WO2009049971A1 - Injection system and method for operating an injection system - Google Patents

Abstract

The present invention relates to an injection system (50) for injecting fuel into a vehicle engine, comprising an injector arrangement (12) with at least one injector housing (28a, 28b, 28c) and at least one actuator (26a, 26b, 26c) arranged in each injector housing (28a, 28b, 28c) for opening and closing the at least one injector of the injector arrangement (12), a control device (14) for applying a voltage to the at least one actuator (26a, 26b, 26c), a first and a second line (34, 36) connecting the control device (14) to an anode connection (30a) and to a cathode connection (30b) of the at least one actuator (26a, 26b, 26c), as well as a connecting line (56) that connects the at least one injector housing (28a, 28b, 28c) to a ground (18) of the control device (14). The invention also relates to a method for operating such an injection system (50).

Description

 description

title

An injection system and method for operating an injection system

The invention relates to an injection system for injecting a fuel into a vehicle engine. Furthermore, the invention relates to a method for operating such an injection system.

State of the art

Frequently, a vehicle for injecting a fuel into its vehicle engine has an injector with an actuator. Such an injector is for example a common rail injector. By controlling the actuator in a piezoelectric actuator, for example by applying a defined voltage to the actuator, the length of the actuator can be changed. In this way, a closing element of the injector coupled to the actuator is displaced between its opening and closing position. This causes an opening or closing of the injector. Thus, a desired amount of fuel may be injected through the open injector into the vehicle engine.

The charging and discharging of the actuator usually takes place by means of an output stage of a control unit, by means of which a charging or discharging current is provided to the actuator. To illustrate this process, a conventional injection system with an injector and an output stage of a control device in Fig.l is shown schematically.

Fig.l shows a circuit diagram of an injection system for injecting a fuel into a vehicle engine according to the prior art. The schematically illustrated injection system 10 comprises an injector arrangement 12 with three injectors and an otherwise not shown control unit with an output stage 14.

The output stage 14 is supplied from a buffer capacitor 16 with an intermediate circuit voltage of, for example, 250 V. The negative pole of the buffer capacitor 16 is connected to a ground 18 of the output stage 14. The positive pole of the buffer capacitor 16 and the ground 18 are respectively connected to a first and a second input 19a and 19b of a half-bridge circuit. The half-bridge circuit includes the Insulated Gate Bipolar Transistor (IGBT) 20a and 20b and the diodes 22a and 22b. The IGBTs 20 a and 20 b are arranged on the side facing the buffer capacitor 16 side. In this case, the IGBT 20a is connected to the positive pole of the buffer capacitor 16 and the IGBT 20b to the ground 18. The diodes 22a and 22b are disposed on the output side facing the half-bridge circuit. The diode 22a is inserted in parallel with the IGBT 20b. Accordingly, the diode 22b is arranged in parallel to the IGBT 20a. In this case, the direction of flow of the diode 22a from the negative pole of the buffer capacitor 16 to the bridge branch 21 of the half-bridge circuit. The direction of flow of the diode 22b extends from the bridge branch 21 of the half-bridge circuit to the positive pole of the buffer capacitor 16.

Instead of the IGBT 20a and 20b, other power semiconductors which can be switched on and off can also be used as switching elements, such as, for example, MOSFET and / or bipolar power transistors.

The first output 23a is located at a contact point between the two diodes 22a and 22b and the bridge branch 21. At the output 23a, a throttle 24 is connected. The second output 23b is located at a contact point between the diode 22a, the IGBT 20b and the ground 18.

In the example of FIG. 1, the injector assembly 12 has three actuators 26a, 26b and 26c. The actuators 26a, 26b and 26c are each disposed within an injector housing 28a, 28b and 28c, of which in Fig.l, however, only partial walls are shown. An injector housing 28a, 28b and 28c may also include a special housing for its actuator 26a, 26b or 26c, which is arranged in its interior.

