Cylinder heating device

Abstract

To provide a cylinder heating device that enables a reduction in energy loss.SOLUTION: A cylinder heating device includes: a DC power supply that outputs a DC current; a power converter that converts the DC current output from the DC power supply to an AC current; and a transformer including a primary coil that is electrically connected to the power converter and a secondary coil that is electrically connected to electrodes each correspondingly provided on one side and the other side of a cylinder liner in an axial direction of the cylinder installed in an internal combustion engine.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[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

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the cylinder heating device disclosed in Patent Document 1, since an electric heater is interposed between the cylinder liner and the power source, energy loss occurs due to the electric heater when the cylinder liner is heated.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a cylinder heating device capable of reducing energy loss.

Means for Solving the Problems

[0006] In order to solve the above problems and achieve the object, a cylinder heating device according to the present invention includes a DC power source that outputs a DC current, a power conversion device that converts the DC current output from the DC power source into an AC current, a primary side coil electrically connected to the power conversion device, and a secondary side coil electrically connected to electrodes provided on one side and the other side of a cylinder liner in the axial direction of a cylinder provided in an internal combustion engine. The cylinder heating device is characterized by including a transformer having the secondary side coil.

Effects of the Invention

[0007] The cylinder heating device according to the present invention heats the cylinder liner by directly passing an electric current through it, thereby reducing energy loss. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a diagram showing the schematic configuration of a cylinder heating device according to an embodiment. [Figure 2] Figure 2 shows the first example of the relationship between electrode position and alternating current flow. [Figure 3] Figure 3 shows a second example of the relationship between electrode position and alternating current flow. [Figure 4] Figure 4 shows a third example of the relationship between electrode position and alternating current flow. [Figure 5] Figure 5 shows a case where two secondary coils of a transformer are provided for two cylinders. [Figure 6] Figure 6 shows a case where one secondary coil of a transformer is provided for two cylinders. [Modes for carrying out the invention]

[0009] The following describes an embodiment of the cylinder heating device according to the present invention. However, the present invention is not limited to this embodiment.

[0010] Figure 1 is a diagram showing the 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 62 (cylinder 6) provided in the cylinder block 61 of an engine, which is an internal combustion engine.

[0011] The cylinder heating device 1 according to this 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 a DC current to the inverter circuit 4. The output control unit 3 controls the on / off state of four switching elements 41, 42, 43, and 44 provided in the inverter circuit 4. In the cylinder heating device 1 according to this 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 AC current.

[0012] The inverter circuit 4 is electrically connected to the DC power supply 2 by a high-voltage power line electrically connected to the positive terminal of the DC power supply 2 and a low-voltage power line electrically connected to the 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, switching elements 41 and 42, which are connected in series with each other, and switching elements 43 and 44, which are connected in series with each other, are connected in parallel with each other. The four switching elements 41, 42, 43, and 44 constitute an H-bridge circuit in which two sets of cascaded switching elements 41, 42, 43, and 44 are connected in parallel with each other.

[0013] Furthermore, the inverter circuit 4 is provided with four capacitors 45, 46, 47, and 48. In the inverter circuit 4, capacitors 45 and 46, which are connected in series with each other, and capacitors 47 and 48, which are connected in series with each other, are connected in parallel with each other between the high-voltage line and the low-voltage line.

[0014] 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. Similarly, 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. Furthermore, the connection points between capacitor 45 and capacitor 46, and between capacitor 47 and capacitor 48, are each electrically connected to the primary coil 51 of the transformer 5 via a power line. As a result, the inverter circuit 4 and the primary coil 51, which is the input side of the transformer 5, are electrically connected via a power line, and the output control unit 3 controls the on / off state of the four switching elements 41, 42, 43, and 44, thereby outputting AC current from the inverter circuit 4 to the primary coil 51 of the transformer 5.

