JP4123768B2 - Step-down transformer for vehicles using molded coil - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a step-down transformer for a vehicle using a formed coil, and more particularly to a step-down transformer for a DC-DC converter used in a vehicle power supply system of a dual power supply voltage system.
[0002]
[Prior Art and Problems to be Solved by the Invention]
In an electric vehicle including a hybrid vehicle, a dual power supply system in which power is supplied to a traveling motor from a high-voltage main battery and power is supplied to various auxiliary machines from a low-voltage auxiliary battery is advantageous in various respects. Further, even in a normal internal combustion locomotive, there is a tendency to install a two-battery power supply system in which both a high-voltage main battery and a low-voltage load power supply auxiliary battery are mounted due to various factors. In this dual power supply vehicle power supply system, it is a reasonable choice in various ways to reduce the capacity of the auxiliary battery and transmit power from the main battery to the auxiliary battery through the step-down DC-DC converter device.
[0003]
This step-down DC-DC converter device includes an inverter circuit that forms a single-phase AC voltage from an input DC voltage, a step-down transformer that transforms the single-phase AC voltage, a rectifier that rectifies the output voltage of the step-down transformer, Usually, it is composed of a smoothing circuit that smoothes the voltage, but in order to reduce the burden on the smoothing circuit, it is usual to configure the rectifier unit with a single-phase full-wave rectification method with the secondary coil of the step-down transformer as an intermediate terminal It is. Hereinafter, this step-down transformer is also referred to as a step-down transformer for a single-phase full-wave rectifier. This step-down transformer for a single-phase full-wave rectifier has a pair of secondary coils wound in the same direction and connected in series, the rectifier circuit is composed of a pair of rectifier elements, and the pair of secondary coils are connected to each other The midpoint thus formed is grounded or used as an output terminal to the smoothing circuit.
[0004]
The coil of the step-down transformer for single-phase full-wave rectifiers uses a formed coil that is formed by bending a flat conductor wire in a spiral or ring shape in a plane direction parallel to its main surface. It is preferable in terms of reducing electric resistance.
[0005]
A coil insulation member is used to electrically insulate the coil of the transformer. The coil insulation member performs inter-turn insulation that insulates each turn of the coil from other turns, inter-coil insulation that insulates the primary coil and the secondary coil, and anti-core insulation that insulates the coil and the core. Insulation between turns and insulation between coils are also called line insulation.
[0006]
As the method of coil electrical insulation, a method of coating a resin film on the coil surface, a method of winding an insulating tape around the entire coil, and the coil as a whole is also called a winding bobbin-shaped insulator (hereinafter also simply referred to as an insulator or a bobbin-shaped insulator). ) And a method of resin-molding the entire coil are widely used. In a transformer with a relatively small capacity, a method in which a coil wound around a winding bobbin (winding bobbin, also simply referred to as a bobbin) is attached to the core is used. In this case, the bobbin is a member for coil winding work. In addition to the function as the above, it also functions as the coil insulating member.
[0007]
If the resin film is thick, cracks may occur when the coil is bent, so it is thinned and used mainly for insulation between lines, and the insulation tape and bobbin-like insulator are wound or attached to the bent coil so that it can withstand core insulation. The resin mold method has both a line insulation function and a core insulation function.
[0008]
In a transformer for a vehicle, in addition to electromagnetic vibration generated in the coil and core during energization, it is necessary to prevent vehicle vibration transmitted from the traveling vehicle from energizing the coil and causing the coil to abut against the core surface and damage the resin film. Yes, it is essential to secure the core insulation function. The winding process of the insulating tape around the coil is difficult to automate, and the adhesive for bonding the insulating tapes is poor in heat resistance, so it is preferable to use it actively in a high temperature and high vibration environment such as a vehicle engine room. Absent. The method of resin-molding a bent coil is difficult to reduce costs due to the complexity of the manufacturing process and manufacturing equipment, and the entire resin-molded coil that has been molded and made highly rigid as a whole is subjected to thermal stress due to heating and cooling cycles. And when various vibrations are applied and cracks occur in the mold resin or hydrolysis occurs, creeping discharge may occur at the shortest distance.To prevent this, the resin thickness near the surface of the resin mold coil is It was necessary to secure enough, and the whole physique tended to increase.
[0009]
From these points, it is economical to interpose a cylindrical portion and a bobbin-like insulator having a rib portion extending radially from both ends of the tube portion between the inner peripheral surface and both end surfaces of the coil and the core surface. This is the most suitable.
