Patent Description:
<CIT> (PTL <NUM>) is a prior art document that discloses a configuration of an on-vehicle transformer. The on-vehicle transformer described in PTL <NUM> includes a pipe, a transformer body and a plurality of coolers. The pipe forms a circulation path for refrigerant. The transformer body is arranged at some midpoint in a path of the pipe to house refrigerant together with a winding. The plurality of coolers are arranged in a distributed manner at some midpoint in the path of the pipe to cool the refrigerant by heat exchange with the air. The plurality of coolers are arranged in a distributed manner under a vehicle floor which is a passage for traveling wind.

<CIT> discloses a transformer, and in particular, to an in-vehicle transformer.

<CIT> discloses an auxiliary device for a cooler of a transformer, and more particularly to an oil flow indicating device for a transformer for instructing a flow state of oil.

In the on-vehicle transformer, when an insulating oil is used as the refrigerant, an oil flow relay is placed in a connection pipe through which the insulating oil flows. In order to prevent insufficient cooling of the transformer body, the oil flow relay operates when a flow rate of the insulating oil becomes equal to or less than a threshold value.

Furthermore, in the on-vehicle transformer, an insulating oil having small environmental load and high dependence of viscosity on temperature may be used in some cases. The insulating oil having high dependence of viscosity on temperature increases in viscosity and decreases in fluidity as the temperature becomes lower. Therefore, when the above-described insulating oil is used, the oil flow relay may erroneously detect an abnormality of the on-vehicle transformer at low temperature.

In order to reduce or prevent erroneous detection by the oil flow relay, the conventional on-vehicle transformer is provided with a thermometer to perform control using a value measured by the thermometer.

The present invention has been made in view of the above-described problem, and an object of the present invention is to provide an on-vehicle transformer and an oil flow relay that can reduce or prevent erroneous detection by the oil flow relay at low temperature, without providing a thermometer.

The present invention is defined by its independent claims <NUM> and <NUM>. An on-vehicle transformer based on claim <NUM> of the present invention includes: a transformer body; a tank; an insulating oil; a cooler; a connection pipe; a pump; and an oil flow relay. The tank houses the transformer body. The insulating oil is filled into the tank to cool the transformer body. The cooler cools the insulating oil. The connection pipe connects the tank to the cooler. The pump is placed in the connection pipe to circulate the insulating oil between the tank and the cooler. The oil flow relay is placed on a discharge portion side of the pump in the connection pipe. The oil flow relay includes: a blade member; a movable contactor; and a fixed contact. The blade member is arranged in the connection pipe and supported so as to be rotatable about a central axis orthogonal to the connection pipe. The movable contactor has a movable contact and rotates about the central axis with rotation of the blade member. The fixed contact is located on a rotation path of the movable contact. The oil flow relay is configured such that an operating flow rate in the oil flow relay becomes smaller as a temperature of the insulating oil becomes lower, the operating flow rate being a flow rate of the insulating oil flowing through the connection pipe when the movable contact and the fixed contact come into contact with each other, wherein the blade member has a shaft portion extending on the central axis and is supported by a bearing portion that is in sliding contact with the shaft portion, and the shaft portion is made of a material having a thermal expansion coefficient higher than that of the bearing portion.

According to the present invention, the oil flow relay is configured such that the operating flow rate of the oil flow relay becomes smaller as the temperature of the insulating oil flowing through the oil flow relay becomes lower, and thus, it is possible to reduce or prevent erroneous detection by the oil flow relay at low temperature, without providing a thermometer.

An on-vehicle transformer and an oil flow relay according to each embodiment of the present invention will be described hereinafter with reference to the drawings.

In the description of the embodiments below, the same or corresponding portions in the drawings are denoted by the same reference characters and description thereof will not be repeated.

<FIG> is a system diagram showing a configuration of an on-vehicle transformer according to a first embodiment of the present invention. <FIG> is a perspective view showing a state of an oil flow relay placed in the on-vehicle transformer according to the first embodiment of the present invention at high temperature and in a pump stop state. <FIG> is a perspective view showing a state of the oil flow relay placed in the on-vehicle transformer according to the first embodiment of the present invention at high temperature and in a pump operation state. <FIG> is a schematic view when an internal structure of the oil flow relay according to the first embodiment of the present invention is viewed from a central axis direction. <FIG> is a perspective view showing a shape of a blade member of the oil flow relay according to the first embodiment of the present invention at high temperature. <FIG> is a perspective view showing a state of the oil flow relay placed in the on-vehicle transformer according to the first embodiment of the present invention at low temperature and in the pump stop state.