[0015] The secondary coil 52, which is the output side of the transformer 5, is electrically connected via power lines to two electrodes 71 and 72, which are provided on the cylinder block 61 and correspond to one side and the other side of the cylinder liner 62 in the axial direction of the cylinder 6. Electrode 71 is electrically connected to the cylinder block 61 (cylinder liner 62) corresponding to the crankcase side of the cylinder liner 62. Electrode 72 is electrically connected to the cylinder block 61 (cylinder liner 62) corresponding to the head gasket side of the cylinder liner 62. The secondary coil 52 of the transformer 5 is isolated from the DC power supply 2, which reduces the risk of current flowing outside the cylinder block 61 and causing noise.

[0016] In recent years, exhaust gas regulations for gasoline-engine vehicles have become stricter, and particular attention is being paid to addressing particulate matter. The cause of particulate matter in gasoline engines is that unvaporized fuel sprayed from the injector adheres to the walls of the cylinder 6. When this incomplete mixture is ignited, soot (particulate matter) is generated from the unburned gas. However, if the fuel adheres to the walls but vaporizes before ignition, creating a mixture that is 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, heating the cylinder liner 62. The Joule heat is calculated as R × I, where R is the resistance [Ω], I is the current [A], and P is the output [W]. 2 It is calculated by multiplying P[W] by time.

[0017] If a DC current is supplied directly from the DC power supply 2 to the cylinder liner 62, the current will not flow to the intended location on the cylinder liner 62. Therefore, an isolation power supply, isolated from the DC power supply 2 by a transformer 5 or the like, is used to supply current to the cylinder liner 62.

[0018] In addition, in order to pass an electric current through the cylinder liner 62 in a state floating from the DC power supply 2 by the transformer 5, an inverter circuit 4 for generating an alternating current is required. When the frequency of the alternating current is as low as about 50 to 60 [Hz], since the current also passes through the inside of the aluminum alloy cylinder block 61 and the cast iron cylinder liner 62 between the two electrodes 71 and 72, the resistance value between the two electrodes 71 and 72 becomes very low. Therefore, in order to obtain sufficient Joule heat, a large current is required. Moreover, since the resistance value between the two electrodes 71 and 72 is low, the current diffuses over a wide range other than between the two electrodes 71 and 72. On the other hand, by increasing the frequency of the alternating current to, for example, 20 [kHz], the skin effect appears, and the current flowing into the cylinder block is suppressed, and the current flows through the surface layer (the inner wall surface of the cylinder 6) of the cylinder liner 62. Then, since the energized area decreases, the resistance value between the two electrodes 71 and 72 increases, and it becomes possible to heat only the surface layer of the cylinder liner 62 with a smaller current than when the frequency is low (50 to 60 [Hz]).

[0019] In addition, in the cylinder heating device 1 according to the embodiment, since the current is directly passed through the cylinder liner 62 from the DC power supply 2 via the transformer 5 to heat the cylinder liner 62, the energy loss can be reduced as compared with the case of heating the cylinder liner 62 by passing an electric current through a separately provided electric heater.

[0020] In FIG. 1, an image of the current flow in the cylinder liner 62 is shown by a broken line arrow. Also, in FIG. 1, the amount of current is represented by the thickness of the line of the broken line arrow. By passing a current (alternating current) through the cylinder liner 62 at a high frequency, the skin effect occurs, and the current flows 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 decreases in terms of the volume resistivity, so the resistance value between the two electrodes 71 and 72 increases. When the resistance value between the two electrodes 71 and 72 is high, the current tries to pass through the shortest path with less resistance. Therefore, the amount of current flowing through the path deviated from the shortest path decreases.

[0021] In addition, due to the increase in the resistance value between the two electrodes 71 and 72 caused by the skin effect, the current flows through the shortest path between the two electrodes 71 and 72. Therefore, if the arrangement of the two electrodes 71 and 72 is optimized, it becomes possible to heat only the targeted part of the surface layer of the cylinder liner 62 (the inner wall surface of the cylinder 6) more efficiently.

