WO2006068561A1

WO2006068561A1 - Interval wiper and a method of controlling an interval wiper

Info

Publication number: WO2006068561A1
Application number: PCT/SE2004/001999
Authority: WO
Inventors: Carl Mannerfelt
Original assignee: Volvo Lastvagnar AB
Current assignee: Volvo Truck Corp
Priority date: 2004-12-22
Filing date: 2004-12-22
Publication date: 2006-06-29
Anticipated expiration: 2007-06-22

Abstract

The present invention relates to a vehicle windscreen wiper system (100) and a method for controlling the same. The system comprises an operator switch (110) that can assume at least two different positions, which operator switch (110) is arranged to be manually maneuverable for changing the operational mode of the wiper system (100). The system (100) also comprises a wiper motor (130) for driving at least one windscreen wiper blade (135) and a vehicle speed sensor (140) or similar for detecting the speed of the vehicle, and a control unit (120) that is coupled to said operator switch (110) for obtaining the position of the operator switch (110). The control unit (120) is also coupled to the vehicle speed sensor (140) or similar for obtaining the speed of the vehicle and to the wiper motor (130) for providing the wiper motor (130) with a signal that activates the wiper motor so that the motor operates with a wipe rate that changes depending on the vehicle speed at a selected rate that depends on the current position of the operator switch (110).

Description

INTERVAL WIPER AND A METHOD OF CONTROLLING AN INTERVAL WIPER

Field of the invention

The present invention relates to a vehicle windscreen wiper system and a method for controlling such a system. More particularly, the invention relates to a system and a method for an intermittent operation of a windscreen wiper, and even more particularly to a system and a method that are responsive to the speed of the vehicle.

Background of the invention

In conditions where a light rain is falling on a vehicle windscreen it is desirable that the vehicle windscreen wiper or wipers operate intermittently. Otherwise, leaving the wipers on continuously may e.g. cause noise, smearing and undue wear on the wiper blades. Commercially available windscreen wiper control systems provide an intermittent operational mode wherein the windscreen wiper blades will sweep intermittently. Typically, with such commercially available intermittent or time delay windscreen wiper control systems, the operator has to continually manually adjust the rate of the windscreen wiper blades in order to adapt to changing conditions. For example, as the rain intensity changes and/or as the vehicle speed changes and more or less rain impacts on the windscreen, the operator would normally decrease or increase the wipe rate. Accordingly, a windscreen wiper control system that automatically adapts to changing conditions would be desirable.

To this end, many vehicles of today are provided with a windscreen wiper control system that is responsive to a rain sensor. However, this solution will add substantial cost to the system and the solution is in principle only available in expensive top-end passenger cars. Moreover, the rain sensor has to be arranged on the windscreen in an area that is representative of the line of sight of the driver. In other words the rain sensor should preferably see the same amount of rain on the windscreen as the driver. The rain sensor is therefore preferably positioned behind the rear-view mirror, since this has proven to be a suitable compromise. However, this position for a rain sensor is not available in trucks and other vehicles that do not have any rear-view mirror. An alternative position may be found on the instrument panel at the lower end of the windscreen, or at the sides or at the upper end of the windscreen. However, these positions are less suitable since they are typically situated too far from the line of sight of the driver to represent the same amount of rain as seen by the driver. This is particularly so in connection with trucks and other vehicles with large windscreens, since the amount of rain on different areas on a large windscreen tends to deviate more than on a small windscreen. Trucks and similar vehicles may even have a protruding sunshade at the top of the windscreen that may stop or reduce the amount of rain on the upper parts of the windscreen making this area totally unsuitable for a rain sensor. Moreover, the positioning of a rain sensor in the windscreen (except behind the rear-view mirror) will reduce the driver's view through the windscreen in an unsuitable way. There are also legislations and regulations in some countries that more or less prohibit any reduction of the view through the windscreen of a vehicle.

An alternative to a windscreen wiper control system with a rain sensor may be a speed dependent windscreen wiper control system, which increases the wipe rate as the vehicle speed increases and conversely decreases the wipe rate as the vehicle speed decreases. However a typical speed dependent system can not adapt to changes that are unrelated to the vehicle speed, e.g. changes in weather conditions such as an increased or decreased rain intensity etc.

