JP4284591B2 - LPG heat exchanger - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an LPG heat exchanger used in an LPG supply device that supplies liquid LPG (liquefied petroleum gas) to an engine by heating and vaporizing the liquid LPG (liquefied petroleum gas), adjusting the pressure to a predetermined pressure, and sending it to an intake pipe.
[0002]
[Prior art]
The use of LPG as a fuel for spark ignition engines is widely known, and vaporized gas decompressed to about atmospheric pressure using a vaporizer (regulator) and a mixer is sucked into an intake pipe and supplied to the engine. This method has been used for some time. On the other hand, instead of this well-known method, as described in Japanese Utility Model Publication No. 59-43659, a method of injecting liquid as it is into the intake pipe has been proposed. There is a problem that it is easily affected and vaporizes easily, and the injection amount becomes unstable.
[0003]
On the other hand, as described in JP-A-6-17709 and the like, the method of adjusting LPG to vapor gas having a predetermined positive pressure and injecting it into the intake pipe has an advantage that the injection amount is not unstable. Therefore, it is advantageous for practical use. As a means for heating and vaporizing the liquid LPG, it is customary to incorporate a heat exchanger using engine cooling water in the regulator or arrange it on the inlet side to heat and vaporize the LPG with engine cooling water. .
[0004]
However, the heating and vaporizing means using such engine cooling water has a disadvantage that the liquid LPG cannot be sufficiently vaporized because the cooling water is at a low temperature when cold.
Therefore, for example, as described in JP-A-5-223014 and JP-A-11-324813, a vaporizer that vaporizes LPG and reduces the pressure to about atmospheric pressure uses heat of engine cooling water. In addition, it has been proposed to arrange an electric heater (PTC heater) in the LPG path so that LPG can be vaporized even when the cooling water is at a low temperature.
[0005]
However, in the case of an automobile engine, the heating capacity of an electric heater that uses electric power obtained from a storage battery or a generator is significantly lower than that of cooling water. Therefore, in the above-mentioned means in which the electric heater is installed in the same path of the LPG that is heated and vaporized by the engine cooling water, depending on the engine operating state immediately after the low temperature start, the LPG having a flow rate exceeding the vaporizing ability of the electric heater remains liquid. May be delivered to the intake line. That is, when the engine coolant is at a low temperature and the LPG flow rate exceeds the vaporization capacity of the electric heater, the liquid LPG is sent to the intake pipe and the air-fuel mixture becomes excessive, and the engine stops and cannot be restarted. This causes a problem. As countermeasures, it is conceivable to increase the size or number of electric heaters. However, the price of regulators and heat exchangers will increase, and the power consumption associated with this will increase significantly. In some cases, the shortage of heating capacity is not solved.
[0006]
[Problems to be solved by the invention]
The present invention is intended to solve the above-described problems. The engine cooling water and the electric power used in the LPG supply device that heats and vaporizes the liquid LPG and adjusts the liquid LPG to a predetermined pressure and supplies it to the intake pipe. For LPG heat exchangers that are used in combination with a heater, when LPG vaporization tends to be impossible or insufficient at low temperatures, it is surely vaporized with a small amount of power consumption and sent to the intake pipe, and cold startability The challenge is to increase
[0007]
[Means for Solving the Problems]
Therefore, the present invention is an LPG heat exchanger that is disposed on the inlet side of a pressure regulator in an LPG supply device that heats and vaporizes liquid LPG, adjusts the liquid LPG to a predetermined pressure, and sends the liquid LPG to the intake pipe of the engine. A main heat exchanger that is arranged in parallel to heat and vaporize the liquid LPG with engine cooling water, a sub heat exchanger that heats and vaporizes the liquid LPG with an electric heater, and the liquid LPG delivered from the cylinder are selectively used as the two heat exchangers. A flow path switching means for flowing in, and an inflow amount limiting means provided on the inflow side of the auxiliary heat exchanger, wherein the flow path switching means causes the liquid LPG to flow through the main heat when the engine coolant temperature is higher than a predetermined temperature. The liquid LPG is operated to flow into the auxiliary heat exchanger when the temperature is lower than a predetermined temperature, and the inflow amount limiting means converts the inflow amount of the liquid LPG into the vaporization capacity of the auxiliary heat exchanger. It was limited to the inside.
