WO2005052357A1

WO2005052357A1 - High pressure feed pump for internal combustion engines

Info

Publication number: WO2005052357A1
Application number: PCT/CH2004/000665
Authority: WO
Inventors: Marco A. Ganser
Original assignee: Ganser-Hydromag Ag
Priority date: 2003-11-28
Filing date: 2004-11-04
Publication date: 2005-06-09
Also published as: DE502004007514D1; EP1687524B1; ATE399936T1; EP1687524A1

Abstract

The invention relates to a high pressure feed pump (10) comprising a number of pump cylinders (12.1, 12.2) that are fixed to a housing and provided with a cylinder body (16) and admission valves (40.1, 40.2) and discharge valves arranged in the cylinder head (14). The admission valves (40.1, 40.2) of respectively two pump cylinders (12.1, 12.2), in the case of a radial piston pump, or three pump cylinders, in the case of an axial piston pump, that are respectively provided with two plungers (18.1, 18.2) moving out-of-phase in relation to each other about 180°, or about 120° for respectively three plungers, are mechanically interconnected by means of a pivotable rocker (42.1). The position of the rocker (42.1) is controlled by a single actuator (44.1). During the delivery stroke of a plunger (18.1, 18.2), the admission valves (40.1, 40.2) associated with the rocker (42.1) and located in an open position are closed by means of a pulse-type excitation of the actuator (44.1) and a resulting displacement of the rocker (42.1).

Description

High pressure pump for internal combustion engines

The invention relates to a high-pressure feed pump, in particular for an injection system for internal combustion engines, according to the preamble of claim 1.

CH-A-689281 discloses a fuel injection system for an internal combustion engine, in particular for a diesel engine, and a method for monitoring the same. For each combustion cylinder, the fuel injection system has at least one injection element controlled by a control unit, which has an injection opening leading into the cylinder, which can be closed by the latter, and a pressure space arranged in front of the latter. The pressure chamber is connected to a high-pressure part supplied by a fuel pump depending on engine speed, load and load change. The quantity of fuel injected into the combustion cylinder can be supplied by means of a quantity metering device, which is preferably connected upstream of the fuel pump and operated by the control unit. The quantity metering device has a valve which is assigned to a pump piston of the fuel pump.

EP-A-1101931 describes a high-pressure scribing system with a common rail, which has a channel element provided with at least one outlet channel with opposing end faces. A plunger cylinder of a high-pressure pump and, on the other hand, a common rail are connected to the end faces via high-pressure sealing surfaces, so that the high-pressure pump can suck in a delivery medium via an inlet valve and can introduce it with increased pressure through the outlet channel of the channel element and an outlet valve via an outlet channel into the pressure space provided in the common rail. The flow rate of the pumped medium to the pump cylinder is controlled by a suction throttle valve protruding into a transfer channel.

The present invention is based on the object of providing a high-pressure feed pump with a precise, reliable and particularly cost-effective flow rate control.

This object is achieved by means of a high-pressure feed pump according to claim 1. Particularly preferred embodiments of the invention are specified in the dependent claims.

The high-pressure feed pump according to the invention, which is intended in particular for use in an injection system for internal combustion engines, has at least two delivery spaces, each delimited by a pump cylinder and a driven plunger. The two delivery spaces are connected to a low-pressure inlet channel via inlet valves controlled by a single actuator and to a high-pressure outlet channel via a pressure-controlled outlet valve. In a preferred embodiment, valve members of the inlet valves are connected to one another by means of a rocker pivotally mounted on an actuator shaft of the actuator. When the actuator is excited, the actuator shaft is shifted and those inlet valves in an open position are closed, at which the assigned plunger is in a delivery stroke.

The precision of the delivery quantity metering of the high-pressure delivery pump according to the invention corresponds to that of known high-pressure delivery pumps. In the case of the subject matter of the invention, however, this is achieved by a smaller number of required actuators with significantly less material and cost. In addition, the requirements for the actuator are reduced by the fact that it operates in a pulsed mode and is therefore only in an excited state for short periods. Another factor in reducing costs is the modular construction of a preferred embodiment, in which the cylinder heads, cylinder bodies and a housing for receiving an eccentric shaft form separate assembly units which are pressed tightly against one another by means of bolts and screw connections. Furthermore, in one embodiment, the housing and the eccentric shaft are designed such that simple assembly is possible by inserting the eccentric shaft into the same from one end of the housing.

