SHEATHED-ELEMENT GLOW PLUG UNIT AND SYSTEM FOR OPERATING A PLURALITY OF SHEATHED-ELEMENT GLOW PLUGS

Abstract

A sheathed-element glow plug unit includes an input for connecting the sheathed-element glow plug unit to a control line, via which a sheathed-element glow plug of the sheathed-element glow plug unit is able to be controlled. The sheathed-element glow plug unit has an output, via which at least one further sheathed-element glow plug unit is able to be connected to the control line.

Description

FIELD OF THE INVENTION

The present invention relates to a sheathed-element glow plug unit having an input for connecting the sheathed-element glow plug unit to a control line, via which a sheathed-element glow plug of the sheathed-element glow plug unit is able to be controlled.

Furthermore, the present invention relates to a system for operating a plurality of sheathed-element glow plugs, including a central glow control device and at least two sheathed-element glow plug units having one sheathed-element glow plug in each case.

In addition, the present invention also relates to a method for operating a plurality of sheathed-element glow plug units, each sheathed-element glow-plug unit having one sheathed-element glow plug, and a central glow control device is provided for controlling the sheathed-element glow plug units.

BACKGROUND INFORMATION

Conventional sheathed-element glow plug units and corresponding systems require at least one electrical line for each sheathed-element glow plug for the supply of the individual sheathed-element glow plug, so that, in particular in the case of applications with a multitude of sheathed-element glow plugs, considerable wiring is required to connect a central glow control device to the various sheathed-element glow plugs.

Another disadvantage of conventional devices is that the central glow control device requires a large number of plug pins and correspondingly complex and. expensive plug connectors in order to enable a connection to each individual sheathed-element glow plug or sheathed-element glow plug unit.

SUMMARY

Example embodiments of the present invention provide a sheathed-element glow plug unit of the type mentioned in the introduction, and a corresponding system as well as an operating method such that the required wiring expenditure is low yet the functionality is not reduced in comparison to conventional systems.

According to example embodiments of the present invention, a sheathed-element glow plug unit of the type mentioned in the introduction includes an output, via which at least one additional sheathed-element glow plug unit is able to be connected to the control line.

In contrast to conventional systems, the arrangement of the sheathed-element glow plug unit according to example embodiments of the present invention, having an input and an output, allows a serial connection of a plurality of sheathed-element glow plug units and thus a lower wiring outlay than, for instance, in the case of sheathed-element glow plug units disposed about a central glow control unit in a star-shaped topology. This reduces the number of plug pins on the glow control unit.

Additional features and details of example embodiments of the present invention result from the following description, in which an exemplary embodiment of the present invention is explained in detail with reference to the drawing. In this context, the features mentioned may be provided alone or in any combination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a system according to an example embodiment of the present invention;

FIG. 2 is a block diagram of a sheathed-element glow plug unit according to an example embodiment of the present invention;

FIG. 3a illustrates a position-evaluation unit according to an example embodiment of the present invention;

FIG. 3b illustrates a position-evaluation unit according to an example embodiment of the present invention;

FIG. 4 illustrates an additional example embodiment of the present invention; and

FIG. 5 is a flow chart of a method according to an example embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 shows a simplified block diagram of a system 100 according to an example embodiment of the present invention, which includes a central glow control device 110 as well as a plurality of sheathed-element glow plug units 120a, 120b. System 100 is used, for example, in motor vehicles having self-igniting internal combustion engines in order to preheat the combustion chambers of various cylinders of the internal combustion engine with the aid of sheathed-element glow plugs provided in individual sheathed-element glow plug units 120a, 120b.

According to example embodiments of the present invention, only the first of the plurality of sheathed-element glow plug units 120a, 120b is directly connected to central glow control device 110. As can be gathered from FIG. 1, additional sheathed-element glow plug units 120b, . . . are connected in series to first sheathed-element glow plug unit 120a. This reduces the wiring expenditure in the region of central glow control device 110 in system 100. Furthermore, central glow control device 110 requires only a single plug pin to connect a multitude of sheathed-element glow plug units 120a, 120b, etc.

Since the individual sheathed-element glow plug units 120a, 120b assigned to adjacent cylinders of an internal combustion engine are usually situated in close proximity to each other on account of the design of the internal combustion engine, the ohmic power losses in the additional sections 110b, 110c of control line 110, each of which, by itself, is considerably shorter than a connection line between central glow control device 110 and a sheathed-element glow plug unit of the conventional type, are lower than in line connections of conventional systems.

