Heat sink, control device having the heat sink and machine tool provided with the device

A heat sink has a panel body and a heat radiating portion. The panel body includes a working fluid circuit for circulating a working fluid in the panel body and has a heat receiving portion and a heat radiating portion substantially on the same plane. The heat radiating portion has an upper region and a lower region. The heat receiving portion is provided on a lateral side of the lower region of the heat radiating portion, and a plurality of radiating fins are provided on at least one surface of the heat radiating portion of the panel body. The working fluid circuit extends from the heat receiving portion to the lower region of the heat radiating portion and further to the upper region of the heat radiating portion, and the working fluid circuit in the lower region of the heat radiating portion has an average channel cross sectional area which is smaller than an average channel cross sectional area of the working fluid circuit in the heat receiving portion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is an application filed under 35 U.S.C. 111(a) claiming the benefit pursuant to 35 U.S.C. 119(e)(1) of the filing date of Provisional Application No. 60/322,439 filed Sep. 17, 2001 pursuant to 35 U.S.C. 111(b).

TECHNICAL FIELD

The present invention relates to heat sinks, and more particularly to heat sinks of the heat pipe type suitable for cooling heat generating elements of control devices such as servoamplifiers for use in NC machine tools and like machine tools. The invention relates also to control devices equipped with the heat sink and machine tools provided with the device.

BACKGROUND ART

FIGS. 13 and 14show a heat sink of the type mentioned already known which comprises a main body102in the form of a vertical plate and having a heat receiving portion103for receiving the heat from a heat generating element and a heat radiating portion104integral with a lateral side of the heat receiving portion103and having an upper end projecting upward beyond the upper end of the heat receiving portion103, and radiator fins105provided on one or each of opposite surfaces of the heat radiating portion104. The heat sink main body102has a heat pipe portion106comprising a working fluid circuit161extending from the portion103to a lower region104aof the heat radiating portion at the lateral side of the portion103and further to an upper region104bof the heat radiating portion which region104bis positioned at a higher level than the heat receiving portion103, the circuit161having a working fluid (not shown) enclosed therein (see the publication of JP-A No. 8-186210).

The working fluid circuit161of the heat sink101described has, for example, a pattern as shown inFIG. 14and has substantially the same channel cross sectional area from portion to portion. The working fluid in a working fluid circuit portion161B provided in the heat receiving portion103evaporates to a gas by receiving the heat emitted by the heat generating element. The gaseous working fluid flows through part of a working fluid circuit portion161A provided in the heat radiating portion lower region104ainto a working fluid circuit portion161C in the heat radiating portion upper region104b, in which the fluid is subjected to heat exchange with air through the radiating fins105, whereby the fluid is converted to a liquid on condensation. The liquid of working fluid flows through other part of the circuit portion161A in the lower region104aunder gravity and returns to the circuit portion161B in the heat receiving portion103. In the case of the heat sink101described, however, the liquid of working fluid remains also in the circuit portion161A in the lower region104abecause of structural reasons.

Even when the circuit portion161A in the heat radiating portion lower region104apermits the liquid of working fluid to remain therein locally, the liquid retaining part contributes nothing to heat radiation and is therefore a structurally useless part. Additionally in order to maintain the liquid of working fluid at a predetermined level, there is a need to increase the amount of working fluid enclosed in the circuit by an amount corresponding to the quantity of the liquid working fluid remaining in the circuit portion161A.

Further since the radiator fins105are provided substantially over the entire area of one or each of opposite surfaces of the heat radiating portion104, fins105are present also in the lower region104a. Nevertheless, the fins105provided in the lower region104acontribute almost nothing to heat radiation and are structurally useless. The presence of useless fins conversely increases the pressure loss of the air flowing between the fins105, consequently leading to impaired heat radiation performance.

For use in cooling the heat generating elements, for example, of control devices of machine tools, an object of the present invention is to provide a heat sink of the heat pipe type which is free of problems such as the useless structural portion due to the stagnation of liquid working fluid that would occur in the working fluid circuit portion in the heat radiating portion lower region, an increase in the amount of working fluid enclosed in the circuit and an increased pressure loss of air and which exhibits high performance at a lower cost.

