Actuator for Hood Lifting Device

Abstract

To provide an actuator for a hood lifting device capable of adjusting push-back force of a ball, etc., used to prevent a piston rod from retreating.SOLUTION: An actuator 1 for a hood lifting device moves a piston rod 3 arranged in a cylinder 2 by gas pressure to lift a hood of a vehicle. In the actuator 1, a ball 15 for preventing the piston rod from retreating is arranged between a tapered surface 13 provided on the base end side of the piston rod 3 and the inner peripheral surface of the cylinder 2. The tapered surface 13 has a shape that expands in diameter in a direction in which the piston rod protrudes. On the tip side of the tapered surface 13 in the direction in which the piston rod protrudes, recess parts 30, 30A recessed toward the axial center side of the piston rod 3 are provided.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an actuator for a hood lifting device for lifting the hood (bonnet hood) of an automobile when a collision with a pedestrian or the like is detected or predicted.

Background Art

[0002] As an actuator used in an automobile hood lifting device, there is one including a gas generator, a cylinder, and a piston rod. In this actuator, when the gas generator operates, the piston rod protrudes from the cylinder to lift the hood.

[0003] In order to prevent the protruding piston rod from retracting, a tapered surface is provided on the circumferential surface of the piston rod, and a ball is disposed between the tapered surface and the inner circumferential surface of the cylinder. When the piston rod attempts to retract, the ball is engaged between the tapered surface and the inner circumferential surface of the cylinder, generating a pushing-back resistance force to prevent the piston rod from retracting.

[0004] Conventionally, this tapered surface is circular in a cross-section perpendicular to the axial center line of the piston rod. A large number of balls are arranged so as to surround this circular tapered surface in cross-section.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide an actuator for a hood lifting device capable of adjusting the pushing-back resistance force by a ball or the like for preventing the piston rod from retracting.

Means for Solving the Problems

[0007] The actuator for a hood lifting device of the present invention is an actuator for a hood lifting device that moves a piston rod disposed in a cylinder by gas pressure to lift the hood of a vehicle. An intervening body for preventing the piston rod from retracting is disposed between a tapered surface provided on the proximal end side of the piston rod and the inner peripheral surface of the cylinder. The tapered surface has a shape that expands in diameter toward the piston rod protruding direction, and a recess that is recessed toward the axial center side of the piston rod is provided on the tip side in the piston rod protruding direction from the tapered surface.

[0008] In one aspect of the present invention, the recess is a groove provided around the outer peripheral surface of the piston rod.

[0009] In one aspect of the present invention, a connecting portion between the tapered surface and the bottom surface of the groove is a plane perpendicular to the axial center line of the piston rod.

[0010] In one aspect of the present invention, a connecting portion between the tapered surface and the bottom surface of the groove has a shape that contracts in diameter toward the piston rod protruding direction.

[0011] In one aspect of the present invention, a groove extending in the longitudinal direction of the piston rod is provided on the outer peripheral surface on the proximal end side of the piston rod. The bottom surface of the groove is the tapered surface, and the recess is provided in the groove.

[0012] In one aspect of the present invention, a plurality of the grooves are provided at intervals in the circumferential direction of the piston rod, and the recess is provided in some of the plurality of grooves.

[0013] In one aspect of the present invention, six of the grooves are provided at six equal circumferential positions of the piston rod, and the recess is provided in three of the grooves at every other one.

[0014] In one aspect of the present invention, a plurality of grooves are provided at intervals in the circumferential direction of the piston rod, and the concave portions are provided in all of the plurality of grooves.

Advantages of the Invention

[0015] According to the present invention, it is possible to adjust the pushing-back resistance force by a ball or the like for preventing the piston rod from retreating.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Modes for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0018] FIG. 1 shows an actuator 1 for a hood lifting device according to an embodiment. This hood lifting device is for lifting the hood to mitigate the impact on a pedestrian when a vehicle collides with the pedestrian.

[0019] In the following description, the end in the protruding direction of the piston rod is referred to as the upper end or the tip, and the end in the direction opposite to the protruding direction is referred to as the lower end or the rear end.

