DC motor having conduction suppression mechanism of electromagnetic wave noise

Abstract

To reduce electromagnetic wave noise radiated from a motor to the outside by suppressing spatial conduction of radiation emission generated from a contact between a commutator and a carbon brush of a DC motor.SOLUTION: A DC motor includes a radiation noise suppression mechanism that is provided in an end cap of a motor and suppresses electromagnetic wave noise generated in a sliding contact unit between a commutator and a pair of brushes. The radiation noise suppression mechanism includes a first ground terminal and a second ground terminal of an EMC filter circuit. The first ground terminal is a ground on a substrate of the EMC filter circuit connected to a ground cable, and includes an antenna portion extending so as to surround the sliding contact unit between the brush and the commutator. The second ground terminal is a ground with the motor case as reference potential. The first ground terminal and the second ground terminal are connected to each other via low-impedance wiring and an antenna.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a DC motor equipped with a mechanism for suppressing the conduction of electromagnetic noise, and more particularly to a mechanism for suppressing the conduction of electromagnetic noise intended for small DC motors suitable for electric actuators in automobiles, etc. [Background technology]

[0002] Small DC motors equipped with commutators have carbon brushes and commutators as electrical and mechanical contacts, so when the brushes and commutator switch, sparks can occur at the contact points between the commutator and the brushes, which can cause electromagnetic noise. Various mechanisms for suppressing the conduction of electromagnetic noise have been proposed to eliminate this spark discharge, or in other words, surges.

[0003] For example, Patent Document 1 discloses a configuration in which a pair of capacitors of a noise prevention circuit are installed in a motor case via the base and branch pieces of an earth terminal (ground terminal). The earth terminal is held in the flat wall of the end cap, and is configured to maintain its ability to suppress electromagnetic noise for a long period of time and to be highly reliable.

[0004] Furthermore, in Patent Document 2, in order to provide reliable countermeasures against electromagnetic noise, a ground terminal is electrically connected between multiple capacitors, and at least a portion of the ground terminal is arranged in the arrangement space between the side surface of the brush holder and the inner wall of the yoke housing, with the yoke connection portion of this ground terminal configured to abut against the yoke housing. This allows the ground terminal to abut reliably against the inner wall of the yoke housing, making it easy to ground.

[0005] Furthermore, Patent Document 3 discloses a configuration in which a brush holder is provided with a shielding portion including an insulating magnetic material for blocking high-frequency radiation noise generated during motor rotation, surrounding the sliding contact portion between the commutator and the power supply brush around the motor shaft. With this configuration, the shielding portion, which is provided on the brush holder and includes an insulating magnetic material for blocking high-frequency radiation noise, surrounds the sliding contact portion between the commutator and the power supply brush, which is the main source of high-frequency radiation noise, around the motor shaft, making it possible to easily and efficiently reduce the adverse effects of high-frequency radiation noise on the outside. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7379786 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-025679 [Patent Document 3] Patent No. 4824506 Summary of the Invention [Problem to be solved by the invention]

[0007] By installing an EMC filter circuit as a noise prevention circuit between the carbon brushes and power lines of a DC motor and ensuring a reliable connection between this EMC filter circuit and the ground terminal, the radiated emissions generated from the contact points between the commutator, which is a noise source, and the carbon brushes can be significantly reduced. However, according to the inventor's experiments, it is possible that some of the radiated emissions generated from the noise source pass through the space around the commutator and are spatially conducted to exposed conductive parts of the power line, such as the power terminals, and are not properly guided to the EMC filter circuit, resulting in electromagnetic noise being radiated from the motor to the outside. Alternatively, some of the electromagnetic noise may be spatially conducted from the noise source directly into the EMC filter circuit without passing through the choke coil, causing the noise prevention circuit to not function effectively and resulting in electromagnetic noise being radiated from the motor to the outside.

