U.S. patent application number 13/183773 was filed with the patent office on 2012-01-19 for electrical heating device.
This patent application is currently assigned to Eberspacher catem GmbH & Co. KG. Invention is credited to Dieter Emanuel, Holger Reiss.
Application Number | 20120014680 13/183773 |
Document ID | / |
Family ID | 43016581 |
Filed Date | 2012-01-19 |
United States Patent
Application |
20120014680 |
Kind Code |
A1 |
Emanuel; Dieter ; et
al. |
January 19, 2012 |
ELECTRICAL HEATING DEVICE
Abstract
The present invention relates to a PTC based heating device for
a motor vehicle, preferably with electrical propulsion, in which
one or a plurality of supplementary circuits are connected to a
heating circuit for being switched in optionally. In this way it is
possible to use a large number of possibilities for temperature
control for energy management which is important in electric
vehicles.
Inventors: |
Emanuel; Dieter; (Annweiler,
DE) ; Reiss; Holger; (Rheinzabern, DE) |
Assignee: |
Eberspacher catem GmbH & Co.
KG
Herxheim
DE
|
Family ID: |
43016581 |
Appl. No.: |
13/183773 |
Filed: |
July 15, 2011 |
Current U.S.
Class: |
392/465 |
Current CPC
Class: |
B60H 1/00385 20130101;
B60H 1/00278 20130101; B60H 1/2221 20130101; B60H 2001/00928
20130101; B60H 2001/00307 20130101; B60H 1/14 20130101 |
Class at
Publication: |
392/465 |
International
Class: |
F24H 1/10 20060101
F24H001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 16, 2010 |
EP |
10007395.6 |
Claims
1. A heating device for a motor vehicle, the heating device
comprising: a heating circuit with a liquid medium as heat transfer
medium, an electrical PTC heating element, arranged in the heating
circuit, for heating the liquid medium, and a supplementary circuit
with a separate heat source which can be optionally switched into
the heating circuit.
2. The heating device according to claim 1, further comprising a
control device for controlling the PTC heating element, wherein the
PTC heating element is controlled such that it contributes a
proportion of the total heating power which cannot be provided via
the supplementary circuit.
3. The heating device according to claim 1, further comprising a
control device for controlling the switching of the supplementary
circuit, so that a heating requirement of the heating device is
first of all covered by switching in the supplementary circuit.
4. The heating device according to claim 1, wherein the switching
of the supplementary circuit occurs with the aid of valves.
5. The heating device according to claim 1, further comprising a
pump for producing a circulation of the liquid medium in the
heating circuit.
6. The heating device according to claim 1, wherein the separate
heat source of the supplementary circuit is supplied from waste
heat of a vehicle component.
7. The heating device according to claim 6, wherein the motor
vehicle is a hybrid electric vehicle, and wherein the waste heat is
made available from a range extender internal combustion engine of
the hybrid vehicle.
8. The heating device according to claim 1, furthermore comprising
a temperature probe arranged in the heating circuit, wherein the
heating device is controlled such that a temperature measured by
the temperature probe is adjusted to a specified temperature target
value.
9. The heating device according to claim 1, wherein the
supplementary circuit is switched off when the supplementary
circuit cannot provide any heat for heating.
10. The heating device according to claim 1, comprising at least
one further supplementary circuit which can be switched in
optionally.
11. The heating device according to claim 1, wherein the
supplementary circuit is switched in when the temperature in the
heating circuit is to be reduced and the liquid medium in the
supplementary circuit, which is switched in, is colder than in the
heating circuit.
12. The heating device according to claim 1, wherein the PTC
heating element is controlled in dependence of a predetermined
heating power.
13. The heating device according to claim 2, wherein the PTC
heating element is controlled in dependence of a predetermined
heating power.
14. The heating device according to claim 12, wherein the
predetermined heating power is equal to the difference between the
required total heating power and a heating power which can be
covered by the supplementary circuit.
