阅读说明：本技术 电抗器结构 (Reactor structure ) 是由 坂本达朗 于 2020-11-20 设计创作，主要内容包括：一种电抗器结构,在不阻断漏磁通的情况下增加电感值,并且,利用冷却器通过冷却构件对线圈和芯体进行直接冷却,从而提高冷却性能。用于对线圈(102)进行冷却的绕组冷却部(104a、104b)通过由非流动性材料构成的线圈冷却构件(230a、230b)与冷却器(210)接触,并且,用于对芯体(105)进行冷却的芯体冷却部(107a、107b)通过由非流动性材料构成的芯体冷却构件(220a、220b)与冷却器(210)接触,将线圈(102)和芯体(105)覆盖的树脂模制构件(201)对线圈(102)和芯体(105)进行保持,并且将线圈(102)和芯体(105)固定至冷却器(210)。(A reactor structure increases an inductance value without blocking leakage magnetic flux, and directly cools a coil and a core by a cooling member with a cooler, thereby improving cooling performance. A winding cooling portion (104a, 104b) for cooling a coil (102) is in contact with a cooler (210) through a coil cooling member (230a, 230b) composed of a non-flowable material, and a core cooling portion (107a, 107b) for cooling a core (105) is in contact with the cooler (210) through a core cooling member (220a, 220b) composed of a non-flowable material, a resin molding member (201) covering the coil (102) and the core (105) holds the coil (102) and the core (105), and fixes the coil (102) and the core (105) to the cooler (210).)

1. A reactor structure having a core around which a coil is wound, characterized in that,

a winding cooling portion for cooling the coil is in contact with the cooler through a coil cooling member composed of a non-flowable material,

a core cooling portion for cooling the core is in contact with the cooler through a core cooling member composed of a non-flowable material,

the resin mold member that covers the coil and the core holds the coil and the core, and fixes the coil and the core to the cooler.

2. The reactor structure according to claim 1,

a metal member is provided at a position spaced apart from the end of the coil and the end of the core by at least 10 mm.

3. The reactor structure according to claim 1 or 2,

the core is constructed of a plurality of core members,

the core is held by the resin mold member in a state where end portions of the plurality of core members are butted against each other.

4. The reactor structure according to any one of claims 1 to 3,

the core body is composed of an iron powder core body.

5. The reactor structure according to claim 4, characterized in that,

the iron powder core body is a sendust magnetic core.

6. The reactor structure according to any one of claims 1 to 5,

the driving frequency of the power conversion device using the reactor structure is 1kHz or more.

7. The reactor structure according to any one of claims 1 to 6,

the reactor structure is constituted by a magnetic coupling type reactor in which a plurality of the coils are differentially connected so that magnetic fluxes generated by the plurality of coils cancel each other.

Technical Field

The present application relates to a reactor structure.

Background

For example, an electric vehicle such as an electric vehicle or a hybrid vehicle includes a power conversion device for driving a motor using electric power of a high-voltage battery as motive power. A reactor is used in a power conversion device for various purposes such as smoothing, boosting, or voltage reduction of electric power.

In a reactor of a power conversion device for an electric vehicle, which requires a large power density, a loss density is large and forced cooling using a filler such as a potting agent is performed. The loss here is a loss of the reactor, and means a loss generated in a winding and a core constituting the reactor.

As a conventional reactor, it includes: a reactor main body including a core and a coil mounted on the core; a case that houses the reactor main body and has an opening through which a part of the reactor main body protrudes to the outside; a bus bar that is a conductive member electrically connected to the coil and covers a part of a side surface of the reactor main body protruding from the opening; a terminal block having an extended portion formed of a resin material in which a part of a bus bar is embedded and provided along an edge portion of an opening, and supporting an electrical connection portion between the bus bar and the outside (see patent document 1).

