Sensor-equipped axle unit having a built-in motor of in-wheel type

The present invention relates to an axle unit with a built-in in-wheel motor that combines a hub bearing, a speed reducer, and an electric motor, and particularly to a technique for controlling running stability in an electric vehicle.

In the future, it is expected that automobiles will shift from those driven by an engine to those driven by a motor in order to reduce the environmental load. Under such circumstances, an axle unit with a built-in in-wheel motor, which is a combination of a hub bearing, an electric motor, and a speed reducer, is attracting attention as a drive wheel bearing device for an electric vehicle (for example, Patent Documents 1 and 2). ). When this axle unit with a built-in in-wheel motor is used for the drive wheels of an electric vehicle, each drive wheel can be driven to rotate individually, eliminating the need for a large-scale power transmission mechanism such as a propeller shaft or differential, and reducing the weight of the vehicle. It can be made compact and compact.

In general wheel bearings used in engine-driven automobiles, suspension control, ABS (anti-lock braking system) control, and the like are used as control technologies related to the stability of vehicle body posture. In addition, various sensors attached to the vehicle body measure various states of the vehicle, and the engine, brakes, steering, etc. are controlled based on the measurement results.<patcit num="1"><text>Japanese Patent Application Laid-Open No. 2005-7914</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 5-332401 (Figs. 1 to 3)</text></patcit>

<p> Since motor drive has a faster torque response than engine drive, when the suspension control and ABS control are introduced into a motor-driven vehicle, the vehicle body posture is more stable than when it is introduced into an engine-driven vehicle. The sex can be secured. In order to improve the accuracy of suspension control and ABS control, it is necessary to accurately measure the force acting on the automobile and perform control based on the measurement results.</p><p> The force acting on the car is mainly generated between the tire and the road surface. The acting force includes the acting force in the traveling direction, the cornering force acting in the direction orthogonal to the traveling direction (force in the axial direction of the drive wheel), and the normal force acting in the direction orthogonal to the ground contact surface (vertical direction). have power. In addition, there are air resistance that depends on the running speed and air force due to natural wind, but these are constantly very small. Therefore, in order to control the posture stability of the vehicle body, it is sufficient to detect the force acting between the tire and the road surface in the three axial directions with good responsiveness.</p><p> However, measuring the force acting on the automobile with a sensor attached to the vehicle body as in the conventional case means measuring the vibration transmitted to the vehicle body via the suspension or the chassis, which causes a time lag in the measurement result. Therefore, if the measurement result is used for control, there is a problem that the response of control becomes slow.</p><p> An object of the present invention is to measure the force in three axial directions orthogonal to the ground contact point of the drive wheel and the road surface from the state of the component related to the drive stop of the automobile with high sensitivity, and to control the vehicle body posture stability of the automobile in the motor drive form. It is to provide an axle unit with a sensor with a built-in in-wheel motor that can perform the above with high accuracy. In the case of a motor-driven automobile, the components are tires, wheels, hubs, drive sources, and brakes.</p>