[0022] FIG. 2 is a diagram showing a first example of the relationship between the positions of the electrodes 71 and 72 and the flow of current. FIG. 3 is a diagram showing a second example of the relationship between the positions of the electrodes 71 and 72 and the flow of current. FIG. 4 is a diagram showing a third example of the relationship between the positions of the electrodes 71 and 72 and the flow of current. Note that FIGS. 2(a), FIGS. 3(a) and FIGS. 4(a) are cross-sectional views of the cylinder 6. FIGS. 2(b), FIGS. 3(b) and FIGS. 4(b) represent the image of the current flow by a diagram in which the cylinder liner 62 is developed with broken line arrows.

[0023] As shown in FIGS. 2, FIGS. 3 and FIGS. 4, it can be seen that the way the current flows through the surface layer of the cylinder liner 62 (the inner wall surface of the cylinder 6) changes depending on the positions of the electrodes 71 (electrodes 71a and 71b) and the electrodes 72 (electrodes 72a and 72b).

[0024] FIG. 5 is a diagram showing a case where two secondary coils 52A and 52B are provided as the output side of the transformer 5 for two cylinders 6A and 6B. FIG. 6 is a diagram showing a case where one secondary coil 52 is commonly provided as the output side of the transformer 5 for two cylinders 6A and 6B.

[0025] In the cylinder heating device 1 according to this embodiment, the number of secondary coils 52 of the transformer 5 is the same as the number of cylinders 6 provided in the cylinder block 61. For example, as shown in Figure 5, two secondary coils 52A and 52B are provided as the output side of the transformer 5 for two cylinders 6A and 6B. Here, as shown in Figure 6, if one secondary coil 52 is electrically connected to both cylinders 6A and 6B as the output side of the transformer 5, the current will flow through the shortest path in the two cylinders 6A and 6B. That is, in adjacent cylinders 6A and 6B, for example, the current will flow through the shortest path inside the cylinder block 61A and 61B from the electrode 71B of cylinder 6B to the electrode 72A of cylinder 6A, and the current will not flow through the intended part of the surface layer of the cylinder liner 62A and 62B (the inner wall surface of cylinders 6A and 6B).

[0026] Therefore, in the cylinder heating device 1 according to this embodiment, as shown in Figure 5, the two cylinders 6A and 6B are each provided with isolated outputs (secondary coils 52A and 52B). This allows the secondary coil 52A to conduct current from electrode 71A, which is electrically connected to the cylinder liner 62A of cylinder 6A, towards electrode 72A, to the surface layer of the cylinder liner 62A (the inner wall surface of cylinder 6A). Similarly, the secondary coil 52B allows current to conduct from electrode 71B, which is electrically connected to the cylinder liner 62B of cylinder 6B, towards electrode 72B, to the surface layer of the cylinder liner 62B (the inner wall surface of cylinder 6B).

[0027] In the cylinder heating device 1 according to this embodiment, heat can be generated efficiently with respect to the input power because there is no conversion efficiency. Similar to induction heating, a high-frequency compatible inverter circuit 4 is required, but the output side is a transformer 5, eliminating the need to install a large coil inside the engine's water jacket, thus improving mountability. Furthermore, since the DC power supply 2 and GND are not shared (not electrically connected) and are isolated, current flows only between the two electrodes 71 and 72, making it difficult for current to flow outside the cylinder block (engine), thus reducing the impact of noise on the ECU and other components. In addition, since the surface of the piston located inside the cylinder 6 can also be a path for current to flow, if current can be passed to the piston surface via the piston rings, it becomes possible to heat the piston surface, making it possible to use it in center-injection direct injection engines as well. [Explanation of symbols]

[0028] 1. Cylinder heating device 2 DC power supply 3 Output control unit 4. Inverter Circuit 5 transformers 6, 6A, 6B Cylinders 51 Primary coil 52, 52A, 52B Secondary coil 61, 61A, 61B Cylinder Block 62, 62A, 62B Cylinder Liner 71,71a,71b,72,72a,72b electrode

Claims

[Claim 1] A DC power supply that outputs DC current, A power conversion device that converts the DC current output from the DC power supply into AC current, A transformer having a primary coil electrically connected to the power conversion device, and a secondary coil electrically connected to electrodes provided in the internal combustion engine, corresponding to one side and the other side of the cylinder liner in the axial direction of the cylinder, A cylinder heating device characterized by comprising the following features.

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