Electric parking brake system

Abstract

To provide an electric parking brake device configured to be able to sense that a parking brake is dragged, without using a load sensing device.SOLUTION: An electric parking brake device 1 according to the present invention comprises: a load sensing part 2 that senses a load on a parking brake PB; a stroke position sensing part 3 that senses a stroke position of a cable CA; a memorizing part 4 that memorizes a sensed result by the stroke position sensing part 3; and a control part 5 that controls operation of pulling the cable CA and operation of returning the cable. The control part 5 makes the memorizing part 4 memorize, as a dragging-determination reference position, a stroke position at the time when the load sensing part 2 senses a dragging-determination reference load, when the parking brake PB is actuated, and determines whether the stroke position of the cable CA at the time when it is determined that the actuation of the parking brake PB is completely released is in a predetermined range with respect to the dragging-determination reference position, when the actuation of the parking brake PB is released.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electric parking brake device.

Background Art

[0002] Conventionally, as an electric parking brake device that electrically operates and releases the parking brake of a vehicle, for example, the electric parking brake device disclosed in Patent Document 1 has been used. When the electric parking brake device of Patent Document 1 operates the parking brake, it is configured to pull the cable for operating the parking brake and stop pulling the cable when a target load is applied to the cable. Further, when the electric parking brake device of Patent Document 1 releases the parking brake, it is configured to return the cable from the stroke position of the cable when the parking brake is in the operating state to a predetermined release target position or to the original position before the parking brake is put into the operating state.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In electric parking brake systems, the cable mounting position may change due to maintenance or other reasons, causing the cable stroke position stored in the electric parking brake system to deviate from the actual stroke position. In such cases, even if the electric parking brake system, as in Patent Document 1, is operated to release the parking brake by returning the cable stroke position to a predetermined release target position or to the original position before the parking brake was activated, based on the current stroke position stored in the electric parking brake system, there is a risk of insufficient release resulting in dragging between the braking member and the braked member (insufficient separation).

[0005] In electric parking brake systems, drag is detected by detecting the load acting on the parking brake after the parking brake is released. However, in the case of vehicles that require a larger load to maintain a stationary state, such as large vehicles, it is necessary to install a load detection device that can detect a larger load. However, a load detection device configured in this way may have lower accuracy in detecting small loads, and may not be able to accurately detect drag.

[0006] The present invention aims to provide an electric parking brake system that can detect parking brake drag without using a load detection device. [Means for solving the problem]

[0007] The electric parking brake device of the present invention is an electric parking brake device that electrically operates and deactivates a parking brake by pulling and releasing a cable, the electric parking brake device comprising: a load detection unit that detects the load applied to the parking brake; a stroke position detection unit that detects the stroke position of the cable; a storage unit that stores the detection result of the stroke position detection unit; and a control unit that controls the pulling and releasing operations of the cable, wherein when the parking brake is operated, the control unit stores the stroke position at which the load detection unit detects a drag judgment criterion load as a drag judgment criterion position in the storage unit, and when the parking brake is deactivated, it determines whether the stroke position of the cable at which the deactivation of the parking brake is determined to be complete is within a predetermined range with respect to the drag judgment criterion position. [Effects of the Invention]

[0008] According to the present invention, an electric parking brake device is provided that can detect parking brake drag without using a load detection device. [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram showing a schematic configuration of an electric parking brake device according to one embodiment of the present invention. [Figure 2] This flowchart shows the action taken to engage the parking brake. [Figure 3] This diagram shows the operation to release the parking brake and the operation to determine if the brake is still dragging after the release is complete. [Figure 4] This is an explanatory diagram illustrating the change in the cable's stroke position during operation, assuming that the cable's stroke position is not misaligned. [Figure 5] This is an explanatory diagram illustrating how the cable's stroke position changes during operation when the cable's stroke position is misaligned. [Modes for carrying out the invention]

[0010] An electric parking brake device according to one embodiment of the present invention will be described below with reference to the drawings. However, the embodiments shown below are examples only, and the electric parking brake device of the present invention is not limited to the embodiments shown below.

[0011] As shown in Figure 1, the electric parking brake device 1 of this embodiment is a device that electrically operates and deactivates the parking brake PB by pulling and releasing the cable CA. The electric parking brake device 1 is not particularly limited and can be applied to a variety of vehicles, including large vehicles, medium-sized vehicles, and passenger cars, that are equipped with a parking brake according to the laws of each country, such as the Road Traffic Act.

[0012] The parking brake PB is activated when a predetermined load is applied by pulling the cable CA, and deactivated when the load is released by returning the cable CA. When activated, the parking brake PB suppresses the rotation of the vehicle's wheels to maintain the vehicle's stationary state when parked or stopped, and when deactivated, it allows the vehicle's wheels to rotate, thus allowing the vehicle to move.

