CABLE CONNECTION STRUCTURE

A cable connection structure includes a cable including a power cable including a power line and a power shield line, a signal cable including a signal line and a signal shield line, a control unit including a control-side ground, and a controlled unit that includes a controlled-side ground, receives supply of power from the control unit, and exchanges the electric signals with the control unit. The power shield line and the signal shield line are connected to the control-side ground and the controlled-side ground. At least one of the power cable and the signal cable includes an earth line that connects the control-side ground and the controlled-side ground to each other.

TECHNICAL FIELD

A technique disclosed in the present specification relates to a cable connection structure, and in particular to a technique for suppressing transmission of noise from a power line to a signal line in a cable including the power line and the signal line.

BACKGROUND ART

Conventionally, for example, a technique disclosed in Patent Document 1 is known as a technique for suppressing transmission of noise from a power line to a signal line as described above. Patent Document 1 discloses a technique that suppresses noise in a cable used in an electric brake device of an automobile. In Patent Document 1, specifically, a technique is disclosed in which generation of noise in the signal line by the power line is suppressed, by constituting the power line by a twisted pair wire, constituting the signal line by a coaxial cable including a shield wire, and passing a DC current through the power line.

CITATION LIST

Patent Documents

SUMMARY OF INVENTION

Technical Problem

However, a DC brushless motor is often used in an electric brake device due to user-friendly control, and in such a case, high frequency noise may be generated by the power line to which an AC voltage is applied. For this reason, a technique for suppressing the influence on the signal line of high frequency noise that is generated by the power line is desired.

Furthermore, there are cases in which body earthing directly is difficult with a device that is provided outside of the vehicle body, such as a motor drive device used in an electric brake device. Accordingly, in such cases, a ground on the motor drive device side and a ground on the body side are connected via the power line and the shield line of the signal line, and a braided wire is used as the shield line in some cases. However, in the electric brake device, vibration stress may act on the braided wire due to vibration generated during driving of the vehicle, and the braided wire may be disconnected by the vibration stress. If the braided wire is disconnected, the shielding effect of the shield line will decrease and the function of the ground connection line will be lost. For this reason, a cable connection structure that can improve the reliability of ground connection and suppress the influence on a signal line of high frequency noise generated by a power line has been desired.

A technique disclosed in the present specification was made in view of the above circumstances, and provides a cable connection structure that can improve the reliability of ground connection and suppress the influence on a signal line of high frequency noise generated by a power line.

Solution to Problem

A cable connection structure disclosed in the present specification is a cable connection structure that connects a control unit and a controlled unit to each other, the cable connection structure including a cable including a power cable including a power line that supplies power and a power shield line that is formed by a braided wire and shields the power line, and a signal cable including a signal line that transmits electric signals and a signal shield line that is formed by a braided wire and shields the signal line, a control unit that is connected to one end of the power line and one end of the signal line, includes a control-side ground, and controls supply of the power and transmission of the electric signals, and a controlled unit that is connected to another end of the power line and another end of the signal line, includes a controlled-side ground, receives supply of power from the control unit, and exchanges the electric signals with the control unit, and the power shield line is connected to the control-side ground and the controlled-side ground, the signal shield line is connected to the control-side ground and the controlled-side ground, and at least one of the power cable and the signal cable includes an earth line that connects the control-side ground and the controlled-side ground to each other.

According to this configuration, in addition to the power shield line and the signal shield line, an earth line is provided to at least one of the power cable and the signal cable, as a ground connection line. For this reason, even in cases such as where the ground connection function between the control unit and controlled unit may be lost due to disconnection of both the power shield line and the signal shield line, for example, the ground connection function can be maintained by the earth line. Furthermore, due to the earth line, it is possible to suppress the influence on the signal line of high frequency noise generated by the power line. For this reason, with the cable connection structure according to this configuration, it is possible to improve the reliability of ground connection and suppress the influence on the signal line of high frequency noise generated by the power line.

In the above-described cable connection structure, both the power cable and the signal cable may include the earth line.

