EP1651856A1

EP1651856A1 - Fuel injection device

Info

Publication number: EP1651856A1
Application number: EP04738651A
Authority: EP
Inventors: Friedrich Boecking
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2003-07-24
Filing date: 2004-06-09
Publication date: 2006-05-03
Also published as: DE10333695A1; WO2005010341A1; JP2006513368A; US20060175436A1; KR20060041264A

Abstract

The invention relates to a fuel injection device (1), comprising an injection valve (9), a pipe (5), for supplying fuel under high pressure to the injection valve (9) in operation and a control valve (41), for controlling the pressure in a control chamber (43) of the injection valve, which is connected to the above-mentioned pipe (5), said control valve having a mobile valve element (51) which can be actuated by an actuator (31) by means of a hydraulic coupler (38). According to said invention, the pistons (39, 40) are arranged within and parallel to each other; a multiplicator chamber (72) is arranged at the ends of the pistons (39, 40), facing the actuator (31); a filling chamber (71-2), provided inside the external piston (39), is connected to the above-mentioned pipe (5) and the direction of the closing movement of the mobile valve element (51) corresponds to the direction of the fuel flowing out of the control chamber (43), so that said control valve is at least partially force-equilibrated because of the pressure acting upon the other piston (40) in the filling chamber (71-2).

Description

Fuel injector

State of the art

The invention relates to a fuel injection device according to the preamble of patent claim 1.

A CR injector (CR = Common Rail) with a piezo actuator (= Piezostelier) and translation by hydraulic coupler is known. Integrated couplers with pistons arranged coaxially one inside the other are also known. The known device uses an A valve as a control valve. Because of possible cavitation, this has to be produced with a special shape and is complex and can only be designed with a relatively small diameter, since otherwise the forces on the valve become too high for actuation by a piezo actuator.

Advantages of the invention

The fuel injection device according to the invention for internal combustion engines with the characterizing features of patent claim 1 has the advantage over the fact that a CR injector with a piezo studio is created, in which a large cross section of the valve is possible and this is designed as an I-valve. This allows the injection valve to open and close more quickly. The integrated coupler enables a short overall length of the device. The coupler is supported by CR printing.

drawing

An embodiment of the fuel injection device according to the invention is shown in the drawing and is explained in more detail in the following description. The sole figure shows the essential components of a fuel injection device according to the invention with an injection valve and a control valve as well as a hydraulic coupler.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT The fuel injection device 1 according to the invention is designed by a

Pressure accumulator (common rail) 3 is supplied with fuel under high pressure via a high-pressure line 5, from which fuel reaches an injection valve 9 via an injection line 6. An internal combustion engine normally has several such injection valves, and only one is shown for the sake of simplicity. The injection valve 9 has a valve needle (valve piston, nozzle needle) 11, which in its closed position closes injection openings 13 through a conical valve sealing surface 12, through which fuel is to be injected into the interior of a combustion chamber of the internal combustion engine. The fuel reaches the area of the nozzle needle via an annular nozzle chamber 14, from which it pressures via a control surface 15 designed as a pressure shoulder

Opening direction of the nozzle needle allowed to exercise. When the pressure mentioned exerts a force in the opening direction on the valve needle which overcomes forces opposing this opening, the valve opens. A is used to control the opening and closing of the injection openings

Actuator 31. Depending on a control at a mechanical output, this generates a deflection and a force for actuating further elements. In the example it is an electrically operated actuator. In the example, it is an actuator that has a piezoelectric element, namely a piezo actuator. Depending on an electrical control in the vertical direction of the drawing and thus in its longitudinal direction, the actuator assumes an elongated configuration or a shortened configuration. In the example, an actuator with such a construction is provided, which, when energized (connection to a direct current supply), assumes an elongated configuration without energization takes a shortened configuration. The actuator forms a capacitive load and does not absorb any power loss when continuously energized. It may be advantageous or necessary to replace the piezo actuator by a tensioning device, e.g. B. spring, so that the piezoelectric elements contained in the actuator are always stressed. This is known to the experts and is therefore not referred to in the following. While the upper end of the piezo actuator is anchored in the injector in a manner not visible in the drawing, the lower end of the piezo actuator serves to ultimately use its force and movement to open and close the injection openings. For this purpose, a hydraulic coupler 38 is provided for its coupling, which has a piston 39 coupled to the piezo actuator and a further piston 40. In the present application, the travel of the further piston 40 is generally required to be increased by the coupler in comparison to the travel of the piston 39 (by suitable selection of the hydraulically effective piston surfaces). The construction and operation of the hydraulic coupler is described below. The piezo actuator is a capacitive load and therefore does not draw any continuous current.

