Cylinder heater

Abstract

To provide a cylinder heater capable of easily securing an installation place of an electrode for causing an electric current to flow in a cylinder liner.SOLUTION: A cylinder heater includes: an electric power conversion device that converts a DC electric current output from a DC power source into a high-frequency AC electric current; and a transformer having a primary side coil electrically connected to the electric power conversion device and a secondary side coil electrically connected to electrodes provided to correspond to one side and the other side of a cylinder liner, respectively in an axial direction of a cylinder of a cylinder block provided in an internal combustion engine. In the cylinder heater, the electrode on one side is electrically connected to a lower part of the cylinder block and the electrode on the other side is a grounding electrode of an ignition plug.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 placed 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 an electric current directly through the cylinder liner, but because the upper part of the cylinder liner is where the gasket and cylinder head are stacked on the cylinder block, it is difficult to secure a location for installing an electrode to pass an electric current through the cylinder liner.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a cylinder heating device that makes it easy to secure a location for installing electrodes for passing current through the 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 power conversion device that converts a DC current output from a DC power source into a 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 in a cylinder block of an internal combustion engine corresponding to one side and the other side of a cylinder liner in the axial direction of the cylinder, wherein the electrode on one side is electrically connected to the lower part of the cylinder block, and the electrode on the other side is a ground electrode of an ignition plug.

[0007] As a result, the cylinder heating device according to the present invention can easily satisfy the requirement of ensuring a location for installing electrodes for passing current through the cylinder liner.

[0008] In the above, the power conversion device and the transformer may be provided inside a case of an ignition coil connected to the spark plug.

[0009] This makes it possible to easily secure a place to install the power conversion device and the transformer. [Effects of the Invention]

[0010] The cylinder heating device according to the present invention has the effect of easily ensuring a location for installing electrodes for passing an electric current through the cylinder liner. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a cylinder heating device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[0013] FIG. 1 is a diagram showing a schematic configuration of a cylinder heating device 1 according to an embodiment. The cylinder heating device 1 according to the embodiment is a device for heating a cylinder liner 72 (cylinder 7) provided in a cylinder block 71 of a gasoline engine, which is an internal combustion engine. In this embodiment, a crankcase is provided below the cylinder block 71, and the cylinder 7 (cylinder) is formed by stacking a gasket and a cylinder head on top of the cylinder block 71. The cylinder head is also provided with an ignition plug 9 having a center electrode 91 and a ground electrode 92, which is inserted into the combustion chamber from the outside of the cylinder 7.

[0014] The cylinder heating device 1 of the embodiment includes a power conversion device that converts a direct current output from a direct current power source into a high-frequency alternating current, and a transformer 5 having a primary coil 51 electrically connected to the power conversion device, and a secondary coil 52 electrically connected to two electrodes 8, 92 provided corresponding to one side and the other side of a cylinder liner 72 in the axial direction of a cylinder 7 in a cylinder block 71 provided in an internal combustion engine.

[0015] The DC power supply is, for example, a 12V power supply system, and outputs DC current. An ignition coil 10 (igniter coil) with an integrated igniter is connected to the spark plug 9. In this embodiment, one ignition coil 10 is provided for each spark plug 9. A DC power supply is connected to a primary coil 53 provided in a case of the ignition coil 10. One end of a secondary coil 54 provided in a case of the ignition coil 10 is connected to a center electrode 91 of the spark plug 9 via a diode 62. The other end of the secondary coil 54 of the ignition coil 10 is connected to a ground electrode 92 of the spark plug 9.

[0016] Furthermore, the control device 2 and the primary coil 53 are connected to an igniter 61 provided inside the case of the ignition coil 10. The igniter 61 is turned on and off by an ignition instruction signal input from the control device 2. A primary current flowing through the primary coil 53 is energized when the igniter 61 is turned on and is cut off when the igniter 61 is turned off. When the primary current is cut off, a high voltage is generated in the secondary coil 54 of the ignition coil 10 by electromagnetic induction, and a spark is generated between the center electrode 91 and the ground electrode 92 of the spark plug 9. In the ignition coil 10, the primary coil 53 and secondary coil 54 for generating a spark between the center electrode 91 and the ground electrode 92 of the spark plug 9 form a transformer 5.

