Heatable washer system which is intended for a motor vehicle

In a washer system (9) which is intended for a motor vehicle, a delivery unit (1) is used to supply a washer nozzle (11) which is connected by a pipe element (10). To protect against damage at low ambient temperatures, a heating element (5) is arranged on a housing (7) of a pump chamber (3) of the delivery unit (1) and thus makes it possible for the washer fluid situated in the pump chamber (3) to be heated rapidly and in a specific manner.

FIELD AND BACKGROUND OF THE INVENTION
 The invention relates to a heatable washer system which is intended for a
 motor vehicle and has a delivery unit for washer fluid.
 In modern motor vehicles, washer systems of this type are used above all
 for cleaning the windshield or a headlamp lens. For this purpose, the
 washer system has a washer nozzle by means of which the washer fluid is
 directed onto the glass as a finely concentrated washer fluid jet. The
 washer fluid jet thereby detaches the particles of dirt adhering to the
 glass and thus ensures an optimum cleaning action.
 In order also to make satisfactory operation in winter possible, washer
 systems of this type are frequently designed such that they can be heated,
 so that a possible freezing up of the washer fluid in the washer system
 can be avoided. In, particular, it is already known to heat the washer
 fluid pipe and the washer nozzle.
 In the case of washer systems of the abovementioned type, it has proved to
 be disadvantageous that the heating of the washer fluid in the washer
 fluid pipe and in the region of the washer nozzle is insufficient to
 ensure a troublefree flow of washer fluid even at low ambient
 temperatures. The washer fluid flow can be impeded in particular by frozen
 particles of washer fluid, as a result of which the delivery power of the
 delivery unit is considerably impaired and damage to the delivery unit may
 be caused.
 SUMMARY OF THE INVENTION
 The invention is based on the problem of providing a washer system of the
 type mentioned at the beginning in such a manner that functional
 impairment of the delivery unit because of frozen washer fluid can largely
 be eliminated.
 According to the invention, this problem is solved in that the delivery
 unit is provided such that it can be heated by means of a heating element.
 This is able to prevent the washer fluid from freezing up in the delivery
 unit. Sufficient delivery power is thereby ensured even at very low
 ambient temperatures and possible damage, caused by the frozen washer
 fluid expanding in the delivery unit, is prevented.
 For this purpose, the delivery unit may be constructed such that it can be
 heated as a whole. In contrast, a development of the invention is
 particularly favorable in which the delivery unit has a pump chamber which
 can be heated by means of the heating element. By this means, that region
 through which the washer fluid flows can be heated by means of the heating
 element in a specific manner. As a result, the required heating power can
 be set comparatively low with, at the same time, rapid heating of the
 washer fluid being made possible.
 In this case, an embodiment is favorable in which the heating element can
 be heated by means of a cooling-water circuit of an internal combustion
 engine of the motor vehicle. By this means, the waste heat of the internal
 combustion engine can be used to heat the delivery unit. In the process, a
 substream of the cooling water heated by the internal combustion engine
 may, for example, be branched off and supplied to the heating element,
 which serves at the same time as a heat exchanger. In this case, an
 additional, electrical supply of energy is not required.
 It is also particularly favorable if the washer system has a heatable
 washer fluid container for the washer fluid, and the heating element has a
 heat-exchange surface which is wetted by the washer fluid. In this case,
 the delivery unit is arranged, for example, in the interior of the washer
 fluid container and is at the same time heated by means of the washer
 fluid contained in the washer fluid container. As a result, only one
 heat-exchange surface needs to be provided for the heating element, the
 additional energy consumption being inconsiderable.
 An embodiment of the invention is particularly advantageous in which the
 heating element can be heated electrically. By this means, the heating
 element can be operated irrespective of the operating state of the motor
 vehicle. In particular, sufficient heating power can be achieved thereby
 when the internal combustion engine is at a standstill. At the same time,
 simple control of the heating power, for example, with the aid of
 temperature sensors, is possible.
 In this case, it is particularly favorable if the heating element is a
 resistance heating wire. The resistance heating wire can also be
 retro-fitted on the delivery unit without any problem. At the same time,
 the heating wire may also be adapted without difficulty to a complicated
 shape of the delivery unit and is, moreover, available cost-effectively
 with virtually any desired heating power.
 It is also advantageous if the heating element is arranged on the periphery
 of the delivery unit. As a result, the heating power can be adapted in a
 simple manner, for example by the number of windings arranged radially
 around the periphery, to the heating power required for heating the washer
 fluid. At the same time, uniform heating of the delivery unit can be
 achieved via the periphery, so that material stresses owing to temperature
 differences, which may lead to damage to the delivery unit, are avoided.
 A development of the invention is designed for this in a particularly
 simple manner, in which development the delivery unit has a housing which
 has a groove in which the heating element is inserted. The heating element
 can thereby be fitted without any problem and at the same time makes
 improved transfer of heat possible by bearing extensively against the
 boundary surfaces of the groove. A standard housing which is provided with
 a groove may also, for example, be used, the housing only being provided
 with the heating element if desired.
 In this connection, it is favorable if the heating element is fixed on the
 delivery unit by means of a clip connection. This enables the outlay on
 installation to be considerably reduced, particularly with no tools of any
 kind being required. As a result, the heating element is also suitable for
 retrofitting on a delivery unit which is already present, as long as the
 delivery unit is appropriately prepared. The heating element may be
 designed for this, for example, as a hollow body which is merely pushed
 over the delivery unit.
 The heating element may be supplied independently of further heating
 elements of the washer system by a central energy source. In contrast, it
 is particularly advantageous if the heating element can additionally be
 used also to heat a connected pipe element. By this means, the outlay on
 installation is further reduced, it being possible to ensure continuous
 heating of the entire washer fluid path. The use throughout of a single
 heating element at the same time reduces possible sources of error and
 thus ensures troublefree functioning of the washer system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 FIG. 1 shows a partially cut away representation of a delivery unit 1 in a
 plan view. The delivery unit 1 has a drive 2 and a pump chamber 3 having a
 pump outlet 4. The pump chamber 3 furthermore has a heating element 5
 which is arranged on the outside on the periphery and is provided as a
 heating wire and which is inserted in a corresponding groove 6 in a
 housing 7 of the pump chamber 3. The heating element 5 is fixed in its
 shown position on the housing 7 by means of a clip connection 8 which is
 designed as a sleeve. The washer fluid entering into the pump chamber 3 is
 heated by means of the heating element 5 and thus prevents a possible
 freezing up of the washer fluid.
 FIG. 2 shows a partially cut away representation of a washer system 9
 having the delivery unit 1 shown in FIG. 1, in a front view. The housing 7
 of the pump chamber 3 with the heating element 5 arranged on the periphery
 of the housing 7 can be seen. The heating element 5 is fixed on the
 housing 7 by means of the clip connection 8 which is designed as a sleeve,
 the clip connection 8 at the same time also being used to insulate the
 heating element 5 against losses of heat to the surroundings. The pump
 outlet 4 is connected to a pipe element 10 which serves to supply a
 plurality of washer nozzles 11. In the embodiment shown, the heating
 element 5 is used both for heating the delivery unit 1 and also the pipe
 element 10, so that heating throughout and therefore high operational
 reliability can be achieved.