In addition, in patent document 1, the following method is often adopted: the core and the coil are provided in a case or the like in which a portion for preventing the flow of the filler is dug, and the filler is poured and cured. Next, the case is attached to a cooler of the power conversion device, and the coil and the core, which are heating elements, are cooled by the cooler through the filler and the case.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2019-121665

Disclosure of Invention

Technical problem to be solved by the invention

The size of the reactor is restricted by factors determined by heat dissipation and loss. In order to miniaturize the reactor, it is necessary to improve heat dissipation and reduce loss. The ripple current is a factor affecting the loss, and in order to reduce the loss, it is necessary to increase the inductance value and reduce the ripple current. However, in general, the reactor has to be increased in size in order to increase the inductance value. In order to improve heat dissipation, it is necessary to consider that the case is made of metal, and the heat generating element, i.e., the coil and the core are disposed as close as possible to the case, thereby reducing thermal resistance. However, since the metal member blocks leakage magnetic flux of the reactor, the inductance value decreases and the loss increases.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a reactor structure in which an inductance value is increased without blocking leakage magnetic flux, and a coil and a core are directly cooled by a cooling member using a cooler, thereby improving cooling performance.

Technical scheme for solving technical problem

A reactor structure disclosed in the present application has a core around which a coil is wound, wherein a winding cooling portion for cooling the coil is in contact with a cooler by a coil cooling member composed of a non-flowable material, and a core cooling portion for cooling the core is in contact with the cooler by a core cooling member composed of a non-flowable material, and a resin molding member that covers the coil and the core holds the coil and the core, and fixes the coil and the core to the cooler.

Effects of the invention

According to the reactor structure disclosed in the present application, it is possible to increase the inductance value without blocking the leakage magnetic flux, and to directly cool the coil and the core by the cooling member with the cooler, so that the cooling performance can be improved.

Drawings

Fig. 1 is a schematic diagram showing a configuration of a power converter according to a first embodiment.

Fig. 2 is an exploded perspective view showing a reactor structure according to the first embodiment.

Fig. 3 is a perspective view showing a configuration of a reactor main body according to the first embodiment.

Fig. 4 is a perspective view showing a configuration of a reactor main body according to the first embodiment.

Fig. 5 is a sectional view showing a reactor according to the first embodiment.

Fig. 6 is a perspective view showing a structure of a core of a reactor according to the first embodiment.

Fig. 7 is a perspective view showing a configuration of a reactor of a comparative example.

Fig. 8 is a cross-sectional view of a plane perpendicular to the X-axis direction of the reactor according to the first embodiment.

Fig. 9 is a cross-sectional view showing a plane perpendicular to the X-axis direction of the reactor structure of the comparative example.

Fig. 10 is a graph showing a relationship between an inductance value and a frequency.

Fig. 11 is a side view showing a case where a magnetic coupling type reactor is used as the reactor of the second embodiment.

Description of the symbols

2 a power conversion device;

4, a reactor;

102 a coil;

104a, 104b winding cooling parts;

105 a core body;

106a, 106b core members;

107a, 107b core cooling portions;

201 a resin molded member;

210 a cooler;

220a, 220b core cooling members;

230a, 230b coil cooling means.

Detailed Description

Implementation mode one

Next, the power conversion device of the present embodiment will be explained based on the drawings. In the drawings, the same or similar portions are denoted by the same reference numerals, and redundant description thereof is omitted. The present embodiment realizes miniaturization and cost reduction of a reactor used for a power conversion device. Fig. 1 is a schematic diagram showing a configuration of a power converter according to a first embodiment. In fig. 1, a power conversion device 2 is a single-switch boost DC/DC converter that boosts DC power input from a DC input power supply 1 and supplies the boosted DC power to a load 3.

The power conversion device 2 includes a boost reactor 4, semiconductor switching elements 5a, 5b, an input power smoothing capacitor 6, and an output power smoothing capacitor 7. The semiconductor switching elements 5a and 5b are connected in series, and a connection point (midpoint) N thereof is connected to one terminal of the winding of the boost reactor 4. The terminal of the winding of the boost reactor 4 on the side not connected to the connection point N of the semiconductor switching elements 5a and 5b is connected to the positive terminal of the input power smoothing capacitor 6. The terminal of the semiconductor switching element 5a not connected to the midpoint N is connected to the positive terminal of the output power smoothing capacitor 7. The terminal of the semiconductor switching element 5b not connected to the midpoint N is connected to the cathode terminal of the output power smoothing capacitor 7 and the cathode terminal of the input power smoothing capacitor 6.

