JPH07112768B2 - Vehicle damping force detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vehicle damping force detector effective for detecting a damping force acting on a shock absorber of a vehicle.

[Prior Art] Conventionally, a detector that applies a piezoelectric element to detect vibration, strain, and the like has been known. Such a detector needs to be attached to a portion to be detected so that stable detection sensitivity can be obtained. As such a technique, for example, a "vibration detector" (Japanese Utility Model Publication No. 57-45539) is proposed.
That is, the diameter of the mounting seat surface that abuts the mounting plate of the bottomed cylindrical metal case containing the pressurized piezoelectric element is set equal to or smaller than the diameter of the piezoelectric element, and the sensitivity change due to the change of the mounting torque, so-called , The change in base distortion sensitivity is small and stable.

[Problems to be Solved by the Invention] In consideration of mountability, it is more advantageous to directly incorporate a detector into a detection target portion than to attach the detector to the detection target. However, the conventional technique has a problem that the accuracy of the detector incorporated directly is low. This is because the piezo actuator, which is also directly incorporated in the detection target portion and which changes the damping force of the shock absorber, directly applies pressure fluctuations to the detector when it is driven. Also, if the initial applied load to the piezoelectric element decreases over time,
There is also a problem that the reliability of damping force detection decreases.

It is an object of the present invention to provide a vehicle damping force detector having excellent detection accuracy and high reliability.

[Means for Solving the Problems] The present invention, which has been made to achieve the above object, provides a shock absorber including a cylinder and a piston slidably fitted to the cylinder, and a piston rod connected to the piston. A damping force detector for a vehicle, which is press-fixed internally and at a position where pressure fluctuation during driving of a piezo actuator for changing the damping force of the shock absorber is not received, by a pressure member screwed with the piston rod. There is a piezoelectric element that generates an electric charge according to the strain of the piston rod, an electrode member that is disposed so as to face the piezoelectric element, and that is interposed between the electrode member and the pressure member, It is characterized by further comprising: a transmission member that transmits a pressing force of the pressure member, and a fixing unit that fixes the screwed portion of the pressure member and the piston rod so as not to rotate at a predetermined position. A vehicular damping force detector to it is an gist.

[Operation] Since the vehicle damping force detector is fixed at a position where pressure fluctuation during driving of the piezo actuator that changes the damping force of the shock absorber is not affected, the damping force detection signal always indicates the piezo actuator. The driving effect does not appear.

The screwing portion of the pressure member and the piston rod, which applies the pressing force to the piezoelectric element via the transmission member, is fixed to the predetermined position in a non-rotatable manner by the fixing means. This prevents loosening due to changes over time and the initial applied load does not decrease.

[Embodiment] Next, a preferred embodiment of the present invention will be described in detail with reference to the drawings. FIG. 3 shows a vertical sectional view of a damping force type shock absorber incorporating a piezo type damping force sensor according to the first embodiment of the present invention.

As shown in the figure, the damping force type shock absorber 1
The piston 3 is fitted inside the cylinder 2 slidably in the axial direction (indicated by arrows A and B in the figure). The piston 3 is connected to one end of a piston rod 4, while the other end of the piston rod 4 is fixed to a shaft 5. The cylinder 2 is housed in an outer shell (outer cylinder) 2a, and the lower part of the outer shell 2a is connected to a vehicle lower arm 2c via a suspension bush 2b, while
The upper portion of the shaft 5 is connected to the vehicle body 8 via a bearing 6 and a vibration-proof rubber 7.

A piezo actuator 11 for changing the damping force of the variable damping force type shock absorber 1 and a piezo type damping force sensor 12 for detecting the acting damping force are built in a hollow portion bored in the axial direction of the piston rod 4. . The piezo-type damping force sensor 12 is pressed and fixed to the hollow portion of the piston rod 4 with a screw 13.

