Electric brake device

Abstract

An electric brake device (10) includes a torque difference calculation section (94) that calculates a difference between a first command torque and a second command torque, i.e., a plus-minus pressure torque difference, the first command torque being a command torque for a first period that is a period in which a change trend of the command torque for an electric motor (40) changes from one of an increasing trend and a decreasing trend to the other, the second command torque being a command torque for a second period that is a period in which a pressing force applied to a rotating body 110 starts to change from the first period due to a change trend of the command torque being maintained, and an efficiency estimation section that estimates an efficiency of the electric brake device (10) based on the first command torque or the second command torque and the plus-minus pressure torque difference, the efficiency of the electric brake device (10) being a ratio of a difference between the command torque and a proportional loss torque to the command torque.

Description

Technical Field

[0001] This invention relates to an electric braking device. Background Technology

[0002] Patent Document 1 describes an electric braking device that generates braking force on the wheel by pressing a friction material against a rotating body that rotates together with the wheel. The electric braking device includes an electric motor and a direct-acting conversion mechanism. The direct-acting conversion mechanism has a rotating part that rotates according to the rotational motion of the output shaft of the electric motor, and a direct-acting part that moves linearly according to the rotational motion of the rotating part. The electric braking device presses the friction material against the rotating body through the direct-acting part, which moves linearly based on the power transmitted from the electric motor. Thus, the electric braking device generates braking force on the wheel. In this way, in the electric braking device, the torque output by the electric motor is converted into the force of the friction material pressing against the rotating body.

[0003] Patent Document 1: U.S. Patent Application Publication No. 2014 / 0303865

[0004] Electric braking systems involve mechanical losses, so not all the torque output by the electric motor is converted into pressing force from the friction material. When the efficiency of an electric braking system is defined as the proportion of the electric motor's output torque converted into pressing force, this efficiency sometimes decreases over time due to changes in the system's characteristics. Therefore, if the efficiency of the electric braking system can be estimated, values ​​related to the pressing force of the direct-acting component can be corrected. For example, the electric braking system can adjust the torque command value for the electric motor or the estimated pressing force of the direct-acting component based on its efficiency. Summary of the Invention

[0005] In the electric braking device that solves the above-mentioned problem, the rotating part of the direct-acting conversion mechanism rotates according to the rotational motion of the electric motor. This rotational motion is converted into linear motion in the forward or backward direction of the direct-acting part of the direct-acting conversion mechanism. Based on this linear motion, friction material is pressed against a rotating body that rotates together with the vehicle's wheel, thereby applying braking force to the wheel. The electric braking device includes a torque difference calculation unit that calculates the difference between a first command torque and a second command torque, i.e., the difference between the acceleration and deceleration torques. The first command torque is the command torque in a first period, which is the period during which the command value of the electric motor's torque, i.e., the trend of the command torque change, changes from one trend of increase or decrease to the other. The second command torque is the torque in a second period... The second period is the period from the first period onwards when the pressing force applied to the rotating body begins to change due to the maintenance of the changing trend of the command torque; and the efficiency estimation unit estimates the efficiency of the electric braking device based on the first command torque or the second command torque and the difference between the pressure increase and decrease torques. The efficiency of the electric braking device is the ratio of the difference between the command torque and the proportional loss torque to the command torque, wherein the larger the command torque, the larger the proportional loss torque. The proportional loss torque is the difference between the command torque in the ideal electric braking device without mechanical loss and the command torque in the electric braking device with mechanical loss, which is the torque output by the electric motor when a specified pressing force is applied to the rotating body.

[0006] Based on the above-mentioned electric braking device, the efficiency of generating braking force on the wheels can be estimated. Attached Figure Description

[0007] Figure 1 This is a schematic diagram showing the general structure of an electric braking device.

[0008] Figure 2 It is a graph showing the relationship between command torque and pressing force.

[0009] Figure 3 It is a graph showing the relationship between command torque and pressing force.

[0010] Figure 4 It is a graph showing the relationship between the command torque and the difference between the acceleration and deceleration torques.

[0011] Figure 5 (a) is a graph showing the relationship between command torque and pressing force. Figure 5 (b) is a graph showing the relationship between the command torque and the difference between the acceleration and deceleration torques.

[0012] Figure 6 (a) is a graph showing the relationship between command torque and pressing force. Figure 6 (b) is a graph showing the relationship between the command torque and the difference between the acceleration and deceleration torques. Detailed Implementation

[0013] One embodiment of the electric braking device will be described with reference to the accompanying drawings.

[0014] <Structure of this embodiment>

[0015] like Figure 1 As shown, the electric braking device 10 includes a brake caliper 20, a gearbox 30, an electric motor 40, a reduction mechanism 50, a direct-acting conversion mechanism 60, a piston 70, a motor control device 80, and a brake control device 90. The electric braking device 10 is configured to apply braking force to the wheel 100 by pressing the friction material 120 against a rotating body 110 that rotates together with the wheel 100. An example of the electric braking device 10 is a disc brake type.

[0016] <Brake calipers and gearboxes>

[0017] The brake caliper 20 has a cylinder body 21, an axle 22, and an arm 23. The cylinder body 21 is connected to the arm 23 via the axle 22. The cylinder body 21 has a cylinder 24 containing a cylindrical space. The axis of the cylinder 24 extends in the same direction as the axis of rotation of the wheel 100. The arm 23 is located in the direction that extends the axis of the cylinder 24. In the following description, the axis of the cylinder 24 will be referred to as the longitudinal direction. With the cylinder body 21 mounted in the vehicle, the rotating body 110 is disposed between the cylinder body 21 and the arm 23. Two friction materials 120 are respectively mounted on the cylinder body 21 and the arm 23. That is, the two friction materials 120 are located on both sides in the thickness direction of the rotating body 110.

[0018] The gearbox 30 houses the reduction mechanism 50 and is mounted on the cylinder body 21. In the longitudinal direction, the gearbox 30 is located at the end of the cylinder 24 opposite to the end where the friction material 120 is located. In the following description, the direction toward the friction material 120 in the longitudinal direction will be referred to as the forward direction X1, and the direction toward the gearbox 30 will be referred to as the reverse direction X2.