DISCLOSURE OF THE INVENTION

The present invention provides a first heat sink comprising a heat sink main body in the form of a vertical plate and having a heat receiving portion and a heat radiating portion integral with a lateral side of the heat receiving portion and having an upper end projecting upward beyond an upper end of the heat receiving portion, and radiating fins provided on at least one surface of the heat radiating portion, the heat sink main body having a heat pipe portion comprising a working fluid circuit extending from the heat receiving portion to a lower region of the heat radiating portion at the lateral side of the heat receiving portion and further to an upper region of the heat radiating portion which region is positioned at a higher level than the heat receiving portion, the working fluid circuit having a working fluid enclosed therein, the heat sink being characterized in that the portion of the working fluid circuit provided in the lower region of the heat radiating portion is smaller than the portion of the working fluid circuit provided in the heat receiving portion in average channel cross sectional area.

Thus, the circuit portion provided in the lower region is smaller than the circuit portion provided in the heat receiving portion in average channel cross sectional area. The amount of the working fluid in a liquid state and remaining in the former circuit portion is then smaller than in the prior art. This diminishes the structurally useless portion of the sink, consequently serving to reduce the amount of working fluid to be enclosed in the circuit.

In the first heat sink of the invention, the circuit portion provided in the lower region of the heat radiating portion may have a bottom positioned at a higher level than a bottom of the circuit portion provided in the heat receiving portion.

When the bottom of the circuit portion in the lower region is thus positioned at a higher level than the bottom of the circuit portion of the heat receiving portion, the working fluid in the liquid state and remaining in the former circuit portion further diminishes, with the result that the advantage described above is available more effectively.

In the first heat sink, the circuit portion provided in the lower region of the heat radiating portion may have a bottom sloping downward toward the heat receiving portion.

When the bottom of the circuit portion in the lower region thus slopes downward toward the heat receiving portion, the amount of liquid working fluid remaining in the circuit portion becomes further smaller, whereby the above advantages becomes greater. This further enables the liquid working fluid to flow from the circuit portion in the lower region to the circuit portion in the heat receiving portion more rapidly.

The present invention provides a second heat sink comprising a heat sink main body in the form of a vertical plate and having a heat receiving portion and a heat radiating portion integral with a lateral side of the heat receiving portion and having an upper end projecting upward beyond an upper end of the heat receiving portion, and radiating fins provided on at least one surface of the heat radiating portion, the heat sink main body having a heat pipe portion comprising a working fluid circuit extending from the heat receiving portion to a lower region of the heat radiating portion at the lateral side of the heat receiving portion and further to an upper region of the heat radiating portion which region is positioned at a higher level than the heat receiving portion, the working fluid circuit having a working fluid enclosed therein, the heat sink being characterized in that the radiating fins each have a lower end positioned at a higher level than a lower end of the lower region of the heat radiating portion and at the same level as or a lower level than an upper end of the lower region.

When the lower ends of the radiating fins are thus positioned at a level higher than the lower end of the lower region and at the same level as or a lower level than the upper end of the lower region, no radiating fins will be present at at least a lower part in the lower region having the circuit portion not contributing to heat radiation. This diminishes the structurally useless portion to result in a reduced cost, also contributing to a reduction in the weight of the heat sink. The pressure loss of the air flowing between the radiating fins can further be reduced to thereby achieve improved heat radiation performance. With a reduction in the air pressure loss, the fin pitch of radiating fins can be smaller than in the prior art to thereby achieve a further improvement in heat radiation performance.

The present invention further provides a third heat sink comprising a heat sink main body in the form of a vertical plate and having a heat receiving portion and a heat radiating portion integral with a lateral side of the heat receiving portion and having an upper end projecting upward beyond an upper end of the heat receiving portion, and radiating fins provided on at least one surface of the heat radiating portion, the heat sink main body having a heat pipe portion comprising a working fluid circuit extending from the heat receiving portion to a lower region of the heat radiating portion at the lateral side of the heat receiving portion and further to an upper region of the heat radiating portion which region is positioned at a higher level than the heat receiving portion, the working fluid circuit having a working fluid enclosed therein, the heat sink being characterized in that the fin pitch of the radiating fins in the lower region of the heat radiating portion is greater than the fin pitch of the radiating fins in the upper region thereof.