<p> In the axle unit with a sensor with a built-in in-wheel motor of the present invention, hub bearings, electric motors, reduction gears, and brakes are arranged coaxially with respect to the central axis of the drive wheels, and these hub bearings, electric motors, reduction gears, It is characterized by providing a sensor that measures the force in three axial directions orthogonal to the ground contact point of the drive wheel and the road surface from the state of at least one component of the brake. Here, the forces in the three axial directions are the acting force in the traveling direction, the cornering force acting in the direction orthogonal to the traveling direction (force in the axial direction of the drive wheel), and the normal acting in the direction orthogonal to the ground plane. It is a force (force in the vertical direction).</p><p> According to the configuration of the present invention, it is possible to measure the force in the three axial directions orthogonal to the ground contact point of the drive wheel and the road surface from the state of the component related to the drive stop of the automobile. The measurement results can be used for suspension control and ABS control. As a result, the posture during braking and cornering of the automobile is stabilized, and safety can be ensured.</p><p><u style="single">Before</u>Brake<u style="single">Is converted into a reciprocating linear motion of the rotational output of the electric motor for braking and transmitted to the brake pads as braking force.</u>Dynamic brake<u style="single">To.</u> If the brake is an electric brake, brake control is easy.</p><p>Further, the axle unit with a sensor having a built-in in-wheel motor is attached to the vehicle body via a suspension having a damping means that attenuates the force acting on the drive wheels and the ground contact point of the road surface and transmits the damping means to the vehicle body. It is electrically operated to change the degree of attenuation, and it is preferable that the output of the sensor is input to the means for controlling the degree of attenuation of the attenuation means. If the damping means of the suspension is electrically operated to change the degree of damping, the suspension can be easily controlled. The suspension is properly controlled by the output of the sensor.</p><p> Sen for measuring the force in the three axial directions<u style="single">With</u>Then, the current sensor that measures the current value of the electric motor<u style="single">A brake force sensor that measures the braking force acting on the brake and the brake is installed.</u>Ke<u style="single">, Said</u>Flow sensor output<u style="single">Compare and contrast both the force and the output of the braking force sensor to drive</u>Provided an estimation means to estimate the force in the direction of travel acting on the driving wheel and the ground contact point of the road surface.<u style="single">To.</u> Since the amount of current flowing through the electric motor differs depending on the magnitude of the force acting on the drive wheels and the grounding point of the road surface in the traveling direction, the relationship between the above-mentioned acting force and the amount of current can be obtained in advance by experiments or simulations. The magnitude of the acting force can be calculated. The estimation means calculates the force in the traveling direction acting on the ground contact point between the drive wheel and the road surface from the output of the current sensor from the relationship between the acting force and the amount of current that have been obtained and set in advance by experiments and simulations. To do. By obtaining the acting force in the traveling direction by this method, the acting force can be detected with high accuracy.</p><p><u style="single">Drive</u>Since the magnitude of the braking force acting on the brake differs depending on the magnitude of the force acting on the driving wheel and the ground contact point of the road surface in the traveling direction, the relationship between the above acting force and the braking force can be obtained in advance by experiments or simulations. , The magnitude of the above acting force can be calculated. Based on the relationship between the acting force and the braking force, which are obtained and set in advance by experiments and simulations, the estimation means uses the output of the braking force sensor to determine the force in the traveling direction acting on the ground contact point between the drive wheels and the road surface. calculate. By obtaining the acting force in the traveling direction by this method, the acting force can be detected with high accuracy.</p><p> As one of the sensors for measuring the force in the three axial directions, an axial strain sensor which is attached to the stationary side raceway ring of the hub bearing and measures the axial strain of the stationary side raceway ring is provided.<u style="single">, This axial strain sensor is a sensor composed of an axial portion along the axial direction and a radial portion whose wall thickness is thinned so that the rigidity is lower than that of the axial portion in an L shape. It is attached to the stationary side raceway ring via the attachment member, and the shaft</u>It is advisable to provide an estimation means for estimating the axial force of the drive wheels acting on the contact points between the drive wheels and the road surface from the output of the directional strain sensor. Since the change in the axial strain of the stationary side raceway ring differs depending on the magnitude of the axial force acting on the drive wheel and the ground contact point of the road surface, the relationship between the above acting force and the axial strain is used in experiments and simulations in advance. The magnitude of the above-mentioned acting force can be calculated by obtaining the above. The estimation means is based on the relationship between the acting force and the axial strain, which are obtained and set in advance by experiments and simulations, and the drive wheels act on the ground contact points between the drive wheels and the road surface by the output of the axial strain sensor. Calculate the axial force. By obtaining the acting force in the axial direction by this method, the acting force can be detected with high accuracy.</p><p> As one of the sensors for measuring the force in the three axial directions, the stationary side raceway ring of the hub bearing<u style="single">Take facing</u>Attached, a radial strain sensor is provided to measure the radial strain of the stationary side raceway ring.<u style="single">The hub bearing is a double-row rolling bearing, and the axial position of the double-row rolling bearing facing the radial strain sensor is a position on the outboard side of the rolling surface of the outboard side row. , Diameter</u>It is advisable to provide an estimation means for estimating the vertical force acting on the drive wheels and the ground contact point of the road surface from the output of the directional strain sensor. Since the change in the radial strain of the stationary side raceway ring differs depending on the magnitude of the vertical force acting on the drive wheel and the ground contact point of the road surface, the relationship between the above acting force and the radial strain is used in experiments and simulations in advance. The magnitude of the above-mentioned acting force can be calculated by obtaining the above. The estimation means is the vertical direction acting on the ground contact point between the drive wheel and the road surface by the output of the radial strain sensor from the relationship between the acting force and the radial strain, which are obtained and set in advance by experiments and simulations. Calculate the force. By obtaining the acting force in the vertical direction by this method, the acting force can be detected with high accuracy.</p>