[0019] <Electric Motor>

[0020] An electric motor 40 is mounted on the cylinder block 21. At this time, the axis of the output shaft 41 of the electric motor 40 is parallel to the axis of the cylinder 24. Furthermore, the output shaft 41 of the electric motor 40 extends towards the interior of the gearbox 30. A rotation angle sensor 42 is provided in the electric motor 40, which outputs a signal corresponding to the rotation angle of the electric motor 40. The rotation angle sensor 42 can be, for example, a magnetic sensor.

[0021] <Speed ​​Reduction Mechanism>

[0022] The reduction mechanism 50 reduces the rotation of the output shaft 41 of the electric motor 40 and transmits it to the direct-drive conversion mechanism 60. The reduction mechanism 50 has a first gear 51 fixed to the output shaft 41 of the electric motor 40, a second gear 52 that rotates by the torque transmitted from the first gear 51, and a third gear 53 that rotates by the torque transmitted from the second gear 52. Therefore, the torque To output by the electric motor 40 is transmitted to the direct-drive conversion mechanism 60 via the first gear 51, the second gear 52, and the third gear 53.

[0023] <Direct-to-Direction Conversion Mechanism>

[0024] The direct-acting conversion mechanism 60 converts the rotary motion of the third gear 53 into the linear motion of the piston 70. The direct-acting conversion mechanism 60 has a lead screw 61 that rotates based on power transmitted from the reduction mechanism 50, and a nut 62 that moves linearly based on power transmitted from the lead screw 61. The direct-acting conversion mechanism 60 is a so-called feed screw mechanism. In other embodiments, the direct-acting conversion mechanism 60 may also be a so-called ball screw mechanism.

[0025] like Figure 1 As shown, a threaded groove is provided on the outer circumferential surface of the lead screw shaft 61. A threaded groove corresponding to the lead screw shaft 61 is provided on the inner circumferential surface of the nut 62. In the direct-drive conversion mechanism 60, the lead screw shaft 61 and the nut 62 are housed in the cylinder 24. At this time, the axial direction of the lead screw shaft 61 and the axial direction of the nut 62 are aligned with the axial direction of the cylinder 24. The base end of the lead screw shaft 61 is connected to the third gear 53. Thus, the lead screw shaft 61 can rotate integrally with the third gear 53. That is, the lead screw shaft 61 corresponds to the "rotating part of the direct-drive conversion mechanism", and the nut 62 corresponds to the "direct-drive part of the direct-drive conversion mechanism".

[0026] <Motor Control Device>

[0027] The motor control device 80 controls the electric motor 40 based on the torque command value, i.e., the command torque T, sent from the braking control device 90, and the detection signal from the rotation angle sensor 42. Specifically, the motor control device 80 controls the electric motor 40 so that the torque To output by the electric motor 40 becomes the command torque T. The motor control device 80 can be a motor driver, such as one that includes a drive circuit for the electric motor 40.

[0028] Piston

[0029] like Figure 1As shown, the piston 70 is housed in the cylinder 24 in a manner that prevents it from rotating relative to the cylinder 24 about an axis extending in the front-rear direction, but allows it to move relative to the cylinder 24 in the front-rear direction. The piston 70 is positioned opposite the friction material 120 in the front-rear direction. Furthermore, the piston 70 is integral with the nut 62. Therefore, when the nut 62 moves in the forward direction X1, the piston 70 moves in the forward direction X1 together with the nut 62. On the other hand, when the nut 62 moves in the backward direction X2, the piston 70 moves in the backward direction X2 together with the nut 62.

[0030] <Operation of the electric braking device>

[0031] In the electric braking device 10, if the electric motor 40 is driven, the rotational motion of the output shaft 41 of the electric motor 40 is reduced by the reduction mechanism 50. Then, the rotational motion of the third gear 53 of the reduction mechanism 50 is transmitted to the lead screw 61 of the direct-acting conversion mechanism 60. In the direct-acting conversion mechanism 60, the rotational motion of the lead screw 61 is converted into linear motion of the nut 62 in the forward direction X1. As a result, the piston 70 moves together with the nut 62 in the forward direction X1. Thus, the piston 70 presses the friction material 120 against the rotating body 110, thereby generating braking force on the wheel 100.

[0032] The magnitude of the braking force generated by the wheel 100 is proportional to the force exerted by the friction material 120 on the rotating body 110 (hereinafter also referred to as "pressing force P"). Furthermore, the pressing force P of the friction material 120 is proportional to the magnitude of the torque To output by the electric motor 40. Therefore, when adjusting the braking force generated by the wheel 100, the command torque T on the electric motor 40 is adjusted. Specifically, when increasing the braking force generated by the wheel 100, the command torque T on the electric motor 40 is increased; when decreasing the braking force generated by the wheel 100, the command torque T on the electric motor 40 is decreased.

[0033] <Characteristics of Electric Braking Systems>

[0034] The torque To output by the electric motor 40 is converted into the pressing force P of the friction material 120 via the reduction mechanism 50, the direct-drive conversion mechanism 60, and the piston 70. Therefore, mechanical losses occur in the power transmission path from the electric motor 40 to the friction material 120. In the following description, the torque in the torque To output by the electric motor 40 that is lost due to mechanical losses and not converted into the pressing force P of the friction material 120 is referred to as the loss torque TL. The loss torque TL includes a proportional loss torque TLp that increases proportionally to the magnitude of the torque To output by the electric motor 40, and a constant loss torque TLc that is constant regardless of the magnitude of the torque To output by the electric motor 40.

[0035] Figure 2The relationship between the command torque T and the pressing force P of the electric braking device 10 is shown in both the case of no mechanical loss and the case of mechanical loss. In both cases, the larger the command torque T, the larger the pressing force P. In other words, the smaller the command torque T, the smaller the pressing force P.

[0036] Assume there is no mechanical loss in the electric braking device 10. Figure 2 The relationship between the command torque T and the braking force P in an ideal electric braking device 10 with no mechanical losses is shown by solid lines. That is, Figure 2 The solid line shown is the ideal characteristic line Li, which represents the relationship between the command torque T (Ti) and the pressing force P in an ideal electric braking device 10 with no mechanical losses. In this case, the magnitude of the pressing force P is uniquely determined by the magnitude of the command torque T. That is, when the command torque T increases, the pressing force P increases along the ideal characteristic line Li, and when the command torque T decreases, the pressing force P decreases along the ideal characteristic line Li.

