WO2010013128A2

WO2010013128A2 - Lever device and parking brake apparatus

Info

Publication number: WO2010013128A2
Application number: PCT/IB2009/006406
Authority: WO
Inventors: Takumi Kawata
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2008-08-01
Filing date: 2009-07-30
Publication date: 2010-02-04
Also published as: WO2010013128A3; JP2010036642A

Abstract

A lever device (100) includes: a bracket (18) fixed to a vehicle; a lever (12) pivotally held by the bracket (18) and pivoted to apply tension to a wire (19) connected to brake units (22, 23) of wheels, thereby applying a brake to the wheels; a pole lever (14) engaged with one of teeth (15) formed in the bracket (18) to keep the lever (14) at a selected pivot angle and pivotally held by the lever (12); a release rod (13) connected to the pole lever (14),- and a switch (11) that pushes the release rod (13) to disengage the pole lever (14) from the tooth (15). The interval between part of the teeth (15), with which the pole lever (14) is engaged when the lever (12) is at a first pivot angle, is wider than the interval between another part of the teeth (15), with which the pole lever (14) is engaged when the lever (12) is at a second pivot angle that is larger than the first pivot angle.

Description

LEVER DEVICEAND PARKING BRAKE APPARATUS

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates to a lever device that is used to operate a brake unit which applies a brake to a wheel. More specifically, the invention relates to a lever device that keeps a brake unit actuated with the use of a ratchet mechanism, and a parking brake apparatus.

2. Description of the Related Art

[0002] A parking brake apparatus is used to keep a vehicle stationary while the vehicle is parked or stopped. Some parking brake apparatuses are actuated when a driver manually operates a lever. In these parking brake apparatuses, a so-called ratchet mechanism is usually used to maintain a braking force. In the parking brake apparatus, the leverage is fixed. Accordingly, the same operation amount is required regardless of whether the lever is in an initial pivot range in which application of a braking force is started or in a pivot range in which a sufficient braking force is obtained. Therefore, for example, Japanese Patent Application Publication No. 58-50025 (JP-A-58-50025) describes a parking brake apparatus in which a low leverage is used to suppress a pivot loss of the lever when the lever is in the initial pivot range and a high leverage is used to cause the lever to be pivoted with a small force when the lever is in the pivot range in which a large force is usually required to cause the lever to be pivoted.

[0003] FIG 5 shows an example of a lever device of a parking brake apparatus according to a related art, which includes a latchet mechanism. A bracket 104 and a circular fixed member 105 are fixed to a vehicle body. Multiple teeth that are formed in the fixed member 105 and teeth 106 that are formed in a lever 101 mesh with each other. The lever 101 is allowed to move along the periphery of the fixed memberlO5, because the lever 101 is held by a pin 107 while the teeth of the fixed member 105 and the teeth 106 of the lever mesh with each other. With this structure, when the lever 101 is in the initial pivot range, it is possible to apply a tension to a wire 108 by moving the lever 101 a short travel distance because the leverage is low. The position at which the teeth of the fixed member 105 and the teeth 106 of the lever mesh with each other is lower when the lever 101 is in pivot range in which a sufficient braking force is obtained than when the lever 101 is in the initial pivot range. Therefore, the leverage is made higher, which makes it possible to apply a tension to the wire 108 with a smaller force when the lever 101 is in pivot range in which a sufficient braking force is obtained.

[0004] However, in the parking brake apparatus described in JP-A-58-50025, the lever 101 is moved a short travel distance when the lever 101 is in the initial pivot range, and needs to be moved a long travel distance when the lever 101 is in the pivot range in which a sufficient braking force is obtained. Therefore, operability of the lever 101 may be lower when the lever 101 in the pivot range in which the lever 101 comes close to the driver's body. Namely, as the lever 101 approaches the driver's body, the operability may be reduced because the lever 101 needs to be moved a longer travel distance.

SUMMARY OF THE INVENTION

[0005] This invention provides a lever device and a parking brake apparatus that will not decline the operability even if the lever is in the position that generates high load during the high load pivot range

[0006] An aspect of the invention relates to a lever device that includes: a bracket that is fixed to a vehicle; a lever that is pivotally held by the bracket and that is pivoted to apply a tension to a wire connected to a brake unit of a wheel, thereby applying a brake to the wheel; a pole lever that is engaged with one of teeth formed in the bracket to keep the lever at a selected pivot angle and that is pivotally held by the lever; a release rod that is connected to the pole lever; and a switch that pushes the release rod to disengage the pole lever from the one of the teeth. In this lever device, the intervals between the teeth formed in the bracket are set in such a manner that the interval between part of the teeth, with which the pole lever is engaged when the lever is at a first pivot angle, is wider than the interval between another part of the teeth, with which the pole lever is engaged when the lever is at a second pivot angle that is larger than the first pivot angle.