[0020] This actuator 1 is a linear actuator having a cylinder 2 and a piston rod 3. A gas generator 4 is provided at the rear end of the cylinder 2. The gas generator 4 is connected to an ECU (electronic control unit) (not shown), operates based on the command of the ECU, and generates high-pressure gas. This high-pressure gas pushes up the piston rod 3 and causes it to protrude from the cylinder 2.

[0021] On the tip side of the cylinder 2, a flange-shaped end member 5 having a hole in the center is fixedly installed. The inner peripheral edge side of the end member 5 protrudes more centrally than the inner peripheral edge of the cylinder 2.

[0022] The tip side of the piston rod 3 protrudes upward through the central hole of the end member 5. A groove is provided around the inner peripheral surface of the end member 5, and a claw piece (not shown) on the outer peripheral edge of the stopper ring 6 is engaged with this groove.

[0023] Although not shown, claw pieces project radially from the outer peripheral edge of the stopper ring 6. A plurality of claw pieces are provided at intervals in the circumferential direction of the stopper ring 6. These claw pieces are engaged with the above-mentioned groove.

[0024] The stopper ring 6 prevents the piston rod 3 from protruding upward during normal operation (when the gas generator is not operating). A cover cap 7 is attached to the tip of the piston rod 3.

[0025] As clearly shown in FIG. 2, the rear end portion of the piston rod 3 is a piston portion 8. A groove 9 is provided around the outer peripheral surface of the piston portion 8. An O-ring 10 is disposed in the groove 9 and is in airtight and slidable contact with the inner peripheral surface of the cylinder 2.

[0026] The upper side of the piston part 8 is a small-diameter part 11, and a large-diameter part 12 is provided above the small-diameter part 11. The diameter of the large-diameter part 12 is slightly smaller than the inner diameter of the cylinder 2.

[0027] The piston part 8 side of the small-diameter part 11 is in a substantially inverted truncated cone shape, and its side peripheral surface is a tapered surface 13 where the distance from the inner peripheral surface of the cylinder 2 becomes smaller upward. The distance between the lower end part of the small-diameter part 11 and the inner peripheral surface of the cylinder 2 is slightly larger than the diameter of the ball 15. The distance between the upper end part of the tapered surface 13 and the inner peripheral surface of the cylinder 2 is smaller than the diameter of the ball 15.

[0028] A ball 15 is arranged between the tapered surface 13 and the inner peripheral surface of the cylinder 2. A ball retaining ring (not shown) is arranged so as to surround the small-diameter part 11 on the lower side of the ball. The ball retaining ring is arranged in contact with the stepped surface on the small-diameter part 11 side of the piston part 8. In the state before the actuator 1 operates, the ball 15 is in a state of being slidably in contact with the inner peripheral surface of the cylinder 2 or having a slight gap therebetween. A plurality of (for example, nine) balls 15 are arranged so as to surround the tapered surface 13.

[0029] A groove 30 is provided around the outer peripheral surface of the piston rod between the large-diameter part 12 side of the small-diameter part 11, that is, between the tapered surface 13 and the large-diameter part 12. The bottom surface 31 of the groove 30 is recessed toward the axial center side of the piston rod 3 from the upper end part of the tapered surface 13. The groove 30 is sized to accommodate at least a part of the ball 15. The groove bottom surface 31 is a cylindrical surface with an equal diameter.

[0030] The connecting part 32 connecting the groove bottom surface 31 and the tapered surface 13 is a plane extending in the radial direction (perpendicular to the axial center line of the piston rod 3).

[0031] Next, the operation of this actuator 1 will be described. When a collision between the vehicle and a pedestrian is detected or predicted by the detection system, the gas generator 4 operates based on the command of the ECU to generate high-pressure gas. The high-pressure gas is supplied into the cylinder 2 to move the piston rod 3 upward.

[0032] The piston rod 3 deforms the claw pieces (not shown) of the stopper 6 to project upward and push up the rear part of the bonnet hood. The piston rod 3 moves upward until the large-diameter portion 12 hits the end member 5.