[0037] However, in reality, the electric braking device 10 experiences mechanical wear. Figure 2 The relationship between the command torque T and the pressing force P in the electric braking device 10 under this condition is shown by single-dotted and double-dotted lines. In the case of an electric braking device 10 with mechanical losses, the pressing force P changes differently with respect to the command torque T compared to the case of an electric braking device 10 without mechanical losses.

[0038] As the commanded torque T increases, the direction of the resistance corresponding to mechanical loss can be said to be the opposite direction of the movement of the friction material 120, i.e., the backward direction X2. Therefore, as Figure 2 As shown by the dashed line, with the increase of the command torque T, the required command torque T to obtain the target pressing force P increases in the presence of mechanical losses. Specifically, the command torque Ta is greater than the command torque Ti. As a result, with the increase of the command torque T, the slope of the change in pressing force P relative to the change of command torque T becomes gentler in the presence of mechanical losses. Therefore, the slope of the line shown by the dashed line is gentler than the slope of the line shown by the solid line.

[0039] When the commanded torque T decreases, the direction of the resistance corresponding to mechanical loss can be said to be the opposite direction of the movement of the friction material 120, i.e., the forward direction X1. Therefore, as Figure 2As shown by the double-dotted line, when the command torque T decreases, the required command torque T to output the target pressing force P decreases in the presence of mechanical losses. Specifically, the command torque Tr is less than the command torque Ti. As a result, when the command torque T decreases, the slope of the change in pressing force P relative to the change in command torque T becomes steeper in the presence of mechanical losses. Therefore, the slope of the line shown by the double-dotted line is steeper than the slope of the line shown by the solid line.

[0040] In the following explanation, the straight line representing the relationship between the command torque T and the pressing force P when the command torque T increases will be called the first pressurization line L1a, and the straight line representing the relationship between the command torque T and the pressing force P when the command torque T decreases will be called the first depressurization line L1r. As mentioned above, the slope of the first pressurization line L1a is gentler than the slope of the straight line shown in the solid line, and the slope of the first depressurization line L1r is steeper than the slope of the straight line shown in the solid line.

[0041] Furthermore, as mechanical losses increase due to the aging of the electric braking device 10, the slope of the first pressurization line L1a becomes gentler, while the slope of the first depressurization line L1r becomes steeper. Thus, given the mechanical losses in the electric braking device 10, the command torque T cannot be applied to the wheels 100 without adjusting the slope of the first pressurization line L1a or the slope of the first depressurization line L1r.

[0042] <Brake Control Device>

[0043] like Figure 1 As shown, the brake control device 90 includes a CPU 91 and a memory 92. By executing the program stored in the memory 92 by the CPU 91, the brake control device 90 outputs command values ​​to the motor control device 80, thereby driving the electric motor 40.

[0044] By executing the program in memory 92 by CPU 91, the brake control device 90 functions as multiple functional units for generating instruction values ​​for motor control device 80. These multiple functional units include a brake control unit 93, a torque difference calculation unit 94, an efficiency estimation unit 95, a constant loss calculation unit 96, and a correction unit 97.

[0045] <Brake Control Unit>

[0046] The braking control unit 93 acquires the required braking force for the vehicle. For example, when the driver is operating the vehicle, the braking control unit 93 calculates the required braking force based on the amount of operation of the brake pedal, etc. Furthermore, when the vehicle is in automatic driving mode, the braking control unit 93 acquires the required braking force sent from the automatic driving control device that performs automatic driving control of the vehicle. Next, the braking control unit 93 calculates the command torque T corresponding to the required braking force. The required braking force is related to the pressing pressure P, and the pressing pressure P is related to the command torque T. Therefore, when the required braking force is large, the calculated command torque T is also large, and when the required braking force is small, the calculated command torque T is also small. The braking control unit 93 can calculate the command torque T either by referring to a formula that establishes a relationship between the required braking force and the command torque T, or by referring to a mapping table that establishes a relationship between the required braking force and the command torque T. Then, the braking control unit 93 sends the command torque T to the motor control device 80.

[0047] <Torque Difference Calculation Section>

[0048] When the command torque T increases, in other words, when the required braking force increases, the torque difference calculation unit 94 acquires the command torque T during the period when the trend of change of the command torque T changes from an increasing trend to a decreasing trend. That is, the torque difference calculation unit 94 acquires the command torque T for the first period, i.e., the first command torque T1. Next, the torque difference calculation unit 94 acquires the command torque T during the period when the pressure P begins to decrease due to maintaining the trend of change of the command torque T. That is, the torque difference calculation unit 94 acquires the command torque T for the second period, i.e., the second command torque T2. Then, the torque difference calculation unit 94 calculates the difference between the first command torque T1 and the second command torque T2, i.e., the pressure difference ΔT.

[0049] like Figure 3 As shown by the first arrow V1 (V11, V12, V13), the change trend of the command torque T changes from an increasing trend to a decreasing trend.

[0050] As indicated by the first arrow V11, when the command torque T increases, the pressing pressure P increases along the first pressing line L1a. Then, as indicated by the first arrow V12, if the trend of the command torque T changes from an increasing trend to a decreasing trend, the command torque T begins to decrease. Here, the period during which the trend of the command torque T changes from an increasing trend to a decreasing trend is the first period. That is, the command torque T during the period when the trend of the command torque T changes from an increasing trend to a decreasing trend is the first command torque T1 (T1a). As indicated by the first arrow V12, for a period of time after the command torque T begins to decrease, the pressing pressure P remains approximately constant. That is, even if the command torque T decreases, the pressing pressure P does not decrease. Then, as indicated by the first arrow V13, if the decrease in command torque T continues, the pressing pressure P begins to decrease along the first depressurization line L1r. Here, the period from the first period during which the pressing pressure P begins to decrease due to maintaining the trend of the command torque T is the second period. That is, starting from the first period, the command torque T during the period when the pressure P begins to decrease due to the trend of maintaining the change of the command torque T is the second command torque T2 (T2r). Therefore, the difference between the first command torque T1 (T1a) and the second command torque T2 (T2r) is the pressure difference ΔT (ΔT1).