[0007] According to the aspect of the invention, as the pivot angle of the lever becomes larger, the interval between the latchet teeth becomes narrower. Therefore, it is possible to actuate a parking brake apparatus efficiently because sufficient operability is maintained regardless of whether the lever is at a position at which a low load is applied to a driver or at a position at which a high load is applied to the driver.

BRIEF DESCRIPTION OF THE DRAWINGS [0008] The foregoing and further features and advantages of the invention will become apparent from the following description of an example embodiment with reference to the accompanying drawings, wherein like numerals are used to represent like elements, and wherein:

FIG 1 is a view showing an example of the skelton framework of a lever device of a parking brake apparatus;

FIG 2 is a view showing an example of the skelton framework of a parking brake apparatus;

FIGs. 3A and 3B are views each schematically showing a travel distance of a lever in a pivot range near the on-position and a travel distance of the lever in a pivot range near the off-position;

FIGs. 4A and 4B show several modifications of the lever device; and

FIG. 5 is a view showing an example of a lever device of a parking brake apparatus according to a related art, which has a latchet mechanism.

DETAILED DESCRIPTION OF THE EMBODIMENT

[0009] Hereafter, an embodiment of the invention will be described with reference to the accompanying drawings. FIG 1 is a view showing an example of the skelton framework of a lever device 100 of a parking brake apparatus according to the embodiment of the invention. In the lever device 100, the intervals between latchet teeth 15 of a latchet mechanism are not regular intervals. The lever 12 is at a large pivot angle when the lever 12 has been pivoted by a large amount from the off-position, whereas the lever 12 is at a small pivot angle when the lever 12 has been pivoted by a small amount from the off-position. The notch interval between some of the Iatchet teeth 15, with which a pole lever 14 is engaged when the lever 12 is at a large pivot angle, is narrower than the notch interval between the other Iatchet teeth 15, with which the pole lever 14 is engaged when the lever 12 is at a small pivot angle.

[0010] In other words, the notch interval is wide in the initial pivot range (hereinafter, referred to as "pivot range near the off-position"), and the notch interval is narrow in the pivot range in which a sufficient braking force is applied to a wheel (hereinafter, referred to as "pivot range near the on-position"). With this structure, the travel distance of the lever 12 per one notch is shorter in the pivot range near the on-position than in the pivot range near the off-position.

[0011] Because the number of notches is small in the pivot range near the off-position in which a low load is placed on a driver, the driver can clearly recognize the off-position. As a result, it becomes easier to prevent brake dragging, in other words, it becomes easier to prevent occurrence of the situation where the brake is not actually released although the driver thinks that the brake is released. In addition, because the driver needs to move the lever 12 a long distance to move it from the off-position to the first notch from the off-position, it becomes easier for the driver, who recognizes the on-position based on the number of notches, to recognize the on-position. It is possible to prevent occurrence of the situation where a parking brake is not actually applied and the vehicle moves down although the driver thinks that the parking brake is applied.

[0012] In the pivot range near the on-position in which a high load is placed on the driver, the travel distance of the lever 12 per one notch is shorter and therefore the number of notches within a certain travel distance is larger than in the pivot range near the off-position. As a result, it is easier to obtain a desired braking force based on an operation force applied by the driver.

[0013] The lever device 100 includes a bracket 18 that is fixed to a vehicle body, the lever 12 that is pivotally held by a pin 17, a release rod l£-that is movable with respect to the lever 12, the pole lever 14 that is connected to the release rod 13, and a wire 19 that is fixed at one end to the lever 12 with a nut 16. The other end of the wire 19 is connected to a brake unit.

[0014] The latchet teeth 15 are formed in the bracket 18 at a face that faces the pole lever 14. The pole lever 14 is pivotally supported by a pin 21, and is biased so that a hook portion 14a of the pole lever 14 is engaged with one of the latchet teeth 15. Accordingly, the pole lever 14 always meshes with one of the latchet teeth 15.

[0015] The interval between the latchet teeth 15 becomes gradually narrower toward the top of the vehicle body. In the actual bracket 18, the line that connects the gums of the latchet teeth 15 is in the form of a segment of a circle of which the center corresponds to the pin 17. The pivot angle of the lever 12 is the smallest when the lever is at the off-position, and becomes larger as the lever 12 is pivoted toward the on-position. Therefore, the interval between the latchet teeth 15 becomes narrower as the pivot angle of the lever 12 becomes larger.