[0033] While the piston rod 3 moves upward, the ball 15 abuts against the ball retaining ring and does not (substantially or at all) restrict the movement of the piston rod 3.

[0034] When a load is applied to the pushed-up bonnet hood by a pedestrian or the like and the rear part of the bonnet hood and the piston rod 3 attempt to move downward, the ball 15 moves upward relative to the piston rod 3 and gets caught between the inner peripheral surface of the cylinder 2 and the tapered surface 13. Due to the downward load F applied to the piston rod 3, the ball 15 receives a radial component force from the tapered surface 13 and is pressed against the inner peripheral surface of the cylinder 2, and is sandwiched between the inner peripheral surface of the cylinder 2 and the tapered surface 13.

[0035] As shown in FIG. 4, as the piston rod 3 moves downward, the ball 15 sandwiched between the inner peripheral surface of the cylinder 2 and the tapered surface 13 moves upward relative to the piston rod 3 and generates a pushing-back resistance force.

[0036] When the ball 15 that moves upward relative to the piston rod 3 exceeds the upper end of the tapered surface 13, it moves into the groove 30. When the ball 15 moves into the groove 30, the pushing-back resistance force decreases.

[0037] For example, when the distance between the groove bottom surface 31 and the inner peripheral surface of the cylinder 2 is equal to or greater than the diameter of the ball 15 and the vertical width of the groove 30 is equal to or greater than the diameter of the ball 15, the pushing-back resistance force by the ball 15 changes as shown in FIG. 5A. That is, while the ball 15 moves upward on the tapered surface 13, the pushing-back resistance force gradually increases, and when it moves into the groove 30 beyond the upper end of the tapered surface 13, the pushing-back resistance force becomes 0 (substantially 0).

[0038] On the other hand, when the distance between the groove bottom surface 31 and the inner peripheral surface of the cylinder 2 is less than the diameter of the ball 15, or when the vertical width of the groove 30 is less than the diameter of the ball 15, the pushing-back resistance force by the ball 15 changes as shown in Fig. 5B. That is, while the ball 15 moves upward on the tapered surface 13, the pushing-back resistance force gradually increases, and when it moves into the groove 30 beyond the upper end of the tapered surface 13, the pushing-back resistance force decreases by a certain amount.

[0039] After the ball 15 moves into the groove 30, the ball 15 moves downward integrally with the piston rod 3.

[0040] In this embodiment, the pushing-back resistance force can be adjusted according to the size of the groove 30.

[0041] As shown in Fig. 6, a cylindrical surface 16 with an equal diameter in the vertical direction may be provided between the concave portion 30 and the tapered surface 13.

[0042] As shown in Fig. 7, the connecting portion 32 connecting the groove bottom surface 31 and the tapered surface 13 may be a tapered surface inclined such that the distance from the inner peripheral surface of the cylinder 2 increases upward. Thereby, the pushing-back resistance force can be gradually decreased.

[0043] As shown in Fig. 8, the connecting portion 32 connecting the groove bottom surface 31 and the tapered surface 13 may be stepped. Thereby, the pushing-back resistance force can be decreased step by step.

[0044] In the above embodiment, an example in which a plurality of balls 15 are arranged between the tapered surface 13 and the inner peripheral surface of the cylinder 2 has been described, but other intervening bodies such as a ring may be used.

[0045] FIG. 9 is a perspective view of a piston rod according to another embodiment. In this embodiment, a groove 20 extending in the vertical direction is provided in the large-diameter portion 12. The lower end of the groove 20 is open toward the small-diameter portion 11. In this embodiment, six grooves 20 are provided at six equally spaced positions in the circumferential direction, but the number of grooves 20 is not limited to this. The groove 20 can be formed, for example, by cutting, but the method of forming the groove is arbitrary and is not limited to this.

[0046] The outer peripheral surface of the large-diameter portion 12 is a cylindrical surface having the same diameter in the vertical direction except for the groove 20. The bottom surface on the lower end side of the groove 20 is an arc surface concentric with the axis of the piston rod 3. Further, the bottom surface on the lower end side of the groove 20 is a tapered surface 21 that is inclined so that the distance from the inner peripheral surface of the cylinder 2 becomes smaller toward the upper side.

