Cooling system for bi-fuel vehicles

Abstract

To provide a cooling device for a bi-fuel vehicle capable of improving fuel economy of a bi-fuel internal combustion engine while activating a catalyst by protecting the catalyst.SOLUTION: A cooling device 20 for a vehicle 1 including an engine 2 that uses gasoline and CNG as fuel includes a temperature control section 40 that controls a temperature of the engine 2 and a temperature of exhaust gas discharged from the engine 2 on the basis of a type of fuel used by the engine 2 and an operating state of an EGR device 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cooling device for a bi-fuel vehicle. [Background technology]

[0002] BACKGROUND ART Conventionally, engines equipped with an EGR device are known that recirculate a portion of exhaust gas as EGR gas to the intake side of the engine to lower the combustion temperature in order to reduce harmful components in the exhaust gas and improve fuel efficiency.

[0003] This engine is equipped with an exhaust gas purification device for removing air pollutants contained in the exhaust gas and purifying the exhaust gas.

[0004] When gasoline is used as engine fuel, the combustion temperature of the gasoline is high, so the temperature of the exhaust gas needs to be lowered to protect the catalyst.

[0005] A known example of an engine that can lower the temperature of exhaust gas is one in which a cooling water passage is provided around the outer periphery of the exhaust manifold, a flow control means is provided in the cooling water passage, and the flow control means is controlled so that the exhaust gas reaches a temperature suitable for exhaust gas purification (see Patent Document 1).

[0006] When the temperature of the exhaust gas is high, this engine can cool the exhaust gas by opening the flow control valve to allow cooling water to flow into the exhaust manifold. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 4519570 Summary of the Invention [Problem to be solved by the invention]

[0008] Meanwhile, bi-fuel vehicles are known that are equipped with two types of fuel, such as gasoline and CNG (Compressed Natural Gas), and select one of the fuels to use as the running fuel.

[0009] In such bi-fuel vehicles, the combustion temperature of CNG is lower than that of gasoline, so if the exhaust gas is cooled when using CNG in the same way as when using gasoline, the catalyst temperature may fall below its activation temperature.

[0010] For this reason, it is possible to prevent the combustion temperature from dropping by, for example, reducing the amount of EGR gas introduced to the intake side, but reducing the amount of EGR gas introduced to the intake side may result in a deterioration in fuel efficiency.

[0011] In the engine described in Patent Document 1, for example, when using CNG, which has a low exhaust gas temperature, it is conceivable to close the flow control valve to prevent cooling water from flowing into the exhaust manifold, thereby not cooling the exhaust gas.

[0012] However, in a bi-fuel vehicle, closing the flow rate adjustment means when using CNG can prevent the exhaust gas from becoming overcooled, but the cooling water flowing through the cooling water passage in the exhaust manifold will flow into the engine, which can cause the engine to become overcooled, increasing engine cooling loss and potentially worsening fuel efficiency.

[0013] The present invention has been made in light of the above-mentioned circumstances, and aims to provide a cooling device for a bi-fuel vehicle that can protect the catalyst, activate the catalyst, and improve the fuel efficiency of the bi-fuel internal combustion engine. [Means for solving the problem]

[0014] The present invention relates to a first fuel and has a lower combustion temperature than the first fuel.a cooling device for a bi-fuel vehicle, the cooling device comprising: a bi-fuel internal combustion engine capable of using a second fuel; an intake member provided in the bi-fuel internal combustion engine for introducing intake air into the bi-fuel internal combustion engine; an exhaust member provided in the bi-fuel internal combustion engine for discharging exhaust gas from the bi-fuel internal combustion engine; an exhaust purification device provided downstream of the exhaust member and having a catalyst for purifying the exhaust gas discharged from the exhaust member; and an EGR device for recirculating a portion of the exhaust gas to the intake member as EGR gas, the cooling device comprising: a temperature adjustment unit for adjusting the temperature of the bi-fuel internal combustion engine and the exhaust gas discharged into the exhaust member based on the type of fuel used by the bi-fuel internal combustion engine and the operating state of the EGR device; the temperature adjustment unit has a main cooling water circulation passage section that circulates cooling water through the bi-fuel internal combustion engine, an exhaust cooling water circulation passage section that branches off from the main cooling water circulation passage section and circulates cooling water through the exhaust member, an EGR cooling water circulation passage section that branches off from the main cooling water circulation passage section and circulates cooling water to the EGR device, bypassing the bi-fuel internal combustion engine and the exhaust member, a first flow control valve that is provided in the exhaust cooling water circulation passage section and adjusts the flow rate of cooling water supplied to the exhaust member, and a second flow control valve that is provided in the EGR cooling water circulation passage section and adjusts the flow rate of cooling water supplied to the EGR device, and the flow rate of cooling water flowing through the exhaust cooling water circulation passage section and the EGR cooling water circulation passage section is adjusted based on the type of fuel used by the bi-fuel internal combustion engine and the operating state of the EGR device, and the EGR device has an EGR gas cooling pipe that returns exhaust gas to the intake member, an EGR control valve provided in a gas cooling pipe for adjusting the flow rate of EGR gas flowing through the EGR gas cooling pipe, and an EGR cooler for cooling the EGR gas flowing through the EGR gas cooling pipe, and the temperature adjustment unit has a control unit that controls the first flow rate control valve and the second flow rate control valve based on the type of fuel supplied to the bi-fuel internal combustion engine and an opening degree of the EGR control valve, and the control unit increases the opening degree of the second flow rate control valve relatively to the opening degree of the first flow rate control valve on the condition that the bi-fuel internal combustion engine uses the second fuel and the opening degree of the EGR control valve exceeds a predetermined value, and increases the opening degree of the first flow rate control valve relatively to the opening degree of the second flow rate control valve on the condition that the bi-fuel internal combustion engine does not use the second fuel or the bi-fuel internal combustion engine uses the second fuel and the opening degree of the EGR control valve is equal to or less than a predetermined value It is characterized by: [Effects of the Invention]