[0013] The structure of the parking brake PB is not particularly limited, as long as it is configured to be activated by pulling the cable CA and deactivated by releasing the cable CA; any known parking brake can be used. In this embodiment, the parking brake PB comprises a braked member (e.g., a drum) and a braking member (e.g., a brake shoe) driven by the operation of the cable CA. The parking brake PB enters an activated state in which the rotation of the braked member is suppressed when the braking member is pressed against the braked member by pulling the cable CA and a predetermined load is applied. The parking brake PB, when activated, suppresses the rotation of the wheel. The parking brake PB, when released, enters an deactivated state in which the rotation of the braked member is permitted when the braking member is separated from the braked member by releasing the cable CA and the load is released. The parking brake PB, when deactivated, allows the rotation of the wheel. The braking member may be configured to be fixed to the vehicle's wheels, or it may be configured to be fixed so as to rotate together with a power transmission member that transmits power to the vehicle's wheels by rotating.

[0014] The cable CA that operates the parking brake PB is a flexible, elongated member, routed between the drive unit 6 (described later) and the parking brake PB of the electric parking brake device 1, and transmits the driving force of the drive unit 6 to the parking brake PB. When the cable CA is pulled, it applies a load to the parking brake PB, and when it is released, it reduces the load on the parking brake PB. As the cable CA, for example, the inner cable of a known control cable can be used. However, the cable CA only needs to be able to transmit the driving force of the drive unit 6 to the parking brake PB by being pulled and released, and it is also possible to substitute it with other elongated members such as a rod.

[0015] As shown in Figure 1, the electric parking brake device 1 includes a load detection unit 2 for detecting the load applied to the parking brake PB, a stroke position detection unit 3 for detecting the stroke position of the cable CA, a storage unit 4 for storing the detection results of the stroke position detection unit 3, and a control unit 5 for controlling the pulling and returning operations of the cable CA. The electric parking brake device 1 further includes a drive unit 6 for electrically pulling and returning the cable CA.

[0016] The drive unit 6 pulls the cable CA away from the parking brake PB (to the right in Figure 1) and returns the cable CA towards the parking brake PB (to the left in Figure 1). Hereinafter, the direction in which the cable CA is pulled will be referred to as the pull operation direction D1, the direction in which the cable CA is returned will be referred to as the return operation direction D2, and the pull operation direction D1 and the return operation direction D2 together will be referred to as the operation direction D. The drive unit 6 only needs to be able to pull and return the cable CA electrically, and its structure is not particularly limited. In this embodiment, as shown in Figure 1, the drive unit 6 includes a movable member 61 connected to the cable CA, a drive device 62 that generates a driving force to move the movable member 61 along the operation direction D, and a transmission member 63 that transmits the driving force of the drive device 62 to the movable member 61. In this embodiment, the movable member 61, the drive device 62, and the transmission member 63 are housed in a base BP such as a casing fixed to the vehicle.

[0017] The movable member 61 moves along the operating direction D by the driving force of the drive unit 62. As shown in Figure 1, the movable member 61 is connected to cable CA on one side of the operating direction D (towards the return operating direction D2) and to load detection unit 2 on the other side of the operating direction D (towards the pull operating direction D1). By moving in the pull operating direction D1 by the driving force of the drive unit 62, the movable member 61 pulls cable CA connected to the movable member 61. Also, by moving in the return operating direction D2 by the driving force of the drive unit 62, the movable member 61 returns cable CA connected to the movable member 61. Furthermore, the movable member 61 receives the reaction force of the load applied to the parking brake PB via cable CA and transmits it to load detection unit 2.

[0018] The configuration of the movable member 61 is not particularly limited, as long as it can operate the cable CA by moving along the operating direction D. In this embodiment, the movable member 61 comprises a first movable member 611, a second movable member 612, and a third movable member 613 along the operating direction D, as shown in Figure 1. The first movable member 611 and the second movable member 612 are connected to each other so as to be able to move relative to each other along the operating direction D, and the second movable member 612 and the third movable member 613 are connected to each other so as to be able to move relative to each other along the operating direction D. The first movable member 611 is connected to the cable CA on one side of the operating direction D (the return operating direction D2 side) and to the second movable member 612 on the other side of the operating direction D (the pull operating direction D1 side). The second movable member 612 is connected to the first movable member 611 on one side of the operating direction D (the return operating direction D2 side) and to the third movable member 613 on the other side of the operating direction D (the pull operating direction D1 side). The third moving member 613 is connected to the second moving member 612 on one side of the operating direction D (the return operating direction D2 side) and to the load detection unit 2 on the other side of the operating direction D (the pull operating direction D1 side). The moving members 61 are configured such that the first moving member 611 and the second moving member 612 move relative to each other along the operating direction D, and the second moving member 612 and the third moving member 613 move relative to each other along the operating direction D, so that the first moving member 611 and the third moving member 613 move forward and backward relative to the second moving member 612 along the operating direction D. The first moving member 611 and the third moving member 613 pull the cable CA by moving toward the second moving member 612 along the operating direction D, and return the cable CA by moving away from the second moving member 612 along the operating direction D. Furthermore, it is sufficient that the moving member 61 extends and retracts along the operating direction D as at least one of the first moving member 611 or the third moving member 613 moves along the operating direction D. For example, either the first moving member 611 or the third moving member 613 may be configured not to move relative to the second moving member 612.