The actuators 26a, 26b and 26c represent essentially a capacitive load with the capacitance C for the output stage 14. All three actuators 26a, 26b and 26c are activated via the output stage 14. For this purpose, the anodes of the actuators 26a, 26b and 26c are provided with an anode

Terminal 30a of the injector 12 is connected. The cathodes of the actuators 26a, 26b and 26c are connected via the switches 32a, 32b and 32c to a common cathode terminal 30b.

In series with a cathode of each actuator 26a, 26b and 26c is thus in each case a switch 32a, 32b and 32c, for example a low-side switch attached. If an actuator 26a, 26b or 26c is to be activated during operation of the injector arrangement 12, then always the switch 32a, 32b or 32c associated with the actuator 26a, 26b or 26c to be controlled. The other switches 32a, 32b or 32c are locked during this time. For example, in a situation where the actuator 26b is driven, the switch 32b is closed. The switches 32a and 32c are opened in this case.

The common anode terminal 30 a of the injector 12 is connected via a line 34 to the throttle 24. Similarly, a line 36 connects the second output 23b of the half-bridge circuit to the cathode terminal 30b. In this way, if the associated switch 32a, 32b or 32c is closed, each actuator 26a, 26b or 26c connected to the ground 18 of the output stage 14.

The charge or discharge current provided by the output stage 14 is controlled via the half-bridge circuit. In order to increase the charging current, the IGBT 20a is turned on. If, on the other hand, the IGBT 20a is blocked, the current flow commutates to the diode 22a, which causes a reduction of the charging current. Accordingly, the IGBT 20b is turned on to increase the discharge current. A decrease in the discharge current takes place as soon as the IGBT 20b is blocked and the current flow commutates to the diode 22b. The throttle 24 serves as a smoothing reactor for smoothing the charging and discharging.

During an activation of an actuator 26a, 26b or 26c, its cathode is thus at ground potential, while the anode potential of the actuator 26a, 26b or 26c is raised or lowered rapidly. In this way, a length of the actuator 26 a, 26 b or 26 c can be varied, which causes opening or closing of the associated injector of the injector 12.

However, the actuators 26a, 26b and 26c of the injector 12 have not only an actuator capacity. When charging or discharging the actuator 26a, 26b or 26c, parasitic coupling capacitances between the anodes and cathodes of the actuators 26a, 26b or 26c and the associated injector housing 28a, 28b or 28c are additionally charged or discharged.

The injector housings 28a, 28b and 28c are connected to a ground potential via the engine block. Thus, when an actuator 26a, 26b or 26c is driven, not only its actuator capacitance but also its parasitic coupling capacitance is charged from its anode to the associated injector housing 28a, 28b or 28c. In addition, the parasitic coupling capacitances between the anodes and the cathodes of the adjacent actuators 26a, 26b or 26c and their injector housings 28a, 28b or 28c are also charged. For this In addition to the charging and discharging current, the charging current of the parasitic coupling capacitances also flows from the output stage 14 to the anodes of the injector arrangement 12. This is also referred to as parasitic charging currents.

However, the parasitic charging currents do not flow back to the negative pole of the buffer capacitor 16 via the cathodes of the actuators 26a, 26b and 26c and the line 36. Instead, the parasitic charging currents are returned to the control unit via a so-called parasitic current path. This (unspecified) parasitic current path includes the engine block with its earth straps, the vehicle body and the connection of the controller to the ground collection point.

The high-frequency pulsed parasitic charging currents flow around a relatively large area on the line 34 and the parasitic current path. This causes a significant electromagnetic interference radiation. This noise emission can lead to problems with the reception of electromagnetic signals by in-vehicle devices. For example, a reception of a car radio can be affected by the noise emission.