<p> In the axle unit with a sensor with a built-in in-wheel motor of the present invention, hub bearings, electric motors, reduction gears, and brakes are arranged coaxially with respect to the central axis of the drive wheels, and these hub bearings, electric motors, reduction gears, A sensor is installed to measure the force in the three axes orthogonal to the ground contact point of the drive wheel and the road surface from the state of at least one component of the brake.<u style="single">The brake is an electric brake that converts the rotational output of the electric brake motor into a reciprocating linear motion and transmits it to the brake pad as a braking force. As a sensor for measuring the force in the three axial directions, the current of the electric motor A current sensor for measuring the value and a braking force sensor for measuring the braking force acting on the brake are provided, and the output of the current sensor and the output of the braking force sensor are compared and contrasted with each other to compare and contrast the drive wheel and the road surface. An estimation means for estimating the force in the traveling direction acting on the ground contact point of the above is provided, and an estimation means for estimating the axial force of the drive wheel and the drive wheel acting on the ground contact point of the road surface is provided from the state of the hub bearing. An estimation means was provided to estimate the vertical force acting on the drive wheels and the ground contact point of the road surface from the state of the hub bearing.</u>As a result, the force in the three axial directions orthogonal to the ground contact point of the drive wheel and the road surface is measured with high sensitivity from the state of the components related to the drive stop of the automobile, and the vehicle body posture stability control of the automobile in the motor drive form is accurately controlled. You can.</p>

1 to 9 show an embodiment of the present invention. First, the outline of this embodiment will be described together with FIG. This axle unit with a built-in motor built-in sensor has a hub bearing A that rotatably supports the hub of the drive wheel 70, an electric motor B as a rotation drive source, and a hub that reduces the rotation of the electric motor B. The speed reducer C for transmission and the brake D for applying braking force to the hub are arranged on the central axis O of the drive wheel 70. What we are saying here is that each component is not necessarily located on the central axis O, but that each component acts functionally on the central axis O. In this specification, the side that is closer to the outside of the vehicle in the vehicle width direction when attached to the vehicle is referred to as the outboard side, and the side that is closer to the center of the vehicle is referred to as the inboard side.

As shown in FIG. 2, the hub bearing A includes an outer member 1 having a double row of rolling surfaces 3 formed on the inner circumference and an inner member forming a rolling surface 4 facing each of these rolling surfaces 3. It is composed of 2 and a double-row rolling element 5 interposed between the rolling surfaces 3 and 4 of the outer member 1 and the inner member 2. The hub bearing A is a double-row angular contact ball bearing type, and the rolling element 5 is made of balls and is held by a cage 6 in each row. The rolling surfaces 3 and 4 have an arcuate cross section, and the rolling surfaces 3 and 4 are formed so that the contact angles are outward. The outboard side end of the bearing space between the outer member 1 and the inner member 2 is sealed with the seal member 7.

The outer member 1 is a stationary side raceway ring, and has a flange 1a on the outer circumference to be attached to the casing 33b on the outboard side of the speed reducer C, and the whole is an integral part. The flange 1a is provided with mounting holes 14 at a plurality of locations in the circumferential direction. The outer member 1 is attached to the casing 33b by a mounting bolt 15 inserted through the mounting hole 14.

The inner member 2 is a rotating side raceway ring, and is an outboard side member 9 having a hub flange 9a for mounting the drive wheel 70 and the brake wheel 46, and the outboard side member 9.<u style="single">Inside</u>The outboard side is fitted around the circumference, and the inboard side member 10 is integrated with the outboard side member 9 by crimping. The rolling surface 4 of each row is formed on the outboard side member 9 and the inboard side member 10. A through hole 11 is provided at the center of the inboard side member 10. The hub flange 9a is provided with press-fitting holes 17 for hub bolts 16 at a plurality of locations in the circumferential direction. Near the base of the hub flange 9a of the outboard side member 9, a cylindrical pilot portion 13 for guiding the drive wheel 70 and the brake wheel 46 projects toward the outboard side. A cap 18 for closing the outboard side end of the through hole 11 is attached to the inner circumference of the pilot portion 13.

The electric motor B is an axial gap type in which an axial gap is provided between the stator 23 fixed to the tubular casing 22 and the rotor 25 attached to the output shaft 24. The output shaft 24 is cantilevered by two bearings 26 in the cylinder portion of the casing 33a on the inboard side of the speed reducer C. The inboard end of the gap between the output shaft 24 and the casing 33a is sealed with a sealing member 27. A cap 28 is attached to the opening on the inboard side of the casing 22.

As shown in FIGS. 2 and 3, the reducer C is configured as a cycloid reducer. That is, in this speed reducer C, two curved plates 34a and 34b formed by a wavy trochoid curve having a gentle outer shape are mounted on the eccentric portions 32a and 32b of the input shaft 32 via the bearing 35, respectively. A plurality of outer pins 36 passed between the casings 33a and 33b on the inboard side and the outboard side guide the eccentric movement of each of the curved plates 34a and 34b on the outer peripheral side, and the inboard side member 10 of the inner member 2 A plurality of inner pins 38 attached to the above are inserted and inserted into a plurality of through holes 39 provided inside the curved plates 34a and 34b. The input shaft 32 is spline-coupled to the output shaft 24 of the electric motor B so as to rotate integrally with the output shaft 24. The input shaft 32 is supported by two bearings 40 on the casing 33a on the inboard side and the inner diameter surface of the inboard side member 10 of the inner member 2.