[0019] In the present embodiment, the first moving member 611, the second moving member 612, and the second moving member 612 and the third moving member 613 are connected to each other such that when the second moving member 612 rotates about the axis X, the first moving member 611 and the third moving member 613 move relative to the second moving member 612 along the operation direction D. When the second moving member 612 rotates in one direction about the axis X, the first moving member 611 moves relative to the second moving member 612 in a direction approaching the second moving member 612 (pulling operation direction D1). When the second moving member 612 rotates in the other direction about the axis X, the first moving member 611 moves relative to the second moving member 612 in a direction away from the second moving member 612 (return operation direction D2). When the second moving member 612 rotates in one direction about the axis X, the third moving member 613 moves relative to the second moving member 612 in a direction approaching the second moving member 612 (return operation direction D2). When the second moving member 612 rotates in the other direction about the axis X, the third moving member 613 moves relative to the second moving member 612 in a direction away from the second moving member 612 (pulling operation direction D1). For that purpose, for example, the first moving member 611 and the third moving member 613 are embodied as screws, and the second moving member 612 is embodied as a nut.

[0020] The first moving member 611, the second moving member 612, and the third moving member 613 are all configured to be movable along the operation direction D with respect to the base BP (or the parking brake PB). However, since the third moving member 613 is biased and fixed to the pulling operation direction D1 side by a biasing member 22 described later of the load detection unit 2, at least unless it receives a load exceeding the biasing force of the biasing member 22 in the return operation direction D2 side, the movement along the operation direction D with respect to the base BP (or the parking brake PB) is suppressed. Therefore, when the moving member 61 expands and contracts, the first moving member 611 and the second moving member 612 move along the operation direction D with respect to the base BP (or the parking brake PB) unless the moving member 61 receives a load exceeding the biasing force of the biasing member 22 in the return operation direction D2 side. When the moving member 61 receives a load exceeding the biasing force of the biasing member 22 in the return operation direction D2 side, the movement of the first moving member 611 along the operation direction D with respect to the base BP (or the parking brake PB) is suppressed by the cable CA, and the second moving member 612 and the third moving member 613 move along the operation direction D with respect to the base BP (or the parking brake PB).

[0021] The drive device 62 generates a driving force for moving the moving member 61 along the operation direction D. In the present embodiment, the drive device 62 is embodied by a motor configured to be capable of forward and reverse rotational movement, and generates a driving force for rotating the second moving member 612 in one or the other direction around the axis X. The drive device 62 is connected to the moving member 61 via a transmission member 63, and transmits the driving force to the moving member 61 via the transmission member 63. However, the drive device may be embodied as a linear motor configured to be capable of linear movement in order to move the moving member 61 along the operation direction D. Further, the drive device may be directly connected to the cable CA and configured to directly move the cable CA without passing through the transmission member 63 and the moving member 61.

[0022] The transmission member 63 transmits the driving force of the drive unit 62 to the moving member 61. The transmission member 63 is not particularly limited as long as it can transmit the driving force of the drive unit 62 to the moving member 61, and can be composed of one or more driving force transmission members such as gears. In this embodiment, the transmission member 63 is connected to the second moving member 612 so as to transmit the driving force of the drive unit 62, thereby rotating the second moving member 612 around the axis X, and also so as to allow the movement of the second moving member 612 along the operating direction D relative to the transmission member 63. However, the transmission member 63 is not necessarily required, and the drive unit 62 and the moving member 61 may be directly connected without the transmission member 63.

[0023] The load detection unit 2 detects the load applied to the parking brake PB. The load applied to the parking brake PB is the load applied to the parking brake PB for the purpose of activating the parking brake PB. When the parking brake PB transitions from the deactivated state to the activated state, the load applied increases, and when it transitions from the activated state to the deactivated state, the load applied decreases. In this embodiment, the load applied to the parking brake PB corresponds to the pressing force generated between the braking member and the braked member. As shown in Figure 1, the load detection unit 2 is communicateably connected to the control unit 5 and is configured to transmit the detection result, i.e., information regarding the detected load, to the control unit 5.