When the piston 40 of the hydraulic coupler, which is not directly connected to the piezo actuator, opens a control valve 41 (or exhaust valve), the pressure drops in a fuel-filled control chamber 43, into which the upper one

End portion of the nozzle needle engages. The control chamber 43 is filled with fuel under pressure via an inlet throttle 47, and when the control valve 41 is open, fuel flows out of the control chamber 43 via an outlet throttle 49. The outflow of fuel is supported by forces that tend to move the nozzle needle 11 to its open position. When the control valve 41 is closed, a movable valve piece 51 seals against a valve seat 53 and is mechanically coupled to the piston 40. The control quantity flowing out of the control chamber when the valve piece 51 is open is discharged through a leakage channel 55. When the valve piece 51 is closed, the control chamber applies rail pressure (= pressure in line 5), the pressure acting on the surface with the diameter d3.

In the example, the pistons 39 and 40 are arranged parallel to one another and one inside the other, advantageously in terms of production technology, coaxially one inside the other (integrated coupler). The way in which they are coupled is explained below. An arrow is drawn in the piston 39, which indicates the movement of this piston when the actuator executes a downward movement in the drawing. An arrow is drawn in the piston 40, which indicates the movement of this piston when the piston 39 executes the movement indicated by its arrow. By comparing the arrow of the piston 40 with the direction in which the movable valve element of the valve to be actuated by the hydraulic converter 38 has to be moved in order to open or close, it is immediately apparent from the drawing whether the direction shown in the drawing is that of the aforementioned Arrows corresponds to an opening process or a closing process of the valve mentioned.

The movable valve piece 51 is essentially spherical. In particular, it rests against the valve seat 53 in the closed state with a surface region that essentially has the shape of a spherical cap. In the example, the movable valve member 51 must be pressed against its valve seat to exert a force to prevent the pressurized fuel from flowing out of the control chamber 43. It is thus in the locked state when the movable valve part has been moved "inward", namely in the direction from a region of lower pressure to a region of higher pressure into its locked position, and therefore that

Control valve in the present case referred to as an I-valve. In other words, the direction of the opening movement of the movable valve part coincides with the direction of fuel flowing out of the control chamber. In contrast, a valve whose movable valve part has been moved "outwards" in its blocking position, namely in the direction from the high pressure in the control chamber to a region of lower pressure leakage pressure, is referred to as the A valve.

The ball valve mentioned can have a free ball without a rigid connection to another part. A ball is less susceptible to cavitation due to its aerodynamic shape. A suitable other construction for the I-valve may be used instead, e.g. B. a plug valve with a conical surface area, which cooperates with the valve seat. The valve part can be rigidly coupled to the associated piston, so that the control valve can be opened particularly quickly. The actuator 31 is connected to the piston 39 by a rod 61 with a diameter d5. The piston 40 is connected to the movable valve part 51 to be actuated by a rod 63 with a diameter d1. The inner piston 39 has a diameter d4, the outer piston 40 has an annular piston surface of size f2. The clear diameter of the valve seat 53 where the movable valve part rests against it is d3.

Guide gaps 65 and 67, which serve to slide the pistons and through which a coupler volume is filled with fuel, are formed in the region of the cylindrical outer surface of the outer piston (opposite a housing, not shown) and in the region of the mutual sliding guide of the two pistons.

The areas f1 and f3 to f5 corresponding to the diameters mentioned above (for circular cross sections) and the area f2 mentioned are decisive for the function. Circular cross sections are expedient for the production, but the invention is not restricted to this.

The end regions of the pistons 39 and 40 facing the actuator 31 engage in a common translator space 72. The other end region of the piston 39 engages in a filling space 71-2; this is connected via bores in the lower end wall of the piston 40, which is connected to the line 5. The other end region of the inner piston 40 projects into the filling space 71-2. The translator room 72 is filled via the guide columns 65 and 67. The translator room 72 is penetrated by the rod 61. The filling space 71-1 is penetrated by the rod 63. The pistons 39 and 40 move in opposite directions and at different speeds because of the desired path translation from the actuator to the control valve. The actuator 31 (piezo studio) is in the closed state of the injection valve

