DESCRIPTION A mist generator TECHNICAL FIELD The present invention relates to a mist generator. 5 BACKGROUND ART Heretofore, a variety of mist generators (the term "mist generator" used herein to represent a concept including steam generators, as well) have been proposed 10 which are used for heating home bathrooms and shower rooms or used for simple steam baths. These mist generators generally require dedicated heat sources, such as electric heaters, and hence are costly. In addition, the mist generators also require 15 pipework and wiring, thus being less practicable when installed in already built houses. To overcome this problem, the present inventors have proposed a mist generator which is adapted to diffuse hot water fed from an already installed hot water supply 20 unit by means of a rotating impeller, thereby generating mist or steam in a simple and efficient manner (see Japanese Unexamined Patent Publication No.6(1996)-277261). This mist generator is adapted for volume production 25 ofmist (the term"mist" usedhereintorepresentaconcept 1 including steam as well as a mixture of mist and steam) by way of a simple construction. Unfortunately, there is a limit to an attempt to further simplify the construction because the impeller as well as a support 5 shaft and bearing for supporting the impeller are essential. on the other hand, a span of time is required for raising the temperature in the bathroom or the like. This has produced a demand for a mist generator capable of generating mist even more efficiently. 10 In view of the foregoing, the present invention has been accomplished with an object of providing a mist generator featuring an even more simple construction for efficient mist formation. 15 DISCLOSURE OF THE INVENTION For achieving the above object, a mist generator according to the invention comprises a nozzle for jetting a liquid, and a break-up member disposed opposite to the nozzle and including a plurality of pores permitting 20 the passage of a liquid jet from the nozzle for mist formation. In the mist generator thus arranged, the liquid is jetted from the nozzle against the break-up member so as to penetrate the pores thereof whereby the liquid jet 25 is broken down into mist particles. This negates the 2 need for the conventionally essential rotating member such as the impeller, permitting quite a simple construction to achieve an efficient mist formation. In one preferred embodiment, the inventive mist 5 generator is preferably arranged such that the break-up member is brought into vibration by the liquid jet from the nozzle. According to this embodiment, the liquid jet from the nozzle can be more efficiently broken down into fine particles due to the vibration of the break-up 10 member. Thus, the mist formation efficiency can be enhanced even higher. The above mist generator may include a diffuser member which is disposed between the break-up member and the nozzle for diffusing the liquid jet from the nozzle. 15 According to this embodiment, the liquid jet from the nozzle can be diffused by the diffuser member before impinging on the break-up member. Accordingly, the liquid jet from the nozzle can be sufficiently diffused for efficient break-up into fine particles even if the 20 nozzle is spaced only a short distance away from the break-up member and hence the liquid jet from the nozzle is not sufficiently diffused. As a result, the mist generator may be reduced in size. The above mist generator may further include a 25 collision plate with which the mist particles through 3 the break-up member are collided so as to be broken down into even more fine particles. According to this embodiment, the liquid particles so broken up by the break-up member are allowed to collide with the collision 5 plate, thus broken down into even more fine particles. Therefore, mist can be formed more efficiently. The break-up member may preferably comprise a net. According to this embodiment, a more simplified construction can efficiently form mist from the liquid. 10 The above net may preferably have a mesh size in the range of 0.05 to 2.0mm. According to this embodiment, the liquid jet from the nozzle can be more efficiently formed into mist. The above break-up member may be retained as allowed 15 to be vibrated by the liquid jet from the nozzle. According to this embodiment, the liquid jet from the nozzle can be even more efficiently broken down into fine particles by virtue of thevibrationof the break-up member. Thus, the mist formation efficiency can be enhanced even 20 higher. BRIEF DESCRIPTION OF THE DRAWINGS Fig.1 is a vertical sectional view showing a mist generator according to a first embodiment of the 25 invention; 4 Fig.2 is a sectional view taken on the line II-II in the above figure; Fig.3 is a vertical sectional view showing a mist generator according to a second embodiment of the 5 invention; Fig.4 is a sectional view taken on the line IV-IV in the above figure; Fig.5 is a vertical sectional view showing a mist generator according to a third embodiment of the 10 invention; and Fig.6 is a vertical sectional view showing a mist generator according to a fourth embodiment of the invention. 15 BEST MODES FOR CARRYING OUT THE INVENTION Next, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. Fig.1 is a vertical sectional view showing a mist 20 generator according to a first embodiment of the invention. Fig.2 is a sectional view taken on the line II-II in the above figure. The mist generator includes a cylindrical housing 1, which has a nozzle 2 inserted through one end thereof 25 and which is provided with a break-up member 3 at the 5 other end thereof. The mist generator is designed to form mist by breaking down hot water into mist particles, thereby permitting a bathroom or the like to be used as a simple steam bath. 5 The nozzle 2 is connected to a hot-water tap via a hose H with a joint J so that hot water fed from the tap can be jetted through its jet orifice 2a against the break-up member 3. The jet orifice 2a has a diameter D1 which is decreased a predetermined amount relative 10 to a diameter D2 of a nozzle body 2b in order to ensure an adequate jetting velocity of the hot water. In a case where, for example, the nozzle body 2b has a diameter D2 of 6 to 8mm, the diameter D1 of the jet orifice 2a is set in the range of 0.5 to 3mm. The diameter D1 of 15 the jet orifice 2a is suitably selected taking into consideration the size of pore 3a of the break-up member 3 to be described hereinlater, the volume and particle size of mist to be generated, and the distance between the nozzle 2 and the break-up member 3. 