Abstract:
A control device for the drive motor of a windscreen wiper device in a vehicle, especially a motor vehicle, comprising a control switch which can be activated by means of a manually actuated wiper switch and which automatically controls the drive motor in a switching stage of said wiper switch according to a rain sensor signal corresponding to a characteristic curve. The operating data for the drive motor varies according to the external effects of lighting, temperature, or speed parameters.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a control device for the drive motor of a windshield wiper device on a vehicle, in particular a motor vehicle, comprising a control circuit that can be activated by a manually operated wiper switch and automatically controls the drive motor in one switching stage of the wiper switch in accordance with a characteristic curve and depending on a signal from a rain sensor. 
     The control device taken into consideration for the drive motor control of a windshield wiper device in a motor vehicle comprises a control circuit, which can be activated by means of a manually activated wiper switch. The wiper switch assigned to the steering column of the vehicle has a multi-stage design. In a first switching stage of the wiper switch, the drive motor for the windshield wiper device is controlled by a characteristic curve, which is scanned in dependence on the signal from a rain sensor and controls the drive motor accordingly. In the process, the operating data deposited for the drive motor contain the control information that the drive motor is operated intermittently in the starting range of the characteristic curve. Depending on the amount of rain hitting the windshield, which is detected by the rain sensor, the interval time between each wiping cycle is reduced if the rain amount increases. The drive motor is switched to the continuous operation if the value for the interval time falls below a predetermined value, wherein its speed initially is at a minimum. With increasing amounts of rain, the speed is then increased by the control until it reaches a maximum speed with a correspondingly increased number of wiping cycles per time unit. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to specify measures for a control device of the type described above, which permit an optimum wiper operation for different influences effecting the vehicle, particularly brightness, temperature, blinding by other traffic participants or light sources and/or driving speed. 
     This object generally is solved according to the invention by a control device for the drive motor of a windshield wiper device on a vehicle, in particular a motor vehicle, comprising a control circuit that can be activated by a manually operated wiper switch and automatically controls the drive motor in one switching stage of the wiper switch in accordance with a characteristic curve and depending on a signal from a rain sensor, and wherein the operating data for the drive motor can be changed in dependence on the effects of lighting and/or temperature and/or driving speed that act upon the vehicle from the outside. Further embodiments are specified and/or discussed in the description. 
     In an embodiment of a control device according to the invention, a predetermined standard characteristic curve is replaced with a predetermined limit characteristic curve, depending on light and/or temperature influences that effect the vehicle from the outside, so that the operating data for the drive motor of the windshield wiper can be changed. In particular, a change in the operating data is planned if environmental conditions, gespecially brightness, temperature and/or speed, respectively deviate from a predetermined limit value and in particular if they fall below this value. 
     The wiper switch is preferably provided with several switching stages for this, wherein the automatic characteristic curve operation is assigned to the first switching stage and one or several fixed speed(s) is (are) assigned to one or several additional switching stages. If the values fall below the limit values for temperature and/or light intensity during the windshield wiper operation, a limit characteristic curve that is changed relative to the standard characteristic curve is provided in the control circuit, wherein the characteristic curves have a fixed upper end point. A preferred limit value for the light intensity in this case is the light intensity that normally exists while the vehicle driving lights are turned on, which results in the danger of blinding. A preferred limit value for the temperature is the temperature around the freezing point because it is to be expected that water mixed with salt hits the vehicle windshield, which can lead to a smearing of the windshield during the wiper operation, thus increasing the danger of blinding and/or reducing the visibility. 
     The transition from the standard characteristic curve to the limit characteristic curve in that case can occur at least quasi-continuously via intermediate characteristic curves between the standard characteristic curve and the limit characteristic curve. The intermediate characteristic curves, standard characteristic curve and limit characteristic curve all have a fixed upper end point (M). The speed of the transition from a standard characteristic curve to a limit characteristic curve advantageously depends on the degree to which the temperature and/or light intensity deviate from the respective limit values. Thus, the wiper operation is at an optimum if possible even during twilight hours and/or with slowly dropping or increasing temperatures. However, the transition from the standard characteristic curve to the changed limit characteristic curve can also be abrupt. 
     If the light intensity that affects the vehicle is below a predetermined light intensity, the drive motor speed is increased and/or interval pauses of the wiper operation are shortened and/or the transition from intermittent operation to continuous operation is shifted to lower rain amounts. It is useful if the drive motor speed is lowered for temperatures below a limit temperature and/or the interval pause time of the wiper operation is increased and/or the transition from intermittent to continuous wiper operation is shifted to higher rain amounts. Given a light intensity and temperature below the respective limit values, it is advantageous if the drive motor speed as well as the interval pauses of the wiper operation are increased and/or the transition from intermittent operation to continuous wiper operation is shifted to lower rain amounts. It is particularly favorable if the wiper operation with windshield-washing function is controlled in a corresponding manner. 