With this configuration, both the power cable and the signal cable include the earth line. Accordingly, the reliability of ground connection can be further improved, and the influence on the signal line of high frequency noise generated by the power line can be further suppressed.

Furthermore, in the above-described cable connection structure, the earth line may be formed by an insulated wire, and arranged inside the power shield line and the signal shield line.

With this configuration, since the earth line is arranged inside the shield line, the earth line is protected by the shield line. In this manner, the reliability of the earth line is improved, and consequently, the reliability of the cable connection structure can be improved.

Furthermore, in the above-described cable connection structure, a configuration is also possible in which the controlled-side ground includes a power ground to which the other end of the power line and the earth line are connected, and a signal ground to which the other end of the signal line and the earth line are connected, and the power ground and the signal ground are individually provided to be separated from each other.

With this configuration, the power ground and the signal ground are individually provided to be separated from each other in the controlled unit. For this reason, compared to a case in which the power ground and the signal ground are provided in common, it is possible to suppress a case in which high frequency noise generated by the power line affects the signal line via the ground on the controlled unit-side.

Furthermore, in the above-described cable connection structure, a configuration is also possible in which the control unit is an electric brake control unit that is provided inside a vehicle body of a vehicle, and controls an electric brake actuator of the vehicle, and the controlled unit is the electric brake actuator provided outside the vehicle body of the vehicle.

With this configuration, the cable connection structure is applied to a cable that connects an electric brake control unit provided inside the vehicle body and an electric brake actuator provided outside the vehicle body to each other. In this case, vibration stress acts on the braided shield line of the cable due to vibration during driving of the vehicle, and the braided shield line may be disconnected due to the vibration stress. However, even if the braided shield line is disconnected, the earth line can ensure the function of the ground connection line, and the influence on the signal line of high frequency noise generated by the power line can be suppressed.

Advantageous Effects of Invention

According to the cable connection structure disclosed in the present specification, it is possible to improve the reliability of ground connection and suppress the influence on a signal line of high frequency noise generated by a power line.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a cable connection structure1according to an embodiment will be described with reference toFIGS. 1 to 8. The cable connection structure1of the present embodiment is a connection structure of a cable2that connects an electric brake control unit10mounted in an automobile and an electric brake actuator20to each other. In other words, the present embodiment illustrates an example in which the cable connection structure1is applied to an electric brake of an automobile, that is, a so-called EMB (Electro-Mechanical Brake).

1. Configuration of Cable Connection Structure

As shown inFIG. 1, the cable connection structure1includes the cable2, the electric brake control unit10, and the electric brake actuator20. Here, the electric brake control unit10is an example of a “control unit”. Also, the electric brake actuator20is an example of a “controlled unit”. Hereinafter, the electric brake actuator20is merely referred to as “the actuator20”.

The cable2includes a power cable30, a signal cable40, and a sheath3. The cable2is fixed to a vehicle body60with a prescribed grommet4.

The power cable30includes a power line31, a power shield line32, and a power earth line (corresponds to earth line)35. Power is supplied from the electric brake control unit10to the actuator20through the power line31.

The power shield line32is constituted by a braided wire, and one end32A thereof is connected to a ground15(hereinafter, referred to as “control-side ground”) of the electric brake control unit10. Another end32B of the power shield line32is connected to a power ground25P that is an actuator ground25(corresponds to controlled-side ground), and covers and shields the power line31.

The power line31is constituted by, for example, three insulated core wires. In other words, in the present embodiment, three-phase power is supplied to the actuator20through the power line31. Note that the configuration is not limited thereto, and, for example, the power line31may be constituted by a single core wire, and DC power may be supplied to the actuator20.

As shown inFIG. 1, the power earth line35is arranged inside the power shield line32, and connects the control-side ground15and the power ground25P (an example of the controlled-side ground) to each other. The power earth line35is a coated wire (insulated wire), and is constituted by, for example, a single core wire having a cross sectional area of approximately 2.5 mm2(sq.) and an insulating coating that covers the core wire.