[0008]
Thereby, even when the temperature of the engine cooling water flowing into the main heat exchanger is low and insufficient for vaporizing LPG, the electric heater is used by flowing the liquid LPG into the sub heat exchanger using the flow path switching means. And can be heated to a vaporizable temperature. In addition, since the required engine fuel flow rate at the time of starting is relatively small, an inflow amount limiting means is provided on the LPG inflow side of the auxiliary heat exchanger so that LPG exceeding the vaporization capacity is not allowed to flow. With a small number of electric heaters, the gas can be completely vaporized with a small amount of power consumption and can be started well.
[0009]
In addition, in the above heat exchanger, if the sub heat exchanger is accommodated in the main heat exchanger, the entire heat exchanger becomes compact, and in addition, the residual heat of the sub heat exchanger is heated in the main heat exchanger. Therefore, the energy efficiency is high.
[0010]
Further, in the above heat exchanger, the sub-heat exchanger has a space for forming a main heat exchange chamber on the entire outer periphery thereof, and is accommodated in the housing of the main heat exchanger, so that the electric heater If there is a space for forming the auxiliary heat exchange chamber on the outer periphery and is accommodated in the housing of the auxiliary heat exchanger, heat is transferred from the entire outer periphery of the electric heater to the LPG of the auxiliary heat exchange chamber, and Since the heat generated in the heat transfer from the entire outer periphery of the exchanger housing to the LPG in the main heat exchange chamber can be used to the full by reducing the amount of heat released to the atmosphere, energy efficiency is further increased. be able to.
[0011]
Furthermore, the flow switching means in the heat exchanger described above includes a main on-off valve provided in a main inflow passage through which the liquid LPG flow path extending from the cylinder branches to allow the liquid LPG to flow into the main heat exchanger, and a sub heat exchanger It is assumed that the two on-off valves are provided in a sub-inflow passage through which the liquid LPG flows into the two on-off valves. In addition to the fact that one of the two on-off valves is open, the other is closed. It was possible to speak.
[0012]
As a result, for example, when switching from heating by the auxiliary heat exchanger to heating by the main heat exchanger after engine startup, it is possible to provide an overlap time for passing both in parallel at the same time, which occurs when the flow path is switched. It is possible to prevent the fuel supply from being interrupted. Further, even when the fuel supply amount is insufficient with only the main heat exchanger during high load operation, it can be easily handled by using the auxiliary heat exchanger in combination.
[0013]
Furthermore, although the vaporization temperature of LPG varies depending on its composition, this LPG composition can be estimated using a predetermined calculation method based on the temperature and pressure of LPG. Therefore, with respect to the flow path switching means described above, the main heat exchanger and the main heat exchanger, based on the engine coolant temperature that can estimate the LPG composition based on the cylinder temperature and pressure and vaporize the LPG calculated based on the estimation result, The liquid LPG was operated to flow into one of the auxiliary heat exchangers. This makes it possible to select and switch the heat exchanger used for heat vaporization according to the composition of LPG, so that more reliable vaporization of LPG can be realized.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described in detail below with reference to the drawings. In the fuel supply apparatus schematically shown in FIG. 1, in the present embodiment, the flow path switching means is a switching device 6, an inflow amount. The limiting means is the orifice 22h. Then, the LPG stored in the cylinder 5 is supplied to the fuel injection valve 7 installed in the intake pipe 4b of the engine 4 through the liquid LPG flow path 9A and the gas LPG flow path 9B. A heat exchanger 2 and a pressure regulator 3 are arranged.
[0015]
The LPG stored in a liquid state in the cylinder 5 is sent to the switch 6 through the liquid LPG flow path 9A. A temperature sensor 11 a and a pressure sensor 12 are arranged in the cylinder 5, and the temperature and pressure of the liquid LPG in the cylinder 5 detected by the cylinder 5 are input to the electronic control device 10.
[0016]
The switching device 6 is provided with an electromagnetically driven main on / off valve 6a and a sub on / off valve 6b in a main inflow passage 9a and a sub inflow passage 9b formed by dividing the liquid LPG passage 9A into two, The main inflow passage 9a is connected to an inlet 21a provided at the bottom of the main heat exchanger 21 of the heat exchanger 2 described later, and the sub inflow passage 9b is provided at the bottom of the sub heat exchanger 22 of the heat exchanger 2 described later. Connected to the inlet 22a. These on-off valves 6 a and 6 b are controlled to be opened and closed by an electronic control device 10.
