High pressure pump prior art
The invention relates to a high-pressure pump, in particular a radial or
Series piston pump. Specifically, the invention relates to the field of fuel pumps for fuel injection systems of air-compression, self-igniting internal combustion engines. The high pressure pump can also serve as a piston pump for conveying other suitable liquids.
From DE 195 15 191 A1 a high-pressure fuel pump is known. The high-pressure fuel pump has a cylinder whose upper part to the outside of the
Head cover, which is part of the motor housing, is exposed. The remaining portion of the high-pressure fuel pump is accommodated in a housing hole of the head cover. A pump cam is mounted on a valve camshaft for driving an intake / exhaust valve and drives the high pressure fuel pump. Since that
Further, the timing with which the pressurized fuel is ejected controlled by the operation of a solenoid valve further enhances the accuracy with which the fuel delivery is controlled.
The known from DE 195 15 191 A1 high-pressure fuel pump is a suction throttled pump in which there are several disadvantages. Disadvantages are high noise, poor controllability and the appearance of mechanical
Vibrations due to cavitations occurring in the feed lines to the intake valves. Pressure waves between a metering unit and the suction valve have an unfavorable effect on the operation. Disclosure of the invention
The high pressure pump according to the invention with the features of claim 1 has the advantage that an improved embodiment realized, in particular a Metering of fuel and a compact design are possible. Specifically, a metering unit or the like can be saved, resulting in a significant cost reduction in the production. The measures listed in the dependent claims are advantageous
Further developments of the specified in claim 1 high pressure pump possible.
In contrast to high-pressure pumps with a suction-side volume flow control by means of a Zumessmengeneinheit in combination with spring-loaded intake valves, which have the disadvantages that at high pump speed no DC funding is guaranteed and that pressure oscillations in the low pressure noise, can advantageously realized a cost reduction by omitting a Zumessmengeneinheit be made possible even at high pump speeds equal promotion and noise reduction by avoiding pressure oscillations and possible cavitation in the low pressure can be achieved.
In a conventional embodiment overlap especially at
Multi-piston pumps with three or more pistons the suction phases. Pressure oscillations then lead to particularly large differences in the conveyed quantity. This can be avoided in an advantageous manner. It is possible that such differences in the upstream quantity are excluded.
Specifically, there is a great cost advantage in a high-pressure pump designed as a stamping pump. Also in the embodiment as a two-piston pump with a further actuator can be partially compensated by the saving of holes in the housing of the high-pressure pump additional costs. A major advantage of the direct control is the expansion of the pump speed and thus an improvement in the efficiency of the high-pressure pump. In addition, a very small size can be realized by the integration of the intake valve in the cylinder head. This also applies to very high pressures, for example of 300 MPa (3000 bar), as is conceivable for applications in commercial vehicles.
Advantageously, the inlet valve is designed as a magnetically controllable inlet valve. Furthermore, it is advantageous that the inlet valve is fixed by means of a screwed into the cylinder head screw plug on the cylinder head and that the
Closure screw is formed of a ferromagnetic material. This can the screw plug serves as a magnetic conductor, which increases the efficiency of the magnetic circuit and allows a high magnetic force.
In addition, it is advantageous that a magnetic coil is provided that by energizing the solenoid coil, a control of the inlet valve is made possible and that the
Solenoid coil is cooled by the feasible via the inlet valve in the pump chamber fuel. Thus, the cooling of the magnetic coil and the other elements of the magnetic circuit can be achieved by flushing with the fuel. It is also advantageous that the inlet valve has a valve body and one with the
Valve body to a sealing seat cooperating valve tappet, wherein the valve stem rests against the cylinder head, wherein a magnetically actuated plunger armature is provided and wherein the plunger armature for opening the seal formed between the valve body and the valve stem during magnetic actuation entrains the valve lifter. As a result, the magnetic force for actuating the inlet valve can be generated via the plunger armature, wherein the closure screw advantageously serves as a magnetic conductor. The inlet valve is in this case switched off
Magnetic coil preferably closed. If the magnet coil of the magnet is energized and the pump piston is at top dead center, for example, then the inlet valve opens. When fully filled, the inlet valve is preferably open until bottom dead center of the pump piston. Here, it is also advantageous that a shim is provided, which serves to specify a working air gap and a residual air gap for the plunger armature. As a result, a modular design is possible, with an adaptation to the particular application of the high pressure pump is possible by installing a suitable shim. As a result, the scope of the
High pressure pump increases, with a simple adaptation and a largely identical design of the high-pressure pump is possible.
