Heat storage tank with improved heat insulating performance

Abstract

A heat storage tank, comprises an inner cylinder 81 having a storage section 811 for storing liquid, an opening 812 at a lower position of the storage section 811 and a body 84 in which a liquid inflow channel 841 and a liquid outflow channel 842 are formed. The body blocks the opening 812. When the inner diameter of the inner cylinder 81 is referred to as a tank inner diameter D and the vertical length of the storage section 811 is referred to as a tank height H, D/H≦0.5 holds. Therefore, the storage section 811 is elongated in the vertical direction and the distance between the body 84, which is a main heat radiating portion, and the high temperature water region is increased and, as a result, the high temperature water region is extended in the vertical direction.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat storage tank for thermally insulating and storing a liquid and is effectively applied, particularly, to a cooling device of a water-cooled engine.

2. Description of the Related Art

Conventionally, a system in which a heat storage tank thermally insulates and stores high temperature engine cooling water in it and then the thermally insulated cooling water is used for promoting warm-up of an engine when the engine is started next time (at a cold start) by circulating the thermally insulated cooling water into the engine, or is used for immediately heating a vehicle compartment by supplying the thermally insulated cooling water to the heater core of a heating device of a vehicle is known (for example, refer to Patent document 1).

[Patent Document 1]

Japanese Unexamined Patent Publication (Kokai) No. 10-71840

Then, the heat insulation performance of a heat storage tank is particularly regarded as an important factor and a further improvement of the heat insulation performance is required.

SUMMARY OF THE INVENTION

The above-mentioned point being taken into account, the object of the present invention is to improve the heat insulation performance of a heat storage tank.

In order to attain the above-mentioned object, a heat storage tank according to a first aspect of the present invention is characterized by comprising an inner cylinder (81) having a storage section (811) for storing liquid and an opening (812) at a lower position of the storage section (811), an outer cylinder (82) accommodating the inner cylinder (81) therein and forming a thermally insulated space (83) between the inner cylinder (81) and itself, and a body (84) in which a liquid inflow channel (841) and a liquid outflow channel (842) for causing the storage section (811) to be communicated with the outside are formed and which blocks the opening (812), wherein if it is assumed that the inner diameter of the inner cylinder (81) is referred to as a tank inner diameter D and the length of the storage section (811) in the vertical direction is referred to as a tank height H in the heat storage tank in which the storage section (811) is a columnar space extending in the vertical direction, D/H≦0.5 holds.

According to this, as shown in FIG. 3, in the region where D/H≦0.5 holds, the temperature of the water after being stored is high and a high heat-insulation performance can be obtained. This is because the storage section is elongated in the vertical direction and the distance between the body, which is a main heat radiating portion, and the high temperature water region (in the vicinity of the top end of the storage section) is increased and therefore the high temperature water region is extended in the vertical direction.

When the inner diameter of the opening and the capacity of the storage section are kept constant, as D/H is reduced, the tank inner diameter D is reduced and the difference in dimension between the tank inner diameter D and the inner diameter of the opening is reduced, therefore, the draw manufacturing performance of the inner cylinder is enhanced and it is possible to integrally form the inner cylinder by, for example, a spinning process.

In a second aspect according to the above-mentioned first aspect, it is possible to use a heat storage tank for storing cooling water that has risen in temperature after cooling a water-cooled internal combustion engine (1) for a vehicle.

The symbols in the parenthesis attached to each means described above indicate a correspondence with a specific means in the embodiments to be described later.

The present invention may be more fully understood from the description of the preferred embodiments of the invention set forth below, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic diagram of a cooling device for a water-cooled engine using a heat storage tank according to an embodiment of the present invention.

FIG. 2 is a section view of the heat storage tank in FIG. 1.

FIG. 3 is a diagram showing a relationship between the ratio (D/H) of the tank inner diameter to the tank height and the heat insulation performance of the heat storage tank.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention is explained below. FIG. 1 is a schematic diagram of a cooling device for a water-cooled engine using a heat storage tank according to an embodiment and FIG. 2 is a sectional view of the heat storage tank in FIG. 1.

In FIG. 1, the cooling device cools cooling water that has risen in temperature after cooling a water-cooled internal combustion engine (hereinafter, referred to as an engine) 1 of a vehicle, not shown, through a radiator 2, and comprises a main cooling water circuit 3 for causing cooling water to flow between the engine 1 and the radiator 2 and an electric water pump 4 for generating a cooling water flow.