[0010]
However, in order to mount the above-described molded coil, which can easily improve space occupancy, has low electrical resistance, and can flow a large current, on a conventional bobbin-shaped insulator, the molded coil is directly wound around the bobbin-shaped insulator. Although it is unavoidable, workability deteriorates although it is not impossible, and a large gap in the axial direction is finally formed between the formed coil and the rib plate portion of the bobbin insulator in the coil housing space of the bobbin insulator. As a result, the length of the core in the axial direction is increased, leaving a room for the coil to vibrate in the axial direction with respect to the bobbin-shaped insulator.
[0011]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a step-down transformer for a vehicle using a molded coil that is easy to manufacture and excellent in reliability.
[0012]
[Means for Solving the Problems]
A step-down transformer for a vehicle using a molded coil according to the present invention includes a core having an axial cross section formed in a letter shape, a primary coil and a secondary coil wound around a central column portion of the core, and the primary coil as described above. In a step-down transformer for a vehicle using a molded coil having a core and an insulator that is electrically insulated from the secondary coil, the pair of secondary coils are individually arranged on both sides in the axial direction of the primary coil, and are single-phase full-wave rectification Power is supplied to the device every half-wave, and the insulator includes an inner cylindrical portion fitted to the central column portion, and one end surface of the primary coil extending in a radial direction from the inner cylindrical portion. And a first insulator that separates from one of the secondary coils, and the inner cylinder fits into the first cylinder that separates one of the pair of secondary coils from the central column and the inner cylinder. Worn An outer cylindrical portion that separates the inner peripheral surface of the primary coil together with the inner cylindrical portion from the central column portion, and the other end surfaces of the primary coil that extend in a radial direction from the outer cylindrical portion are the pair of secondary coils. And a second insulator that separates the other of the pair of secondary coils from the central column portion. It is characterized by that. The coil conductor cross section is preferably a plate shape, but is not limited thereto.
[0013]
That is, the step-down transformer for a vehicle using the molded coil of the present invention divides the conventional bobbin-shaped insulator into a pair of flange-shaped insulators in order to ensure electrical insulation of the high-voltage primary coil. A primary coil having the same structure as the bobbin-shaped insulator housing is created by fitting the primary coil made of the outer tubular portion of the second insulator and then fitting the inner tubular portion of the first insulator into the outer tubular portion. can do. For this reason, like the conventional bobbin-shaped insulator housing coil, it is possible to realize good insulation protection of the primary coil with a simple manufacturing process and a small amount of insulating material used.
[0014]
However, when such a bobbin-shaped insulator is divided into two flange-shaped insulators by a cylindrical portion, a creeping discharge path between the primary coil and the central column portion of the core occurs at the divided end surface of the cylindrical portion, The creeping discharge distance from the primary coil to the core is greatly reduced as compared with the conventional bobbin-like insulator.
[0015]
Therefore, the present invention employs a structure in which both the cylindrical portions are fitted to each other by changing the diameters of the cylindrical portions of the both flange-shaped insulators and increasing the axial length of both the cylindrical portions. Furthermore, in this invention, it arrange | positions so that a primary coil may be pinched | interposed into an axial direction with a pair of secondary coil which feeds a single phase full-wave rectifier for every half wave, and one side of this pair of secondary coil is an inner cylinder part. A configuration is also employed in which electrical insulation is performed from the central column portion, and the other of the pair of secondary coils is electrically insulated from the central column portion by the outer cylinder portion. As a result, it is possible to eliminate the problem of a decrease in creeping discharge distance caused by the division of the bobbin-like insulator, and it is possible to realize a step-down transformer for a vehicle that uses a molded coil that is easy to manufacture and excellent in reliability.
[0016]
In a preferred embodiment, the inner gap between the inner peripheral end of the primary coil and the central column is set smaller than the outer gap between the side column of the core and the outer peripheral end of the primary coil. ing.
[0017]
As a result, even if the primary coil is vibrated or urged in the radial direction due to vehicle vibration or the like, the inner peripheral end of the primary coil is the outer cylinder portion of the insulator before the outer peripheral end of the primary coil abuts against the side column portion of the core. I will be in contact with you. Thereby, it can prevent that the outer peripheral end of a primary coil collides with the side pillar part of a core, and the insulation protection of the outer peripheral surface of a primary coil can be abbreviate | omitted. In addition, since the outer cylinder part of the second insulator is cantilevered by the flange part and doubled with the inner cylinder part of the first insulator between the central pillar part of the core, it has excellent shock absorption ing.
