Cylinder heating device

Abstract

To provide a cylinder heating device that can improve the heat generation efficiency of a cylinder liner.SOLUTION: A cylinder heating device of the present invention is a cylinder heating device comprising: a DC power supply that outputs a DC current; a power conversion device that converts the DC current output from the DC power supply into a high-frequency AC current; and a transformer having a primary side coil electrically connected to the power conversion device and a secondary side coil electrically connected to electrodes that are provided in a cylinder block provided in an internal combustion engine, the electrodes corresponding to one side and the other side of a cylinder liner in the axial direction of the cylinder. The cylinder liner is made of iron and the cylinder block is made of an aluminum alloy, and a high-resistance section made of alumina with a higher electrical resistance than iron is provided in the path of the current flowing on the cylinder block side between the electrodes on one side and the electrodes on the other side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cylinder heating device. [Background technology]

[0002] Patent Document 1 discloses a cylinder heating device that heats a cylinder liner using an electric heater. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-171886 Summary of the Invention [Problem to be solved by the invention]

[0004] In the cylinder heating device disclosed in Patent Document 1, an electric heater is interposed between the cylinder liner and a power source, which results in energy loss due to the electric heater when heating the cylinder liner. Therefore, it is possible to pass current directly through the cylinder liner, but if the cylinder liner is made of iron and the cylinder block is made of aluminum alloy, the electrical resistance of aluminum alloy is lower than that of iron, which makes it easier for current to flow through the cylinder block, potentially reducing the heating efficiency of the cylinder liner.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a cylinder heating device that can improve the heat generation efficiency of a cylinder liner. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the cylinder heating device of the present invention is a cylinder heating device comprising: a DC power supply that outputs DC current; a power conversion device that converts the DC current output from the DC power supply into high-frequency AC current; and a transformer having a primary coil electrically connected to the power conversion device and a secondary coil electrically connected to electrodes provided on one side and the other side of a cylinder liner in the axial direction of the cylinder in a cylinder block provided in an internal combustion engine, wherein the cylinder liner is made of iron, the cylinder block is made of aluminum alloy, and a high-resistance section made of alumina and having higher electrical resistance than iron is provided in the path of the current flowing on the cylinder block side between the one electrode and the other electrode.

[0007] As a result, the cylinder heating device of the present invention can increase the electrical resistance of the path of current flowing toward the cylinder block between one electrode and the other electrode, and keep the electrical resistance of the path of current flowing toward the cylinder liner low, making it easier for current to flow to the cylinder liner and improving the heating efficiency of the cylinder liner.

[0008] In the above configuration, the high resistance portion may be provided on an upper surface or a lower surface of the cylinder block.

[0009] This makes it easier to process aluminum into alumina when forming a high resistance portion in the cylinder block.

[0010] In the above configuration, the high resistance portion may be provided in an annular shape along an end surface of the cylinder in an axial direction.

[0011] This makes it possible to minimize the area where aluminum is machined into alumina when providing a high resistance portion in the cylinder block. [Effects of the Invention]

[0012] The cylinder heating device of the present invention increases the electrical resistance of the path of current flowing toward the cylinder block between one electrode and the other electrode, and reduces the electrical resistance of the path of current flowing toward the cylinder liner, thereby making it easier for current to flow to the cylinder liner and improving the heating efficiency of the cylinder liner. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a cylinder heating device according to an embodiment. [Figure 2] FIG. 2 is a top view of a cylinder block to which the cylinder heating device according to the embodiment is applied. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of a cylinder heating device according to the present invention will be described, but the present invention is not limited to the embodiment.

[0015] Fig. 1 is a diagram showing a schematic configuration of a cylinder heating device 1 according to an embodiment. Fig. 2 is a top view of a cylinder block 61 to which the cylinder heating device 1 according to the embodiment is applied.

[0016] The cylinder heating device 1 according to the embodiment is a device for heating a cylinder liner 62 (cylinder 6) provided in a cylinder block 61 of an internal combustion engine.