On the other hand, the signal cable40includes a signal line41, a signal shield line42, and a signal earth line45(corresponds to earth line). The signal line41transmits electric signals between the electric brake control unit10and the actuator20. The electric signals include, for example, various types of control signals to be sent to the actuator20, various types of sensor signals to be received from the actuator20, and the like.

Similarly to the power shield line32, the signal shield line42is constituted by a braided wire, and one end42A thereof is connected to the control-side ground15. Another end42B of the signal shield line42is connected to a signal ground25S that is the actuator ground25, and covers and shields the signal line41. The signal line41is constituted by, for example, twelve core wires, and the core wires are covered with an insulating coating (not shown) and insulated.

The signal earth line45is provided inside the signal shield line42and connects the control-side ground15and the signal ground (an example of the controlled-side ground)25S to each other. Similarly to the power earth line35, the signal earth line45is a coated wire (insulated wire), and is constituted by a single core wire having a cross sectional area of approximately 2.5 mm2(sq.) and an insulating coating that covers the core wire, for example.

As described above, in the present embodiment, the earth lines (35and45) are arranged inside the shield lines (32and42), respectively, and thus the earth lines (35and45) are protected by the shield lines (32and42). In this manner, the reliability of the earth lines (35,45) is improved, and consequently, the reliability of the cable connection structure1can be improved.

The sheath3is constituted by an insulative tape, for example, and covers the power cable30and the signal cable40by winding with gaps between windings, or with half-overlapping windings.

Note that there is no limitation to the earth lines (35and45) being arranged inside the shield lines (32and42), respectively. For example, the earth lines (35and45) may be arranged between the shield lines (32and42) and the sheath3, respectively.

The electric brake control unit10is provided inside the vehicle body60. The electric brake control unit10is connected to one end31A of the power line and one end41A of the signal line, includes the control-side ground15, and controls power supply to the electric brake actuator20and transmission of the electric signals. Additionally, the electric brake control unit10includes an inverter (not shown) that generates three-phase power.

Specifically, the electric brake control unit10includes, for example, a power control unit11, a signal control unit12, and the control-side ground15. The power control unit11includes an output terminal11A and a ground terminal11B. The output terminal11A is connected to the one end31A of the power line, and the ground terminal11B is connected to the control-side ground15via a ground wiring13, for example. On the other hand, the signal control unit12includes an output terminal12A and a ground terminal12B. The output terminal12A is connected to the one end41A of the signal line, and the ground terminal12B is connected to the control-side ground15via a ground wiring14, for example.

Furthermore, in the electric brake control unit10, the one end32A of the power shield line32is connected to the control-side ground15via a ground wiring33, and the one end42A of the signal shield line42is connected to the control-side ground15via a ground wiring43. The control-side ground15is connected to the vehicle body60. In other words, the control-side ground15is connected to a body earth. Note that any configuration of the ground wirings (13,14,33, and43) can be employed, such as any length, for example.

On the other hand, the actuator20is provided outside the vehicle body60. The actuator20is connected to another end31B of the power line and another end41B of the signal line, exchanges electric signals with the electric brake control unit10and electrically acts on a disc brake51of a tire50.

Specifically, the actuator20includes, for example, a motor control unit21, a communication unit22, an actuator ground25, a motor26, and an accommodation box20A. As shown inFIG. 1, the actuator ground25is separated into the power ground25P of a power system and the signal ground25S of a signal system. Note that the configuration of the actuator ground25is not limited thereto, and the actuator ground25may be formed integrally rather than being separated into the power ground25P and the signal ground25S. Additionally, the actuator20includes various types of sensors, gears, a brake pad, a caliper, and the like (not shown).

The motor control unit21includes an input terminal21A and a ground terminal21B. The input terminal21A is connected to the other end31B of the power line, and the ground terminal21B is connected to the power ground25P via the ground wiring23, for example. On the other hand, the communication unit22includes an input terminal22A and a ground terminal22B. The input terminal22A is connected to the other end41B of the signal line, and the ground terminal22B is connected to the signal ground25S via a ground wiring24, for example.