[0024] The load detection unit 2 is not particularly limited in its configuration as long as it can detect the load applied to the parking brake PB. In this embodiment, as shown in Figure 1, the load detection unit 2 includes a driven member 21 that can move along the operating direction D in conjunction with the movement of a movable member 61 along the operating direction D, a biasing member 22 that biases the driven member 21 in the pulling operating direction D1, a first sensor element 23 (e.g., a magnet or Hall IC) that moves together with the driven member 21, and a second sensor element 24 (e.g., a Hall IC or magnet) that is fixedly attached to the base BP and interacts with the first sensor element 23. In the load detection unit 2, when the cable CA is pulled with a load exceeding the biasing force of the biasing member 22, the driven member 21 moves along the operating direction D toward the pulling operating direction D1 side together with the movable member 61 connected to the cable CA. At that time, the positional relationship between the first sensor element 23 that moves together with the driven member 21 and the second sensor element 24 fixedly attached to the base BP changes according to the magnitude of the load applied to the parking brake PB due to the pulling operation of the cable CA. The strength of the interaction between the first sensor element 23 and the second sensor element 24 changes in accordance with the change in the positional relationship between the first sensor element 23 and the second sensor element 24. Therefore, by measuring the strength of the interaction between the first sensor element 23 and the second sensor element 24, the positional relationship between the first sensor element 23 and the second sensor element 24 can be determined, and thereby the load applied to the parking brake PB by the operation of the cable CA can be determined. However, the load detection unit is not limited to the above example as long as it can detect the load applied to the parking brake PB, and may be configured to detect, for example, the load applied to the drive device 62 by the operation of the cable CA. Alternatively, the load detection unit may be configured to directly detect the load applied to the parking brake PB, for example, by detecting the pressing force generated between the braking member and the braked member of the parking brake PB.

[0025] The stroke position detection unit 3 detects the stroke position of the cable CA. The stroke position of the cable CA is the position of the cable CA in the operating direction D, and can be, for example, the position relative to the zero position which is the starting point of the stroke position. The zero position is a preset reference position for the stroke position of the cable CA, and can be, for example, the position at the furthest end on the return operation direction D2 side of the return operation range of the cable CA. For example, it can be set to the position of the cable CA when it has been returned by a predetermined stroke amount necessary to reliably release the parking brake PB, from the position of the cable CA when a predetermined maximum load (a load that is greater than the target load described later and is preset so as not to damage each element) is applied to the parking brake PB (maximum load position). The stroke position detection unit 3 is connected to the control unit 5 in a communicative manner and is configured to transmit the detection result, that is, information regarding the detected stroke position of the cable CA, to the control unit 5.

[0026] The stroke position detection unit 3 is not particularly limited in its configuration as long as it can detect the stroke position of the cable CA. In this embodiment, the stroke position detection unit 3 is configured to detect the amount of movement (stroke amount) of the cable CA by detecting the amount of drive displacement of the drive unit 6 (for example, the amount of movement of the moving member 61, or the rotational speed of the drive device 62 or transmission member 63). The stroke position detection unit 3 can detect the stroke position of the cable CA by detecting the amount of drive displacement from the drive displacement position corresponding to the zero position of the cable CA (for example, the position of the moving member 61 when the cable CA is at the zero position, or the rotational position of the drive device 62 or transmission member 63). The stroke position detection unit 3 can be embodied as a known rotary encoder attached to the drive device 62 or transmission member 63 of the drive unit 6, for example, as shown in Figure 1. The stroke position detection unit 3 detects the amount of movement of the moving member 61 moving along the operating direction D by counting the rotational speed of the drive device 62 or transmission member 63, and thereby detects the stroke amount of the cable CA in the operating direction D. The stroke position detection unit 3 detects the stroke position of the cable CA by counting the number of rotations of the drive unit 62 or transmission member 63 from the rotational position of the drive unit 62 or transmission member 63 corresponding to the zero position of the cable CA. In this embodiment, the stroke position detection unit 3 transmits the information regarding the counted rotations of the drive unit 62 or transmission member 63 to the control unit 5 as information regarding the stroke amount and stroke position of the cable CA. However, the stroke position detection unit can also be implemented by, for example, a position sensor that directly measures the position of a specific point on the cable CA.

[0027] The storage unit 4 stores the detection results of the stroke position detection unit 3. As shown in Figure 1, the storage unit 4 is communicated to the control unit 5 and configured to receive the detection results of the stroke position detection unit 3 from the control unit 5. In addition to the detection results of the stroke position detection unit 3, the storage unit 4 can also store the detection results of the load detection unit 2, preset load and stroke positions, and software configured to execute the operation of the control unit 5 when executed by the control unit 5. The storage unit 4 is not particularly limited as long as it can store the detection results of the stroke position detection unit 3, etc., and can be implemented using known non-volatile memory or volatile memory. For example, if the storage unit 4 is configured with non-volatile memory, it can continue to store the detection results of the stroke position detection unit 3, etc., even if the power supply of the electric parking brake device 1 (not shown) is turned off for maintenance or the like. In this embodiment, the storage unit 4 is configured to receive the detection results of the stroke position detection unit 3 via the control unit 5, but it may also be configured to be communicated to the stroke position detection unit 3 and receive the detection results directly from the stroke position detection unit 3.