FIG. 2 shows a block diagram of a sheathed-element glow plug 120 according to an example embodiment of the present invention. Sheathed-element glow plug units 120a, 120b, for example, which are shown in FIG. 1, also have the same configuration.

As can be gathered from FIG. 2, sheathed-element glow plug unit 120 has an input 10 and an output 20. Via input 10, sheathed-element glow plug unit 120 is able to be directly connected to control line 110a, for example, which originates from central glow control device 110, while output 20 of sheathed-element glow plug unit 120 is connected to an input 10 of an additional sheathed-element glow plug unit 120, for instance via an additional section 110b (FIG. 1) of control line 110a, 110b, 110c.

Via an electrical connection of input 10 to output 20 within first sheathed-element glow plug unit 120a, control line 110a, which is connected to input 10 of first sheathed-element glow plug unit 120a (FIG. 1), is able to be connected through to first sheathed-element glow plug unit 120a and can thereby be made available to following sheathed-element glow plug units 120b, . . . . The connection of input 10 to output 20 may be implemented by, for instance, corresponding switches, which are preferably embodied as low-impedance semiconductor switches. In the same manner, additional sheathed-element glow plug units 120b, . . . are able to determine whether control line 110b, 110c, . . . is connected through to a following sheathed-element glow plug unit, which allows a corresponding forwarding of control signals that, for example, are transmitted from central glow control device 110.

To coordinate local control processes such as the connection of an input 10 to an output 20, and to implement diagnostic sequences and the like, sheathed-element glow plug unit 120 (FIG. 2) has a local control unit 40, which is preferably embodied as microcontroller or as application-specific, integrated circuit, ASIC.

Local control unit 40 is also used to evaluate control signals which central glow control device 110 outputs to sheathed-element glow plug units 120a, 120b, . . . via control line 110a, 110b, 110c.

To receive such control signals, sheathed-element glow plug unit 120 has a communications unit, which, for instance, evaluates a voltage level between control line 110a, 110b, 110c and a reference potential, such as the ground potential, by which corresponding address signals and control signals from central glow control unit 110 are encoded. In the same manner, i.e. by ground sampling, the communications unit of sheathed-element glow plug unit 120 is also able to generate signals and transmit them via control line 110a, 110b, 110c.

For sheathed-element glow plug unit 120 to know its address code, it must be able to detect its position within a series connection of a plurality of sheathed-element glow plug units 120a, 120b, . . . (FIG. 1). To this end, it is equipped with a position-evaluation unit, which is denoted by reference numeral 30 in the block diagram according to FIG. 2.

Position-evaluation unit 30 has at least one resistive and/or inductive component, which is switchable between input 10 and output 20 during the position detection process. This results in a voltage-divider system between input 10 of first sheathed-element glow plug unit 120a and the output of the last sheathed-element glow plug unit, which is preferably connected to the ground potential during the position determination, the voltage-divider system being made up of the series connection of the resistive and inductive elements of the individual sheathed-element glow plug units 120.

When an ohmic resistor is used as resistive element, this will therefore result in a simple ohmic voltage divider, and if all ohmic resistors are selected to have the same resistance value, then it is easily possible to infer the position of the particular sheathed-element glow plug unit 120 within the series connection by determining the voltage between input 10 and/or output 20 and the ground potential by applying the voltage-divider rule.

FIG. 3a shows a position-evaluation unit 30 by way of example; it has an ohmic resistor R, which is switchable between input 10 and output 20 of sheathed-element glow plug unit 120 (FIG. 2) with the aid of switches 15a, 15b. In the example embodiment shown, device V for a voltage measurement is provided as well, which measures a potential difference between the connection terminal of ohmic resistor R, shown on the left in FIG. 3a, and a ground potential. After the position detection has been concluded, switches 15a, 15b are opened and assume the state shown in FIG. 3a. Switches 15a, 15b may advantageously be embodied as semiconductor switches, in particular as field-effect transistors.

In example embodiments of the present invention, instead of ohmic resistor R and switches 15a, 15b, it is also possible to provide only a single semiconductor switch in position-evaluation unit 30. In this case the semiconductor switch is preferably arranged as field-effect transistor and, by appropriate controlling at its gate electrode, for instance, allows the simulation of ohmic resistor R additionally provided in the exemplary embodiment according to FIG. 3a, by its own drain-source resistance, which comes about between its drain electrode and its source electrode. That is to say, in this case the field-effect transistor simultaneously realizes the functionality of switches 15a, 15b (FIG. 3a) to connect input 10 to output 20, and the functionality of the serial resistor required for the position detection. The voltage measurement may be implemented analogously to the exemplary embodiment shown in FIG. 3a.

