pipe 10 of pump 7. Pump 9 is generally arranged in usual fuel tank 11, to which an exhaust pipe 12 of the fuel in excess in injection system 1 leads.
On supply pipe 10 there is arranged a filter 14 adapted to prevent the introduction in pump 7 of possible impurities present in the fuel pumped by low-pressure pump 9. Each injector is adapted to inject each time in the corresponding cylinder a variable quantity of fuel, under the control of an electronic control unit 16, which may be formed by the usual engine microprocessor control unit. Control unit 16, by processing signals corresponding to the operative conditions of the engine, controls both the injectors and the fuel pressure in the common rail, in an intrinsically known way.
High-pressure pump 7 comprises at least one pumping element 18 formed by a cylinder 19 having an
intake chamber 20, in which slides a piston 21 mobile in reciprocating motion forned by an intake stroke and a delivery stroke. Specifically, in figure 1 pump 7 comprises two pumping elements 18, each of which having a compression chamber 20 provided with a corresponding intake valve 25 and a corresponding delivery valve 30. Valves 25 and 30 may be of the ball type and may be provided with respective recall springs. The two intake valves 25 are in communication with reciprocally common supply pipe 10, as described in better detail below, while the two delivery valves 30 are in communication with delivery pipe 8 in common to the latter.
Pistons 21 are operated by an actuating mechanism 26 housed in a compartment 35 enclosed in a crankcase 33. In figure 1, the two pumping elements 18 are reciprocally coaxial and opposite, and actuating mechanism 26 comprises a single cam 22 carried by a shaft 23, in consequence of which pistons 21 are actuated with a reciprocal offset of 180°. Shaft 23 may be actuated in any known way, for example by the usual engine crankshaft, by means of a motion transmission device. The flow rate of high-pressure pump 7 is exclusively controlled by a metering, or shut-off, solenoid valve 27, of the on-off type, which is provided with an inlet 29 in communication with supply pipe 10, and an outlet 28 in communication with intake valves 25, through corresponding intake pipes 31. Solenoid valve 27 is adapted to be actuated, in synchronous or asynchronous
manner with respect to the movement of pumping elements 18, both during the intake stroke and during the compression stroke, according to the operative conditions of the engine, by control unit 16, by means of frequency modulated and/or duty cycle control signals. These conditions determine the quantity of fuel that the pump 7 must intake through pipes 31.
On supply pipe 10 is further arranged a pressure control valve 32, which is used to maintain constant the pressure of the fuel to be supplied, continuously pumped by low-pressure pump 9. Specifically, pressure control valve 32 is of the ball and spring type, and is provided with an inlet 34 in communication with supply pipe 10. Valve 32, through an outlet pipe 36, sends the fuel in excess in compartment 35 of crankcase 33 of the pump 7, for the purpose of cooling and lubricating actuating mechanism 2. The fuel in excess having entered compartment 35 returns to tank 11, through outlet pipe 36 in communication with exhaust pipe 12.
Filter 14 comprises a filtering body 37 (figure 4) formed by intrinsically known specific material, for example paper or felt. Filtering body 37 is accommodated in a metallic material cartridge 38 (figures 2 and 3) formed by a side wall 39, having an essentially cylindrical shape, with a lower portion 40 of reduced diameter, whereby the cartridge 38 is open on both ends.
Filter 14 is adapted to be removably housed in an substantially cylindrical casing 41 independent from the
body of pump 7. Casing 41 presents a cylindrical wall 42 having an axis A, which presents a lower portion 43 of reduced diameter, adapted to partially accommodate portion 40 of wall 39 with a large clearance, so as to define a gap 44. Casing 41 is integral with a closed lower wall 45, and is further provided with a flat upper wall or lid 46, removably connected to side wall 42 of casing 41, in a known manner, for example by bayonet or clip fastening, not shown in the drawings, to allow the replacement of cartridge 38.
Filtering body 37 determines in casing 41 a lower chamber 47 contiguous to gap 44, and an upper chamber 48 delimited by lid 46. It is crossed by a pipe 49 parallel to axis A, which on one side leads to lower chamber 47 and on the other is adapted to fluid-tightly engage a coaxial pipe 51, carried by lid 46. Pipe 51 protrudes from a free portion 50 of lid 46, forming an inlet union 52, which is adapted to be connected to supply pipe 10 (also see figure I) . Lid 46 is further crossed by a sleeve 53 parallel to pipe 51, which leads on bottom into upper chamber 48 and protrudes on top from lid 46 itself.