[0017] The cylinder heating device 1 according to the embodiment includes a DC power supply 2, an output control unit 3, an inverter circuit 4, and a transformer 5. The DC power supply 2 is a 12 V power supply system or a high-voltage power supply system (high-voltage battery), and outputs DC current to the inverter circuit 4. The output control unit 3 controls the on / off of four switching elements 41, 42, 43, and 44 provided in the inverter circuit 4. In the cylinder heating device 1 according to the embodiment, the output control unit 3 and the inverter circuit 4 constitute a power conversion device that converts the DC current output from the DC power supply 2 into high-frequency AC current.

[0018] The inverter circuit 4 is electrically connected to the DC power supply 2 via a high-voltage power line electrically connected to a positive terminal of the DC power supply 2 and a low-voltage power line electrically connected to a negative terminal of the DC power supply 2. The inverter circuit 4 is provided with four switching elements 41, 42, 43, and 44. In the inverter circuit 4, the switching elements 41 and 42 are connected in series between the high-voltage power line and the low-voltage power line, and the switching elements 43 and 44 are connected in series between the high-voltage power line and the low-voltage power line, and are connected in parallel to each other. The four switching elements 41, 42, 43, and 44 form an H-bridge circuit in which two pairs of cascade-connected switching elements are connected in parallel to each other.

[0019] The inverter circuit 4 is also provided with four capacitors 45, 46, 47, and 48. In the inverter circuit 4, the capacitors 45 and 46 are connected in series between the high-voltage line and the low-voltage line, and the capacitors 47 and 48 are also connected in series between the high-voltage line and the low-voltage line, and are connected in parallel to each other.

[0020] The connection point between switching element 41 and switching element 42 is electrically connected to the connection point between capacitor 45 and capacitor 46 via a power line. In addition, the connection point between switching element 43 and switching element 44 is electrically connected to the connection point between capacitor 47 and capacitor 48 via a power line. The connection point between capacitor 45 and capacitor 46 and the connection point between capacitor 47 and capacitor 48 are each electrically connected to a primary coil 51 of transformer 5 via a power line. As a result, the inverter circuit 4 and primary coil 51, which is the input side of transformer 5, are electrically connected via the power line, and AC current is output from the inverter circuit 4 to the primary coil 51 of transformer 5 by on / off control of the four switching elements 41, 42, 43, and 44 by the output control unit 3.

[0021] Two electrodes 71, 72 are provided corresponding to one side and the other side of a cylinder liner 62 in the axial direction of the cylinder 6 provided in the cylinder block 61, and are electrically connected via power lines to the secondary coil 52 on the output side of the transformer 5. The electrode 71 is electrically connected to the cylinder block 61 (cylinder liner 62) corresponding to the crankcase side of the cylinder liner 62, which is the one side. The electrode 72 is electrically connected to the cylinder block 61 (cylinder liner 62) corresponding to the head gasket side of the cylinder liner 62, which is the other side. The secondary coil 52 of the transformer 5 is isolated from the DC power source 2, which reduces the risk of current flowing outside the cylinder block 61 and causing noise.

[0022] In recent years, exhaust gas regulations for automobiles equipped with gasoline engines have become stricter, and there is a particular need to address particulate matter. Particulate matter is generated in gasoline engines when unvaporized fuel sprayed from the injector adheres to the wall surface inside the cylinder 6 and is ignited in an incomplete mixture, generating soot (particulate matter) from the unburned gas. However, even if the fuel adheres to the wall surface, if it vaporizes before ignition and becomes a state in which an air-fuel mixture can be easily formed, the amount of particulate matter generated can be reduced. By passing an electric current through the cylinder liner 62 itself, Joule heat is directly generated to heat the cylinder liner 62. Note that the Joule heat is calculated as follows: R x I, where R is the resistance value [Ω], I is the current [A], and P is the output [W]. 2 = Calculated by multiplying P[W] by time.