[0015] As described above, according to the present invention, the fuel economy of a bi-fuel internal combustion engine can be improved while protecting the catalyst and activating the catalyst. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram of a bi-fuel vehicle equipped with a cooling device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a system configuration diagram of a cooling device for a bi-fuel vehicle according to a first embodiment of the present invention. [Figure 3] FIG. 3 is a flowchart showing the flow of cooling control for a bi-fuel vehicle according to a first embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram of a bi-fuel vehicle equipped with a cooling device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] A cooling device for a bi-fuel vehicle according to one embodiment of the present invention is a cooling device for a bi-fuel vehicle that includes a bi-fuel internal combustion engine that can use a first fuel and a second fuel of a different type from the first fuel, an intake member that is provided in the bi-fuel internal combustion engine and that introduces intake air into the bi-fuel internal combustion engine, an exhaust member that is provided in the bi-fuel internal combustion engine and through which exhaust gas is discharged from the bi-fuel internal combustion engine, an exhaust purification device that is provided downstream of the exhaust member and has a catalyst that purifies the exhaust gas discharged from the exhaust member, and an EGR device that recirculates a portion of the exhaust gas to the intake member as EGR gas, and has a temperature adjustment unit that adjusts the temperature of the bi-fuel internal combustion engine and the exhaust gas discharged to the exhaust member based on the type of fuel used by the bi-fuel internal combustion engine and the operating state of the EGR device.

[0018] As a result, the cooling device for a bi-fuel vehicle according to one embodiment of the present invention can improve the fuel economy of the bi-fuel internal combustion engine while protecting the catalyst and activating the catalyst. [Example]

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A cooling device for a bi-fuel vehicle according to an embodiment of the present invention will now be described with reference to the drawings. (First Example)

[0020] 1 to 3 are diagrams showing a cooling device for a bi-fuel vehicle according to a first embodiment of the present invention.

[0021] First, the configuration will be described. In Figure 1, a bi-fuel vehicle 1 (hereinafter simply referred to as vehicle 1) is configured to include an engine 2 as a bi-fuel internal combustion engine, an ECU (Electronic Control Unit) 3 (see Figure 2), an EGR (Exhaust Gas Recirculation) device 10, and a cooling device 20.

[0022] The engine 2 is formed with a plurality of cylinders (not shown), and is configured to perform a series of four strokes for each cylinder, including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.

[0023] One of two types of fuel, liquid gasoline as a first fuel and compressed natural gas (hereinafter referred to as CNG) as a second fuel, is selected and supplied to the engine 2 as the fuel to be injected into the combustion chamber of each cylinder. Note that LPG (Liquefied Petroleum Gas) may also be used as the second fuel.

[0024] The engine 2 is equipped with a gasoline supply system that supplies gasoline stored in a gasoline tank 4 to the combustion chambers of the cylinders, and a gas fuel supply system that supplies CNG stored at high pressure in a gas fuel tank 5 to the combustion chambers of the cylinders.

[0025] The fuel switching device 6 switches the fuel to be injected into the combustion chamber of each cylinder of the engine 2. Under the control of the ECU 3, the fuel switching device 6 switches the fuel to be injected into the combustion chamber of each cylinder of the engine 2 between gasoline stored in the gasoline tank 4 and CNG stored in the gas fuel tank 5.

[0026] An intake manifold 7 is attached to the engine 2. The intake manifold 7 distributes and introduces intake air purified by an air cleaner (not shown) into each cylinder of the engine 2.

[0027] An exhaust manifold 8 is attached to the engine 2. The exhaust manifold 8 collects exhaust gas burned in the combustion chambers of the cylinders of the engine 2 and discharges it to an exhaust purification device 9. In this embodiment, the intake manifold 7 constitutes an intake member, and the exhaust manifold 8 constitutes an exhaust member.

[0028] The exhaust purification device 9 is configured by supporting a precious metal such as platinum or rhodium on a honeycomb-shaped alumina carrier, and is provided with a catalyst 9A that purifies harmful components such as HC, NOx, and CO.

[0029] The EGR device 10 includes an EGR pipe 11 , an EGR cooler 12 , and an EGR control valve 13 .

[0030] The upstream end of the EGR pipe 11 is connected to the exhaust purification device 9, and part of the exhaust gas is introduced as EGR gas from the exhaust purification device 9 into the EGR pipe 11. Here, upstream and downstream refer to the upstream and downstream with respect to the flow direction of intake air, EGR gas, exhaust gas, and cooling water, which will be described later.

[0031] The downstream end of the EGR pipe 11 is connected to the intake manifold 7. That is, with respect to the flow direction of the EGR gas, the intake manifold 7 is located downstream of the exhaust manifold 8, and the exhaust manifold 8 is located upstream of the intake manifold 7.

[0032] The EGR pipe 11 recirculates a portion of the exhaust gas discharged from the exhaust manifold 8 to the intake manifold 7 .

[0033] This reduces the oxygen concentration in the combustion chamber of the cylinder of engine 2, lowering the combustion temperature and suppressing the generation of NOx. In addition, since the throttle valve opening can be increased during intake, pumping loss can be reduced and the fuel efficiency of engine 2 can be improved.

[0034] The EGR cooler 12 cools the EGR gas by exchanging heat between the cooling water and the EGR gas.

[0035] This increases the density of the EGR gas, reducing the cooling loss of the engine 2 and improving the fuel efficiency of the engine 2. The EGR control valve 13 adjusts the flow rate of the EGR gas flowing through the EGR pipe 11. The upstream end of the EGR pipe 11 may be connected to the exhaust manifold 8.

[0036] The cooling device 20 includes a main cooling pipe 21, an exhaust gas cooling pipe 22, an EGR gas cooling pipe 23, a first flow control valve 24, a second flow control valve 25, a radiator 26, a water pump 27, and an ECU 3.