Shut-off solenoid valve 27 (figure 5) is housed in a cylindrical seat 56 of an substantially prismatic-shaped block 54, fixed in known manner onto lid 46, covering another part 60 of lid 46, and leaving union 52 free. Seat 56 presents an axis perpendicular to axis A and only partially houses solenoid valve 27, so as to allow the electrical connection with control unit 16 and
with electrical power. Solenoid valve 27 is removably mounted in block 54, by means of screws 55. Seat 56 forms with the body of solenoid valve 27 an annular chamber 57 in communication with inlet 29 of solenoid valve 27, as will be better seen below. Annular chamber 57 allows the fuel from filtering body 37 to cross the inlet of solenoid valve 27 when this is closed and however ensures a continuous flow rate of fuel towards pressure control valve 32.
Block 54 is further provided with a cylindrical seat 58 (figure 4) parallel to axis A and adapted to house at least partially a cylindrical body 59, in which control valve 32 is enclosed. Body 59 carries inlet 34 of valve 32 and an outlet union 62. Union 62 is parallel to axis A and protrudes from block 54. It is adapted to be connected in known manner to outlet pipe 36, to send the fuel discharged by valve 32 to compartment 35 of crankcase 33.
Block 54 presents a group of internal pipes, indicated as a whole by numeral 63, which are adapted to put into communication the outlet of filter 14, represented by sleeve 53, with inlet 29 of solenoid valve 27 and with inlet 34 of valve 32. Specifically, the series of pipes 63 comprises an axial pipe segment 64 which leads into annular chamber 57 of seat 56, and is in fluid-tight communication with sleeve 53. The inlet of solenoid valve 27 is in communication with annular chamber 57, in an intrinsically known manner.
Annular chamber 57 is further in communication with a radial pipe 66, closed by a cap 67 for technological reasons. Radial pipe 66 is in communication with the inlet union 34 of valve 32, through another axial pipe 68. Therefore, solenoid valve 27 is arranged, with respect to valve 32, upstream in the direction of flow of the fuel. The segment of the group of pipes 63 comprising annular chamber 57 and pipes 66 and 68 comprised between inlet 29 of solenoid valve 27 and inlet 34 of valve 32 is dimensioned so as to ensure, in use, the flow of fuel at inlet 29 of solenoid valve 27 and, when this is closed, allows the disposal of the entire flow rate of pump 9 towards pressure control valve 32.
Finally, outlet 28 (figure 5) of solenoid valve 27 is in communication with an axial pipe 69 of block 54, which leads to a sleeve 71, in which an outlet union 72 parallel to axis A is fluid-tightly inserted. Outlet union 72 is placed in use in communication between intake valves 25 (also see figure 1) of pumping elements 18, through intake pipes 31.
The flow of fuel through the adjustment and filtering device is performed as follows.
The fuel pumped by low-pressure pump 9 (figures 1 and 4), as shown above, entirely reaches inlet union 52 and, through pipe 49 of filtering body 37, reaches lower chamber 47 of casing 41. After crossing filtering body 37, the fuel, through sleeve 53, now enters block 54 and reaches annular chamber 57. Since the quantity of fuel
pumped by low-pressure pump 9 is always greater than that required at inlet 29 of high-pressure pump 7, the fuel in excess tends to make the pressure in inlet pipe 68 to pressure control valve 32 increase thus making it open. The increase of pressure in pipe 68 is balanced by the spring of pressure valve 32, thus a situation of balance is reached when the pressure in pipe 68 reaches the value corresponding to the preload of the spring. Thus, this fuel reaches chamber 35 of case 33, whereby actuating mechanism 26 of pumping elements 18 is continuously lubricated and cooled.
In turn, shut-off solenoid valve 27 is continuously opened and closed under the control of control unit 16,'so as to allow the passage towards pump 7 only of the fuel required by the injectors according to the operative conditions of the engine. However, when solenoid valve 27 is closed not only does the flow of fuel continue in the intersection of inlet 29 with annular chamber 57, but this flow is generally also greater, because in such times all the fuel sent by low-pressure pump 9 is discharged by pressure control valve 32.
When solenoid valve 27 is reopened, there is a certain flow of fuel in the group of pipes 63 and specifically in annular chamber 57, so that the fuel presents a certain kinetic component and readily run-through inlet 29 of solenoid valve 27.
From the above, the advantages of fuel adjustment
and filtering device 1 according to the invention with respect to the known art are apparent. Specifically, the body of pump 7 is very simple to manufacture, since the number of internal hydraulic connections is considerably reduced, because all of connections 63 are now transferred to a casing other than the body of the pump. Furthermore, the pump body appears lighter, because it no longer needs to contain appendixes or protrusions for accommodating shut-off solenoid valve 27 and pressure control valve 32.
