Patent Application
20150345844
This application claims priority to German Patent Application No. DE 10 2014 101 585.1 filed on Feb. 2, 2014 and German Patent Application No. DE 10 2014 113 793.0 filed on Sep. 24, 2014, the entire disclosures of which are hereby incorporated herein by reference.
The invention relates to a coolant accumulator, in particular for motor vehicle coolant circuits. Coolant accumulators, also known as coolant collectors, are used in coolant circuits to separate liquid coolant from coolant vapors, while at the same time, coolant oil is separated and collected as well. The coolant accumulator is further used for adding coolant oil to the coolant vapor in the finest possible dispersion, in order to feed the coolant oil to the coolant compressor.
In certain coolant circuits, it can be advantageous to implement an additional functionality into the coolant accumulator. This is the integration of a heat exchanger as an internal heat exchanger into the component, for instance by way of an undercooling heat exchanger. In coolant circuits using R744 as a coolant, for instance, this can be advantageously implemented.
Coolant accumulators, therefore, can be summarized as having the task of separating the liquid from the gaseous phase. Furthermore, through the siphoning of the gaseous phase, the construction of the coolant accumulators achieves the oil return flow into the coolant compressor, and it also implements a filter for the liquid phase in the coolant accumulator.
Various forms of coolant accumulators are known from prior art. From U.S. Pat. Appl. Pub. No. 2005/0229632 A1, a coolant oil for the liquid phase of an air-conditioning system is known, which was conceived specifically for the requirements of a cooling system using CO2 by way of coolant. The siphoning of the coolant is done by way of a piping system, the end of which is centrally positioned in the upper region of the accumulator. No internal heat exchanger is integrated into this coolant accumulator, and the pipe for siphoning the coolant vapors leads down in an arch, from the axially centered upper end, following the contours of the bottom, and then back up to the off-center outflow point.
From U.S. Pat. Appl. Pub. No. 2004/0093894 A1, a coolant accumulator is known for the liquid phase of the coolant of an air conditioning system which has an axially centered straight pipe for the siphoning of the coolant, with an inflow point in the upper region, and an outflow point at the bottom.
U.S. Pat. Appl. Pub. No. 2008/0041093 A1 discloses a coolant accumulator for air-conditioning systems which has a piping system consisting of coaxially arranged external and internal pipes, with an inflow point in the upper region of the accumulator into the external pipe, and an outflow point at the axially centered outflow point of the internal pipe, upward out of the accumulator.
The purpose of the invention is to provide a coolant accumulator, and specifically, a coolant accumulator for motor vehicle coolant circuits, capable of achieving an effective separation between the liquid and gaseous phases, and which also has a pipe for the siphoning of the gaseous phase, including the oil return flow. The coolant accumulator must be manufacturable in a cost-effective and technically not too complex way. Moreover, the functionality of the components must be guaranteed for the long term by way of the ability to integrate a filter array for the returning coolant oil.
This task is achieved by way of the object with the characteristics of Patent Claim 1. Further developments are indicated in the subsidiary patent claims.
The task of the invention is solved in particular by way of a coolant accumulator for motor vehicle coolant circuits which features an accumulation tank with a suction pipe assembly in it. The suction pipe assembly consists of an external suction pipe and an internal suction pipe, which are positioned coaxially and at a distance from each other inside the accumulation tank. The external suction pipe and the internal suction pipe are connected with each other by way of a connecting piece at the respective lower ends of the pipes. Via this connecting piece, the flow path of the coolant extends in the annular gap between the external and the internal suction pipe from the top into the connecting piece, where it is redirected inward, and then flows upward through the internal suction pipe. The connecting piece features a radially positioned oil balancing bore, which connects an oil sump region of the accumulation tank with the flow path in the suction pipe assembly.
According to an embodiment of the invention, the oil balancing bore in the connecting piece is at the height of half the distance between the lower end of the internal suction pipe and the lower end of the connecting piece.
Desirably, the connecting piece is surrounded in the region of the oil balancing bore by a filter, which filters the oil that is drawn in from the oil sump region before entering the oil balancing bore.
The connecting piece is specifically suited for the pressure loss minimization at the 180° flow reversal of the flow path. Preferentially, a rounded ring-shaped contour is provided, so that the flow path is guided radially from the outside inward, in a 180° reversal.
For the reception of the external suction pipe, a pine tree profile is provided at the upper end of a connecting piece, onto which the external suction pipe can be shrunk in a technically simple manner.
In the region of the oil balancing bore, the connecting piece shown features a wall thickness between 0.4 mm and 3 mm.