It is also advantageous that a control is provided which the inlet valve in
Dependent on a movement of the pump piston of the pump assembly controls. On the one hand, it is advantageous that the controller for reducing a filling of the pump chamber of the pump assembly shortens the drive time at its end so that the inlet valve is closed before reaching a bottom dead center of the pump piston or the drive time at its end extended so that the inlet valve after reaching a bottom dead center of the pump piston is closed. Thus, the Ansteuerzeit can be reduced so that the inlet valve is closed again before reaching the bottom dead center of the pump piston, which is the amount of in the
Pump working space of flowing fuel decreases. On the other hand, this can also be be achieved in that the injection valve only after reaching the bottom
Dead center is closed, whereby the guided into the pump chamber fuel is partially conveyed back via the movement of the pump piston via the inlet valve in the opposite direction. In the first case, the pressure oscillations are reduced on the low pressure side. In the second case, preferably no cavities arise in the working cylinder. Depending on the application, the advantageous variant can be specially selected. Another possibility is that the activation time is shortened at its beginning so that the inlet valve is opened only after reaching a top dead center of the pump piston. Thus, the intake valve is not opened immediately after top dead center, so that the amount of fuel flowing into the pump working space is also reduced. In this case, a suitable combination of the drive types can be carried out by the controller. For example, the driving time can be shortened both at the beginning and at the end. Thus, can be in an advantageous manner
Implement partial fillings of the pump working space. Furthermore, pressure fluctuations with respect to the amplitude and frequency can be positively influenced by one or more throttles arranged upstream of the inlet valve. In addition, the volume control can be positively influenced. As a result, the noise behavior, which can be adversely affected by pressure oscillations in the low pressure, can be improved.
The inlet valve is preferably equipped with a closing spring which has a high spring bias in order to achieve a high closing dynamics.
Short description of the drawing
Preferred embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawings. It shows:
Fig. 1 is a high-pressure pump in a partial, schematic, axial
Sectional view according to an embodiment of the invention.
Embodiments of the invention
Fig. 1 shows a high-pressure pump 1 in a partial, schematic, axial sectional view according to an embodiment of the invention. The
High-pressure pump 1 can be designed in particular as a radial or in-line piston pump. Specifically, the high-pressure pump 1 is suitable as a fuel pump for
Fuel injection systems of air-compressing, self-igniting internal combustion engines. A preferred use of the high pressure pump 1 is for a fuel injection system having a fuel rail which stores diesel fuel under high pressure. However, the high-pressure pump 1 according to the invention is also suitable for others
Use cases. In particular, the high-pressure pump can also be configured as a piston pump for conveying suitable liquids, that is to say also other liquids as fuel.
The high-pressure pump 1 has a pump housing to which a cylinder head 2 is mounted. The cylinder head 2 has a projection 3 which projects into a bore of the pump housing. Here, in the approach 3, a cylinder bore 4 configured in the one
Pump piston 5 a pump assembly 6 is guided along an axis 7.
The high-pressure pump 1 also has a drive shaft 8, on which a cam 9 is provided. The cam 9 can in this case also be configured as a multiple cam or as an eccentric portion of the drive shaft 8. In operation, the drive shaft 8 rotates with the cam 9 about an axis of rotation 10 between the pump piston 5 of
Pump assembly 6 and the cam 9 is an operative connection 1 1, which is illustrated by the double arrow 1 1. For example, via a roller shoe and a roller mounted in the roller shoe, an actuating force from the cam 9 on the
Pump piston 5 are transmitted. A provision of the pump piston 5 can be made via a suitable plunger spring.