[0018]
In a preferred aspect, the inner cylinder part or the outer cylinder part separates the inner peripheral surface of the secondary coil from the central column part. That is, according to this aspect, the inner cylinder part or the outer cylinder part protrudes further to the axial secondary coil side than the flange part, and is interposed between the inner peripheral end of the secondary coil and the central column part of the core. Therefore, it is possible to prevent contact between the secondary coil and the central column and to protect the insulation of the inner peripheral surface of the secondary coil without increasing the number of members.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
A preferred embodiment of a vehicle step-down DC-DC converter device for a two-battery mounted vehicle using a vehicle step-down transformer using the molded coil of the present invention will be described with reference to the following embodiments.
[0020]
[Example 1]
The circuit configuration of the step-down DC-DC converter device of this embodiment will be described below with reference to FIG.
(Circuit configuration)
100 is a smoothing capacitor on the input side, 200 is an inverter, 300 is a transformer, 400 is a pair of diodes forming a rectifier, and 500 is a smoothing circuit. Reference numeral 501 denotes a smoothing circuit choke coil, and 502 a smoothing circuit smoothing capacitor. The transformer 300 has a core 1, a primary coil 2, and secondary coils 3 and 4. One end (common connection end) of the secondary coils 3 and 4 is grounded, and the other end (independent end) is connected to the choke coil 501 through a pair of diodes 400. Note that one end (common connection end) of the secondary coils 3 and 4 may be connected to the choke coil 501 through a pair of diodes 400, and the other end (independent end) may be grounded.
[0021]
The high-voltage and high-frequency voltage output from the inverter 200 is stepped down by the transformer 300. Both secondary coils 3 and 4 alternately output a half-wave rectified voltage to the low-voltage battery through the diode 400 and the smoothing circuit 500 every different half-wave periods. Since this type of DC-DC converter is well known, further explanation is omitted.
(Transformer structure)
Next, the transformer 300, which is the main part of this embodiment, will be described in detail with reference to FIGS. 2 is a schematic cross-sectional view taken along line AA of the transformer 300, and FIG. 3 is a schematic vertical cross-sectional view taken along line BB of the transformer 300.
[0022]
The core 1 of the transformer 300 is formed by combining an E-shaped lower core 11 and an upper core 12 each formed of sintered ferrite, and each has a rectangular parallelepiped base 13, a central column 14, and a pair of side columns. 15.
[0023]
The primary coil 2 and the secondary coils 3 and 4 are each a flat plate coil formed by bending a flat conductor wire in a spiral or ring shape in a plane direction parallel to the main surface thereof. As shown in FIG. 2, the coil is composed of a one-turn coil, and the secondary coil 3, the primary coil 2, and the secondary coil 4 are fitted in the columnar central column portion 14 in this order.
[0024]
The primary coil 2 and the secondary coils 3 and 4 are composed of a pair of flange-shaped insulators 5 and 6 formed in a substantially flange shape, and a pair of ring-plate-shaped ring plate insulators 7 and 8 so as to provide insulation between coils and a pair of cores. Insulated.
[0025]
The flange-like insulator 5 has an inner cylinder portion 51 and a flange plate portion 52, and the inner cylinder portion 51 is fitted to the central column portion 14. The flange 52 extends from the inner cylinder 51 in the radially outward direction and is interposed between the primary coil 2 and the secondary coil 3. The flange-like insulator 6 has an outer cylinder part 61 and a flange plate part 62, and the outer cylinder part 61 is fitted to the inner cylinder part 51. The flange 62 extends from the outer cylinder 61 in the radially outward direction and is interposed between the primary coil 2 and the secondary coil 4. The ring plate insulator 7 formed in a ring plate shape is fitted to the upper end portion of the inner cylinder portion 51 protruding upward from the inner peripheral end of the flange plate portion 52, and the base portion 13 and the secondary portion of the upper core 12. It is interposed between the coils 3. The ring plate insulator 8 formed in a ring plate shape is fitted to the lower end portion of the outer cylinder portion 61 that protrudes downward from the inner peripheral end of the flange plate portion 62, and is connected to the base portion 13 of the lower core 11 and the secondary portion. It is interposed between the coils 4. The assembly of the transformer 300 need not be described, and each coil and insulator may be assembled to the core 1 in order.