When the output shaft 24 of the electric motor B rotates, the curved plates 34a and 34b attached to the input shaft 32 that rotate integrally with the output shaft 24 perform eccentric movement. The eccentric motion of each of the curved plates 34a and 34b is transmitted as a rotational motion to the inner member 2 which is the hub of the wheel by the engagement between the inner pin 38 and the through hole 39. The rotation of the inner member 2 is decelerated with respect to the rotation of the output shaft 24. For example, a reduction ratio of 1/10 or more can be obtained with a one-stage cycloid reducer.

The two curved plates 34a, 34b are mounted on the eccentric portions 32a, 32b of the input shaft 32 with a phase shift of 180 ° so that the eccentric motions cancel each other, and on both sides of the eccentric portions 32a, 32b, A counterweight 41 eccentric in the direction opposite to the eccentric direction of the eccentric portions 32a and 32b is attached so as to cancel the vibration caused by the eccentric motion of the curved plates 34a and 34b.

As shown in FIG. 4, bearings 42 and 43 are mounted on the outer pins 36 and the inner pins 38, and the outer rings 42a and 43a of these bearings 42 and 43 are the outer circumferences and the outer circumferences of the curved plates 34a and 34b, respectively. It is designed to make a transition to the inner circumference of the through hole 39. Therefore, the contact resistance between the outer pin 36 and the outer circumferences of the curved plates 34a and 34b and the contact resistance between the inner pin 38 and the inner circumference of each through hole 39 are reduced, and the eccentric movement of the curved plates 34a and 34b is smoothed. It can be transmitted to the inner member 2 as a rotary motion.

As shown in FIG. 5, the brake D operates a brake wheel 46 attached to the hub flange 9a together with the drive wheel 70, an actuating portion 48 having a brake pad 47 capable of frictionally contacting the brake wheel 46, and a brake pad 47. It has a drive unit 49 to be driven, and is an electric brake using an electric brake motor 50 as a drive source of the drive unit 49. The brake wheel 46 consists of a brake disc. A pair of brake pads 47 are provided so as to sandwich the brake wheels 46. One brake pad 47 is fixed to the brake frame 51, and the other brake pad 47 is attached to an advancing / retreating member 52 linearly and retreatingly installed on the brake frame 51. The advancing / retreating direction of the advancing / retreating member 52 is the direction facing the brake wheel 46. The advancing / retreating member 52 is stopped from rotating with respect to the brake frame 51.

The drive unit 49 has the electric motor 50 for braking and a ball screw 53 that converts the rotational output of the electric motor 50 into a reciprocating linear motion and transmits it to the brake pad 47 as a braking force, and the output of the electric motor 50 is It is transmitted to the ball screw 53 via the deceleration transmission mechanism 58. In the ball screw 53, the screw shaft 54 is rotatably supported by the brake frame 51 via the bearing 57, and the nut 55 is fixed to the advancing / retreating member 52. The advancing / retreating member 52 and the nut 55 may be integrally integrated with each other.

The ball screw 53 has a screw shaft 54 and a nut 55, and a plurality of balls 56 interposed between the screw grooves formed so as to face the outer peripheral surface of the screw shaft 54 and the inner peripheral surface of the nut 55. The nut 55 has a circulation means (not shown) for circulating a ball 56 interposed between the screw shaft 54 and the nut 55 by an endless path. The circulation means may be an external circulation type using a return tube or a guide plate, or an internal circulation type using an end chap or a piece. Further, since the ball screw 53 reciprocates a short distance, a ball screw 53 having no circulation means, for example, a plurality of balls 56 between the screw shaft 54 and the nut 55 is used with a retainer (not shown). It may be a held retainer type.

The deceleration transmission mechanism 58 is a mechanism that decelerates and transmits the rotation of the electric motor 50 for braking to the screw shaft 54 of the ball screw 53, and is composed of a gear train. In this example, the deceleration transmission mechanism 58 includes a gear 59 provided on the output shaft of the electric motor 50 and a gear 60 provided on the screw shaft 54 and meshing with the gear 59. The deceleration transmission mechanism 58 may also include, for example, a worm and a worm foil (not shown).

The brake D has an operation unit 62 that controls the electric motor 50 according to the operation of an operation member 61 such as a brake pedal. The operation unit 62 is provided with anti-lock control means 65. The operation unit 62 includes the operation member 61, a sensor 64 capable of detecting the operation amount and the operation direction of the operation member 61, and a control device 63 that controls the electric motor 50 in response to the detection signal of the sensor 64. Therefore, the control device 63 is provided with the anti-lock control means 65. The control device 63 includes means for generating a motor control signal and a motor drive circuit (neither shown) capable of controlling the motor current by the motor control signal.