     For one advantageous modification of a control device, an adaptive characteristic curve for the wiping operation is additionally generated, which is changed by means of manually operated control means if it does not meet the individual requirements of the motor-vehicle user. For this, the pause time between two wiper operations can be changed during the intermittent operation and/or the drive motor speed or the wiping frequency can be increased or lowered during the subsequent, continuous wiper operation. The wiper switch is preferably provided with the standard three switching stages, wherein the automatic characteristic curve operation is assigned to the first switching stage, while one or several fixed speed(s) is (are) assigned to the one or several additional switching stage(s). The operating data predetermined by the manufacturer for controlling the drive motor for the windshield wiper device are programmed to meet average requirements. After switching on the automatic characteristic curve operation, an intermittent operation with long pause times is controlled automatically for small rain amounts, depending on the amount of rain per time unit that is detected by a rain sensor. The pause times will decrease with increasing amounts of rain. If the rain amounts increase even further, the drive motor will change to a continuous operation, wherein the speed is increased up to a maximum value if the amount of rain increases accordingly. 
     If the specified characteristic curve does not control a wiper characteristic that meets the personal ideas of the driver, the characteristic curve can be changed by switching on additional switching stages of the wiper switch. If, for example, the pause times during the intermittent operation are too long or the wiper frequency during the continuous operation is too low, the wiper switch must only be switched to one of the additional stages with the fixed, predetermined speeds. This switching measure is recorded in the control unit and the slope of the characteristic curve is reduced by means of an adaptation algorithm control, triggered by this measure. The end point of the characteristic curve remains at least for the most part fixed in the maximum operating point of the drive motor. As a result of this pivoting upward of the characteristic curve, around the maximum operating point, the operating data assigned to this characteristic curve for the drive motor are changed in such a way that the pause times during the intermittent operation are respectively shortened and the drive motor speed or the windshield wiper wiping frequency in the characteristic curve segment of the continuous operation is raised. A switching of the wiper switch from stage  1  to stage  2  can cause a specified change. In contrast, a switching through from stage  1  to stage  3  makes it possible to control a stronger raising of the characteristic curve. As a result of a repeated switching back and renewed switching up of the wiper switch, a stage-by-stage raising of the characteristic curve or the stage-by-stage reduction of the increase by means of the algorithm control can be effected. A switching back of the wiper switch to the first switching stage for the automatic operation thus always makes available a characteristic curve that approaches the driver needs for a rain-dependent control of the windshield wiper device. 
     On the other hand, if the operating data supplied to the drive motor by the rain-dependent operating point data result in a wiping sequence that is too high for the individual requirements of the driver, the data for the characteristic curve can be changed back through a steeper increase in the slope of the characteristic curve, longer pause times for the intermittent operation, and a slower wiping frequency in the superimposed characteristic curve range. It is assumed that the actual characteristic curve for the automatic, rain-amount dependent operation is actuated in a range that is above the number of wiping cycles or the drive motor speed and is fixedly predetermined by position  2  of the wiper switch. Thus, if the user of the wiper switch switches from the switching position  1  for the automatic operation to the switching position  2 , the operating data specified by the switching position  2  are below the data specified by the actual characteristic curves. The control signal obtained in this way causes a reduction of the operating data in the algorithm control, not only for this operating point, but for the complete characteristic curve. In the process, the operating point of the characteristic curve, which is assigned to the highest, detected rain amount, remains again unchanged. A new characteristic curve can be determined for this in each case, or it is possible to switch to one of several fixedly predetermined characteristic curves. Furthermore, if the wiper switch is turned to the zero position during the operation and the rain sensor still signals a rain amount worth mentioning to the control circuit, a control command obtained in this way can be used to change the slope of the characteristic curve or to change the curve course, such that the pause times during the intermittent operation are increased and the continuously occurring wiping cycles in the upper range of the characteristic curve are reduced. 
    
    
     In the following, the invention is explained further with the aid of basic diagrams. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is switching diagram for a control device for a windshield wiper device according to the invention. 
     FIG. 2 shows a basic diagram for changing a characteristic curve assigned to a control device according to the invention. 
     FIG. 3 is a modification of the A switching diagram of FIG. 1 for a control device of a windshield wiper device according to the invention. 