[0008] An object of the present invention is to suppress the spatial conduction of radiated emissions generated from the contact points between the commutator and the carbon brushes, which are noise sources, and to reduce the electromagnetic noise radiated from the motor to the outside. [Means for solving the problem]

[0009] According to one aspect of the present invention, there is provided a DC motor comprising a commutator fixed to a rotating shaft and a pair of brushes in sliding contact with the commutator, the rotating shaft being rotatably supported by a metal motor case and end caps made of an insulating material, A pair of brush holders are provided inside the end cap, and the pair of brushes are connected to a pair of power supply terminals for power supply via a power supply line, a choke coil, and an EMC filter circuit, a radiation noise suppression mechanism provided in the end cap for suppressing electromagnetic noise generated at a sliding contact portion between the commutator and the pair of brushes; the radiation noise suppression mechanism includes a first ground terminal and a second ground terminal of the EMC filter circuit, the first ground terminal is a ground on a substrate of the EMC filter circuit connected to a ground cable, and has an antenna portion extending to surround the sliding contact portion between the brush and the commutator, the second ground terminal is a ground with the motor case as a reference potential, The first ground terminal and the second ground terminal are connected via a low-impedance wiring and the antenna portion.

[0010] According to one aspect of the present invention, the first ground terminal (signal ground connected to the ground cable) and the second ground terminal (frame ground (motor case)) of the EMC filter circuit are connected via low-impedance wiring and an antenna unit. The antenna unit of the first ground terminal receives spatially conducted electromagnetic noise generated from a noise source and transmits this noise wave to the ground cable via the ground terminal unit. This suppresses spatial conduction of radiated emissions generated from the contact point between the commutator and the carbon brush, which is a noise source, and reduces electromagnetic noise radiated to the outside from the motor.

[0011] According to another aspect of the present invention, the radiation noise suppression mechanism includes a shield cover, and the shield cover covers the power line, the choke coil, the EMC filter circuit, and the power supply terminal for power feeding. the first ground terminal has a connection end portion to the substrate, the antenna portion, a ground terminal portion to be connected to a ground cable, and a shield cover holding portion, The shield cover holding portion is inserted into the shield cover and has a function of restraining and holding the shield cover against the motor case and the end cap within the end cap. This ensures a reliable electrical connection between the shield cover and the first ground terminal, and suppresses spatial conduction of electromagnetic noise generated from the shield cover and the noise source to the EMC filter circuit. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a longitudinal sectional view of a DC motor provided with a mechanism for suppressing the transmission of electromagnetic noise according to a first embodiment of the present invention. [Figure 2] 2 is a longitudinal cross-sectional view taken along the line AA in FIG. 1, showing an end cap assembly equipped with a mechanism for suppressing the transmission of electromagnetic noise. [Figure 3] 3 is a perspective view showing the end cap assembly of FIG. 2 with the shield cover removed. FIG. [Figure 4] 3 is a circuit diagram showing an example of the configuration of an EMC filter circuit, a first ground terminal, and a second ground terminal incorporated in the mechanism for suppressing the conduction of electromagnetic noise according to the first embodiment. FIG. [Figure 5] FIG. 2 is a perspective view showing details of a connection structure of a printed circuit board (PCB) and its first and second ground terminals. [Figure 6] 10 is a perspective view showing the relationship between an electromagnetic noise conduction suppression mechanism and a first ground terminal in an end cap assembly. FIG. [Figure 7] FIG. 10 is a plan view of the end cap with the shielding cover removed, showing the end cap assembly incorporating the first ground terminal. [Figure 8] FIG. 8 is a rear view of the end cap of FIG. 7. [Figure 9] 4 is a vertical cross-sectional view showing the relationship between the second ground terminal, the shield cover, and the motor case. FIG. [Figure 10] 10 is a vertical cross-sectional perspective view of the end cap, showing the relationship between the first ground terminal and the shield cover in detail. FIG. [Figure 11] FIG. 10 is a diagram illustrating a problem that arises when an EMC filter circuit is not connected to a motor case, as a first comparative example. [Figure 12] FIG. 10 is a diagram illustrating a problem that occurs when, as a comparative example 2, an EMC filter circuit is connected to a motor case via a second ground terminal at a location separate from the connector inside the motor case. [Figure 13] 10A and 10B are diagrams illustrating the effect of connecting an EMC filter circuit to a motor case via a second ground terminal near a connector inside the motor case, as in the present invention. [Figure 14] FIG. 2 is an explanatory diagram of conduction emissions of a DC motor according to an embodiment of the present invention. [Figure 15A] FIG. 10 is a diagram showing an example of measurement data of horizontally polarized radiation emissions of a DC motor according to an embodiment of the present invention. [Figure 15B] FIG. 10 is a diagram showing an example of measurement data of horizontally polarized radiation emissions in a DC motor of a comparative example. [Figure 16A] FIG. 10 is a diagram showing an example of measurement data of vertical conduction emissions of a DC motor according to an embodiment of the present invention. [Figure 16B] FIG. 10 is a diagram showing an example of measurement data of radiated emissions in the vertical direction in a DC motor of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a DC motor according to the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal cross-sectional view of a DC motor equipped with an electromagnetic noise transmission suppression mechanism according to a first embodiment of the present invention. The DC motor 1 includes a motor case 2 made of a metal such as iron, which is cup-shaped and has one open end. An end cap 3 made of an electrically insulating material, such as resin, is fixed to the open end of the motor case. A magnet 6, which constitutes the stator of the DC motor, is fixed to the motor case 2. The rotor of the DC motor, consisting of a laminated core 8 and an armature winding 7, is integrally formed with a rotating shaft 4, which is rotatably supported by the motor case 2 and the end cap 3 via a pair of bearings 5A and 5B. The laminated core 8 is circumferentially polarized with multiple poles, and the ends of the armature winding 7 are connected to a commutator 9. A pair of carbon brushes 10, connected to power supply terminals 23A and 23B for power supply and held by a brush holder 11, make sliding contact with the commutator 9. Reference numeral 28 denotes a shield cover made of a conductive material for suppressing the transmission of electromagnetic noise.

