Patent Description:
Shunt resistors have conventionally been known such as that described in <CIT>. As shown in <FIG>, the shunt resistor <NUM> includes two plate-shaped base materials joined by welding 101a with a resistance element <NUM> with the resistance element <NUM> therebetween and a measurement terminal portion <NUM> joined to each of the base materials <NUM> by welding 103a. It is noted that the reference sign 102a designates a circular bolt hole for a shaft part of an insulated bolt not shown to pass therethrough.

A shunt resistor and method for manufacturing same is also known from <CIT>, <CIT>, and <CIT>.

Incidentally, when a current flows through the above-described shunt resistor <NUM>, the resistance element <NUM> generates heat and thereby undergoes a change in the resistance value depending on the heat generation temperature. To address this, the resistance element <NUM> is required to have a lower resistance value in order not to result in an increase in the heat generation temperature. It is said, for example, that if a large current of <NUM> A flows through the shunt resistor <NUM>, the resistance element <NUM> preferably has a resistance value of about <NUM>µΩ, and if a large current of <NUM> A flows through the shunt resistor <NUM>, the resistance element <NUM> preferably has a resistance value of about <NUM>µΩ to <NUM>µΩ.

Here, since it is known that the resistance value of the resistance element <NUM> varies depending on the size of the resistance element <NUM> itself, a method for adjusting the resistance value of the resistance element <NUM> has commonly been known in which a recess-shaped notched portion 101b is provided in the resistance element <NUM> to reduce the size of the resistance element <NUM> itself, as shown in <FIG>.

In such a method, however, when a current flows from the base material <NUM> shown on the left side to the base material <NUM> shown on the right side as shown in <FIG> (see the direction indicated by the arrow Y10), since the current does not flow in the notched portion 101b provided in the resistance element <NUM>, there has been a problem such that the current value may not be measured accurately.

Hence, it is considered to reduce the width W10 (see <FIG>) of the resistance element <NUM> in order to lower the resistance value of the resistance element <NUM>. For example, it is required that the resistance element <NUM> has a width W10 (see <FIG>) of about <NUM> so as to have a resistance value of <NUM>µΩ, while the resistance element <NUM> has a width W10 (see <FIG>) of about <NUM> so as to have a resistance value of <NUM>µΩ to <NUM>µΩ.

However, thus reducing the width W10 (see <FIG>) of the resistance element <NUM> suffers from a problem, for example, that it is very difficult to join the resistance element <NUM> and the two base materials <NUM> by welding 101a of the resistance element <NUM>, with the resistance element being sandwiched between the two base materials <NUM>. In particular, manufacturing of conventional shunt resistors <NUM>, in which a continuous welding method is employed, significantly suffers from this problem. That is, in the continuous welding method, as shown in <FIG>, a long object LO with a resistance element <NUM> between two base materials <NUM> wound around a feed roll KR1 is fed from the feed roll KR1 in the direction indicated by the arrow Y11, and within the fed long object LO, portions in which the resistance element <NUM> is in close proximity to the two respective base materials <NUM> undergo welding 101a using an electron beam DE. As a result, this causes the two base materials <NUM> with the resistance element <NUM> therebetween to be joined by welding 101a to the resistance element <NUM>. It is noted that the long object LO1 after welding using an electron beam DE is to be wound around a take-up roll MR, as shown in <FIG>. Then, the long object LO1 wound around the take-up roll MR is to be wound around a feed roll KR2, as shown in <FIG>, and then fed from the feed roll KR2 in the direction indicated by the arrow Y12. The long object LO1 thus fed from the feed roll KR2 is to be cut by a cutting blade not shown at predetermined intervals in the direction perpendicular to the feed direction (indicated by the arrow Y12 in <FIG>) (see C10, C11 shown in <FIG>). After thus cutting the long object LO1 at predetermined intervals, a bolt hole 102a (see <FIG>) is to be provided in a vertically penetrating manner in each of the base materials <NUM> of each cut piece S, and further a measurement terminal portion <NUM> is to be joined by welding 103a (see <FIG>) to each of the base materials <NUM>, whereby such a shunt resistor <NUM> as shown in <FIG> is manufactured.

However, in such a continuous welding method as above, since the long object LO with the resistance element <NUM> between the two base materials <NUM> is fed continuously from the feed roll KR1, sufficient allowances for welding are required to join the resistance element <NUM> and the two base materials <NUM> reliably by welding 101a. For this reason, reducing the width W10 (see <FIG>) of the resistance element <NUM> suffers from a problem, for example, that sufficient allowances for welding are not provided and poor joints may occur, whereby the current value may not be measured accurately.

