Control module for a storage-type injection system injector

A control module (1) for an injector designed to control and guide a valve body (8) comprises a high-pressure supply element (2), a guiding device (3) for guiding the valve body, a control compartment (4), a control valve (10), a supply choke (5), first and second output chokes (6, 7). The supply choke physically represents a connection between the high pressure supply element (2) and a valve compartment (9). The first output choke (6) connects the control compartment linked to one end of the valve body, to the valve compartment (9). The second output choke (7) connects the valve compartment (9) to the control valve (10).

TECHNICAL FIELD OF THE INVENTION

The invention relates to a control module for a storage-type injection system injector to control and simultaneously guide an injector valve body.

DESCRIPTION OF THE RELATED ART

Different embodiments of injectors for storage-type injection systems are known. One such known injector is shown inFIG. 4for example. Here fuel is supplied to the area around the nozzle needle36via a high-pressure supply line30. The nozzle needle36is in contact with a control piston31, one end of which is arranged in a control compartment32. The pressure in the control compartment32can be controlled in the known manner by means of a control valve33, so that the control compartment32can be connected to a tank T. The side of the control piston31opposite the control compartment32is in contact with a low-pressure compartment34, which is connected via a low-pressure output element35to the tank T. This allows the nozzle needle36to be raised from its seat in the known manner, resulting in injection. However this causes a major drop in pressure in the control compartment33, which can result in cavitation problems and longer closure times due to gas bubbles.

With the injector design shown inFIG. 4continuous leakage occurs both in the nozzle needle guide37and in the guide38for the control piston31, as the compartments subject to high pressure are connected to the low-pressure compartment34via sealed gaps. A quantity of fuel therefore flows from the high-pressure area via the two guides37and38to the low-pressure compartment34. However this continuous leakage causes an efficiency loss that cannot be ignored.

Injectors are also known from the prior art, which have a bypass, to allow a direct connection between the high-pressure supply line and the control valve. This allows faster switching times to be achieved. However during injection there is both a connection from the high-pressure line via the bypass to the low-pressure area and from the high-pressure line via the supply choke and the control compartment to the low-pressure area. This means that losses during injection are not insignificant. Unwanted continuous leakage also occurs via the control piston with this system.

SUMMARY OF THE INVENTION

The object of the present invention is therefore to provide a control module without continuous leakage or an injector without continuous leakage for storage-type injection systems, which has a simple structure and is simple and economical to produce.

This object can be achieved by a control module for a storage-type injection system injector to control and guide a valve body, comprising a high-pressure supply element to supply fuel, a guiding device to guide the valve body, a control compartment, a control valve, a valve compartment, a supply choke, a first output choke and a second output choke, whereby the supply choke provides a connection between the high-pressure supply element and the valve compartment, the first output choke provides a connection between the control compartment, which is connected to one end of the valve body, and the valve compartment, and the second output choke connects the valve compartment to the control valve. The object can also be achieved by an injector for a storage-type injection system with such a control module.

The high-pressure supply element can be connected to the supply choke via an annular channel. The annular channel can be configured in a nozzle body and/or in the control module. The guiding device can be configured as a cylindrical extension. A connecting area can be provided on the outer periphery of the guiding device and/or on the inner periphery of the nozzle body to connect the high pressure supply element to a high-pressure area on the valve body. The connecting area can be formed by one or a plurality of recesses on the guiding device and/or on the nozzle body. The guiding device may have a recess to guide the valve body. A spring element to reset the valve body can be supported on the one hand on the guiding device and on the other hand on a spring plate arranged on the valve body. Centering surfaces can be configured on the guiding device to center the control module in the nozzle body. The valve body can be configured as a nozzle needle. In the control module all the functional elements to control and guide the valve body of the injector can be combined in one component. The high-pressure supply element can be connected to the supply choke via an annular channel, which is preferably configured in a nozzle body and/or in the control module. The valve compartment can be formed by a lateral hole in the control module. The valve body can be configured as a single nozzle needle, one end of which is connected to the control compartment and the other end of which releases or closes injection openings.