In the description of the embodiments below, "at high temperature" refers to the time when a temperature of an insulating oil flowing through the oil flow relay is relatively high, and "at low temperature" refers to the time when the temperature of the insulating oil flowing through the oil flow relay is relatively low.

As shown in <FIG>, an on-vehicle transformer <NUM> according to the first embodiment of the present invention includes a transformer body <NUM>, a tank <NUM>, an insulating oil <NUM>, a cooler <NUM>, a connection pipe <NUM>, a pump <NUM>, and an oil flow relay <NUM>.

On-vehicle transformer <NUM> according to the present embodiment is mounted on, for example, a railway vehicle. The operation of on-vehicle transformer <NUM> mounted on a railway vehicle stops at a higher frequency than a power transformer. Therefore, in on-vehicle transformer <NUM>, it is important to reduce or prevent erroneous detection by the oil flow relay at the start of operation, i.e., at low temperature.

When on-vehicle transformer <NUM> is mounted on a railway vehicle, transformer body <NUM> converts a high voltage current supplied from an overhead wire into a low voltage current and supplies the current to a motor, an air-conditioning facility or the like used in the railway vehicle. Transformer body <NUM> is housed in tank <NUM>.

Insulating oil <NUM> is filled into tank <NUM> to cool transformer body <NUM>. Since on-vehicle transformer <NUM> may be mounted on a railway vehicle, insulating oil <NUM> is preferably a flame-resistant insulating oil from a safety point of view. Examples of insulating oil <NUM> include an ester oil that is a vegetable oil, a silicone oil and the like. The number of users who select the ester oil as insulating oil <NUM> is on the increase. The ester oil has higher dependence of viscosity on temperature than that of the silicone oil.

Insulating oil <NUM> having high dependence of viscosity on temperature, such as the ester oil, has a remarkable tendency of decreasing in viscosity as the temperature becomes higher, and increasing in viscosity as the temperature becomes lower. Therefore, in connection pipe <NUM>, insulating oil <NUM> having high dependence of viscosity on temperature, such as the ester oil, decreases in viscosity and increases in fluidity as the temperature becomes higher, and increases in viscosity and decreases in fluidity as the temperature becomes lower.

Cooler <NUM> cools insulating oil <NUM>. Examples of cooler <NUM> include an air-cooled type cooler and the like, although not particularly limited.

Connection pipe <NUM> connects tank <NUM> to cooler <NUM>. Connection pipe <NUM> is composed of a first connection pipe for conveying insulating oil <NUM> from cooler <NUM> to tank <NUM>, and a second connection pipe for conveying insulating oil <NUM> from tank <NUM> to cooler <NUM>.

Pump <NUM> is placed in connection pipe <NUM> to circulate insulating oil <NUM> between tank <NUM> and cooler <NUM>. In the present embodiment, pump <NUM> is placed in the second connection pipe.

Insulating oil <NUM> having an increased temperature as a result of cooling of transformer body <NUM> housed in tank <NUM> is conveyed from tank <NUM> through the second connection pipe of connection pipe <NUM> to cooler <NUM>, where insulating oil <NUM> is cooled. Cooled insulating oil <NUM> is conveyed from cooler <NUM> through the first connection pipe of connection pipe <NUM> to tank <NUM>, where insulating oil <NUM> cools transformer body <NUM> again.

Oil flow relay <NUM> is placed on the discharge portion side of pump <NUM> in connection pipe <NUM>. In the present embodiment, oil flow relay <NUM> is placed in the second connection pipe of connection pipe <NUM>. Oil flow relay <NUM> is provided between pump <NUM> and cooler <NUM>.

As shown in <FIG>, oil flow relay <NUM> according to the first embodiment of the present invention includes a blade member <NUM>, a movable contactor <NUM> and a fixed contact <NUM>.

As shown in <FIG> and <FIG>, blade member <NUM> is arranged in the pipe in which insulating oil <NUM> flows, and is supported so as to be rotatable about a central axis C orthogonal to the pipe. In on-vehicle transformer <NUM> according to the first embodiment, blade member <NUM> is arranged in connection pipe <NUM> and supported so as to be rotatable about central axis C orthogonal to connection pipe <NUM>. Although <FIG> shows a direction of a flow of insulating oil <NUM> by an arrow, insulating oil <NUM> is not flowing in the state shown in <FIG>.

