JP7835656B2 - Vehicle braking system - Google Patents

Description

This invention relates to a vehicle braking system.

Conventionally, electric vehicle brake systems are known that convert rotation from a motor, reduced in speed by a gearbox, into linear motion, pressing pads against the wheel discs.

For example, the electric brake device described in Patent Document 1 is a brake-by-wire system mounted on each wheel, and integrates a motor, a reduction gear, a linear motion converter, and an electronic circuit capable of controlling the motor's rotation.

During braking, the brake pads and discs reach high temperatures due to friction. The motor also generates heat, as does the power module in the output control unit's electronic circuitry. This can lead to the electronic components inside the device exceeding their heat resistance limits and potentially failing.

Japanese Patent Publication No. 2006-103562

Patent Document 1 describes how frictional heat during braking is suppressed by placing an insulating member made of a resin material with lower thermal conductivity than metal between the power module, the reducer, the motor, and the linear motion converter. On the other hand, to address heat generation in the power module, the electronic circuit is fixed to a metal plate, and another metal plate is placed opposite it, utilizing the high thermal conductivity of metal to improve heat dissipation.

However, in the electric brake device described in Patent Document 1, the reduction gear, motor, and linear motion converter are arranged very close together within the same housing. Therefore, simply placing an insulating material in between is insufficient to suppress heat conduction between the power module and the reduction gear, motor, and linear motion converter, and there is a risk that frictional heat during braking may be transmitted to the motor and reduction gear via the linear motion converter. Furthermore, the heat dissipation effect of metal alone may be insufficient to release heat generated by the electronic circuit. Moreover, no consideration is given to motor heat generation.

The object of the present invention is to provide a vehicle brake system that improves heat dissipation in view of the above-mentioned thermal problems.

The present invention relates to a vehicle braking device capable of restricting the rotation of a wheel (2) by pressing a pad (4) against a disc (3) that rotates together with the wheel, and comprises a motor (20), a reduction gear (30), a linear motion conversion unit (40), and a control circuit unit (60).

The motor rotates when power is supplied. The gearbox reduces the rotation from the motor and outputs it. The linear motion converter converts the rotation from the gearbox into linear motion, enabling the pad to press against the disc. The control circuit has an electronic circuit capable of controlling the rotation of the motor and the operation of the gearbox and linear motion converter.

At least a portion of the electrically conductive components of the motor or control circuit are covered with a material that has a higher thermal conductivity than air at room temperature . The motor's outer wall is composed of a motor housing (21). The control circuit's electronic circuits are housed in a circuit housing (61). The motor housing has multiple outside air intakes (26) along the circumferential direction at the same position in the axial direction of the motor. The circuit housing has multiple outside air intakes (66) along a direction perpendicular to the axial direction of the motor, on a plane parallel to the axial direction of the motor.

Air is a low-thermal-conductivity insulating medium; while it has a heat diffusion effect through convection, its heat dissipation is not particularly high. However, in recent years, polymer materials such as gels or resins with higher thermal conductivity than air have been developed and are becoming available for use. Therefore, in this invention, at least a portion of the heat-generating components of a motor or control circuit are covered with a high-thermal-conductivity material, and the space that was previously an air layer is replaced with a resin mold. This promotes smooth heat transfer from the heat-generating components to the outside of the device, thereby efficiently releasing heat.

This configuration ensures, for example, a continuous inflow of outside air from below. As a result, the heat generated by the device—specifically, the heat generated by the heat-generating components during braking, such as the discs and pads, motor, and electronic circuits of the control circuit—is more efficiently diffused within the resin mold than the air layer allows. This heat then moves to the outside air in the vicinity of the device and is smoothly discharged. Consequently, the heat from the motor and electronic circuits, along with the frictional heat generated during braking, is efficiently released, suppressing the temperature rise of the motor and electronic circuits during operation of the vehicle's braking system.

A plan view of a vehicle brake system according to one embodiment. A front view of a vehicle brake system according to one embodiment. A perspective view of a vehicle brake system according to one embodiment. A perspective view illustrating a resin mold for a motor according to one embodiment. A perspective view illustrating a resin mold for a control circuit according to one embodiment. A perspective view illustrating a resin mold for a control circuit according to another embodiment.

The following describes a vehicle brake system according to an embodiment, based on the drawings.

(One embodiment)
Figure 1 shows a schematic configuration of a vehicle brake device according to one embodiment. Its external appearance is shown in Figures 2-3. The vehicle brake device 10 is installed, for example, on the wheel 2 of a vehicle 1. The vehicle brake device 10 can restrict the rotation of the wheel 2 by pressing a pad 4 against a disc 3 that rotates together with the wheel 2. This makes it possible to maintain the stationary state of a stationary vehicle 1, or to decelerate or stop a moving vehicle 1.