The present invention has hence been made in consideration of the above-described problem, and an object thereof is to provide a shunt resistor capable of measuring a current value accurately even when a large current flows therethrough, and a method for manufacturing such a shunt resistor.

The foregoing object of the present invention is achieved by the following means. It is noted that reference signs in the embodiments to be described hereinafter are added in parentheses, but the present invention is not intended to be limited thereto.

The invention of claim <NUM> is characterized by including:.

In accordance with the invention of claim <NUM>, the shunt resistor (<NUM>) according to claim <NUM> is also characterized in that
the resistance element (<NUM>) is provided with protruding portions (first protruding portion 10a, second protruding portion 10b) that protrude from the longitudinal side surfaces (one side surface 11a, the other side surface 11b) of the two base materials (<NUM>).

On the other hand, the invention of claim <NUM> is a method for manufacturing a shunt resistor according to claim <NUM> and is characterized by including:.

Next will be described advantageous effects of the present invention based on designation by the reference signs in the drawings. It is noted that reference signs in the embodiments to be described hereinafter are added in parentheses, but the present invention is not intended to be limited thereto.

In accordance with the invention of claim <NUM>, since the resistance element (<NUM>) is provided with the protruding portion (first protruding portion 10a) that protrudes from at least one (11a) of the longitudinal side surfaces (one side surface 11a, the other side surface 11b) of the two base materials (<NUM>), the two base materials (<NUM>) and the protruding portion (first protruding portion 10a) of the resistance element (<NUM>) can be clamped by a well-known clamping mechanism not shown. This allows to join the two base materials (<NUM>) and the resistance element (<NUM>) therebetween by welding (10e) while ensuring a sufficient welding bead width, whereby this makes it possible to realize welding of high quality in which poor joints are less likely to occur.

The present invention can thus achieve an accurate current value measurement even when a large current flows.

Also, in accordance with the invention of claim <NUM>, since the resistance element (<NUM>) is provided with the protruding portions (first protruding portion 10a, second protruding portion 10b) that protrude from the longitudinal side surfaces (one side surface 11a, the other side surface 11b) of the two base materials (<NUM>), the resistance element (<NUM>) can be clamped stably by a well-known clamping mechanism not shown.

On the other hand, in accordance with the invention of claim <NUM>, the resistance element (<NUM>) is formed to be provided with the protruding portion (first protruding portion 10a) that protrudes from at least one (11a) of the longitudinal side surfaces (one side surface 11a, the other side surface 11b) of the two base materials (<NUM>) when the resistance element (<NUM>) is sandwiched between the two base materials (<NUM>) (see <FIG>), and the protruding portion (first protruding portion 10a) of the resistance element (<NUM>) and the two base materials (<NUM>) are clamped and joined by welding (10e) when joining by welding (10e) the two base materials (<NUM>) to the resistance element (<NUM>) with the resistance element (<NUM>) therebetween (see <FIG>), which allows to join the two base materials (<NUM>) and the resistance element (<NUM>) therebetween by welding (10e) while ensuring a sufficient welding bead width, whereby makes it possible to realize welding of high quality in which poor joints are less likely to occur.

An embodiment of a shunt resistor according to the present invention will hereinafter be described specifically with reference to the accompanying drawings. It is noted that in the following description, reference to vertical and horizontal directions will denote the vertical and horizontal directions in a front view of the drawings.

The shunt resistor according to this embodiment is particularly used to measure the current value on a current path through which a large current flows from a battery for high-voltage applications to a motor circuit that are used in, for example, electric vehicles (EVs), hybrid vehicles (HVs), and plug-in hybrid vehicles (PHVs), the shunt resistor <NUM> including a resistance element <NUM>, two base materials <NUM> formed integrally by welding 10e with the resistance element <NUM> therebetween, and a measurement terminal <NUM> fixed by welding 12a in a standing manner on each of the two base materials <NUM>, as shown in <FIG>.

The resistance element <NUM> can withstand a large current of even <NUM> A, and formed in, for example, a thickened and shortened rectangular shape with a thickness of about <NUM> to <NUM> as shown in <FIG>, while having a reduced width W1 of about <NUM> as shown in <FIG>. Further, the resistance element <NUM> is preferably formed of, for example, Cu-Mn alloy, Cu-Ni alloy, or Ni-Cr alloy, having a resistance value of about <NUM>µΩ to <NUM>µΩ so as to withstand a large current of even <NUM> A.