FIG. 3b shows a position-evaluation unit 30 according to an example embodiment of the present invention, which includes an inductive element L, such as a coil having a specifiable inductivity. Analogously to the above description, this produces an inductive voltage divider within the series connection of sheathed-element glow plug units 120a, 120b, . . . (FIG. 1).

When central glow control device 110 applies a jump-type control signal to control line 110, the position of the corresponding sheathed-element glow plug unit 120 may be inferred based on the individual rise time of the voltage dropping across a coil L, since—depending on the position of sheathed-element glow plug unit 120—a different resulting inductivity that influences the rise time is active on account of the series connection of the coils. The voltage across coil L may then be implemented locally using the already described means V for a voltage measurement, while appropriate monitoring of the rise time is preferably carried out by local control unit 40.

Another position-evaluation unit 30 according to an example embodiment of the present invention provides a capacitive element instead of inductive element L, which allows a position determination analogously to the afore-described method, and is able to be realized even more easily and in a more cost-effective manner than inductive element L.

Following successful position determination, each sheathed-element glow plug unit 120a, 120b, . . . has appropriate information and stores it, preferably in a non-volatile memory, such as an EEPROM memory integrated in local control unit 40, for example. The control of switches 15a, 15b (FIG. 3a) is preferably also implemented by local control unit 40.

FIG. 4 shows a module 50, which is likewise included in sheathed-element glow plug unit 120 and has a sheathed-element glow plug 51. As can be gathered from FIG. 4, a grounded connection 51b of sheathed-element glow plug 51 is permanently connected to the ground potential, and an operating-voltage connection 51a of sheathed-element glow plug 51 is connectable to input 10 via switch 16. For example, operating-voltage connection 51a of sheathed-element glow plug 51 is connected to input 10 via switch 16 whenever sheathed-element glow plug 51 is to be triggered. In this case, central glow control device 110 supplies sheathed-element glow plug 51 with electrical energy via input 10 and corresponding control lines 110a, 110b, . . . . I.e., instead of the control signals otherwise exchanged via control lines 110a, 110b, . . . , central glow control device 110 must then also supply an electrical output of sufficient size in order to ensure an adequate energy supply of sheathed-element glow plug 51.

Sheathed-element glow plug units that are possibly situated upstream from the viewed sheathed-element glow plug unit in a series connection must configure their modules 50 accordingly in this case, such that their switch 16 connects input 10 directly to output 20, so that the electrical energy will be conveyed to sheathed-element glow plug 51 to be triggered.

That is to say, in the case of a sheathed-element glow plug unit whose sheathed-element glow plug 51 is not to be triggered at the present time, switch 16 connects input 10 to output 20.

A diagnosis of the operation of sheathed-element glow plug 51 is possible by device V, shown in FIG. 4, for a voltage measurement. To this end, device V could record a voltage characteristic coming about at sheathed-element glow plug 51, for instance under the control of local control unit 40; in the event of a deviation from typical voltage values or voltage characteristics, a diagnosis report may possibly be transmitted from affected sheathed-element glow plug unit 120 to central glow control device 110.

This makes it possible, for instance, to realize a short-circuit detection, which infers a short circuit in the region of sheathed-element glow plug 51 if a voltage applied to sheathed-element glow plug 51 is undershot during triggering of sheathed-element glow plug 51. Aging of sheathed-element glow plug 51 is also detectable, by a change in the voltage characteristic coming about in the triggering of sheathed-element glow plug 51.

Device V for a voltage measurement shown in FIG. 4 may involve the same device shown in FIG. 3a as well. In this case measuring device V may be directly and permanently connected to input 10 and activated either for position detection or for diagnostic purposes in an operation of sheathed-element glow plug 51 (FIG. 4).

Device V for a voltage measurement may also be directly integrated in local control unit 40, for instance in the form of at least one analog-to-digital converter channel of a local control unit 40 embodied as microcontroller.

The control of an electric power supplied to sheathed-element glow plug 51 may, for one, be implemented by central glow control device 110 via the selection of the voltage applied to control line 110a, 110b, . . . or, on the other, is able to be coordinated locally in a sheathed-element glow plug unit 120, for instance by local control unit 40. In a local control, local control unit 40 is able to open and close switch 16 according to a specified pattern, for instance, in order to thereby enable a pulse-width-modulated triggering of sheathed-element glow plug 51.