The anti-lock control means 65 is a means for preventing the rotation lock of the drive wheels 70 by adjusting the braking force of the electric motor 50 according to the rotation of the drive wheels 70 when braking by operating the operation member 61. The anti-lock control means 65 detects the rotation speed of the drive wheels 70 during the braking, and when the rotation lock of the drive wheels 70 or a sign thereof is detected from the detected speed, the drive current of the electric motor 50 is reduced, or A process of adjusting the braking force, that is, the tightening force of the brake pad 47 is performed by temporarily generating a reverse rotation output. The output of the rotation speed sensor 87 of the electric motor B, which will be described later, can be used to detect the rotation speed of the drive wheels 70.

As shown in FIG. 1, a drive wheel 70 is attached to the hub flange 9a of the hub bearing A together with the brake wheel 46. The drive wheel 70 has tires 72 provided around the wheel 71. With the brake wheel 46 sandwiched between the hub flange 9a and the wheel 71, the drive wheel 70 and the brake wheel 46 are hubbed by screwing the hub bolt 16 press-fitted into the press-fit hole 17 of the hub flange 9a to the wheel 74. It is fixed to the flange 9a.

This axle unit is fixed to the vehicle body (not shown) via a suspension 73 attached to the outer peripheral portion of the casing 22 of the electric motor B. The suspension 73 is provided with damping means 74 that attenuates the force acting on the drive wheels 70 and the ground contact point on the road surface and transmits the force to the vehicle body. The damping means 74 includes a damper, a shock absorber, and the like. The damping means 74 is electrically operated so that the degree of damping can be changed.

The force acting on the drive wheels 70 and the ground contact point on the road surface is a combination of a force Fx in the traveling direction orthogonal to each other, a force Fy in the axial direction of the drive wheels, and a force Fz in the vertical direction. The axle unit is provided with sensors that individually measure the forces in these three axial directions. The force Fx in the traveling direction is obtained from the output of the current sensor 80 that detects the current value I of the electric motor B. The axial force Fy of the drive wheel is obtained from the output of the axial strain sensor 81 that detects the axial strain εy of the outer member 1 which is the stationary side raceway ring of the hub bearing A. The vertical force Fz is obtained from the output of the radial strain sensor 82 that detects the radial strain εz of the outer member 1 which is the stationary side raceway ring of the hub bearing A.

As shown in FIG. 6, each of these sensors 80, 81, 82 is connected to an estimation means 83 and an abnormality determination means 84 that process the output of each sensor. These estimation means 83 and abnormality determination means 84 are provided in, for example, an electric control unit (ECU) 85 of an automobile. The estimation means 83 and the abnormality determination means 84 may be incorporated in an electronic circuit device (not shown) such as a circuit board provided for each axle unit. An electric motor B, an electric motor 50 of the brake C, and a damping means 74 of the suspension D are connected to the output side of the electric control unit 85.

Since the amount of current flowing through the electric motor B differs depending on the magnitude of the force acting on the drive wheel 70 and the grounding point of the road surface in the traveling direction, the relationship between the above acting force and the amount of current can be obtained in advance by experiments or simulations. , The magnitude of the above acting force can be calculated. Based on the relationship between the acting force and the amount of current that have been obtained and set in advance by experiments and simulations, the estimation means 83 uses the output of the electric motor 50 to act on the grounding points of the drive wheels and the road surface in the traveling direction. Is calculated.

Further, since the axial strain of the outer member 1 which is the stationary side raceway ring differs depending on the magnitude of the axial force acting on the drive wheel 70 and the ground contact point of the road surface, the above-mentioned acting force and the axial direction are obtained in advance. By obtaining the strain relationship by experiments or simulations, the magnitude of the above acting force can be calculated. Based on the relationship between the acting force and the axial strain that have been obtained and set in advance by experiments and simulations, the estimation means 83 is driven by the output of the axial strain sensor 81 to act on the ground contact points between the drive wheels and the road surface. Calculate the axial force of the wheel 70.

Further, since the change in the radial strain of the outer member 1 which is the stationary side raceway ring differs depending on the magnitude of the vertical force acting on the drive wheel 70 and the ground contact point of the road surface, the above-mentioned acting force and the radial strain are different in advance. By obtaining the relationship by experiment or simulation, the magnitude of the above acting force can be calculated. Based on the relationship between the acting force and the radial strain, which are obtained and set in advance by experiments and simulations, the estimation means 83 acts on the ground contact point between the drive wheel and the road surface by the output of the radial strain sensor 82. Calculate the force in the direction.