The fin pitch of the radiating fins in the lower region is thus made greater than the fin pitch of the radiating fins in the upper region. This reduces the heat radiating area of the radiating fins present in the lower region having the circuit portion not contributing to heat radiation, consequently diminishing the structurally useless portion to result in a reduced cost and also contributing to a reduction in the weight of the heat sink. The pressure loss of the air flowing between the radiating fins can further be reduced to thereby achieve improved heat radiation performance.

In the third heat sink of the invention, the height of the radiating fins in the lower region of the heat radiating portion may be lower than the height of the radiating fins in the upper region thereof.

In addition to the above fin pitch, the height of the radiating fins in the lower region is made lower than the height of the radiating fins in the upper region. This further reduces the heat radiating area of the radiating fins present in the lower region having the circuit portion not contributing to heat radiation. The advantage described therefore becomes greater.

The present invention further provides a fourth heat sink comprising a heat sink main body in the form of a vertical plate and having a heat receiving portion and a heat radiating portion integral with a lateral side of the heat receiving portion and having an upper end projecting upward beyond an upper end of the heat receiving portion, and radiating fins provided on at least one surface of the heat radiating portion, the heat sink main body having a heat pipe portion comprising a working fluid circuit extending from the heat receiving portion to a lower region of the heat radiating portion at the lateral side of the heat receiving portion and further to an upper region of the heat radiating portion which region is positioned at a higher level than the heat receiving portion, the working fluid circuit having a working fluid enclosed therein, the heat sink being characterized in that the height of the radiating fins in the lower region of the heat radiating portion is lower than the height of the radiating fins in the upper region thereof.

If the height of the radiating fins in the lower region is thus made lower than the height of the radiating fins in the upper region, a further reduction can be made in the heat radiating area of the radiating fins present in the lower region having the circuit portion not contributing to heat radiation, consequently diminishing the structurally useless portion to result in a reduced cost and also contributing to a reduction in the weight of the heat sink. The pressure loss of the air flowing between the radiating fins can further be reduced to thereby achieve improved heat radiation performance.

In the first to fourth heat sinks of the invention, the heat sink main body may be provided by a roll-bonded panel, with the working fluid circuit comprising a tubular protuberant portion so formed as to bulge out toward at least one side of the panel. Alternatively the heat sink main body may comprise a clad sheet formed by joining two metal sheets to each other, and a circuit forming recess may be formed in at least one of the metal sheets in a surface thereof to be joined to the other metal sheet. However, the construction of the heat sink main body is not limited to those described above.

In the first to fourth heat sinks of the invention, a fin unit made of a metal extrudate comprises a flat platelike base joined to at least one surface of the heat radiating portion, and a plurality of fin portions formed on an outer surface of the base integrally with the base, the fin portions providing the radiating fins. Alternatively, the radiating fins are provided by a corrugated fin member joined to at least one surface of the heat radiating portion directly or with a flat platelike base interposed therebetween. However, the radiating fins are not limited to those described above in construction.

The present invention includes a control device having one of the heat sinks described above and characterized in that the device comprises a heat generating element, the heat sink being attached to the device so as to receive by the heat receiving portion thereof the heat produced by the heat generating element. The control device is, for example, a servoamplifier provided, for example, with a thyristor, transistor or like heat generating element.

The present invention further includes a machine tool characterized in that the tool comprises the control device of the invention. The machine tool is, for example, an NC machine tool.