[0016] When the driver operates the lever 12 upward, the lever 12 pivots about the pin 17 to pull the wire 19 toward the front of vehicle, and the brake unit that is connected the other end of the wire 19 applies a brake to the vehicle (hereinafter, referred to as "brake unit is actuated"). The latchet tooth 15 is formed in such a manner that a face that extends from the gum between this latchet tooth 15 and another latchet tooth 15, which is adjacent to this latchet tooth 15 and closer to the front of the vehicle, is inclined at a small angle, and a face that extends from the gum between this latchet tooth 15 and another latchet tooth 15, which is adjacent to this latchet tooth 15 and closer to the rear of the vehicle, is inclined at a large angle. Therefore, the hook portion 14a can climb over the latchet tooth 15 easily when the lever 12 is operated upward. However, even if the driver takes his/her hand off the lever 12, the hook portion 14a cannot climb over the latchet tooth 15 in the reverse direction. Accordingly, it is possible to keep the brake unit actuated.

[0017] To de-actuate the brake unit, the driver pushes a release button 11. Then, the pole lever 14 is allowed to pivot about the pin 21 against the biasing force. Accordingly the hook portion 14a is disengaged from the latchet tooth 15.^ As a result, it is possible to return the lever 12 to the off-position.

[0018] The parking brake apparatus that includes the lever device 100 will be described briefly. FIG 2 is a view showing an example of the skelton framework of the parking brake apparatus. The parking brake apparatus includes the lever device 100, a rear right wheel RR, a rear left wheel RL, a brake unit 22 that applies a braking force to the rear right wheel RR, and a brake unit 23 that applies a braking force to the rear left wheel RL. The lever device 100 is connected to the brake units 22 and brake unit 23 via an equalizer 30. The equalizer 30 distributes the tension generated by the lever device 100 to two cables, that is, a cable 25 and a cable 26, equally. In the embodiment of the invention shown FIG 2, the brake units 22 and 23 are fitted to the rear wheels. Alternatively, the brake units 22 and 23 may be fitted to the front wheels.

[0019] Drum brake units are used as the brake units 22 and 23 in the embodiment of the invention. Each of the brake units 22 and 23 includes a cylindrical brake drum 31 that is fixed a wheel and rotates together with the wheel, a pair of brake shoes provided in the brake drum 31, brake linings 33 that are fixed the brake shoes 32 and apply a braking force to the wheel when pushed against the brake drum 31, etc.

[0020] One end of a brake shoe lever 35 is rotatably connected to one of the paired brake shoes 32 by a pin, and the other end of the brake shoe lever 35 is connected to one end of the cable 25 (26). The brake shoe lever 35 is connected to the other brake shoe 32 via a shoe strut 34. With this structure, when the wire 19 is pulled by the lever device 100, the distance between the paired brake shoes 32 is increased by the brake shoe lever 35 and the shoe strut 34, and the brake linings 33 are pushed against the inner face of the brake drum 31. As a result, a braking force is applied to the wheel.

[0021] The operation of the lever device 100 will be described below. FlG. 3A is a view schematically showing the travel distance of the lever 12 in the pivot range near the on-position and the travel distance of the lever 12 in the pivot range near the off-position. In order to compare the embodiment of this invention with a related art, FIG 3B, which shows the travel distance of a lever in a lever device 100 according to the related art, will be used. FIG. 3B is a view schematically showing the travel distance of :the lever in the pivot range near the on-position and the travel distance of the lever in the pivot range near the off-position.

[0022] As described above, in the lever device 100 according to the embodiment of the invention, the notch interval between the latchet teeth 15 in the pivot range near the off-position differs from the notch interval between the latchet teeth 15 in the pivot range near the on-position. On the other hand, in the lever device 100 according to the related art, the notch interval between the latchet teeth 15 is substantially uniform from the off-position to the on-position. Accordingly, in the lever device 100 according to the related art, a travel distance A' of the lever per one notch in the pivot range near the on-position is substantially equal to a travel distance B' of the lever per one notch in the pivot range near the off-position (travel distance A' » travel distance B').

[0023] In contrast, in the lever device 100 according to the embodiment of the invention shown in FIG 3A, the notch interval between the latchet teeth 15 is wide in the pivot range near the off-position, and the notch interval between the latchet teeth 15 is narrow in the pivot range near the on-position. Therefore, a travel distance A that needs to be traveled by the lever 12 to cause the hook portion 14a to climb over the one notch in the pivot range near the off-position is longer than a travel distance B that needs be traveled by the lever 12 to cause the hook portion 14a to climb over one notch in the pivot range near the on-position (travel distance A > travel distance B).