[0026]
Thereby, the inner peripheral surface and both end surfaces of the primary coil 2 are well insulated and protected by these insulators, and the secondary coils 3 and 4 are similarly well insulated and protected by these insulators. The insulation protection of the primary coil 2 can be realized by a simple process, and a small amount of insulating material can be used. Further, in this embodiment, since the inner cylinder portion 51 and the outer cylinder portion 61 are substantially overlapped, the central column portion 14 is passed through the gap between the flange-like insulators 5 and 6 from the inner peripheral surface of the primary coil 2. Therefore, the total length of the creeping discharge path reaching to can be significantly increased , and the creeping discharge can be satisfactorily prevented.
[0027]
Further, in this embodiment, the inner clearance between the inner peripheral end of the primary coil 2 and the central column portion 14 is set smaller than the outer clearance between the side column portion 15 and the outer peripheral end of the primary coil 2. . Thereby, even if the primary coil 2 is vibrated or urged in the radial direction due to vehicle vibration or the like, the outer peripheral end of the primary coil 2 does not abut against the side column portion 15 of the core 1, and the outer peripheral surface of the primary coil 2 is There is no need for insulation protection (including mechanical protection) by the insulator.
[0028]
In this embodiment, the upper end portion of the inner cylindrical portion 51 insulates and protects the inner peripheral surface of the secondary coil 3 from the central column portion 14, and the lower end portion of the outer cylindrical portion 61 covers the inner peripheral surface of the secondary coil 4. Since the insulation protection is provided from the central column portion 14, the secondary coils 3 and 4 can be well protected similarly to the primary coil 2.
[0029]
(Modification 1)
Another embodiment will be described below with reference to FIG.
[0030]
This embodiment is the same as the first embodiment shown in FIG. 1 except that the lower end portion of the inner cylinder portion 51 is further extended so that the inner peripheral surface of the secondary coil 4 extends from the central column portion 14 at the lower end portion of the inner cylinder portion 51. The difference is in the distance.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a step-down DC-DC converter device for a vehicle according to a first embodiment.
2 is a schematic longitudinal sectional view showing a transformer of Example 1. FIG.
3 is a cross-sectional view taken along line BB in FIG.
FIG. 4 is a schematic longitudinal sectional view showing a transformer according to modified embodiment 1 ;
[Explanation of symbols]
300 Transformer 1 Core 2 Primary coil 3 Secondary coil 4 Secondary coil 5 Flange-shaped insulator 6 Flange-shaped insulator 7 Ring plate insulator 8 Ring plate insulator 51 Inner cylindrical portion 52 鍔 plate portion 61 Outer tube portion 62 鍔 plate portion

Claims (3)

A core having an axial cross section formed in a letter shape, a primary coil and a secondary coil wound around a central column portion of the core, and an insulator for electrically insulating the primary coil from the core and the secondary coil. In a step-down transformer for a vehicle using a formed coil provided,
The pair of secondary coils are individually disposed on both sides in the axial direction of the primary coil, and feed the half-wave to the single-phase full-wave rectifier,
The insulator is
An inner cylinder part fitted to the central column part, and a first rib part extending radially from the inner cylinder part and separating one end surface of the primary coil from one of the pair of secondary coils And the inner cylinder part is a first insulator that separates one of the pair of secondary coils from the central column part,
An outer cylindrical portion that is fitted to the inner cylindrical portion and separates the inner peripheral surface of the primary coil together with the inner cylindrical portion from the central column portion, and extends radially from the outer cylindrical portion to The other end surface of the pair of secondary coils is spaced apart from the other of the pair of secondary coils, and one of the inner cylinder portion and the outer cylinder portion is the center column portion of the other pair of secondary coils. A second insulator spaced from the
A step-down transformer for a vehicle using a formed coil characterized by comprising: In the step-down transformer for a vehicle using the molded coil according to claim 1,
The inner gap between the inner peripheral end of the primary coil and the central column part is set to be smaller than the outer gap between the side column part of the core and the outer peripheral end of the primary coil. A step-down transformer for vehicles using a molded coil. In the step-down transformer for a vehicle using the molded coil according to claim 1,
The vehicular step-down transformer using a molded coil, wherein the inner cylinder part or the outer cylinder part separates the inner peripheral surface of the secondary coil from the central column part.

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