[0037] In this embodiment, the main cooling pipe 21 constitutes a main cooling water circulation section, the exhaust gas cooling pipe 22 constitutes an exhaust gas cooling water circulation section, and the EGR gas cooling pipe 23 constitutes an EGR gas cooling water circulation section.

[0038] The main cooling pipe 21, the exhaust gas cooling pipe 22, the EGR gas cooling pipe 23, the first flow control valve 24, the second flow control valve 25 and the ECU 3 constitute a temperature adjustment unit 40, and the ECU 3 constitutes a control unit.

[0039] The engine 2 is provided with a cooling water passage 2w that cools parts that become hot, such as the cylinders. A main cooling pipe 21 connects an inlet 2a and an outlet 2b of the cooling water passage 2w, and circulates the cooling water through the cooling water passage 2w of the engine 2. The main cooling water circulation unit is configured to include the cooling water passage 2w.

[0040] The EGR cooler 12 is attached to a main cooling pipe 21 , which circulates cooling water through the EGR cooler 12 .

[0041] The water pump 27 is provided in the engine 2 and is driven by the crankshaft of the engine 2 to circulate the cooling water through the main cooling pipe 21. The water pump 27 may be configured as an electric pump.

[0042] In the main cooling pipe 21, a radiator 26 is installed between the EGR cooler 12 and the inlet 2a of the cooling water passage 2w. The radiator 26 exchanges heat between the running wind and the cooling water flowing through the main cooling pipe 21, cools the engine 2 and EGR gas, and supplies the high-temperature cooling water to the engine 2.

[0043] A cooling water passage 8w through which cooling water flows is formed in the exhaust manifold 8. The exhaust gas cooling pipe 22 has an upstream pipe 22A that branches off from the main cooling pipe 21 and is connected to the inlet 8a of the cooling water passage 8w, and a downstream pipe 22B that connects the outlet 8b of the cooling water passage 8w to the main cooling pipe 21 downstream of the outlet 2b of the cooling water passage 2w of the engine 2. The exhaust gas cooling water circulation section is configured to include the cooling water passage 8w.

[0044] The exhaust gas cooling pipe 22 supplies cooling water cooled by the radiator 26 to the exhaust manifold 8 to cool the high-temperature exhaust gas discharged from the cylinders of the engine 2 .

[0045] The EGR gas cooling pipe 23 branches off from the main cooling pipe 21 and is connected to the main cooling pipe 21 downstream of the outlet 2 b of the cooling water passage 2 w of the engine 2 .

[0046] The EGR gas cooling pipe 23 cools the EGR gas by directly supplying the cooling water cooled by the radiator 26 to the EGR cooler 12. That is, the EGR gas cooling pipe 23 supplies the cooling water cooled by the radiator 26 to the EGR cooler 12 while maintaining the temperature of the cooling water.

[0047] In addition, the exhaust gas cooling pipe 22 and the EGR gas cooling pipe 23 are connected to the main cooling pipe 21, and the cooling water flowing through the exhaust gas cooling pipe 22 and the EGR gas cooling pipe 23 is merged with the cooling water flowing through the main cooling pipe 21 and supplied to the EGR cooler 12.

[0048] The first flow control valve 24 is installed in the upstream pipe 22A upstream of the inlet 8a of the cooling water passage 8w of the exhaust manifold 8, and adjusts the flow rate of the cooling water flowing through the upstream pipe 22A, thereby adjusting the flow rate of the cooling water flowing through the cooling water passage 8w.

[0049] The second flow control valve 25 is installed in the EGR gas cooling pipe 23 upstream of the EGR cooler 12, and adjusts the flow rate of the cooling water flowing through the EGR gas cooling pipe 23, thereby adjusting the flow rate of the cooling water flowing through the EGR cooler 12.

[0050] The ECU 3 is composed of a computer unit equipped with a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), flash memory for storing backup data, input ports, and output ports.

[0051] The ROM of this computer unit stores various constants, various maps, and the like, as well as a program for causing the computer unit to function as the ECU 3.

[0052] That is, the CPU executes the program stored in the ROM using the RAM as a work area, and this computer unit functions as the ECU 3 in this embodiment.

[0053] An input port of the ECU 3 receives a fuel use signal P1 from a fuel use selection switch 41 and an operating state signal P2 from an operating state detection unit .

[0054] An output port of the ECU 3 is connected to the EGR control valve 13 , a first flow control valve 24 , and a second flow control valve 25 .

[0055] The fuel selection switch 41 receives an operation from the driver and outputs a signal to select either gasoline or CNG as the fuel to be injected into the combustion chamber of each cylinder of the engine 2. In accordance with the signal from the fuel selection switch 41, the ECU 3 controls the fuel switching device 6 to switch the fuel to be injected into the combustion chamber of each cylinder of the engine 2, and outputs a fuel selection signal P1 to the ECU 3 according to the selected fuel.

[0056] The operating state signal P2 is output information from an operating state detection unit 42, which is composed of, for example, a rotation speed sensor that detects the rotation speed of the engine 2 and an accelerator pedal position sensor that detects the position of the accelerator pedal, and the fuel used signal P1 and the operating state signal P2 are signals that correspond to the operating state of the engine 2.

[0057] The ECU 3 adjusts the opening of the EGR control valve 13 in accordance with the operating state of the engine 2 , and adjusts the flow rate of the EGR gas recirculated from the exhaust purification device 9 through the EGR pipe 11 to the intake manifold 7 .

[0058] The flow rate of this EGR gas is set according to an EGR map pre-stored in the ROM of the ECU 3. The EGR map determines the EGR amount using engine speed and accelerator opening as parameters, and is experimentally obtained and stored in the ROM in advance.

[0059] That is, the ECU 3 controls and detects the opening degree of the EGR control valve 13 based on the detection signal of the operating state detection unit 42 and the EGR map.