The inventive control module for a storage-type injection system injector provides for an injector without continuous leakage, in that all the functional elements to control and guide the valve body of the injector are combined in one component. This means there is a minimum number of high-pressure sealed surfaces. The high-pressure sealed surfaces are thereby only configured as planes, which can be sealed relatively easily. There is therefore no need for the cylindrical guide surfaces used in the prior art, which are subject to continuous leakage due to the gap there. Also according to the invention there is no need for the provision of a bypass, without any disadvantages in respect of switching times. This can be achieved, as according to the invention optimum design is possible for the choke cross-sections of the different chokes of the control module. The inventive control module thereby comprises a high-pressure supply element to supply fuel, a guiding device to guide the valve body of the injector, a control compartment, a control valve and a valve compartment. A supply choke and a first and second output choke are also provided. The control compartment, which is connected to one end of the valve body, is thereby only connected to the valve compartment via a first output choke. The supply choke also connects the high-pressure supply line to the valve compartment. A second output choke goes out from the valve compartment to the control valve. Unlike the prior art there is no direct connection between the control compartment and the high-pressure supply line. The control compartment is only connected to the high-pressure line via the first output choke and the valve compartment and supply choke. Therefore when the control valve is opened, fluid flows out of the control compartment via the first output choke and when the control valve is closed, the control compartment is filled again through the first output choke, whereby the flow direction in the first output choke reverses. The inventive use of an additional valve compartment also means that the pressure level in the control compartment is higher when the control valve is opened. This means there is no longer a risk of cavitation bubbles forming, which in the prior art result in both damage to the components and delays in closing the nozzle needle. The volume flow flowing out through the control valve when the nozzle needle opens is also smaller, with the result that the control cross-section required at the control valve to prevent choking effects at the control valve is reduced. Also when the injector is open, there is only switching leakage due to the volume flow through the supply choke, the valve compartment and the control valve to the low-pressure area. Also according to the invention a larger design margin can be maintained for the individual choke cross-sections, to be able to satisfy the requirements in respect of the smallest representable injection quantity from the injection nozzle into the combustion chamber and the minimum nozzle opening pressure. This means that for a predefined, maximum permissible volume flow at the control valve seat the choke cross-sections can be larger than in the prior art. This reduces sensitivity in respect of manufacturing tolerances, so manufacturing costs can be reduced.

In order for it to be possible to produce the inventive control valve in a particularly favorable manner, the high-pressure supply element is preferably connected to the supply choke via an annular channel. The annular channel is thereby particularly preferably configured in a nozzle body (injector housing) and/or in the control module.

According to one preferred embodiment of the present invention the guiding device is configured as a cylindrical extension to the control module. The valve body of the injector is thereby preferably guided in a hole in the guiding device and the control compartment is arranged at the end of the hole preferably in the form of graduated hole.

In order to provide a particularly compact control module structure or a particularly compact injector, a connecting area is preferably provided on the outer periphery of the guiding device or on the inner periphery of the nozzle body. This connecting area connects the high-pressure supply element to a high-pressure area on the valve body of the injector, in order to supply fuel for an injection.

In order to allow particularly simple and economical production, the connecting area is thereby preferably formed by one or a plurality of recesses on the guiding device and/or on the nozzle body. The connecting area can thereby be produced particularly easily by grinding areas on the periphery of the cylindrical guiding device.

The guiding device preferably has a recess to guide the valve body. It is particularly preferable for said recess to be configured as a blind hole in the cylindrical guiding device.

According to a further preferred embodiment of the present invention, a nozzle spring for resetting the valve body is supported on the one hand on the guiding device and on the other hand on a spring plate arranged on the valve body.

In order to maintain a high degree of accuracy of the movement of the valve body during the fuel injection process, one or a plurality of centering surfaces are preferably configured on the guiding device to center the control module in the nozzle body.

It is particularly preferably here for the valve body of the injector to be configured as a nozzle needle.

The inventive control module for an injector is preferably used in storage-type injection systems such as common rail injectors for diesel engines. As the inventive control module combines all the necessary elements for controlling and guiding the valve body in one component, the injector can be particularly compact and economical to produce. Continuous leakage can be prevented, as there is only one flat sealed surface between the control module and the adjacent further components of the injector and this is relatively easy to seal. This can also significantly simplify functional testing of the component, as elaborate assembly of a plurality of components is not necessary. Also pressure loss and the volume of the control compartment can be kept to a low value, so that very short control times are possible with the inventive injector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An exemplary embodiment according to the present invention is described below with reference toFIGS. 1 to 3.

As shown in particular inFIG. 1, the inventive control module1for a storage-type injection system injector is very compact in structure. The control module1comprises a high-pressure supply element2, to supply fuel from a high-pressure pump (not shown) to the injector. The control module1also comprises a cylindrical guiding device3for guiding a valve body8of the injector. A blind hole21is configured in the cylindrical guiding device3for this purpose.