15. The heating device according to claim 10, wherein the
supplementary circuit, heats a specific region or a specific
component of the motor vehicle.
6. The heating device according to claim 1, wherein the PTC heating
element, a control device, valves for switching a supplementary
circuit in and out, and a pump for producing a circulation of the
liquid medium are arranged in a common housing. 17. The heating
device according to claim 1, wherein the PTC heating element, the
control device, valves for switching a supplementary circuit in and
out, and a pump for producing a circulation of the liquid medium
are arranged in a common housing.
18. The heating device according to claim 1, wherein the motor
vehicle is electrically propelled.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an electrical heating
device for a motor vehicle. In particular the present invention
relates to an electrical heating device with a fluid medium as heat
transfer medium which is suitable for electric and hybrid
vehicles.
[0003] 2. Description of the Related Art
[0004] With regard to heating there is a problem with vehicles with
electric or hybrid drive in that the drive unit of the motor
vehicle does not dissipate sufficient waste heat for the heating or
air conditioning. An appropriate vehicle heating system must
therefore be suitable for providing both the interior of the motor
vehicle with the required heat for heating purposes as well as
providing the heat required for or at least supporting the running
processes in the individual system parts of the motor vehicle, such
as for example for preheating the vehicle rechargeable battery. An
obvious method would be to provide the required heat by electrical
means. In the state of the art it is known that so-called
resistance heating elements or PTC (Positive Temperature
Coefficient) heating elements can be used for this purpose. They
are self-regulating, because they exhibit a higher resistance with
increasing heating, thus passing a lower amount of current. The
self-regulating properties of the PTC heating elements thus prevent
overheating.
[0005] Accordingly PTC heating elements are often used in heating
devices which are particularly used for heating the vehicle
passenger compartment in vehicles, the drive of which does not
produce sufficient process heat for the air conditioning or heating
system of the vehicle passenger compartment. With hybrid vehicles a
PTC heating device can also be used as an auxiliary heater in the
phases in which the internal combustion engine is not running (e.g.
at traffic lights or in a traffic jam).
[0006] When electrical heating elements are employed in a vehicle
with electric propulsion there is a further problem in that the
vehicle battery (accumulator) acts as the energy source both for
the vehicle drive to provide traction as well as for the heating.
Thus, the vehicle drive and the heating are competing for the
limited amount of energy which is available between two battery
charging processes. Expressed in another way, the vehicle operating
range between two battery charges reduces with the electrical
energy used for electric heating.
[0007] Therefore, in an electric or hybrid vehicle a well
thought-out concept of energy management plays a central role in
which the drive, the heating and other components consuming
electrical power, such as the lighting, are taken into account. An
important aspect of energy management is the use of additional
energy resources in the vehicle which are not based on the
electrical energy of the battery. Resources of this nature are
available in the vehicle in particular in the form of waste heat
from certain vehicle components. Components, which make additional
energy available in the form of waste heat include an additional
internal combustion engine on hybrid vehicles ("range extender"),
brakes and the vehicle battery itself or a built-in battery charger
(on-board charger). It is therefore desirable to exploit the waste
heat arising in the vehicle within the scope of the energy
management system as far as possible for the heating in order to
extend the operating range. With PTC heating the air in the vehicle
passenger compartment is heated with the aid of the PTC resistance
heating elements either directly (air heater) or indirectly via a
circuit in which a hot liquid flows through radiators. Preferably,
water is used as the liquid (hot-water heating). For the energy
management system hot-water heating has the advantage that the
waste heat taken up by water in one region of the vehicle (cooling
circuit) can be used by cooling and heating circuit for heating at
another location.
[0008] It should be noted however that waste heat from vehicle
components is generally only available temporarily. Thus, an
additional internal combustion engine on a hybrid vehicle only
supplies waste heat when it runs. Braking supplies a significant
amount of waste heat, in particular during longer downhill
sections. With regard to the vehicle battery the situation is such
that it must first be brought to a required operating temperature
by preheating and is then cooled during running operation. The
combination of heating and cooling circuits is thus in particular a
disadvantage if with the lack of waste heat, the presence of a
large quantity of cold coolant in circulation prevents efficient
heating and thus negatively affects the electrical energy
consumption and operating range.