Particularly preferred embodiments of the high-pressure feed pump according to the invention are described in

The following explains the drawing. It shows purely schematically:

1 shows a longitudinal section through a high-pressure feed pump according to the invention;

FIG. 2 shows a detail from the high-pressure feed pump shown in FIG. 1 with two plunger positions that are 180 ° out of phase with one another and an inlet valve control for both Pump cylinder by means of a rocker, the middle position of which is controlled by an actuator; and

3 shows a cross section through the high-pressure feed pump shown in FIG. 1 along the section plane A shown in FIG. 2.

1 shows a longitudinal section of a high-pressure feed pump 10 according to the invention in the design of a radial piston pump with four pump cylinders 12.1, 12.2, 12.3, 12.4 in a row arrangement. The high-pressure feed pump 10 is provided for internal combustion engines, in particular for diesel engines with a common rail. Each of the pump cylinders 12.1, 12.2, 12.3, 12.4 has a similar structure and has a delivery space limited by the inner walls of a cylinder head 14 common to all pump cylinders 12.1, 12.2, 12.3, 12.4, a cylinder body 16 and a plunger 18.1, 18.2, 18.3, 18.4 20 on. The inner walls of the hollow cylindrical cylinder bodies 16 are designed as narrow sliding fits (2 μm to 10 μm) for the plungers 18.1, 18.2, 18.3, 18.4. The cylinder bodies 16 are clamped in a sandwich construction between the cylinder head 14 and the housing 22 by means of bolts 24 and pressed tightly against one another.

The plungers 18.1, 18.2, 18.3, 18.4 are supported over them by compression springs 26 against the cylinder body 16 and sit with their plunger feet 27 on a lubricant film slidingly on two-part rolling elements 28. The rolling elements 28 encompass cylindrical crank bearings 30, which act on the drive of the plungers 18.1, 18.2, 18.3, 18.4 serving eccentric shaft 32 rotatable are stored. The two-part crank bearings 30 in turn encompass eccentrics which are eccentrically offset from the longitudinal axis of the eccentric shaft 32. The eccentric shaft 32 is rotatably mounted on shaft bearings 31 in the housing 22. In the arrangement shown with four pump cylinders 12.1, 12.2, 12.3, 12.4, there are two shaft bearings 31 at the front end regions of the housing 22 and a third shaft bearing between the pump cylinders 12.2 and 12.3. The eccentric shaft 32 tapers on one side to form a conical drive pin 33 protruding from the housing 22. Lubricant films are also located between the rolling elements 28 and the crank bearings 30 to reduce friction. The lubricant is supplied through a channel 34 located within the eccentric shaft 32 and arranged centrally to its longitudinal axis with radial outlets 34 'to the rolling elements 28 and shaft bearings 31. After lubrication has taken place, the lubricant collects in a lubricant sump 35, from which it is added in a known manner a lubricant supply not shown is returned.

The plungers 18.1, 18.2, 18.3, 18.4 of the pump cylinders 12.1, 12.2, 12.3, 12.4 differ in their stroke position shown in FIG. 2: the plunger designated 18.1 is at a bottom dead center at the beginning of the delivery stroke, the one designated 18.2 an upper dead center at the beginning of the suction stroke, i.e. shifted by 180 ° against the stroke position of the plunger 18.1, the plunger designated 18.3 in the middle conveying stroke position, i.e. 90 ° ahead of the stroke position of the plunger 18.1, and the plunger designated 18.4 in the middle suction stroke position, i.e. shifted by 180 ° against the stroke position of the plunger 18.3. A cylinder head body 36 of the cylinder head 14 has four identical, one of the four pump cylinders 18.1,

18.2, 18.3, 18.4 assigned intake valves 40.1, 40.2,

40.3, 40.4, each with a valve member movably arranged in a cylindrical recess in the form of a

Valve lifter 38.1, 38.2, 38.3, 38.4. For a better overview, all inlet valves 40.1, 40.2, 40.3, 40.4 are shown in their closed position in FIG. 1

In each case two inlet valves 40.1 and 40.2 as well as 40.3 and 40.4, which are assigned to the plungers 18.1 and 18.2 as well as 18.3 and 18.4, are actuated via a pivotable rocker 42.1 or 42.2. The middle support position of the rocker 42.1, 42.2 is controlled by one actuator 44.1, 44.2 each.

