FR2736023A1 - Thermal protection of windscreen wiper drive motor on motor vehicle - Google Patents

Abstract

The protection of the windscreen wiper motor is by an electronic controller (3) in the supply circuit to the wiper motor (1). The electronic controller has an electromagnetic relay (5) switching direct current supply to the wiper motor. A second electromagnetic relay (6) connects supply to either the high- or low-speed windings of the motor. The relay coils are connected to a control unit (7). The control unit is connected to the wiper end-of-travel switches (2) and to the driver's control switch (4). The sweep time for the wipers is measured and, if it exceeds a preset time, a count is incremented. If the count reaches a preset number the wiper control is automatically dropped to a lower demand setting.

Description

PROTECTION DEVICE FOR A WIPER MOTOR
IN A MOTOR VEHICLE AND ITS CONTROL METHOD
The invention relates to a device for protecting a wiper motor, in a motor vehicle, intended to drive the wiper blades on the windshield in rainy weather, and its control method. Depending on the density of the rain, and therefore the degree of humidity of the windshield, the motor must overcome a more or less significant torque depending on the friction exerted by the brushes.

The greater the resistive torque that the engine has to overcome in order to operate, the more the engine heats up, leading to its possible destruction after a certain time.

Wiping the windshield of a motor vehicle is a very important factor in motorist safety in rainy weather. A windscreen wiper, or wiper, consists of a metal brush holder in which is fixed the bead heel which is its thick part ensuring its stability. The rubber broom is extended by a blade, or lip, which removes water at each round trip by turning. A motor drives one or both brushes and must overcome the friction due to the greater or lesser amount of water flowing on the windshield, to dust or various dirt.

Currently, the wiper motor, which is connected by wiring to a control lever allowing to choose the wiping speed according to the humidity of the windshield, is only protected by a fuse which does not blow , because the motor does not have a short circuit, and therefore does not prevent it from blowing.

Another current protection means is a thermal circuit breaker calibrated exactly for the motor with which it is associated. Its main drawback is its high price.

The invention solves this problem by proposing an electronic management of the power supply to the wiper motor which includes an opening contact with the fixed stop of the wipers, based solely on the information from the first contact tilting front.

From this information, the electronics are able to calculate the scan time or the speed with which each scan is performed. The invention uses for this electronic systems such as a microprocessor, electromagnetic relays and memories.

More specifically, a first object of the invention is a device for protecting a wiper motor connected to a DC voltage supply circuit, controlled by a lever according to three scanning modes corresponding to two operating speeds. different, a first so-called small speed being lower than the second so-called high, and provided with a fixed stop contact intended to indicate the instants when the wipers are in the rest position, characterized in that the supply circuit of the motor is an electronic system comprising - a first electromagnetic relay authorizing
supply by a DC voltage, - a second electromagnetic relay, connected between the
first relay and the motor, and authorizing the
engine operation in small or large
speed, - a control unit connected to the fixed stop contact
windscreen wipers and the control lever, - counting means, - comparison means, - storage boxes for the time values
scan, scan time thresholds,
timers, and thresholds for exceeding the
scanning time.

A second object of the invention is a method for controlling a device for protecting a windscreen wiper motor, characterized in that it consists in controlling the operation of the motor, for these two scanning speeds, by: - a measurement of the sweep time defined between two
fixed wiper stopping positions, - a wiper blocking detection phase, - a comparison of the sweep time value
with a scanning threshold, determined as a function of
the engine speed, - a count of the number of exceedances of said threshold
sweep by the sweep time, resulting in 1) in the case of the low operating speed - an engine stop if this number of exceedances is
above a threshold, and - restarting the engine after a
time delay; 2) in the case of high operating speed - switching to low speed of the motor and control
of its functioning, with in addition a comparison
scanning time with a scanning threshold of
value between the scanning thresholds
respective corresponding to the large and the small
speed, below which the motor returns to
great speed.

Other characteristics and advantages of the invention will appear on reading the following description, given in relation to the accompanying drawings in which: - Figure 1 is an example of an embodiment of a
protection device according to the invention; - Figure 2 is the flow diagram of the process steps
for controlling the device according to the invention.

According to the invention, the protection of the wiper motor in a motor vehicle is obtained by electronic management of the DC voltage supply to the motor. As shown in FIG. 1, the motor 1 is fitted with a fixed stop contact 2 for the windscreen wipers and is connected to an electronic system 3 for managing the power supply of the motor by a direct voltage V, of the order of 12 volts supplied by a battery for example. A control lever 4 allows the motorist to choose, from a rest position A, the wiping mode of the wipers according to the degree of humidity of the windshield, generally according to three possibilities. speed, called low speed PV, ensures scanning in normal rain, a second speed higher than the first, called high speed GV, is used in heavy rain, and finally a CV timing mode allows to wipe the screen cyclically breeze in the event of low humidity, the speed of the actual sweep being equal to the low speed but two successive sweeps being separated by a time delay.