[0060] An EGR control valve opening sensor may be provided to detect the opening of the EGR control valve 13, and the ECU 3 may detect the opening of the EGR control valve 13 based on detection information from the EGR control valve opening sensor.

[0061] The ECU 3 adjusts the flow rate of the cooling water flowing through the exhaust gas cooling pipe 22 and the EGR gas cooling pipe 23 by controlling the first flow control valve 24 and the second flow control valve 25 based on the fuel use signal P1 and the operating state signal P2 from the fuel use selection switch 41, i.e., based on the type of fuel used in the engine 2 and the opening degree of the EGR control valve 13.

[0062] Specifically, the ECU 3 increases the opening degree of the second flow control valve 25 relatively to the opening degree of the first flow control valve 24, provided that the engine 2 uses CNG and the opening degree of the EGR control valve 13 exceeds a predetermined value.

[0063] In addition, the ECU 3 increases the opening degree of the first flow control valve 24 relatively to the opening degree of the second flow control valve 25, on the condition that the engine 2 is not using CNG, or that the engine 2 is using CNG and the opening degree of the EGR control valve 13 is equal to or less than a predetermined value.

[0064] Next, the flow of cooling control of the vehicle 1 will be described with reference to the flowchart of Fig. 3. The following control content is repeatedly executed at predetermined intervals while the engine 2 is operating.

[0065] In step S1, the ECU 3 acquires the operating conditions based on the fuel to be used signal P1 from the fuel to be used selection switch 41 and the operating state signal P2.

[0066] That is, the ECU 3 detects the type of fuel used by the engine 2 based on the fuel use signal P1, and detects the opening degree of the EGR control valve 13 based on the operating state signal P2.

[0067] Next, the ECU 3 determines whether the fuel used by the engine 2 is CNG (step S2), and if it determines that the fuel used is CNG, it determines whether the opening of the EGR control valve 13 exceeds a predetermined value (step S3).

[0068] In this embodiment, the predetermined value is 0 (zero), and when the opening degree of the EGR control valve 13 is 0, the EGR control valve 13 is in a completely closed state (fully closed state).

[0069] In step S3, if the ECU 3 determines that the EGR control valve 13 exceeds the predetermined value, it closes the first flow control valve 24 and opens the second flow control valve 25 (step S4).

[0070] That is, in an operating state in which CNG fuel is used and EGR gas is supplied to the intake manifold 7, the first flow control valve 24 is closed and the second flow control valve 25 is opened.

[0071] As a result, cooling water does not flow through the exhaust gas cooling pipe 22, but flows through the engine 2 and EGR gas cooling pipe 23 (see arrows A and C in Figure 1), and the cooling water that has cooled the engine 2 is combined with the cooling water that has bypassed the engine 2 and exhaust manifold 8 and circulates through the EGR cooler 12, and the EGR gas is cooled by the cooling water.

[0072] Therefore, when the engine 2 is driven by CNG, which has a lower combustion temperature than gasoline, the exhaust gas from the combustion of the CNG can be prevented from being cooled in the exhaust manifold 8 by the cooling water, and the exhaust gas can be prevented from being overcooled, causing the temperature of the catalyst 9A to fall below its activation temperature.

[0073] In addition, in the past, it was considered to reduce the amount of EGR gas introduced into the intake side to prevent the exhaust gas from being overcooled, but the cooling device 20 of this embodiment does not cool the exhaust gas with cooling water, so it is possible to flow a large amount of EGR gas into the EGR device 10 and circulate low-temperature cooling water cooled in the radiator 26 to the EGR cooler 12 via the EGR gas cooling piping 23.

[0074] This allows a large amount of EGR gas to be cooled efficiently and the density of the EGR gas to be increased, which in turn allows the oxygen concentration in the combustion chamber of the engine 2 to be more effectively reduced, thereby more effectively lowering the combustion temperature and more effectively suppressing the generation of NOx.

[0075] In addition, the opening of the throttle valve can be increased during intake, reducing pumping loss and improving the fuel efficiency of engine 2.

[0076] Furthermore, since the combustion of CNG causes the engine 2 to be at a lower temperature than when gasoline is burned, if cooling water is not supplied to the exhaust manifold 8, cooling water cooled by the radiator 26 will be supplied to the engine 2 to the extent that cooling water is not supplied to the exhaust manifold 8, and there is a risk that the engine 2 will become overcooled.

[0077] The cooling device 20 of this embodiment can circulate the coolant cooled by the radiator 26 to the EGR gas cooling pipe 23, bypassing the engine 2 and the exhaust manifold 8, thereby preventing overcooling of the engine 2. This reduces the cooling loss of the engine 2, and more effectively improves the fuel efficiency of the engine 2.

[0078] On the other hand, if it is determined in step S2 that CNG is not being used, i.e., that gasoline is being used, the first flow control valve 24 is opened and the second flow control valve 25 is closed (step S5).

[0079] That is, in an operating state in which CNG fuel is not used, the first flow control valve 24 is opened and the second flow control valve 25 is closed. In this operating state, the ECU 3 adjusts the opening of the EGR control valve 13 in accordance with the operating state of the engine 2, and adjusts the flow rate of EGR gas recirculated from the exhaust purification device 9 through the EGR pipe 11 to the intake manifold 7.

[0080] As a result, cooling water does not flow through the EGR gas cooling pipe 23, but flows through the engine 2 and exhaust gas cooling pipe 22 (see arrows A and B in Figure 1), and after the cooling water cools the engine 2 and exhaust gas, it can cool the EGR gas.

[0081] Therefore, when the engine 2 is driven by gasoline, which has a higher combustion temperature than CNG, the high-temperature exhaust gas produced by the combustion of the gasoline can be cooled by the cooling water in the exhaust manifold 8. As a result, the catalyst 9A can be protected from the high-temperature exhaust gas, and the temperature of the catalyst 9A can be maintained at its activation temperature.