In the cylinder head body 36 there is a tube-like inlet duct 46, which extends in a straight line in the longitudinal direction and is connected to the recesses for the inlet valves 40.1, 40.2, 40.3, 40.4 and serves to supply a conveying medium 48. The delivery medium 48 is already in the inlet channel 46 at a pressure between 100 kPa and 600 kPa, which was generated by a pre-delivery pump, not shown.

As shown for better clarity only in FIG. 3, the cylinder head 14 also has a pressure-controlled outlet valve 50.1, 50.2, 50.3, 50.4 in a corresponding recess for each pump cylinder 12.1, 12.2, 12.3, 12.4. The recesses are connected to a high-pressure outlet channel 52, the volume of which forms a pressure accumulator.

FIG. 2 shows an enlarged detail from FIG. 1 with two jointly controlled inlet valves 40.1, 40.2 shown. 2, further details of the structure and the mode of operation of the high-pressure feed pump 10 are described below. Due to the similar structure, these details as well as their function can be transferred to the part of the high-pressure feed pump 10, not shown.

The delivery chamber 48 of the pump cylinder 12.1, 12.2, 12.3, 12.4 narrows in the direction of the inlet valve 40.1, 40.2, 40.3, 40.4 to an inlet valve seat 54.1, 54.2, 54.3, 54.4 interacting with a valve disk 56 of the valve lifter 38.1, 38.2, 38.3, 38.4. The valve tappet 38.1, 38.2, 38.3, 38.4 is prestressed at its end region opposite the valve disk 56 by means of a compression spring 58 against the cylinder head body 36 into its closed position. In the closed position, the valve plate 56 sits tightly on the inlet valve seat 54.1, 54.2, 54.3, 54.4. and prevents the delivery medium 48 from escaping from the delivery chamber 20 into the inlet channel 46 or possibly from the inlet channel 46 into the delivery chamber 20. A hemispherical valve tappet head 60 formed on the valve tappet 38.1, 38.2, 38.3, 38.4 is in a bowl-shaped valve tappet receptacle 62 of the rocker 42.1, 42.2 mounted. The rocker 42.1, 42.2 has on the same side in the opposite end region a second valve lifter receptacle 62 for receiving the assigned second valve lifter 38.1, 38.2, 38.3, 38.4 of the second inlet valve 40.1, 40.2, 40.3, 40.4. A hemispherical actuator receptacle 64 is formed in the center on the side opposite the valve lifter receptacles 62 on the rocker 42.1, 42.2.

The actuator shaft 66 presses into the actuator receptacle 64. A displacement of the rocker 42.1, 42.2 in the direction of the longitudinal axis of the actuator shaft 66 is controlled by the actuator 44.1, 44.2. The actuator stem 66 is biased against the actuator 44.1, 44.2 in the direction of the open position of the associated inlet valves 40.1, 40.2 or 40.3, 40.4 by means of an actuator stem spring 67 designed as a compression spring. The preload of the actuator stem spring 67 is greater than the sum of the oppositely acting preloads of the respectively assigned compression springs 58 of the inlet valves 40.1, 40.2 or 40.3, 40.4. The actuator 44.1, 44.2 preferably has an electromagnet; a piezoelectric element would also be conceivable. In the case of an electromagnet, the actuator shaft 66 is designed as an extension of an actuator armature. The actuator 44.1, 44.2 and thus the position of the actuator shaft 66 is influenced by a preferably not shown, preferably electronic control. The actuator 44.1, 44.2 is mounted on a cylinder head cover 68 fastened to the cylinder head 14. The cylinder head cover 68 has a central recess through which the actuator shaft 66 is movably guided. The cylinder head cover 68 spans a recess in the cylinder head body 36, in which the valve tappet heads 60 with the compression springs 58 protrude and the rocker 42.1, 42.2 located on the valve tappet heads 60 is located.