Consequently, there is a need for an inexpensive windscreen wiper control system that can adapt to changing conditions in a more efficient way.

Summary of the invention

The invention provides for a vehicle windscreen wiper system and a method for controlling the same, which system and method provides a wipe rate that is changing a selected rate as the vehicle speed is changing, which selected rate depends on the current position of an operator switch or similar.

This is achieved by a vehicle windscreen wiper system that comprises an operator switch that is capable of assuming at least two different positions, which operator switch is arranged to be manually maneuvered for changing the operational mode of the wiper system. The system also comprises a wiper motor for driving at least one windscreen wiper blade, and a vehicle speed sensor or similar for detecting the speed of the vehicle, and a control unit that is coupled to said operator switch for obtaining the position of the operator switch. The control unit is also coupled to the vehicle speed sensor or similar for obtaining the speed of the vehicle and to the wiper motor for activating the wiper motor. The control unit is moreover arranged to provide the wiper motor with a signal that activates the wiper motor so that the motor operates with a wipe rate that changes depending on the vehicle speed, which changes is performed at a selected rate that depends on the current position of the operator switch.

Moreover, the invention provides for a method for controlling the vehicle windscreen wiper system.

The method is performed by the basic steps of: - obtaining the current position of the operator switch and the current vehicle speed,

- determining a wipe rate depending on the vehicle speed and a selected rate that depends on the current position of the operator switch,

- activating the wiper motor so as to operate at the determined wipe rate.

Further advantages of the present invention and embodiments thereof will appear from the following detailed description of the invention.

Brief description of the drawings

Fig. 1 shows a schematic illustration of a windscreen wiper control system 100 according to an exemplifying embodiment of the present invention.

Fig. 2a illustrates a diagram showing a first exemplifying operation mode of the windscreen wiper control system 100 in fig. 1.

Fig. 2b illustrates a diagram showing a second exemplifying operation mode of the windscreen wiper control system 100 that improves the wipe function at low or zero vehicle speed.

Fig. 2c illustrates a diagram showing a third exemplifying operation mode of the wiper control system 100 that even further improves the wipe function at low or zero vehicle speeds. Fig. 3 shows a flowchart that illustrates an exemplifying operation of the windscreen wiper control system 100 in fig. 1. Detailed description of preferred embodiments of the invention

The invention will be described in more detail below with reference to an exemplifying windscreen wiper control system. Other embodiments of the invention are clearly conceivable and the invention is by no means limited to the exemplifying windscreen wiper control system described below.

The Wiper Control System

Figure 1 shows a schematic illustration of a windscreen wiper control system 100 according to an exemplifying embodiment of the present invention. The wiper control system 100 comprises an operator switch 110, a control unit 120, a wiper motor 130 and a vehicle speed sensor 140. The control unit 120 is coupled to the operator switch 110, to the wiper motor 130 and to the vehicle speed sensor 140 for enabling an operational communication between said units 110-140.

The wiper motor 130 is adapted to be provided with a suitable wiper blade arrangement comprising one or several wiper blades 135. A wiper blade 135 is schematically illustrated by a solid line in figure 1 and a contemplated sweep area of the wiper blade 135 is schematically enclosed by dashed lines in figure 1.

It is preferred that the control unit 120 includes a programmable microprocessor (not shown) and memory means (not shown) for storing the microprocessor program and/or possibly temporary results from the execution of the microprocessor program and/or any other data that is produced during operation of the control unit 120. It is also preferred that the control unit 120 includes suitable interfaces, which enables an appropriate communication with the operator switch 110, the wiper motor 130 and the vehicle speed sensor 140. The control unit 120 may be arranged in any suitable space in the vehicle, even within the wiper motor 130. The control unit 120 may be a stand-alone unit or it may be integrated in an electronic control unit already present on the vehicle.