Based on the various information obtained in this way, the electric control unit 85 outputs an output for controlling the attitude of the vehicle. For example, the rotation speed of the left and right drive wheels 70 is controlled by outputting to the electric motor B so that the turning is performed smoothly. The brake D is output to the electric motor 50 to control braking so that the drive wheels 70 do not lock during braking. Suspension control is performed by outputting to the damping means 74 of the suspension 73 in order to prevent the vehicle body from tilting significantly to the left or right when turning, or tilting significantly back and forth during acceleration or braking. Further, the abnormality determining means 84 outputs an abnormality signal when it is determined that the force in the three axial directions exceeds the permissible value. This abnormal signal can also be used for vehicle control of an automobile. Furthermore, by outputting the acting force between the drive wheels and the road surface in real time, more detailed attitude control becomes possible.

The axial strain sensor 81 is installed as shown in FIGS. 7 to 9, for example. That is, the axial strain sensor 81 is attached to the sensor mounting member 92 to form the sensor unit 91, and the sensor unit 91 is fixed to the outer peripheral portion of the outer member 1 of the hub bearing A. The sensor mounting member 92 includes a first contact fixing portion 92a that is contact-fixed in the vicinity of the mounting hole 14 of the outer member 1 and a second contact fixing portion 92b that is contact-fixed to the outer peripheral surface of the outer member 1. have. Further, the sensor mounting member 92 includes a radial portion 92c including the first contact fixing portion 92a and an axial portion 92d along the axial direction including the second contact fixing portion 92b. It is configured in an L shape. The radial portion 92c is thinner than the axial portion 92d so that the rigidity is lower. The axial strain sensor 81 is attached to this low-rigidity radial portion 92c.

In the sensor unit 91, the first and second contact fixing portions 92a and 92b of the sensor mounting member 92 so that both contact fixing portions 92a and 92b are in the same phase with respect to the circumferential direction of the outer member 1. It is fixed to the outer peripheral portion of the outer member 1. When the first and second contact fixing portions 92a and 92b are in phase in the circumferential direction, the length of the sensor mounting member 92 can be shortened, so that the sensor unit 91 can be easily installed. The axial strain sensor 81 is fixed to the sensor mounting member 92 using, for example, an adhesive.

The sensor mounting member 92 has a shape and material that does not cause plastic deformation when fixed to the outer member 1. Further, the sensor mounting member 92 needs to have a shape that does not cause plastic deformation even when the maximum expected load is applied to the wheel bearing. The above assumed maximum force is the maximum force assumed in traveling that does not lead to a vehicle breakdown. This is because when the sensor mounting member 92 is plastically deformed, the deformation of the outer member 1 is not accurately transmitted to the sensor mounting member 92, which affects the measurement of strain.

The sensor mounting member 92 can be manufactured, for example, by press working. If the sensor mounting member 92 is a pressed product, cost reduction is possible. Further, the sensor mounting member 92 may be a sintered metal product obtained by metal powder injection molding. Metal powder injection molding is one of the molding techniques for metals, intermetal compounds, etc., and includes a step of kneading metal powder with a binder, a step of injection molding using this kneaded product, and a step of degreasing a molded product. The step of sintering the molded product is included. According to this metal powder injection molding, a sintered body having a higher sintering density than general powder metallurgy can be obtained, a sintered metal product can be manufactured with high dimensional accuracy, and mechanical strength is also high. There are advantages.

As the axial strain sensor 81, various ones can be used. For example, if the axial strain sensor 81 is composed of a metal foil strain gauge, considering the durability of this metal foil strain gauge, the sensor can be mounted even when the maximum expected load is applied to the wheel bearings. It is preferable that the amount of strain in the mounting portion of the axial strain sensor 81 in the member 92 is 1500 microstrain or less. For the same reason, when the axial strain sensor 81 is composed of a semiconductor strain gauge, the strain amount is preferably 1000 microstrain or less. When the axial strain sensor 81 is composed of a thick film sensor, the strain amount is preferably 1500 microstrain or less.

Since the sensor unit 91 including the sensor mounting member 92 and the axial strain sensor 81 mounted on the sensor mounting member 92 is mounted on the outer member 1, the sensor for axial load detection can be compactly installed. Since the sensor mounting member 92 is a simple component that can be mounted on the outer member 1, by mounting the axial strain sensor 81 on the sensor mounting member 92, mass productivity can be improved and the cost can be reduced.