The motor26is connected to the motor control unit21, and causes the brake pad (not shown) to act on the disc brake51by rotational force. In the present embodiment, the motor26is a DC brushless motor, for example. The motor control unit21receives a three-phase driving voltage from the electric brake control unit10, and supplies three-phase driving voltage to the motor26. Note that the configuration is not limited thereto, and the motor26may also be a DC brushless motor with built-in inverter. At this time, a DC voltage is supplied from the electric brake control unit10. Furthermore, the motor26is not limited to a DC brushless motor.

Furthermore, in the actuator20, the other end32B of the power shield line32is connected to the power ground25P via a ground wiring34, for example, and the other end42B of the signal shield line42is connected to the signal ground25S via a ground wiring44. Note that any configuration of the ground wirings (23,24,34, and44) can be employed, such as any length, for example.

In this way, in the present embodiment, the cable connection structure1is applied to a configuration in which the ground25of the actuator20(controlled unit) is placed in a state apart from the ground15of the electric brake control unit10(control unit), and the connection between the control-side ground15and the actuator ground25is carried out by the shield lines (32and42). At this time, in the present embodiment, the power ground25P of the actuator20is connected to the control-side ground15of the electric brake control unit10via the power shield line32and the power earth line35. Similarly, the signal ground25S of the actuator20is connected to the control-side ground15via the signal shield line42and the signal earth line45.

Additionally, the effect of suppressing noise transmission from the power line31to the signal line41in the present embodiment was confirmed through simulation described hereinafter.

2. Simulation Test of Noise Transmission from Power Line to Signal Line

Next, a simulation test of noise transmission from the power line to the signal line will be described with reference toFIGS. 2 to 8.

As shown inFIG. 2, the basic configuration of the simulation test was as follows: in the case where shield lines SH1and SH2were provided to a power line L1and a signal line L2, respectively, a length K1of the shield lines SH1and SH2was 1400 mm; a length K2of the sheath tape TA that covers the power line L1and the signal line L2, that is, the length for which the power line L1and the signal line L2run parallel to each other, was 900 mm. Ground wirings GL1and GL2were provided at the ends of the shield line SH1, and ground wirings GL3and GL4were provided at the ends of the shield line SH2. A ground GND was constituted by a copper plate.

The power line L1was a single line having a cross sectional area of approximately 2.5 mm2(sq.), and the signal line L2was a single line having a cross sectional area of 1.25 mm2, and both of the lines L1and L2were coated by insulating coating parts (not shown). Furthermore, the power line L1and the signal line L2were integrated by a sheath tape TA. Note that any configuration of the ground wirings (GL1to GL4) can be employed, such as any length, for example. Additionally, coated copper wires having a cross sectional area of approximately 2.5 mm2(sq.) were used for earth lines EL1and EL2.

Additionally, a test signal of 0 dBm (1 mW) power was input to one end (control unit side) of the power line L1, and the other ends (actuator side) of the power line L1and the signal line L2were terminated by 50Ω resistors. At this time, a spectrum analyzer SA was connected to the control unit side of the signal line L2and the power induced in the signal line L2by crosstalk was measured. Note that the test signals were sine waves, and were scanned at a frequency between approximately 10 KHz and 1 GHz. Additionally, in simulation modes M1and M5, the ground GND on the control unit side and the ground GND on the actuator side were electrically connected and integrated by a prescribed connection line or the like.

In the simulation mode M1, simulation was performed with a configuration in which the shield lines SH1and SH2were not provided and the power line L1and the signal line L2were covered only with the sheath tape TA, as shown inFIG. 3.

The result of the simulation mode M1is indicated by a curved line M1inFIG. 8. In this case, it is shown that the level of noise induced in the signal line L2is the highest of the simulations.