[0051] Similarly, when the command torque T decreases, in other words, when a reduction in braking force is required, the torque difference calculation unit 94 acquires the command torque T during the period when the trend of change of the command torque T changes from a decreasing trend to an increasing trend. That is, the torque difference calculation unit 94 acquires the command torque of the first period, i.e., the first command torque T1. Next, while maintaining the trend of change of the command torque T, the torque difference calculation unit 94 acquires the command torque T during the period when the pressing force P begins to increase. That is, the torque difference calculation unit 94 acquires the command torque T of the second period, i.e., the second command torque T2. Then, the torque difference calculation unit 94 calculates the difference between the first command torque T1 and the second command torque T2, i.e., the pressure relief torque difference ΔT.

[0052] like Figure 3 As shown by the second arrow V2 (V21, V22, V23), the change trend of the command torque T changes from a decreasing trend to an increasing trend.

[0053] As shown by the second arrow V21, when the command torque T decreases, the pressing pressure P decreases along the first decompression line L1r. Then, as shown by the second arrow V22, if the trend of the command torque T changes from a decreasing trend to an increasing trend, the command torque T begins to increase. Here, the period during which the trend of the command torque T changes from a decreasing trend to an increasing trend is the first period. That is, the command torque T during the period when the trend of the command torque T changes from a decreasing trend to an increasing trend is the first command torque T1 (T1r). As shown by the second arrow V22, for a period of time after the command torque T begins to increase, the pressing pressure P remains approximately constant. That is, even if the command torque T increases, the pressing pressure P does not increase. Then, as shown by the second arrow V23, if the increase of the command torque T continues, the pressing pressure P begins to increase along the first pressurization line L1a. Here, the period from the first period during which the pressing pressure P begins to increase due to maintaining the trend of the command torque T is the second period. That is, starting from the first period, the command torque T during the period when the pressure P begins to increase due to the trend of the command torque T's change is the second command torque T2 (T2a). Therefore, the difference between the first command torque T1 (T1r) and the second command torque T2 (T2a) is the pressure difference ΔT (ΔT2).

[0054] like Figure 3 As shown, in the first command torques T1a and T1r, the first command torque T1a is the command torque T corresponding to the first pressurization line L1a, and the first command torque T1r is the command torque T corresponding to the first depressurization line L1r. Similarly, in the second command torques T2a and T2r, the second command torque T2a is the command torque T corresponding to the first pressurization line L1a, and the second command torque T2r is the command torque T corresponding to the first depressurization line L1r. Therefore, the first command torque T1a during the first period when the trend of change of the command torque T changes from an increasing trend to a decreasing trend is called the pressurization-side first command torque T1a. The second command torque T2r during the second period, which changes according to the pressure P while maintaining the decreasing trend of the command torque T, is called the depressurization-side second command torque T2r. Furthermore, the first command torque T1r during the first period when the trend of change of the command torque T changes from a decreasing trend to an increasing trend is called the depressurization-side first command torque T1r. The second command torque T2a, which begins to change according to the pressure P in the second period starting from the first period due to the increasing trend of the command torque T, is called the second command torque T2a on the pressurized side.

[0055] Furthermore, each time the torque difference calculation unit 94 calculates the increase / decrease torque difference ΔT, it establishes a correspondence between the first command torque T1 and the second command torque T2 used for calculating the increase / decrease torque difference ΔT and the increase / decrease torque difference ΔT, and stores them in the memory 92. For example, in Figure 3In the example shown, the first command torque T1a on the pressurization side and the second command torque T2r on the depressurization side are stored in memory 92 in a state where a correspondence is established with the pressurization-depressurization torque difference ΔT1. Additionally, the first command torque T1r on the depressurization side and the second command torque T2a on the pressurization side are stored in memory 92 in a state where a correspondence is established with the pressurization-depressurization torque difference ΔT2.

[0056] When the pressing force P changes, the friction material 120 moves in the forward direction X1 or the backward direction X2. That is, when the pressing force P changes, the rotation angle of the electric motor 40 changes. Therefore, while maintaining the changing trend of the command torque T, the torque difference calculation unit 94 determines that the pressing force P has changed when the rotation angle of the electric motor 40 changes. Therefore, while maintaining the changing trend of the command torque T, the torque difference calculation unit 94 determines the second period based on the change in the rotation angle of the electric motor 40. As described above, in the second period, the rotation angle of the electric motor 40 changes, and therefore, a back electromotive force is generated in the second period. Therefore, the electric braking device 10 can also determine the second period based on the back electromotive force while maintaining the changing trend of the command torque T.

[0057] <Efficiency Estimation Department>

[0058] The efficiency estimation unit 95 estimates the efficiency Ea and Er of the electric braking device 10 based on the relationship between the first command torque T1 or the second command torque T2 and the difference between the pressure relief torque ΔT.

[0059] Figure 4 This is a graph showing the relationship between the first command torque T1 and the second command torque T2 obtained by the torque difference calculation unit 94 and the increase / decrease torque difference ΔT. Figure 4 In this context, the straight line representing the relationship between the first command torque T1a and the second command torque T2a on the pressurization side and the torque difference ΔT between the pressurization and depressurization sides is called the second pressurization straight line L2a. Similarly, the straight line representing the relationship between the first command torque T1r and the second command torque T2r on the depressurization side and the torque difference ΔT between the pressurization and depressurization sides is called the second depressurization straight line L2r.

[0060] The second pressurization line L2a is a straight line obtained by approximating the relationship between multiple plotted data representing the relationship between the first command torque T1a on the pressurization side and the difference between the pressurization and depressurization torques ΔT1, and the relationship between the second command torque T2a on the pressurization side and the difference between the pressurization and depressurization torques ΔT2. Similarly, the second pressurization line L2a can also be obtained solely from the multiple plotted data representing the relationship between the first command torque T1a on the pressurization side and the difference between the pressurization and depressurization torques ΔT1.

[0061] The second decompression line L2r is a straight line obtained by approximating multiple plotted data representing the relationship between the first command torque T1r on the decompression side and the difference between the applied and decompression torques ΔT2, and multiple plotted data representing the relationship between the second command torque T2r on the decompression side and the difference between the applied and decompression torques ΔT1. The second decompression line L2r can also be obtained solely from the multiple plotted data representing the relationship between the first command torque T1r on the decompression side and the difference between the applied and decompression torques ΔT2. Similarly, the second decompression line L2r can also be obtained solely from the multiple plotted data representing the relationship between the second command torque T2r on the decompression side and the difference between the applied and decompression torques ΔT1.