To solve this problem, the injection system 10 in addition to a throttle 38. The throttle 38 is a common-mode or common-mode throttle (CM throttle). It comprises two windings 40a and 40b on a common core. The two windings 40a and 40b usually have the same number of turns. The line 34 is guided over the first winding 40 a. Accordingly, the line 36 is guided over the second winding 40b.

Thus, the charging and discharging current and the parasitic charging current flow from the output stage 14 to the anode terminal 30a via the first winding 40a. The charging and discharging current also flows back from the cathode terminal 30b to the final stage 14 via the second winding 40b. Thus, the regular charge and discharge current flows equally across both windings 40a and 40b, and thus does not cause a magnetic field in the common core of the reactor 38. Therefore, the choke 38 has no effects on the desired charge and discharge current.

However, the parasitic parasitic currents do not flow back to the final stage 14 via the cathode terminal 30b and the line 36. Thus, the parasitic interference currents flow only via the first winding 40a of the throttle 38 from the output stage to the anode terminal 30a and therefore cause a flooding of the inductor 38. For the current path across the winding 40a of the inductor 38 and the parasitic coupling capacitances to the vehicle housing and from there back to the controller, therefore, the main inductance of the throttle 38 is effective. The Throttle 38 thus causes a limitation of the rate of rise of the parasitic parasitic currents. This leads to a reduction of the disturbance radiation.

However, even this reduced interference radiation can have a negative effect on the reception of electromagnetic signals by in-vehicle devices and / or permissible

Exceed limits. It is therefore desirable to have an additional possibility of further reducing the noise emission.

Disclosure of the invention

The invention provides an injection system with the features of claim 1 and a method for operating such an injection system with the features of claim 9.

The present invention is based on the finding that by means of a connection of the injector housing to the ground of the control device, the parasitic currents are at least partially discharged via the connection. As a result, those parasitic currents which flow off via the parasitic current path described above are reduced. Since the connection of the injector housing formed by means of the connection line to the mass of the control device encloses a smaller area than the parasitic current path, the interference radiation generated by the outflowing parasitic charging currents can be significantly reduced in this way.

For example, the at least one injector housing, which is connected via the connecting line to the ground of the control unit, comprises at least one actuator housing of the at least one actuator. The connection of the injector to the ground of the controller is thus chosen so that a flow of parasitic charging currents through the connection is well possible.

In a preferred embodiment, the first line, the second line and the connecting line are guided together in a cable harness. In this way, the area enclosed by the lines can be minimized. This also contributes to reducing the noise emission.

The control device preferably comprises an output stage with a buffer capacitor for providing the voltage applied to the at least one actuator. The mass of the Control unit is then arranged in the power amplifier. In this way, a relatively high proportion of the parasitic interference currents can flow to the negative pole of the buffer capacitor.

Advantageously, the first line extends via a first winding and the second line via a second winding of a common-mode or common-mode throttle (CM throttle). The guiding of the first and the second line via the choke causes a limitation of the rate of rise of the parasitic interference currents, which additionally reduces the interference radiation generated by the parasitic interference currents.

In an advantageous development of the invention, the connecting line runs over a third winding of the common mode or CM choke. In this way, it can be ensured that an increased proportion of the parasitic interference currents flows via the connection line and not via the parasitic current path to the ground of the control unit. Thus, the parasitic charging currents are dissipated to a much greater extent over the desired current path. At most a negligible proportion of these currents still flows in this case via the parasitic current path. In this way, the noise emission is reduced significantly to the same extent.

The first, the second and the third winding may have the same number of turns. In a preferred development, however, the first and the second winding have a first number of turns and the third winding has a second number of turns different from the first number of turns. In this way, the interaction of the windings can be controlled such that the highest possible proportion of the parasitic charging currents flows via the connecting line and only the smallest possible proportion of the parasitic charging currents flows via the parasitic current path.

As a supplement or as an alternative thereto, a first distance between the first and the second winding may also deviate from a second distance between the second and the third winding. This offers a further possibility for controlling the interaction of the windings mounted on a common core in such a way that the noise radiation generated due to the parasitic charging currents flowing away via the parasitic current path is reduced.