However, the invention is not limited to the exemplifying control unit 120 describe above. On the contrary, the control unit may be designed by means of discrete electrical components such as separate transistors, or by means of electro-mechanical components such as relays, or even by means of a suitable combination of integrated circuits (e.g. a microprocessor and memory), discrete electrical components and electro mechanical components. The operator switch 110 in figure 1 has been schematically illustrated as having five different positions, i.e. positions 1-5 schematically indicated by five small circles in figure 1. It is preferred that the five positions represent different operational modes according to which the wiper motor 130 is commanded by the by the control unit 120 to operate at different wipe rates, i.e. commanded to sweep the wiper blade 135 across the windscreen according to different rates, e.g. one sweep per second or any other wipe rate that can be accomplished by the wiper control system 100 in question.

However, the invention is not limited to an operator switch 110 as describe above. On the contrary, the operator switch may e.g. have a smaller or a greater number of positions.

The operator switch may also be of several different types, e.g. a turnable switch, a sliding switch or any other suitable switch, e.g. a spring back push button that can be repeatedly pushed in one direction so as to stepwise increase the sweep rate, and pushed repeatedly in another direction so as to stepwise decrease the wipe rate. The operator switch 110 is preferably arranged at an easily accessible location within the passenger compartment of the vehicle so that the positions or similar of the operator switch 110 can be selected without any effort by the driver of the vehicle.

The speed sensor 140 in figure 1 may e.g. be a conventional speedometer arrangement as described in the patent US 6,771,063 (Stolfus), which comprises a sensor ring provided with cogs of a magnetic material and an electromagnetic sensor coil arranged to detect each cog as they pass in front of the sensor coil. The speed sensor 140 can e.g. be arranged on the tail shaft of the vehicle transmission or at one of the vehicle road wheels.

The speed sensor 140 provides a pulsed output for each cog that passes in front of the sensor coil, where the number of pulses per time unit is a measure of the vehicle speed.

The patent US 5,422,568 (Hashizume) discloses a similar conventional speedometer that comprises a Hall-sensor that is associated with a rotor. A plurality of small permanent magnets have been arranged around the rotor with their poles in alternating directions so as to produce an alternating magnetic field as they pass the Hall-sensor when the rotor is rotated. The Hall-sensor produces an alternating signal as a result of the changes in magnetic flux caused by the passing permanent magnets.

However, the invention is not limited to any of the speed sensors describe above. On the contrary, the speed sensor 140 may be any suitable vehicle speed sensor. The vehicle speed may even be retrieved from a vehicle apparatus or a vehicle function or similar that in turn has retrieved the speed information from a vehicle speed sensor or similar.

The wiper motor 130 in figure 1 may be any suitable wiper motor. The wiper motor itself may e.g. be provided with an intelligent functionality that is arranged to receive a command from the control unit 120. Such a command may e.g. comprise information about the number of sweeps of the wiper blade 135 across the windscreen to be performed by the motor each time the motor is activated, the sweep velocity, the sweep angle etc. Other wiper motors may be arranged to merely receive an electrical drive power from the control unit 120. In such cases it is preferred that the wiper motor provides the control unit 120 with the current position of the wiper blade 135, which enables the control unit 120 to determine when to return the wiper blade 135 (e.g. by changing the polarity of the electrical drive power) after a sweep across the windscreen. The current position of the wiper blade 135 may also be useful in determining when to reduce or cut-off the drive power to let the wiper blade 135 slow down before and/or rest in an end position etc. Exemplifying windscreen wiper motor arrangements can e.g. be found in the patent document US 6,819,067 {Grass) or in the patent document US 6,800,978 (Bohn).

The Operation of the Wiper Control System

Exemplifying operation modes of the windscreen wiper control system 100 will now be described with reference to figures 2a-2c and figure 3. In particular, a plurality of intermittent operation modes will be described that depends on the vehicle speed and the position of the operator switch 110 selected by the driver.

Figure 2a illustrates a diagram showing a first exemplifying operation mode of the windscreen wiper control system 100 in figure 1. The diagram in figure 2a has a vertical axis y that represents the wipe rate of the windscreen wiper control system. 100 and a horizontal axis x that represents the speed of the vehicle in which the wiper control system 100 is operationally arranged. The diagram in figure 2a comprises five different graphs Lla-L5a. Each of the graphs Lla-L5a corresponds to one of the five positions of the operator switch 110 in figure 1.