Instead of the configuration of module 50 illustrated in FIG. 4, for the purpose of triggering one sheathed-element glow plug 51 it is also possible to connect input 10 (FIG. 2) to output 20 in all sheathed-element glow plug units 120, and to optionally connect operating-voltage connection 51a of corresponding sheathed-element glow plug 51 to input 10 or output 20, or disconnect it therefrom, by a switch provided in module SO. In an especially advantageous manner, a parallel triggering of sheathed-element glow plugs 51 of a plurality of sheathed-element glow plug units 120 is possible simultaneously since all sheathed-element glow plug units 120 or modules 50 are supplied with electrical energy via respective input 10. In this case it must be ensured that central glow control device 110 (FIG. 1) is able to provide sufficient electrical power via control line 110a, 110b, 110c, . . . , and that switches provided locally in sheathed-element glow plug units 120 for the connection of input 10 to the respective output 20 are configured for the currents that arise.

In a very advantageous manner, sheathed-element glow plug unit 120 has an energy-supply unit, which stores electrical energy supplied to sheathed-element glow plug unit 120 via control line 110a, 110b, 110c, and/or makes it available to the components of sheathed-element glow plug unit 120, in particular to local control unit 40. For this purpose the energy-supply unit may, for instance, be equipped with a voltage converter, protective diodes or also with a local charge-coupled store in a manner known per se.

A method of an example embodiment of the present invention is described in the following text with the aid of the flow chart shown in FIG. 5.

In step 200, central glow control device 110 (FIG. 1) first applies a specifiable voltage to control line 110a, and individual switches 15a, 15b of position-evaluation units 30 of the various sheathed-element glow plug units 120a, 120b, . . . are closed, so that a position is able to be evaluated.

Subsequently, in step 210, the determined position of each sheathed-element glow plug unit 120a, 120b, . . . is stored locally, for example in a non-volatile memory of local control unit 40. If applicable, status feedback of individual sheathed-element glow plug units 120 to central glow control device 110 may occur, in which a corresponding item of position information of the individual sheathed-element glow plug unit 120 is advantageously transmitted as well.

In step 220, a specific sheathed-element glow plug unit 120b is triggered. The triggering may, for example, be implemented in such a manner that central glow control device 110 first outputs the address or position of sheathed-element glow plug unit 120b to be triggered, possibly together with trigger parameters such as, for example, a trigger duration or a power profile or the like, using control lines 110a, 110b, . . . .

Following successful address or position comparison, the communications unit of corresponding sheathed-element glow plug unit 120b forwards the information received via control line 110a, 110b, . . . to local control unit 40 of sheathed-element glow plug unit 120b, and sheathed-element glow plug 51 of sheathed-element glow plug unit 120b will then be triggered accordingly.

A special advantage of system 100 is that all sheathed-element glow plug units 120 may have the same design and are quasi able to initialize themselves via the described position detection, so that no special sequence or the like need to be observed when sheathed-element glow plug units 120 are installed. Furthermore, the absolute number of sheathed-element glow plug units 120 connected to a central glow control device 110 is able to be determined in an uncomplicated manner.

In addition, the series connection allows a particularly uncomplicated and low-cost wiring with power losses that are lower than in conventional systems. In a particularly advantageous manner, first section 110a of the control line may have an especially large diameter, since a reduction in the power losses in this section 110a has an effect on all triggering processes as a result of the series connection.

The fact that only a single plug pin must be provided on central glow control device 110 in system 100 is to be considered an additional advantage, the plug pin being utilized to connect control line 110a.

Furthermore, measuring device V (FIGS. 3a, 4) integrated into the corresponding sheathed-element glow plug unit 120 makes it possible to perform a diagnosis of each individual sheathed-element glow plug 51.

A conventional protocol suitable for single-wire transmission is able to be used for the communication of components 110, 120 via control line 110a, 110b, 110c, . . . . In an advantageous manner, an interference-resistant and self-synchronizing Manchester coding is also employable for the encoding of data to be transmitted.

Furthermore, it is possible to use a low-pass frequency range for the energy transmission via control line 110a, 110b, 110c, . . . , in particular also for the supply of sheathed-element glow plugs 51, and to transmit control signal in a band-pass frequency range so that the control signals may, for instance, be separated from an equisignal provided for energy transmission, with the aid of corresponding filters in, e.g., a conventional manner.