A bypass circuit 5 for causing cooling water to flow while bypassing the radiator 2 is connected in parallel with the main cooling water circuit 3. A thermostat 6 provided at the connection point of the main cooling water circuit 3 and the bypass circuit 5 carries out switching control between a case where the cooling water is caused to flow through the bypass circuit 5 and a case where the cooling water is caused to flow through the radiator 2. By the way, switching between the two circuits 3 and 5 is normally controlled such that the cooling water flows through the radiator 2 when the cooling water temperature is equal to or higher than about 80° C. and the cooling water flows through the bypass circuit 5 when the temperature is lower than about 80° C.

A sub-cooling-water circuit 7 for causing the cooling water to flow while bypassing the main cooling water circuit 3 and the bypass circuit 5 is connected in parallel to the main cooling water circuit 3 and the bypass circuit 5. The sub-cooling-water circuit 7 is provided with a heat storage tank 8 for thermally insulating (and storing) heat of cooling water and an electromagnetic opening/closing valve 9 for opening and closing the sub cooling water circuit 7.

Next, the heat storage tank 8 is explained using FIG. 2.

The heat storage tank 8 comprises an inner cylinder 81 and an outer cylinder 82 made of a material excellent in corrosion resistance such as stainless and formed into a bottomed cylindrical shape. The heat storage tank 8 has a structure in which end portions 8a of the inner cylinder 81 and the outer cylinder 82 are welded in a state in which the inner cylinder 81 is accommodated within the outer cylinder 82, and a thermally insulated space 83 substantially in a vacuum state is formed between the inner cylinder 81 and the outer cylinder 82. By the way, the inner cylinder 81 is integrally formed by a spinning process.

Within the inner cylinder 81, a storage section 811 for storing cooling water is formed and the storage section 811 forms a columnar space extending in the vertical direction. Into a small diameter opening 812 and a large diameter opening 813 of the inner cylinder 81 located at the lower portion of the storage section 811, a body 84 made of resin that blocks both the openings 812 and 813 is inserted. By the way, a female screw formed in the large diameter opening 813 of the inner cylinder 81 and a male screw formed at the body 84 are screwed with each other and, thereby, the inner cylinder 81 and the body 84 are joined together.

Between the inner cylinder 81 and the body 84, a ring-shaped rubber packing 85 for sealing between the inner cylinder 81 and the body 84 is arranged. In more detail, the packing 85 is arranged at the boundary between the small diameter opening 812 and the large diameter opening 813 in the inner cylinder 81.

In the body 84, a cooling water inflow channel 841 that causes the sub cooling water circuit 7 on the opening/closing valve 9 side to be communicated with the storage section 811 is formed. The end portion of the cooling water inflow channel 841 on the storage section 811 side opens at the position in the vicinity of the small diameter opening 812 of the inner cylinder 81, that is, at the lower position of the storage section 811. The cooling water inflow channel 841 corresponds to the liquid inflow channel of the present invention.

To the end portion of the body 84 on the storage section 811 side, a pipe 10 is attached. Then, through an in-body cooling-water-outflow channel 842 formed in the body 84 and an in-pipe cooling-water-outflow channel 101 formed in the pipe 10, the sub-cooling-water circuit 7 on the water pump 4 side and the storage section 811 are communicated with each other. The end portion of the in-pipe cooling water outflow channel 101 on the storage section 811 side opens at the position in the vicinity of the top wall of the inner cylinder 81, that is, at the position in the vicinity of the top end of the storage section 811. The in-body cooling-water-outflow channel 842 corresponds to the liquid outflow channel of the present invention.

To the end portion of the body 84 on the storage section 811 side, a mixture prevention plate 11 having a substantially cup-like shape is attached so as to enclose the end portion of the cooling water inflow channel 841 on the storage section 811 side. In the mixture prevention plate 11, a plurality of outflow holes 111 are formed and the cooling water that has flowed in from the cooling-water-inflow channel 841 is guided to flow substantially evenly to the storage section 811 side through the outflow holes 111.

An angle 12 is attached to the outer surface of the outer cylinder 82 and the heat storage tank 8 is fixed to a vehicle by means of this angle 12

Next, the operation of a cooling device having the above-mentioned configuration is explained below.