The positions of the operator switch 110 are arranged to be manually selected by the driver of the vehicle so that a first position of the switch corresponds to the first graph LIa in said diagram and a second position corresponds to the second graph L2a, a third position corresponds to the third graph L3a and a fourth position corresponds to the fourth graph L4a and finally a fifth position corresponds to the fifth graph L5a in said diagram. As can be seen in figure 2a the graphs Lla-L5a have different inclinations. This implies that the wipe rate of the wiper control system 100 will increase at different rates as the speed of the vehicle increases and that the increase rate depends on the position of the operator switch 110 selected by the driver. Hence, the driver may select a lower increase rate of the wipe rate (e.g. according to the graph LIa) when the rain intensity is low and a higher increase rate of the wipe rate (e.g. according to the graphs L2a-L5a) when the rain intensity is higher. This enables the driver to manually select a wipe rate that, depending on the present rain intensity, increases at a lower or higher rate as the vehicle speed increases, i.e. to manually select a wipe rate that, depending on the present weather condition, increases at a certain rate as the vehicle speed increases.

The wipe rate represented by the graphs Lla-L5a in figure 2a is increasing from a zero wipe rate to the maximum wipe rate W_max in an approximately linear fashion, which can be represented by the expression:

Wipe Rate = Cx Vehicle Speed [1]

wherein, the constant C corresponds to the specific inclination of the graphs LIa-LSa, i.e. the selected rate according to which the wipe rate is changing as the vehicle speed is changing, which selected rate depends on the current position of the operator switch (110).

Hence, the wipe rate represented by the graphs Lla-L5a in figure 2a is low or equal to zero when the vehicle speed is low or equal to zero, which in turn means that no or little water is wiped from the windscreen at these vehicle speeds. This may not be a problem when the rain intensity is low, since the rainwater is then typically accumulating slowly on the windshield, especially when the vehicle is moving slowly or is standing still. However this can certainly be a problem when the rain intensity is high, since the rainwater is then accumulating fast on the windshield.

The attention is therefore turned to figure 2b, which illustrates a diagram showing a second exemplifying operation mode of the windscreen wiper control system 100 that improves the wipe function at low or zero vehicle speed. The diagram in figure 2b is the same as the previously described diagram in figure 2a and the diagram comprises five different graphs Llb-L5b that each corresponds to one of the five positions of the operator switch 110 in the same way as the graphs Lla-L5a in figure 2a. As can be seen in figure 2b the graphs Llb-L5b have different inclinations in a similar way as previously described in connection with the graphs Lla-L5a in figure 2a, which means that the wipe rate will increase at different rates as the speed of the vehicle increases and that the rate depends on the position of the operator switch 110 selected by the driver.

However, each of the graphs L2b-L5b in figure 2b represents different wipe rates that are above zero when the vehicle speed is low or zero, as a contrast to the graphs Lla-L5a in figure 2a which all represent a zero or near wipe rate when the vehicle speed is low or zero. Hence, the operational mode according to the graphs L2b-L5b in figure 2b provides an intermittent wipe rate that can be adapted by the driver even at low or zero vehicle speeds, e.g. adapted to the present rain intensity. Hence, the driver may select a higher initial wipe rate at said low or zero vehicle speed (e.g. according to the graphs L2b-L5b) when the rain intensity is high, and a lower initial wipe rate at said low or zero vehicle speed (e.g. according to the graph Lib) when the rain intensity is low.

The wipe rate represented by the graphs Llb-L5b in figure 2b is increasing from a near zero wipe rate to the maximum wipe rate in an approximately linear fashion, which can be represented by the expression :

Wipe Rate = Cx Vehicle Speed + M [2]

wherein, the constant C corresponds to the specific inclination of the graphs Llb-L5b, i.e. the selected rate according to which the wipe rate is changing as the vehicle speed is changing, which selected rate depends on the current position of the operator switch 110, while the M corresponds to the initial wipe rate represented by the graphs LIb-LSb at a zero vehicle speed, which initial wipe rate depends on the current position of the operator switch 110.