BEST MODE OF CARRYING OUT THE INVENTION

FIGS. 1 to 4show a first embodiment of the invention. With reference toFIGS. 1 to 3, a heat sink1of the invention comprises a heat sink main body2in the form of a vertical plate and having a heat receiving portion3and a heat radiating portion4integral with a lateral side of the heat receiving portion3and having an upper end projecting upward beyond the upper end of the portion3, and radiating fins5provided on each of opposite surfaces of the heat radiating portion4. The heat sink main body2has a heat pipe portion6which is formed by providing a working fluid circuit61extending from the heat receiving portion3to a lower region4aof the heat radiating portion at the lateral side of the heat receiving portion3and further to an upper region4bof the heat radiating portion which region4bis positioned at a higher level than the heat receiving portion3and enclosing a working fluid (not shown) in the circuit61. The portion61A of the working fluid circuit provided in the lower region4aof the heat radiating portion is smaller than the portion61B of the circuit provided in the heat receiving portion3in average channel cross sectional area. The heat sink main body2is provided by a roll-bonded panel20. The working fluid circuit61comprises a tubular protuberant portion610so formed as to bulge out toward opposite sides of the panel20. Each of two fin units50is made of an aluminum (including an aluminum alloy, the same as hereinafter) extrudate and comprises a flat platelike base501, and a plurality of fin portions502formed on the outer surface of the base501integrally therewith. The bases501of the two units50are joined respectively to the opposite surfaces of the heat radiating portion3. The fin portions502provide the radiating fins5.

As shown inFIG. 3, the heat sink main body2has an L-shape as laterally reversed. The square portion projecting leftward inFIG. 3serves as the heat receiving portion3, and the remaining vertically elongated rectangular portion as the heat radiating portion4. The working fluid circuit61is provided approximately over the entire area of the heat sink main body2and has a lattice pattern as shown inFIG. 3. The circuit61is generally hexagonal in channel cross section as seen inFIG. 2. The portions of the main body2bulging out toward the opposite sides each have a flat face610A to be joined to the base501of the fin unit50. The circuit portion61A in the heat radiating portion lower region4ais provided approximately at the same level as the circuit portion61B in the heat receiving portion3. Accordingly, the working fluid in the form of a liquid and in circulation remains in this portion61A during the operation of the heat pipe portion6. The liquid working fluid in the circuit portion61A in the lower region4aflows in the largest amount through a vertical channel611positioned at the right end inFIG. 3and through a horizontal channel612at the lowermost level, and in the second largest amount through a vertical channel613at the left of the vertical channel611adjacent thereto and through a horizontal channel614above the horizontal channel612. A gas of working fluid flowing from the circuit portion61B of the heat receiving portion3toward the circuit portion61C in the heat radiating portion upper region4bmainly flows through a curved channel615positioned at the left upper portion of the lower region4a. Almost no liquid working fluid flows through the curved channel615. The two vertical channels611,613and the two horizontal channels612,614which serve substantially as circulation channels for the liquid working fluid are made smaller than the channels constituting the circuit portion61B of the heat receiving portion3in cross sectional area as shown inFIG. 3, with the result that the circuit portion61A in the heat radiating portion lower region4ais smaller than the circuit portion61B of the heat receiving portion3in average channel cross sectional area.

The base501of the fin unit50has approximately the same size as the heat radiating portion4of the heat sink main body2. The fin portions502are each in the form of a plate projecting from the outer surface of the base501perpendicular thereto and extending vertically. The fin portions502are arranged in parallel widthwise of the base501at a predetermined spacing. The base501of the fin unit50is joined to the heat radiating portion4of the heat sink main body2usually by brazing.

FIG. 4shows the heat sink1as attached to a servoamplifier8of an NC machine tool7. The servoamplifier8internally has a thyristor or like heat generating element81and is disposed within a casing71of the NC machine tool7. The heat sink1is attached to the servoamplifier8so that the heat receiving portion3of the main body2can receive the heat emitted by the heat generating element81. The heat radiating portion4of the heat sink main body2and the radiating fins5are positioned outside the servoamplifier8. The radiating fins5are exposed to an air stream from a fan9disposed therebelow.

A large quantity of heat emitted by the heat generating element81with the operation of the servoamplifier8is transmitted to the heat receiving portion3of the heat sink main body2. The liquid working fluid in the circuit portion61B provided in the heat receiving portion3is evaporated into a gas with the heat. The gas of working fluid flows through part of the circuit portion61A provided in the heat radiating portion lower region4ato the circuit portion61C provided in the heat radiating portion upper region4band is subjected to heat exchange with air in the portion61C through the radiating fins5, whereby the gas is converted to a liquid on condensation. The liquid of working fluid flows down under gravity, remains in other part of the circuit portion61A in the lower region4aand is thereafter returned to the circuit portion61B of the heat receiving portion3.