In the simulation mode M2, the shield lines SH1and SH2were not provided, and the earth line EL1was provided in proximity to the power line L1, and the earth line EL2was provided in proximity to the signal line L2, as shown inFIG. 4. Simulation was performed with a configuration in which ends on one side of the earth lines EL1and EL2were connected to the ground GND on the control unit side, and the ends on the other side of the earth lines EL1and EL2were connected to the ground on the actuator side. Note that a power ground GP and a signal ground GS on the actuator side were not connected on the actuator side, but were connected on the control unit side via the earth lines E1and E2, and via the ground GND. Note that “being proximity to” also includes being in contact with. In other words, the earth line EL1may be provided in contact with the power line L1, and the earth line EL2may be provided in contact with the signal line L2.

The result of the simulation mode M2is indicated by a curved line M2inFIG. 8. In this case, a noise level reduction effect was achieved in a frequency domain of 1 MHz to 100 MHz, compared to the simulation mode M1. In other words, a noise level reduction effect due to the earth lines EL1and EL2in a case where the shield lines SH1and SH2were not provided was confirmed.

In the simulation mode M3, only the shield lines SH1and SH2were provided, as shown inFIG. 5. Simulation was performed with a configuration in which the both ends of the shield lines SH1and SH2were connected to the ground on both sides, and the power ground GP and the signal ground GS were not connected on the actuator side. In this configuration, the power ground GP and the signal ground GS were provided common (integrated) to the ground GND on the control unit side by the shield lines SH1and SH2.

The result of the simulation mode M3is indicated by a curved line M3inFIG. 8. In this case, it was confirmed that the level of noise induced in the signal line L2was reduced the most of the simulations across substantially the whole frequency range.

In the simulation mode M4, the shield lines SH1and SH2and the earth lines EL1and EL2were provided as shown inFIG. 6. Simulation was performed with a configuration in which both ends of the shield lines SH1and SH2and the earth lines EL1and EL2were connected to the ground on both sides, and the power ground GP and the signal ground GS were not connected on the actuator side. This configuration is a configuration in which the power ground GP and the signal ground GS are provided in common (integrated) to the ground GND on the control unit side through the shield lines SH1and SH2and the earth lines EL1and EL2, and corresponds to the present embodiment.

The result of the simulation mode M4is indicated by a curved line M4inFIG. 8. In this case, it was confirmed that the level of noise induced in the signal line L2was reduced to substantially the same level as the simulation mode M3in a frequency domain up to substantially 20 MHz. In other words, the earth line EL1was provided in proximity to the power line L1, and the power line L1and the earth line EL1were shielded by the shield line SH1. In addition, the earth line EL2was provided in proximity to the signal line L2, and the signal line L2and the earth line EL2were shielded by the shield line SH2. In this configuration, the power ground GP and the signal ground GS were not connected, in other words, were provided individually, on the actuator side.

Note that it was confirmed that in a frequency domain of greater than or equal to 20 MHz, the effect of noise level reduction is small compared to that of the simulation mode M3.

In the simulation mode M5, simulation was performed on the assumption that disconnection WB has occurred in the shield lines SH1and SH2in the case where the control-side ground and the actuator-side ground are connected to each other in the simulation mode M3, as shown inFIG. 7.

The result of the simulation mode M5is indicated by the curved line M5inFIG. 8. In this case, as shown inFIG. 8, it was confirmed that the result is substantially close to that of the simulation mode M1. In other words, if the disconnection WB occurs due to the shield lines SH1and SH2, the reduction effect of the noise level caused by the shield lines SH1and SH2can be mostly obtained. Note that, from the results of the simulation mode M1and the simulation mode M2, it is conceivable that, in the simulation mode M5, if the earth lines EL1and EL2are provided (corresponds to the present embodiment), a noise level reduction effect by the earth lines EL1and EL2close to the result of the simulation mode M2can be obtained.

