DE2207198A1 - Control device for an electric see wipers for continuous and intermittent operation - Google Patents

Description

ZELLENTIN ι ·. LUYKEN

Patent attorney

• 7 Ludwigshafen / Rhine tubwutr. 30

Pabbrica Italiana magnet! fim I679

Marelli S.p.A. Feb. 15, 1972

Milano Oe / Rt

Control device for an electronic windshield wiper for continuous and intermittent operation

The present invention relates to a control device for an electronic windshield wiper for continuous and intermittent operation, the motor of which is supplied via a thyristor at the beginning of each intermittent working period, while it is supplied at the end of each working period is braked electrically via a brake circuit connected to the motor.

In the known windshield wipers of this type, the brake circuit has a resistance and is in the shunt to the engine even at the beginning of each intermittent work period, with the disadvantage that a current consumption at the beginning every working period by the battery. On the other hand, the aforementioned resistance cannot be high Purposes of such power consumption, because in this case the effectiveness of the braking would be impaired. This upstream take are disadvantageous, either because of the consumption or because of the heating when the battery voltage increases. For example, it already has a battery voltage of 24 V. the current drawn is of the order of a few tenths of an ampere when the resistance of the circuit is of the order of a few Ohms or fractions of ohms.

The object of the present invention is to provide a

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such braking circuit of the control device that its control energy is fully utilized at the beginning of a working period will. According to the invention, the solution is that the brake circuit has at least one semiconductor switch (e.g. a controlled diode SCR,) which is connected to a supply terminal (H) of the Motor (M) is connected and also controlled so that it is locked at the beginning of each work period, later on the other hand is conductive and takes over the strong braking current before the end of each working period.

Advantageously, at the end of each working period, one Circuit created for an immediate braking of the motor, which locks the wiper blade in its end position. These Circuit does not draw any current at the beginning of a working period.

The electronic brake circuit preferably has a controlled diode (SCR ₁ ), which is connected with its anode to the supply terminal of the motor both via a line with high resistance and via a limit switch in the rest position and also connected to the cathode to Nasse via a changeover switch is. The controlled diode is controlled by means of a timer, namely after a certain period of time from the beginning of each working period in the current-conducting state and at the latest when the end switch returns to the rest position. The timing circuit advantageously consists of a programmable switching transistor (unijunction transistor), to which a capacitor is assigned, which is charged at the beginning of each working period and the transistor becomes conductive when it is discharged.

The discharge occurs later than the start of the working period

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and coincides at most with the moment of the end of the working period.

Further advantageous features of the invention emerge from the following description of the drawing of an exemplary embodiment. In the drawing show:

FIG. 1 shows the circuit diagram of an electronic windshield wiper with the brake circuit according to the invention, FIG. 2 is a diagram for explaining the brake circuit according to FIG. 1.

Referring to Figure 1, there is the control part the wiper circuit from a supply battery + B, a two-way switch K with J positions, a DC motor M with the assigned limit switch S and a thyristor (SCR).

of the switch In the three switch positions K is one - position R is the Rest position, which is shown in the figure, another is the working position for intermittent operation position I - and the third position - position C - is the working position for continuous operation. With TE is denotes an electronic timer that controls the thyristor SCR.

In continuous operation, the battery + B supplies immediate power switch the motor M to its position C. After the end of operation, i.e. with K in position R, as soon as the limit switch S has assumed its rest position P, the motor M, which now acts as a generator, is short-circuited and quickly brought to a standstill. This short circuit is over

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a line branched off from the motor at H is triggered and closes via S, P, A and K in position R to the other terminal or terminal. Dimensions.

According to the invention, the brake circuit of the motor M has a controlled diode SCR in intermittent operation, the cathode of which is connected to ground via the switch K in its position I and the anode of which is connected to the terminal H of the motor via two paths, one directly via S in the position P and another one having a _{high resistance R 1 of} the order of 1000 ohms.

The ignition of the diode SCR- is controlled according to the invention by a timing circuit which consists of a programmable switching transistor (unijunction) PUT, the cathode of which is connected to the control electrode of the diode SCR, the control electrode being connected to point D of a resistance voltage regulator Rp, R-, is connected and the anode to an electrode (point P) of the capacitor C ₁ , which in turn is connected with this electrode to the terminal H for supplying the motor via a resistor R ^, and with the other electrode to ground via K in position I.

In the case of intermittent operation, the switch K is set to position I and after a specified time has elapsed, the timer TE ignites the thyristor SCR, via which the battery + B supplies the motor M. The motor starts and causes the removal of limit switch S from its rest position P. is located If the limit switch S is in the operating position Q, then while the motor is powered directly by the battery + B

SCR
the thyristor blocks.