[0023] If a DC current is passed directly from the DC power supply 2 to the cylinder liner 62, the current will not flow to the intended location of the cylinder liner 62. For this reason, an isolated power supply that is isolated from the DC power supply 2 by a transformer 5 or the like is used as the power supply for passing a current through the cylinder liner 62.

[0024] To pass current through the cylinder liner 62 while floating from the DC power source 2 using the transformer 5, an inverter circuit 4 is required to generate AC current. When the AC current has a low frequency of approximately 50 to 60 Hz, the current also passes through the aluminum alloy cylinder block 61 and the iron (cast iron) cylinder liner 62 between the two electrodes 71 and 72, resulting in a very low resistance between the two electrodes 71 and 72. Therefore, a large current is required to generate sufficient Joule heat. Furthermore, because the resistance between the two electrodes 71 and 72 is low, the current diffuses over a wide area beyond the area between the two electrodes 71 and 72. On the other hand, by increasing the frequency of the AC current to, for example, 20 kHz, a skin effect is generated, preventing current from flowing into the cylinder block 61 and instead flowing through the surface of the cylinder liner 62 (the cylinder bore wall). This reduces the current-carrying area, increasing the resistance between the two electrodes 71, 72, making it possible to heat only the surface layer of the cylinder liner 62 with less current than at low frequencies (50 to 60 Hz).

[0025] Furthermore, in the cylinder heating device 1 according to the embodiment, the cylinder liner 62 is heated by passing current directly from the DC power source 2 through the transformer 5 to the cylinder liner 62, which reduces energy loss compared to when the cylinder liner 62 is heated by passing current through a separately provided electric heater.

[0026] In Fig. 1, the solid arrows indicate the current flow (path) in the cylinder liner 62 between the electrodes 71 and 72. Also in Fig. 1, the dashed arrows indicate the current flow (path) in the cylinder block 61 between the electrodes 71 and 72. Note that in Fig. 1, the thickness of the solid and dashed arrows indicates the amount of current.

[0027] When a high-frequency current (AC current) is passed through the cylinder liner 62, a skin effect occurs, causing the current to flow only through the surface layer of the cylinder liner 62. When the current flows only through the surface layer of the cylinder liner 62, the cross-sectional area through which the current passes is reduced in terms of volume resistivity, and the resistance between the two electrodes 71, 72 increases. When the resistance between the two electrodes 71, 72 is high, the current tries to pass through the shortest path with the lowest resistance. Therefore, the amount of current flowing through paths that deviate from the shortest path is reduced.

[0028] In addition, the skin effect increases the resistance between the two electrodes 71, 72, causing current to flow along the shortest path between the two electrodes 71, 72. Therefore, by optimizing the positioning of the two electrodes 71, 72, it becomes possible to more efficiently heat only the targeted area on the surface of the cylinder liner 62 (cylinder bore wall surface).

[0029] When high-frequency current is applied to the electrodes 71, 72 provided on the top and bottom of the iron cylinder block 61 (cylinder liner 62), the current tends to flow toward the area with lower electrical resistance. Therefore, if more current flows through the aluminum alloy cylinder block 61 than through the iron cylinder liner 62, the heat generation efficiency of the cylinder liner 62 decreases, and there is a risk that the cylinder liner 62, which is intended to be heated, will not be heated efficiently.

[0030] Therefore, in the cylinder heating device 1 according to the embodiment, in order to make it difficult for current to flow toward the cylinder block 61 between electrodes 71, 72 provided on the upper and lower parts of the cylinder block 61 (cylinder liner 62), a high-resistance portion 63 with high electrical resistance is provided in the path of current flowing toward the cylinder block 61 between the electrodes 71, 72. The high-resistance portion 63 is provided in an annular shape on the upper surface of the cylinder block 61 along the annular end face (gasket surface) 61a in the axial direction of the cylinder 6. The high-resistance portion 63 is formed by converting aluminum on the surface of the cylinder block 61 into alumina (aluminum oxide).