SUMMARY OF THE INVENTION
[0009] An object of the present invention is to provide a heating
device for a motor vehicle, in particular with electrical
propulsion, which facilitates efficient energy management.
[0010] According to the present invention, an electrical heating
device for a motor vehicle, in particular with electrical
propulsion, is provided. A liquid medium is used with the heating
device as the heat transfer medium. The heating device comprises a
heating circuit with a liquid medium as the heat transfer medium.
Furthermore, the heating device comprises an electrical PTC heating
element arranged in the heating circuit for heating the liquid
medium. Moreover, the heating device comprises a supplementary
circuit with a separate heat source which can be optionally
switched into the heating circuit.
[0011] It is the particular approach of the present invention to
arrange a heating device with an electrical PTC heating element
such that additional heat sources made available can be used for
efficient energy management. This is achieved in that a
supplementary circuit, which makes heat available separately from
the electrical heating element, can be switched in optionally. By
controlling the switching in and out of the supplementary circuit,
depending on the heating requirement and operating conditions, the
supplementary circuit can be included in the energy management.
[0012] The heating device may also comprise a control device for
controlling the PTC heating element. This enables the PTC heating
element to be controlled such that it bears a proportion of the
total heating power which cannot be supplied by means of the
supplementary circuit. It is thus achieved that the heating is
supplied as far as possible from non-electrical energy sources, in
particular from waste heat. The electrical heating is used when the
heat from other sources is not sufficient.
[0013] The alternative switching in of the supplementary circuit
may be controlled such that the heat requirement of the heating
device is first of all covered by switching in the supplementary
circuit. The supplementary circuit is controlled such that it is
switched in when the heating device has a heat requirement which
can be covered by the supplementary circuit. According to a
preferred embodiment, the optional switching in of the
supplementary circuit occurs with the aid of valves.
[0014] Further, the heating device may additionally comprise a pump
with which circulation of the liquid medium is produced in the
heating circuit. The circulation of the fluid medium in the heating
circuit is used for the transport of the heat provided by the
electrical heating element and, where applicable, further heat
sources. This can occur in that the pump is only switched on and
off as required, or also by additional control of the pump power.
Generally the following applies: the higher the heating power, the
larger the flow velocity in the circuit must be. With large heating
power requirements a larger amount of heat can be transported with
a higher rotational speed.
[0015] The separate heat source of the supplementary circuit may be
the waste heat from a component of the motor vehicle. In this way
existing heat is efficiently exploited which would otherwise have
to be uselessly dissipated. Therefore the cooling of one component
or a region of the vehicle can be linked with the heating of
another component or another vehicle region. This is employed to
save the electrical vehicle energy and thus to increase the
operating range of the vehicle. Heat may be made available by the
internal combustion engine of a hybrid vehicle. An internal
combustion engine of this nature can in particular be a so-called
"range extender" which is particularly switched in for longer trips
in order to increase the range. A range extender of this nature can
in particular be used in the serial hybrid design, whereby the
internal combustion engine (range extender) produces electrical
energy, which can be used via a generator directly for the vehicle
drive as well as indirectly for battery charging. Combinations are
possible through alternative switching. Alternatively, a range
extender can also be switched in via a clutch as a direct drive for
vehicle propulsion (parallel hybrid design).
[0016] Further conceivable heat sources for feeding the
supplementary circuit are the waste heat from the brakes, in
particular on longer downhill sections, and the waste heat from the
vehicle battery. With vehicle batteries used for electric and
hybrid vehicles in the automotive high voltage range of a few
hundred volts (e.g. 300 V, 380 V or 500 V) the continual cooling of
the battery during operation plays a significant role. On the other
hand, when putting the vehicle into operation it is initially
necessary to preheat the cold battery to a certain operating
temperature. Within the scope of the present invention it is, for
example, possible to use the valve control of a supplementary
circuit initially for preheating the battery, and when it has
reached operating temperature, the battery waste heat is used for
heating the vehicle passenger compartment.