     FIG. 4 shows a basic diagram for changing a characteristic curve assigned to an advantageous modification of the control device according to the invention. 
     FIG. 5 shows a characteristic curve with different operating points. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a control device for a drive motor  11 , which impresses back and forth wiping cycles onto windshield wipers  13  with the aid of a gear  12 . The windshield wipers  13  rest on a windshield  14  to be wiped, to which a rain sensor  15  is assigned. The rain sensor  15  supplies an electric control signal, which depends on the amount of rain per time unit, which hits the area of the windshield that is covered by the sensor. The rain-dependent control signal is supplied to a control circuit  16 . With a measuring unit  17 , the control circuit  16  can determine the actual speed of the windshield wiper motor  11  and thus also the number of wiping cycles. A switch for a windshield-washing device  20  is arranged as additional input unit, and a wiper switch  18  is connected directly or via a bus system to the control circuit  16 . Normally, this switch is mounted as steering column switch on the steering column of the respective vehicle and, in addition to the zero position for shutting down the drive motor  11 , contains additional switching stages  1 ,  2 ,  3  for switching up or down, in accordance with the various operating states. An optical sensor  21 , which is preferably arranged on the windshield and adjacent to the rain sensor  15 , determines the brightness of the surrounding area and/or the blinding. It is advantageous if the rain sensor as well as the sensors for determining the brightness and blinding are combined to form a single optical sensor. A temperature sensor  22  transmits the determined outside temperature values to the control circuit  16 . The characteristic curve stored in the control circuit  16 , which describes the connection between rain amount and wiping speed or interval pause time, is adapted in dependence on the data provided by the sensors  21  and  22 , such that the highest optimum wiping speed is adjusted. 
     In a first switching stage  1 , the drive motor  11  is controlled during daylight in accordance with a characteristic curve  30 . This curve is deposited in the control circuit  16  as standard characteristic curve  30  for daylight and specifies operating data for the drive motor  11  in dependence on the amount of rain determined by the rain sensor  15 , which is shown in FIG. 2 a . Based on the operating data deposited with the characteristic curve  30 , the drive motor  11  is operated intermittently if the rain sensor  15  detects a small rain amount. In that case, a pause occurs after each wiping cycle, consisting of a back and forth movement of the windshield wiper  13 , until the following wiping cycle occurs. With increasing amounts of rain, the respective pause time is shortened. As soon as the pause time falls below a specified value, a continued operation of drive motor  11  with low speed is controlled by the characteristic curve  30  if the rain amount is correspondingly increased. If the detected rain amount increases even further, the drive motor  11  speed is also adjusted to higher values until it reaches its maximum value M for high rain amounts. With a decreasing rain amount, the drive motor  11  is controlled in the opposite direction. The characteristic must be shifted with decreasing light intensity for an adaptation of the characteristic line to the surrounding brightness. For this, the interval pause times must be shortened and the transition between intermittent wiping operation and continuous wiping operation must be shifted toward lower degrees of wetting or rain amounts and the characteristic curve for the continuous wiping must be raised. It means that the wiping speed must be increased if the wetting of the windshield remains constant but the darkness increases. If a value falls below a predetermined limit value for the light intensity, it is possible to switch from a standard characteristic curve  30  for daylight to a limit characteristic curve  31  for nighttime. With the adaptation of the characteristic curve, the point M that represents the maximum motor  11  speed preferably remains unchanged. However, a characteristic curve adaptation for which this point is changed is also possible. 
     By taking into account the outside temperatures, which can be determined in or on the vehicle with a temperatures sensor  22 , the standard characteristic curve for the wiping operation can be lowered, which is shown in FIG. 2 b . Given a constant degree of wetting or a constant rain amount, the wiping speed is reduced below a limit temperature, preferably near the freezing point (0° C.). In that case, the temperature is only an indication that salt is present with a high probability on the driving surface. This salt is kicked up by other vehicles and hits the windshield  14 , resulting in the danger of smearing the windshield  14  during the wiping operation. 
     If the wiper must be used during darkness and at temperatures below the freezing point, one of the operating states darkness or cold, meaning salt on the driving surface, must be given precedence. 
     Different vehicle speeds lead to different drop sizes on the windshield. In order to obtain an optimum wiping function, it is therefore useful to provide the driven speed and/or the average drop size on the windshield  14  of the vehicle as additional input value(s) for the adaptation of the characteristic curve. 
     It is favorable if the characteristic curve adaptation is also used for the washing function of wiper switch  18 . In that case, one or several washing cycles are triggered with additional wetting of the windshield. 