In other words, from the results of above simulations, it was confirmed that, in the present embodiment, even if disconnection occurs in the shield lines (32and42), the connection between the control-side ground15and the actuator ground25is ensured by the earth lines (35and45), and predetermined noise level reduction effects can be obtained.3. Effects of Present Embodiment

The cable connection structure1according to the present embodiment can be applied to a configuration in which the ground25of the actuator20(controlled unit) is placed in a state apart from the ground15of the electric brake control unit10(control unit), and the control-side ground15and the actuator ground25are connected to each other by the shield lines (32and42).

In this case, according to the cable connection structure1of the present embodiment, the power earth line35is provided to the power cable30, and the signal earth line45is provided to the signal cable40as the ground connection lines that connect the control-side ground15and the actuator ground25to each other, aside from the power shield line32and the signal shield line42. For this reason, even if disconnection occurs in both the power shield line32and the signal shield line42, and the ground connection function of the electric brake control unit10(control unit) and the electric brake actuator20(controlled unit) is lost, the ground connection function will be maintained by the earth lines (35and45). In addition, the earth lines (35and45) can suppress the influence on the signal line41of high frequency noise generated by the power line31. For this reason, with the cable connection structure1according to the present embodiment, it is possible to improve the reliability of ground connection and to suppress the influence on the signal line41of high frequency noise generated by the power line31.

Also, in the present embodiment, the actuator ground (controlled-side ground)25includes the power ground25P and the signal ground25S, and the power ground and the signal ground are individually provided to be separated from each other. Accordingly, compared to the case where the power ground and the signal ground are integrated, it is possible to suppress a situation where high frequency noise generated by the power line31affects the signal line41via the controlled-side ground.

Furthermore, in the present embodiment, the cable connection structure1is applied to the cables (30and40) that connect the electric brake control unit10provided inside the vehicle body and the electric brake actuator20provided outside of the vehicle body to each other. In this case, vibration stress acts on the braided shield lines (32and42) of the cable (30and40) due to vibrations during driving of the vehicle, and the braided shield lines (32and42) may conceivably disconnect due to the vibration stress. However, even if the braided shield lines (32and42) are disconnected, the ground connection function between the electric brake control unit10and the electric brake actuator20is ensured by the earth lines (35and45). It is also possible to suppress the influence on the signal line41of high frequency noise generated by the power line31.

Other Embodiments

The present invention is not limited to the embodiment described above with reference to the drawings, and the following embodiments are also encompassed within the technical scope of the present invention, for example.

(1) The above embodiment described an example in which the earth lines (35and45) are provided to both the power cable30and the signal cable40, but the present invention is not limited thereto. For example, the earth line may be provided only to the power cable30, or the earth line may be provided only to the signal cable40, on the basis of the possibility of disconnection of the shield lines, the effect of noise reduction, and the like. In short, it is sufficient that the earth line is provided to at least one of the power cable and the signal cable.

(2) The above embodiment described an example in which the cable connection structure according to the present application is applied to an electric brake of an automobile (EMB), with the control unit as the electric brake control unit10, and the controlled unit as the electric brake actuator20, but the present invention is not limited thereto. For example, the cable connection structure can also be applied to an in-wheel motor of an automobile, a side mirror camera of an automobile, and the like. Furthermore, the application is not limited to a vehicle such as an automobile. In other words, the cable connection structure according to the present application can be applied to any configuration in which a ground part of a controlled unit is placed in a state apart from an ground part of a control unit, and the ground part of the control unit and the ground part of the controlled unit are connected via a shield line.

LIST OF REFERENCE NUMERALS

1Cable connection structure2Cable10Electric brake control unit (control unit)15Control-side ground20Electric brake actuator (controlled unit)25Actuator ground (controlled-side ground)25P Power ground (controlled-side ground)25S Signal ground (controlled-side ground)30Power cable31Power line31A One end of power line31B Other end of power line32Power shield line32B Other end of power shield line35Power earth line (earth line)40Signal cable41Signal line41A One end of signal line41B Other end of signal line42Signal shield line42A One end of signal shield line42B Other end of signal shield line45Signal earth line (earth line)