In any case, a weight reduction of the injection system is obtained, because supporting block 54 of the components of the adjustment device, being arranged on the low-pressure circuit, may be formed by lighter material and with reduced thickness. In turn, the assembly of pump 7 in the engine housing, which must be very close to the pressurised fuel common rail and therefore also to the engine head, is much simplified also in virtue of the reduced dimensions of high-pressure pump 7 itself.
Furthermore, since pressure control valve 32 and shut-off solenoid valve 37 can be arranged in block 54, they are relatively much closer to each other, thus obtaining an optimal operation from the hydraulic point of view, avoiding between them a pressure drop and reducing the pressure waves caused by the actuation of solenoid valve 27. Finally, block 54, also with casing 41, may be arranged in the engine bay in an optimal
position to reduce the effects of possible motorcar accidents.
It is understood that to the adjustment and filtering device described above various modifications and improvement may be made without departing from the scope of the claims. For example, block 54 may be separate from casing 41 and connected to it by means of a simple pipe. Furthermore, pressure control valve 32 may be omitted and block 54 may contain only solenoid valve 27. Also pressure control valve 32 may be arranged upstream of solenoid valve 27, rather than downstream, as shown in the figures. Finally, in the case of a pump 7 with two pumping elements 18, as in figure 1, or three radial pumping elements, block 54 may be provided, for each pumping element 18, with an inlet 29 of a corresponding solenoid valve 27, in communication with a specific outlet pipe 53 from the filter 14.
1. An adjustment and filtering device for a high-pressure pump (7) in an injection system (1) for an internal combustion engine, comprising a filter (14) formed of a cartridge (38) carrying a filtering body (37) housed in a casing (41), a shut-off solenoid valve (27) supplied with fuel by said filter (14), and a fuel pressure control valve (32) adapted to control the pressure of fluid so supplied, said solenoid valve (27) and said control valve (32) being housed in a block (54) separate from said pumps (7), said casing (41) having an essentially cylindrical shape and being closed by a wall (46) removably mounted on said casing (41) for allowing the replacement of said cartridge (38); characterised in that said block (54) is directly fixed to, or integrated with said wall (46), said solenoid valve (27) being adapted to shut-off the fuel supplied to said pressure pump (7), said block (54) carrying a group of pipes (63) adapted to put in communication an outlet passage (53) of said filter (14) with inlets (29, 34) of said valves (27, 32).
2. A device as claimed in claim 1, wherein said wall (46) is substantially flat and said block (54) is provided with a substantially prismatic shape, and covers only a part (60) of said flat wall (46), an inlet union (52) being provided on another part (50) of said flat wall (46) for connecting a supply pipe (10) of the fuel to said cartridge (38).
3. A device as claimed in claim 2, wherein said block (54) further comprises an axial seat (58) in which said control valve (32) is removably accommodated, and a radial seat (56) in which said solenoid valve (27) is removably accommodated.
4. A device as claimed in claim 3, wherein said block (54) carries an axial outlet union (72) for supplying the fuel out coming from said solenoid valve (27), to said pump (7).
5. A device as claimed in any previous claim, wherein said pump (7) comprises an actuating mechanism (26) enclosed in a crankcase (33), wherein said outlet pipe (36) of said control valve (32) is adapted to be hydraulically connected to said crankcase (33) to lubricate and cool said mechanism (26).
6. A device as claimed in claim 5, wherein said block (54) carries another union (62)
adapted to be hydraulically connected to said outlet pipe (36) of said control valve
7. A device as claimed in claim 6, wherein said outlet unions (62, 72) are parallel to
said inlet union (52).
8. A device as claimed in one of the preceding claims, wherein said group of pipes (63)
comprises at least one control pipe (66) to put the inlet (34) of said control valve
(32) into communication with the inlet (29) of said solenoid valve (27), the inlet (29)
of said solenoid valve (27) being arranged upstream with respect to that of said
control valve (32) in the direction of flow of said fuel.
9. A device as claimed in claim 8, wherein said group of ducts (63) comprises a union
connected to a passage (53) of said wall (46) to receive the filtered fuel.
10. A device as claimed in claim 9, wherein said block (54) is accommodated in the engine housing of a motorcar, wherein said wall (46) is fixed in said engine housing independently from said pump (7).
|Indian Patent Application Number||39/DEL/2007|
|PG Journal Number||09/2014|
|Date of Filing||04-Jan-2007|
|Name of Patentee||C.R.F. SOCIETA CONSORTILE PER AZIONI|
|Applicant Address||50 STRADA TORINO, ORBASSANO 10043, ITALY|
|PCT International Classification Number||F02D41/22|
|PCT International Application Number||N/A|
|PCT International Filing date|