Inside the pump cylinders 12.1, 12.2, 12.3, 12.4, circumferential grooves 70 with a semicircular cross section open towards the plungers 18.1, 18.2, 18.3, 18.4 are incorporated. They are connected to a return duct 72 shown in FIG. 3 and serve to return leakage quantities of the conveying medium 48 which are caused by the tight sliding fit of pump cylinders 12.1, 12.2, 12.3, 12.4 and Plungers 18.1, 18.2, 18.3, 18.4 have passed through to a reservoir, not shown, for the medium 48.

A thrust washer 78 is attached to a housing cover 74 with a passage for the drive pin 33 opposite an outer circumferential shoulder of the eccentric shaft 32. On the opposite side of the housing 22, a further thrust washer 78 supports the end face of the eccentric shaft 32 directly against a further housing cover 74, which is provided with a passage for the lubricant supply. The thrust washers 78 serve to transversely guide the eccentric shaft 32 in the housing 22. On the side of the drive pin 33, a circumferential lip seal 80 is connected to the housing cover 74, which prevents lubricant from escaping from the housing 22 by its contact with the drive pin 31.

In the connecting surfaces between the housing 22 and the cylinder body 16, between the cylinder body 16 and the cylinder head 14 and between the cylinder head body 36 and the cylinder head cover 68, sealing rings 82 are inserted in appropriately shaped grooves. Due to the strong pressing of the above-mentioned parts against one another, a tight seal of the high-pressure feed pump 10 is ensured and escape of the delivery medium 48 or the lubricant is prevented.

The discharge of the delivery medium 48 during the delivery stroke of the plungers 18.1, 18.2, 18.3, 18.4 takes place through the pressure-controlled outlet valves 50.1, 50.2, 50.3, 50.4 into the outlet channel 52. As shown in FIG. 3, the outlet valves 50.1, 50.2, 50.3, 50.4 designed as ball valves of a known type. A ball 84 is in their closed position is pressed into their outlet valve seat 88 by a prestressed outlet pressure spring 86 and closes the high-pressure outlet channel 52 tightly against the delivery chamber 20. If the pressure of the conveyed medium 48 in the delivery chamber 20 exceeds the pressure in the outlet channel 52 by one depending on the preload of the outlet pressure spring 86, in As a rule, the amount is very small, the ball 84 lifts off its outlet valve seat 88 and the medium 48 escapes into the high-pressure outlet channel 52. The ball 84 is in a cylindrical recess that narrows conically towards the outlet valve seat 88 between its outlet valve seat 88 and an end face on the delivery chamber side of a pin 90 carrying the outlet pressure spring 86. The outlet channel 52 is connected to this recess. A plate-like widening 92 of the pin 90 lies on a shoulder 93 in the recess of the housing 22. An Allen screw 94 presses the widening 92 against the shoulder 93 and closes the recess in the housing 22.

The mode of operation of the high-pressure feed pump 10 shown in FIGS. 1 to 3 is described below. A first plunger 18.1 of a pump cylinder 12.1 is initially in its suction stroke, the assigned outlet valve 50.1 in its closed position and the actuator 44.1 in a non-excited state. The assigned first inlet valve 54.1 is in the open position during the suction stroke due to the dominant preload of the actuator stem spring 67.

The delivery medium 48, which is already under the pressure generated by an upstream, not shown, pre-delivery pump, is from the low-pressure inlet channel