Blade member <NUM> includes a plate-shaped portion extending from central axis C in a radial direction, and a main surface of the plate-shaped portion has a substantially rectangular outer shape. A radially outward edge portion of the plate-shaped portion is curved radially outward in the shape of an arc.

As shown in <FIG>, when a flow rate of insulating oil <NUM> becomes equal to or more than a predetermined rate, blade member <NUM> rotates about above-described central axis C, and thus, the plate-shaped portion of blade member <NUM> in a pump operation state becomes substantially horizontal along a direction of extension of the pipe in which oil flow relay <NUM> is placed, i.e., connection pipe <NUM>.

As shown in <FIG>, inside oil flow relay <NUM>, movable contactor <NUM> has a movable contact 164c and rotates about above-described central axis C with rotation of blade member <NUM>. A hollow portion <NUM> is formed in oil flow relay <NUM> such that movable contactor <NUM> can rotate.

Fixed contact <NUM> is located on a rotation path of movable contact 164c. In <FIG>, a position of movable contactor <NUM> at high temperature and during operation of pump <NUM> is indicated by a solid line, and each of a position of movable contactor <NUM> when movable contact 164c and fixed contact <NUM> come into contact with each other and a position of movable contactor <NUM> when pump <NUM> is not operating is indicated by a dotted line.

As shown in <FIG>, in the present embodiment, blade member <NUM> includes a first plate-shaped portion 162a and a second plate-shaped portion 162b as the plate-shaped portion. In the present embodiment, first plate-shaped portion 162a and second plate-shaped portion 162b have substantially the same shape at high temperature. However, first plate-shaped portion 162a and second plate-shaped portion 162b may have different shapes.

First plate-shaped portion 162a extends from above-described central axis C in a radial direction of above-described central axis C. At high temperature, a main surface of first plate-shaped portion 162a has a substantially rectangular outer shape. A radially outward edge portion of first plate-shaped portion 162a is curved radially outward.

Second plate-shaped portion 162b extends from above-described central axis C in the above-described radial direction and is joined to the downstream side of first plate-shaped portion 162a in the direction of the flow of insulating oil <NUM>. That is, second plate-shaped portion 162b extends from above-described central axis C in the above-described radial direction and is joined to a side of first plate-shaped portion 162a opposite to the pump <NUM> side.

At high temperature, a main surface of second plate-shaped portion 162b has a substantially rectangular outer shape. A radially outward edge portion of second plate-shaped portion 162b is curved radially outward.

Blade member <NUM> further has a shaft portion 162c extending on above-described central axis C. Blade member <NUM> may be formed by joining shaft portion 162c to each of first plate-shaped portion 162a and second plate-shaped portion 162b. In addition, shaft portion 162c and one of first plate-shaped portion 162a and second plate-shaped portion 162b may be formed as an integrated member.

Blade member <NUM> is supported by a bearing portion <NUM> that is in sliding contact with shaft portion 162c. In the present embodiment, bearing portion <NUM> has a cylindrical shape. However, the shape of bearing portion <NUM> is not particularly limited as long as bearing portion <NUM> has a shape of being in sliding contact with shaft portion 162c. In addition, as shown in <FIG>, bearing portion <NUM> is exposed to the outside of oil flow relay <NUM>. However, bearing portion <NUM> may be housed in oil flow relay <NUM>.

First plate-shaped portion 162a is made of a material having a thermal expansion coefficient higher than that of second plate-shaped portion 162b. Although each of first plate-shaped portion 162a and second plate-shaped portion 162b is made of a metal material or a resin material, the present invention is not limited thereto. When first plate-shaped portion 162a and second plate-shaped portion 162b are made of metal materials having different thermal expansion coefficients, a so-called bimetal is formed.

Since first plate-shaped portion 162a is made of a material having a thermal expansion coefficient higher than that of second plate-shaped portion 162b, first plate-shaped portion 162a contracts more greatly than second plate-shaped portion 162b at low temperature as shown in <FIG>, and thus, blade member <NUM> is curved to protrude to the second plate-shaped portion 162b side. Therefore, as the temperature becomes lower, blade member <NUM> is more likely to receive the rotational force from flowing insulating oil <NUM>. Thus, when the flow rate is small due to an increase in viscosity of insulating oil <NUM> at low temperature, the rotational force of blade member <NUM> can be supplemented.