As shown in <FIG>, on the upper side of the thus formed resistance element <NUM> is provided a first protruding portion 10a that protrudes outward from one longitudinal side surface 11a (upper surface in the drawing) of the two base materials <NUM> when the resistance element <NUM> is sandwiched between lateral side surfaces 11c of the two respective base materials <NUM> (the right side surface of the base material <NUM> on the left side and the left side surface of the base material <NUM> on the right side in the drawing). As shown in <FIG>, on the lower side of the resistance element <NUM> is further provided a second protruding portion 10b that protrudes outward from the other longitudinal side surface 11b (lower surface in the drawing) of the two base materials <NUM> when the resistance element <NUM> is sandwiched between lateral side surfaces 11c of the two respective base materials <NUM> (the right side surface of the base material <NUM> on the left side and the left side surface of the base material <NUM> on the right side in the drawing).

Incidentally, in the thus arranged resistance element <NUM>, the first protruding portion 10a is provided so as to have a height (length) H1 (see <FIG>) of <NUM> to <NUM>, and the second protruding portion 10b is also provided so as to have a height (length) H2 (see <FIG>) of <NUM> to <NUM>. It is noted that the height (length) H1 (see <FIG>) of the first protruding portion 10a and the height (length) H2 (see <FIG>) of the second protruding portion 10b may be set to have the same value or set to have respective different values.

On the other hand, as shown in <FIG>, the resistance element <NUM> has left and right side surfaces 10c, 10d that contact with the lateral side surfaces 11c of the two respective base materials <NUM> (the right side surface of the base material <NUM> on the left side and the left side surface of the base material <NUM> on the right side in the drawing) when the resistance element <NUM> is sandwiched between the side surfaces 11c of the two base materials <NUM>, in which the base material <NUM> on the left side in the drawing is joined by welding 10e to the left side surface 10c of the resistance element <NUM>, while the base material <NUM> on the right side in the drawing is joined by welding 10e to the right side surface 10c of the resistance element <NUM>. This causes the resistance element <NUM> and the two base materials <NUM> to be formed integrally by welding 10e.

The base materials <NUM> are so-called bus bars, made of metal such as copper, and formed in, for example, a thickened and lengthened rectangular shape with a thickness of about <NUM> to <NUM>, as shown in <FIG>. Closer to the other lateral side surface 11d of each of the base materials <NUM> (opposite to the joint with the resistance element <NUM>) is formed in a vertically penetrating manner a circular bolt hole 11e for a shaft part of an insulated bolt not shown to pass therethrough.

The measurement terminal <NUM>, on which a printed circuit board for current detection can be mounted, is formed by, for example, copper or tin plating and fixed by welding 12a in a standing manner on each of the two base materials <NUM>, as shown in <FIG>.

A process of manufacturing the thus arranged shunt resistor <NUM> will next be described specifically with reference to <FIG>.

First, as shown in <FIG>, two base materials <NUM> are prepared each with a bolt hole 11e formed closer to the other side surface 11d in a vertically penetrating manner. Further, a resistance element <NUM> is then prepared with such a first protruding portion 10a and a second protruding portion 10b as described above.

Next, the thus prepared two base materials <NUM> and the first protruding portion 10a and the second protruding portion 10b of the resistance element <NUM> are clamped by a well-known clamping mechanism not shown and, in this state, the side surfaces 11c of the two base materials <NUM> are brought into contact with the left and right side surfaces 10c, 10d of the resistance element <NUM> so that the resistance element <NUM> is sandwiched between the two base materials <NUM>, as shown in <FIG>.

Next, in this state, laser welding not shown is used under a non-vacuum environment to join the side surface 11c of the base material <NUM> on the left side in the drawing by welding 10e to the left side surface 10c of the resistance element <NUM>, while joining the side surface 11c of the base material <NUM> on the right side in the drawing by welding 10e to the right side surface 10d of the resistance element <NUM>, as shown in <FIG>. This causes the two base materials <NUM> and the resistance element <NUM> to be formed integrally by welding 10e.

Accordingly, the side surface 11c of the base material <NUM> on the left side in the drawing can thus be joined by welding 10e to the left side surface 10c of the resistance element <NUM>, while the side surface 11c of the base material <NUM> on the right side in the drawing can be joined by welding 10e to the right side surface 10d of the resistance element <NUM>, even when the resistance element <NUM> has a reduced width W1 (see <FIG> and <FIG>) of about <NUM>. That is, since the welding 10e only requires a welding bead width of as small as <NUM> to <NUM>, and even if the welding bead width for the welding 10e may be <NUM>, the resistance element <NUM> having a width W1 (see <FIG> and <FIG>) of about <NUM> can ensure a sufficient welding bead width. Accordingly, the side surface 11c of the base material <NUM> on the left side in the drawing can be joined by welding 10e to the left side surface 10c of the resistance element <NUM>, while the side surface 11c of the base material <NUM> on the right side in the drawing can be joined by welding 10e to the right side surface 10d of the resistance element <NUM>, even when the resistance element <NUM> has a reduced width W1 (see <FIG> and <FIG>) of about <NUM>. That is, this makes it possible to provide welding of high quality. As a result, poor joints are less likely to occur.