[0028] The control unit 5 is configured to control the pulling and returning operations of the cable CA. In this embodiment, as shown in Figure 1, the control unit 5 is communicatively connected to the drive unit 6 and configured to transmit commands to the drive unit 6 for operating the cable CA. The control unit 5 is also communicatively connected to the load detection unit 2 and the stroke position detection unit 3 and is configured to control the operation of the load detection unit 2 and the stroke position detection unit 3, as well as to receive detection results from the load detection unit 2 and detection results from the stroke position detection unit 3. The control unit 5 is configured to control the pulling and returning operations of the cable CA based on the detection results from the load detection unit 2 and the detection results from the stroke position detection unit 3, as will be described in detail below. The control unit 5 is not particularly limited as long as it can control the pulling and returning operations of the cable CA, and can be configured by, for example, a known central processing unit (CPU). The control unit 5 is configured so that, when executed by the control unit 5, it can run software capable of executing the operations of the control unit 5 described below.

[0029] When the control unit 5 activates the parking brake PB, as shown in Figure 2, it causes the drive unit 6 to pull the cable CA until it is determined that the parking brake PB is activated. More specifically, when the control unit 5 starts operation, for example by operating a switch (not shown), the drive unit 6 starts pulling the cable CA at the command of the control unit 5 (step S11), and regardless of whether steps S12 and S13 described later occur, the drive unit 6 continues pulling the cable CA until it is determined that the parking brake PB is activated (steps S14, S15). When it is determined that the parking brake PB is activated, the drive unit 6 stops pulling the cable CA. The determination of whether or not the parking brake PB is activated (step S15) is not particularly limited and can be performed, for example, by detecting whether or not a preset target load is applied to the parking brake PB using the load detection unit 2. The target load is set within a range that can maintain the vehicle's stationary state when applied to the parking brake PB. The target load can be set appropriately according to the conditions when the vehicle is parked, such as the slope of the parking location or the weight of the cargo loaded on the vehicle. When the load detection unit 2 detects that the target load has been applied to the parking brake PB, the drive unit 6 stops pulling the cable CA. When the drive unit 6 stops pulling the cable CA, the stroke position of the cable CA detected by the stroke position detection unit 3 may be stored in the storage unit 4 as the operating position corresponding to the operating state of the parking brake PB. Alternatively, the stroke position of the cable CA before the pulling operation may be stored in the storage unit 4 as the pre-operation position.

[0030] As shown in steps S12 and S13 of Figure 2, the control unit 5 stores in the storage unit 4 the stroke position at which the load detection unit 2 detects the drag judgment criterion load when the parking brake PB is activated, as the drag judgment criterion position. The drag judgment criterion position is the stroke position of the cable CA used to determine whether or not the parking brake PB is in a dragging state when the parking brake PB is released, as will be described in detail below. The drag judgment criterion position is the stroke position of the cable CA detected when a preset drag judgment criterion load is applied to the parking brake PB, and it changes according to the drag judgment criterion load, and may also change due to changes in the arrangement of the cable CA, etc., even with the same drag judgment criterion load. The parking brake PB is in a dragging state when the parking brake PB is not in a completely released state, and a load of a certain amount or more (for example, 100N or more) remains on the parking brake PB. If the cable CA is located at a stroke position within a predetermined range relative to the drag judgment reference position, it can be determined that a certain amount of load remains on the parking brake PB, and that the parking brake PB is in a dragging state.

[0031] The drag judgment criterion load, which is the load applied to the parking brake PB when the cable CA is located at the stroke position designated as the drag judgment criterion position, is set within a range greater than the minimum load that the load detection unit 2 can detect and smaller than the target load required to activate the parking brake PB. By setting the drag judgment criterion load smaller than the target load, unlike when the drag judgment criterion load is set to the target load, the drag judgment criterion load can be set to a fixed value even if the target load is changed depending on the state of the vehicle when it is parked or stopped. This allows a predetermined range for the drag judgment criterion position corresponding to the drag judgment criterion load to be set to a fixed value, and there is no need to change the predetermined range for each changing target load, making it easier to determine whether the parking brake PB is dragging. Furthermore, by setting the drag judgment criterion load smaller than the target load, the load on the cable CA is reduced when detecting the drag judgment criterion position, thereby suppressing the elongation of the cable CA and reducing the detection error of the stroke position due to the elongation of the cable CA, thus enabling more accurate detection of the drag judgment criterion position.

[0032] The detection of the drag judgment reference position only needs to be performed when the parking brake PB is activated, that is, when a load is applied to the parking brake PB, and may be performed when the cable CA is pulled or when the cable CA is returned. In this embodiment, as shown in Figure 2, the detection of the drag judgment reference position is performed when the cable CA is pulled to activate the parking brake PB. For example, if the parking brake PB has a configuration in which the braking member is biased in the direction away from the braked member, then when the cable CA is returned to deactivate the parking brake PB, the biasing force of the parking brake PB that biases the braking member may cause the cable CA to be biased in the return operation direction D2. In that case, the moving member 61 and the driven member 21 are also biased in the return operation direction D2, so the load on the parking brake PB cannot be accurately detected, and there is a risk that the drag judgment reference position cannot be accurately detected. By detecting the drag judgment reference position during the pulling operation of the cable CA, the drag judgment reference load can be detected more accurately, and the drag judgment reference position can be detected more accurately, even when, for example, the braking member of the parking brake PB is biased in a direction away from the braked member.