Previously, this control lever provided the direct link between the battery and the motor thus supplied. According to the invention, this controller is connected to the electronic system which will manage the power supply to the engine according to the request of the motorist. The fixed stop contact 2 opens each time the motor has brought the wipers back to the rest position, at the bottom of the windshield after a full round-trip sweep. The electronic system 3 receives from this contact the information of the first tilting front of the contact part with opening of the fixed stop and calculates, from this single information, the speed with which each sweep is carried out, or the time of each sweep defined between two fixed stop positions of the wipers. By controlling this sweeping time continuously, we know the operation of the wipers which either sweep freely and in good conditions or must overcome a torque strong resistance, especially when the windshield dries.

To control the motor as a function of the command imposed by the lever 4 on the one hand and the actual wiping time of the wipers on the other hand, the electronic system 3 comprises two relays 5 and 6 connected in series between the source of DC voltage V and the motor 1. The first relay 5 has the function of ensuring the supply of voltage to the motor and the second relay 6 directs this supply voltage either to the low speed motor path, or to the large path speed. The electronic system also includes a central control unit or microprocessor 7, receiving the various information from the lever 4 and from the contact 2 of fixed stop of the wipers, and driving the relays 5 and 6 according to a control strategy which will be developed in the rest of this description. The system also includes several memory boxes 8 necessary for memorizing the information which the microprocessor needs, as well as counting means 9, or counters, and comparison means 10.

The method for protecting a wiper motor according to the invention is based on the following principle.

The wiper being controlled at low speed, the microprocessor controls the operation of the motor by measuring the sweep time. If this time is abnormally long, you must first detect if the wipers are blocked, that is to say if they cannot sweep the windshield. In this case, the engine must be stopped temporarily for it to cool. If the wipers are not blocked but have too much friction on the windshield and the engine has to overcome, the electronic system stops the engine temporarily to allow it to cool. After this time, the engine is restarted and electronically controlled.

In the case where the motor is controlled at high speed, and the sweeping time is abnormal, the microprocessor first checks whether there is blockage of the wiper sweep, then controls its operation at low speed which it check as before, with engine shutdown if necessary. On the other hand, if the operating conditions return to normal, the motor is again piloted at high speed and the control of its correct operation ensured. It will be noted that the passage of the motor from high to low speed is often sufficient to increase the wiping speed, because a characteristic of wiper motors is to have a significantly higher torque in small than in large speed, to the point that for an identical resistive torque, the low speed can generate a sweep faster than the large.

In more detail, as shown in the flow diagram of FIG. 2 in relation to FIG. 1, the protection method comprises the following steps, fulfilled by the central unit 7 of the electronic management system 3, in the case where the control lever 4 is in the "low speed" PV position.

First of all, the continuous measurement and the storage of the sweep time T1 defined between two fixed stop positions of the windscreen wipers, given by the first tilting front of the fixed stop contact 2, is carried out, this step a performed by counting means 9 of the electronic system 3.

Then, a comparison is made of each value of the measured time T1 with a threshold T6 (step b), in order to detect any blockage of the wipers. This blocking threshold T6 is memorized in a memory box 8 of the electronic system 3 and determined both by the characteristics of the wiper motor and those of the vehicle, that is to say by the average sweep time. in the worst possible operating conditions. If the time measured from a first tilting edge of contact 2, is actually greater than this threshold, it is due to faulty operation of the wipers which remain blocked, and the central unit 7 then decides to stop the engine (step c) by switching off the first electromagnetic relay 5, and only restart it after a delay T7 sufficient for it to cool down (step d). Otherwise, each value of the scanning time T1 with a first scanning threshold T2, determined as a function of the speed of the motor and placed in a memory box 8 of the system 3. This step e is completed by comparison means 10.

If the measured time T1 is less than the threshold T2, the electronic system continues to supply the motor normally according to the low speed mode. But if the measured time T1 is greater than the threshold T2, the microprocessor 7 increments one of the counting means 9, or counter, accounting for the number C of overruns of said threshold T2 by the scanning time (step f). As soon as the engine has to overcome significant friction, the scanning is slower for a certain time, which increments the counter several times. For this reason, step g is then carried out of comparing the number C of overshoots with a first threshold C1 stored in memory, which causes the engine to stop (step h) by switching off the first relay 5 if this number of overshoots C is greater than the threshold C1 of overshoots, in order to allow it to cool. At the same time, the counting means 9 is reset to zero. After a step i of timer T4, also stored in the electronic system, the system makes a new attempt to restart the engine, at low speed and the control of the operation of the engine continues by resuming the steps previously described.