When a load is applied to the inner member 2 which is the hub of the drive wheel 70 by the axial force acting on the drive wheel 70 and the ground contact point of the road surface, the outer member 1 is deformed via the rolling element 5 and the outer member 1 is deformed. The deformation is transmitted to the sensor mounting member 92 mounted on the outer member 1, and the sensor mounting member 92 is deformed. The strain of the sensor mounting member 92 is measured by the axial strain sensor 81. At this time, the radial portion 92c of the sensor mounting member 92 is deformed according to the deformation of the flange 1a of the outer member 1. In the case of this embodiment, the radial portion 92c has lower rigidity than the outer member 1, and the sensor mounting member 92 has an L-shape composed of a less rigid radial portion 92c and a more rigid axial portion 92d. Therefore, the strain is concentrated near the corner portion 92e on the radial portion 92c side between the radial portion 92c and the axial portion 92d, and appears as a larger strain than the outer member 1. That is, the strain generated between the radial portion 92c and the axial portion 92d is a transfer and expansion of the strain of the R portion 1b at the base end of the flange 1a. Since this strain is measured by the axial strain sensor 81, the strain of the outer member 1 can be detected with high sensitivity, and the strain measurement accuracy is improved. Further, since the axial force acting on the drive wheel 70 and the ground contact point of the road surface is calculated by the axial strain measured with high accuracy, the calculated axial force is also highly accurate.

The radial strain sensor 82 is installed as shown in FIGS. 10 to 12, for example. That is, the radial strain sensor 82 is attached to the sensor mounting member 94 to form the sensor unit 93, and the sensor unit 93 is fixed to the outboard side casing 33b of the speed reducer C. The sensor mounting member 94 is an elongated member whose tip is bent like a hook, and a radial strain sensor 82 composed of a displacement sensor is mounted on the tip of the sensor mounting member 94. The base of the sensor mounting member 94 is a contact fixing portion 94a for mounting on the casing 33b.

The sensor unit 93 is attached to the casing 33b by fixing the contact fixing portion 94a of the sensor mounting member 94 to the outboard side surface of the casing 33b with an adhesive or the like. In the case of this embodiment, the radial strain sensor 82 is a non-contact type displacement sensor such as a vortex current type, and the radial strain sensor 82 measures the radial displacement of the outer peripheral surface of the outer member 1. It is attached to the sensor unit 93 at a predetermined distance from the outer peripheral surface of the outer member 1. The axial position of the outer member 1 facing the radial strain sensor 82 is, for example, the vicinity of the rolling surface 3 in the outboard side row, or the position on the outboard side of the rolling surface 3. The portion of the outer member 1 on the outboard side of the rolling surface 3 has a relatively large radial deformation with respect to the load as compared with the other portions. The sensor mounting member 94 is made of a material having rigidity that does not deform due to an external force when the sensor unit 93 is mounted on the casing 33b.

As the displacement sensor for the radial strain sensor 82, in addition to the eddy current type, a magnetic type, an optical type, an ultrasonic type, a contact type or the like, or a sensor capable of detecting displacement of other types is used. be able to. An appropriate sensor may be selected according to various conditions.

Since the sensor unit 93 including the sensor mounting member 94 and the radial strain sensor 82 mounted on the sensor mounting member 94 is mounted on the outer member 1, the sensor for vertical load detection can be compactly installed. Since the sensor mounting member 94 is a simple component that can be mounted on the outer member 1, by mounting the radial strain sensor 82 on the sensor mounting member 94, mass productivity can be improved and the cost can be reduced.

When a load is applied to the inner member 2 which is the hub of the drive wheel 70 by the vertical force acting on the drive wheel 70 and the ground contact point of the road surface, the outer member 1 is deformed via the rolling element 5 and the outer member 1 is deformed. The radial displacement of the outer member 1 due to deformation is measured by the radial strain sensor 82 provided on the sensor mounting member 94 mounted on the outboard side casing 33b of the speed reducer C. At this time, since the outer peripheral surface of the outer member 1 to be measured is a portion that is largely displaced in the radial direction as compared with the surroundings, the radial displacement of the outer member 1 can be measured with high sensitivity. Further, since the vertical force acting on the drive wheel 70 and the ground contact point of the road surface is calculated by the radial strain measured with high accuracy, the calculated vertical force is also highly accurate.

In this embodiment, the case where the axial strain and the radial strain of the outer member 1 are measured by the axial strain sensor 81 and the radial strain sensor 82 has been described, but the axial strain sensor 81 and the radial strain sensor 82 have been described. Other components of the hub bearing A, such as the axial and radial strains of the inner member 2, may be measured. Further, in this embodiment, the inner member is a third generation type hub bearing that forms a part of the hub, but the inner member and the wheel hub are independent of each other in the first or second generation type hub. It may be used as a bearing. Further, it may be a hub bearing A which is a tapered roller type of each generation type.

For example, when this axle unit is provided on four wheels of an automobile and the four wheels are independently driven by an electric motor B, an algorithm for stabilizing the vehicle posture by detecting the rotation speed of each drive wheel 70 is constructed. To detect the number of rotations of the drive wheel 70, for example, a plurality of slits are provided on the outer diameter surface of the rotor 25 of the electric motor B, or a band-shaped mark is drawn and the light applied to the outer diameter surface of the rotor 25 is applied. A method can be used in which the reflected light is guided to the outside of the casing 22 by an optical fiber 86, and the intensity of the reflected light is measured by a rotation speed sensor 87 including a brightness meter. Since the inside of the casing 22 of the electric motor B is sealed and stains are unlikely to occur, measurement using light can be satisfactorily applied. An electromagnetic encoder-type detection method may be used to detect the rotation speed of the drive wheels 70.