[0033] In this embodiment, the control unit 5 stores the drag judgment reference position corresponding to the drag judgment reference load in the storage unit 4 each time the parking brake PB is activated. By storing the drag judgment reference position in the storage unit 4 each time the parking brake PB is activated, the drag state of the parking brake PB can be accurately determined each time the parking brake PB is released after activation. However, the control unit 5 may only detect the drag judgment reference position and store the drag judgment reference position in the storage unit 4 after performing work that may cause the stroke position of the cable CA to shift, such as maintenance.

[0034] When the control unit 5 releases the parking brake PB, it causes the drive unit 6 to retract the cable CA until it is determined that the parking brake PB has been fully released, as shown in Figure 3. More specifically, when the control unit 5 starts operation, for example by operating a switch (not shown), the drive unit 6 starts retracting the cable CA at the command of the control unit 5 (step S21), and the drive unit 6 continues retracting the cable CA until it is determined that the parking brake PB has been fully released (steps S21, S22). Once it is determined that the parking brake PB has been fully released, the drive unit 6 stops retracting the cable CA. The determination of whether the release of the parking brake PB is complete (step S22) is not particularly limited, and can be performed by determining whether the amount of return operation of the cable CA satisfies predetermined conditions, for example, by determining whether the cable CA has been returned by the amount of stroke when the cable CA was pulled to activate the parking brake PB, that is, by the amount of stroke required to return the cable CA to its position before activation, or by determining whether the cable CA has been returned by the amount of stroke required to return it to a predetermined stroke position at the start of the return operation of the cable CA. When the stroke position detection unit 3 detects that the cable CA has been returned by an amount of stroke that can be estimated to be the amount by which the brake member pressed against the braked member has moved away from the braked member, the control unit 5 determines that the release of the parking brake PB is complete.

[0035] As shown in Figure 3, when the parking brake PB is released, the control unit 5 determines whether the stroke position of the cable CA at the time the release of the parking brake PB is determined to be complete is within a predetermined range with respect to the drag determination reference position described above (step S23). The predetermined range with respect to the drag determination reference position refers to the range between the drag determination reference position and a stroke position that is a predetermined stroke amount away from the drag determination reference position in the return operation direction D2. The predetermined stroke amount at this time can be the stroke amount from the drag determination reference position to the stroke position of the cable CA where the parking brake PB is released, and for example, it can be the outermost position on the pull operation direction D1 side of the stroke position of the cable CA where the parking brake PB is released.

[0036] The control unit 5 determines whether the stroke position of the cable CA when it determines that the release of the parking brake PB is complete is within a predetermined range relative to the drag determination reference position. This allows the control unit 5 to detect the drag state of the parking brake PB without the load detection unit 2 detecting the load of the parking brake PB. For example, in large vehicles where it is necessary to increase the load during operation, if a load detection unit with a range set to large loads is used to perform control according to the vehicle's condition when the parking brake PB is in the activated state, it may be difficult to accurately detect small loads such as the drag state of the parking brake PB, and it may be difficult to determine the drag state of the parking brake PB by detecting the load of the parking brake PB. In such cases, the determination of the drag state of the cable CA in this embodiment can be suitably applied. The control unit 5 may also be configured to determine the drag state of the parking brake PB based on the load applied to the parking brake PB in combination with the above determination. For example, the control unit 5 may be configured to determine the drag state of the parking brake PB based on the detection result of the load detection unit 2 when the load remaining on the parking brake PB is large, and based on the stroke position of the cable CA when the load remaining on the parking brake PB is small. This makes it possible to determine the drag state of the parking brake PB over a wider load range.

[0037] The above-mentioned determination of the parking brake PB dragging state is not particularly limited, but it is effective when, for example, the mounting position of the cable CA to the parking brake PB or base BP changes due to maintenance, and the stroke position of the cable CA stored in the memory unit 4 deviates from the actual stroke position. The effect will be explained below with reference to Figure 4, which shows the change in the stroke position during operation when the stroke position of the cable CA is not deviated, and Figure 5, which shows the change in the stroke position during operation when the stroke position of the cable CA is deviated.