When the scanning time T1 becomes again below the threshold T2, the counter is reset to zero or decremented, depending on the strategy used.

In the case where the control lever is in the "high speed" GV position, the control of its operation comprises the following steps, fulfilled by the electronic system 3 and the progress of which is represented by broken lines in FIG. 2.

First, the continuous measurement of the scanning time T1 defined between two fixed stop positions of the wipers is made by counting means 9, with storage of the values of this scanning time T1 (step a '), followed by the comparison of each value of the time during measurement T1 with the threshold T6 for detecting the blocking of the wipers previously mentioned (step b ′). In the event of a blockage, the engine is stopped (step c) with triggering of a time delay T7 (step d) before restarting the engine. Otherwise, a comparison of the scanning time T1 with a second scanning threshold T3, determined as a function of the speed of the motor, is made by comparison means 10 (step e ′). If the measured time T1 is less than the threshold T3, the electronic system continues to supply the motor normally according to the high speed mode. But if the measured time T1 is greater than the threshold T3, the microprocessor increments a counter counting the number C 'of overshoots of said threshold T3 by the scanning time, due to abnormal forces that the engine must provide (step f' ). To decide on the abnormal behavior of the engine, a comparison is made of the number C 'of exceedances with a second memorized threshold C2 (step g), and if this number C' of exceedances is greater than the threshold C2, the method provides for the passage of the engine at low speed, by switching off the second relay 6.

The engine operation is then checked at low speed, starting with the measurement and storage of the sweep time T1 (step a) and the detection of the wiper blockage (steps b to d).

In the case where they are not blocked, the measurement time T1 is compared with a third threshold
T5 scanning whose value is between the first respective thresholds T3 and T2 corresponding to the high and the low engine speeds (step h ').

Detecting this phenomenon, the number C "of exceedances of said third threshold T5 is counted by the scanning time (step i '), and the comparison of the number C" of exceedances with a threshold C3 (step j') in order to observe a real reduction in the resistive torque of the motor. In this case, the number of exceedances being greater than the threshold C3, the electronic system 3 reactivates the relay 6 to restart the motor at high speed, while continuing to control the sweep time with sweep time T3 and threshold instructions C2 overshoots corresponding to this high speed.

If the sweep time is greater than the threshold T5, the engine is maintained at low speed but the operation of the engine at low speed is controlled according to steps e to i previously described, with temporary stopping of the engine, by cutting off the first relay 5, if the measured scanning time T1 is always greater than the first low speed threshold T2.

In the case where the motor is controlled according to the third so-called clocking scanning mode, corresponding to the low scanning speed with time delay between two successive scans, the control of the operation of the motor at clocking speed always comprises the continuous measurement of the time of sweep T1 defined between two fixed stop positions of the wipers (step a "), then the comparison of each value of the measured time T1 with the blocking threshold T6, previously defined for detecting the blocking of the wipers in small and high speeds (step b "). If the time during measurement T1 is greater than the threshold T6, the stopping of the motor is controlled (step c ") by cutting off the first relay 5, its resumption of operation only taking place after a delay step d" T7, of value greater than the normal running time to cool the engine.

The invention therefore makes it possible to protect the motor of the windscreen wipers of a motor vehicle against overheating caused by a defective sweeping of the windscreen wipers and which can lead to its destruction. The completely electronic management of the motor supply, from the wiper speed, resolves the problems due to the abnormal friction of the wiper blades on the windshield then detected and taken into account.

Claims (11)

