metal wiper mount

Function: The function of the wiper is to scrape off the rain, snow or dust on the windshield to ensure that the driver has a good view. The electric wiper consists of three parts: a wiper motor, a transmission mechanism and a wiper. In addition, Including wiper switch, intermittent relay and other accessories.

The structure and principle of wiper motor:

The wiper motors currently used in automobiles are basically hydromagnetic DC motors. Its stator magnetic field is a set of permanent magnetic fields made of strontium calcium ferrite or other permanent magnetic materials. It has the advantages of simple structure, high power, low power consumption, and relatively hard mechanical properties.

The wiper motor has a closed structure, and its rotating parts are generally supported by copper-based oil bearings and ball bearings. Sufficient oil or grease has been stored before leaving the factory. The gears and worms in the reducer are made of two anti-seize materials. There is enough grease stored in the reducer, so there is no need to add oil within a certain operating period (about 500 hours).

The different working speeds of the wiper are achieved by controlling the high and low speed of the motor. The high and low speeds of the wiper motor are usually obtained by using different brush combinations of the three-brush permanent magnet motor. When the brushes are 180° apart, the motor rotor windings form two symmetrical parallel branches, and the motor runs stably at a lower speed. When the brushes are biased, the number of effective winding turns in series on the motor rotor winding branch decreases, so the back electromotive force between the positive and negative brushes decreases. As the back electromotive force decreases, the armature current increases, causing the motor's torque to increase. When the load remains unchanged, the motor obtains a higher speed.

In the control circuit of the two-speed wiper motor, when the power switch is turned on and the wiper speed switch is connected to the I position, brush L and brush (+) are energized. The eight armature windings between the two brushes form two parallel branches. The back electromotive force of each winding in each branch is added, and the back electromotive force of the two branches is equal. When the sum of the back electromotive force and the internal voltage drop of the motor is equal to the power supply voltage, the motor enters a stable operating state. At this time, the rotation speed is low, that is, the wiper blade moves at a low speed, about 33 to 55 times/min.

When the wiper change switch is connected to the II position, the brush (+) and brush H are energized. The eight windings between the two brushes form two asymmetric parallel branches. One way has five windings connected in series; the other way has three windings connected in series. There is a winding in the first branch whose back electromotive force direction is opposite to that of the other four windings, canceling each other out. So in fact, each branch only has three windings connected in series, and the back electromotive force is reduced. Since the power supply voltage is basically constant, only by increasing the back electromotive force can a new equilibrium state be entered. The back electromotive force is proportional to the speed, so the motor speed will definitely rise, that is, the wiper blade moves at a high speed, about 51 to 72 times/min (the difference between high and low speeds of the same wiper motor is greater than 10 times/min).

At this time, the motor will still be running, and the circuit is as follows: battery terminal → fuse → brush (+) → armature winding → brush L → wiper switch neutral → inner contact → long slide → ground → battery negative pole. At this time the wiper runs at low speed. When the wiper blade moves to the parking position (usually the lower edge of the windshield glass), the outer contact piece contacts the raised part of the short sliding blade, the inner contact piece also contacts the short sliding blade, and the motor stops running without a ground loop. Moreover, the brush (+) and L are connected through the automatic parking mechanism, which generates electromagnetic braking to stop the wiper blade accurately. The so-called electromagnetic braking of the motor means: after the ground circuit of the motor is disconnected, the action of inertia causes the motor rotor to continue to rotate. At this time, the rotor winding generates an induced electromotive force. Due to the communication with the external circuit of the motor, an induced current is formed, and the kinetic energy is converted into electrical energy, and the motor stops quickly. operation. On the other hand, the induced current flows through the rotor winding in the reverse direction, generating braking torque and accelerating the stop of the motor.

The short sliding plate and long sliding plate of the automatic parking mechanism are fixed on the side plane of the reducer worm gear and rotate with the worm gear. The inner contact piece and the outer contact piece are fixed on the inside of the reducer cover. The outer contact piece is far away from the center of the worm gear and can only intermittently contact the protruding part of the short slide plate during operation. The inner contact piece is located at the radius of the long and short sliding plates, and will contact the long and short sliding plates successively during operation. When the wiper switch is turned off, if the wiper blade has not yet reached the parking position, the inner contact piece of the automatic parking mechanism will inevitably come into contact with the long sliding blade, and the outer contact piece will be in an open circuit state.

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