[0031] For reference, the electrical resistance values ​​of the conductive materials used in this embodiment are as follows: The electrical resistivity of the aluminum alloy used for the cylinder block 61 is 2.65×10 -8 The electrical resistivity of the iron used in the cylinder liner 62 is 10 × 10 -8 The electrical resistance of the alumina used in the high resistance portion 63 is 10 14 ~10 18 [Ω·m].

[0032] In the cylinder heating device 1 according to the embodiment, between the electrodes 71, 72 provided on the upper and lower parts of the cylinder block 61 (cylinder liner 62), the electrical resistance of the path of current flowing toward the cylinder block 61 can be increased, and the electrical resistance of the path of current flowing toward the cylinder liner 62 can be kept low. Therefore, in the cylinder heating device 1 according to the embodiment, current flows more easily to the cylinder liner 62, allowing more current to flow and improving the heat generation efficiency of the cylinder liner 62, making it possible to efficiently heat the cylinder liner 62.

[0033] In addition, the high resistance portion 63 is preferably provided on the upper or lower surface of the cylinder block 61, which is easy to process, in order to process aluminum into alumina.

[0034] As a method for processing aluminum into alumina, for example, alumina can be formed on the surface by subjecting aluminum to electrical discharge in water using electrical discharge machining or the like. Alumina can also be generated on the surface of aluminum by a chemical reaction. A specific method for processing aluminum into alumina is to use dilute sulfuric acid or oxalic acid in a treatment bath and electrolyze the aluminum as the anode, thereby electrochemically oxidizing the aluminum surface to generate an alumina film. This type of processing makes it possible to form an alumina layer at a level of several to several tens of microns from the surface.

[0035] By providing annular high-resistance portions along the annular end faces of the cylinders 6 in the axial direction on the upper or lower surface of the cylinder block 61, it is possible to minimize the area in which aluminum is machined into alumina. In the example shown in Fig. 2, annular high-resistance portions 63A, 63B, 63C, and 63D are machined into alumina on the upper surface of the cylinder block 61 at annular end faces 61aA, 61aB, 61aC, and 61aD in the axial direction of the four cylinders 6A, 6B, 6C, and 6D. This makes it easiest to machine the aluminum of the cylinder block 61 into alumina, and also reduces the area to be machined compared to machining aluminum into alumina over the entire upper surface of the cylinder block 61. [Explanation of symbols]

[0036] 1 Cylinder heating device 2 DC power supply 3 Output control section 4. Inverter circuit 5. Transformer 6, 6A, 6B, 6C, 6D Cylinder 41, 42, 43, 44 Switching elements 61 Cylinder block 61a,61aA,61aB,61aC,61aD End face 62 Cylinder liner 63,63A,63B,63C,63D High resistance part 71,72 electrode

Claims

1. a DC power supply that outputs a DC current; a power conversion device that converts a direct current output from the direct current power supply into a high-frequency alternating current; a transformer having a primary coil electrically connected to the power conversion device and a secondary coil electrically connected to electrodes provided in a cylinder block of the internal combustion engine, the electrodes corresponding to one side and the other side of a cylinder liner in the axial direction of the cylinder; A cylinder heating device comprising: the cylinder liner is made of iron, the cylinder block is made of an aluminum alloy, A cylinder heating device characterized in that a high resistance section made of alumina and having a higher electrical resistance than iron is provided in the path of the current flowing on the cylinder block side between the one electrode and the other electrode.

2. 2. The cylinder heating device according to claim 1, wherein the high resistance portion is provided on the upper surface or the lower surface of the cylinder block.

3. 3. The cylinder heating device according to claim 2, wherein the high resistance portion is provided on the upper surface of the cylinder block in an annular shape along an end surface of the cylinder in the axial direction of the cylinder.

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