[0017] In the vehicle configuration the heating device according to
the invention may comprise further supplementary circuits which can
be switched in optionally.
[0018] The heating device furthermore may comprise a temperature
probe (temperature sensor) arranged in the heating circuit, whereby
the heating device is controlled such that a temperature measured
by the temperature probe is adjusted to a specified temperature
target value. Furthermore, the control device may comprise a
comparator, which compares the temperature measured by the
temperature probe to a temperature target value. Within the
framework of the energy management system according to the
invention, if the temperature is to be increased, initially a
status check may occur of whether a supplementary circuit is able
to supply sufficient hot water. It is only when this is not
sufficient that the power of the PTC is increased. For the case in
which the temperature is to be reduced, initially the PTC heating
power may be reduced and then cold water from a supplementary
circuit is supplied if necessary for faster cooling.
[0019] Further, a supplementary circuit may be switched off when it
cannot make heat available for heating. This is particularly
important when the electrical heating must be called upon for
heating. In the cold vehicle state, for example before the start of
a trip, heating up takes place more efficiently the less cold water
there is initially in circulation which has to be heated.
[0020] In a heating device according to the present invention the
PTC heating element may be controlled in dependence of a
predetermined heating power. Also, the predetermined heating power
is here equal to the difference of a required total heating power
and a heating power which can be covered by supplementary
circuits.
[0021] According to an embodiment, one or a plurality of PTC
heating elements, a control device, valves for switching one or a
plurality of supplementary circuits in and out and a pump for
generating a circulation of the fluid medium may be arranged in a
common housing. A form of construction of this nature facilitates a
particularly compact heating device, in which in particular the
elements required for the control are integrated into the heating
device such that their available processor capacity is optimally
exploited and separate control units are superfluous. This
facilitates a higher integration and reduces the general complexity
of control.
[0022] Preferably, water is used as the liquid medium (heat
transfer medium).
[0023] Further advantageous embodiments of the present invention
are the subject matter of dependent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The invention is described in the following based on the
accompanying figures in which:
[0025] FIG. 1 illustrates a heating circuit of a heating device
with a supplementary circuit according to the present invention,
whereby
[0026] FIG. 1A illustrates a state in which the supplementary
circuit is separated from the heating circuit; and
[0027] FIG. 1B illustrates a state with an open (included in the
heating circuit) supplementary circuit;
[0028] FIG. 2 illustrates a representation of a heating circuit
according to the present invention with a further supplementary
circuit;
[0029] FIG. 3 shows a schematic representation of a control concept
for a heating device according to the present invention;
[0030] FIG. 4 illustrates a flow chart for an embodiment of the
control of a heating device according to the present invention;
and
[0031] FIG. 5 illustrates a further flow chart for an example of a
control of a heating device according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0032] The present invention relates to a motor vehicle heater
which may be formed as a hot-water heater and comprises one or a
plurality of PTC heating elements. If a plurality of heater
elements are present, they may be combined to form one or a
plurality of heating stages, whereby the heater elements of a
heating stage are controlled together. A control is for example
possible with the aid of pulse width modulation (PWM). Furthermore,
a combination of a plurality of binary heating stages is possible
which can be adjusted quasi-continuously or in fine steps using
PWM. Thus, a finely stepped adjustability with minimisation of the
undesired side effects present in the automotive high voltage range
such as EMC (Electro-Magnetic Compatibility) interference can be
achieved.