The voltage boosting reactor 4 repeatedly holds or releases electric energy as magnetic energy to perform a voltage boosting operation by the switching operation of the semiconductor switching elements 5a and 5 b. Here, since the operation principle of the step-up DC/DC converter is well known, the description thereof is omitted.

Fig. 2 is an exploded perspective view showing the structure of the booster reactor 4. In fig. 2, the boost reactor 4 is constituted by a boost reactor main body 200, a cooler 210, core cooling members 220a, 220b, and coil cooling members 230a, 230 b. Further, the booster reactor main body 200 has the thermistor 101, the coil 102, the resin mold member 201, the screw 202, and the screw hole 203.

Fig. 3 and 4 are perspective views showing the structure of the boost reactor main body, fig. 3 is a perspective view seen from the lower side, and fig. 4 is a perspective view seen from the upper side. In fig. 2, the arrow direction of the Z axis is defined as an upper side and the opposite side is defined as a lower side, and the X axis and the Y axis are axes extending in a direction perpendicular to the Z axis. Further, in fig. 4, a state is shown in which resin mold member 201 is removed in boost reactor main body 200. In the figure, the booster reactor main body 200 is formed by covering the thermistor 101, the coil 102, and the core 105 with a resin mold member 201.

One end portions of the two windings 103a and 103b constituting the coil 102 are connected to each other at the outside, and the other end portions constitute terminals of the booster reactor 4. The windings 103a and 130b are wound around the core 105, and have a turn ratio of 1: 1. the windings 103a and 103b are wound so that the respective magnetic fluxes generated are oriented in the same direction (superposed connection) inside the core body 105.

Resin mold member 201 has a function of holding thermistor 101, coil 102, and core 105 and fixing booster reactor main body 200 to cooler 210. As shown in fig. 3, winding cooling portions 104a and 104b for cooling coil 102 and core cooling portions 107a and 107b for cooling core 105 are provided, and these portions are not covered by resin molding. Other portions may be provided not to be covered by the resin molding within a range not impairing the function. Although the winding cooling portions 104a and 104b and the core cooling portions 107a and 107b are provided in the reactor lower portion, the present invention is not limited to this. For example, as shown in fig. 5, the reactor may be provided on the upper U or the side surfaces S1 and S2. By providing the cooling portion at an appropriate position according to the shape of the reactor and the cooler 210, the cooling performance can be improved.

Winding cooling portions 104a, 104b and core cooling portions 107a, 107b are in contact with cooler 210 through core cooling members 220a, 220b and coil cooling members 230a, 230b, respectively. The core cooling members 220a and 220b and the coil cooling members 230a and 230b are each configured as an independent member, but the present invention is not limited to this, and may be integrated into one cooling member, for example. Further, as shown in fig. 2, seats 211a, 211b for placing core cooling members 220a, 220b are provided in the cooler 210.

The material of the cooling members constituting the core cooling members 220a and 220b and the coil cooling members 230a and 230b is a non-flowable material such as a semisolid or a solid, and is, for example, a silicone-based heat sink, a solidified silicone-based gap filler, or a heat sink lubricant. By using the non-flowable material as described above, it is not necessary to provide a hole-digging structure for preventing the flow of the cooling member, which is required when using a flowable material (potting agent). By eliminating the hole-digging structure, the metal member covering the side face of the reactor is not provided any more, and the inductance is increased, so that the reactor can be miniaturized.

Fig. 6 is a perspective view showing the structure of core 105 of boost reactor 4. The core 105 is constituted by two core members 106a, 106b, respective ends of which are in contact at core member end abutment portions 108a, 108 b. In this state, the resin mold member 201 fixes the core 105. Here, an example in which the core 105 is constituted by two core members is shown, but the present invention is not limited thereto.

Next, a technical problem in the booster reactor having the structure of the comparative example will be described. The reactor generates an induced voltage corresponding to a current change, and the ratio of the current change to the induced voltage is a self-inductance L. In the power conversion device 2, the induced voltage to be generated is determined by the input voltages Vin and Vout for each operation mode, and therefore, the boost reactor 4 in the boost operation generates a ripple current corresponding to the self-inductance L.