[0038] If the stroke position of cable CA is not misaligned, as shown in Figure 4, the actual stroke position of cable CA (pre-operation position) before the parking brake PB is activated coincides with the stroke position of cable CA (pre-operation position) recognized by the control unit 5. When cable CA is pulled to activate the parking brake PB, cable CA is pulled from the pre-operation position until the drag judgment criterion load is applied to the parking brake PB, reaching the drag judgment criterion position, and then pulled until the target load is applied to the parking brake PB, reaching the activation position. At this time, since the actual pre-operation position of cable CA and the pre-operation position of cable CA recognized by the control unit 5 coincide, the actual drag judgment criterion position and activation position of cable CA also coincide with the drag judgment criterion position and activation position recognized by the control unit 5. Next, in order to release the parking brake PB, the cable CA is returned by an amount of stroke that can be estimated to be the amount by which the braking member has separated from the braked member from the state in which the braking member was pressed against the braked member, for example, the amount of stroke when the cable CA is pulled (see "release operation" in the figure), and the cable CA returns to its position before operation (release completion position). At this time, the actual position of the cable CA before operation and the position of the cable CA before operation recognized by the control unit 5 match, so the actual release completion position of the cable CA matches the release completion position of the cable CA recognized by the control unit 5. When the cable CA reaches the release completion position, it is determined whether the release completion position is within a predetermined range from the drag judgment reference position (see "predetermined range" in the figure). In the illustrated example, the release completion position is not within the predetermined range from the drag judgment reference position, so it is determined that the parking brake PB is not in a dragging state.

[0039] If the stroke position of cable CA is misaligned, as shown in Figure 5, the actual stroke position of cable CA (pre-operation position) will be different from the stroke position of cable CA recognized by the control unit 5 before the parking brake PB is activated. For example, suppose the actual stroke position of cable CA (pre-operation position) is shifted by a shift amount d towards the pulling operation direction D1 due to maintenance or other reasons (see "A" in the figure). At this time, the control unit 5 recognizes the stroke position of cable CA stored in the memory unit 4 before the shift in the cable CA's stroke position, and therefore recognizes that cable CA is in the stroke position before the shift. From this state, when cable CA is pulled to activate the parking brake PB, cable CA moves from the pre-operation position to the drag judgment reference position corresponding to the drag judgment reference load, and then to the operating position corresponding to the target load. Since the drag judgment criterion load and target load do not change before and after the shift in the stroke position of the cable CA, the corresponding drag judgment criterion position and operating position where the actual cable CA is located do not change before and after the shift in the stroke position of the cable CA (comparison of Figure 4 and Figure 5). At this time, the actual amount of stroke moved by the cable CA (the distance between the position before the parking brake PB is activated, indicated by "A" in the figure, and the operating position where the parking brake PB is activated) is smaller by a shift amount d compared to before the shift in the stroke position of the cable CA. Therefore, the control unit 5 recognizes the drag judgment criterion position and operating position as the position on the D2 side of the return operation direction by a shift amount d' (the position before the shift in the stroke position) compared to the actual stroke position of the cable CA (see "B" and "C" in the figure). Next, in order to release the parking brake PB, the cable CA is returned by an amount of stroke that can be estimated to be the amount by which the braking member has separated from the braked member from the state in which the braking member was pressed against the braked member, for example, the amount of stroke when the cable CA is pulled (see "Release Operation" in the diagram), and the cable CA returns to its position before activation (release completed position).At this time, the actual release position of cable CA is shifted by a shift amount d toward the pulling direction D1 compared to before the cable CA's stroke position shifted (see "A" in the figure). As a result, the actual release position of cable CA falls within a predetermined range (see "determined range" in the figure) from the actual drag judgment reference position, and the parking brake PB is actually in a dragging state. On the other hand, the drag judgment reference position of cable CA recognized by the control unit 5 is shifted by a shift amount d' toward the returning direction D2 compared to before the cable CA shifted (see "B" in the figure). As a result, the release position recognized by the control unit 5 falls within a predetermined range (see "determined range" in the figure) from the drag judgment reference position recognized by the control unit 5, and the control unit 5 can determine that the parking brake PB is in a dragging state.

[0040] As described above, the determination of the dragging state of the parking brake PB in the electric parking brake device 1 of this embodiment can be suitably applied when, for example, the mounting position of the cable CA changes due to maintenance, and the stroke position of the cable CA stored in the memory unit 4 deviates from the actual stroke position. In addition to maintenance, the stroke position of the cable CA stored in the memory unit 4 may also deviate from the actual stroke position due to cable CA elongation or misalignment between components of the electric parking brake device 1, and in such cases as well, the determination of the dragging state of the parking brake PB in this embodiment can be suitably applied.

[0041] As described above, the control unit 5 only needs to be configured to determine whether the stroke position of the cable CA at the time of complete release is within a predetermined range from the drag detection reference position, and its operation after the determination is not particularly limited. For example, as shown in Figure 3, when the control unit 5 determines that the stroke position of the cable CA is within a predetermined range with respect to the drag detection reference position, it may be configured to display a drag detection warning on a display unit (not shown), or it may be configured to reset the zero position (step S24). The zero position can be reset, for example, by setting the zero position to the position of the cable CA when it is returned by a predetermined stroke amount necessary to reliably release the parking brake PB from the position of the cable CA when the maximum load is applied to the parking brake PB (maximum load position). Specifically, in the case of Figure 5, when the stroke position of the cable CA is shifted, the maximum load applied to the parking brake PB does not change before and after the shift in the stroke position of the cable CA, so the maximum load position corresponding to the actual maximum load of the cable CA hardly changes before and after the shift in the stroke position of the cable CA (comparison of Figure 4 and Figure 5). The zero position is reset by applying the maximum load to the parking brake PB and then moving the cable CA back by a predetermined stroke amount from the position of the cable CA when the maximum load is applied to the parking brake PB (maximum load position). The position of the cable CA at the time of the return operation is set as the new zero position. This allows the control unit 5 to accurately recognize the stroke position of the cable CA. The reset zero position may be stored in the memory unit 4.