[0024] The following is an example of the relationship among the travel distances A, B, A' and B'. The travel distance B is shorter than the travel distance A' (or B'), and the travel distance A' (or B') is shorter than the travel distance A (B < A' (B') < A). The travel distance A may be 1.5 times to several times as long as the travel distance A' (B'), and the travel distance B may be three-fourths to one-fifths of the travel distance A' (B').

[0025] If the travel distance of the lever 12 per one notch in the pivot range near the off-position is long, a higher load is placed on the driver to cause the hook portion 14a to climb over one notch when the parking brake apparatus is actuated. As a result, it becomes easier for the driver, who determines whether the parking brake apparatus is

^actuated based on the number of notches, to determine whether the parking brake apparatus is actuated. It is therefore possible to prevent the vehicle from moving down.

[0026] Further more, when the parking brake apparatus is de-actuated, the driver can clearly recognize the off-position. Therefore, it becomes easier to prevent brake dragging, in other words, it becomes easier to prevent the vehicle from moving with the parking brake still actuated. As a result, it is possible to reduce the wearing away of the brake shoes and to improve the fuel efficiency.

[0027] If the travel distance of the lever 12 per one notch in the pivot range near the on-position is short, a load that is placed on the driver to cause the hook portion 14a to climb over one notch is low. Therefore, it is possible to cause the hook portion 14a to climb over more notches at the same load in the pivot range near the on-position, in which a higher load is placed on the driver, than in the pivot range near the off-position. For example, it becomes easier for a driver having a weak force to engage the pole lever 14 with the ratchet tooth 15 at a pivot angle at which a sufficient braking force is obtained.

[0028] FIG 4 shows several modifications of the lever device 100. In FIG 3A, the notch interval between the latchet teeth 15 becomes gradually narrower. However, as shown in FIG 4A, the notch interval between the latchet teeth 15 may become narrower in a stepwise manner. In FIG. 4A, the notch interval between the latchet teeth 15 is changed in three steps. Alternatively, the notch interval between the latchet teeth 15 may be changed in two steps or four steps. If the notch interval between the latchet teeth 15 becomes narrower in a stepwise manner, it is easier to suppress cost increase.

[0029] In the pivot range near the off-position in which the travel distance per one notch should be long, the latchet teeth 15 need not be closely adjacent to each other. As shown in FIG4B, in the pivot range near the off-position, some of the latchet teeth 15 may be omitted. Because some of the latchet teeth 15 are omitted, it is easier for the driver to determine whether the parking brake apparatus is actuated and to recognize the off-position. In the pivot range near the off-position, the driver can operate the lever 12 at a low load. Therefore, even if some of the latchet teeth 15 are omitted, for example, the problem that the hook portion 14a cannot climb over one notch does not occur.

[0030]ι In. the embodiments of the invention, the pivot angle of the lever 12 in the pivofr range near the off-position, that is, the pivot angle at which the travel distance of the lever 12 per one notch is the travel distance A may be referred to as a first pivot angle, and the pivot angle of the lever 12 in the pivot range near the on-position, that is, the pivot angle at which the travel distance of the lever 12 per one notch is the travel distance B will be ' referred to as a second pivot angle.

Claims

Claims:

1. A lever device that includes: a bracket that is fixed to a vehicle; a lever that is pivotally held by the bracket and that is pivoted to apply a tension to a wire connected to a brake unit of a wheel, thereby applying a brake to the wheel; a pole lever that is engaged with one of teeth formed in the bracket to keep the lever at a selected pivot angle and that is pivotally held by the lever; a release rod that is connected to the pole lever; and a switch that pushes the release rod to disengage the pole lever from the one of the teeth, characterized in that intervals between the teeth formed in the bracket are set in such a manner that an interval between part of the teeth, with which the pole lever is engaged when the lever is at a first pivot angle, is wider than an interval between another part of the teeth, with which the pole lever is engaged when the lever is at a second pivot angle that is larger than the first pivot angle.

2. The lever device according to claim 1, wherein the interval between the teeth formed in the bracket is set in such a manner that an interval between part of the teeth, with which the pole lever is engaged when the brake is applied to the wheel, is narrower than an interval between another part of the teeth, with which the pole lever is engaged when the brake is not applied to the wheel.

3. The lever device according to claim 2, wherein the interval between the teeth formed in the bracket becomes narrower as the pivot angle of the lever is larger.

4. The lever device according to claim 2, wherein part of the teeth, with which the pole lever is engaged when the brake is not applied to the wheel, are omitted.

5. A parking brake apparatus characterized by comprising: the lever device according to any one of claims 1 to 4; an equalizer that is connected to the wire; and drum brakes that are connected to the equalizer via a pair of cables, and that apply brakes to a right wheel and a left wheel with use of tension of the wire.