Solenoid valve for a coolant circuit

Patent Abstract
A solenoid valve for a coolant circuit including a valve body having at least one inlet and at least one outlet for the coolant. A valve member is displaceable in the interior of the valve body between two switching positions for the solenoid valve. At least one outlet is formed by a capillary tube.

2. The solenoid valve according to claim 1, characterised in that the dimensions of the capillary tube (5) are selected so that when coolant passes through the solenoid valve, the pressure drop between the beginning and end of the capillary tube (5) is a multiple of the pressure drop between the inlet (7) of the solenoid valve and the beginning of the capillary (5).

3. The solenoid valve as claimed according to one of the preceding claims, characterised in that it has two outlets (4) each formed by a capillary tube (5).

4. The solenoid valve according to one of the preceding claims characterised in that each outlet (4) is arranged at a longitudinal end of the valve body (1) and the inlet (7) is arranged centrally on the valve body (1), and that it comprises a coil (17) for generating a magnetic field in the longitudinal direction in the valve body (1).

5. The solenoid valve according to claim 4 characterised in that the valve body (1) is arranged outside the core of the coil (17) and that the coil (17) has two pole pieces (23) in contact with the valve body for coupling in a magnetic field parallel to the longitudinal axis of the valve body (1).

6. The solenoid valve according to one of the preceding claims characterised in that the inlet (7) is formed by an outlet pipe section (6) of a coolant drier (9) joined to the valve body (1).

7. The solenoid valve according to one of the preceding claims characterised in that the end of each capillary tube (5) opens into an evaporator.

Patent Description
[0001] The present invention relates to a solenoid valve for a coolant circuit, with a valve body that has an inlet and at least one outlet for the coolant, and a valve member that can be displaced in the interior of the valve body between two positions that respectively correspond to the different switching positions of the solenoid valve.

[0002] Such a solenoid valve is used to control the coolant flow in the coolant circuit or, in cases where the solenoid valve is designed as a directional path valve with several outlets, to switch a coolant flow to one or the other of at least two evaporators of the coolant circuit.

[0003] A solenoid valve of the type described above is known from DE 37 18 94 A1.

[0004] The object of the invention is to provide a solenoid valve of the type specified above that allows simpler, faster and therefore more economically-priced construction of a coolant circuit compared with solenoid valves known so far.

[0005] The object is solved by a solenoid valve with the features of claim 1. Since the at least one outlet of the solenoid valve according to the invention is formed by a capillary tube, the solenoid valve can at the same time fulfil the task of a pressure-relieving element for the coolant which is supplied at high pressure. This reduces the number of parts which must be joined together during the manufacture of a coolant circuit and the number of connection points between them. This results in savings in production time and costs without the need to accept cutbacks in the quality of the coolant circuit. On the contrary, the reduced number of joints reduces the risk of leakages in the coolant circuit.

[0006] So that the capillary tube forming the outlet of the solenoid valve can also fulfil the task of a press-relieving element for the coolant under high pressure, it is desirable that the pressure drop between the beginning and end of the capillary tube is a multiple of the pressure drop between the inlet of the solenoid valve and the beginning of the capillary tube. In other words, the pressure drop at the valve seat of the solenoid valve is largely negligible compared with that in the capillary tube.

[0007] The solenoid valve preferably has two outlets which are each formed by a capillary tube. Such a solenoid valve allows the selective operation of two connected evaporators, e.g. a cooling area and a freezing area of a combined refrigerating device.

[0008] Each outlet is more appropriately arranged at a longitudinal end of a valve body and the inlet is arranged centrally on the valve body, and a coil is provided for generating a magnetic field in the longitudinal direction of the valve body. This allows the valve member to be simply controlled with the aid of a single magnetic field by means of linear forward and backward movement.

[0009] In order to supply the magnetic field in the valve body, the valve body is preferably arranged outside the interior of the coil and the coil has two pole pieces in contact with the valve body. With such an arrangement it is also possible to repair or change the coil after the coolant circuit has been fully installed without the need to break the coolant circuit for this purpose.

[0010] A further simplification of the structure of the coolant circuit and reduction in the number of parts is obtained if the inlet of the solenoid valve is formed by an outlet pipe section of a coolant drier joined to the valve body, which is usually provided in the coolant circuit of a refrigerating device.

[0011] Further features and advantages of the invention are obtained from the following description of an embodiment with reference to the drawings, wherein:

[0012] FIGS. 1 and 2 show two views of a valve body of a solenoid valve according to the invention;

[0013] FIGS. 3 and 4 show two views of a housing of the solenoid valve according to the invention with the coil installed therein in the perspective respectively corresponding to those in FIG. 1 or 2;

[0014] FIG. 5 is a view of the solenoid valve after joining together in a perspective corresponding to that in FIG. 1 and FIG. 3; and

[0015] FIG. 6 is a top view of the solenoid valve from FIG. 5.