[0062] In the following explanation, the slope of the second pressurization line L2a will be set as the pressurization slope α, and the slope of the second depressurization line L2r will be set as the depressurization slope β. When approximating the second pressurization line L2a and the second depressurization line L2r, for example, the least squares method can be used.

[0063] In addition, Figure 4 To simplify the illustrations, only one plotted data point is shown, representing the relationship between the first command torque T1a on the pressurized side and the torque difference ΔT1 between the pressurization and depressurization sides, and another plotted data point is shown, representing the relationship between the second command torque T2a on the pressurized side and the torque difference ΔT2 between the pressurization and depressurization sides. Similarly, only one plotted data point is shown, representing the relationship between the first command torque T1r on the depressurization side and the torque difference ΔT2 between the pressurization and depressurization sides, and another plotted data point is shown, representing the relationship between the second command torque T2r on the depressurization side and the torque difference ΔT1 between the pressurization and depressurization sides. Furthermore, the actual acquired plotted data points contain errors, so the possibility of multiple plotted data points being perfectly aligned on a straight line is extremely low.

[0064] like Figure 5 As shown in (a), in the electric braking device 10 without mechanical losses, the command torque T required to obtain the specified pressing force P is defined as "Ti". On the other hand, in the electric braking device 10 with mechanical losses, the command torque T required to obtain the specified pressing force P when the command torque T increases is defined as "Ta", and the command torque T required to obtain the specified pressing force P when the command torque T decreases is defined as "Tr". Furthermore, the efficiency of the electric braking device 10 when the command torque T increases, i.e., the pressurization efficiency, is defined as "Ea", and the efficiency of the electric braking device 10 when the command torque T decreases, i.e., the depressurization efficiency, is defined as "Er". In this case, the pressurization efficiency Ea and the depressurization efficiency Er are defined as follows.

[0065] [Mathematical Expression 1]

[0066]

[0067] When the command torque T increases, it needs to be increased by the amount corresponding to the resistance caused by mechanical losses. Therefore, the command torque Ta is greater than the command torque Ti. Consequently, the pressurization efficiency Ea is less than 1. Furthermore, the smaller the deviation between the command torque Ta and the command torque Ti (i.e., the smaller the command torque Ta), the higher the pressurization efficiency Ea. Conversely, when the command torque T decreases, it needs to be decreased by the amount corresponding to the resistance caused by mechanical losses. Therefore, the command torque Tr is less than the command torque Ti. Consequently, the decompression efficiency Er is less than 1. Furthermore, the smaller the deviation between the command torque Tr and the command torque Ti (i.e., the larger the command torque Tr), the higher the decompression efficiency Er.

[0068] like Figure 5 As shown in (a), when the command torque T increases, the proportional loss torque TLp, which is proportional to the command torque T, is the difference between the command torque Ti and the command torque Ta. Therefore, the pressurization efficiency Ea in (Equation 1) is the ratio of the difference between the command torque T (=Ta) and the proportional loss torque TLp (=Ta−Ti) (=Ti) to the command torque T (=Ta). Furthermore, when the command torque T decreases, the proportional loss torque TLp, which is proportional to the command torque T, is the difference between the command torque Ti and the command torque Tr. Therefore, the depressurization efficiency Er in (Equation 2) is the ratio of the difference between the command torque T (=Tr) and the proportional loss torque TLp (=Ti−Tr) (=Ti) to the command torque T (=Tr).

[0069] Therefore, the proportional loss torque TLp can be described as the difference between the command torque T in the ideal electric brake device 10 without mechanical loss and the command torque T in the electric brake device 10 with mechanical loss when a specified pressing force P is applied to the rotating body 110.

[0070] If we connect the values ​​of the left-hand sides of (Equation 1) and (Equation 2) with the values ​​of the right-hand sides by multiplying them together using an equal sign, we can obtain the following equation.

[0071] [Mathematical Expression 2]

[0072]

[0073] like Figure 5 As shown in (b), the pressure slope α of the second pressurization line L2a is ΔT / Ta, the pressure reduction slope β of the second depressurization line L2r is ΔT / Tr, and the torque difference between pressurization and depressurization is ΔT = Ta−Tr. Therefore, the pressurization slope α and the depressurization slope β can be expressed by the following formulas.

[0074] [Mathematical Expression 3]

[0075]

[0076] Here, the pressurization efficiency Ea of the new electric brake device 10 is set as "Ean", the depressurization efficiency Er of the new electric brake device 10 is set as "Ern", and the variation coefficient representing the degree of aging of the new electric brake device 10 is set as "K". The variation coefficient K of the new electric brake device 10 is "1", and the variation coefficient K of the electric brake device 10 gradually decreases over time. The pressurization efficiency Ean and the depressurization efficiency Er can be set based on the measured value of the pressure P during the manufacturing of the electric brake device 10. The current pressurization efficiency Ea and depressurization efficiency Er of the electric brake device 10 can be expressed by the following formula.

[0077] [Mathematical Expression 4]

[0078]

[0079] If we connect the values ​​of the left sides of (Equation 6) and (Equation 7) multiplied together with the values ​​of the right sides multiplied together using an equal sign, we can obtain the following equation.

[0080] [Mathematical Expression 5]

[0081]

[0082] If we move the variation coefficient K in (Equation 8) to the left, we can obtain the following equation.

[0083] [Mathematical Expression 6]

[0084]

[0085] If we substitute the transformed (Equation 4) or (Equation 5) into the molecule on the right side of (Equation 9), we can obtain the following equation.

[0086] [Mathematical Expression 7]

[0087]

[0088] As shown in Equation 10, the variation coefficient K is obtained by using the pressurization efficiency Ean, the depressurization efficiency Ern, and the pressurization slope α of the new electric braking device 10. Furthermore, as shown in Equation 11, the variation coefficient K is obtained by using the pressurization efficiency Ean, the depressurization efficiency Ern, and the depressurization slope β of the new electric braking device 10.