The increase in the ripple current causes an increase in the winding loss of the boost reactor 4 and an increase in the loss of the input power smoothing capacitor 6, the output power smoothing capacitor 7, and the semiconductor switching elements 5a and 5 b.

That is, regarding the relationship between the ripple current and the winding loss, the loss generated in the winding is divided into a direct current loss due to the direct current component and an alternating current loss due to the ripple component. When the ac loss is Wcoil _ ac [ W ], Rcoil [ Ω ] is a winding resistance, and Irip [ Arms ] is a ripple current value, the ac loss Wcoil _ ac [ W ] is expressed by the following expression (1).

Wcoil_ac＝Irip²×Rcoil……(1)

In this way, since the ac loss is proportional to the square of the ripple current value, an increase in the ripple current leads to an increase in the loss.

Note that, regarding the input power smoothing capacitor 6 and the output power smoothing capacitor 7, when the loss generated in the capacitors is Wco [ W ], ESRco [ Ω ] is a resistance component of the capacitors, and Ico [ Arms ] is a current flowing in the capacitors, the capacitance loss is expressed by the following expression (2).

Wco＝Ico²×ESRco……(2)

The current Ico flowing through the capacitor increases with the increase in the ripple current of the reactor together with the input power smoothing capacitor 6 and the output power smoothing capacitor 7, and therefore, if the ripple current increases, the loss of each increases.

Similarly, in the semiconductor switching element, when the ripple current of the reactor increases, the ripple of the current flowing through the semiconductor switching element also increases, and the loss of the member constituting the semiconductor switching element increases.

As is apparent from the above description, it is preferable to increase the self-inductance L and reduce the ripple current from the viewpoint of loss and heat generation.

The inductance L of the reactor is expressed by the following expression (3).

L＝N²×(μr·μ₀·S)/lc……(3)

Here, lc is the core magnetic path length, μ r is the specific permeability of the core, μ₀Is the vacuum permeability.

In order to increase the inductance L, in general, a method of increasing the number of turns N of the coil or a method of increasing the core sectional area S may be employed.

The main factors that restrict the size of the reactor are heat dissipation and loss. In miniaturizing the reactor, it is desirable to increase the inductance value and reduce the loss amount. However, when the inductance value is increased by the above method, there is a technical problem that the reactor is increased in size, and there is a limit to the size reduction.

Fig. 7 is a perspective view showing a structure of a voltage boosting reactor of a comparative example. In fig. 7, the coil and the core of the boost reactor main body 300 are the same as those of the boost reactor main body 200 shown in fig. 2. In fig. 7, a booster reactor main body 300 has a thermistor 101, a coil 102, a case 301, a filler 302, and a core molding member 303.

The core molding member 303 covers the core, and has a function of protecting the core surface and positioning the coil 102. The filler 302 is made of, for example, silicone potting agent, and has a function of cooling the coil 102 and the core and fixing the core. The housing 301 has a function of preventing the filler 302 from flowing out.

In order to improve heat radiation performance, a metal member such as aluminum is used for the case 301, and the case 301 is provided close to the coil 102 or the core, which is a heat generating body. In the case where a metal member exists near the reactor, the metal member blocks leakage magnetic flux generated by the reactor. Here, the leakage flux is a flux directly discharged into a space from a core or a coil of the reactor. The leakage flux also affects the inductance value, and when the leakage flux is reduced, the self-inductance value is reduced. Therefore, although the case 301 improves the heat radiation performance, there is a technical problem that the loss amount of the reactor increases.

The present embodiment is designed to solve the above-described problems, and the boost reactor 4 of the power conversion device 2 of the present embodiment can maintain high heat dissipation, and can utilize a large amount of leakage magnetic flux by using a resin member as a reactor holding mechanism. This can increase the inductance value without changing the structure of the coil and the core. Further, the loss of the reactor can be reduced, and the reactor can be miniaturized and produced at low cost.