[0042] As shown in Figure 3, the control unit 5 may be configured to reset the zero position of the cable CA, and then, based on the reset zero position, perform a pulling operation in the pulling direction D1 by a predetermined stroke amount (for example, 5 mm) to return the cable CA to its pre-operation position (step S25). Note that the pre-operation position in step S25 may be the position after the zero position has been reset, and does not necessarily have to be the position where the parking brake PB is located before operation. As a result, the stroke position of the cable CA is no longer within a predetermined range with respect to the drag judgment reference position, and the dragging state of the parking brake PB is eliminated.

[0043] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above. The embodiments described above mainly describe an invention having the following configuration.

[0044] (1) An electric parking brake device that electrically activates and deactivates the parking brake by pulling and releasing a cable, wherein the electric parking brake device is A load detection unit that detects the load applied to the parking brake, A stroke position detection unit for detecting the stroke position of the cable, A storage unit for storing the detection result of the stroke position detection unit, A control unit that controls the pulling and returning operations of the cable. Equipped with, The control unit, When the parking brake is activated, the stroke position at which the load detection unit detects the drag judgment criterion load is stored in the storage unit as the drag judgment criterion position. When the parking brake is released, it is determined whether the stroke position of the cable at the time the release of the parking brake is determined to be complete is within a predetermined range relative to the drag determination reference position. Electric parking brake system.

[0045] (2) The control unit, Each time the parking brake is activated, the drag judgment reference position corresponding to the drag judgment reference load is stored in the storage unit. The electric parking brake device described in (1).

[0046] (3) The memory unit is Non-volatile memory, The electric parking brake device described in (1) or (2).

[0047] (4) The control unit, When it is determined that the stroke position of the cable is within the predetermined range relative to the drag judgment reference position, the zero position, which is the outermost position of the cable's return operation range and the starting point of the stroke position, is configured to be reset. An electric parking brake device as described in any one of (1) to (3). [Explanation of symbols]

[0048] 1. Electric parking brake system 2. Load detection unit 21 Driven member 22 Biasing member 23 First Sensor Element 24. Second Sensor Element 3. Stroke position detection unit 4 Storage section 5. Control Unit 6 Drive Unit 61 Moving member 611 First movable member 612 Second movable member 613 Third movable member 62 Drive unit 63 Transmission Members BP base CA Cable d Shift amount d' Shift amount recognized by the control unit D Operation direction D1 Pull operation direction D2 Return operation direction PB Parking Brake S11 Steps to pull and operate the cable S12 Step to determine whether or not the parking brake is subjected to a drag judgment criterion load. S13 Step of storing the cable stroke position when the drag judgment criterion load is applied as the drag judgment criterion position in the memory unit. S14 Steps to pull and operate the cable S15 Step to determine whether the parking brake is engaged or not. Steps to reconnect and operate the S21 cable. S22 Step to determine whether the parking brake has been fully released. S23 Step to determine whether the stroke position of the cable is within a predetermined range relative to the drag judgment reference position. S24 Step to reset the zero position S25 Step to return the cable to its pre-operation position based on the reset zero position. X axis of the moving member

Claims

1. An electric parking brake device that electrically activates and deactivates the parking brake by pulling and releasing a cable, wherein the electric parking brake device is A load detection unit that detects the load applied to the parking brake, A stroke position detection unit for detecting the stroke position of the cable, A storage unit for storing the detection result of the stroke position detection unit, A control unit that controls the pulling and returning operations of the cable. Equipped with, The control unit, When the parking brake is activated, the stroke position at which the load detection unit detects the drag judgment criterion load is stored in the storage unit as the drag judgment criterion position. When the parking brake is released, it is determined whether the stroke position of the cable at the time the release of the parking brake is determined to be complete is within a predetermined range relative to the drag determination reference position. Electric parking brake system.

2. The control unit, Each time the parking brake is activated, the drag judgment reference position corresponding to the drag judgment reference load is stored in the storage unit. The electric parking brake device according to claim 1.

3. The aforementioned storage unit is Non-volatile memory, The electric parking brake device according to claim 1.

4. The control unit, When it is determined that the stroke position of the cable is within the predetermined range relative to the drag judgment reference position, the zero position, which is the outermost position of the cable's return operation range and the starting point of the stroke position, is configured to be reset. The electric parking brake device according to claim 1.

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