Engine

Abstract

To provide an engine capable of suppressing generation of particulate matters by sufficiently vaporizing fuel adhered to a cylinder liner immediately after start of the engine.SOLUTION: An engine 100 includes a cylinder block 10 having a cylinder wall 12 and a cylinder liner 14. The engine 100 further includes a heater having an induction coil 42 disposed in a water jacket 20 extending along the cylinder wall 12. The heater heats the cylinder wall 12 by causing the cylinder wall 12 to generate an eddy current by using an AC current flowing in the induction coil 42.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an engine.

Background Art

[0002] The engine described in Patent Document 1 includes a cylinder block having a gas jacket. The gas jacket extends along the cylinder wall within the cylinder block. An exhaust passage is connected to the gas jacket via an exhaust gas supply valve. The gas jacket is connected to an intake passage via an exhaust gas discharge passage.

[0003] By opening the exhaust gas supply valve during operation of the engine, exhaust gas flows through the gas jacket. Thereby, the cylinder wall can be heated. By heating the cylinder wall, the cylinder liner located inside the cylinder wall can be heated. Thereby, the temperature of the lubricating oil between the cylinder liner and the piston can be raised to a desired temperature. Thereby, since the viscosity of the lubricating oil decreases, the frictional loss between the cylinder liner and the piston can be suppressed. Thereby, the fuel efficiency can be improved.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Immediately after the engine starts, the temperature of the exhaust gas is low. Immediately after the engine starts, fuel sprayed from the injector and not vaporized may adhere to the cylinder liner. If the air-fuel mixture is ignited when the fuel is not sufficiently vaporized, particulate matter (PM) may be generated. Therefore, it is conceivable to suppress the generation of PM by sufficiently vaporizing the fuel by heating the cylinder liner.

[0006] The technology described in the above patent document heats the cylinder liner using exhaust gas on the premise that the temperature of the exhaust gas is sufficiently high. Therefore, it is difficult to suppress the generation of PM immediately after the engine starts.

Means for Solving the Problem

[0007] Hereinafter, means for solving the above problems and their effects will be described. According to one aspect of the present disclosure, there is provided an engine including: a cylinder block having a cylinder wall and a cylinder liner located inside the cylinder wall and continuous with the cylinder wall; and a heater disposed in a water jacket extending along the cylinder wall in the cylinder block and having an induction coil extending along the cylinder wall, the heater being configured to heat the cylinder wall by generating eddy currents in the cylinder wall by an alternating current flowing through the induction coil.

[0008] According to the above configuration, the cylinder wall can be heated by generating eddy currents in the cylinder wall using the induction coil regardless of whether the engine has just started. Thereby, the cylinder liner can be heated. Thereby, the fuel adhering to the cylinder liner can be sufficiently vaporized, so that the generation of PM can be suppressed even immediately after the engine starts.

[0009] In the above engine, while the cylinder wall and the cylinder liner are entirely formed of an iron material, the cylinder block may be formed of an aluminum material except for the cylinder wall and the cylinder liner.

[0010] Generally, it is known that a cylinder block is formed of an aluminum material for the purpose of weight reduction. Also, generally, it is known that a cylinder liner is formed of an iron material for the purpose of ensuring durability.

[0011] In contrast, in the above configuration, while the cylinder wall and the cylinder liner are entirely formed of an iron material, the cylinder block is formed of an aluminum material except for the cylinder wall and the cylinder liner. Different from the above configuration, a comparative example where the cylinder wall is formed of an aluminum material can be considered.

[0012] Assume a case where an induction coil applies an alternating magnetic field having a given frequency to the cylinder wall. The magnitude of the eddy current flowing when the cylinder wall is formed of an aluminum material is the same as the magnitude of the eddy current flowing when the cylinder wall is formed of an iron material. The magnitude of the eddy current increases in direct proportion to the frequency of the alternating magnetic field.

[0013] The volume resistivity of the iron material is about four times that of the aluminum material. Therefore, in order to generate the same amount of Joule heat as in the above configuration, it is necessary to increase the frequency by about four times in the comparative example. In the above configuration, the cylinder wall can be induction heated by flowing an alternating current with a relatively low frequency through the induction coil. Therefore, according to the above configuration, a heater that generates a high-frequency alternating current, which is costly, becomes unnecessary. Thus, according to the above configuration, the cost required for the heater can be reduced.

[0014] In the above engine, the cylinder wall and the cylinder liner constitute the cylinder, the cylinder is one of a plurality of cylinders of the cylinder block, the plurality of cylinders are arranged in a row, and the plurality of central axes of the plurality of cylinders are on one cross-section of the cylinder block. The water jacket is composed of a first flow path located on a first side with respect to the cross-section and a second flow path located on a second side with respect to the cross-section. The first side and the second side are opposite to each other across the cross-section, and each of the first flow path and the second flow path extends across the plurality of cylinders. The induction coil may be disposed in the second flow path.