With the above-described configuration, oil flow relay <NUM> according to the present embodiment is configured such that an operating flow rate of oil flow relay <NUM> becomes smaller as the temperature of insulating oil <NUM> becomes lower, the operating flow rate being a flow rate of insulating oil <NUM> flowing through the above-described pipe when movable contact 164c and fixed contact <NUM> come into contact with each other. That is, oil flow relay <NUM> in on-vehicle transformer <NUM> according to the present embodiment is configured such that the operating flow rate of oil flow relay <NUM> becomes smaller as the temperature of insulating oil <NUM> becomes lower, the operating flow rate being a flow rate of insulating oil <NUM> flowing through connection pipe <NUM> when movable contact 164c and fixed contact <NUM> come into contact with each other.

Specifically, as the temperature becomes lower, blade member <NUM> is curved and is more likely to receive the rotational force from flowing insulating oil <NUM>, and thus, the rotational force of blade member <NUM> obtained from insulating oil <NUM> having a decreased flow rate due to an increase in viscosity can be supplemented and the flow rate of insulating oil <NUM> flowing through connection pipe <NUM> when movable contact 164c and fixed contact <NUM> come into contact with each other can be reduced. That is, the operating flow rate of oil flow relay <NUM> can be made smaller as the temperature of insulating oil <NUM> becomes lower.

Now, description will be given of an experiment example performed to check a correlation between the operating flow rate of oil flow relay <NUM> according to the present embodiment and the temperature of the insulating oil.

<FIG> is a graph showing transition of each of the flow rate of the insulating oil in the connection pipe and the operating flow rate of the oil flow relay with respect to the temperature of the insulating oil flowing through the connection pipe. In <FIG>, the horizontal axis represents the temperature (°C) of the insulating oil, and the vertical axis represents each flow rate (L/min). During the experiment, the operation condition of pump <NUM> is kept constant and pump <NUM> operates normally.

As shown in <FIG>, the operating flow rate of oil flow relay <NUM> became smaller as the temperature of insulating oil <NUM> became lower. It could be confirmed from the result of the experiment that, in on-vehicle transformer <NUM> according to the present embodiment, when pump <NUM> operates normally and the temperature of insulating oil <NUM> is equal to or higher than -<NUM>, the flow rate of insulating oil <NUM> in connection pipe <NUM> does not fall below the operating flow rate of oil flow relay <NUM>, and thus, erroneous detection of an abnormality of on-vehicle transformer <NUM> by oil flow relay <NUM> can be reduced or prevented.

As described above, on-vehicle transformer <NUM> and oil flow relay <NUM> according to the present embodiment are configured such that the operating flow rate of oil flow relay <NUM> becomes smaller as the temperature of insulating oil <NUM> becomes lower. Therefore, on-vehicle transformer <NUM> and oil flow relay <NUM> according to the present embodiment can reduce or prevent erroneous detection by the oil flow relay at low temperature, without providing a thermometer. This can eliminate the need for providing placement space for a thermometer, which can lead to a reduction in size of on-vehicle transformer <NUM>.

Furthermore, a railway vehicle on which on-vehicle transformer <NUM> according to the present embodiment having reduced size and mass is mounted can travel faster and can travel with a larger number of cargo and passengers.

In the present embodiment, first plate-shaped portion 162a is made of a material having a thermal expansion coefficient higher than that of second plate-shaped portion 162b. Therefore, when the temperature of insulating oil <NUM> decreases, blade member <NUM> can be deformed to receive the greater rotational force from the flow of insulating oil <NUM>. Thus, the operating flow rate of oil flow relay <NUM> can be made smaller as the temperature of insulating oil <NUM> becomes lower.

An on-vehicle transformer and an oil flow relay according to a second embodiment of the present invention will be described below. The on-vehicle transformer and the oil flow relay according to the second embodiment of the present invention are different from on-vehicle transformer <NUM> and oil flow relay <NUM> according to the first embodiment of the present invention mainly in terms of the feature for making the operating flow rate smaller as the temperature of the insulating oil becomes lower. Therefore, description of the features similar to those of on-vehicle transformer <NUM> and oil flow relay <NUM> according to the first embodiment of the present invention will not be repeated.