[0014] Fig. 2 is a longitudinal cross-sectional view taken along the line AA in Fig. 1, showing the configuration of an end cap assembly 20 equipped with a mechanism for suppressing the transmission of electromagnetic noise provided inside the end cap. Fig. 3 is a perspective view of the end cap, showing a state in which the shield cover 28 in Fig. 2 is seen through. An end cap assembly 20 provided inside the end cap 3 includes a pair of brush holders 11 and a pair of coil springs 19 that apply pressure to the carbon brushes 10. The carbon brushes 10 are connected to the armature windings 7 of the DC motor 1, and are connected to power supply terminals 23A and 23B for power supply via a pigtail 21, choke coils 25A and 25B, and an EMC filter circuit 27, which constitute a power supply line. The EMC filter circuit 27 is also connected to a first ground terminal 30 and a second ground terminal 31. As shown in Figures 2 and 3, the pair of choke coils 25A and 25B, the EMC filter circuit 27, the pair of power supply terminals 23A and 23B for power supply, the first ground terminal 30, and the second ground terminal 31, which constitute the power supply line, are covered with a shield cover 28 made of a conductive material. This structure aims to improve electromagnetic wave shielding characteristics by covering the EMC filter circuit 27 and other components with a shield cover 28 made of a conductive material to electromagnetically isolate them from the sliding contact points between the brushes 10, which are noise sources, and the commutator 9. This shield cover 28 is in contact with the inside of the motor case 2 and is fixed to the end cap 3 while connected to the first ground terminal 30. This ensures a reliable electrical connection between the shield cover 28 and the first ground terminal 30, and suppresses spatial conduction of electromagnetic noise generated from the shield cover 28 and the noise source to the EMC filter circuit 27.

[0015] FIG. 4 is a circuit diagram showing an example configuration of an EMC filter circuit 27, a first ground terminal 30, and a second ground terminal 31 incorporated in the electromagnetic noise conduction suppression mechanism according to the first embodiment. The EMC filter circuit 27 is a circuit in which the following elements constituting an IC filter circuit are mounted on a printed circuit board (PCB) 33: capacitors C1, C2, C3, a CMC (Common Mode Coil), C5, and a varistor or TVS (Transient Voltage Suppressor). The TVS is a voltage clamp-type surge protection element that absorbs and reduces surge voltages. C5 is an X2Y capacitor with two capacitors built into a single component. The EMC filter circuit 27 is configured to function as a common-mode filter. The CMC has high impedance for common modes and therefore effectively suppresses common-mode noise. Furthermore, a common-mode filter using an X2Y capacitor has characteristics different from those of a typical common-mode choke coil and exhibits high noise suppression effects, particularly for high-impedance circuits. The terminals 23C and 23D are connected to a pair of choke coils 25A and 25B. The signal ground SG corresponding to the first ground terminal 30 is a ground on the substrate 33 of the EMC filter circuit, and is a ground that serves as the reference potential for circuit operation on the substrate. The frame ground FG corresponding to the second ground terminal 31 is a ground that uses the motor case 2 as its reference potential, which allows for a larger ground area and makes it less susceptible to noise being carried to the ground. The signal ground SG and frame ground FG are connected on the printed circuit board (PCB) 33 by a thick, short electrical wiring 32 with low impedance.