     The transition from the standard characteristic curve  30 ,  33  to the limit characteristic curve  31 ,  34  can be adapted so-to-speak continuously, preferably via the intermediate characteristic curves between the standard characteristic curve  30 ,  33  and the limit characteristic curve  31 ,  34 , to the slowly changing brightness and/or the temperature, or it can be switched abruptly if the value falls below the limit value. 
     Another advantageous measure provides for a change in the drive motor  11  speed, not only during the switching stage I with automatic operation, but in at least one other switching position, particularly the switching stage  2  (so-called switching stage  1  of the wiper) and/or  3  (so-called stage II of the wiper). For the night-time operation, it is advantageous if the speed is raised in stage I, for example from 40 cycles/minute to 45 cycles/minute. 
     A control device for a drive motor  11  impresses back and forth wiping movement cycles (FIG. 3) onto the windshield wipers  13  by means of a gear  12 . Temperature sensor  22  and light sensor  21  from FIG. 1 are not shown in further detail herein. The windshield wipers  13  rest on a windshield  14  to be wiped, to which a rain sensor  15  is assigned. The rain sensor  15  delivers an electric control signal, which depends on the amount of rain per time unit that hits the windshield area covered by the sensor. The control signal that depends on the rain amount is supplied to a control circuit  16 . With a measuring unit  17 , the control circuit  16  can determine the actual speed of the windshield wiper motor  11  and thus the wiping cycles. In addition, a wiper switch  18  is connected as input unit directly or via a bus system to the control circuit  16 . This switch is normally mounted as steering column switch on the steering column of the respective vehicle and, in addition to a zero position for shutting down the drive motor  11 , also contains the switching stages  1 ,  2 ,  3  for switching back and forth in accordance with different operating states. In a first switching state  1 , the drive motor  11  is controlled on the basis of a characteristic curve  19 , which is deposited in the control circuit  16  and specifies operating data for the drive motor  11  in dependence on the amount of rain determined by the rain sensor  15 . The characteristic curve  19  corresponds to standard characteristic curves such as the characteristic curves  30 ,  33  as well as the limit characteristic curves  31 ,  34 . Based on the operating data deposited in the characteristic curve  19 , the drive motor  11  is operated intermittently if the amount of rain detected by the rain sensor  15  is low. In that case, a pause follows each wiping cycle that consists of a pivoting back and forth movement of the windshield wiper  13 , until the next wiping cycle occurs. With increasing rain amounts, the respective pause time is shortened. As soon as the pause time falls below a specified value and a correspondingly increased rain amount is detected, the drive motor  11  is controlled by the characteristic curve  19  to run continuously at low speed. If the detected amount of rain increases further, the speed of drive motor  11  is adjusted toward higher values, until it reaches its maximum value M for high rain amounts. With decreasing rain amounts, the drive motor  11  is controlled in the opposite direction. 
     Independent of the automatic control operation that depends on the rain amount, a fixed speed can be switched on for the drive motor  11  by using the wiper switch  18  to switch to stage  2 . An even higher speed can be adjusted by further switching to the stage  3 . In accordance with the relevant specifications, the number of wiping operations in switching stage  2  is 40 per minute, for example, and the number of wiping operations in switching stage  3  is 55 per minute. For this, the maximum speed of drive motor  11  is higher for the operation in switching stage  1 , which depends on the amount of rain, than the speed in switching stage  3 . 
     In order to change the wiping characteristic predetermined by the characteristic curve  19  to match the driver requirements, the control circuit  16  is provided with an algorithm adaptation control, which permanently changes the characteristic curve data if respective control commands are input. 
     The wiper switch  18  is used for this, and an evaluation is made as to when the driver changes the operating data, predetermined during the automatic wiping operating in switching stage  1 , by switching to the stage  2  or  3 . The control commands derived thereof are evaluated in the algorithm-adaptation control. 
     If the subjective wiper  13  operation is too slow or too infrequent, according to FIG. 4 a , then the driver switches the wiper switch  18  to continuous operation in switching stage  2  or  3 . FIG. 4 b  illustrates this switching operation for switching stage  2 , starting with the characteristic curve  19  for an operating point A 1 . The control signal derived from the switching operation causes the operating point A 1  to be raised to a new operating point A 11  in the algorithm-adaptation control according to FIG. 4 c . New operating data are simultaneously computed for the complete new characteristic curve  19 . 1  with reduced slop, but the same end point M for the highest amount of rain. The characteristic curve  19  is thus pivoted around the center M in clockwise direction. In the process, the value for the change from operating point A 1  to the operating point A 11  is less than the absolute value of the control command between the operating point A 1  and the number of cycles per time unit according to switching stage  2 . In that case and with a direct switching upward from the switching position  1  to the switching position  3 , the operating point can be increased by an amount that is higher than for the switching from stage  1  to stage  2 . If subsequently the wiper switch is again switched back to stage  1  for the automatic operation, the drive motor is controlled according to the new characteristic curve  19 . 1  with shortened pauses for the intermittent operation or an increased number of continuous wiping cycles for higher rain amounts. 
