DE3516136A1 - Wash/wipe interval control device for motor vehicle windows with an integrated circuit - Google Patents

Abstract

Wash/wipe interval control device with an integrated circuit (IC) and only one RC element for obtaining the two time functions with the three times of switch-on time (to), interval pause (tp) and after-wipe delay time (tv), where the IC does not contain any fragile and complex frequency dividers. The inputs of the IC are configured in such a way that they can be driven with all the combinations, which occur in various vehicle types, of the switch-on potentials of the interval switch (I) and of the washer pump (W). The minimum external circuit limits the electrical interference pulses coming from the electrical system of the motor vehicle to small values which can be absorbed by linear integrated circuits.

Description

Wipe-wash interval control device for motor vehicle windows

with integrated circuit In motor vehicles are electronic Control devices for controlling windshield wipers are widely used.

This device category can be divided into so-called interval control devices, which operate the windshield wipers in intermittent operation when there is little rainfall, so-called wipe-wash control units that operate the windshield wipers when the washer pump is operated for a period of a few seconds after the washer pump has stopped operating let it continue running and the combination of both functions, so-called wipe-wash interval control devices (WWIS devices).

The described types of devices are still different today because of their differences Design of the various vehicle circuits (wiper motor, switch) with discrete Semiconductors built up. They become the corresponding external vehicle circuit adapted, are relatively complex in terms of components and usually have to the required time tolerances are adjusted.

A typical example of a wipe-wash interval switch used today is the picture 1.

The invention is based on the idea of a device with an integrated To create a circuit for this application that allows WWIS devices with to create small dimensions and tighter tolerances while at the same time reducing them Costs for this device category. The integrated circuit should be in different Device types can be used for different vehicle circuits.

The technical requirements for the usability of an IC in These devices are - low environmental switching with high immunity to interference electrical interference from the vehicle electrical system, - universal applicability in various Vehicle circuits, - easy to implement as an integrated semiconductor scarf tion.

The inventive circuit arrangement for a wiping-washing In ter Valles expensive ge advises with an integrated circuit meets these requirements in a simple way In that - only one RC element for both time functions (interval and wiping) is required without interposing complex and failure-prone frequency dividers.

- The accuracy of the integrated circuit allows that so far to omit the usual from the same of the time functions.

- the inputs for the input signals interval (from the switch) and Subsequent wiping (from the washer pump) designed as a so-called tri-state version that are driven with both positive and negative potential can.

- The external circuit parts are arranged so advantageously that together with the internal measures to limit interference against electronic interference from the vehicle electrical system (e.g.

Zener diodes) the interference current and thus the pulse power loss on the IC limit to relatively small values.

Functions 1. The interval and wipe-wash delay functions with only one timing element can be achieved, for example, as described below (function diagram Figure 2 and principle of the external circuitry of the IC Figure 4a.).

1.1 Interval When the capacitor is discharged, the relay is at the output A not excited. When switch I is switched on, the output, the relay, is energized attracts. The capacitor is charged with a relatively large current in time to (Pulse time). When the threshold Uab is reached, output A is de-energized and the Discharge capacitor with a lower current. This current is externally via set the resistance Rt. The pause time tp can be widened by the resistance Limits can be varied.

When the lower threshold Uan is reached, the capacitor is again Charged relatively quickly, etc. (feedback threshold switch as a multivibrator).

1.2 Wipe-wash operation When activating input W, which is for each can take place at any time during interval operation or in the idle state, a memory contained in the IC is set, which is independent of The state of charge of the capacitor controls output A. At the same time the capacitor suddenly discharged. The capacitor remains discharged as long as the control through input W (tw) is present. As soon as the input W is no longer activated, can be the capacitor by a relatively small current that either with the same external resistance as at I or set by a second resistor Rt ' can be back on. When the threshold Uab is reached after the delay time tv the output is switched off, the memory is reset and the capacitor suddenly discharged.

Program the specified external resistor (s) in the IC included power sources for the times tp and tv.

The use of only one time-determining resistor means at According to this principle, a fixed ratio between these two times (interval time and wiping time).

With two different resistances, both times can be dependent can be varied from each other.

To make the required memory more immune to electrical interference from the on-board network, it is advisable to only use the reset pulse on the memory to take effect during the relay delay time.

The circuitry of the IC is shown in Figure 4a and 4b. The relay is controlled directly by the IC and switches the wiper motor. Determine Rt and C. as described the two time functions (3 times). The resistor Rv is used for Limitation of the interference current through the IC in the event of interference voltage peaks on the vehicle electrical system.

Depending on the design of the internal circuitry of the IC, the relay can counteract + (Fig. 4a) or - (Fig. 4b) must be switched.

According to the switch-on potential for the washer pump (M) polarize the diode so that the switch-on potential is led to the IC. The diode serves to decouple the tri-state input (see point 3) as well as also for separating the very high inductance peak, #ie when switching off the Pump occurs from the IC.

2. About any possible susceptibility of the IC to interference in the event of strong interference pulses and unfavorable arrangement of the device in the on-board network due to the memory used To avoid this, a second option was found without the internal storage tier get by (function diagram Fig. 3).

2.1 Interval The interval function is, as under 1.1. described, retained (feedback threshold switch between the thresholds UIab ' Ulan) 2.2 After wiping To use the function after wiping with only one To achieve a timer, the capacitor voltage is set via a second threshold switch additionally queried. Above the threshold Uw, which is higher than Ilab, switches this threshold switch sets the output current IA.

As soon as the input W is activated by a signal, it charges the capacitor immediately to the fixed or externally adjustable voltage Uo. He remains charged for the actuation time tw of the pump and is after the end of this time by a relatively small discharge current, which as already described with a or two external resistors can be set to discharge.

To improve the signal-to-noise ratio and a short switch-on delay To achieve the wipe-wash function, the second threshold switch can also be used be provided with a hysteresis for the switching point.

To change the time tv compared to tp you can use the discharge current instead the voltage levels Uo and Uw can also be shifted.

3. As described above, it is advantageous to use the inputs W and I as so-called tri-state inputs. Thereby the tension on these Inputs through an internal voltage divider to a fixed value set between o and the positive supply voltage. This value is taken from Threshold switches monitored. The input is only activated when the level is shifted to zero or plus by the potential supplied from the outside.

This arrangement allows in addition to the activation of the inputs by different potentials also additional switch-on delays. Especially those of input W via another external RC element. The switch-on delay times possible in this way are significantly longer than the short delay time mentioned under 2.2, paragraph 3 became.

Claims (3)

Claims: wipe-wash interval control device for motor vehicles ug discs with an integrated circuit, characterized in 1. That only one timing element (Rt and C) for both functions of the science and control unit (interval and Wiping) is required without being in the integrated circuit used complex and failure-prone frequency dividers are interposed. 2. Apparatus according to claim 1, characterized in that the inputs for the input signals interval (I) and wiping (W) as so-called # ri-state inputs are executed, which are driven with both positive and negative potential can be. 3. Apparatus according to claim 1, characterized in that the external Circuit parts Rt, Rv, relay and C are arranged so advantageously that they are at positive or negative interference voltages from the vehicle electrical system Limit interference currents and thus the pulse power loss on the IC to relatively small values. This low power dissipation can be achieved by a conventional analog IC with chip area less than 1 mm2 in 8-pole dual-in-line housing absorbed by internal protective measures will.