The oil balancing bore itself as shown features a diameter between 0.2 mm and 3 mm.
For the concentration of the coolant oil in the accumulation tank, the oil sump region is conically tapered off towards the bottom, so that even when the coolant oil volume is low, the coolant oil level is relatively high, so that the oil balancing bore is always within the range of the separated coolant oil below the liquid coolant.
The filter for the coolant oil is preferentially embodied as a filter ring. For the reception of the filter ring, it is advantageous that the connecting piece features annular bulges. According to an advantageous embodiment, the accumulation tank is positioned in a pressure-resistant outer container, and an internal heat exchanger for the coolant circuit is located between the accumulation tank and the outer container. The embodiment of the internal heat exchanger is as a coiled tube in the annular gap between the accumulation tank and the outer container. It was proven to be particularly advantageous that the accumulation tank is made out of a synthetic material with a low degree of water absorption, such as polybutylene terephthalate, polyethylene, or polypropylene.
The accumulation tank is closed at the top by an accumulation tank cover, which features an opening in the region of the manifold, which is embodied such that it can be closed with a cap. For an efficient separation of the liquid and vapor mixture it is advantageous to embody the accumulation tank cover as a cyclone for the separation of this mixture.
Functionally, the accumulator separates not only liquid coolant, but also coolant oil. The coolant oil, however, must be removed again from the sump of the accumulator, and be added to the coolant mass flow circulating in the coolant circuit, or be returned to the coolant compressor. This is done by way of a suction pipe, through which the gaseous coolant flows out. In the accumulator sump there is a small oil balancing bore, through which the gas flow siphons, or sucks out, the coolant oil. Through this oil balancing bore, however, coolant oil is not the only substance that enters into the coolant vapor flow, but so does liquid coolant, which adds a liquid component to the exiting gaseous phase. This inevitable liquid component should typically not exceed 10% of the total mass of the flow. In order to minimize this problem, the correct diameter of the oil balancing bore was determined, which is typically very small, in the range of 0.2 to 3 mm. Typical production tolerances therefore carry a significant functional weight. Furthermore, the geometric orientation of the oil balancing bore has a considerable impact on the sensitivity and the amount of the siphoned liquid. According to one aspect of the invention, the geometric orientation determines whether production tolerances can be compensated or not, or whether the siphoned liquid quantities are always within the specified range.
The advantages of the invention consist of a cost-effective way to produce the coolant accumulator. Furthermore, the coolant accumulator tank can be produced from synthetic material, which allows for better heat insulation from the environment. Constructively speaking, there is a considerable freedom of design, which is advantageous in particular for the construction of the cyclone as a liquid separator. Due to the conically tapering oil sump region, the oil sump volume is minimized, allowing for the reliable siphoning of coolant oil and for a relatively low degree of coolant liquid.
In the embodiment of the coolant accumulator as a combined part which integrates the accumulator and the internal heat exchanger in a single component, the internal heat exchanger is positioned coaxially around the accumulation tank. This has the additional advantage that the wall of the accumulation tank is not warmed up by the heat of the engine compartment, but rather, is insulated against the intrusion of heat from the engine compartment by the low pressure side of the internal heat exchanger.
Other details, characteristics, and advantages of the embodiments of the invention follow from the following description of exemplary embodiments, with reference to the respective drawings:
The following detailed description and appended drawings describe and illustrate various embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner.
In the cylindrical mantle 20 of the outer container 14, the cylindrical connecting piece 6 of the base part 19 and the top part 18, radially, from the outside inward, always concentric to the cylinder axis, are positioned the heat exchanger 15 as a coiled tube, then the accumulation tank 2 for the collection of the liquid coolant, and the suction pipe assembly 3 for guiding the coolant vapor flow. The lower region of the accumulation tank 2 is referred to as oil sump region 9, which tapers conically downward in order to concentrate and collect the coolant oil settling there.
In
In the outer wall of the connecting piece 6, which takes over the guidance of the low pressure flow from the external suction pipe 4 to the internal suction pipe 5, there is an oil balancing bore 7 through which the coolant vapor flow is connected with the oil sump region 9 and with the coolant oil that is collecting there. Via the oil balancing bore 7, the oil moves from the oil sump region 9 into the coolant vapor flow, which is redirected at the end of connecting piece 6 by 180° and then flows into the internal suction pipe 5, and then upward. On the connecting piece 6 there are two annular bulges 12, which serve the purpose of receiving a filter 10 in the form of a filter ring in such a manner as to form a seal.
The external suction pipe 4 is shrink-fitted onto the pine tree profile 13 of the connecting piece 6.