[0017]
The heat exchanger 2 includes a main heat exchanger 21 and a sub heat exchanger 22, and has a double structure in which the sub heat exchanger 22 is accommodated inside the main heat exchanger 21. The main heat exchanger 21 has a cooling water chamber 23 which is arranged in a jacket shape surrounding the periphery of the main heat exchanger 21 and through which the engine cooling water passes, and the pressure regulator 3 converts the liquid LPG inflow port 21a and the gas LPG vaporized therein. Are provided at the opposite end on the diagonal line.
[0018]
The engine cooling water in the cooling water jacket 4a provided in the engine 4 is sent to the cooling water chamber 23 of the heat exchanger 2 via the cooling water delivery path 8a. And the engine cooling water which heated the main heat exchanger 21 in the heat exchanger 2 is returned and circulated to the cooling water jacket 4a via the cooling water return path 8b.
[0019]
2 and 3, the main heat exchanger 21 has a rectangular housing 21B, and the auxiliary heat exchanger 22 has a rectangular housing 22B having a shape substantially similar to the housing 21B of the main heat exchanger 21. The sub heat exchanger 22 has a space on the entire outer periphery thereof and is accommodated in the main heat exchanger 21, and this space forms a main heat exchange chamber 21A. The sub heat exchanger 22 accommodated in the main heat exchanger 21 is provided in an inlet 22 a provided substantially adjacent to the inlet 21 a of the main heat exchanger 21 and in an outlet 21 b of the main heat exchanger 21. The gas LPG generated by the two heat exchangers 21 and 22 is sent from one outlet to the inlet 3 a of the pressure regulator 3.
[0020]
In addition, an orifice 22h, which is an LPG inflow amount limiting means, is arranged at the inlet 22a so that liquid LPG exceeding the vaporization capacity of the auxiliary heat exchanger 22 does not flow in. The auxiliary heat exchanger 22 has two PTC heaters 24c and 24d, which are electric heaters, with the front and rear surfaces thereof being in close contact with the inner wall surfaces of the heat transfer walls 24e and 24f, respectively. The electric heater 24 is housed. The heat transfer walls 24e and 24d also serve as electrodes and energize the PTC heaters 24c and 24d. The electric heater 24 is accommodated with a space on the entire outer periphery thereof, and this space forms a sub heat exchange chamber 22B.
[0021]
The heat exchanger 2 has a compact and simple configuration as described above, and the inflow ports 21a and 22a and the outflow ports 21b and 22b are arranged diagonally. Complete heat vaporization and complete vaporization. In particular, the auxiliary heat exchanger 22 is highly efficient because heat is exchanged on the entire surfaces of the heat transfer walls 24e and 24f and the peripheral wall 24g of the electric heater 24. Therefore, the PTC heaters 24c and 24d are small or small in number. Therefore, there is an advantage that power consumption is small. The inflow ports 21a and 22a are arranged at the bottom of the heat exchangers 21 and 22, and the outflow ports 21b and 22b are arranged at the top, so that the liquid LPG having a high specific gravity remains in the liquid state. It is hard to be sent out from.
[0022]
And the pressure regulator 3 arrange | positioned connected to the exit of the heat exchanger 2 has the pressure regulation chamber 3c and the back chamber 3d divided by the diaphragm 3e, and the pressure of the pressure regulation chamber 3c is more than a setting pressure. When the pressure becomes lower, the diaphragm 3e opens the inlet valve 3f and the gas LPG generated by the heat exchanger 2 flows into the pressure regulating chamber 3c from the inlet 3a connected to the outlets 21b and 22b. By closing 3f and stopping the inflow to the pressure regulating chamber 3c, the pressure regulating chamber 3c has the gas LPG decompressed to a constant positive pressure, and is similar to the conventional device. The gas LPG delivered from the outlet 3b of the pressure regulator 3 is injected from the fuel injection valve 7 installed in the intake pipe 4b via the gas LPG channel 9B.