When the temperature of the cooling water becomes high, due to the operation of the engine 1, the opening/closing valve 9 is opened and the high temperature cooling water is caused to flow into the heat storage tank 8. After the engine stops, the high temperature cooling water is thermally insulated and stored in the heat storage tank 8.

Then, when the engine is started, the temperature of the portion in the vicinity of the engine combustion chamber is raised by circulating the cooling water thermally insulated and stored in the heat storage tank 8 through the engine 1.

Specifically, immediately before the engine is started, the water pump 4 is put into operation and the opening/closing valve 9 is opened. Due to this, the low temperature cooling water flows into the storage section 811 of the heat storage tank 8 through the sub-cooling-water circuit 7 and the cooling-water-inflow channel 841.

The cooling water that has flowed in pushes up the high temperature cooling water thermally insulated and stored in the storage section 811 and the high temperature cooling water circulates to the engine 1 through the in-pipe cooling water outflow channel 101, the in-body cooling water outflow channel 842, and the sub cooling water circuit 7.

At this time, the low temperature cooling water flowing into the storage section 811 is designed to push up the high temperature cooling water stored in the storage section 811 evenly with respect to the entire circumference due to the effect of the mixture prevention plate 11. Therefore, the mixture of the low temperature cooling water flowing in and the stored high temperature cooling water is prevented and the high temperature cooling water is caused to circulate to the engine 1.

Next, by using the ratio (D/H) between the inner diameter D of the inner cylinder 81 (hereinafter, referred to as a tank inner diameter) and the length H of the storage section 811 in the vertical direction (hereinafter, referred to as a tank height) as a parameter, the heat insulation performance of the heat storage tank 8 is evaluated. The distance from the top end of the storage section 811, that is, from the top wall of the inner cylinder 81, to the small diameter opening 812 corresponds to the tank height H.

FIG. 3 shows the results of a study wherein the horizontal axis represents the ratio (D/H) between the tank inner diameter D and the tank height H. The vertical axis in FIG. 3 shows the average temperature of the hot water in the heat storage tank 8 after the hot water at an initial temperature of 90° C. is thermally insulated in the heat storage tank 8 for 24 hours.

The tank inner diameter D of the evaluated heat storage tank 8 is set to a constant value, that is, 100 mm, and the inner diameter of the small diameter opening 812 is also set to a constant value, and the tank height H is changed.

As is obvious from FIG. 3, in the region in which D/H≦0.5 holds, the temperature of the hot water after thermally insulated for 24 hours is high and high heat insulation performance can be obtained. This is because the storage section 811 is elongated in the vertical direction and the distance between the body 84, which is a main heat radiating portion, and the hot water region (in the vicinity of the top end of the storage section 811) is increased and the hot water region is extended in the vertical direction. The ratio D/H may be set in order to satisfy several requirements for the heat storage tank such as an inner capacity of water and a vertical height that may be limited for installation of the storage tank on vehicles. In this aspect, the heat storage tank may be designed to satisfy that the ratio D/H is equal to or greater than 0.3. Instead, the ratio D/H may be set equal to or greater than 0.35. Further, the ratio D/H may be set equal to or greater than 0.4 in order to satisfy an installation requirement. On the other hand, the ratio D/H may be set equal to or less than 0.45. Instead, the ratio D/H may be set equal to or less than 0.4 in order to improve hot water temperature.

While the invention has been described by reference to specific embodiments chosen for the purposes of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art, without departing from the basic concept and scope of the invention.

Claims

1. A heat storage tank comprising:

an inner cylinder having a storage section for storing liquid and an opening at a lower position of the storage section;

an outer cylinder accommodating the inner cylinder therein and forming a thermally insulated space between the inner cylinder and the outer cylinder; and

a body in which a liquid inflow channel and a liquid outflow channel for causing the storage section to be communicated with an outside are formed, the body blocking the opening,

wherein an inner diameter of the inner cylinder is referred to as a tank inner diameter D, a length of the storage section in a vertical direction is referred to as a tank height H in the heat storage tank in which the storage section is a columnar space extending in the vertical direction, and a ratio D/H satisfies the following: D/H≦0.5.

2. The heat storage tank as set forth in claim 1, mounted in a vehicle having a water-cooled internal combustion engine that is cooled by cooling water, wherein liquid stored in the storage section is cooling water that has risen in temperature after cooling the water-cooled internal combustion engine.