In the case of the heat sink1according to the invention, the circuit portion61A in the lower region4ais smaller than the circuit portion61B of the heat receiving portion3in average channel cross sectional area as described above, so that the amount of the liquid working fluid remaining in the former circuit portion61A is smaller than in the prior art shown inFIGS. 13 and 14. Accordingly, the heat sink1is diminished in structural useless portion, consequently reducing the amount of working fluid to be enclosed in the circuit61.

FIG. 5shows a second embodiment of the invention, i.e., a heat sink11, wherein the portion61A of the working fluid circuit provided in the heat radiating portion lower region4ahas a bottom616positioned at a higher level than the bottom617of the portion61B of the working fluid provided in the heat receiving portion3as shown inFIG. 5. With this heat sink11, the amount of liquid working fluid remaining in the former circuit portion61A can be further smaller, so that the advantage described with reference to the first embodiment is available more effectively.

FIG. 6shows a third embodiment of the invention, i.e., a heat sink12, wherein the working fluid circuit portion61A provided in the heat radiating portion lower region4ahas a bottom618sloping downward toward the heat receiving portion3as shown inFIG. 6. With this heat sink12, the amount of liquid working fluid remaining in the former circuit portion61A can be further smaller, so that the advantage described with reference to the first embodiment is available more effectively. Further in the case of this heat sink12, the liquid of working fluid returns from the circuit portion61A in the lower region4ato the circuit portion61B of the heat receiving portion3more rapidly.

FIGS. 7 to 9show a fourth embodiment of the invention. These drawings show a heat sink13, which comprises a heat sink main body2in the form of a vertical plate and having a heat receiving portion3and a heat radiating portion4integral with a lateral side of the heat receiving portion3and having an upper end projecting upward beyond the upper end of the portion3, and radiating fins5A provided on each of opposite surfaces of the heat radiating portion4. The heat sink main body2has a heat pipe portion6which is formed by providing a working fluid circuit61extending from the heat receiving portion3to a lower region4aof the heat radiating portion at the lateral side of the heat receiving portion3and further to an upper region4bof the heat radiating portion which region4bis positioned at a higher level than the heat receiving portion3and enclosing a working fluid (not shown) in the circuit61. As shown inFIG. 9, the radiating fins5A each have a lower end500positioned at a higher level than the lower end401of the radiating portion lower region4aand at a lower level than the upper end402of the region4a.

The heat sink main body2has basically the same construction as the main body2of the heat sink1shown inFIGS. 1 to 3, while the working fluid circuit61is substantially the same as the circuit of the conventional heat sink shown inFIGS. 13 and 14(seeFIG. 9). The circuit61of the present embodiment can be of the same construction as the circuit61of the heat sink1,11or12shown inFIGS. 1 to 3,5or6.

The radiating fins5A is provided by a corrugated fin member502A joined to the surface of the heat radiating portion4of the main body2with a flat platelike base member501A interposed therebetween. The base member501A is joined to the radiating portion4of the main body2, and the fin member502A to the base member501A, usually by brazing. The base member501A is provided, for example, by a brazing sheet comprising an aluminum sheet clad with a brazing material on each surface thereof. The fin member502A is provided, for example, by an aluminum sheet corrugated by roll forming. The corrugated fin member502A has its furrow portions joined to the outer surface of the base member501A, with the ridges and furrows thereof arranged alternately in a horizontal direction.

The heat sink13, like the one shown inFIG. 4, is attached, for example, to a servoamplifier of an NC machine tool and used for cooling a thyristor or like heat generating element in the servoamplifier.

In the case of the heat sink13of the present embodiment, the lower ends500of the radiating fins5A are positioned at a higher level than the lower end401of the lower region4aand a lower level than the upper end402of the region4a, so that the sink is diminished in structural useless portion and available at a reduced cost unlike the conventional one shown inFIGS. 13 and 14. The construction also contributes to a reduction in weight and decreases the pressure loss of the air flowing between the radiating fins5A. With the air pressure loss reduced, the pitch P of radiating fins5A can be smaller than in the prior art. This also achieves a further improvement in heat radiation performance.