The attention is now turned to figure 2c, which illustrates a diagram showing a third exemplifying operation mode of the wiper control system 100 that even further improves the wipe function at low or zero vehicle speeds. The diagram in figure 2c is the same as the diagram previously described in connection with figures 2a and 2b. The diagram in figure 2c comprises five different graphs Llc-L5c that each corresponds to one of the five positions of the operator switch 110 in a substantially same way as the graphs Lla-L5a and Llb-5b in figure 2a and 2b.

However, each of the graphs Llc-L5c in figure 2c represents different constant initial wipe rates that are above zero when the vehicle speed is within an interval from a zero vehicle speed to a specific low threshold vehicle speed V_min. The value of V_mm may e.g. be 15-20 km/h, though higher or lower speeds are clearly conceivable. This is in contrast to the graphs L2b-L5b in figure 2b, which all represents an increase in the wipe rate immediately when the vehicle speed is above zero, i.e. the graphs L2b-L5b do not represent a constant initial wipe rate.

As can be seen in figure 2b the graphs LIc-LSc that represent different constant initial wipe rates continues with different inclinations for the vehicle speeds that are above the threshold vehicle speed V_m]n, which inclinations represents the same function as previously described in connection with the graphs Lla-L5a and Llb-L5b, i.e. that the wipe rate will increase at different rates as the speed of the vehicle increases above V_min and that the rate depends on the position of the operator switch 110 selected by the driver.

The wipe rate according to the graphs Llc-L5c in figure 2c is increasing from different constant wipe rates to the maximum wipe rate in a discontinuous fashion, which can be represented by the following expression:

f M , for 0 < VehickSpeed ≤ V -

WipeRαte = \ ' ^ " [3]

[M + C -

), for F_101n < VehicleSpeed

wherein, M corresponds to the initial wipe rate represented by the graphs Llc-L5c at vehicle speeds from zero to V_mm, which initial rate depends on the current position of the operator switch 110, while the constant C corresponds to the specific inclinations of the graphs Llc-L5c at vehicle speeds equal to or above V_mln, i.e. the selected rate according to which the wipe rate is changing as the vehicle speed is changing, which selected rate depends on the current position of the operator switch 110.

A constant initial wipe rate at low vehicle speeds as represented by the graphs Llc-L5c is particularly advantageous as many speed sensors have difficulties in accurately measuring the vehicle speed at low speeds. For example, in pulsed speed sensors as those described in the patent documents US 6,771,063 (Stolfus) and US 5,422,568 (Hashizume) mentioned above there may be too few pulses available to accurately and steadily produce a correct measurement of the vehicle speed at low speeds. The measured speed may then fluctuate and cause changes in the wipe rate that can be perceived by the driver as disturbing and/or as a malfunction. This can be avoided by using different constant initial wipe rates at vehicle speeds below V_mln as illustrated by the graphs Llc-L5c in figure 2c.

It should be added that the wipe rate represented by the graphs Lla-L5a, Llb-L5b and Llc-L5c in figures 2a-2c can not increase above a certain maximum wipe rate W_max as indicated in figures 2a-2c, which typically corresponds to the maximum continuous wipe rate that can be practically achieved by the wiper system in question. The maximum wipe rate is typically limited by such parameters as the performance of the wiper motor 130, the structural strength of the parts in the wiper system, the highest wipe rate above which the efficiency of the wipe function decreases and/or becomes disturbing to the driver etc. The increase of the wipe rate according to the selected rate (e.g. according to Lla-L5a, Llb-L5b or Llc-L5c) ends when the vehicle speed reaches the point that corresponds to the maximum wipe rate. The wipe rate is subsequently decreased according to the same selected rate (e.g. according to Lla-L5a, Llb-L5b or LIc-LSc) when the vehicle speed is decreased.