[0023]
Next, in the present embodiment, the temperature and pressure of the liquid LPG in the cylinder 5 are detected by the temperature sensor 11a and the pressure sensor 12, and based on these values, the electronic control unit 10 uses the predetermined calculation method to calculate the LPG. The composition can be calculated. That is, since propane and butane composing LPG have different vaporization temperatures, the vaporization temperature changes depending on the LPG properties (propantobutane ratio). Therefore, the flow path can be switched by estimating the fuel properties using a predetermined method. The reference temperature of engine cooling water for can be calculated.
[0024]
For example, at the time of starting the engine, in the case of 100% propane, it is possible to vaporize this using the main heat exchanger 21 even if the engine coolant temperature is −10 ° C. On the other hand, in the case of 20% propane, when the engine coolant temperature is −10 ° C., the main heat exchanger 21 cannot evaporate, so it is necessary to heat with an electric heater. In this case, the auxiliary heat exchanger 22 is used. After the engine is started, the main heat exchanger 21 is switched to use after the engine coolant temperature rises to 10 to 30 ° C.
[0025]
In the present embodiment, the electric controller 10 determines the ratio of propane and butane at a predetermined temperature and pressure based on the temperature and pressure of the liquid LPG in the cylinder 5 and determines the reference temperature based on the ratio. I am doing so. That is, the electronic control device 10 calculates the switching reference temperature from the temperature and pressure of the LPG detected by the temperature sensor 11a and the pressure sensor 12 provided in the cylinder 5, and detects by the temperature sensor 11b provided in the cooling water jacket 4a. Compared with the engine coolant temperature, the necessity of switching is determined.
[0026]
When the engine cooling water has a temperature that is impossible or insufficient for vaporizing the LPG, the liquid LPG flows into the auxiliary heat exchanger 22 and is heated and vaporized by the PTC heaters 24c and 24d, and the LPG is directed toward the pressure regulator 3. Is sent out. At this time, the inlet 22a of the auxiliary heat exchanger 22 is provided with the orifice 22h as the inflow amount limiting means, so that an amount of LPG exceeding the vaporization capacity of the auxiliary heat exchanger 22 does not flow. Therefore, normally, a high-load operation cannot be performed immediately after the engine is started at a low temperature, but the flow of excess LPG to the heat exchanger 2 is restricted, and liquid LPG is sent to the intake pipe 4b to cause excess mixture. The inconvenience of inducing darkness can be prevented.
[0027]
When the temperature of the engine coolant detected by the temperature sensor 11b of the coolant jacket 4a reaches a temperature suitable for vaporization, the sub-open / close valve 6b is closed and the main open / close valve 6a is opened according to a command from the electronic control unit 10. Let me speak. At that time, before the sub on-off valve 6b is closed, the main on-off valve 6a is opened, and an overlap time is provided in which the liquid LPG passes through both heat exchangers at the same time.
[0028]
That is, the switching device 6 can achieve the object of the present invention even with a complete switching system using a single directional switching valve, but the main on-off valve 6a on the inlet side of the main heat exchanger 21 and the auxiliary heat exchanger 22 According to the present embodiment in which each of the sub open / close valves 6b is provided, there is an advantage that the fuel supply interruption can be prevented by providing an overlap time at the time of switching. Furthermore, when a situation occurs in which fuel supply is insufficient in heat exchange by the main heat exchanger 21 during high load operation, heat exchange is performed by the sub heat exchanger 22 in addition to the main heat exchanger 21 to ensure the required fuel flow rate. It is also possible to do.
[0029]
When the engine cooling water rises to a predetermined temperature after the engine is started, the LPG flow path is switched via the main heat exchanger 21, but the residual heat of the auxiliary heat exchanger 22 is not released into the atmosphere, but the main heat exchanger. Since the inside of the engine 21 is heated, the engine cooling water reaches a predetermined temperature, but it can be completely vaporized even at a relatively low temperature stage, and the engine cooling water temperature is sufficient without causing malfunction of the engine. It is possible to shift to a state where the vaporization rises to stable vaporization. In addition, although the sub heat exchanger 22 may be installed in parallel outside the main heat exchanger 21, when it is installed as in the present embodiment, the LPG flow path is connected to the LPG in the main heat exchanger 21. This is advantageous in that the vaporization can be completed.
[0030]
The heat exchanger of the present invention is not limited to the one arranged on the inlet side of the regulator in the system in which the gas LPG is adjusted to a predetermined positive pressure and sent to the fuel injection valve. The system for sucking into the pipeline can be applied as it is by changing the set pressure of the regulator.