[0016] Next, FIG. 5 is a perspective view showing the details of the connection structure between the printed circuit board (PCB) 33 and the first and second ground terminals 30 and 31. As shown in FIG. The first ground terminal 30 has a connection end 302 to a printed circuit board (PCB) 33, an antenna portion 304, a ground terminal portion 306 connected to a ground cable G (terminal G in FIG. 13), and a shield cover holding portion 308 fixed to the shield cover 28. The ground terminal portion 306 and the shield cover holding portion 308 extend linearly. Terminals 23A to 23D connected to the EMC filter circuit 27 are provided at both upper corners of both surfaces of the printed circuit board (PCB) 33. A second ground terminal 31 is fixed to one surface of the printed circuit board (PCB) 33, and its tip is fixed to an F terminal 23F corresponding to a frame ground FG of the EMC filter circuit 27. This F terminal 23F is connected to a G terminal 23G corresponding to a signal ground SG via a wiring 32 inside the printed circuit board (PCB). A connection end 302 of the first ground terminal 30 is connected to this G terminal 23G.

[0017] FIG. 6 is a perspective view showing the relationship between the electromagnetic noise transmission suppression mechanism and the first ground terminal 30 in the end cap assembly 20. As shown in FIG. FIG. 7 is a plan view of the end cap assembly with the shield cover removed, showing the electromagnetic noise transmission suppression mechanism incorporating the first ground terminal 30. The first ground terminal 30 is fixed to the end cap 3 so that its approximately arc-shaped antenna portion 304 is positioned within the space outside the outer periphery of the commutator 9. The antenna portion 304 has the function of receiving spatially conducted electromagnetic noise generated from a noise source and transmitting this noise wave to the ground cable G via the ground terminal portion 306. This makes it possible to significantly suppress spatially conducted electromagnetic noise to the EMC filter circuit.

[0018] Fig. 8 is a rear view of the end cap of Fig. 7. Power supply terminals 23A, 23B and ground terminal portion 306 of the first ground terminal extend in their longitudinal direction to the outside of end cap 3. Ground terminal portion 306 is connected to an external ground cable via connector 34 (see Fig. 13).

[0019] 9 is a vertical cross-sectional view showing the relationship between the second ground terminal 31, the shield cover 28, and the motor case 2. One end of the second ground terminal 31 is electrically connected to the F terminal 23F corresponding to the frame ground FG of the printed circuit board (PCB) 33 via an electrode portion 312 on the underside of the shield cover 28. The other end of the second ground terminal 31 is electrically connected to the inner circumferential surface of the motor case 2 via an electrode portion 314.

[0020] 10 is a vertical cross-sectional perspective view of the end cap, showing the detailed relationship between the first ground terminal 30 and the shield cover 28. The roughly arc-shaped antenna portion 304 of the first ground terminal is fixed to the end cap 3 so as to fit along the outer periphery of the commutator 9. The shield cover holding portion 308 of the first ground terminal 30 is inserted into a groove or the like provided in the shield cover 28, and has the function of restraining and holding the shield cover 28 relative to the motor case 2 and the end cap 3.

[0021] Next, the functions and effects of the present invention will be described. In the present invention, the EMC filter circuit 27 is covered with a shield cover 28 made of a conductive material that is connected to the metal part of the motor case 2. This allows electromagnetic noise generated from the noise source to be short-circuited to the ground terminal, thereby suppressing spatial conduction to the EMC filter circuit 27. Furthermore, electromagnetic noise may be transmitted through space to the exposed portion of the power terminal. In the present invention, the substantially arc-shaped antenna portion 304 of the first ground terminal is provided in close proximity to the noise source, i.e., surrounding the sliding contact portion between the brush 10 (the noise source) and the commutator 9. This allows electromagnetic noise generated at the sliding contact portion to be conducted via the ground terminal to the external ground cable in the shortest distance, thereby reducing the spatial conduction of electromagnetic noise.