[0033] A heating device according to the present invention
facilitates heating of the vehicle passenger compartment and, where
applicable, further vehicle components, whereby apart from the
electrical energy (via the PTC heating elements) further
(preferably non-electrical) heat sources can also be used. The
latter furthermore may involve waste heat from vehicle components
which have to be cooled and the waste heat of which would otherwise
be lost and unused. To achieve this, the heating device comprises
according to the present invention, along with a main circuit
(heating circuit), one or a plurality of supplementary circuits,
which are switched in optionally. With the aid of a suitable
control device the optional switching in and out occurs such that
the heating device supports efficient energy management of the
vehicle. In this respect, it is achieved that the electrical
heating power is only drawn on when there is not sufficient heat
available from other sources. This contributes to an efficient
exploitation of the electrical energy and thus to as large a
vehicle range (operating range) as possible.
[0034] With the objective of reducing the general outlay for
control, the processor capacity, which is necessary in any case for
the control of the electrical heating device, may be assigned
additional tasks which provide control of the supplementary
circuits.
[0035] An example of a construction of a heating device according
to the invention with a heating circuit (main circuit) 2 and a
supplementary circuit 3 is shown schematically in FIG. 1. FIG. 1A
illustrates the supplementary circuit in the state shut off from
the main circuit and FIG. 1B shows the opened supplementary
circuit, so that the fluid heat transfer medium (designated as
water as an example in the following) flows through the
supplementary circuit 3.
[0036] The heating device 1 comprises a main circuit 2 and a
supplementary circuit 3 connected by means of 3/2-way valves 40a
and 40b.
[0037] Arrows in the circuit symbolise the water flowing through
the circuit. For reasons of safety in the motor vehicle the maximum
water temperature is preferably 60.degree. C.
[0038] In the main circuit there is also a PTC heating element 20,
a radiator (heat exchanger) 30 and a pump 60. In a preferred
embodiment illustrated here the valves 40a and 40b are arranged in
a part of the heating circuit 2 located opposing the direction of
flow relative to the PTC heating 20. However another arrangement is
also possible. An additional heat source 50, arranged in the
supplementary circuit, is in a preferred embodiment an additional
internal combustion engine (range extender) of a hybrid
vehicle.
[0039] The power supply of the PTC heating element 20 is provided
by the vehicle battery 10, which is also responsible for the
traction (propulsion) of the vehicle. In the heat exchanger
(radiator) 30 heat is dissipated from the water to the surrounding
air. The radiator 30 can be arranged such that the air, for example
in the vehicle passenger compartment, is directly heated.
Alternatively, air can be heated, which for example is blown into
the vehicle passenger compartment by a fan. Furthermore, it is
possible to realise a combined direct and indirect heating of the
interior air with the aid of a plurality of radiators. The pump 6,
preferably driven electrically, maintains the flow of water in the
circuit. Depending on the control of the valves 40a and 40b, the
circulation of the water in the circuit occurs either directly
through the short section of the main circuit between valve 40a and
valve 40b (FIG. 1A) or however by inclusion of the supplementary
circuit 3 (FIG. 1B). As shown in FIG. 1B, here the water flows
starting from the valve 40a, which is open in the direction of the
supplementary circuit 3, initially through the supplementary
circuit to the range extender 50. Here the water can, preferably
with the aid of a further heat exchanger (not illustrated in the
figure), take up waste heat from the range extender. Then the water
flows through the supplementary circuit 3 via the valve 40b, which
is actuated appropriately, back into the main circuit.
[0040] Instead of the range extender 50, in the supplementary
circuit another heat source can also be arranged, separate from the
electrical PTC heating. With the aid of an appropriate heat
exchanging device the waste heat from the brakes, for example, can
be removed by the water flowing through the supplementary
circuit.
[0041] In order to include the heating device 1 in the overall
system of energy management of the electric or hybrid vehicle, an
appropriate control of at least the PTC heating element 20 and the
valves 40a and 40b is required. The control concept and the
corresponding control device (not illustrated in FIG. 1) are
explained in further detail with reference to FIGS. 3 and 5. The
pump 60 may also be controlled by the control device, whereby
either only its on/off switching or also the pump power (dependent
on the rotational speed) can be controlled. From a standpoint of
mechanical construction it is advantageous if the PTC heater is
integrated into one single housing together with the valves, pump
and control device. This saves space and is particularly
cost-effective.
