Fuel-operated vehicle heater and method for operating a fuel-operated vehicle heater

Abstract

A method for operating a fuel-operated vehicle heater, wherein after receipt of a switch-off signal by a control unit of the fuel-operated vehicle heater, a shutdown phase is initiated, during which remaining fuel present in the fuel-operated vehicle heater is combusted, and wherein a restart phase is initiated by the control unit after receipt of a switch-on signal during the shutdown phase, without the shutdown phase being terminated after complete combustion of the remaining fuel.

Claims

1. Method for operating a fuel-operated vehicle heater, wherein after receipt of a switch-off signal by a control unit of the fuel-operated vehicle heater, a shutdown phase is initiated, during which remaining fuel present in the fuel-operated vehicle heater is combusted, and wherein a restart phase is initiated by the control unit after receipt of a switch-on signal during the shutdown phase, without the shutdown phase being terminated after complete combustion of the remaining fuel.

2. Method according to claim 1, wherein during the shutdown phase, combustion air is supplied to a burner of the fuel-operated vehicle heater while no new fuel is supplied to the burner.

3. Method according to claim 1, wherein combustion air and new fuel are supplied to the burner during the restart phase.

4. Method according to claim 3, wherein an amount of fuel V.sub.restart supplied to the burner at the beginning of the restart phase corresponds to an amount of fuel V.sub.shutdown supplied at the beginning of the shutdown phase when the shutdown phase lasts for less than a predetermined time interval Δt.sub.1 at receipt of the switch-on signal.

5. Method according to claim 3, wherein an amount of fuel V.sub.restart supplied to the burner at the beginning of the restart phase corresponds to a fraction of an amount of fuel V.sub.shutdown supplied immediately before the shutdown phase begins when the shutdown phase lasts for more than a predetermined time interval Δt.sub.1 at receipt of the switch-on signal.

6. Method according to claim 5, wherein the amount of fuel V.sub.restart supplied to the burner at the beginning of the restart phase is increased during a further time interval Δt.sub.2 from the fraction of the amount of fuel V.sub.shutdown supplied immediately before the shutdown phase begins to the amount of fuel V.sub.shutdown supplied at the beginning of the shutdown phase.

7. Method according to claim 3, wherein the amount of combustion air V.sub.air supplied to the burner during the restart phase is adapted to the amount of fuel V.sub.restart supplied to the burner such that during the entire restart phase an air number λ is maintained which is constant over time or which follows a predetermined temporal course.

8. Fuel-operated vehicle heater having a control unit configured to perform the method according to claim 1.

Description

(1) The disclosure described above is now explained by way of example with reference to the accompanying drawings using a preferred embodiment.

(2) It shows:

(3) FIG. 1 a flow diagram of a method for operating a fuel-operated vehicle heater; and

(4) FIG. 2 a schematic illustration of a fuel-operated vehicle heater.

(5) FIG. 1 shows a flow diagram of a method 100 for operating a fuel-operated vehicle heater. The described method 100 starts for example in a normal operation 110. Starting from this, it is checked in step 120, whether a switch-off signal is received. This can be done, for example, in a control unit of the fuel-operated vehicle heater. If no switch-off signal is received, step 120-No, normal operation is maintained. If, on the other hand, the switch-off signal is received, step 120-Yes, a shutdown phase is initiated and in a subsequent step 130, it is checked whether the shutdown phase has been completed. The shutdown phase can also be controlled by the control unit. Any present fuel, i.e., remaining fuel, can be burned in a controlled manner in a burner of the fuel-operated vehicle heater during the shutdown phase. If the shutdown phase is completed, step 130-Yes, the fuel-operated vehicle heater is switched-off, step 140. If, on the other hand, the shutdown phase is not completed, step 130-No, it is checked whether a switch-on signal is received in a subsequent step 150. If no switch-on signal is received, step 150-No, it is checked again whether the shutdown phase is terminated in step 130. If, on the other hand, a switch-on signal is received, step 150-Yes, a restart phase of the fuel-operated vehicle heater is initiated in a subsequent step 160 and it is continued in normal operation 110 after completion of the restart phase. The restart phase can, for example, be characterized by reaching an operating state which is identical to an operating state which was present as normal operating state immediately before the initiation of the shutdown phase.