[0022] The present invention is further characterized in that the signal ground SG (GND-1) on the printed circuit board (PCB) 33 and the frame ground FG (motor case 2) are connected by a thick and short electrical wiring 32. The actions and effects of the present invention will be described in more detail below.

[0023] 11 is a diagram illustrating a comparative example 1 that illustrates the problem that occurs when the EMC filter circuit in the PCB 33 is not connected to the motor case 2. A circuit board (PCB) 33 is placed inside the motor case 2 (chassis), and the ground terminal SG of this PCB 33 is connected to a ground cable G (Terminal G) via a ground terminal (GND-1) in a connector 34. VG is the noise voltage generated on the signal ground of the PCB 33. In this case, because the signal ground (GND-1) and frame ground (motor case 2) are not connected, the noise current generated in the signal ground passes through the ground cable (Terminal G), and the noise is conducted and radiated from the cable. There is stray capacitance Cf1 between the ground cable G and the frame, and there is stray capacitance Cf2 between the PCB (EMC filter circuit) and the frame (motor case). The noise current flows from the signal ground of PCB33 via the ground cable G, Cf1, frame ground (motor case), Cf2, and signal ground, and when the noise current flows through the ground cable (Terminal G), the noise is conducted and radiated.

[0024] Next, Figure 12 is a diagram illustrating a comparative example 2 that illustrates the issues that arise when the EMC filter circuit in PCB 33 is connected to motor case 2 via the second ground terminal (GND-2) at a location away from connector 34 inside the motor case. In this case, the signal ground (GND-1) of PCB33 is connected to the frame ground (motor case 2) via the second ground terminal on the side opposite the ground cable G, i.e., at the location of stray capacitance Cf2 in Comparative Example 1, resulting in the same phenomenon as in Comparative Example 1. In other words, noise current in the loop between the signal ground of PCB33 and the frame ground flows more easily, increasing conducted and radiated noise. If we consider the frame ground as the reference ground, this structure is the same as the monopole antenna shown in the lower right of Figure 12. This monopole antenna has a structure in which one element of a dipole antenna is connected to a large ground such as the housing or the ground. In this way, the frame ground (motor case 2) is effective in shielding noise, but if the connection location with the signal ground is poor, as in Comparative Example 2, the noise will actually increase.

[0025] 13 is a diagram illustrating the effect of connecting an EMC filter circuit to a motor case 2 via a second ground terminal (GND-2) near the connector 34 inside the motor case 2, as in the present invention. In this example, the signal ground SG (GND-1) on the printed circuit board (PCB) 33 and the frame ground FG (motor case 2) are connected by a thick and short electrical wiring 32. In other words, the signal ground and the frame ground are connected by a thick and short wiring to achieve low impedance. When the signal ground SG and the frame ground FG are connected near the ground cable (Terminal G), as in the present invention, noise current passes through the frame ground FG and is less likely to flow into the ground cable G.

[0026] Next, FIG. 14 is an explanatory diagram of conduction emissions of a DC motor according to an embodiment of the present invention. Electromagnetic radiation noise generated at the sliding contact between the commutator 9 and the brushes 10 travels through the power line to the EMC filter circuit 27, where it is reduced. It is believed that the exposed parts near the power terminals 23A and 23B act as antennas and receive the electromagnetic noise generated at the sliding contact between the commutator 9 and the pair of brushes 10 as radiation noise. When the power terminals or the like act as antennas and receive radiation noise, it is believed that noise is induced in common mode. It is also believed that the exposed parts of the EMC filter circuit 27 receive radiation noise.