[0089] If Equation 10 or Equation 11 is substituted into Equation 6, then based on the pressure slope α of the second pressure line L2a, and the pressure efficiency Ean and pressure reduction efficiency Ern of the new electric braking device 10, the formula for calculating the pressure efficiency Ea of the electric braking device 10 can be obtained. If Equation 10 or Equation 11 is substituted into Equation 7, then based on the pressure reduction slope β of the second pressure reduction line L2r, and the pressure efficiency Ean and pressure reduction efficiency Ern of the new electric braking device 10, the formula for calculating the pressure reduction efficiency Er of the electric braking device 10 can be obtained.

[0090] Therefore, the efficiency estimation unit 95 estimates the variation coefficient K of the electric braking device 10 based on the pressure slope α of the second pressure line L2a, and the pressure efficiency Ean and decompression efficiency Ern of the new electric braking device 10. Here, the efficiency estimation unit 95 calculates the pressure slope α based on the relationship between at least one of the first command torque T1a and the second command torque T2a on the pressure side and the pressure-decompression torque difference ΔT. Specifically, the efficiency estimation unit 95 calculates the pressure slope α based on at least one of the relationships between the first command torque T1a and the pressure-decompression torque difference ΔT1 when the trend of the command torque T changes from an increasing trend to a decreasing trend, and the relationships between the second command torque T2a and the pressure-decompression torque difference ΔT2 when the trend of the command torque T changes from a decreasing trend to an increasing trend.

[0091] On the other hand, the efficiency estimation unit 95 can also calculate the variation coefficient K of the electric braking device 10 based on the decompression slope β of the second decompression line L2r, and the pressurization efficiency Ean and decompression efficiency Ern of the new electric braking device 10. Here, the efficiency estimation unit 95 calculates the decompression slope β based on the relationship between at least one of the first command torque T1r on the decompression side and the second command torque T2r on the decompression side and the difference between the pressurization and decompression torques ΔT. Specifically, the efficiency estimation unit 95 calculates the decompression slope β based on at least one of the relationship between the first command torque T1r and the difference between the pressurization and decompression torques ΔT2 when the trend of the command torque T changes from a decreasing trend to an increasing trend, and the relationship between the second command torque T2r and the difference between the pressurization and decompression torques ΔT1 when the trend of the command torque T changes from an increasing trend to a decreasing trend.

[0092] Thus, the efficiency estimation unit 95 estimates at least one of the pressure-increasing efficiency Ea and the depressurizing efficiency Er of the electric braking device 10 based on the estimated variation coefficient K and at least one of the pressure-increasing efficiency Ean and depressurizing efficiency Ern of the new electric braking device 10.

[0093] <Constant Loss Calculation Department>

[0094] The constant loss calculation unit 96 calculates the constant loss torque TLc based on the first command torque T1 or the second command torque T2 and the difference between the pressure relief torque ΔT.

[0095] As described above, the loss torque TL includes a constant loss torque TLc that is disproportionate to the magnitude of the torque To output by the electric motor 40. Therefore, as Figure 6 As shown by the dashed line in (a), when the command torque T is increased from "0", the friction material 120 does not move in the forward direction X1 if the command torque T is less than the constant loss torque TLc. That is, when the command torque T is less than the constant loss torque TLc, the pressing pressure P is "0". If the command torque T becomes greater than or equal to the constant loss torque TLc, the friction material 120 moves in the forward direction X1. That is, if the command torque T becomes greater than or equal to the constant loss torque TLc, the pressing pressure P increases according to the increase of the command torque T.

[0096] On the other hand, such as Figure 6 As shown by the double-dotted line in (a), when the command torque T is reduced towards "0", the friction material 120 will not return to its initial position even if the command torque T becomes "0". That is, even if the command torque T becomes "0", the pressing force P will not become "0". In this case, if the command torque T is reduced to a value that is the same as the constant loss torque TLc but different in sign, the pressing force P becomes "0". In this embodiment, it is assumed that the constant loss torque TLc acts equally when the command torque T increases and decreases. That is, Figure 6 The command torque T (=TLca) of (a), which corresponds to the horizontal intercept of the first pressurization line L1a, is equal in magnitude and sign to the constant loss torque TLc. On the other hand, Figure 6 The command torque T (=TLcr) of (a) which is equivalent to the horizontal intercept of the first decompression line L1r is equal in magnitude to the constant loss torque TLc but has different signs.

[0097] Figure 6 (b) shows the second pressurization line L2a and the second depressurization line L2r. When deriving a first-order approximation of the second pressurization line L2a, the slope, x-axis intercept, and y-axis intercept of L2a can be obtained in one step. Similarly, when deriving a first-order approximation of the second depressurization line L2r, the slope, x-axis intercept, and y-axis intercept of L2r can be obtained in one step.

[0098] If the command torque T, which corresponds to the horizontal intercept of the second pressurization line L2a and the second depressurization line L2r, is set as TLc0, then the constant loss torque TLc can be expressed by the following formula. Furthermore, (Equation 12) is the y-coordinate relationship at point Qa, and (Equation 13) is the y-coordinate relationship at point Qr. Additionally, as... Figure 6 As shown in (b), the torque TLc0 is the command torque T when the torque difference ΔT between the applied and reduced pressure becomes “0”.

[0099] [Mathematical Expression 8]

[0100]

[0101] Since TLca = TLc, if we replace TLca with TLc in (Equation 12) and then transform the form of the expression, we can obtain (Equation 14). Similarly, since TLcr = −TLc, if we replace TLcr with −TLc in (Equation 13) and then transform the form of the expression, we can obtain (Equation 15).

[0102] [Mathematical Expression 9]

[0103]

[0104] Therefore, the efficiency estimation unit 95 calculates the constant loss torque TLc based on the pressure slope α of the second pressure-applying line L2a and the horizontal intercept of the second pressure-applying line L2a, i.e., the torque TLc0. That is, the efficiency estimation unit 95 calculates the constant loss torque TLc based on the relationship between at least one of the pressure-applying side first command torque T1a and the pressure-applying side second command torque T2a and the pressure-applying torque difference ΔT, and the torque TLc0. On the other hand, the efficiency estimation unit 95 calculates the constant loss torque TLc based on the pressure-applying slope β of the second pressure-applying line L2r and the horizontal intercept of the second pressure-applying line L2r, i.e., the torque TLc0. That is, the efficiency estimation unit 95 calculates the constant loss torque TLc based on the relationship between at least one of the pressure-applying side first command torque T1r and the pressure-applying side second command torque T2r and the pressure-applying torque difference ΔT, and the torque TLc0.