In this embodiment, the resistance element <NUM> is thus provided with the first protruding portion 10a and the second protruding portion 10b so as to be clamped by a well-known clamping mechanism not shown in order to ensure a sufficient welding bead width, even when the resistance element <NUM> has a reduced width W1 (see <FIG> and <FIG>) of about <NUM>. This allows the resistance element <NUM> to be clamped by a well-known clamping mechanism not shown while ensuring a sufficient welding bead width, even when the resistance element <NUM> has a reduced width W1 (see <FIG> and <FIG>) of about <NUM>, whereby this makes it possible to realize welding of high quality and poor joints are less likely to occur.

If the resistance element <NUM> had such a structure as that of the resistance element <NUM> shown in <FIG> and if the resistance element <NUM> has a reduced width W1 (see <FIG> and <FIG>) of about <NUM>, the well-known clamping mechanism used for clamping the resistance element <NUM> having such a structure as that of the resistance element <NUM> shown in <FIG> would become an impediment and it would be very difficult to ensure a welding bead width of about <NUM> to <NUM>. This makes it difficult to provide high-quality welding and poor joints are therefore likely to occur.

For this reason, in this embodiment, the resistance element <NUM> is provided with the first protruding portion 10a and the second protruding portion 10b for clamping by a well-known clamping mechanism not shown in order to ensure a sufficient welding bead width.

On the other hand, in the conventional continuous welding method, as shown in <FIG>, a long object LO with a resistance element <NUM> between two base materials <NUM> wound around a feed roll KR1 is fed from the feed roll KR1 in the direction indicated by the arrow Y11, and within the fed long object LO, portions in which the resistance element <NUM> is in close proximity to the two respective base materials <NUM> undergo welding 101a using an electron beam DE, which does not allow the resistance element <NUM> shown in <FIG> to have such a shape as that of the resistance element <NUM> described in this embodiment, which is provided with the first protruding portion 10a and the second protruding portion 10b.

For this reason, in this embodiment, unlike the conventional continuous welding method, two base materials <NUM> are prepared each with a bolt hole 11e formed closer to the other side surface 11d in a vertically penetrating manner, and further a resistance element <NUM> is prepared with such a first protruding portion 10a and a second protruding portion 10b as described above as shown in <FIG> and, in this state, the thus prepared two base materials <NUM> and the first protruding portion 10a and the second protruding portion 10b of the resistance element <NUM> are clamped by a well-known clamping mechanism not shown so that the two base materials <NUM> and the resistance element <NUM> therebetween are formed integrally by welding 10e.

Accordingly, this makes it possible to realize welding of high quality in which poor joints are less likely to occur even when the resistance element <NUM> has a reduced width.

After the welding as shown in <FIG> above, a measurement terminal <NUM> is fixed by welding 12a in a standing manner on each of the two base materials <NUM>, as shown in <FIG>, with which such a shunt resistor <NUM> as shown in <FIG> is manufactured.

Thus, in accordance with this embodiment having been described above, since the resistance element <NUM> is provided with the first protruding portion 10a that protrudes outward from the one longitudinal side surface 11a (upper surface in the drawing) of the two base materials <NUM> and the second protruding portion 10b that protrudes outward from the other longitudinal side surface 11b (lower surface in the drawing) of the two base materials <NUM>, the two base materials <NUM> and the first protruding portion 10a and the second protruding portion 10b of the resistance element <NUM> can be clamped by a well-known clamping mechanism not shown. This allows to form the two base materials <NUM> and the resistance element <NUM> therebetween integrally by welding 10e while ensuring a sufficient welding bead width, whereby this makes it possible to realize welding of high quality in which poor joints are less likely to occur.

This embodiment can thus achieve an accurate current value measurement even when a large current flows.