[0047] On the upper end side in the groove 20, a recess 30A recessed toward the axis of the piston rod 3 is provided. That is, in the groove 20, the upper end side of the tapered surface 21 is the recess 30A. The recess 30A is sized to accommodate at least a part of the ball 15.

[0048] The recess 30A may be provided in all of the plurality of grooves 20 formed in the large-diameter portion 12, or may be provided only in some of the grooves 20. In the example shown in FIG. 9, the grooves 20 are provided at six equally spaced positions in the circumferential direction, and the recess 30A is provided in three grooves 20 at every other one.

[0049] The ball 15 is disposed between the tapered surface 21 and the inner peripheral surface of the cylinder 2. After the actuator 1 operates and the piston rod 3 moves upward and then attempts to move downward, the ball 15 is sandwiched between the inner peripheral surface of the cylinder 2 and the tapered surface 21, and a pushing-back resistance force is generated.

[0050] In the groove 20 in which the recess 30A is not provided, the pushing-back resistance force increases until the ball 15 contacts the upper end surface 23 of the groove, and becomes (substantially) constant after contacting the upper end surface 23 of the groove.

[0051] On one hand, in the groove 20 provided with the recess 30A, the pushing-back resistance increases until the ball 15 reaches the recess 30A, and when the ball 15 moves into the recess 30A beyond the upper end of the tapered surface 21, the pushing-back resistance decreases.

[0052] The above embodiment is an example of the present invention, and the present invention may be in other forms than the above. For example, when using a plurality of balls as the intervening body, the sizes of some balls may be different.

Explanation of reference numerals

[0053] 1 Actuator 2 Cylinder 3 Piston rod 4 Gas generator 8 Piston part 11 Small-diameter part 12 Large-diameter part 13 Tapered surface 15 Ball 20 Groove 30 Groove 30A Recess

Claims

1. An actuator for a hood lifting device that moves a piston rod disposed in a cylinder by gas pressure to lift the hood of a vehicle, An intervening body for preventing the piston rod from retracting is disposed between a tapered surface provided on the proximal end side of the piston rod and the inner peripheral surface of the cylinder, The tapered surface has a shape that expands in diameter toward the protruding direction of the piston rod, A recess that is recessed toward the axial center side of the piston rod is provided on the distal end side in the protruding direction of the piston rod from the tapered surface, After the piston rod protrudes, as the piston rod retracts, the intervening body moves relatively toward the distal end side in the protruding direction of the piston rod with respect to the piston rod, and moves into the recess beyond the distal end in the protruding direction of the tapered surface. An actuator for a hood lifting device, characterized in that.

2. The actuator for a hood lifting device according to claim 1, wherein the recess is a groove provided circumferentially on the outer peripheral surface of the piston rod.

3. The actuator for a hood lifting device according to claim 2, wherein a connecting portion between the tapered surface and the bottom surface of the groove is a plane perpendicular to the axial center line of the piston rod.

4. The actuator for a hood lifting device according to claim 2, wherein a connecting portion between the tapered surface and the bottom surface of the groove has a shape that tapers in diameter toward the protruding direction of the piston rod.

5. A groove extending in the longitudinal direction of the piston rod is provided on the outer peripheral surface of the proximal end side of the piston rod, The bottom surface of the groove is the tapered surface, The actuator for a hood lifting device according to claim 1, wherein the recess is provided in the groove.

6. A plurality of the grooves are provided at intervals in the circumferential direction of the piston rod, The actuator for a hood lifting device according to claim 5, wherein the concave portion is provided in some of the plurality of grooves.

7. The six grooves are provided at circumferentially equally spaced positions of the piston rod. The actuator for a hood lifting device according to claim 6, wherein the concave portion is provided in every other three of the grooves.

8. A plurality of the grooves are provided at intervals in the circumferential direction of the piston rod. The actuator for a hood lifting device according to claim 5, wherein the concave portion is provided in all of the plurality of grooves.

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