The vehicle brake system 10 comprises a motor 20, a reduction gear 30, a linear motion converter 40, a control circuit 60, and the like. The motor 20 is, for example, a three-phase brushless motor, and rotates under the energization control of the circuit body 63, which will be described later. The reduction gear 30 is configured to reduce the rotation from the motor 20 when the shaft 24 of the motor 20 rotates, and output it to the linear motion converter 40. The linear motion converter 40 is configured to convert the rotation from the reduction gear 30 into linear motion, enabling the pad 4 to press against the disc 3. This allows the braking control state of the vehicle 1 by the vehicle brake system 10 to be maintained. The control circuit 60 is configured to control the rotation of the motor 20, the operation of the reduction gear 30, and the linear motion converter 40.

The vehicle brake system 10 comprises a motor housing 21, a reduction gear housing 31, and a circuit housing 61. The motor housing 21 houses the motor 20. The reduction gear housing 31 is formed, for example, as a bottomed cylindrical shape and houses the reduction gear 30. The circuit housing 61 is formed, for example, as a cylindrical shape and is located on the opposite side of the bottom of the reduction gear housing 31, housing the control circuit unit 60.

The motor 20 further includes a stator 22 fixed to the motor housing 21, a rotor 23 rotatably mounted relative to the stator 22, and a shaft 24 that rotates with the rotor 23 to output torque. When the rotor 23 rotates, rotation is output from the shaft 24.

In detail, the motor housing 21 is mounted in contact with the gearbox housing 31. The stator 22 is fixed to the inner wall of the motor housing 21. The shaft 24 is formed, for example, in a cylindrical shape. The rotor 23 is mounted coaxially with the shaft 24 at one end of the shaft 24. The other end of the shaft 24 is located inside the gearbox housing 31. The other end of the shaft 24 is supported inside the gearbox housing 31 via a bearing and a portion of the motor housing 21. Here, the bearing is, for example, a ball bearing. The motor 20 has a coil 25. The coil 25 is wound around the teeth of the stator 22.

The control circuit unit 60 includes a circuit housing 61, a circuit board 62, and a circuit body 63. The circuit board 62 is formed in a plate shape, for example, from resin, and is housed within the circuit housing 61. The circuit body 63 is an integrated circuit, such as a microcontroller, and is mounted on the side of the circuit board 62 facing the heat dissipation promotion section 611. Specifically, the circuit body 63 is a small computer containing a CPU, memory, input/output section, etc. Based on signals from various sensors attached to the vehicle 1, it controls the power supply to the motor 20's coil 25 and the reduction gear 30, thereby operating the motor 20 so that the rotor 23 rotates in the forward or reverse direction, and also operating the reduction gear 30.

All conductive components generate some heat when energized, but the circuit body 63 of the electronic circuit 60, in particular, is an integrated circuit with a dense concentration of heat-generating elements. Because the circuit body 63 controls the motor 20 by microscopically adjusting the current pattern, amount, and duration, a large amount of heat can be generated instantaneously, potentially leading to high temperatures. Therefore, it is necessary to quickly and efficiently dissipate the generated heat.

In this embodiment, the entire energized components of the motor 20 (coil 25, etc.) and the energized components of the control circuit unit 60 (circuit body 63, etc.) are resin-molded with a polymer material (high thermal conductivity gel or resin) that has a higher thermal conductivity than air (Figure 1). This allows the generated heat to diffuse more efficiently within the resin mold than in the case of no resin molding (heat diffusion through the air layer), and heat radiation from the resin mold moves the heat to the outside of the device, promoting heat dissipation. Hereafter, the resin mold of the energized components of the motor 20 will be referred to as resin mold 20M, and the resin mold of the energized components of the control circuit unit 60 will be referred to as resin mold 60M. Figures 4-5 show resin molds 20M and 60M.

In this embodiment, multiple outside air inlets 26 and 66 are provided in both the motor housing 21 and the circuit housing 61 (Figure 1-3). The outside air inlets 26 and 66 are designed to allow air from outside the device to enter and blow through the motor housing 21 and the circuit housing 61. This combination of a resin-molded heating element using a polymer material (high thermal conductivity gel or resin) with a higher thermal conductivity than air, and the introduction of outside air into the housing, promotes heat dissipation from the device.

Refer to Figure 3 below. The coil 25 of the motor 20 generates heat when energized. Especially during braking, if several phases generate significant heat due to the three-phase current entering an electrical lock state, the motor housing 21 becomes extremely hot. To quickly dissipate this heat, as described above, the entire coil 25 of the motor 20 is molded with a polymer material (high thermal conductivity gel or resin) with a higher thermal conductivity than air (resin mold 20M), and the motor housing 21 has multiple outside air inlets 26 on its outer surface. With this configuration, outside air A1 entering the motor housing 21 through the outside air inlets 26 travels along the resin mold 20M, receives heat from the resin mold 20M, and becomes "heated outside air A2," which then blows out to other outside air inlets 26, efficiently dissipating the heat released from the coil 25 via the resin mold 20M to the outside.

The heated outside air A2 expands due to the heat, increasing in volume compared to the outside air A1 before it was heated. Its specific gravity decreases, generating buoyancy, and it moves upward. The outside air intake section 26 is a void formed across the entire motor housing 21, including the top surface and the ground, and exhibits multiple slit-shaped openings. This ensures that, for example, outside air A1 continuously flows in from the lower, ground-side outside air intake section 26. The incoming outside air A1 is then heated by heat radiation from the resin mold 20M, becoming outside air A2, which is then smoothly and continuously discharged from other outside air intake sections 26.