[0105] Furthermore, the efficiency estimation unit 95 can also calculate the constant loss torque TLc based on the pressure slope α of the second pressure line L2a and the y-intercept of the second pressure line L2a. Similarly, the efficiency estimation unit 95 can also calculate the constant loss torque TLc based on the decompression slope β of the second decompression line L2r and the y-intercept of the second decompression line L2r.

[0106] <Revision Section>

[0107] The correction unit 97 corrects the pressing pressure correlation value related to the pressing pressure P based on the efficiency Ea, Er, and constant loss torque TLc of the electric braking device 10. For example, the correction unit 97 corrects the command torque T, which is an example of the pressing pressure correlation value. Here, the command torque T calculated by the braking control unit 93 is called the command torque before correction, and the command torque T after correction by the correction unit 97 is called the command torque after correction.

[0108] When the command torque T is trending upwards, the correction unit 97 corrects the original command torque according to the principle that a lower pressurization efficiency Ea of the electric brake device 10 results in a larger corrected command torque. Additionally, the correction unit 97 corrects the original command torque according to the principle that a larger constant loss torque TLc results in a larger corrected command torque. Conversely, when the command torque T is trending downwards, the correction unit 97 corrects the original command torque according to the principle that a lower depressurization efficiency Er of the electric brake device 10 results in a smaller corrected command torque. Additionally, the correction unit 97 corrects the original command torque according to the principle that a larger constant loss torque TLc results in a smaller corrected command torque. Furthermore, the correction unit 97 can correct the command torque T using either a predetermined mapping table or a predetermined correction formula.

[0109] <Function and Effects of This Implementation Method>

[0110] When braking is required for the vehicle, the electric braking device 10 is controlled based on the required braking force. Specifically, the electric motor 40 of the electric braking device 10 is controlled based on the command torque T corresponding to the required braking force. In this way, the torque To output from the electric motor 40 is converted into the pressing force P of the friction material 120. As a result, the friction material 120 presses against the rotating body 110, thereby generating a braking force on the wheel 100.

[0111] Because the electric braking device 10 has mechanical losses, when the torque To output by the electric motor 40 is converted into the pressing force P of the friction material 120, not all of the torque To output by the electric motor 40 is converted into the pressing force P of the friction material 120. Specifically, the electric motor 40 includes a proportional loss torque TLp and a constant loss torque TLc as a loss torque TL. In this embodiment, the electric braking device 10 corrects the command torque T calculated based on the required braking force based on the efficiency Ea, Er and the constant loss torque TLc of the electric braking device 10. Therefore, the electric braking device 10 can suppress the braking force generated by the wheel 100 from being excessive or insufficient relative to the required braking force. Furthermore, compared to the case where the command torque T is corrected based only on one of the efficiency Ea, Er and the constant loss torque TLc of the electric braking device 10, the electric braking device 10 can reduce the deviation between the braking force generated by the wheel 100 and the required braking force.

[0112] The electric braking device 10 estimates its current efficiency Ea and Er based on the difference between the first command torque T1 or the second command torque T2 and the pressure difference ΔT. In other words, even without a sensor to detect the pressing pressure P of the friction material 120, the electric braking device 10 can estimate its current efficiency Ea and Er. Therefore, an electric braking device 10 capable of estimating efficiency Ea and Er can be constructed at low cost.

[0113] The electric braking device 10 can achieve the following effects.

[0114] (1) The second command torque T2 is the command torque T of the second period, which begins to change due to the changing trend of the command torque T since the first period. The electric braking device 10 determines the second period based on the change in the rotation angle of the electric motor 40. When the pressing force P is constant, the rotation angle of the electric motor 40 is constant; when the pressing force P changes, the rotation angle of the electric motor 40 changes. Therefore, the electric braking device 10 can determine the second period with high accuracy after maintaining the changing trend of the command torque T since the first period.

[0115] <Example of Change>

[0116] This embodiment can be modified as follows. This embodiment and the following modifications can be combined and implemented within the scope of technical non-contradiction.

[0117] The braking control device 90 can also acquire a first command torque T1 and a second command torque T2 by increasing or decreasing the command torque T when the vehicle is stationary. In this case, the braking control device 90 can acquire the first command torque T1, the second command torque T2, and the torque difference ΔT between the acceleration and deceleration forces with minimal external interference.

[0118] • If the characteristics of the electric braking device 10 change excessively over time, the pressure efficiency Ea or pressure reduction efficiency Er may decrease excessively. Therefore, the brake control device 90 may also issue a report to the vehicle user urging them to repair or replace the electric braking device 10 if the pressure efficiency Ea or pressure reduction efficiency Er decreases below a predetermined efficiency judgment value. Here, the efficiency judgment value compared with the pressure efficiency Ea and the efficiency judgment value compared with the pressure reduction efficiency Er may be different values.

[0119] • When the command torque T is small, the proportion of constant loss torque TLc in the loss torque TL is more likely to be higher than the proportion of proportional loss torque TLp in the loss torque TL compared to when the command torque T is large. Therefore, when the command torque T is less than the specified torque judgment value, the braking control device 90 can also correct the pressing force correlation value by considering only the constant loss torque TLc in the loss torque TL.

[0120] Similarly, when the command torque T is large, the proportion of proportional loss torque TLp in the loss torque TL is more likely to be higher than the proportion of constant loss torque TLc in the loss torque TL compared to when the command torque T is small. Therefore, when the command torque T is above a predetermined torque judgment value, the braking control device 90 can also correct the actuation force correlation value based solely on the proportional loss torque TLp in the loss torque TL. That is, when the command torque T is above a predetermined torque judgment value, the braking control device 90 can also correct the actuation force correlation value based solely on the efficiency Ea and Er of the electric braking device 10.

[0121] • The brake control device 90 can also correct the command torque T without considering the constant loss torque TLc. That is, the brake control device 90 can also have a correction unit 97, which corrects the values ​​related to the pressing pressure, i.e., the pressing pressure associated values, based solely on the efficiency Ea and Er of the electric brake device 10.