[0082] Furthermore, since cooling water can be supplied from the main cooling pipe 21 and the exhaust gas cooling pipe 22 to the EGR cooler 12 to cool the EGR gas, the density of the EGR gas can be increased, the cooling loss of the engine 2 can be reduced, and the fuel efficiency of the engine 2 can be improved.

[0083] Furthermore, in step S3, if the ECU 3 determines that the opening degree of the EGR control valve 13 is zero when the engine 2 is driven by CNG, the ECU 3 executes the process of step S5.

[0084] Therefore, even when the exhaust gas is cooled by the cooling water circulating through the exhaust gas cooling pipe 22, the amount of EGR gas introduced into the intake side can be eliminated, thereby preventing the exhaust gas from being overcooled and the temperature of the catalyst 9A from falling below the activation temperature.

[0085] The predetermined value is not limited to 0, but may be, for example, an opening in the range of 0.1% to 1%.

[0086] Thus, the vehicle 1 of this embodiment has an engine 2 that can use gasoline and CNG, an intake manifold 7 that is provided on the engine 2 and introduces intake air into the engine 2, and an exhaust manifold 8 that is provided on the engine 2 and discharges exhaust gas from the engine 2.

[0087] In addition, the vehicle 1 is equipped with an exhaust purification device 9 that is installed downstream of the exhaust manifold 8 and has a catalyst 9A that purifies the exhaust gas discharged from the exhaust manifold 8, and an EGR device 10 that recirculates a portion of the exhaust gas to the intake manifold 7 as EGR gas.

[0088] In addition, the cooling device of the vehicle 1 in this embodiment has a temperature adjustment unit 40 that adjusts the temperature of the engine 2 and the temperature of the exhaust gas emitted from the engine 2 based on the type of fuel used by the engine 2 and the operating state of the EGR device 10.

[0089] As a result, when the engine 2 is driven by gasoline, the exhaust gas is cooled by the cooling water, and the catalyst 9A of the exhaust purification device 9 is protected and activated.

[0090] Furthermore, when the engine 2 is driven by CNG, the exhaust gas can be prevented from being overcooled, and more EGR gas can be recirculated to the intake manifold 7, improving the fuel efficiency of the engine 2. In other words, the EGR device 10 can be used to the fullest extent.

[0091] Furthermore, when the engine 2 is driven by CNG, it is possible to prevent an excessive supply of cooling water to the engine 2, thereby preventing the engine 2 from being overcooled. This reduces the cooling loss of the engine 2, and more effectively improves the fuel efficiency of the engine 2.

[0092] In this way, the cooling device for the vehicle 1 of this embodiment can improve the fuel efficiency of the engine 2 while protecting the catalyst 9A and activating the catalyst 9A.

[0093] Furthermore, according to the cooling device of the vehicle 1 of this embodiment, the temperature adjustment unit 40 has a main cooling pipe 21 that circulates cooling water to the engine 2, an exhaust gas cooling pipe 22 that branches off from the main cooling pipe 21 and circulates cooling water to the exhaust manifold 8, and an EGR gas cooling pipe 23 that branches off from the main cooling pipe 21 and circulates cooling water to the EGR device 10, bypassing the engine 2 and the exhaust manifold 8.

[0094] In addition, the temperature adjusting unit 40 adjusts the flow rate of the cooling water flowing through the exhaust gas cooling pipe 22 and the EGR gas cooling pipe 23 based on the type of fuel used by the engine 2 and the operating state of the EGR device 10.

[0095] As a result, when the engine 2 is driven by gasoline, cooling water is circulated through the exhaust gas cooling pipe 22 to cool the exhaust gas, thereby protecting the catalyst 9A of the exhaust purification device 9 and activating the catalyst 9A.

[0096] Furthermore, when the engine 2 is driven by CNG, the exhaust gas can be prevented from being overcooled by not flowing cooling water through the exhaust gas cooling pipe 22. This allows a larger amount of EGR gas to be recirculated to the intake manifold 7, improving the fuel efficiency of the engine 2. In other words, the EGR device 10 can be used to the fullest extent.

[0097] Furthermore, when the engine 2 is driven by CNG, even if cooling water is not flowed through the exhaust gas cooling pipe 22, by circulating the cooling water through the EGR gas cooling pipe 23, it is possible to prevent excessive supply of cooling water to the engine 2 and prevent the engine 2 from being overcooled. This reduces the cooling loss of the engine 2 and more effectively improves the fuel efficiency of the engine 2.

[0098] Furthermore, according to the cooling device of the vehicle 1 of this embodiment, the temperature adjustment unit 40 has a first flow control valve 24 provided in the exhaust gas cooling pipe 22 to adjust the flow rate of the cooling water supplied to the exhaust manifold 8, and a second flow control valve 25 provided in the EGR gas cooling pipe 23 to adjust the flow rate of the cooling water supplied to the EGR device 10.

[0099] This allows the first flow control valve 24 and the second flow control valve 25 to easily adjust the flow rate of the cooling water circulating through the main cooling pipe 21, the exhaust gas cooling pipe 22, and the EGR gas cooling pipe 23, thereby protecting the catalyst 9A and activating it, while more effectively improving the fuel efficiency of the engine 2.

[0100] Furthermore, according to the cooling device of the vehicle 1 of this embodiment, the EGR device 10 includes an EGR pipe 11 that recirculates exhaust gas to the intake manifold 7, an EGR control valve 13 that is provided in the EGR pipe 11 and that adjusts the flow rate of EGR gas flowing through the EGR pipe 11, and an EGR cooler 12 that cools the EGR gas flowing through the EGR pipe 11.

[0101] The cooling device 20 includes an ECU 3, which controls a first flow control valve 24 and a second flow control valve 25 based on the type of fuel supplied to the engine 2 and the opening degree of the EGR control valve 13.

[0102] As a result, when the engine 2 is driven by gasoline, the ECU 3 opens the first flow control valve 24 to circulate cooling water through the exhaust gas cooling pipe 22 to cool the exhaust gas, thereby protecting the catalyst 9A of the exhaust purification device 9 and activating the catalyst 9A.