[0015] In the above engine, a plurality of injectors configured to inject fuel into the plurality of cylinders are provided, and each of the plurality of injectors may face the second side.

[0016] According to the above configuration, it becomes easier to heat the portion of the cylinder liner where fuel is likely to adhere. Therefore, it becomes easier to sufficiently vaporize the fuel adhering to the cylinder liner. As a result, it becomes easier to suppress the generation of PM.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0018] (First Embodiment) Hereinafter, the engine according to the first embodiment will be described with reference to the drawings. <Overview of Engine 100> As shown in FIG. 1, the engine 100 includes a cylinder block 10. The cylinder block 10 has a plurality of cylinders 16. Each of the plurality of cylinders 16 is composed of a cylinder wall 12 and a cylinder liner 14 located inside the cylinder wall 12 and continuous with the cylinder wall 12. That is, the cylinder wall 12 and the cylinder liner 14 constitute the cylinder 16. The cylinder liner 14 is entirely formed of an iron material. The cylinder block 10 is formed of an aluminum material except for the cylinder liner 14.

[0019] A water jacket 20 extends along the cylinder wall 12 within the cylinder block 10. The engine 100 includes a heater 40 having an induction coil 42 extending along the cylinder wall 12. The induction coil 42 is in the shape of a sheet. The induction coil 42 is fixed to the cylinder wall 12. As shown in FIG. 2, the heater 40 has an induction coil 42 and a drive circuit 50. Details of the drive circuit 50 will be described later. As shown in FIG. 1, the induction coil 42 is disposed within the water jacket 20. The heater 40 heats the cylinder wall 12 by generating eddy currents in the cylinder wall 12 by means of an alternating current flowing through the induction coil 42.

[0020] As shown in FIG. 1, the engine 100 includes a plurality of injectors 30 configured to inject fuel into the plurality of cylinders 16 respectively. For each of the plurality of cylinders 16, two intake valves 32 and two exhaust valves 34 are provided in the engine 100. FIG. 1 shows the plurality of injectors 30, the plurality of intake valves 32, and the plurality of exhaust valves 34 by dashed lines.

[0021] <Positional Relationship between the Plurality of Injectors 30 and the Induction Coil 42> As shown in FIG. 1, a plurality of cylinders 16 are arranged in a row, and a plurality of central axes L of the plurality of cylinders 16 are on one cross-section S of the cylinder block 10. The water jacket 20 includes a first flow path 22 located on the first side 1stSD with respect to the cross-section S and a second flow path 24 located on the second side 2ndSD with respect to the cross-section S. The first side 1stSD and the second side 2ndSD are opposite to each other with the cross-section S interposed therebetween. Each of the first flow path 22 and the second flow path 24 extends across the plurality of cylinders 16. The induction coil 42 is disposed in the second flow path 24. Each of the plurality of injectors 30 faces the second side 2ndSD.

[0022] <The drive circuit 50 of the heater 40> Referring to FIG. 2, the drive circuit 50 of the heater 40 will be described. As described above, the heater 40 includes an induction coil 42 and a drive circuit 50. A DC power supply 70 supplies a voltage to the drive circuit 50.

[0023] The drive circuit 50 has a positive electrode line 54 connected to the high potential terminal of the DC power supply 70. The drive circuit 50 has a negative electrode line 56 connected to the low potential terminal of the DC power supply 70. The drive circuit 50 has an upper arm switch 58 connected to the positive electrode line 54. The drive circuit 50 has a lower arm switch 60 connected to the negative electrode line 56. The upper arm switch 58 and the lower arm switch 60 are connected to each other. The output control unit 52 can individually turn on and off the upper arm switch 58 and the lower arm switch 60.

[0024] The drive circuit 50 has a first snubber capacitor 62 connected to the positive electrode line 54. The drive circuit 50 has a second snubber capacitor 64 connected to the negative electrode line 56. The first snubber capacitor 62 and the second snubber capacitor 64 are connected to each other. The drive circuit 50 has a resonance capacitor 66 connected to the negative electrode line 56. By changing the capacitance of the resonance capacitor 66, it is possible to change the resonance frequency of the circuit. By reducing the capacitance of the resonance capacitor 66, it is possible to increase the resonance frequency of the circuit. Thereby, the resonance frequency of the circuit can be made to match the frequency of the alternating magnetic field desired for heating the cylinder wall 12.

[0025] The midpoint between the upper arm switch 58 and the lower arm switch 60 is connected to the first end of the induction coil 42. The midpoint between the first snubber capacitor 62 and the second snubber capacitor 64 is connected to the first end of the induction coil 42. The second end of the induction coil 42 is connected to the negative electrode line 56 via the resonance capacitor 66.