Next, the effect of the boost reactor 4 of the power converter of the present embodiment will be described. Fig. 8 is a cross-sectional view of a plane perpendicular to the X-axis direction of the booster reactor of the present embodiment. Fig. 9 is a cross-sectional view showing a plane perpendicular to the X-axis direction of the booster reactor structure of the comparative example.

In fig. 9, in the booster reactor of the comparative example, since the filler 302 has a function of fixing the coil and the core, it is necessary to cover the side surface of the reactor with the case 301 made of metal. Therefore, the leakage magnetic flux 9 generated from the coil and the core is blocked by the case 301 in the Y-axis direction.

In contrast, in fig. 8, in the boost reactor of the present embodiment, by fixing the boost reactor main body 200 with the resin mold member 201, the function of fixing the cooling member can be eliminated, and the cooling surface can be localized. That is, in the present embodiment, as shown in fig. 8, the cooling surfaces are only three surfaces of the core cooling members 220a and 220b and the coil cooling member 230b, and therefore, the cooling surfaces can be localized. In contrast, in fig. 9, the cooling surface is formed as the entire filler 302, and therefore, the cooling surface cannot be localized because the cooling surface is not only the bottom surface of the coil 102 and the core 106 but also the side surfaces of the coil 102 and the core 106. Thus, in the present embodiment, a metal case covering the side surface of the reactor is not necessary. Therefore, the leakage magnetic flux 8 generated from the coil and the core can also be diffused in the Y-axis direction, and the inductance value increases because the amount of the magnetic flux is larger than the leakage magnetic flux 9 shown in fig. 9. In the present embodiment, the core, the coil, and the like are fixed to the cooler 210 by the fixing portion of the resin mold member 201.

In contrast to the coil and core of the voltage boosting reactor of the comparative example being cooled by cooler 310 via filler 302, case 301 and heat dissipation lubricant oil 320, coil 102 and core 105 of voltage boosting reactor 4 of the present embodiment are directly cooled by cooler 210 via coil cooling members 230a and 230b and core cooling members 220a and 220b, respectively. Therefore, the thermal resistance reaching the cooler 210 can be reduced, and the cooling performance can be improved.

Further, since the metal case is not required, the reactor main body can be downsized and can be produced at low cost.

In the power conversion device 2, when a large metal member such as a case or a case covering one surface of a reactor such as a bus is disposed in the vicinity of the boost reactor 4, the effect of the present embodiment is affected. In order to sufficiently exhibit the effects of the present embodiment, it is necessary to secure a region in which leakage magnetic flux can be generated. Preferably, the large metal member is spaced apart from the coil and the core end by at least 10mm, i.e., by at least 10mm from the coil and the core end, which are sources of magnetic flux, in addition to the surface having the cooling portion. However, if the metal member is a small metal member to which the terminal block or the like is fastened by a screw, the influence thereof can be ignored.

As shown in fig. 7, the cores of the boost reactors of the comparative examples are fixed by the filler 302, but the filler has a low hardness, and the cores of the core members 106a and 106b cannot be fixed in a state where the core member end butting portions 108a and 108b are in contact with each other only by the filler 302. Therefore, it is necessary to fix the core member end butting portions 108a, 108b by an adhesive. In contrast, in the booster reactor 4 of the present embodiment, the ends of the core members 106a and 106b are butted against each other and are molded by the resin mold member 201. Therefore, stress due to thermal contraction generated during molding can be continuously applied, and the core member end butting portions 108a and 108b can be fixed in a butted state. Therefore, there is no concern that the following occurs in the voltage boost reactor of the comparative example: since the adhesive is used, if the temperature becomes high, the adhesive may fail, and the reactor may fail. Thus, the reactor can be operated even at a higher temperature, and the reactor can be further downsized.

As the core in the booster reactor of the present embodiment, it is conceivable to use an iron powder core (dust core). The iron powder core body has high saturation magnetic density, is suitable for large electric power, and has small magnetic conductivity. Therefore, the ratio of the inductance value generated by the leakage flux to the inductance value generated by the core body becomes large, and therefore, the effect of increasing the inductance is exhibited. Particularly, when a Sendust core (Sendust) that is an iron powder core having a small magnetic permeability is used, a significant effect can be exhibited. However, the application object of the present embodiment is not limited to this, and ferrite, electromagnetic steel sheet, or the like having high magnetic permeability may be used as the core. This produces the same effects as described above.