1. Device for protecting a wiper motor connected to a DC voltage supply circuit, controlled by a lever according to three scanning modes corresponding to two different operating speeds, a first speed known as low speed, lower at a second so-called high speed, and provided with a fixed stop contact intended to indicate the instants when the wipers are in the rest position, characterized in that the motor supply circuit (1) is a system electronic (3) comprising - a first electromagnetic relay (5) authorizing  supply by a DC voltage (V), - a second electromagnetic relay (6), connected  between the first relay (5) and the motor (1), and  allowing the engine to operate in small or  at high speed, - a control unit (7) connected to the stop contact  fixed (2) of the windscreen wipers and the  control (4), and driving the two relays  electromagnetic (5,6), - counting means (9), - comparison means (10) - boxes (8) for memorizing the time values of  scan (T1), time thresholds (T2, T3, T5, T6)  , timers (T4, T7), and  thresholds (C1, C2, C3) for exceeding the  scanning. 2. Method for controlling a device for protecting a wiper motor according to claim 1, characterized in that it consists in controlling the operation of the motor, for these two scanning speeds, by: - a measurement of the scanning time (T1) defined between  two fixed wiper stop positions, - a wiper blockage detection phase, - a comparison of the sweep time value  (T1) with a scanning threshold (T2, T3) determined in  as a function of the engine speed, - a count of the number (C, C ') of overshoots of said  scanning threshold (T2, T3) by the scanning time,  resulting in 1) in the case of low operating speed - the engine stops if this number (C) of overshoots  is greater than a threshold (C1), and - restarting the engine after a  time delay (T4); 2) in the case of high operating speed - switching to low speed of the motor and control  of its functioning, with in addition a comparison  scanning time (T1) with a scanning threshold  (T5) of value between the respective thresholds  (T3 and T2) corresponding to the large and the small  speed, below which the motor returns to  great speed. 3. Method according to claim 2, characterized in that the detection phase of the wipers blocking consists in: - comparing each value of the measured time (T1) with a  wiper blocking detection threshold (T6),  determined by the characteristics of the vehicle and  windscreen wiper motor, - stop the motor if the said threshold is exceeded  blocking (T6), - restart the engine after a  time delay (T7). 4. Method according to claim 2, characterized in that the control of the operation of the motor at low speed, comprises the following steps - continuous measurement and storage (a) of the values  sweep time (T1) defined between two positions  fixed stop of the wipers, - detection of the wipers blocking, - the comparison (e) of each time value  scan (T1) with a first scan threshold (T2)  determined as a function of the engine speed, - the count (f) of the number (C) of overshoots of said  threshold (T2) by the scanning time (T1), - the comparison (g) of the number (C) of exceedances with  a first threshold (C1) of overshoots, stopping (h) of the engine if this number (C) of  exceedances is greater than said threshold (C1), and - restarting of the engine (i) after a  time delay (T4); - repeating steps (a) to (i). 5. Method according to claims 2 to 4, characterized in that the control of the operation of the motor at high speed comprises the following steps: - continuous measurement and storage (a ') of  values of the scanning time (T1) defined between two  fixed wiper stopping positions, - detection of wiper blockage, - comparison (e ') of each time value  scan (T1) with a second scan threshold (T3)  determined as a function of the engine speed, - the count (f ') of the number (C') of overshoots of said  second threshold (T3) by the scanning time (T1), - the comparison (g ') of the number (C') of exceedances  with a second threshold (C2) of overshoots, - switching the engine to low speed if this number  (C ') of exceedances is greater than the second threshold  (C2), and the control according to steps (a) to (d), - the comparison (h ') of the scanning time (T1) with a  third scanning threshold (T5) whose value is  generally between the scanning thresholds  respective (T3 and T2) corresponding to the large and to  low engine speed, - counting (i ') of the number (C ") of overshoots of said  third threshold (T5) by the scanning time, - the comparison (j ') of the number (C ") of exceedances  with a third threshold (C3) of overshoots, - switching to high speed of the engine if the number  (C ") exceedances is greater than the third threshold  (C3), and control according to steps (a ') to (f').  sweep (T1) is greater than the third threshold (T5). - keeping the engine at low speed if the weather 6. Method according to claim 2, the motor being controlled according to the third so-called clocking scanning mode corresponding to the low operating speed, characterized in that the control of the operation of the motor at clocking speed comprises the following steps - the measurement continues (a ") of the scanning time (T1)  defined between two fixed stop positions of the wipers  windows, - the comparison (b ") of each value of the measured time  (T1) with the threshold (T6) for blocking detection  windscreen wipers, determined by the characteristics of the  vehicle and the wiper motor, - the engine (c ") stops if the wiping time (T1)  is greater than the time threshold (T6), and - restarting the engine (d ") after a  time delay (T7), of value greater than the duration  normal timing to ensure the  engine cooling; - resumption of steps (a ") to (d"). 7. Method according to claims 4, 5 and 6, characterized in that the stopping of the engine of steps (h and c ") is carried out by cutting off the first electromagnetic relay (5) of the electronic management system (3). 8. Method according to claim 5, characterized in that the passage of the engine at low speed, in the step is carried out by cutting the second electromagnetic relay (6) of the electronic management system (3). 9. Method according to claims 4 and 5, characterized in that the counting of the overshoots by the scanning time (T1) of steps (f), (f '), and <i') is carried out by the counting means ( 9) of the electronic management system (3). 10. Method according to claims 4, 5 and 6, characterized in that the measurement and storage of the scanning time (T1) of steps (a), <a ') and (a ") are carried out by the counting means (9) of the electronic management system (3). 11. Method according to claims 4, 5 and 6, characterized in that the comparison of each value of the scanning time (T1) of steps (e), (e '), (h') and (b ") is carried out by the comparison means (10) of the electronic management system (3).