The control module1also comprises a control compartment4, a valve compartment9and a control valve10. The control compartment4is connected, as shown inFIG. 1, to one end of the valve body8. The control compartment4is also connected via a first output choke6to the valve compartment9. The valve compartment9is in turn connected via a second output choke7to the control valve10. The high-pressure supply line2is connected via an annular channel14via a supply choke5to the valve compartment9.

As shown in particular inFIG. 3, the valve compartment9is formed by a lateral hole in the control module1, which is sealed in a fluid-tight manner by means of a grub screw13.

The inventive arrangement of the supply and output chokes5,6,7means that the control compartment4can have a minimum volume, which has an advantageous effect on the achievement of minimum switching times for opening and closing the valve body.

The connecting area15between the high-pressure supply line2and a high-pressure area22on the valve body8is also shown inFIGS. 2 and 3. As shown inFIG. 2, the connecting area15comprises four flattened areas on the outer periphery of the cylindrical guiding device3. Centering surfaces16(only one is shown inFIG. 3) are configured between the individual connecting areas15to allow reliable centering of the control module1in the nozzle body17.

As also shown inFIG. 1, a spring18is provided to reset the valve body8, and said spring is supported on the one hand on the annular end of the guiding device3and on the other hand on a spring plate19attached to the valve body8.

The function of the inventive injector is as follows: when the control valve10is activated by an actuator, such as a piezoactuator for example, so that a control valve element11of the control valve10is raised from a valve seat12, the valve compartment9is connected via the second output choke7to a low-pressure area downstream from the control valve. The pressure in the valve compartment9therefore drops. As a result fluid flows out of the control compartment4via the first output choke6and the valve compartment9into the low-pressure area. The pressure in the control compartment4therefore drops so that the valve body8is moved upwards towards the control module1counter to the spring force of the spring18, so that the injection openings20are released and the injection of fuel into a combustion chamber is facilitated. While the control valve10is in the opened state, only a volume restricted by the supply choke5can flow from the high-pressure supply element2via the annular channel14, the supply choke5, the valve compartment9and the second output choke7to the low-pressure area. The inventive embodiment of the control module also prevents continuous leakage, as the inventive control module has no further connections to the low-pressure area. The inventive control module has only one flat sealed surface D on the control module1between the high-pressure supply element2and the low-pressure area.

When injection is to be terminated, the control valve10is closed again via the actuator, so that the original pressure can build up again in the valve compartment9. The control compartment4is thereby filled again from the valve compartment9via the first output choke6. The flow direction in the first output choke6thereby reverses. The original pressure therefore builds up again in the control compartment4, so that the valve body8moves downwards into its original position and the injection openings20close again and injection is terminated.

As the pressure level in the control compartment4is higher with the control valve10open than with the prior art, fast closure of the injector can be achieved. The higher pressure means that cavitation bubbles do not form at the first output choke6or at the control compartment4.

The inventive injector thereby requires a minimum volume to open or close the valve body8, resulting in a larger design margin for the choke cross-sections of the two output chokes6and7and the supply choke5. In particular for a predefined maximum permissible volume flow at the valve seat12the choke cross-sections can be larger, thereby significantly reducing manufacturing costs. The inventive control module thereby has a particularly compact structure, as a plurality of functions can be provided simultaneously by the control module1.

As shown inFIG. 1, the valve body8is configured as a single nozzle needle, one end of which is connected to the control compartment4and the other end of which releases or closes injection openings20.

Because of the minimal volume of the control compartment4it is also possible with the invention for the smallest quantities of fuel to be injected with a very high degree of accuracy, as the valve body8can be positioned very accurately as a result.

The present invention therefore relates to a control module1for a storage-type injection system injector to control and guide a valve body8, comprising a high-pressure supply element2to supply fuel, a guiding device3to guide the valve body8and a control compartment4. A control valve10, a supply choke5, a first output choke6and a second output choke7are also provided. The supply choke5provides a connection between the high-pressure supply element2and a valve compartment9. The first output choke6connects the control compartment4, which is connected to one end of the valve body18, to the valve compartment9. The second output choke7connects the valve compartment9to the control valve10.

The present invention is not restricted to the exemplary embodiment shown. Various differences and modifications can be implemented without leaving the scope of the invention.