46 through the open inlet valve 40.1 in the Delivery chamber 20 sucked. The plunger 18.1 reaches bottom dead center at the end of its suction stroke. In this position of the plunger 18.1 shown in FIG. 3, the volume of the delivery space 20 is at a maximum. In the subsequent delivery stroke, the delivery volume is reduced by the movement of the plunger 18.1 and delivery medium 48 is pushed back through the open inlet valve 40.1 into the inlet channel 46 until the delivery volume corresponds to the desired delivery rate. Due to a pulse-like excitation of the actuator 44.1, the actuator shaft 66 is attracted at this time along its longitudinal axis against the bias of the actuator shaft spring 67 and the inlet valve 40.1 is closed. The rocker 42.1 follows this movement on account of the pretension of the compression spring 26 attached to the valve tappet 38.1 and the pressure increase then occurring in the delivery chamber 20 as a result of the movement of the plunger 18.1 in the direction of the inlet valve 40.1. As a result, the valve plate 56 of the valve lifter 38.1 is pressed against its inlet valve seat 54.1, so that no fluid 48 can leave the delivery chamber 20 through the inlet valve 40.1. A second inlet valve 40.2 assigned to the same rocker 42.1 remains in its open position despite the excitation of the actuator 44.1, since the second plunger 18.2 moving out of phase with the first plunger 18.1 is in the suction stroke and because of the pressure difference between the low-pressure inlet channel 46 and the valve plunger 38.2 keeps the valve plunger 20 open in the direction of the pumping chamber 20.

After the pulsed excitation of the actuator 44.1 has ended, the first inlet valve 40.1 remains in its closed position until the next suction stroke. The assigned second inlet valve 40.2 is by the Termination of the excitation of the actuator 44.1 is not influenced and remains in its open position.

After the plunger 18.1 of the first pump cylinder 12.1 has passed through the top dead center and has passed into the suction stroke, the first inlet valve 40.1 is opened and the conveying medium 48 is sucked into the conveying space 20. The assigned second plunger 18.2 passes through the bottom dead center and begins to push the pumped medium 48 back into the inlet channel 46 until the inlet valve 40.2 is closed by means of a renewed pulse-like excitation of the actuator 44.1.

The described mode of operation continues periodically and, by controlling the time period from opening to closing the inlet valves 40.1, 40.2, 40.3, 40.4, it is possible to control the amount of the conveyed medium 48 pressed into the high-pressure outlet channel. The amount ranges from a maximum, namely a delivery volume per plunger period and pump cylinder 12.1, 12.2, 12.3, 12.4, to zero, in which case the inlet valves 40.1, 40.2, 40.3, 40.4 remain open during the entire plunger period. In the latter case, the high pressure feed pump 10 operates at idle.

In contrast to the method of operation described above, in which the delivery rate is determined by closing the inlet valves 40.1, 40.2, 40.3, 40.4 in the delivery stroke, in a further embodiment the delivery rate can be achieved in the suction stroke by closing the inlet valves 40.1, 40.2, 40.3, 40.4 be limited. For this purpose, the preloads of the compression springs 58 of the inlet valves 40.1, 40.2, 40.3, 40.4 and the actuator shaft 66 have to be adjusted accordingly. The bias of the Compression springs 58 must be selected such that the inlet valves 40.1, 40.2, 40.3, 40.4 can also be closed during the suction stroke. In addition, the actuators 44.1, 44.2 need to be modified, in particular with regard to longer holding times.

The row arrangement of radial piston pumps shown in FIGS. 1 to 3 can alternatively also be replaced by a boxer arrangement or an arrangement with pump cylinders rotated through an angle around the longitudinal axis of the eccentric shaft.

With an axial piston pump, it is also possible to control three pump cylinders with plungers, which are moved against each other with a phase shift of 120 °, with a single rocker and one actuator. In this case, the rocker is preferably star-shaped or triangular. Three corresponding valve lifter receptacles can, for example, be arranged uniformly around a central actuator receptacle. The dosage of the delivery rate is limited to a range between zero and about 2/3 of the maximum delivery rate before irregular delivery occurs. The maximum delivery rate corresponds to the delivery rate in the event that each of the inlet valves is closed exactly at the point in time at which the respectively assigned plunger passes through its bottom dead center before the subsequent pressure stroke.

In embodiments as radial or as

Axial piston pumps can of course one or more pump cylinder pairs or pump cylinder triplets each by means of a common rocker 42.1, 42.2 and one only actuator 44.1, 44.2 are operated in the arrangement described.

The plungers 18.1, 18.2, 18.3, 18.4 can also be floatingly mounted on the rolling elements 28 by means of pressure compensation for extremely low-friction movement. For this purpose, the plungers 18.1, 18.2, 18.3, 18.4 are equipped with hollow shafts in which stamps are freely movable. During a delivery stroke of the plungers 18.1, 18.2, 18.3, 18.4, the plunger is pressed in the direction of the rolling element 28 and lubricant located in the hollow shaft is pressed between the plunger foot 27 and the rolling element 28.