In general, sheathed-element glow plug unit 120 or system 100 allows the use of sheathed-element glow plugs configured for an operating voltage of 11 Volt as well as low-voltage sheathed-element glow plugs.

To ensure reliable communication between central glow control device 110 and sheathed-element glow plug units 120a, 120b, it may be provided as standard state that input 10 is connected to output 20 in each sheathed-element glow plug unit 120, via a corresponding switch, for instance, and that the particular communications unit is activated in order to be able to evaluate trigger signals that may arise.

Claims

1-16. (canceled)

17. A sheathed-element glow plug unit, comprising:

an input configured to connect the sheathed-element glow plug unit to a control line, via which a sheathed-element glow plug of the sheathed-element glow plug unit is controllable; and

an output, via which at least one further sheathed-element glow plug unit is connectable to the control line.

18. The sheathed-element glow plug unit according to claim 17, further comprising a local control unit.

19. The sheathed-element glow plug unit according to claim 17, further comprising a local control unit arranged as at least one of (a) a microcontroller and (b) an application-specific integrated circuit.

20. The sheathed-element glow plug unit according to claim 17, further comprising a communications unit.

21. The sheathed-element glow plug unit according to claim 17, further comprising a position-evaluation unit including at least one of (a) a resistive, (b) an inductive, and (c) a capacitive component switchable between the input and the output.

22. The sheathed-element glow plug unit according to claim 21, further comprising a voltage measurement device configured to determine at least one of (i) a voltage dropping at the at least one of (a) the resistive, (b) the inductive, and (c) the capacitive component and (ii) a voltage between a connection of the at least one of (a) the resistive, (b) the inductive, and (c) the capacitive component and at least one of (a) a reference potential and (b) a ground potential.

23. The sheathed-element glow plug unit according to claim 17, wherein a grounded connection of the sheathed-element glow plug is permanently connected with a ground potential within the sheathed-element glow plug unit, and an operating-voltage connection of the sheathed-element glow plug is connectable to the input.

24. The sheathed-element glow plug unit according to claim 17, further comprising a voltage measurement device configured to determine at least one of (a) a voltage applied between the input and the output, (b) a voltage applied between the input and a reference potential, and (c) a voltage applied between the output and a reference potential.

25. The sheathed-element glow plug unit according to claim 17, further comprising an energy-supply unit configured to at least one of (a) store electrical energy supplied to the sheathed-element glow plug unit via the control line and (b) supply electrical energy to at least one of (a) components of the sheathed-element glow plug unit, (b) a control unit, and (c) a local control unit.

26. A system for operating a plurality of sheathed-element glow plugs, comprising:

a central glow control device;

at least two sheathed-element glow plug units, each including a sheathed-element glow plug;

wherein, via a control line, the central glow control device is connected only to a first sheathed-element glow plug unit, and additional sheathed-element glow plug units are switched in series to the first sheathed-element glow plug unit.

27. The system according to claim 26, wherein control signals for an operation of the sheathed-element glow plug units and electrical energy for at least one of (a) supply of components of the sheathed-element glow plug units and (b) supply of the sheathed-element glow plugs are transmittable via the control line.

28. The system according to claim 26, wherein at least one sheathed-element glow plug unit includes:

an input configured to connect the sheathed-element glow plug unit to the control line, via which a sheathed-element glow plug of the sheathed-element glow plug unit is controllable; and

an output, via which at least one further sheathed-element glow plug unit is connectable to the control line.

29. A method for operating a plurality of sheathed-element glow plug units, each sheathed-element glow plug unit including a sheathed-element glow plug, a central glow control device arranged to control the sheathed-element glow plug units, comprising:

acting upon, by the glow control device, a first sheathed-element glow plug unit, directly connected to the glow control device via a control line, with a corresponding control signal; and

if appropriate, forwarding the control signal to additional sheathed-element glow plug units connected in series to the first sheathed-element glow plug unit.

30. The method according to claim 29, wherein the control line is connected through the first sheathed-element glow plug unit to additional sheathed-element glow plug units to forward the control signal.

31. The method according to claim 29, wherein each sheathed-element glow plug unit determines its position in the series connection of the sheathed-element glow plug units.

32. The method according to claim 29, wherein at least one of (a) diagnosis reports and (b) status reports from a sheathed-element glow plug unit are transmitted to the central glow control device.

33. The method according to claim 29, wherein the control line is used to at least one of (a) supply consumers with electrical energy and (b) to supply the sheathed-element glow plugs.