[0031]
【The invention's effect】
As described above, according to the present invention, heat exchange of LPG using both the engine cooling water and the electric heater used in the LPG supply device that heats and vaporizes the liquid LPG and adjusts the liquid LPG to a predetermined pressure and supplies it to the intake pipe. When the vaporization of LPG is difficult or insufficient at low temperatures, it can be reliably vaporized with low power consumption and sent to the intake pipe to improve the cold startability. is there.
[Brief description of the drawings]
FIG. 1 is a layout view of a fuel supply device in which an LPG heat exchanger according to an embodiment of the present invention is disposed.
FIG. 2 is an enlarged longitudinal sectional view of the LPG heat exchanger in FIG.
3 is a cross-sectional view taken along line XX of FIG.
2 heat exchanger, 3 pressure regulator, 3a, 21a, 22a inlet, 3b, 21b, 22b outlet, 3c pressure regulating chamber, 3d back chamber, 3e diaphragm, 3f inlet valve, 4 engine, 4a cooling water jacket, 4b Intake pipe, 5 cylinder, 6 switch, 6a main on-off valve, 6b sub on-off valve, 7 fuel injection valve, 8a cooling water delivery path, 8b cooling water return path, 9A liquid LPG flow path, 9B gas LPG flow path 9a Main inflow passage, 9b Sub inflow passage, 10 Electronic control device, 11a, 11b Temperature sensor, 12 Pressure sensor, 21 Main heat exchanger, 21A Main heat exchange chamber, 21B, 22B Housing, 22 Sub heat exchanger, 22A Sub heat exchange chamber, 22h Orifice, 23 Cooling water chamber, 24 Electric heater, 24c, 24d PTC heater, 24e, 24f Heat transfer wall, 24g Perimeter wall

Claims (6)

An LPG heat exchanger disposed on the inlet side of a pressure regulator in an LPG supply device that heats and vaporizes liquid LPG and adjusts the liquid LPG to a predetermined pressure and sends it to an intake pipe of an engine,
A main heat exchanger that is arranged in parallel to heat and vaporize the liquid LPG with engine cooling water, a sub heat exchanger that heats and vaporizes the liquid LPG with an electric heater, and the liquid LPG delivered from the cylinder are selectively used as the two heat exchangers. A flow path switching means for inflow, and an inflow amount limiting means provided on the inflow side of the auxiliary heat exchanger,
The flow path switching means operates to cause the liquid LPG to flow into the main heat exchanger when the engine coolant temperature is higher than a predetermined temperature, and to cause the liquid LPG to flow into the sub heat exchanger when the temperature is lower than the predetermined temperature. The inflow amount limiting means limits the inflow amount of the liquid LPG within the vaporization capacity of the sub heat exchanger.
An LPG heat exchanger characterized by the above. The LPG heat exchanger according to claim 1, wherein the sub heat exchanger is housed in the main heat exchanger. The sub heat exchanger has a space forming a main heat exchange chamber on the entire outer periphery thereof and is housed in a housing of the main heat exchanger, and the electric heater has a space forming a sub heat exchange chamber on the entire outer periphery thereof. The LPG heat exchanger according to claim 2, wherein the LPG heat exchanger is housed in a housing of the auxiliary heat exchanger. The LPG heat exchanger according to claim 1, 2 or 3, wherein the electric heater of the auxiliary heat exchanger is a PTC heater. The flow path switching means branches from a liquid LPG flow path extending from the cylinder, and a main on-off valve provided in a main inflow passage for allowing the liquid LPG to flow into the main heat exchanger, and the liquid LPG flows into the sub heat exchanger. A secondary on / off valve provided in the secondary inflow passage to be opened, and the two on / off valves can be opened together in addition to the other being closed when one is open. The LPG heat exchanger according to claim 1, 2, 3 or 4, wherein the heat exchanger is capable of being made. The flow path switching means estimates the composition of LPG based on the temperature and pressure of the cylinder, and uses the main heat exchanger and auxiliary heat based on the engine coolant temperature that can vaporize the LPG calculated based on the estimation result. 6. An LPG heat exchanger according to claim 5, wherein the LPG heat exchanger is configured to actuate liquid LPG into any of the exchangers.

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