[0103] Furthermore, when the engine 2 is driven by CNG, the ECU 3 closes the first flow control valve 24 to prevent cooling water from flowing through the exhaust gas cooling pipe 22, thereby preventing the exhaust gas from being overcooled. This allows a larger amount of EGR gas to be recirculated to the intake manifold 7, improving the fuel efficiency of the engine 2. In other words, the EGR device 10 can be used to the fullest extent.

[0104] Furthermore, when the engine 2 is driven by CNG, even if cooling water is not flowed through the exhaust gas cooling pipe 22, by circulating the cooling water through the EGR gas cooling pipe 23, it is possible to prevent excessive supply of cooling water to the engine 2 and prevent the engine 2 from being overcooled.

[0105] This reduces the cooling loss of the engine 2, and improves the fuel efficiency of the engine 2 more effectively.

[0106] Furthermore, according to the cooling device for the vehicle 1 of this embodiment, the ECU 3 closes the first flow control valve 24 and opens the second flow control valve 25 on the condition that the engine 2 uses CNG and the opening degree of the EGR control valve 13 exceeds zero.

[0107] This prevents the exhaust gas from the combustion of CNG from being cooled in the exhaust manifold 8 by the cooling water when the engine 2 is driven by CNG, which has a lower combustion temperature than gasoline, and prevents the exhaust gas from becoming overcooled and causing the temperature of the catalyst 9A to fall below its activation temperature.

[0108] Furthermore, instead of cooling the exhaust gas with cooling water, low-temperature cooling water cooled by the radiator 26 can be circulated through the EGR gas cooling pipe 23 to the EGR cooler 12. This allows the EGR gas to be cooled efficiently, increasing the density of the EGR gas and improving the fuel efficiency of the engine 2.

[0109] In addition, the cooling water cooled by the radiator 26 can be circulated to the EGR gas cooling pipe 23, bypassing the engine 2 and the exhaust manifold 8, thereby preventing overcooling of the engine 2. This reduces the cooling loss of the engine 2, and more effectively improves the fuel efficiency of the engine 2.

[0110] Furthermore, according to the cooling device for the vehicle 1 of this embodiment, the ECU 3 opens the first flow control valve 24 and closes the second flow control valve 25 on the condition that the engine 2 does not use CNG, or that the engine 2 uses CNG and the opening degree of the EGR control valve 13 is zero.

[0111] As a result, when the engine 2 is driven by gasoline, which has a higher combustion temperature than CNG, the high-temperature exhaust gas produced by the combustion of gasoline can be cooled by the cooling water in the exhaust manifold 8. This makes it possible to protect the catalyst 9A from the high-temperature exhaust gas and maintain the temperature of the catalyst 9A at its activation temperature.

[0112] Furthermore, since cooling water can be supplied from the main cooling pipe 21 and the exhaust gas cooling pipe 22 to the EGR cooler 12 to cool the EGR gas, the density of the EGR gas can be increased, the cooling loss of the engine 2 can be reduced, and the fuel efficiency of the engine 2 can be improved.

[0113] Furthermore, when the engine 2 is driven by CNG and the opening of the EGR control valve 13 is zero, the first flow control valve 24 is opened and the second flow control valve 25 is closed. Therefore, even if the exhaust gas is cooled with cooling water, the cooling caused by the introduction of EGR gas to the intake side is suppressed, thereby preventing excessive cooling.

[0114] This makes it possible to prevent the exhaust gas from being overcooled, and to prevent the temperature of the catalyst 9A from falling below its activation temperature.

[0115] Furthermore, according to the cooling device of the vehicle 1 of this embodiment, the exhaust gas cooling pipe 22 and the EGR gas cooling pipe 23 introduce cooling water into the EGR cooler 12, so that the EGR gas can be cooled more effectively, the density of the EGR gas can be increased more effectively, and the fuel efficiency of the engine 2 can be improved more effectively.

[0116] Furthermore, according to the cooling device for the vehicle 1 of this embodiment, different fuels are switched between gasoline and CNG and supplied to the engine 2.

[0117] Compared to gasoline, CNG has better fuel efficiency and emits fewer harmful substances in its exhaust gases, so in addition to improving fuel efficiency by reducing gasoline consumption, it can also improve exhaust gas performance.

[0118] (Second Example) Fig. 4 is a diagram showing a cooling device for a bi-fuel vehicle according to a second embodiment of the present invention, in which the same components as those in the first embodiment are given the same reference numerals and their explanations are omitted. Note that Fig. 3 is used as a system configuration diagram.

[0119] In FIG. 4, a cooling water passage 2w of the engine 2 and a cooling water passage 8w of the exhaust manifold 8 are in communication with each other, and cooling water can flow through the cooling water passage 2w and the cooling water passage 8w.

[0120] The vehicle 1 is provided with a cooling system 50, which includes a main cooling pipe 51, an exhaust gas cooling pipe 52, an EGR gas cooling pipe 53, bypass pipes 54 and 55, a thermostat 56, a heater core 57, a first flow control valve 24, a second flow control valve 25, a radiator 26, a water pump 27, and an ECU 3 (see FIG. 2).

[0121] In this embodiment, the main cooling pipe 51 constitutes a main cooling water circulation section, the exhaust gas cooling pipe 52 constitutes an exhaust gas cooling water circulation section, and the EGR gas cooling pipe 53 constitutes an EGR gas cooling water circulation section. The main cooling water circulation section is configured to include a cooling water passage 2w, and the exhaust gas cooling water circulation section is configured to include a cooling water passage 8w.

[0122] The main cooling pipe 51 , the exhaust gas cooling pipe 52 , the EGR gas cooling pipe 53 , the first flow control valve 24 , the second flow control valve 25 and the ECU 3 constitute a temperature adjustment unit 60 .