According to the invention, the first protruding portion 10a is formed so as to have a height (length) H1 (see <FIG>) of <NUM> to <NUM> and the second protruding portion 10b is also formed so as to have a height (length) H2 (see <FIG>) of <NUM> to <NUM>, and this is for the following reasons. That is, when the size of the resistance element <NUM> itself needs to be reduced to adjust the resistance value and if the first protruding portion 10a were formed so as to have a height (length) H1 (see <FIG>) of less than <NUM> and the second protruding portion 10b were also formed so as to have a height (length) H2 (see <FIG>) of less than <NUM>, it might be necessary to provide such a notched portion 101b as shown in <FIG> and therefore it might not be possible to measure the current value accurately. Also, when the shunt resistor <NUM> is installed on a current path through which a large current flows from a battery for high-voltage applications to a motor circuit that are used in, for example, electric vehicles (EVs), hybrid vehicles (HVs), and plug-in hybrid vehicles (PHVs) and if the first protruding portion 10a were formed so as to have a height (length) H1 (see <FIG>) of more than <NUM> and the second protruding portion 10b were also formed so as to have a height (length) H2 (see <FIG>) of more than <NUM>, the shunt resistor <NUM> might come into contact with other devices or parts and therefore it might not be possible to measure the current value accurately. It is therefore the invention to form the first protruding portion 10a so as to have a height (length) H1 (see <FIG>) of <NUM> to <NUM> and also the second protruding portion 10b to have a height (length) H2 (see <FIG>) of <NUM> to <NUM>. Accordingly, by forming the first protruding portion 10a to have a height (length) H1 (see <FIG>) of <NUM> to <NUM> and also the second protruding portion 10b so as to have a height (length) H2 (see <FIG>) of <NUM> to <NUM>, even if the need for reducing the size of the resistance element <NUM> itself to adjust the resistance value arises, the size of the resistance element <NUM> itself can be reduced to adjust the resistance value without providing such a notched portion 101b as shown in <FIG>, and further it is possible to avoid contact with other devices or parts. This configuration according to the invention can thus achieve an accurate current value measurement even when a large current flows.

Another embodiment describes an example in which laser welding not shown is used under a non-vacuum environment to join the side surface 11c of the base material <NUM> on the left side in the drawing by welding 10e to the left side surface 10c of the resistance element <NUM>, while joining the side surface 11c of the base material <NUM> on the right side in the drawing by welding 10e to the right side surface 10d of the resistance element <NUM>, as shown in <FIG>, but an electron beam may be used for welding.

However, welding using an electron beam requires performing welding under a vacuum environment. For such welding under a vacuum environment while clamping by using a clamping mechanism not shown as in this embodiment, it is very difficult to automate the welding operation. It is therefore preferable to use laser welding not shown for welding under a non-vacuum environment, because using laser welding not shown under a non-vacuum environment allows for easy automation of the welding operation. This can improve mass productivity.

Incidentally, the shape of the resistance element <NUM>, the base materials <NUM>, and the measurement terminals <NUM> described in this embodiment is merely an example, and various modifications and changes are possible without departing from the spirit and scope of the present invention as defined in the appended claims. For example, this embodiment describes an example of the resistance element <NUM> in which the first protruding portion 10a is provided on the upper side of the resistance element <NUM> and the second protruding portion 10b is provided on the lower side of the resistance element <NUM>, but without being limited thereto, only either one of the first protruding portion 10a and the second protruding portion 10b may be provided. This also allows the two base materials <NUM> and the first protruding portion 10a and the second protruding portion 10b of the resistance element <NUM> to be clamped by a well-known clamping mechanism not shown. It is however preferable to provide the first protruding portion 10a on the upper side of the resistance element <NUM> and provide the second protruding portion 10b on the lower side of the resistance element <NUM>, because this allows the resistance element <NUM> to be clamped stably by a well-known clamping mechanism not shown.

This embodiment also describes an example of the shape of the base material <NUM> in which the base materials <NUM> are each formed in a lengthened rectangular shape, but without being limited thereto, the present invention can also be applied to base materials <NUM> that have undergone a bending process, as shown in <FIG>. In particular, since the conventional continuous welding method cannot be employed to manufacture a shunt resistor <NUM> using such base materials <NUM> that have undergone a bending process, the manufacturing method according to this embodiment described with reference to <FIG> is of particular benefit.

Claim 1:
A shunt resistor having:
a resistance element (<NUM>); and
two base materials (<NUM>) joined by welding (10e) to the resistance element (<NUM>) with the resistance element (<NUM>) therebetween wherein
the resistance element (<NUM>) is provided with a protruding portion (10a) that protrudes from at least one (11a) of longitudinal side surfaces (11a, 11b) of the two base materials (<NUM>), characterized in that the protruding portion is formed so as to have a height (H1, H2) of <NUM> to <NUM>.