In this embodiment, the continuous inflow of outside air A1 is ensured by mounting the vehicle brake device 10 on a vehicle 1 equipped with an air guide plate G that directs the outside air A1 toward the mounting position of the vehicle brake device 10. As a result, the outside air A1 guided by the air guide plate G flows, receives heat from the resin mold 20M, is heated, and then blows through. Here, the difference in the background patterns of outside air A1 and heated outside air A2 in Figure 3 reflects the gas density. That is, outside air A1 has a high density, while heated outside air A2 has a low density.

The conductive components of the control circuit unit 60 are also resin-molded with a polymer material (high thermal conductivity gel or resin) that has a higher thermal conductivity than air (resin mold 60M). The circuit housing 61 is provided with an outside air intake section 66. Similar to the outside air intake section 26, the outside air intake section 66 is a void formed throughout the circuit housing 61, exhibiting multiple slit-shaped openings. This configuration allows outside air A1 entering through the outside air intake section 66 to absorb heat from the resin mold 60M, becoming heated outside air A2, which then blows out to the opposite side of the motor housing 21, thus efficiently discharging the heat emitted from the resin mold 60M to the outside.

As described above, the heated outside air A2 expands due to the heat, generating buoyancy and moving upward. Therefore, by, for example, attaching it to a vehicle 1 equipped with an air guide plate G, and ensuring a continuous inflow of outside air A1 from below, the outside air A2 heated by heat radiation from the resin mold 60M is smoothly and continuously discharged to the outside of the device through the outside air intake section 26.

Furthermore, as in this embodiment, when the entire energized components of the motor 20 and control circuit unit 60 are resin-molded, not only is the aforementioned heat dissipation efficiency improvement effect (paragraph [0023]) achieved, but a waterproofing effect is also obtained, which reduces the rate of electrical short circuits caused by moisture or metallic foreign matter entering from the outside. This allows for simplification of the waterproofing structure, leading to further benefits such as simplification of the manufacturing process and weight reduction of the device due to a reduction in the number of parts.

(Other embodiments)
In the above-described embodiment, an example was shown in which the entire conductive components of the motor and control circuit are resin-molded. However, the extent to which the conductive components of the motor and control circuit are resin-molded is not limited to the above example, and in other embodiments, only a portion of the conductive components of the motor or control circuit may be resin-molded. For example, in the example shown in Figure 6, only the component of the conductive part of the control circuit that is expected to generate the most heat is resin-molded.

In the above embodiment, an example was shown in which both the motor and the conductive components of the control circuit are resin-molded. In contrast, in other embodiments, only one of the conductive components of the motor and the control circuit may be resin-molded.

In the above-described embodiment, an example was shown in which multiple outside air intakes are provided in both the motor housing and the circuit housing. In contrast, in other embodiments, multiple outside air intakes may be provided in only one of the motor housing or the circuit housing.

In the above-described embodiment, an example was shown where each outside air intake section exhibited multiple slit-shaped openings. However, the shape of the outside air intake section is not limited to the above example; in other embodiments, for example, it may exhibit multiple substantially circular openings, such as those found in perforated metal. In other words, the shape of the outside air intake section only needs to allow for the free flow of outside air into the device.

In other embodiments, the motor may be a motor other than a three-phase brushless motor.

The vehicle brake system of the present invention may be applied to all of the vehicle's wheels, or to only some of the wheels.

The vehicle brake device of the present invention can be used as a parking brake, as well as a braking device for slowing down or stopping a moving vehicle.

Thus, this disclosure is not limited to the embodiments described above, and can be implemented in various forms without departing from its essence.

2 wheels, 3 discs, 4 pads, 10 vehicle brake system, 20 motor,
30 Reducer, 40 Linear motion converter, 60 Control circuit

Claims (1)

A vehicle brake device capable of restricting the rotation of a wheel by pressing a pad (4) against a disc (3) that is rotatably mounted together with the wheel (2),
A motor (20) that rotates when power is applied,
A reduction gear (30) that reduces the rotation from the motor and outputs it,
A linear motion conversion unit (40) that converts the rotation from the reduction gear into linear motion and presses the pad against the disk,
A control circuit unit (60) having an electronic circuit capable of controlling the rotation of the motor, the operation of the reduction gear and the linear motion converter,
Equipped with,
At least a portion of the energized components of the motor or the control circuit are covered with a material that has a higher thermal conductivity than air at room temperature .
The motor's outer wall is composed of a motor housing (21).
The control circuit section comprises the electronic circuit housed in a circuit housing (61).
The motor housing is provided with a plurality of outside air inlet sections (26) along the circumferential direction at the same position in the axial direction of the motor.
The circuit housing is a vehicle brake device in which a plurality of outside air intake sections (66) are provided on a plane parallel to the axial direction of the motor, along a direction perpendicular to the axial direction of the motor .