[0017] Additionally, an output control driver 3, an inverter circuit 4, a primary coil 51, a secondary coil 52, and the like are provided within the case of the ignition coil 10, partially utilizing an existing circuit for generating a spark between the center electrode 91 and the ground electrode 92 of an existing spark plug 9. The output control driver 3 is connected to the control device 2. The output control driver 3 performs on / off control of four switching elements 41, 42, 43, and 44 provided in the inverter circuit 4 (described later) based on control signals from the control device 2. In the cylinder heating device 1 according to this embodiment, the output control driver 3 and the inverter circuit 4 form a power conversion device that converts a DC current output from a DC power supply into a high-frequency AC current.

[0018] The inverter circuit 4 is electrically connected to the DC power supply via a high-voltage power line electrically connected to the positive terminal of the DC power supply and a low-voltage power line electrically connected to the negative terminal of the DC power supply. 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 a 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 driver 3.

[0021] In the cylinder heating device 1 according to this embodiment, a lower electrode 8 and a ground electrode 92 of a spark plug 9 are used as two electrodes provided corresponding to one side and the other side of a cylinder liner 72 in the axial direction of the cylinder 7 in a cylinder block 71. The lower electrode 8 is electrically connected to the cylinder block 71 (cylinder liner 72) so as to correspond to the crankcase side of the cylinder liner 72, which is the one side. The ground electrode 92 of the spark plug 9 is electrically connected to the cylinder block 71 (cylinder liner 72) so as to correspond to the head gasket side of the cylinder liner 72, which is the other side. The lower electrode 8 and the ground electrode 92 of the spark plug 9 are electrically connected to the secondary coil 52, which is the output side of the transformer 5, via power lines.

[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 7 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. Joule heat is generated directly by passing an electric current through the cylinder liner 72 itself, which heats the cylinder liner 72. 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 to the cylinder liner 72, the current will not flow to the intended location of the cylinder liner 72. For this reason, an isolated power supply that is isolated from the DC power supply by a transformer 5 or the like is used as the power supply for passing a current through the cylinder liner 72.

[0024] To pass current through the cylinder liner 72 while floating from the DC power source 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 71 and the iron (cast iron) cylinder liner 72 between the lower electrode 8 and the ground electrode 92, resulting in a very low resistance between the lower electrode 8 and the ground electrode 92. Therefore, a large current is required to generate sufficient Joule heat. Furthermore, because the resistance between the lower electrode 8 and the ground electrode 92 is low, the current diffuses over a wide area beyond the area between the lower electrode 8 and the ground electrode 92. 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 71 and instead flowing through the surface of the cylinder liner 72 (the cylinder bore wall). As a result, the resistance between the lower electrode 8 and the ground electrode 92 increases due to the reduced current carrying area, making it possible to heat only the surface layer of the cylinder liner 72 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 72 is heated by passing current directly from the DC power source to the cylinder liner 72 via the transformer 5, which reduces energy loss compared to when the cylinder liner 72 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 72 between the lower electrode 8 and the ground electrode 92. When a high-frequency current (AC current) is passed through the cylinder liner 72, a skin effect occurs, causing current to flow only in the surface layer of the cylinder liner 72. When current flows only in the surface layer of the cylinder liner 72, the cross-sectional area through which the current passes is reduced in terms of volume resistivity, and the resistance between the lower electrode 8 and the ground electrode 92 increases. When the resistance between the lower electrode 8 and the ground electrode 92 is high, the current attempts to pass through the shortest path with the lowest resistance. As a result, the amount of current flowing in paths that deviate from the shortest path is reduced.

[0027] Furthermore, the skin effect increases the resistance between the lower electrode 8 and the ground electrode 92, causing current to flow through the shortest path between the lower electrode 8 and the ground electrode 92. Therefore, by optimizing the arrangement of the lower electrode 8 and the ground electrode 92, it becomes possible to heat only the targeted portion of the surface of the cylinder liner 72 (cylinder bore wall surface) more efficiently.