20 The break-up member 3 is attached to the housing 1 by means of a bolt B in a manner to cover the whole opening at the other end of the housing 1. The break-up member 3 consists of a net formed from a synthetic resin material, multiple meshes of which define pores 3a 25 permitting a liquid jet from the nozzle 2 to pass 6 therethrough for mist formation. The mesh size of the pore 3a is suitably selected taking into consideration the volume and particle size of mist to be generated. For efficient mist formation from hot water, it is 5 preferred to set the mesh size in the range of 0.05 to 2.0mm. The break-up member 3 is adapted to be elastically deformed in an axial direction of the nozzle 2 by a hot-water jet from the nozzle 2 impinging thereon, thus 10 being capable of finely vibrating in the axial direction. In the mist generator thus arranged, the hot-water jet from the nozzle 2 is allowed to impinge on the break-up member 3 and to pass through the pores 3a thereof, thereby being efficiently broken down into mist particles. Such 15 a mist formation brings about an efficient steam generation. Particularly, the above embodiment permits the break-up member 3 to be brought into fine vibration by the hot water impinging thereon such that the impinging hot water is continuously changed in direction to be 20 scattered. Thus, the hot water may be more efficiently broken down into fine particles. Therefore, an efficient mist formation in high volume can be accomplished. This embodiment presents a greater mist formation efficiency than the conventional mist generator employing the 25 impeller. In addition, this embodiment may have a highly 7 simplified construction because the rotary parts, such as the impeller, are not required. The greater the distance over which the hot-water jet from the nozzle 2 travels to reach the break-up member 5 3, the higher is the efficiency at which mist is formed. However, the distance can be reduced by decreasing the diameter Dl of the jet orifice 2a of the nozzle 2 for an increased jet pressure. For instance, where the hot water is supplied to the nozzle 2 at a pressure of 1 kg/cm 2 10 and the jet orifice 2a of the nozzle 2 has a diameter Dl of 1mm, the distance between the nozzle 2 and the break-up member 3 is set in the range of 10 to 50mm. Where the jet orifice 2a of the nozzle 2 has a diameter Dl of 2mm, the distance between the nozzle 2 and the break-up 15 member 3 is set in the range of 100 to 300mm. Fig.3 is a vertical sectional view showing a mist generator according to a second embodiment of the invention. Fig.4 is a sectional view taken on the line IV-IV in the above figure. 20 This embodiment differs from that of Fig.1 in that a diffuser member 4 is disposed between the nozzle 2 and the break-up member 3, the diffuser member serving to diffuse the hot-water jet from the nozzle 2. The diffuser member 4 is formed from a metal or 25 synthetic resin material in a conical shape. The 8 diffuser member is coaxially attached to the break-up member 3 at its great diameter end. The diffuser member 4 has its point angle 0 set in the range of 100 to 300 such that the resistance of the point may not lower the 5 velocity of the hot-water jet from the nozzle 2. The dimension of the great diameter end of the dif fuser member 4 is set in the range of about 1/4 to 1/2 with respect to the outside diameter of the break-up member 3. According to this embodiment, the hot-water jet from 10 the nozzle 2 can be diffused by the diffuser member 4 before impinging on the break-up member 3. Therefore, the hot-water jet from the nozzle 2 can be sufficiently diffused when impinging on the break-up member 2 even if the nozzle 2 is spaced a short distance away from the 15 break-up member 3 or a sufficient distance for diffusion of the hot-water jet from the nozzle 2 cannot be ensured. This provides for not only the reduction of distance between the nozzle 2 and the break-up member 3 or the size reduction of the mist generator but also the efficient 20 break-up of hot water into fine particles. Fig.5 is a vertical sectional view showing a mist generator according to a third embodiment of the invention. This embodiment is arranged such that the diffuser 25 member 4 is disposed between the nozzle 2 and the break-up 9 member 3 while a collision plate 5 is disposed on a back side of the break-up member 3 (left-hand side as seen in the figure) so as to be in collision with the mist particles through the break-up member 3 for further 5 breaking down the mist particles. The collision plate 5 is of a disk-like shape and fixed to an extension la of the housing 1 at an outer periphery thereof. The extension la of the housing 1 is provided with through holes lb for discharging the mist particles out of the 10 housing 1, the through holes lb arranged circumferentially of the extension at given space intervals. According to this embodiment, the liquid broken up by the break-up member 3 may be broken down into even 15 finer particles through collision with the collision plate 5. This results in an even more efficient mist formation. The collision plate 5 also serves to prevent relatively large droplets from being ejected out of the housing 1. 20 Of course, the collision plate 5 is also applicable to the embodiment shown in Fig.1. Further, the collision plate 5 may also be formed integrally with the housing 1 in one piece. Fig.6 is a vertical sectional view showing a mist 25 generator according to a fourth embodiment of the 10 invention. This embodiment is arranged such that the break-up member 3 is attached to the housing 1 in an axially movable relation with the bolt B mounting the member 3 to the 5 housingwhile a helical compression spring 6 is interposed between a head of the bolt B and the break-up member 3. The helical compression spring 6 is fitted about an outer periphery of the bolt B, resiliently urging the break-up member 3 toward the nozzle 2 at all times. An urging 10 force of the helical compression spring 6 is set to a degree that the break-up member 3 is brought into an axial fine vibration by the collision of the hot-water jet from the nozzle 2. According to this embodiment, upon impinging on the 15 break-up member 3, the hot-water jet from the nozzle 2 brings the net, constituting the break-up member, into fine vibration as well as the whole body of the break-up member 3 into fine vibration. Thus, the vibration of the break-up member 3 is promoted. This leads to an even 20 more efficient break-up of the hot water into fine particles and hence, anevenmoreefficientmist formation in high volume can be accomplished. In this embodiment, if a bolt through hole 3c formed in the break-up member 3 has a sufficiently greater inside 25 diameter than an outside dimension of the bolt B, the 11