[0123] The main cooling pipe 51 connects the inlet 2a and outlet 2b of the cooling water passage 2w, and circulates the cooling water through the cooling water passage 2w of the engine 2.

[0124] The EGR cooler 12 is attached to a main cooling pipe 51 , which circulates cooling water through the EGR cooler 12 .

[0125] In the main cooling pipe 51, a radiator 26 is installed between the EGR cooler 12 and the inlet 2a of the cooling water passage 2w.

[0126] The exhaust gas cooling pipe 52 connects the outlet 8b of the cooling water passage 8w to the main cooling pipe 51 downstream of the outlet 2b of the cooling water passage 2w of the engine 2, and the cooling water flowing through the cooling water passage 8w is introduced into the exhaust gas cooling pipe 52.

[0127] That is, the cooling water passage 8w constituting the exhaust gas cooling water circulation part is branched off from the cooling water passage 2w constituting the main cooling water circulation part, and the cooling water passage 8w and the exhaust gas cooling pipe 52 circulate the cooling water cooled by the radiator 26 to the exhaust manifold 8. In this way, the exhaust gas discharged from the cylinders of the engine 2 is cooled.

[0128] The EGR gas cooling pipe 53 branches off from the main cooling pipe 51, and its upstream end is connected to the main cooling pipe 51 upstream of the inlet 2a of the cooling water passage 2w of the engine 2, and its downstream end is connected to the main cooling pipe 51 upstream of the EGR cooler 12.

[0129] The EGR gas cooling pipe 53 cools the EGR gas by supplying the cooling water, which has been cooled by the radiator 26 and circulated through the EGR cooler 12, to the EGR cooler 12.

[0130] In addition, the exhaust gas cooling pipe 52 and the EGR gas cooling pipe 53 are connected to the main cooling pipe 51, and the cooling water flowing through the exhaust gas cooling pipe 52 and the EGR gas cooling pipe 53 is merged with the cooling water flowing through the main cooling pipe 51 and supplied to the EGR cooler 12.

[0131] The thermostat 56 is attached to the outlet 2b of the cooling water passage 2w of the engine 2. When the temperature of the cooling water exceeds a predetermined temperature, the thermostat 56 circulates the cooling water through the main cooling pipe 51 while cooling the cooling water using the radiator 26.

[0132] The upstream end of the bypass pipe 54 is connected to a thermostat 56 , and the downstream end of the bypass pipe 54 is connected to the main cooling pipe 51 downstream of the radiator 26 and upstream of the EGR cooler 12 .

[0133] The upstream end of the bypass pipe 55 branches off from the bypass pipe 54, and the downstream end of the bypass pipe 55 is connected to the main cooling pipe 51 downstream of the EGR cooler 12. The heater core 57 is installed in the bypass pipe 55. The heater core 57 exchanges heat with air for air conditioning (outside air or air inside the vehicle cabin) that has a lower temperature than the coolant.

[0134] When the coolant temperature drops below a predetermined value, the thermostat 56 circulates the coolant through the bypass pipes 54 and 55, bypassing the radiator 26, thereby raising the temperature of the coolant, thereby accelerating the warming up of the engine 2.

[0135] The heater core 57 exchanges heat between the coolant heated by the engine 2 and air sent in by a fan (not shown). During heating, the air sent in by the fan is heated by the heater core 57 and sent into the vehicle interior through an air outlet (not shown).

[0136] The first flow control valve 24 is installed inside the engine 2, and adjusts the flow rate of the cooling water flowing through the cooling water passage 2w, thereby adjusting the flow rate of the cooling water flowing through the cooling water passage of the exhaust manifold 8. The first flow control valve 24 may also be installed in the exhaust manifold 8.

[0137] According to the cooling device 50 of the vehicle 1 having such a configuration, when CNG fuel is used and EGR gas is supplied to the intake manifold 7, the first flow control valve 24 is closed and the second flow control valve 25 is opened.

[0138] The first flow control valve 24 is a flow control valve with a check valve, and when the first flow control valve 24 is opened, the cooling water flows from the downstream side of the water pump 27 to the upstream side of the EGR cooler 12, but the cooling water does not flow from the upstream side of the EGR cooler 12 to the downstream side of the water pump 27.

[0139] As a result, cooling water does not flow through the exhaust gas cooling pipe 52, but flows through the engine 2 and EGR gas cooling pipe 53 (see arrows E and F in Figure 4), and the cooling water that has cooled the engine 2 is combined with the cooling water that has bypassed the engine 2 and exhaust manifold 8 and circulates through the EGR cooler 12, and the EGR gas is cooled by the cooling water.

[0140] Therefore, when the engine 2 is driven by CNG, which has a lower combustion temperature than gasoline, the exhaust gas from the combustion of the CNG is prevented from being cooled in the exhaust manifold 8 by the cooling water, and the exhaust gas is prevented from becoming overcooled, causing the temperature of the catalyst 9A to fall below its activation temperature.

[0141] Furthermore, the exhaust gas is not cooled by cooling water, but low-temperature cooling water cooled by the radiator 26 can be circulated to the EGR cooler 12 by the EGR gas cooling pipe 53 .

[0142] This allows the EGR gas to be cooled efficiently and the density of the EGR gas to be increased, which in turn allows the oxygen concentration in the combustion chamber of the engine 2 to be more effectively reduced, thereby more effectively lowering the combustion temperature and more effectively suppressing the generation of NOx.

[0143] In addition, the opening of the throttle valve can be increased during intake, reducing pumping loss and improving the fuel efficiency of engine 2.

[0144] Furthermore, the cooling water cooled by the radiator 26 can be circulated to the EGR gas cooling pipe 53, bypassing the engine 2 and the exhaust manifold 8, thereby preventing overcooling of the engine 2. This reduces the cooling loss of the engine 2, and more effectively improves the fuel efficiency of the engine 2.