The annular bulges 12 form sealing diameters for the filter 10 which protect the oil balancing bore 7 against contaminants.
According to a further embodiment, a drying agent is positioned in the oil sump region 9 of the accumulation tank 2, such that the oil balancing bore 7 continues to be protected by the filter 10. In this embodiment, a disc-shaped sieve or a filter presses against the surface of the drying agent granulate filing in order to prevent the raising and swirling of the granulate. The sieve, which is not shown, has an outer diameter corresponding to the inner diameter, or the contours, of the accumulation tank 2. In its middle there is a corresponding opening for the suction pipe assembly 3.
The oil balancing bore 7 is situated radially with respect to the axis of the coolant accumulator 1 and below the lower end of the internal suction pipe 5, approximately at the level of half the distance between the lower end of the suction pipe 5 and the lower end of the connecting piece 6. The oil balancing bore 7 typically features a diameter between 0.29 mm and 2.1 mm.
A thickness of a wall of the connecting piece 6 corresponds to a length of the oil balancing bore 7, and is typically in the range of 0.49 mm to 2.1 mm.
The coolant accumulator is bounded in the axial direction by the top part 18 and the base part 19. The internal heat exchanger 15 is situated in the upper region. The lower region of the accumulation tank 2 can be seen below the internal heat exchanger 15.
Similarly, a covering plate which protects the external suction pipe 4 against the drawing in of liquid coolant, holds and spaces the internal suction pipe 5 in the upper region. The covering plate is attached to the external suction pipe 4, and features three bars, which guide the internal suction pipe 5 into the external suction pipe 4, and provide for the existence of the annular gap. These bars are also situated in the connecting piece 6. The internal suction pipe 5 is positioned axially against the connecting piece 6 via the cover 16.
The flow path 8 of the coolant vapor mixture extends between the connecting piece 6 and the internal suction pipe 5 towards the axial end of the connecting piece 6, where the flow path 8 is redirected by 180°, first inward, and then upward. The vaporized coolant therefore enters into the internal suction pipe 5, and flows upward again. In the oil sump region 9 of the accumulation tank 2, the connecting piece 6 features an oil balancing bore 7 with a radial orientation with respect to axis of the coolant accumulator 1. The oil balancing bore 7, the flow path 8 in the connecting piece 6 is materially connected with the oil sump region 9, allowing oil from the oil sump region 9 to be drawn in and carried away by the vaporized coolant through the oil balancing bore 7.
In the lower region of the connecting piece 6, adjacent to the pine tree profile 13, annular bulges 12 are situated above and below the oil balancing bore 7 for receiving the external suction pipe 4, which serve for receiving a filter 10.
For the 180° redirection of the flow path 8 at the lower end of the connecting piece 6, the latter features a rounded ring-shaped contour 11 for the purpose of implementing the flow reversal of the flow path 8 with a minimum of loss, in hydrodynamic terms.
For the coolant accumulator 1, this results in a filtration of 100% immediately before the outflow of the coolant vapors on the low pressure side, meaning, after the internal heat exchanger 15. Since the coolant accumulator 1 has a very large internal surface, the potential for unintended penetration of contaminants is relatively high. A filter immediately prior to the outflow of the combined part offers the advantage of a certain intrinsic safety with respect to intolerable contaminations.
A drying agent must be present in the coolant circuit, and typically it is located inside the coolant accumulator 1. For these purposes, for example, pouches made out of a textile fabric may be used, filled with the drying agent silica gel. According to one advantageous embodiment of the invention, hygroscopic plastics are used that are capable of absorbing up to 2 or 3% of water. This corresponds to up to 50% of the absorptive capacity of the drying agent. Therefore, coolant accumulators 1 made out of hygroscopic plastics must either be protected during the production process and during shipping and handling against environmental moisture, or alternatively, the quantity of the drying agent must be increased equivalently. The latter option, however, reduces the storage capacity of the coolant accumulator 1 for liquid coolant. In order to reduce the risk, synthetic materials with very low water absorption are used, such as PBT, PE, or PP.
An advantageous embodiment of the invention consists of the utilization of the capacity of synthetic materials to absorb moisture, and to implement this moisture absorption capacity for the purposes of coolant desiccation. This can lead to a cost reduction for drying agents, as well as to an increased storage capacity of the accumulator for more liquid coolant.
While certain representative embodiments and details have been shown for purposes of illustrating the invention, it will be apparent to those skilled in the art that various changes may be made without departing from the scope of the disclosure, which is further described in the following appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2014 101 585.1 | Feb 2014 | DE | national |
| 10 2014 113 793.0 | Sep 2014 | DE | national |