[0122] • As shown in Equations 10 and 11, the variation coefficient K can be calculated using the pressure slope α or the decompression slope β. As shown in Equations 14 and 15, the constant loss torque TLc can be calculated using the pressure slope α or the decompression slope β. Therefore, the braking control device 90 can correct the braking force correlation value as long as it can obtain the pressure slope α or the decompression slope β. Here, as... Figure 4 As shown, the command torques T(T1a, T2a) on the pressurization side corresponding to the same magnitude of the pressurization-depressurization torque difference ΔT are greater than the command torques T(T1r, T2r) on the depressurization side. The larger the value of the command torque T, the greater the ratio of the magnitude of the command torque T to the external disturbance. Therefore, the braking control device 90 can more easily and accurately correct the pressing pressure correlation value by using the pressurization slope α.

[0123] • If the pressing force P applied to the rotating body 110 changes, the vehicle's acceleration changes. Therefore, when the vehicle is in motion, the electric braking device 10 can also determine, based on the vehicle's acceleration, the second period in which the pressing force P applied to the rotating body 110 begins to change due to the trend of maintaining the command torque T, which started from the first period.

[0124] • The pressure correlation value can be any value related to the pressure P that is different from the command torque T. For example, the pressure correlation value can be an estimated value of the pressure P. In this case, the brake control device 90 can also estimate the current pressure P of the electric brake device 10 based on the estimated value of the pressure P of the new electric brake device 10 and the efficiency Ea and Er of the electric brake device 10.

[0125] • The direct-acting conversion mechanism can be replaced by a mechanism in which the nut 62 functions as a "rotating part" and the lead screw 61 functions as a "direct-acting part".

[0126] • The electric braking device 10 may also include an axial force sensor capable of detecting the pressing force P. Furthermore, the braking control device 90 may calculate the efficiency Ea and Er of the electric braking device 10 based on the command torque T and the detection results of the axial force sensor. In this case, the electric braking device 10 may also determine whether the efficiency Ea and Er based on the detection results of the axial force sensor is reasonable by comparing it with the efficiency Ea and Er based on the difference between the applied and depressurized torque ΔT.

[0127] • The electric braking device 10 may also be a wet electric braking device, which supplies brake fluid to the wheel cylinder according to the forward movement of the piston 70, thereby generating braking force on the wheel 100.

[0128] • The electric brake device 10 may not be a caliper-type disc brake device as long as it has a direct-acting conversion mechanism 60 with a nut 62 and a lead screw shaft 61. For example, the electric brake device 10 may also be a drum-type electric brake device.

[0129] The braking control device 90 is not limited to a processing circuit that includes a CPU 91 and a memory 92 and performs software processing. For example, the braking control device 90 may also have a dedicated hardware circuit that performs at least a portion of the various processes performed in the above embodiments. Examples of dedicated hardware circuits include ASICs. ASIC is short for "Application Specific Integrated Circuit". That is, the braking control device 90 can be configured as described in any of the following (a) to (c).

[0130] (a) A processing circuit comprising: a processing device for performing all of the above-described processing according to a program; and a program storage device such as a memory 92 for storing the program.

[0131] (b) A processing circuit comprising: a processing device and a program storage device for performing a portion of the processing according to a program; and a dedicated hardware circuit for performing the remaining processing.

[0132] (c) A processing circuit having dedicated hardware circuitry that performs all of the above-described processing.

[0133] Here, there may be multiple software execution devices with processing devices and program storage devices, as well as dedicated hardware circuits.

Claims

1. An electric braking device, wherein the rotating part of the direct-acting conversion mechanism of the electric braking device rotates according to the rotational motion of an electric motor, and the rotational motion of the rotating part is converted into linear motion in the forward or backward direction of the direct-acting part of the direct-acting conversion mechanism, and according to the linear motion of the direct-acting part, a friction material is pressed against a rotating body that rotates together with the wheel of the vehicle, thereby applying braking force to the wheel, wherein... have: The torque difference calculation unit calculates the difference between the first command torque and the second command torque, i.e., the pressure difference. The first command torque is the command torque of the first period, which is the period during which the command value of the torque of the electric motor, i.e., the trend of the command torque, changes from one trend of increase to the other. The second command torque is the command torque of the second period, which is the period from the first period onwards when the pressing force applied to the rotating body begins to change due to maintaining the trend of the command torque. The efficiency estimation unit estimates the efficiency of the electric braking device based on the first command torque or the second command torque and the difference between the acceleration and deceleration torques. The efficiency of the electric braking device is the ratio of the difference between the command torque and the proportional loss torque to the command torque, wherein a larger command torque results in a larger proportional loss torque. The aforementioned proportional loss torque is the difference between the command torque of the electric motor output torque in the ideal electric braking device without mechanical loss and the command torque of the electric braking device with mechanical loss when the specified pressing force is applied to the rotating body.

2. The electric braking device according to claim 1, wherein, The torque difference calculation unit determines the second period based on the change in the rotation angle of the electric motor.

3. The electric braking device according to claim 1, wherein, The efficiency estimation unit estimates the efficiency of the electric braking device based on at least one of the pressurization slope and the depressurization slope. The aforementioned pressure-increasing slope is the slope of a first-order approximation calculated based on at least one of the following: the relationship between the first command torque and the pressure-in / pressure-out torque difference when the command torque changes from an increasing trend to a decreasing trend, and the relationship between the second command torque and the pressure-in / pressure-out torque difference when the command torque changes from a decreasing trend to an increasing trend. The aforementioned pressure reduction slope is the slope of a first-order approximation calculated based on at least one of the following: the relationship between the first command torque and the pressure reduction torque difference when the command torque changes from a decreasing trend to an increasing trend, and the relationship between the second command torque and the pressure reduction torque difference when the command torque changes from an increasing trend to a decreasing trend.

4. The electric braking device according to any one of claims 1 to 3, wherein, The torque output by the aforementioned electric motor that is not converted into the loss torque due to pressure and is lost regardless of the magnitude of the command torque is considered a constant loss torque. It includes a constant loss calculation unit that calculates the constant loss torque based on the first command torque or the second command torque and the difference between the applied and depressurized torques.

5. The electric braking device according to claim 4, wherein, It includes a correction unit that corrects the value related to the pressing pressure, i.e. the pressing pressure correlation value, based on at least one of the efficiency of the electric braking device and the constant loss torque.

Images