When the motor is fed in, the charging of the

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Capacitor C ^ via the circuit: Terminal H, resistor R ₁ ,, C ₁ , K in position I, ground.

FIG. 2 shows the curve f (t) of the voltage V _M at the connections of the motor and the charging voltage Vp _{1 of} the capacitor during the two working periods. T ₁ and Tp are the two moments of the start of the supply of the motor and Tl and Tp the moments of the end of the supply.

The capacitor C ₁ is charged until its voltage has reached the value of the trigger voltage V _{0 of} the switching transistor PUT, a value determined by the resistor divider Rp, R ^. At this moment, indicated in FIG. 2 mi * t., Tp, the capacitor discharges via the anode of the switching transistor PUT and the control electrode of the diode SCR ₁ and causes the latter to ignite.

If the ignition of SCR _{1 takes place} before the end of a working period (not shown) and so if S is still in the running pitch Q, then the one-way line, which has the resistance R _{T of} high value, is traversed by a weak current, the minimum required to keep the controllable diode SCR conductive.

At the end of the working period, when the _{limit switch S returns to the P position, the resistor R 1 is} shunted and the diode SCR is in a branch going through S, P · and I. «

Under these conditions, the motor brakes immediately. From the foregoing it is clear that that

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The motor is braked via a circuit which has a controlled diode SCR ₁ , which is already conductive when the forward current is weak before the end of the working period, so that at the end of the working period it is ready to conduct a strong braking current, which is generated by the generator Motor M is generated.

The moments t-, tp in which the discharge of C- takes place and ultimately the activation of the diode SCRj * can at most coincide with the moments T, ¹ , T ₂ ¹ in which the charging voltage of C _{1 is} equal to V and that in Pig . The course shown in dashed lines below the curve V ~.

On the other hand, for good operation it is necessary that t ,, tp later than the moments of disconnection of the limit switch S from position P, which are indicated by t in FIG. and t ~ are given. In particular, it is appropriate that the arrangement be such that t 1, t p occurs later than the contact times of S with Q.

It should be noted that when the motor comes to a standstill, at the end of the working period, the braking circuit is de-energized and the diode SCR _{1 is} not conducting. This ensures that at the beginning of the new working period no current can be branched off at point H, neither via the resistor R_ nor via the limit switch S, which is still in the P position. This avoids the disadvantage that current is consumed at the beginning of each working period, as is the case with conventional brake circuits. As shown, the instantaneous braking circuit has only diode SCR ₁ . It is obvious, however, that to protect the used. Diode with a strong braking current in series with it, for example between the cathode, ground, a braking resistor (with a low wattage) is used (as indicated by R, -).

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Claims (2)

CELL Tiri ν. LOVKEH Patenlanv / aiia 67 Ludwigshafen / Rhine l. 30th Fabbrica Italiana Magneti flm I679 Marelli S.p.A. Feb 15, 1972 Milano. Oe / Rt Patent claims Control device for an electronic windshield wiper r continuous and intermittent operation, in which the engine at the beginning of each working period with intermittent operation is supplied via a thyristor, which is controlled by a timer, and is braked at the end of each working period via a brake circuit that is shunted to the motor, thereby characterized in that the brake circuit has at least one semiconductor switch (e.g. a controlled diode SCR,) connected to a supply terminal (H) of the motor (M) in such a way connected and is also controlled in such a way that it is blocked at the beginning of each working period, but later conductive and takes over the strong braking current before the end of each working period. 2. Control device according to claim 1, characterized in that the controlled diode (SCR,) is connected with its anode to the supply terminal (H) of the motor (M) both via a line with high resistance (R,) and directly via a limit switch (S ) is connected in the rest position and its cathode can also be connected to ground via a changeover switch (K) and that it (SCR,) is _{controlled by a timing circuit (PUT, Rp, R ^, R 1} ,, C.) so that it is conductive from a certain time from the beginning of each working period and to the maximum degree at the moment the limit switch (S) is reset to the rest position. 209836/0842 Control device according to Claim 2, characterized by a _{timing circuit (PUT, R 2} , R, Rj) such that the controlled diode (SCR,) becomes conductive after the limit switch (S) has reached the operating position (Q). Device according to claims 2 and j, characterized in that the timing circuit consists of a switching transistor (PUT) whose trigger voltage is determined by a resistor divider (Rp, R ^) and whose anode is connected to a capacitor (C-), one of which is an electrode is connected to the supply terminal (H) of the motor (M) via a resistor (Rh) and on the other hand to ground via the changeover switch (K) in the position for intermittent operation. 209836/0842