The advantages described in the above sections also apply to a corresponding procedure.

Brief description of the drawings Further features and advantages of the present invention will be explained below with reference to the figures. Show it:

Fig.l a circuit diagram of an injection system for injecting a fuel into a vehicle engine according to the prior art;

2 shows a circuit diagram of a first embodiment of the invention

Injection system; and

3 shows a circuit diagram of a second embodiment of the invention

Injection system.

Embodiment of the invention

2 shows a circuit diagram of a first embodiment of the injection system according to the invention. The injection system 44 shown has the already described components 12 to 36 of the injection system 10 of FIG. A repeated description of these components 12 to 36 is omitted here.

However, the injection system 44 additionally has a connecting line 46, which connects the injector housings 28a, 28b and 28c to the line 36 and thus to the output 23b of the output stage 14. Preferably, the connection line 46 is guided with the lines 34 and 36 in a common wiring harness. The routing of the lines 34, 36 and 46 in the harness is done in a meaningful way spatially very close. For example, the lines 34, 36 and 46 can be summarized in the wiring harness or twisted together. In this way, the lines 34, 36 and 46 span a negligible area.

Advantageously, in the injection system 44, the parasitic charging currents not only via the parasitic current path, which runs over the engine block, the grounding strap, the body, the ground-collecting point and the control unit, but also flow via the connecting line 46. The area enclosed by the lead 46 and the lead 34 is relatively small compared to the area defined by the parasitic current path and the lead 34. A drainage of the parasitic charging currents via the connecting line 46 therefore hardly generates a noise emission. The connecting line 46 thus provides a new desired current path to drain the parasitic charging currents.

3 shows a circuit diagram of a second embodiment of the injection system according to the invention. The illustrated injection system 50 also has the already described components 12 to 36 of the injection system 10 of FIG. 1.

In contrast to the conventional injection system 10, however, the injection system 50 according to the invention is equipped with a three-coil throttle 52 instead of the two-coil throttle 38. The points represent the winding sense of the windings 54a to 54c of the throttle 52 again. The conduit 34, which connects the throttle 24 to the anode terminal 30a, passes over the first winding 54a. The line connecting the cathode terminal 30b to the ground 18 of the output stage 14 extends over the second winding 54b.

In addition, the injection system 50 according to the invention has a connection line 56, which connects each injector housing 28a, 28b and 28c to the output 23b of the output stage 14. The terminals of all the injector housings 28a, 28b and 28c are interconnected at a collection point. This collection point is connected via the output 23b to the negative terminal of the buffer capacitor 16 and to the ground 18. The connecting line 56 is connected to the lines 34 and 36 in a common, not shown harness. This ensures the advantages already described for the injection system 44.

The third winding 54c has the same winding sense as the second winding 54b, over which the line 36 extends, which connects the cathode terminal 30b to the negative terminal of the buffer capacitor 16 and the mass 18 connects.

A parasitic charging current, which flows via the first winding 54a from the output stage 14 to the anode terminal 30a and flows back via the third winding 54c from the cathode terminal 30b to the output stage 14, thus causes no magnetic field in the core of the choke 52 in contrast to a parasitic charging current, which flows back via the engine block and body to the mass 18 back. Therefore, in the injection system 50, a relatively high proportion of the parasitic charging currents flow back to the final stage 14 via the desired current path, the connecting line 56. Only a significantly reduced proportion of the parasitic charging currents flows through the parasitic current path. This causes a significant reduction in the noise emission. The provision of the injection system 50 with the three-coil throttle 52 instead of a two-coil throttle 38 does not significantly increase the manufacturing cost of the injection system 50. The injection system 50 thus represents a cost-effective solution for reducing the noise emission. Likewise, the three-coil choke 52 requires hardly any more building space.