[0042] Within the scope of the concept of the present invention it
is furthermore possible, through further supplementary circuits
which can be optionally switched in, to supply certain regions of
the motor vehicle specifically with heat (optionally included in
the heating circuit). The valves for connecting optional
supplementary circuits of this nature are preferably arranged in
the direction of flow as viewed from the electrical PTC heating
device.
[0043] In FIG. 2, along with the supplementary circuit 3 which can
be alternatively switched in via the control of the valves 40a and
40b, a second supplementary circuit 3a, which can be alternatively
switched in with the aid of the 3/2-way valves 40c and 40d, is
illustrated. In the example illustrated in FIG. 2 the supplementary
circuit 3a runs in the vicinity of the vehicle battery 10. A
supplementary circuit of this nature can fulfil two functions:
[0044] On the one hand, the supplementary circuit 3a can be used to
preheat the battery until it reaches its operating temperature. For
this purpose the supplementary circuit 3a is included in the
heating circuit by appropriate control of the valves 40c and 40d
and has water flowing through it which is heated by the PTC heating
element 20. In the phase of preheating the battery the valves 40a
and 40b are preferably controlled such that the supplementary
circuit 3 of the range extender is switched off. Since it cannot
provide any heat before the vehicle is put into operation, it is
advantageous for the rapid and efficient heating of the water in
the heating circuit to reduce the circulating water quantity by
switching off the supplementary circuit 3.
[0045] Furthermore, it is also alternatively possible to provide
the radiator 30 for heating the vehicle passenger compartment also
in a section of the circuit which can be switched in alternatively
by suitable valves (not illustrated in FIG. 2). With an embodiment
of this nature and for especially fast heating of the battery, the
radiator 30 can be initially removed from the heating circuit and
later, preferably once the battery has reached its operating
temperature, switched in again. The supplementary circuit 3a can be
switched off at the same time.
[0046] On the other hand, the circuit 3a can be used as an
additional heat source in a similar manner as the supplementary
circuit 3 illustrated on the left in FIG. 2. Here, the battery
waste heat arising during the running operation of the battery 10
can be used as a separate heat source. For this purpose, the
supplementary circuit 3a is not separated from the rest of the
circuit once the battery reaches its operating temperature, or it
is switched in again at a later time during running operation,
depending on the demand.
[0047] FIG. 3 shows an overview of the control concept of the
heating device according to an embodiment of the present invention.
An important advantage of the present invention is that the control
device for the control of the valves and pumps can be integrated
into the control electronics which are in any case present in a
high voltage (HV) PTC heater 20. In other words the processor
capacity of the control electronics already present in the PTC
heater is assigned additional tasks, such as the control of the
pump 60 and the valves (symbolised in FIG. 3 by the 3/2-way valves
40a and 40b). For this purpose the HV PTC heater also has, in
addition to the high voltage connection (symbolised by the HV plug
22), connections in the automotive low voltage range (LV--low
voltage--symbolised by the LV plug 24). These are used on one hand
for the transfer of control data to the components (pumps and
valves) which are external to the HV PTC 20. On the other hand
control data is transferred to the control device via these
connections. In the illustrated picture the air conditioning
operating panel 70 of the vehicle is shown as an example data
source. In this way it is possible for example for demands for a
desired temperature or also power demands to be entered by the
user. Data communications preferably occur via a vehicle bus
(symbolised in FIG. 3 by a LIN bus). The invention is however not
restricted to certain interface formats. Other bus systems can also
be used, such as for example CAN bus systems. Via the control
connections in the low voltage range (preferably via the vehicle
bus system) further data relevant for the control of the heating
device can be communicated to the control device integrated into
the HV PTC 20. This relates, for example, to the provision of data
which is determined by temperature measurement devices (temperature
sensors) in the heating circuit or at other positions in the
vehicle. Alternatively or additionally, with regard to the
availability of heating energy (e.g. from waste heat) in certain
supplementary circuits which can be switched in alternatively, data
can be communicated over the vehicle bus and the LV plug 24 to the
control device.
