JPH05227714A - Ac generator for vehicle - Google Patents

Abstract

PURPOSE:To suppress a temperature rise of a diode by bringing cooling fins of the diode into close contact with a rear cover and increasing a thickness of a part of the cover in contact with the fins larger than that of the cover of a part of a regulator. CONSTITUTION:In the case of cooling a diode, an output current induced in a stator coil 3 flows to diode elements (DE) 26, 27 to be full-wave rectified. In this case, they are heated by forward voltages of the currents flowing in the DEs 26, 27. A quantity of heat generated at the (-) side DE 27 is diffused to cooling fins (CF) 23 and dissipated to a rear cover (RC) 15. A quantity of heat generated at the (+) side DE 26 is diffused to a (+) side CF 22, thermally conducted to an insulating sheet 21, a (-) side CF 21, and dissipated to the RC 15. Then, when a thickness of the RC 15 opposed with a regulator (RG) 14 is formed in the degree of prior art and a thickness of the RC 15 in contact with one side surface of the (-) side CF 23 is formed about 4mm, quantities of heat generated at the DEs 26, 27 can be sufficiently absorbed by the RC 15, thereby expediting averaging of the heat.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC generator mounted for supplying electric power to an automobile or the like, and more particularly to a structure of a vehicle AC generator excellent in cooling a diode constituting a diode bridge.

[0002]

2. Description of the Related Art As a conventional technique, as shown in Japanese Utility Model Application Laid-Open No. 64-9478, the thickness of the rear cover is the same for the diode bridge portion and the regulator portion.

[0003]

However, the above-mentioned prior art was satisfactory as the cooling capacity within the electric output range up to now, but if a higher output than the present is demanded, the cooling capacity is now limited. It is difficult to handle because of this.
On the other hand, due to an increase in auxiliary machinery due to diversification of end users, and an increase in new power demand such as exhaust gas cleaning equipment due to global warming, power demand for vehicles will increase year by year.
The demand for smaller and lighter vehicle AC generators is becoming stronger from automobile manufacturers. As a means for dealing with the contradictory problems, improvement in output can be dealt with by improving the magnetic circuit and increasing the rotation speed, but it is limited by insufficient cooling capacity corresponding to the improvement in output. The vital vital points of the alternator for vehicles are the stator coil, the diode, and the regulator. When the output is improved, the temperature of the diode exceeds the guaranteed temperature. An object of the present invention is to provide a diode cooling structure that efficiently suppresses a temperature rise of a diode of a vehicle AC generator and a structure of a rear cover that is effective in reducing the weight of the generator.

[0004]

The above object is achieved by bringing the cooling fins of the diode into close contact with the rear cover and making the thickness of the portion of the rear cover in contact with the cooling fins thicker than the thickness of the rear cover of the regulator portion. It

[0005]

As a diode cooling method, rather than air-cooling each of the (+) side and (-) side fins of the diode, heat generated by the diode is conducted to the cover and the entire cover is used as a heat sink. Has better cooling capacity. The present invention has a structure of a heat conduction type in which the entire surface of the (-) side diode fin, which is electrically grounded, is brought into contact with the rear cover, but the heat capacity of the rear cover is insufficient, that is, if the rear cover is thin, local heat is generated. Since spots are generated, the thickness of the rear cover of the portion where the cooling fins of the diode abut is increased so that the temperature of the diode is averaged.

[0006]

Embodiments of the present invention will be described with reference to FIGS. In FIG. 1, a pair of brackets 1 and 2 forming the outer shell of the generator are fixed by a plurality of bolts (not shown) via a stator core 4 around which a three-phase stator coil 3 is wound. Cylindrical bearing boxes projecting inward of the generator are formed near the center of the side surfaces of both brackets 1 and 2, and bearings 6 and 7 are attached to each bearing box. 8 is rotatably supported.

A pair of rotor cores 9 each having an even number of claw-shaped magnetic poles with a minute gap maintained on the inner peripheral side of the stator core.
However, by sandwiching the field coil 10 inside the shaft 8
It is fixed to. A pulley 5 is fixed to the tip of the shaft. Fans 11a and 11b are fixed to the side surfaces of the pair of rotor cores 9, respectively.
The shaft ends of a and 11b are opposed to the inner side surfaces of the brackets 1 and 2 via an appropriate gap.

A slip ring 12 is fixed coaxially with the shaft 8 at a portion projecting from the bracket 2, and a brush 13a slides on the ring. Brush 1
3 a is housed in the brush holder 13 and indirectly fixed to the bracket 2.

Along with the brush holder 13, a regulator 14 for controlling the output voltage to a constant level and a diode bridge 20 for full-wave rectifying the output current of the stator coil 3 are arranged on the bracket 2 on substantially the same plane and cover them. The rear cover 15 is attached like this.