     This characteristic curve is maintained until no switching to the switching stages  2  or  3  is considered necessary. It is desirable if the operating data are not changed too drastically during a switching operation, preferably by less than 50%. If a switching upward to the switching stages  2  or  3  causes only a slight change, preferably less than 5%, then a further re-calculation of the characteristic curve does not make sense. It can also be advantageous in this case to take over a new characteristic curve as changed characteristic curve for the control, but only if the manual control means are switched back to the characteristic-curve controlled first stage within a predetermined time period. However, it can also be useful if several independent characteristic curves are deposited in the control circuit, such that they can be called up. In that case, it can be advantageous if the individual characteristic curves are deposited so that they can be called up via the manually activated control means, which here is a selector switch. 
     The change of the characteristic curve from operating point A 1  to operating point A 11  is again shown in FIG.  5 . In addition, it is shown therein that an increase in the slant of the current characteristic curve  19 . 1 , for example to the slant according to the original characteristic curve  19  is possible with the aid of wiper switch  18  if the operating point A 2  specifies operating data, which are above the operating data of the values predetermined for position  2 . If the wiper switch  18  accordingly is switched from the automatic switching stage  1  to the switching stage  2  with fixed speed, the control signal derived thereof is negative and provides a new operating point A 22 , which in the present case by accident happens to be on the original characteristic curve  19 . The algorithm-adaptation control in the control circuit  16  thus generates the current characteristic curve  19  for this operating point A 22 , which specifies the operating data for drive motor  11  that control a reduced number of cycles per time unit or an increase in the intervals for the intermittent operation. The same slope-increase function can also be achieved in that the wiper switch is switched by the rain-dependent automatic stage  1  to the zero position while the ignition turned on or the vehicle drive motor is still operational and the control command obtained in this way is transmitted to the algorithm-adaptation control. 
     The adaptive adjustment of the characteristic curve can be applied to the standard characteristic curve  30 ,  33  as well as the limit characteristic curve  31 ,  34 , so that a subjectively improved windshield wiping function can be achieved for bright conditions or darkness or with high or low temperatures. 
     Of course, it is also possible to provide control means for influencing the slope of the characteristic curve or for selecting individual, different characteristic curves, which characteristic curve can be activated independent of the wiper switch by the driver of the vehicle or a maintenance facility. The selection of a driver-specific characteristic curve is possible even if the motor-vehicle control processes such memory functions as adjusting the seats and the mirror or coding of the ignition key. By calling up one of these driver-dependent functions, the associated characteristic curve for the wiper operation can be selected. 
     When switching from the steering column switch to the OFF stage, one advantageous modification makes it possible to distinguish whether the user actually wants to switch off only the windshield wiper  13  or whether the interval pauses appear too short. That is to say, if longer interval pauses are required for the current, small amount of rain. If the switch is switched off because the interval pause times appear too short, an adaptation of the characteristic curve  19  is advantageous. However, if the wiping must actually be stopped, an adaptation is not necessary. To make a distinction between these two cases, the rain sensor  15  is read for a limited time, at most 1 minute, following the switching of the switch to the OFF position. If the rain sensor  15  no longer detects any rain, it can be assumed that the switch was actually turned off. If the amount of rain measured during the limited time exceeds a predetermined threshold value, it is assumed that the interval pause time was too short and the characteristic curve  19  is adaptively adjusted. 
     On the whole, this results in a control device for the drive motor of a windshield wiper, for which the rain-dependent characteristic curve for controlling the drive motor can be changed later on, wherein the operating data of the drive motor can be changed in dependence on environmental conditions. This increases the vehicle comfort as well as the safety in difficult traffic situations. In addition, manually actuated control means can be used for the input of corresponding control commands. The existing multi-stage wiper switch in the vehicle preferably can be used for these control means. In the process and referring to the actual characteristic curve, a determination is made at the momentary operating point specified by the determined rain amount whether the user desires a higher or lower number of wiping cycles during further switching operations. A corresponding change in the slope or course of the characteristic line is then derived from this information.