[0048] Embodiments of a control of a heating device according to
the present invention are described in the following as examples
based on the flow charts in FIGS. 4 and 5.
[0049] FIG. 4 illustrates a processing example in which a measured
temperature is to be adjusted to a specified temperature target
value. In this respect the measured temperature may be a
temperature acquired by a temperature probe at a certain position
of the heating circuit. Here, the temperature probe is preferably
arranged, viewed in the flow direction, behind the PTC heating
device. However, other arrangements are also possible.
[0050] Alternatively, a temperature may be involved which is
measured in a region of the motor vehicle which is heated by the
heating device. This may be, for example, the vehicle passenger
compartment. It may however also be a temperature at another region
of the motor vehicle, such as for example in the region of the
vehicle battery (accumulator).
[0051] In a first step in the method (S10) the temperature target
value T.sub.SET is defined. This can be done by an operator (driver
or vehicle occupant), for example with the aid of the air
conditioning operating panel 70. In the second step in the method
(S20) the control electronics integrated into the HV PTC heating
device 20 checks whether the temperature currently measured by the
temperature probe T.sub.ACTUAL is lower than the temperature target
value. If the measured temperature value is lower than the
specified temperature target value (S20:Y), the method moves on to
step S30.
[0052] In step S30 the control electronics carries out an
assessment of whether a shut-off supplementary circuit can provide
additional heat. Information of this nature may be made available
to the control device via the vehicle bus. For example, the control
device has information available about the available waste heat of
a range extender (additional internal combustion engine on a hybrid
vehicle) via the temperature of the range extender. Analogously,
appropriate information for other sources supplying heat, such as
for example brakes or the vehicle battery, can be made available
based on their temperature.
[0053] In the case where a shut-off supplementary circuit can
provide heat (S30:Y), in the following step (S40) the relevant
supplementary circuit is switched in by appropriate control of the
valves. The method then proceeds to step S60. In step S60 the
control electronics assesses whether the supplementary circuit can
provide sufficient heat to bring the temperature to the temperature
target value T.sub.SET. If the assessment is positive (S60:Y), the
method finishes according to FIG. 4. As shown by the arrow
(S60:Y->S20), the processing cycle then starts from the
beginning. In the alternative case (S60:N) the heating power of the
PTC heating device is increased in the next step (S50).
[0054] If alternatively the assessment in step S30 reveals that
currently no shut-off supplementary circuit is able to provide
additional heat (S30:N), the method then moves directly to step
S50. In step S50 the PTC heating power is increased by the control
device.
[0055] If it is furthermore found in the assessment step S20 that
the currently measured temperature is not lower than the
temperature target value (S20:N), the method initially continues
with the assessment step S70. In step S70 it is assessed whether
the current temperature is higher than the temperature target
value. If this is not the case (S70:N), i.e. the current
temperature (within a specified tolerance as applicable) is equal
to the temperature target value, then the method terminates
according to the flow chart of FIG. 4 and the cycle starts again
with the step S20.
[0056] In the alternative case (S70:Y), i.e. when the measured
temperature is higher than the temperature target value, the method
proceeds with step S75. In step S75 the control device assesses
whether the PTC heating device is currently supplying heat. If the
PTC heating device is currently supplying heat, at (S75:Y), then
the method proceeds to step S90. In step S90 the control device
assesses whether a currently shut-off supplementary circuit is
present which can feed cold water into the heating circuit. If this
is not the case (S90:N), the method terminates according to the
flow chart in FIG. 4. In the alternative case (S90:Y) initially all
supplementary circuits which can supply cold water (step S100) are
switched in. Thus, fast cooling is achieved (aligning the
temperature actual value with the temperature target value).