The diode bridge 20 includes a (+) side diode fin 22, a (-) side cooling fin 23, and a thin insulation for insulating both fins, in which a plurality of diode elements for full-wave rectifying the output of the stator coil 3 are embedded. Sheet 2
1 and a diode terminal block 25.

The operation of the generator having the above structure will be described below. When a field current flows through the field coil 10 through the brush 13a and the slip ring 12 and a driving force is transmitted to the pulley 5 by an engine (not shown) or the like, a rotating magnetic field is generated in the rotor core 9. When the rotating magnetic field crosses the stator coil 3, the stator coil 3 is electromagnetically induced and an AC voltage is generated. The AC output generated in the stator coil 3 flows into the diode bridge 20 via the stator coil output line 31 and is full-wave rectified and converted into a DC output. At this time, since the output voltage of the generator changes depending on the rotation speed, the field current is appropriately turned on and off by the regulator 14, and the generated voltage is controlled to be constant.

Regarding the cooling system, the fans 11a, 1 fixed to the side surface of the rotor core 9 as the shaft 8 rotates.
When 1b rotates, cooling air flows into the generator and is discharged. By the rotation of the fan 11a, cooling air is introduced from the intake port 1a of the front bracket 1, cools the outer wall of the front bearing 6, cools the side surface of the rotor core 9, and then cools the stator coil 3 on the front side. Is discharged from the exhaust port 1b. or,
By the rotation of the rear fan 11b, cooling air is introduced from the intake port of the rear cover 15, cools the rear cover 15, the diode 20 and the regulator, and then cools the outer wall of the rear bearing 7 while passing through the intake port 2a of the rear bracket 2. After cooling the stator coil 3 on the rear side, the stator coil 3 is discharged from the exhaust port 2b of the rear bracket 2.

The cooling of the diode 20 will be described in more detail with reference to FIG. 2. The output power induced in the stator coil 3 is connected to the connection terminal 24 embedded in the diode terminal block 25 via the output line 31 of the stator coil. And the diode elements 26, 2 connected to the connection terminal 24
Output power flows into 7 for full-wave rectification. At this time, heat is generated by the forward voltage of the current flowing through the diode elements 26 and 27. The amount of heat generated in the (−) side diode element 27 is diffused into the cooling fin 23 and radiated to the rear cover 15 with which one surface of the cooling fin 23 is in contact. The amount of heat generated in the (+) side diode element 26 is equal to that of the (+) side cooling fin 22.
Thin insulating sheet 2
The heat is conducted to the 1-(-) side cooling fins 21 and radiated to the rear cover 15. The heat radiated to the rear cover 15 is
Heat is transferred and cooled by the cooling air generated by the rotation of the fan 11b.

Normally, since the rear cover 15 is a structure, it may have a wall thickness of about 0.5 to 2 mm, but the heat capacity of the rear cover 15 has recently become insufficient due to the demand for smaller size, lighter weight and improved output. Becomes insufficient and heat spots are generated in the diode elements 26 and 27, so that sufficient reliability and life cannot be secured.

Therefore, if the thickness of the rear cover 15 portion facing the regulator 14 is the same as the conventional one, and the thickness of the rear cover 15 portion with which one surface of the (-) side cooling fin 23 of the diode bridge 20 contacts is set to about 4 mm, the diode element 2 is obtained.
The amount of heat generated in 6, 27 can be sufficiently absorbed by the rear cover, and the averaging of heat is promoted, and the diode elements 26, 27
The effect is that no heat spot occurs.

Further, since the thickness of only the portion of the rear cover 15 in contact with the diode bridge 20 is increased and the other portions are thin, the weight is the minimum necessary for the generator, and there is an effect of weight reduction.

[0017]

According to the present invention, the cooling fins of the diode are brought into close contact with the rear cover, and the thickness of the portion of the rear cover in contact with the cooling fins is made thicker than the thickness of the rear cover of the regulator portion. The temperature rise of the diode of the generator can be efficiently suppressed, and it is also effective in reducing the weight of the generator.

[Brief description of drawings]

FIG. 1 shows a cross-sectional view of a generator that is an embodiment of the present invention.

FIG. 2 is a partial sectional view of a diode section.

[Explanation of symbols]

1 ... Front bracket, 2 ... Rear bracket, 9 ... Rotor core, 14 ... Regulator, 15 ... Rear cover, 2
0 ... Diode bridge.

Claims (1)

[Claims] 1. A rotor rotatably supported by a pair of bearings held on the inner peripheral sides of a front bracket and a rear bracket, a diode bridge and a regulator incorporated outside the rear bracket, and the diode bridge and the regulator. In a vehicular alternator constituted by a rear cover that covers from the outside, one surface of the diode bridge is brought into full contact with the rear cover, and the thickness of the diode bridge portion of the rear cover is in contact with the regulator portion of the rear cover portion. An alternator for vehicles characterized by being thicker than the thickness.