Thus, the pump assembly 6 of the cam 9 of the drive shaft 8 is driven. Depending on the configuration of the high-pressure pump 1, further pump assemblies can also be driven by the cam 9. In addition, further cams may be provided on the drive shaft 8, which serve to drive other pump assemblies. Depending on the configuration, a high-pressure pump 1 configured as a radial or in-line piston pump can thereby be realized. The pump piston 5 defines a pump working space 12 in the cylinder bore 4. An inlet channel 13, into which fuel is supplied, serves to supply fuel
Pre-feed pump is promoted. In the inlet channel 13, a first throttle 14 and a second throttle 15 are provided. The inlet channel 13 leads into a low-pressure chamber 16, which is formed by a recess 17 in the cylinder head 2.
The high-pressure pump 1 has an inlet valve 20. The low-pressure chamber 16 is part of the intake valve 20. The intake valve 20 is integrated in the cylinder head 2. Here, the inlet valve 20 is arranged in the recess 17 of the cylinder head 2. The Recess 17 is closed by a screw plug 21. Thus, the low pressure space 16 is closed to the environment. The
Closure screw 21 acts via a valve member 22 on a valve body 23 a. The closure screw 21 is screwed into the cylinder head 2 and thereby presses the valve body 23 against a formed on the cylinder head 2 contact surface 24. Die
Closure screw 21, the valve member 22 and the valve body 23 of the inlet valve 20 are thereby fixed in place. In addition, the plug 21 and the valve member 22 are preferably formed of a ferromagnetic material. In the valve body 23, a valve lifter 25 is guided. Here, the valve stem 25 cooperates with a formed on the valve body 23 valve seat surface 26 to a sealing seat. In this case, a valve spring 27 urges the valve tappet 25 against the valve seat surface 26. The valve spring 27 acts on an armature 30 via a valve element 28 and a shim 29. The armature 30 is designed as a plunger anchor 30. The plunger armature 30 is connected to the valve tappet 25. Thus, the valve stem 25 is acted upon by the bias of the valve spring 27. The valve stem 25, the valve element 28, the
The shim 29 and the plunger armature 30 of the intake valve 20 are movable members that are moved to drive the intake valve 20 to open the intake valve 20. The inlet valve 20 also has a magnet 31 with a magnetic coil 32. The magnet coil 32 is electrically connected to pins 35, 36 of a plug 37 via electrically conductive contact pins 33, 34. The plug 37 in this case allows the connection to a control unit 38. The control unit 38 is used in this embodiment as
Control 38. The controller 38 may also be integrated in a central control unit. The control unit 38 is connected to a rotation angle sensor 39, which detects the current rotation angle of the drive shaft 8 and outputs to the control unit 38. About the detected rotation angle is a direct relationship with the current position of the pump piston 5. Specifically, it can thus be detected whether the pump piston 5 is at a top dead center at which the pump piston undergoes a maximum stroke and the pump chamber 12 has a minimum volume. Accordingly, it can be detected whether the pump piston 5 is at a bottom dead center at which the pump piston 5 has a minimum stroke and the volume of
Pump work space 12 is maximum. By energizing the magnetic coil 32, a magnetic field is generated. This magnetic field originates from the magnet 31, whereby a reinforcement is made possible via the ferromagnetic locking screw 21. The magnetic circuit also passes through the valve member 22, the plunger armature 30 and optionally via other ferromagnetic elements back to the Closure screw 21. Here, a gap 40 is provided between the plunger armature 30 and the valve member 22. The gap 40 allows for a displaceability of the
Submersible anchor 30 and thus an adjustment of the valve stem 25 for actuating the inlet valve 20. On the other hand remains as a gap 40, at least one residual air gap to avoid a so-called magnetic adhesive effect of the plunger armature 30 on the valve member 22 in the actuated state. Specifically, it can be at power off the
Solenoid 32, the force of the valve spring 27 largely delay a closing of the inlet valve 20 initiate. The maximum size of the gap 40 is predetermined by the sum of a desired working air gap and the residual air gap. A setting of the residual air gap and the working air gap is made by a suitable choice of the
Valve element 28 and the shim 29 allows. Specifically, by the thickness of the shim 29, the desired working air gap can be specified. The thickness of the shim 29 thus indicates the stroke of the valve stem 25. With unchanged
Geometry in the region of the valve seat surface 26 can thereby change the opening cross section on the valve seat surface 26 and thus also the possible flow in the
Pump work space 12 can be adjusted with the seal seat open. As a result, an adaptation of the inlet valve 20 is possible with respect to the respective application.