[0057] If it is assessed in the assessment step S75 that currently
heat is being supplied by the PTC heating device (S75:N), the PTC
heating power is initially reduced in the following step S80. Then
the method returns to the decision step S20 and a further check is
made of whether the reduction of the PTC heating power obtained is
sufficient to equalise the measured temperature to the temperature
target value.
[0058] Accordingly, the method is continuously repeated following
the loops illustrated in FIG. 4, starting from the assessment step
S20. Alternatively, the assessment can also be implemented
according to the steps S20 and, where applicable S70, in specified
regular intervals. This results in a corresponding waiting period
between the end of one passage through the loop and the start of
the next passage through the loop S20. A restart of the method
according to FIG. 4, with step S10, occurs with each redefinition
of the specified target temperature T.sub.SET.
[0059] Other modifications of the sequence illustrated in FIG. 4 as
an example are possible within the scope of the present invention.
For example, initially step S70 can be carried out to assess
whether T.sub.ACTUAL>T.sub.SET and in the negative case the
method continues with step 20.
[0060] A further alternative is that instead of a temperature
(T.sub.SET) a heating power to be obtained is specified. The
control of the heating device including the PTC heating device 20
and the supplementary circuits 3, 3a then occurs in that it is
initially assessed which proportion of the heating power demand can
be supplied from non-electrical heat sources via supplementary
circuits. Within the scope of energy management the use of the PTC
heating is restricted to the remaining part which cannot be
supplied from other sources. Finally, it is also possible that a
power specification has its origin in a temperature specification
which is converted into a power specification by the control
electronics.
[0061] In the following the method is described according to
another embodiment for the control of the heating device according
to the invention with reference to the flow chart in FIG. 5.
[0062] On putting the motor vehicle into operation after a longer
period at standstill, the method according to FIG. 5 starts in step
S200 with the PTC heating device 20 being switched on and the
battery supplementary circuit 3a being switched in to preheat the
vehicle battery 10 through appropriate control of the valves 40c
and 40d (refer to FIG. 2). Since with the vehicle at standstill no
thermal energy is to be expected from supplementary heat sources,
such as waste heat, the position of the valves for the connection
of further supplementary circuits, such as for example,
supplementary circuit 3 for the range extender 50, is preferably in
the shut-off position. Thus, a faster circulation of water and
therefore faster preheating of the battery are achieved.
[0063] Then in the assessment step S210 it is assessed whether the
operating temperature of the vehicle battery 10 has been reached.
As long as the operating temperature of the battery 10 has not been
reached (S210:N), the status of the heating device remains
unchanged (loop S210:N->S210).
[0064] When the battery operating temperature has been reached
(S210:Y), the method continues to step S220. In step S220 the
battery supplementary circuit 3a is initially switched off in that
the position of the valves 40c and 40d is changed appropriately.
Then in step S230 the control device assesses whether a requirement
on additional heat is needed in the circulation and whether the
supplementary circuit 3a of the battery can provide waste heat. An
assessment of this nature can take place, for example, within the
scope of energy management which is illustrated in FIG. 4 as an
example. Alternatively, the assessment can also be implemented
according to different criteria, for example, based on a certain
heating power specification.
[0065] As long as no battery waste heat is available or required
for heating (S230:N), the status of the heating device remains
unchanged. Otherwise (S230:Y) the battery supplementary circuit 3a
is switched in again by the control device in step S240 through
appropriate control of the valves 40c and 40d.
[0066] The present invention, as defined in the accompanying
claims, is not restricted to the embodiments described in detail
above. In particular individual features of certain embodiments can
be combined, provided this does not lead to conflicts.
[0067] Summarising, the present invention relates to a PTC based
heating device for a motor vehicle, preferably with electrical
propulsion, in which one or a plurality of supplementary circuits
are connected to a heating circuit for being switched in
optionally. In this way it is possible to use a large number of
possibilities for temperature control for energy management which
is important in electric vehicles.
* * * * *