[0145] On the other hand, in an operating state in which gasoline is used, that is, in an operating state in which CNG fuel is not used, the first flow control valve 24 is opened and the second flow control valve 25 is closed.

[0146] As a result, cooling water does not flow through the EGR gas cooling pipe 53, but flows through the engine 2 and exhaust gas cooling pipe 52 (see arrows E and G in Figure 4), and after the engine 2 and exhaust gas are cooled by the cooling water, the EGR gas is cooled.

[0147] Therefore, when the engine 2 is driven by gasoline, which has a higher combustion temperature than CNG, the high-temperature exhaust gas produced by the combustion of the gasoline can be cooled by the cooling water in the exhaust manifold 8. This makes it possible to protect the catalyst 9A from the high-temperature exhaust gas and maintain the temperature of the catalyst 9A at its activation temperature.

[0148] Furthermore, the cooling water flowing through the exhaust gas cooling pipe 52 is merged with the main cooling pipe 51 and cooled by the radiator 26, and then the low-temperature cooling water is supplied to the EGR cooler 12 to cool the EGR gas. This increases the density of the EGR gas, reduces the cooling loss of the engine 2, and improves the fuel efficiency of the engine 2.

[0149] Furthermore, when the engine 2 is driven by CNG and the opening degree of the EGR control valve 13 is zero, the ECU 3 opens the first flow control valve 24 and closes the second flow control valve 25. Therefore, even if the exhaust gas is cooled by the cooling water circulating through the exhaust gas cooling pipe 52, the cooling caused by the introduction of EGR gas to the intake side is suppressed, and excessive cooling can be prevented. This prevents the exhaust gas from being overcooled, and the temperature of the catalyst 9A from falling below the activation temperature.

[0150] While an embodiment of the present invention has been disclosed, it will be apparent to one skilled in the art that modifications may be made thereto without departing from the scope of the present invention, and it is intended that all such modifications and equivalents be included in the following claims. [Explanation of symbols]

[0151] 1...vehicle (bi-fuel vehicle), 2...engine (bi-fuel internal combustion engine), 2w...cooling water passage (main cooling water circulation section), 3...ECU (temperature adjustment section, control section), 7...intake manifold (intake member), 8...exhaust manifold (exhaust member), 8w...cooling water passage (exhaust gas cooling water circulation section), 9...exhaust gas purification device, 9A...catalyst, 10...EGR device, 11...EGR piping, 12...EGR cooler, 13...EGR control valve, 21, 51...main cooling pipe (main cooling water circulation section, temperature adjustment section), 22, 52...exhaust gas cooling pipe (exhaust gas cooling water circulation section, temperature adjustment section), 23, 53...EGR gas cooling pipe (EGR gas cooling water circulation section, temperature adjustment section), 24...first flow control valve (EGR cooling water circulation section), 25...second flow control valve (EGR cooling water circulation section), 40, 60...temperature adjustment section

Claims

1. a bi-fuel internal combustion engine capable of using a first fuel and a second fuel having a lower combustion temperature than the first fuel; an intake member provided in the bi-fuel internal combustion engine for introducing intake air into the bi-fuel internal combustion engine; an exhaust member provided in the bi-fuel internal combustion engine through which exhaust gas is discharged from the bi-fuel internal combustion engine; an exhaust purification device that is installed downstream of the exhaust member and has a catalyst that purifies exhaust gas discharged from the exhaust member; an EGR device that recirculates a portion of exhaust gas to the intake member as EGR gas, a temperature adjusting unit that adjusts the temperature of the exhaust gas discharged into the bi-fuel internal combustion engine and the exhaust member based on the type of fuel used by the bi-fuel internal combustion engine and the operating state of the EGR device, The temperature adjustment unit is a main cooling water circulation passage portion for circulating cooling water in the bi-fuel internal combustion engine; an exhaust cooling water circulation passage portion branching from the main cooling water circulation passage portion and circulating cooling water through the exhaust member; an EGR cooling water circulation passage portion branching from the main cooling water circulation passage portion, bypassing the bi-fuel internal combustion engine and the exhaust member, and circulating cooling water to the EGR device; a first flow control valve provided in the exhaust cooling water circulation passage portion and configured to adjust the flow rate of the cooling water supplied to the exhaust member; a second flow control valve provided in the EGR cooling water circulation passage portion and configured to adjust the flow rate of the cooling water supplied to the EGR device; a flow rate of the cooling water flowing through the exhaust cooling water circulation passage portion and the EGR cooling water circulation passage portion is adjusted based on the type of fuel used by the bi-fuel internal combustion engine and the operating state of the EGR device, The EGR device is an EGR gas cooling pipe that recirculates exhaust gas to the intake member; an EGR control valve that is provided in the EGR gas cooling pipe and that adjusts the flow rate of EGR gas flowing through the EGR gas cooling pipe; and an EGR cooler that cools the EGR gas flowing through the EGR gas cooling pipe, The temperature adjustment unit is a control unit that controls the first flow control valve and the second flow control valve based on the type of fuel supplied to the bi-fuel internal combustion engine and the opening degree of the EGR control valve, The control unit On the condition that the bi-fuel internal combustion engine uses the second fuel and the opening degree of the EGR control valve exceeds a predetermined value, the opening degree of the second flow control valve is made relatively large compared to the opening degree of the first flow control valve, A cooling device for a bi-fuel vehicle, characterized in that the opening of the first flow control valve is made larger relative to the opening of the second flow control valve, under the condition that the bi-fuel internal combustion engine is not using the second fuel, or the bi-fuel internal combustion engine is using the second fuel and the opening of the EGR control valve is not more than a predetermined value.

2. A cooling device for a bi-fuel vehicle as described in Claim 1, characterized in that the exhaust cooling water circulation passage section and the EGR cooling water circulation passage section introduce cooling water into the EGR cooler.

3. A cooling device for a bi-fuel vehicle as described in claim 1 or claim 2, characterized in that the first fuel is gasoline and the second fuel is compressed natural gas.

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