[0027] According to the embodiment of the present invention, the exposed portions near the power supply terminals 23A and 23B and the EMC filter circuit 27 are covered with the shield cover 28, and the first ground terminal 30 and the second ground terminal 31 are electrically connected by the short wiring 32 and the substantially arc-shaped antenna portion 304. This reduces the electromagnetic noise that reaches the EMC filter circuit 27 directly from the noise source without passing through the power supply line. This reduces the noise that needs to be processed by the EMC filter circuit 27, and as a result, reduces the noise that is radiated via the power supply line 35 to electronic devices outside the motor, such as an on-board ECU.

[0028] Next, the effects of the present invention will be described based on measurement data with reference to FIGS. 15A to 16B. First, Fig. 15A is a diagram showing an example of measurement data of horizontal radiation emissions in the frequency band of 1 GHz to 2.5 GHz for a DC motor according to an embodiment of the present invention. Fig. 15B is a diagram showing an example of measurement data of horizontal radiation emissions in the frequency band of 1 GHz to 2.5 GHz for a DC motor according to a comparative example. Note that the DC motor according to the comparative example is an example in which the EMC filter circuit in PCB 33 is connected to motor case 2 via the second ground terminal (GND-2) at a location away from connector 34 inside the motor case, as shown in Fig. 12. In the DC motor of the present invention, the radiated emissions show values ​​around 30 to 40 Field Strength. On the other hand, in the DC motor of the comparative example, the radiated emissions show values ​​mainly around 40 to 50 Field Strength. As such, the DC motor of the example of the present invention has significantly reduced horizontal radiated emissions compared to the DC motor of the comparative example. In other words, it is recognized that there is a noise suppression effect.

[0029] Next, Fig. 16A is a diagram showing an example of measurement data of radiated emissions in the vertical direction in a frequency band of 1 GHz to 2.5 GHz for a DC motor according to an example of the present invention, and Fig. 16B is a diagram showing an example of measurement data of radiated emissions in the vertical direction in a frequency band of 1 GHz to 2.5 GHz for a DC motor according to a comparative example. In the DC motor of the present invention, the radiated emissions show values ​​around 30 to 40 Field Strength. On the other hand, in the DC motor of the comparative example, the radiated emissions show values ​​mainly around 40 to 60 Field Strength. As such, in the DC motor of the example of the present invention, the value of radiated emissions in the vertical direction is significantly reduced compared to the DC motor of the comparative example. In other words, it is recognized that there is a noise suppression effect. [Explanation of symbols]

[0030] 1 DC motor 2 Motor case 3 End Caps 4 rotation axes 6. Magnets 7 Armature Winding 8 Laminated core 9 commutator 10 Carbon Brush 11 Brush holder 20 End Cap Assembly 21 Pigtail 23 Power terminal 25 Choke coil 27 EMC filter circuits 28 Shield cover 30 First ground terminal 304 Antenna part 31 Second ground terminal 32 Wiring 33 PCB

Claims

1. A DC motor comprising: a commutator fixed to a rotating shaft; and a pair of brushes in sliding contact with the commutator, the rotating shaft being rotatably supported by a metal motor case and end caps made of an insulating material, a pair of brush holders are provided in the end cap, and the pair of brushes are connected to a pair of power supply terminals for power supply via a power supply line, a choke coil, and an EMC filter circuit; a radiation noise suppression mechanism provided in the end cap for suppressing electromagnetic noise generated at a sliding contact portion between the commutator and the pair of brushes; the radiation noise suppression mechanism includes a first ground terminal and a second ground terminal of the EMC filter circuit, the first ground terminal is a ground on a substrate of the EMC filter circuit connected to a ground cable, and has an antenna portion extending to surround the sliding contact portion between the brush and the commutator, the second ground terminal is a ground with the motor case as a reference potential, The DC motor is characterized in that the first ground terminal and the second ground terminal are connected via a low-impedance wiring and the antenna portion.

2. In claim 1, The first ground terminal is fixed to the end cap so that the antenna portion is positioned within a space around the commutator.

3. In claim 1, the radiation noise suppression mechanism includes a shield cover, the shield cover covers the power supply line, the choke coil, the EMC filter circuit, and the power supply terminal for power supply, the first ground terminal has a connection end portion to the substrate, the antenna portion, a ground terminal portion to be connected to a ground cable, and a shield cover holding portion, a shield cover holding portion that is inserted into the shield cover and has the function of restraining and holding the shield cover against the motor case and the end cap within the end cap;

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