(6) The shutdown phase can in particular be characterized in that combustion air is supplied to the burner while no new fuel is supplied to the burner. The restart phase can in particular be characterized in that besides combustion air new fuel is supplied to the burner.

(7) FIG. 2 shows a schematic illustration of a fuel-operated vehicle heater 10. The fuel-operated vehicle heater 10 shown in FIG. 2 is supplied with fuel via a fuel line 12 and with combustion air via a combustion air line 14. The supplied combustion air can be conveyed via a combustion air supply device 18 to a burner 32. The supplied fuel can be conveyed via a fuel supply device 20 to the burner 32. The fuel supplied to the burner 32 can, for example, be thermally evaporated in a fuel evaporator 30. The fuel evaporator 30 can comprise an evaporator fleece, in which a certain amount of supplied fuel is stored during normal operation so that fuel, which can be described as the remaining fuel, is still present in the burner 32 after switching off the fuel supply device 20. The combustion air supply device 18 can for example be designed as a throttle and/or blower. The fuel supply device 20 can for example be designed as a dosing pump. The combustion air supply device 18 and the fuel supply device 20 can be connected to a control unit 16 via a control line 22 and another control line 24 respectively. The control unit 16 can control the combustion air supply device 18 and the fuel supply device 20 via the two control lines 22, 24, for example to maintain a specific air number λ during the operation of the fuel-operated vehicle heater 10. Furthermore, the fuel-operated vehicle heater 10 may include an ignition device 26, which may also be controlled by the control unit 16. The ignition device 26 can, for example, be a glow plug. The glow plug can, for example, promote the thermal evaporation of fuel in the fuel evaporator 30 during a starting phase of the fuel-operated vehicle heater 10. The ignition device 26 may optionally be operated during the restart phase of the fuel-operated vehicle heater 10, in order to avoid an extinguishing of the residual flame in the fuel-operated vehicle heater 10 until the normal operating condition is restored. Preferably, however, the ignition device 26 is not operated during the restart phase. For example, if an activation of the ignition device 26 is required during the restart phase at all, the ignition device 26 may be deactivated about 70% of the time and activated about 30% of the time. Also shown is a sensor device 28 via which the control unit 16 can record measured values, for example with regard to temperature and exhaust gases. These can be advantageous, for example, for the precise regulation of the desired air number λ during operation of the fuel-operated vehicle heater. The control unit 16 can receive a switch-off signal 34 and a switch-on signal 36. Based on the reception of a switch-off signal 34, a shutdown phase can be initiated by the control unit 16 while the remaining fuel present in the burner 32 is burned completely in a controlled manner. If the control unit 16 receives the switch-on signal 36, either the switched-off fuel-operated vehicle heater 10 is switched-on in the usual manner or, if the switch-on signal 36 is received during the shutdown phase, a restart phase is initiated.

(8) The features of the disclosure which are disclosed in the above description, in the drawings and in the claims may be essential both individually and in any desired combination for the purpose of implementing the disclosure.

LIST OF NUMERALS

(9) 10 fuel-operated vehicle heater

(10) 12 fuel line

(11) 14 combustion air line

(12) 16 control unit

(13) 18 combustion air supply device

(14) 20 fuel supply device

(15) 22 control line

(16) 24 further control line

(17) 26 ignition device

(18) 28 sensor device

(19) 30 fuel evaporator

(20) 32 burner

(21) 34 switch-off signal

(22) 36 switch-on signal

(23) 100 method

(24) 110 normal operation

(25) 120 shutdown?

(26) 130 shutdown phase completed?

(27) 140 off

(28) 150 switch-on signal received?

(29) 160 initiate restart phase