[0026] By keeping the upper arm switch 58 on and keeping the lower arm switch 60 off, current flows in one direction in the induction coil 42. Thereafter, by keeping the upper arm switch 58 off and keeping the lower arm switch 60 on, current flows in the reverse direction in the induction coil 42. This is due to the charge stored in the resonance capacitor 66 flowing out by keeping the upper arm switch 58 on and keeping the lower arm switch 60 off.

[0027] <Magnetic field generated by the induction coil 42> Referring to FIG. 3, the magnetic field generated by the induction coil 42 will be described. One turn of the induction coil 42 extends across a plurality of cylinders 16. Therefore, when an alternating current flows through the induction coil 42, the same polarity appears at the portions of the plurality of cylinders 16 facing the induction coil 42. In FIG. 3, the N pole appears at the portions of the plurality of cylinders 16 facing the induction coil 42. The S pole appears at the portions of the plurality of cylinders 16 on the side opposite to the induction coil 42. As shown by the arrows in FIG. 3, magnetic field lines are generated so as to wrap around the cylinder 16.

[0028] <Effect of the First Embodiment> (1-1) According to the present embodiment, the cylinder wall 12 can be heated by generating eddy currents in the cylinder wall 12 using the induction coil 42 regardless of whether the engine 100 has just started. Thereby, the cylinder liner 14 can be heated. As a result, the fuel attached to the cylinder liner 14 can be sufficiently vaporized, so that the generation of PM can be suppressed even immediately after the engine 100 is started.

[0029] (1-2) Different from the present embodiment, a comparative example can be considered in which the cylinder block 10 includes a heater 40 having a resistance heating element extending along the cylinder wall 12. In the comparative example, it is necessary to bring the resistance heating element into close contact with the cylinder wall 12 from the viewpoint of ensuring the effectiveness of heating the cylinder wall 12. However, it is difficult to bring the resistance heating element into close contact with the cylinder wall 12. This difficulty is due to the fact that the cylinder wall 12 is a casting and has many irregularities. On the other hand, in the present embodiment, the cylinder block 10 includes a heater 40 having an induction coil 42 extending along the cylinder wall 12. The induction coil 42 can generate sufficient eddy currents in the cylinder wall 12 without being in close contact with the cylinder wall 12. Therefore, the induction coil 42 does not have to be in close contact with the cylinder wall 12. Therefore, the engine 100 of the present embodiment is easier to manufacture than the comparative example.

[0030] (1-3) In the above comparative example where the heater 40 has a resistive heating element, heat transfer from the resistive heating element to the cylinder wall 12 is necessary. In contrast, in the above embodiment, the cylinder wall 12 itself can be heated. This means that since heat transfer from the resistive heating element to the cylinder wall 12 is unnecessary, the temperature rise efficiency is excellent.

[0031] (1-4) In the above comparative example where the heater 40 has a resistive heating element, due to the absence of a wire between the wires constituting the resistive heating element, a region of the cylinder wall 12 that is difficult to heat is likely to occur. In contrast, in the above embodiment, since the induction coil 42 can generate eddy currents in the cylinder wall 12, it is easy to heat a wide area of the cylinder wall 12.

[0032] (1-5) In the present embodiment, the induction coil 42 is disposed in the second flow path 24. Each of the plurality of injectors 30 faces the second side 2ndSD. For this reason, it becomes easy to heat the portion of the cylinder liner 14 where fuel is likely to adhere. For this reason, it becomes easy to sufficiently vaporize the fuel adhering to the cylinder liner 14. Thereby, generation of PM is likely to be suppressed.

[0033] (Second Embodiment) Hereinafter, the engine according to the second embodiment will be described with reference to the drawings. Description of the configurations common to the engines 100 according to the first and second embodiments will be omitted.

[0034] In the engine 100 according to the first embodiment shown in FIG. 1, the cylinder liner 14 is entirely formed of an iron material. The cylinder block 10 is formed of an aluminum material except for the cylinder liner 14. In contrast, in the engine 100 according to the second embodiment shown in FIG. 4, the cylinder wall 12 and the cylinder liner 14 are entirely formed of an iron material. The cylinder block 10 is formed of an aluminum material except for the cylinder wall 12 and the cylinder liner 14.

[0035] <Effects of the Second Embodiment> According to the engine 100 according to the second embodiment, in addition to the effects described in the above (1-1) to (1-5), the following effects can be obtained.

[0036] (2-1) Generally, the cylinder block 10 is known to be formed of an aluminum material for the purpose of weight reduction. Also, generally, the cylinder liner 14 is known to be formed of an iron material for the purpose of ensuring durability.