The adaptable wipe rate as described above with reference to figures 2a-2c is preferably accomplished by the control unit 120. The adaptable wipe rate can e.g. be defined in a table arrangement or by a mathematic formula or similar that may be stored in an suitable memory or similar, by means of which the control unit 120 can retrieve a suitable value for the command or the drive power or similar signal that is to be sent to the wiper motor 130 depending on the position of the operator switch 110 and the vehicle speed detected by the speed sensor 140.

However, the invention is not limited to the use of tables or mathematic formulas or similar. On the contrary, the adaptable wipe rate may be defined by any suitable means that enables a command or a suitable drive power or similar to be sent to the wiper motor 130 depending on the position of the operator switch 110 and the vehicle speed detected by the speed sensor 140.

Figure 3 shows a flowchart that illustrates an exemplifying operation of the windscreen wiper control system 100 in figure 1.

The system is initialized in A during the start-up of the vehicle. The first step 200 according to the flowchart in figure 3 is to obtain the current vehicle speed and the current position of the operator switch 110 that has been selected by the driver.

The second step 210 is more or less an optional step according to which the control unit 120 may check if the operator switch 110 or similar is in a position according to which an intermittent wipe function is requested. The operation will then continue to the subsequent step 220 if an intermittent wiper function has been requested. However, the operation will continue to the last step 240 if an intermittent wiper function has not been requested. Step 240 will be described below.

The third step 220 is to determine a wipe rate that depends on the vehicle speed and the current position of the operator switch 110. For example, the wipe rate in the exemplifying operation modes described above with reference to figures 2a-2c is determined according to one of the graphs Lla-L5a, Llb-L5b or Llc-L5c selected by the driver as he positions the operator switch 110.

The fourth step 230 is to activate the wiper motor 130 to operate at the determined wipe rate. As previously indicated, this is preferably accomplished by letting the control unit 120 send an appropriate command or drive power or similar signal to the wiper motor 130, which signal corresponds to the determined wipe rate.

The fifth step 240 is to execute a delay before the operation returns to the first step 210. The delay may be composed by a basic delay that is added to a determined delay that corresponds to the wipe rate that was determined at the third step 220, which determined delay e.g. is long enough to allow the completion of a sweep of the wiper blade 135 over the windscreen. The delay may as an alternative or as a supplement depend on the position of the wiper blade 135, which e.g. enables a delay that corresponds to a sweep of the wiper blade 135 over the windscreen by a detection of the position of the wiper blade

135 during the sweep.

The present invention has now been described by means of preferred embodiments. However, the invention is not limited to the embodiments described above. On the contrary, the operation of the windscreen wiper control system 100 illustrated by the flowchart in figure 3 may for example comprise further steps and/or steps that are performed according to another sequence than the one described in connection with figure 3. Moreover, the exemplifying windscreen wiper control system 100 may comprise more units or similar in addition to the ones illustrated in figure 1.

Reference signs

100 Windscreen Wiper Control System

110 Operator Switch 120 Control Unit

130 Wiper Motor

135 Wiper Blade

140 Speed Sensor / Speedometer

Claims

Patent Claims

1. A vehicle windscreen wiper system (100) comprising; an operator switch (110) arranged to assume at least two positions for changing the operational mode of the wiper system (100), a wiper motor (130) for driving at least one windscreen wiper blade (135), a vehicle speed sensor (140) for detecting the speed of the vehicle, and a control unit (120) that is coupled to; the operator switch (110) for obtaining the position of the operator switch (110), the vehicle speed sensor (140) for obtaining the speed of the vehicle, the wiper motor (130) for activating the wiper motor (130), wherein: said control unit (120) is arranged to provide the wiper motor (130) with a signal that activates the wiper motor (130) so as to operate with a wipe rate that changes depending on the vehicle speed at a selected rate that depends on the current position of the operator switch (110).

2. A vehicle windscreen wiper system (100) according to claim 1; wherein: said control unit (120) is arranged to provide the wiper motor (130) with a wipe rate that correspond to an intermittent sweeping of the wiper blade (135) at vehicle speeds that are below a vehicle speed that correspond to a maximum sweep rate, and a wipe rate that correspond to a continuous sweeping of the wiper blade (135) at vehicle speeds that are equal to or above a vehicle speed that correspond to a maximum sweep rate.