[0028] Here, if an electrode were to be installed on the top of the cylinder liner 72 of the cylinder block 71, it would be located where the gasket would be, making it difficult to route an electrode or wire harness there. Furthermore, when the cylinder block 71, gasket, and cylinder head are stacked, the cylinder 7 becomes a single metal tube. Therefore, an electrode must be installed somewhere on the surface of this tube. The cylinder head contains an ignition plug 9 inserted from the outside of the cylinder 7. The ground electrode 92 of the spark plug 9 is a component with a metal surface that connects the inside and outside of the cylinder 7. Therefore, for example, the ground electrode 92 of the spark plug 9 is installed in contact with the top of the cylinder liner 72 of the cylinder block 71. This allows current to flow through the surface of the cylinder liner 72 between the lower electrode 8 and the ground electrode 92 due to the skin effect. Therefore, the cylinder heating device 1 according to this embodiment can easily secure a location for an electrode to pass current through the surface of the cylinder liner 72.

[0029] In the cylinder heating device 1 according to the embodiment, an output control driver 3 for heating the cylinder liner, an inverter circuit 4, and a transformer 5 (primary coil 51 and secondary coil 52) are provided inside the case of the ignition coil 10. This makes it easy to ensure that there are sufficient locations for installing the output control driver 3 for heating the cylinder liner, the inverter circuit 4, and the transformer 5 (primary coil 51 and secondary coil 52).

[0030] Furthermore, one end of the secondary coil 52 for heating the cylinder liner is connected to a lower electrode 8 provided below the cylinder liner 72 in the cylinder block 71 via wiring drawn from the ignition coil 10. The other end of the secondary coil 52 for heating the cylinder liner is connected to a ground electrode 92 of the spark plug 9. This makes it possible to reduce the installation space for the output control driver 3 for heating the cylinder liner, the inverter circuit 4, and the transformer 5 (primary coil 51 and secondary coil 52) and the amount of wiring for heating the cylinder liner. Furthermore, by designing the ignition coil 10 as a circuit for only one cylinder, even if the number of cylinders is increased or decreased, the ignition coil 10 is necessarily provided according to the number of cylinders, eliminating the need to secure additional space or to design a case according to the number of cylinders.

[0031] Furthermore, in the cylinder heating device 1 according to this embodiment, before the engine starts, the output control driver 3 controls the on / off of the switching elements 41, 42, 43, and 44 of the inverter circuit 4 based on a control signal from the control device 2. This allows a high-frequency AC current to flow between the lower electrode 8 and the ground electrode 92 via the primary coil 51 and secondary coil 52 for heating the cylinder liner, thereby causing a current to flow through the surface layer of the cylinder liner 72 due to the skin effect, thereby heating it. Furthermore, during and after the engine starts, the on / off operation of the igniter 61 is controlled by an ignition command signal input from the control device 2, thereby generating a spark between the center electrode 91 and the ground electrode 92 of the spark plug 9.

[0032] Furthermore, in the cylinder heating device 1 according to the embodiment, the cylinder liner 72 can be heated with one ignition coil 10 per cylinder. Therefore, even if the number of cylinders changes to three, four, six, eight, etc., the number of ignition coils 10 necessarily increases or decreases depending on the number of cylinders, so the cylinder heating device 1 according to the embodiment can also accommodate changes in the number of cylinders.

[0033] In the above description of the embodiments, the internal combustion engine is assumed to be a gasoline engine. However, in the case of a diesel engine, it is possible to achieve the same function as in the case of a gasoline engine by using the ground electrode of a glow plug. [Explanation of symbols]

[0034] 1 Cylinder heating device 2. Control device 3 Output Control Driver 4. Inverter circuit 5. Transformer 7 cylinders 8 Lower electrode 9 Spark plugs 10. Ignition coil 41, 42, 43, 44 Switching elements 51,53 Primary coil 52,54 Secondary coil 61 Igniter 62 Diode 71 Cylinder block 72 Cylinder liner 91 Center electrode 92 Ground electrode

Claims

1. a power conversion device that converts a direct current output from a 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 electrode on one side is electrically connected to the lower part of the cylinder block, The cylinder heating device is characterized in that the other electrode is a ground electrode of an ignition plug.

2. 2. The cylinder heating device according to claim 1, wherein the power converter and the transformer are provided inside a case of an ignition coil connected to the spark plug.

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