Fig. 10 is a graph showing a relationship between an inductance value and a frequency, and shows a comparison between an inductance value of the boost reactor of the present embodiment and an inductance value of the boost reactor of the comparative example. In fig. 10, the horizontal axis represents frequency, the vertical axis represents a ratio of inductance based on the inductance at 100Hz of the voltage boosting reactor of the present embodiment, the broken line represents the voltage boosting reactor of the present embodiment, and the solid line represents the voltage boosting reactor of the comparative example. The metal member blocks the leakage magnetic flux due to an eddy current generated in the metal case, and the leakage magnetic flux is largely changed depending on the frequency (amount of change in magnetic flux). That is, as the frequency becomes higher, the effect of blocking the magnetic flux becomes larger. As shown in fig. 10, particularly, when the driving frequency of the semiconductor switching elements 5a and 5b of the power conversion device 2 is 1kHz or more, the reduction in inductance is small in the present embodiment, and the reduction ratio is large in the voltage boosting reactor of the comparative example. Therefore, in the present embodiment, the effect is particularly obtained when the driving frequency of the power converter is 1kHz or more.

As described above, according to the present embodiment, the inductance value can be increased and the loss can be reduced without changing the materials and structures of the coil and the core by providing the structure in which high heat radiation performance can be maintained and a large amount of leakage magnetic flux can be utilized. That is, according to the reactor structure of the present embodiment, by providing the structure in which the holding mechanism of the reactor is made of the resin member, the inductance value can be increased without interrupting the leakage magnetic flux. Further, since the coil and the core can be directly cooled by the cooling member using the cooler, the cooling performance can be improved. Further, the reactor structure can be miniaturized, so that inexpensive production can be performed.

Second embodiment

In the above description, the case where two windings 103a and 103b are connected in a superposed manner to form one coil is described with respect to the booster reactor main body 200 of the power conversion device. The superposition connection is premised on forming a magnetic circuit inside the core. In contrast, when the present invention is applied to a power conversion device and a reactor structure on the premise that a magnetic path is formed outside the core and leakage magnetic flux is used as inductance, a higher effect can be obtained. That is, the inductance value can be further increased. In a reactor that assumes that leakage magnetic flux is used as an inductor, the absolute amount of leakage magnetic flux increases, and the ratio of the leakage magnetic flux to the inductance value generated in the core increases. Therefore, in the present embodiment, a relatively large effect of increasing the leakage magnetic flux can be obtained.

For example, as an example of the power conversion device, a multistage boost converter including a boost reactor having a plurality of windings can be cited. As an example of the voltage boosting reactor, for example, a magnetic coupling type reactor may be considered in which magnetic fluxes generated in the respective windings are cancelled (differentially connected). Fig. 11 is a side view showing a case where a magnetic coupling type reactor is used as the step-up reactor. In fig. 11, a core 1102 is wound with a coil 1101, and generates a magnetic flux M. Further, the positional relationship among the cooling member, the cooler, and the resin mold member, the core 1102, and the coil 1101 is the same as that shown in the first embodiment.

Further, although the step-up DC/DC converter is shown as the circuit configuration of the power converter of the present embodiment, this is merely an example, and the power converter may be configured by another circuit such as an AC/DC converter circuit or an insulation type step-down DC/DC converter circuit. In this case, the same effects as described above can be obtained.

The number, size, material, and the like of the above-described constituent members can be appropriately changed.

In addition, although the present application describes various exemplary embodiments and examples, various features, modes, and functions described in one or more embodiments are not limited to the application to specific embodiments, and can be applied to the embodiments alone or in various combinations.

Therefore, countless modifications not illustrated are assumed to be within the technical scope disclosed in the present application. For example, the case where at least one component is modified, added, or omitted is included, and the case where at least one component is extracted and combined with the components of the other embodiments is also included.