FIGS. 10 to 12show a fifth embodiment of the invention. These drawings show a heat sink14which comprises a heat sink main body2A in the form of a vertical plate and having a heat receiving portion3and a heat radiating portion4integral with a lateral side of the heat receiving portion3and having an upper end projecting upward beyond the upper end of the portion3, and radiating fins5B provided on one surface of the heat radiating portion4. The heat sink main body2A has a heat pipe portion6which is formed by providing a working fluid circuit61extending from the heat receiving portion3to a lower region4aof the heat radiating portion at the lateral side of the heat receiving portion3and further to an upper region4bof the heat radiating portion which region4bis positioned at a higher level than the heat receiving portion3and enclosing a working fluid (not shown) in the circuit61. As shown inFIG. 10, the fin pitch P1of the radiating fins5B in the lower region4aof the heat radiating portion is greater than the fin pitch P2of the radiating fins5B in the upper region4bthereof. The height H1of the radiating fins5B in the lower region4aof the heat radiating portion is lower than the height H2of the radiating fins5B in the upper region4bthereof.

As shown inFIG. 11, the heat sink main body2A comprises a clad sheet21formed by joining two metal sheets211,212to each other, and circuit forming recesses610B are formed in one of the metal sheets,211, in the surface thereof to be joined to the other metal sheet. The metal sheets211,212each comprise, for example, an aluminum sheet. The recesses610B are formed in one of the aluminum sheets as by press work. The two metal plates211,212are joined to each other, for example, by brazing or welding. The working fluid circuit61of the heat sink main body2A is substantially the same as the circuit of the conventional heat sink shown inFIGS. 13 and 14(seeFIG. 12). The circuit61of the present embodiment can be of the same construction as the circuit61of the heat sink1,11or12shown inFIGS. 1 to 3,5or6. The channels of the fluid circuit61are generally trapezoidal in cross section as shown inFIG. 11. The bottoms of the circuit forming recesses in the metal plate211have flat surfaces610A for joining a base member501A thereto. The heat sink main body can be provided by a clad sheet comprising at least three metal sheets which are joined. In this case, circuit forming cutouts are formed in the intermediate metal sheet, and inner fin members for forming a working fluid circuit are provided in the respective cutouts to form the circuit in the heat sink main body.

The radiating fins5B are provided by upper and lower two corrugated fin members502B,502C joined to one surface of the heat radiating portion4of the main body2A, with a flat platelike base member501A interposed therebetween. The base member501A is joined to the radiating portion4of the main body2A, and the fin members502B,502C to the base member501A, usually by brazing. The base member501A is provided, for example, by a brazing sheet comprising an aluminum sheet clad with a brazing material on each surface thereof, and has approximately the same size as the heat radiating portion4of the main body2A. The fin members502B,502C are each provided, for example, by an aluminum sheet corrugated by roll forming. Each of the fin members502B,502C has its furrow portions joined to the outer surface of the base member501A, with the ridges and furrows thereof arranged alternately in a horizontal direction. The lower fin member502B is joined to the outer surface of the base member501A over the portion thereof corresponding to the heat radiating portion lower region4a, and the upper fin member502C to the base member portion corresponding to the upper region4b. The fin pitch P1of the lower fin member502B is greater than the fin pitch P2of the upper fin member502C. The fin height H1of the lower fin member502B is lower than the fin height H2of the upper fin member502C.

The heat sink14, like the one shown inFIG. 4, is attached, for example, to a servoamplifier of an NC machine tool and used for cooling a thyristor or like heat generating element in the servoamplifier.

In the case of the heat sink14of the present embodiment, the fin pitch P1of the radiating fins5B in the lower region4aof the heat radiating portion is greater than the fin pitch P2of the radiating fins5B in the upper region4bthereof. The height H1of the radiating fins5B in the lower region4aof the heat radiating portion is lower than the height H2of the radiating fins5B in the upper region4bthereof as described above. Unlike the heat sink of the prior art shown inFIGS. 13 and 14, therefore, the heat sink14is diminished in structural useless portion and available at a reduced cost, and the construction contributes to a reduction in weight. Further it is possible to decrease the pressure loss of the air flowing between the radiating fins5B. This also achieves a further improvement in heat radiation performance.

The foregoing embodiments are given for illustrative purposes only. The invention can of course be practiced as suitably modified without departing from the scope of the invention set forth in the appended claims.