9 de-energized and shortened. To open the control valve 41, the electrical current to the actuator 31 is switched on and the actuator becomes longer. As a result, the piston 39 (first booster piston) is moved downward in the figure. CR pressure (= pressure of the pressure accumulator) is in the idle state in the translator space 72 and in the filling space 71-2 or common rail) as system pressure. In the translation space 72, the pressure drops as the piston 39 moves downward. This decrease in pressure moves the piston 40 (second booster piston) upward and opens the control valve 41, which is an I-valve, by moving the valve part 51 in the same direction. For particularly quick opening of the valve part 51, in embodiments of the invention this may be firmly connected to the rod 63 and thus to the piston 40. Because of the CR pressure in the booster space 72, the seat diameter d3 of the valve part 51 can be selected to be very large, since the piston 40 largely compensates for this area with its side located in the booster space 72. When the valve 41 is closed, the movement of the piston 39 upwards is supported by the spring 75 and by the pressure in the filling chamber 71-2. The invention thus creates an advantageous I-valve servo injector with CR pressure support for very quick opening and closing of the injection valve. The coaxial coupler ensures a short overall length. An important feature of the invention is that on the side of the

Piston 39 (in the booster chamber) facing away from the control valve, rail pressure is present which supports the actuation of the control valve and counteracts the pressure acting on the valve part 51 in the locked state from the control chamber 43. Because of the rail pressure in the translator room 72, d3 is largely balanced. There is therefore a larger excess of force, which is supplied by the actuator, compared to the prior art, for accelerating the mass of the movable valve part. The invention thus creates a variant with a partially balanced (= partially balanced in terms of force) control valve, the valve being an I-valve. The force to be supplied by the actuator to close the valve is therefore smaller compared to the known one. Instead, in one embodiment, a valve 51 is provided with a larger diameter d3 compared to the known one, which enables the injection valve to open and close more quickly because the increase and decrease in flow therein is greater than in the known smaller A valve. A compression spring 75 in the filling chamber 71-2 pushes the pistons apart and ensures that the coupler is in good contact with the actuator 31 and, when the valve is closed, the valve part 51 with the valve seat 53. The device described so far has further features. At least in a region of the rod 61 connecting the actuator 31 to the hydraulic coupler there is a further filling space 90, which is connected to the line 5, at a distance from the space of the coupler closest to the actuator 31. In the example, the further filling space 90 surrounds the actuator 31 in its lower end region. It preferably surrounds the entire actuator 31. A guide gap 94 of the rod 61 is dimensioned for additional filling of the adjacent space of the coupler with fuel under pressure. One advantage is the additional filling of the coupler with fuel under high pressure.

In embodiments of the invention, the further filling space 90 is not present or is not connected to the line 5 and does not have the function of a filling space. In this case, it may be expedient to dimension a bore, in which the rod 61 is guided in a housing (not shown) of the entire device, for the smallest possible outflow of fuel from the coupler.

The invention also encompasses embodiments in which the fuel under high pressure is not supplied by a high-pressure accumulator, but by a pump assigned to the injection valve (e.g. pump-injector unit, unit injector), which also feeds the filling chamber.

Claims

claims

1. Fuel injection device (1) with an injection valve (9), the one

Injection valve (9) when operating fuel under high pressure supply line (5), a control valve (41) controlling the pressure in a control chamber (43) of the injection valve connected to said line (5), the movable valve part (51) of an actuator (31) can be actuated via a hydraulic coupler (38) which has two pistons (39, 40) cooperating with a coupler volume of the coupler, the seat (53) of the movable valve part (51) having a clear cross-sectional area f3, with means for Filling the coupler volume via guide gaps (65, 67) of the pistons (39, 40) with fuel under pressure,

characterized in that the pistons (39, 40) are arranged parallel to one another, that at the ends of the pistons (39, 40) facing the actuator (31) a translator space (72) is arranged that inside the outer piston (39 ) a filling space (71-2) is provided, which is connected to said line (5), that one (39) of the pistons with a cross-sectional area f4 with the actuator (31) mechanically via a rod (61) with a cross-sectional area f5 is coupled that the other piston (40), which has a piston surface f2, actuates the control valve (41) via a rod (63) with a cross-sectional area f1 that is smaller than f2, that the direction of the opening movement of the movable valve part (51) with the Direction of fuel flowing out of the control chamber (43) coincides, so that the control valve is at least partially force-balanced due to the pressure acting on the further piston (40) in the booster chamber (72).

2. Fuel injection device (1) according to claim 1, characterized in that at least in a region of the rod (61) connecting the actuator (31) to the hydraulic coupler at a distance from the space of the coupler closest to the actuator (31) there is a further filling space (90), which is connected to said line (5) and is connected to the coupler via a guide gap (94) in the rod (61).