By actuating the inlet valve 20, fuel can thus be conducted from the low-pressure chamber 16 into the pump working chamber 12. The actuation of the inlet valve 20 takes place here during a suction stroke of the pump piston 5. During the delivery stroke of the pump piston 5, the inlet valve 20 is preferably closed. As a result, high-pressure fuel is conveyed into a high-pressure line 42 via an outlet valve 41, which may be designed as a directional or check valve 41. The high-pressure line 42 is connected, for example, to a fuel distributor strip.
If the inlet valve 20 is opened at about the top dead center of the pump piston 5 and closed at the bottom dead center of the pump piston 5, then a
Full filling of the pump chamber 12 can be achieved. However, the inlet valve 20 can be controlled by the controller 38 regardless of the stroke or the current position of the pump piston 5 during the suction phase. In this way, a partial filling of the pump working chamber 12 can be realized. There are several options for this, which can also be combined if necessary.
One possibility is that the actuation time of the inlet valve 20 is reduced so that the inlet valve 20 is closed again before reaching the bottom dead center of the pump piston 5. Alternatively, the activation time can also be achieved by reaching the lower one Totally extended beyond. The inlet valve 20 is then after the
Closed to reach the bottom dead center of the pump piston 5, so that a portion of the fuel from the pump chamber 12 during the stroke of the pump piston 5 in the opposite direction through the inlet valve 20 is fed back. The other part of the fuel is then conveyed via the high pressure line 42. The total funded over the high pressure line 42 amount of fuel per pump stroke is thereby reduced.
It should be noted that in this case there is no control of the fuel to a tank or the like. In addition, in this way, if appropriate, a noise behavior can be improved by damping pressure pulsations. A vote is possible here on the throttles 14, 15.
Another way to achieve a partial filling is that the
Inlet valve is not opened immediately after reaching the top dead center of the pump piston 5. As a result, a certain idle stroke of the pump piston 5 is achieved, so that the total flowing into the pump chamber 12 via the opening cross section of the open sealing seat fuel is reduced. In this case, by one or more upstream of the inlet valve throttles 14, 15 or damping volumes can be in an advantageous manner
Pressure fluctuations in terms of amplitude and frequency and the volume control can be reduced. The chokes allow this a large partial reflection and a low attenuation of pressure and dilution waves. Damping volumes allow a lower partial reflection and a stronger damping of the pressure and
Dilution waves. This depends on the geometric design of the respective damping volume. By opening and closing of the inlet valve 20 or possibly a plurality of intake valves 20 designed in accordance with the intake valves, pressure and dilution waves are produced which flow from the intake valves to a
Feed pump, in particular an electric fuel pump run and reflected there. The reflected waves can inter alia during an opening process of the
Return inlet valve 20 again and thus additionally affect the filled mass in the pump working space, which can lead to fluctuations in delivery of the high-pressure pump. With the help of damping volumes and throttles 14, 15 in the inlet channel 13 and their vote these pressure waves can be reduced so far that a uniform delivery of the high-pressure pump 1 within a certain tolerance
is guaranteed. The design and dimensioning depends on the field of application of the high-pressure pump 1 and the connection to the prefeed pump. In an advantageous manner, an inlet valve 20 can thus be realized, which is closed in the de-energized state. This intake valve 20 is integrated in the cylinder head 2. In this case, the plunger anchor principle can be exploited, so that a quick opening and
Close the intake valve 20 can be achieved. Furthermore, the suction throttling can be moved into the working cylinder, in which an air outgassing is deliberately used. The required dynamics can be ensured by one or more connection holes. About a correspondingly high spring preload of the valve spring 27, a sufficiently high closing dynamics can be achieved. The cooling of the magnet 31 with the magnetic coil 32 can be achieved by the flushing of the fuel.
The invention is not limited to the described embodiments.