<FIG> is a schematic view showing a compressive stress generated between the shaft portion and the bearing portion at high temperature in the oil flow relay according to the second embodiment of the present invention, when viewed from the central axis direction. <FIG> is a schematic view showing a compressive stress generated between the shaft portion and the bearing portion at low temperature in the oil flow relay according to the second embodiment of the present invention, when viewed from the central axis direction.

In the on-vehicle transformer and the oil flow relay according to the second embodiment of the present invention, the plate-shaped portions of blade member <NUM> are formed as an integrated member.

In the on-vehicle transformer and the oil flow relay according to the second embodiment of the present invention, shaft portion 162c is made of a material having a thermal expansion coefficient higher than that of bearing portion <NUM>. Although each of shaft portion 162c and bearing portion <NUM> is made of a metal material or a resin material, the material of each of shaft portion 162c and bearing portion <NUM> is not limited thereto.

In the present embodiment, shaft portion 162c is made of a material having a thermal expansion coefficient higher than that of bearing portion <NUM>. Therefore, shaft portion 162c contracts more greatly than bearing portion <NUM> at low temperature.

As a result, the compressive stress generated between shaft portion 162c and bearing portion <NUM> at low temperature shown in <FIG> is smaller than the compressive stress generated between shaft portion 162c and bearing portion <NUM> at high temperature shown in <FIG>. Therefore, the rotational force necessary for rotation of blade member <NUM> is reduced as the temperature becomes lower.

With the above-described configuration, the rotational force necessary for rotation of blade member <NUM> can be reduced as the temperature becomes lower. Therefore, even when the rotational force of blade member <NUM> obtained from insulating oil <NUM> having a decreased flow rate due to an increase in viscosity is reduced, blade member <NUM> can rotate. As a result, the flow rate of insulating oil <NUM> flowing through connection pipe <NUM> when movable contact 164c and fixed contact <NUM> come into contact with each other can be reduced. That is, the operating flow rate of the oil flow relay can be made smaller as the temperature of insulating oil <NUM> becomes lower.

In the present embodiment, shaft portion 162c is made of a material having a thermal expansion coefficient higher than that of bearing portion <NUM>. Therefore, when the temperature of insulating oil <NUM> decreases, the rotational force necessary for rotation of blade member <NUM> can be reduced. Thus, the operating flow rate of the oil flow relay can be made smaller as the temperature of insulating oil <NUM> becomes lower.

Claim 1:
An on-vehicle transformer (<NUM>) comprising:
a transformer body (<NUM>);
a tank (<NUM>) to house the transformer body (<NUM>);
an insulating oil (<NUM>) filled into the tank (<NUM>) to cool the transformer body (<NUM>);
a cooler (<NUM>) to cool the insulating oil (<NUM>);
a connection pipe (<NUM>) to connect the tank (<NUM>) to the cooler (<NUM>);
a pump (<NUM>) placed in the connection pipe (<NUM>) to circulate the insulating oil (<NUM>) between the tank (<NUM>) and the cooler (<NUM>); and characterized in that
an oil flow relay (<NUM>) being placed on a discharge portion side of the pump (<NUM>) in the connection pipe (<NUM>),
the oil flow relay (<NUM>) including:
a blade member (<NUM>) arranged in the connection pipe (<NUM>) and supported so as to be rotatable about a central axis (C) orthogonal to the connection pipe (<NUM>);
a movable contactor (<NUM>) having a movable contact (164c) and rotating about the central axis (C) with rotation of the blade member (<NUM>); and
a fixed contact (<NUM>) located on a rotation path of the movable contact (164c), wherein
the oil flow relay (<NUM>) is configured such that an operating flow rate in the oil flow relay (<NUM>) becomes smaller as a temperature of the insulating oil (<NUM>) becomes lower, the operating flow rate being a flow rate of the insulating oil (<NUM>) flowing through the connection pipe (<NUM>) when the movable contact (164c) and the fixed contact (<NUM>) come into contact with each other, wherein the blade member (<NUM>) has a shaft portion (162c) extending on the central axis (C) and is supported by a bearing portion (<NUM>) that is in sliding contact with the shaft portion (162c), and
the shaft portion (162c) is made of a material having a thermal expansion coefficient higher than that of the bearing portion (<NUM>).