In order to further reduce the gradients of the parasitic charging currents flowing over the desired current path, the choke 52 can be designed in such a way that the current flow via its third winding 54c leads specifically to the formation of a small stray flux which causes the other windings 54a and 54b 54b of the throttle 52 does not surround. As a result, a slightly higher stray inductance acts on the desired current path than in the current path for the regular charging and discharging current of the actuators 26a, 26b and 26c. Since this stray inductance is substantially lower than the main inductance of the inductor 52, a high proportion of the parasitic charging currents will continue to flow over the desired current path.

For example, the third winding 54c may have a different winding number than the first and second windings 54a and 54b. Accordingly, a geometric distance between the windings 54a and 54b and the windings 54b and 54c can be varied.

In a development, the housing connection of the injectors to the control unit in the wiring harness can be configured as a screen around the previous injector connection lines. In this way, the noise radiation, which is emitted by a flow of the parasitic charging current on the desired current path, can be further reduced.

The present invention has been described in FIGS. 2 and 3 using the example of an injector with three actuators 26a, 26b and 26c. However, it is not limited to this example.

Claims

claims An injection system (44, 50) for injecting a fuel in a vehicle engine with an injector assembly (12) having at least one injector housing (28a, 28b, 28c) and at least one actuator disposed in each injector housing (28a, 28b, 28c) (26a, 26b, 26c) for opening and closing the at least one injector of the injector assembly (12); a controller (14) for applying a voltage to the at least one actuator (26a, 26b, 26c); - A first and a second line (34,36) connecting the controller (14) with an anode terminal (30a) and with a cathode terminal (30b) of the at least one actuator (26a, 26b, 26c); and a connecting line (46, 56) which connects the at least one injector housing (28a, 28b, 28c) to a mass (18) of the control unit (14). 2. Injection system (44,50) according to claim 1, wherein the at least one injector housing (28a, 28b, 28c) which is connected via the connecting line (46,56) to the ground (18) of the control unit (14), at least one actuator housing of the at least one actuator (26a, 26b, 26c) comprises. 3. Injection system (44,50) according to claim 1 or 2, wherein the first line (34), the second line (36) and the connecting line (46,56) are guided together in a wire harness. 4. Injection system (44,50) according to any one of the preceding claims, wherein the Control unit (14) comprises an output stage (14) with a buffer capacitor (16) for providing the voltage applied to the at least one actuator (26a, 26b, 26c). 5. Injection system (44,50) according to one of the preceding claims, wherein the first line (34) via a first winding (54a) and the second line (36) via a second winding (54b) of a common mode or common Mode throttle (CM throttle) (52) runs. 6. Injection system (50) according to claim 5, wherein the connecting line (56) via a third winding (54c) of the common mode or CM choke (52) extends. 7. Injection system (50) according to claim 6, wherein the first, the second and the third winding (54 a, 54 b, 54 c) have the same number of turns. 8. Injection system (50) according to claim 6, wherein the first and the second winding (54 a, 54 b) have a first number of turns and the third winding (54 c) has a second number of turns different from the first number of turns. 9. Injection system (50) according to any one of claims 6 to 8, wherein a first distance between the first and the second winding (54 a, 54 b) deviates from a second distance between the second and the third winding (54 b, 54 c). 10. A method for operating an injection system (44, 50) for injecting a fuel in a vehicle engine with an injector arrangement (12) with at least one injector housing (28a, 28b, 28c) and with at least one in each injector housing (28a, 28b, 28c) arranged actuator (26a, 26b, 26c) for opening and closing the at least one injector of the injector assembly (12), with a control unit (14) for applying a voltage to the at least one actuator (26a, 26b, 26c); and a first and a second line (34, 36) connecting the controller (14) to an anode terminal (30a) and to a cathode terminal (30b) of the actuator (26a, 26b, 26c) Step: Connecting the at least one injector housing (28a, 28b, 28c) to a mass (18) of the control device (14).