[0016] FIGS. 1 and 2 show the valve body 1 of the solenoid valve according to the invention in two views from mutually perpendicular directions. The valve body 1 is shown in a partly cutaway view in FIG. 2 in order to explain its mode of operation better. A chamber 2 in the interior of the valve body 1 is bounded at two ends by valve seats 3 each having a central hole which forms the outlet 4 of the valve. The tube of the valve body 1 is tapered towards its two ends and capillary tubes 5 are tightly soldered into the end openings of the valve body 1. The capillary tubes 5 are provided to be each connected to an evaporator of the coolant circuit, typically an evaporator assigned to the cooling area and an evaporator assigned to the freezing area of a combination refrigerating device. The length and diameter of the capillary tubes 5 on the one hand and the through cross-sections in the valve body 1 on the other hand are matched one to the other so that the pressure drop at a capillary tube 5 through which coolant flows is at least twice and preferably a multiple of the pressure drop in the valve body 1.

[0017] An inlet pipe 6 coming from a drier 9, having a diameter larger than that of the capillary tube 5, is soldered onto an inlet 7 of the valve body 1, which opens centrally into the chamber 2.

[0018] A valve member 8 in the form of a cylindrical body made of ferromagnetic material is displaceable in the chamber 2 between two end positions in which it respectively closes one of the two outlets 4.

[0019] FIGS. 3 and 4 show views of a housing 12 provided to accommodate the valve body 1 in respectively the same perspectives as those in FIGS. 1 and 2. The housing 12 can be manufactured, for example, by injection moulding from plastic, e.g. from polypropylene. Said housing comprises a substantially rectangular main body 13 which is open at one side, located at the top in FIGS. 3 and 4. A large and a small cover section 14, 15 are joined to the upper edge of the main body 13 by means of film hinges on opposite sides.

[0020] Two opposite walls of the main body 13 each have a U-shaped cut-out which runs in a semicircular fashion in its lower region. The size of the cut out 16 is such that the valve body 1 can be inserted therein with a small amount of play.

[0021] To the right of a line X-X in FIG. 3 the main body 13 is shown in cutaway view. In its interior can be seen a substantially cylindrical coil 17 with two contact tabs 18 for the power supply to the coil, which engage in a chamber 19 moulded onto the main body 13 at the bottom. The chamber 19 has a window 20 through which a connector 21 can be inserted and can make contact with the contact tabs 18.

[0022] Two iron castings 22 shown by dashed lines in FIG. 4 are riveted onto the core of the coil 18'. At their ends away from the coil core, the iron castings 22 form two pole pieces 33 in the form of semi-cylindrical grooves which, after attachment of the valve body 1, abut against said valve body.

[0023] The two cover sections 14, 15 are constructed such that after attachment of the valve body 1, they can be clipped shut and located, as shown in FIG. 5. Said cover sections completely cover the upper side of the housing except for a circular hole bounded by both cover sections 14, 15, that accommodates the inlet pipe 6 as shown in FIG. 6. For locking in the closed state the large cover section 14 is provided with two locking lances 24 which in the closed state engage in eyes 25 on the opposite wall of the main body 13. The small cover section 15 is provided with projections which in the closed state of the cover are covered by the large cover section 14. Thus, both cover sections are held closed by locating the large cover section 14 in the eyes 25.

[0024] Moulded onto the large cover section 14 complementary to the cut--outs 16 of the main body 13 are semi circularly cut-out cross-pieces 28 which together with the cut-outs 16 encompass the valve body 1 when the cover is closed. By this means and by the inlet pipe 6 being held in the circular hole formed by the two cover sections 14, 15, the valve body 1 is completely fixed in the housing 12.

[0025] At least one of the cover sections 14, 15 has a projection 26 directed into the interior of the housing when the cover is closed, which holds a permanent magnet 27. In each case the size of the projection 26 is such that the permanent magnet 27 comes to lie approximately at the height of the axis of the valve body 1 which connects the two capillary tubes 5 when the cover is closed. In this case, one pole of the permanent magnet 27 is facing the valve body 1; if two magnets are used, like poles of these magnets respectively face one another on either side of the valve body 1. The permanent magnet 27 generates a substantially axially oriented magnetic field in the chamber 2, which holds the valve member 8 respectively in contact with that valve seat 3 in whose vicinity it is located. If a current surge of suitable polarity is applied to the coil 17, this generates in the chamber 2 a magnetic field in the opposite direction to the induced magnetisation of the valve member 8, which moves the valve member 8 to the opposite valve seat 3. Thus, the valve can be switched by applying pulses of alternating polarity to the coil.

[0026] The valve according to the invention simplifies the structure of a coolant circuit since the number of parts is reduced by directly joining the valve body to the capillary tubes 5 which are used as a pressure-relieving element for the coolant. As a result of the valve being joined directly to the drier 9, these two elements can be installed jointly as a compact unit. This also helps to simplify the structure of the coolant circuit.