In this axle unit, since the brake D is an electric brake that moves the brake pad 47 by the electric motor 50, it is possible to avoid environmental pollution due to oil leakage that occurs in the hydraulic brake. Further, since it is an electric brake, the amount of movement of the brake pad 47 can be quickly adjusted, and the responsiveness of the rotation speed control of the left and right drive wheels 70 at the time of turning can be improved.

Further, since this axle unit electrically operates the damping means 74 of the suspension 73, the responsiveness of the suspension control can be improved and the vehicle posture can be stabilized.

In the control system of the above embodiment, the force Fx in the traveling direction acting on the drive wheel 70 and the ground contact point of the road surface is obtained from the output of the current sensor 80 that detects the current value I of the electric motor B. As shown in the above, the force Fx in the traveling direction may be obtained from the output of the brake force sensor 88 that detects the braking force εd acting on the brake pad 47 of the brake D.

Since the magnitude of the braking force acting on the brake pad 47 of the brake D differs depending on the magnitude of the force acting on the drive wheel 70 and the ground contact point of the road surface in the traveling direction, the relationship between the above acting force and the braking force is tested or simulated in advance. The magnitude of the above-mentioned acting force can be calculated by obtaining the above. Based on the relationship between the acting force and the braking force, which are obtained and set in advance by experiments and simulations in this way, the estimation means 83 is a force in the traveling direction acting on the ground contact point between the drive wheels and the road surface by the output of the electric motor 50. Is calculated.

Further, as shown in FIG. 14, the force Fx in the traveling direction acting on the drive wheel 70 and the ground contact point of the road surface is the output of the current sensor 80 that detects the current value I of the electric motor B, and the brake pad 47 of the brake D. By comparing and contrasting both the outputs of the braking force sensor 88 that detects the braking force εd acting on the braking force εd, the detection accuracy of the force Fx in the traveling direction can be improved.

When the brake D is a hydraulic type, for example, a strain sensor is attached to a member that receives a load when a pressing force is applied to the brake pad, for example, a brake caliper, and the output of the strain sensor is applied to the contact point between the drive wheel and the road surface. It is possible to obtain the force in the direction of travel that acts.

In the above description, the drive of the electric motor B, the operation of the brake D, and the operation of the suspension 73 are controlled from the outputs of the sensors 80, 81, 82 that measure the forces acting on the drive wheels 70 and the road surface in the three axial directions. However, if each of the above controls including the signal from the steering device is performed, it is more desirable to perform the control according to the actual driving. Further, the axle unit of the present invention may be provided on all the wheels of the automobile, or may be provided on only a part of the wheels.

<figref num="1">It is a schematic diagram of the axle unit with an in-wheel type motor built-in sensor which concerns on embodiment of this invention.</figref><figref num="2">It is sectional drawing of the hub bearing, the reduction gear, and the electric motor of the axle unit.</figref><figref num="3">FIG. 2 is a sectional view taken along line III-III of FIG.</figref><figref num="4">It is sectional drawing which shows the main part of FIG. 3 enlarged.</figref><figref num="5">It is sectional drawing of the brake of the axle unit.</figref><figref num="6">It is a block diagram of a control system.</figref><figref num="7">It is the enlarged sectional view of the attachment part of the axial strain sensor of the axle unit.</figref><figref num="8">It is a front view which shows the outer member of a hub bearing, and the sensor unit for an axial strain sensor.</figref><figref num="9">(A) is a plan view of the sensor unit, and (B) is a side view thereof.</figref><figref num="10">It is the enlarged sectional view of the attachment part of the radial strain sensor of the axle unit.</figref><figref num="11">It is a front view which shows the outer member of a hub bearing, and the sensor unit for a radial strain sensor.</figref><figref num="12">(A) is a side view of the sensor unit, and (B) is a bottom view thereof.</figref><figref num="13">It is a block diagram of a different control system.</figref><figref num="14">It is a block diagram of a further different control system.</figref>

Code description

1 ... Outer member (fixed side raceway ring) 2 ... Inner member (hub) 3,4 ... Rolling surface 5 ... Rolling body 50 ... electric motor 70 ... drive wheels 73 ... Suspension 74 ... Attenuation means 80 ... current sensor 81 ... Axial strain sensor 82 ... Radial strain sensor 83 ... Estimating means 84 ... Abnormality judgment means 85 ... Electrical control unit 87 ... Rotation speed sensor A ... Hub bearing B ... Electric motor C ... reducer D ... Brake O ... central axis