3. A vehicle windscreen wiper system (100) according to claims 1-2; wherein: said control unit (120) is arranged to provide the wiper motor (130) with a wipe rate that changes depending on the vehicle speed at a substantially continuous rate.

4. A vehicle windscreen wiper system (100) according to claim 1-3; wherein: said control unit (120) is arranged to provide the wiper motor (130) with a wipe rate that changes according to the expression:

Wipe Rate = Cx Vehicle Speed wherein, C correspond to the selected rate according to which the wipe rate is changing as the vehicle speed is changing, which selected rate depends on the current position of the operator switch (110).

5. A vehicle windscreen wiper system (100) according to claim 4; wherein: said control unit (120) is arranged to provide the wiper motor (130) with a wipe rate that changes according to the expression:

Wipe Rate = C x Vehicle Speed + M wherein, M corresponds to an initial wipe rate at zero vehicle speed, which initial wipe rate depends on the current position of the operator switch (110).

6. A vehicle windscreen wiper system (100) according to claims 1-2; wherein: said control unit (120) is arranged to provide the wiper motor (130) with a wipe rate that changes according to the expression:

_ f M , for 0 < VehicleSpeed ≤ V^ ⁱpe ^{αte ~} |_{M + c} . (j/_ehic!eSpeed - V_x^ ) , for F_n^ < VehicleSpeed

wherein M corresponds to an initial wipe rate at vehicle speeds from zero to V_mι_n, which initial wipe rate depends on the current position of the operator switch (110), and C corresponds to a selected rate according to which the wipe rate is changing as the vehicle speed is changing at vehicle speeds that are equal to or above V_m|_n, which selected rate depends on the current position of the operator switch (110).

7. A method for controlling a vehicle windscreen wiper system (100) comprising; an operator switch (110) arranged to assume at least two positions for changing the operational mode of the wiper system (100), a wiper motor (130) for driving at least one windscreen wiper (135), a vehicle speed sensor (140) for detecting the speed of the vehicle, and a control unit (120) that is coupled to; the operator switch (110) for obtaining the position of the operator switch (110), the vehicle speed sensor (140) for obtaining the speed of the vehicle, the wiper motor (130) for activating the wiper motor (130), which method is performed by the steps of:

- obtaining the current position of the operator switch (110) and the current vehicle speed, determining a wipe rate depending on the vehicle speed and a selected rate that depends on the current position of the operator switch (110), - activating the wiper motor (130) so as to operate at the determined wipe rate.

8. A method according to claim 7; wherein: said wipe rate is determined so as to correspond to an intermittent sweeping of the wiper blade (135) at vehicle speeds that are below a vehicle speed that corresponds to a maximum sweep rate, and so as to correspond to a continuous sweeping of the wiper blade (135) at vehicle speed that are equal to or above a vehicle speed that correspond to a maximum sweep rate.

9. A method according to claims 7-8; wherein: said wipe rate is determined so as to change depending on the vehicle speed at a substantially continuous rate.

10. A method according to claim 9; wherein: said wipe rate is determined according to the expression:

Wipe Rate = Cx Vehicle Speed wherein, C corresponds to the selected rate according to which the wipe rate is changing as the vehicle speed is changing, which selected rate depends on the current position of the operator switch (110).

11. A method according to claim 10; wherein: said wipe rate is determined according to the expression: Wipe Rate = C x Vehicle Speed + M wherein, M corresponds to an initial wipe rate at zero vehicle speed, which initial wipe rate depends on the current position of the operator switch (110).

12. A method according to claims 7-8; wherein: said wipe rate is determined according to the expression:

f M , for O ≤ VehicleSpee d ≤ V^

WipeRαte = { , _N

[M + C - {VehicleSpeed - V^J, for V_n^ < VehicleSpeed

wherein M corresponds to an initial wipe rate at vehicle speeds from zero to V_min, which initial wipe rate depends on the current position of the operator switch (110), and C corresponds to a selected rate according to which the wipe rate is changing as the vehicle speed is changing at vehicle speeds that are equal to or above V_π,_in, which selected rate depends on the current position of the operator switch (110).