[0037] In contrast, in the second embodiment, while the cylinder wall 12 and the cylinder liner 14 are entirely formed of an iron material, the cylinder block 10 is formed of an aluminum material except for the cylinder wall 12 and the cylinder liner 14. Different from the second embodiment, in the first embodiment, the cylinder wall 12 is formed of an aluminum material.

[0038] Assume a case where the induction coil 42 applies an alternating magnetic field having a given frequency to the cylinder wall 12. The magnitude of the eddy current flowing when the cylinder wall 12 is formed of an aluminum material is the same as the magnitude of the eddy current flowing when the cylinder wall 12 is formed of an iron material. The magnitude of the eddy current increases in direct proportion to the frequency of the alternating magnetic field.

[0039] The volume resistivity of the iron material is about 4 times that of the aluminum material. For this reason, in order to generate the same amount of Joule heat as in the second embodiment, it is necessary to increase the frequency by about 4 times in the first embodiment. In the second embodiment, the cylinder wall 12 can be induction heated by passing an alternating current with a relatively low frequency through the induction coil 42. For this reason, according to the second embodiment, the heater 40 that is expensive to generate a high-frequency alternating current becomes unnecessary. Therefore, according to the second embodiment, the cost required for the heater 40 can be reduced.

[0040] (2-2) The aluminum material is a non-magnetic material. Therefore, in the first embodiment, in order to inductively heat the cylinder wall 12, it is necessary to pass a high-frequency alternating current through the induction coil 42. On the other hand, in the second embodiment, the cylinder wall 12 is formed of an iron material which is a magnetic material. Therefore, the cylinder wall 12 can be inductively heated by passing a relatively low-frequency alternating current through the induction coil 42. For this reason, according to the second embodiment, the heater 40 which has a high cost of generating a high-frequency alternating current becomes unnecessary. Therefore, according to the second embodiment, the cost required for the heater 40 can be reduced.

[0041] (2-3) Generally, as the frequency of the alternating magnetic field increases, eddy currents flow in a portion closer to the surface of the object to which the alternating magnetic field is applied. This is generally called the skin effect.

[0042] The induction coil 42, the cylinder wall 12, and the cylinder liner 14 are arranged in this order. As described above, it is desired to heat the cylinder liner 14 so that the fuel attached to the cylinder liner 14 can be sufficiently vaporized. For this reason, an increase in the frequency of the alternating magnetic field means that a portion farther from the cylinder liner 14 which is desired to be heated is more likely to be heated. This means that it becomes difficult to heat the cylinder liner 14. According to the second embodiment, the frequency of the alternating magnetic field can be set lower. For this reason, according to the second embodiment, the influence of the skin effect can be reduced. This means that it becomes easier to heat the cylinder liner 14.

[0043] (Modification example) Elements that can be commonly modified in the first and second embodiments are as follows. The following modification examples can be implemented in combination with each other within a technically non-contradictory range.

[0044] · The cylinder block 10 may be entirely formed of an iron material. · In the above first and second embodiments, the induction coil 42 is provided only in the second flow path 24. In addition to or instead of this, an induction coil different from the induction coil 42 may be provided in the first flow path 22.

Explanation of Signs

[0045] 10… Cylinder block 12… Cylinder wall 14… Cylinder liner 16… Cylinder 20… Water jacket 22… First flow path 24… Second flow path 30… Injector 40… Heater 42… Induction coil 100… Engine

Claims

1. An engine comprising: a cylinder block having a cylinder wall and a cylinder liner located inside the cylinder wall and continuous with the cylinder wall; a heater disposed in a water jacket extending along the cylinder wall within the cylinder block and having an induction coil extending along the cylinder wall; wherein the heater is configured to heat the cylinder wall by generating eddy currents in the cylinder wall by an alternating current flowing through the induction coil. The engine.

2. While the cylinder wall and the cylinder liner are entirely formed of an iron material, the cylinder block is formed of an aluminum material except for the cylinder wall and the cylinder liner. The engine according to Claim 1.

3. The cylinder wall and the cylinder liner constitute a cylinder, which is one of a plurality of cylinders of the cylinder block. The plurality of cylinders are arranged in a row, and the plurality of central axes of the plurality of cylinders are on one cross-section of the cylinder block. The water jacket consists of a first flow path located on a first side with respect to the cross-section and a second flow path located on a second side with respect to the cross-section, and the first side and the second side are opposite to each other across the cross-section. Each of the first flow path and the second flow path extends across the plurality of cylinders. The induction coil is disposed in the second flow path. The engine according to Claim 1 or 2.

4. Comprising a plurality of injectors configured to inject fuel into the plurality of cylinders respectively. Each of the plurality of injectors faces the second side. The engine according to Claim 3.

Images