The assembly of the high-pressure feed pump is particularly simple and inexpensive due to the modular construction of the separately manufactured assembly units cylinder head 14, cylinder body 16 and housing 22. The possibility of lateral insertion of the eccentric shaft 32 into the housing 22 also contributes to simple assembly.

Claims

claims

1.High pressure feed pump, in particular for an injection system for internal combustion engines, with at least one of a pump cylinder (12.1, 12.2, 12.3, 12.4) and a driven plunger (18.1, 18.2, 18.3, 18.4) limited delivery space (20), which via a by means of a Actuator (44.1, 44.2) controlled inlet valve (40.1, 40.2, 40.3, 40.4) is connected to a low-pressure inlet channel (46) and via a pressure-controlled outlet valve (50.1, 50.2, 50.3, 50.4) to a high-pressure outlet channel (52) , characterized by at least two delivery spaces (20), each with an inlet valve (40.1, 40.2, 40.3, 40.4), at least two inlet valves (40.1, 40.2, 40.3, 40.4) being controlled by means of a single actuator (44.1, 44.2).

2. High-pressure feed pump according to claim 1, characterized in that the inlet valves (40.1, 40.2, 40.3, 40.4) and the outlet valves (50.1, 50.2, 50.3, 50.4) are arranged in a cylinder head body (36) of a cylinder head (14).

3. High-pressure feed pump according to claim 1 or 2, characterized in that the plungers (18.1, 18.2, 18.3, 18.4) assigned to the inlet valves (40.1, 40.2, 40.3, 40.4) controlled by means of the actuator (44.1, 44.2) are synchronous, but mutually, preferably driven by 180 ° or 120 °, out of phase.

4. High pressure feed pump according to one of claims 1 to 3, characterized in that each inlet valve (40.1, 40.2, 40.3, 40.4) has a valve member (38.1, 38.2, 38.3, 38.4) cooperating with an inlet valve seat (54.1, 54.2, 54.3, 54.4), the valve members of the inlet valves (40.1 , 40.2, 40.3, 40.4) are connected to one another by means of a rocker (42.1, 42.2) pivotable on an actuator shaft (66) of the actuator (44.1, 44.2) and the actuator (44.1, 44.2) controls the position of the actuator shaft (66).

5. High-pressure feed pump according to claim 4, characterized in that the valve members (38.1, 38.2, 38.3, 38.4) are ^' biased into their closed position.

6. High-pressure feed pump according to claim 4 or 5, characterized in that the actuator shaft (66) is biased in the direction of the open position of the valve members (38.1, 38.2, 38.3, 38.4).

7. High-pressure feed pump according to one of claims 4 to 6, characterized in that the ₍ rocker (42.1, 42.2) associated, located in an open position inlet valves (40.1, 40.2, 40.3, 40.4) of the pump cylinder (12.1, 12.2, 12.3, 12.4), the plungers (18.1, 18.2, 18.3, 18.4) of which are in the delivery stroke, are moved into a closed position when the actuator shaft (66) is displaced by excitation of the actuator (44.1, 44.2).

8. High-pressure feed pump according to claim 1 to 7, characterized in that for the purpose of quantity metering, the inlet valves (40.1, 40.2, 40.3, 40.4) during the delivery stroke of the plungers (18.1,

18.2, 18.3, 18.4) are placed in their closed position.

9. High-pressure feed pump according to one of claims 1 to 8, characterized in that the high-pressure feed pump (10) is designed as a radial piston pump and two inlet valves (40.1, 40.2, 40.3, 40.4) are controlled by means of a single actuator (44.1, 44.2).

10. High-pressure feed pump according to one of claims 1 to 9, characterized in that the high-pressure feed pump (10) is designed as an axial piston pump and two or three inlet valves (40.1, 40.2, 40.3, 40.4) are controlled by means of a single actuator (44.1, 44.2) , ^' wherein the rocker (42.1, 42.2) has three star-shaped rocker arms in the case of three inlet valves (40.1, 40.2, 40.3, 40.4).