Next, the piezoelectric type damping force sensor 12 that characterizes the present invention
The structure will be described with reference to FIGS. 1 and 2. As shown in FIG. 1 and FIG. 2, the piezo time damping force sensor 1 is made of piezoelectric ceramics such as PZT, and presses two piezoelectric elements 21 and 22 having a disk shape and a through hole in the central portion. The surfaces on which positive charges are generated face each other. A positive electrode plate 23 made of a conductive metal such as copper and having a through hole at the center is interposed between the positive charge generating surfaces of the piezoelectric elements 21 and 22. Between the piezoelectric element 21 and the screw 13, there is arranged a retainer 24 having a through hole in the central portion and having a lower surface forming a convex spherical surface having substantially the same curvature as the concave spherical surface of the upper surface of the screw 13. The upper surface of the retainer 24 in contact with the piezoelectric element 21 is polished (10-point average roughness is about 3.2Z).

On the other hand, on both sides of the piezoelectric element 22 facing the piezoelectric element 21 where negative charges are generated, a negative electrode plate 25 made of a conductive metal such as copper and having a through hole at the center is provided. Furthermore, piston rod 4
Between the negative electrode plate 25 and the negative electrode plate 25, a plate 26 made of an insulating material such as insulating resin or ceramics and having a disk shape and having a through hole in the center is disposed. The surface of the plate 26 in contact with the negative electrode plate 25 is polished (10-point average roughness of about 3.2Z) to prevent concentrated stress from acting on a part of the piezoelectric element 22.

As shown in FIG. 1, these piezoelectric elements 21, 22, the positive electrode plate 23, the retainer 24, the negative electrode plate 25, and the plate 26 are surrounded by a cylindrical spacer 27 made of an insulating resin. Therefore, the lateral displacement of each member is prevented. The inner peripheral surface of the spacer 27, the piezoelectric elements 21 and 22, the retainer 2
4. A highly viscous and highly insulating grease is applied to the outer peripheral side surface of the plate 26. In addition, these piezoelectric elements 21 and 2
2, positive electrode plate 23, retainer 24, negative electrode plate 25, plate 26
The lead wire 28 is held by a clamp 29 and integrated. Each one end of the pair of lead wires 28 is connected to the positive electrode plate 23 and the negative electrode plate 25, respectively, and the other end is connected to an electronic control unit (not shown), and the negative electrode plate 25 is a plate.
It is connected to the piston rod 4 via 26, that is, is body-grounded.

Next, the operation of the piezoelectric type damping force sensor 1 will be described.
When the vehicle gets over the uneven portion of the road surface, a compressive force acts on the piston rod 4. As shown in FIG. 1, a part of this compressive force passes through the contact surface between the screw 13 and the retainer 24,
It acts on the piezoelectric type damping force sensor 1. This acting force is transmitted from the retainer 24 to the piezoelectric elements 21 and 22. Electric charges corresponding to the transmitted acting force are generated in the piezoelectric elements 21 and 22, and are stored in the charge amplifier circuit of the electronic control unit (not shown) from the positive electrode plate 23 and the negative electrode plate 25 via the lead wire 28. It Therefore, the damping force acting on the piston rod 4 can be detected. Even if the piston rod 4 is not distorted by the compressive force, the piezoelectric elements 21, 22
A predetermined initial applied load is applied to the screw by tightening the screw 13. This initial applied load is for obtaining a stable detection signal when the piston rod 4 is distorted due to axial tension or compression, which strain is changed from the strain due to the initial applied load.

In the first embodiment, the piezoelectric type damping force sensor
12 is a vehicle damping force detector, piezoelectric elements 21 and 22 are piezoelectric elements, positive electrode plate 23 and negative electrode plate 25 are electrode members, retainer 24 is a transmission member, spacer 27 and clamp 29 is a gripping member. , Respectively.

As described above, according to the first embodiment, since the assembly accuracy of the piezoelectric type damping force sensor 12 is high and the displacement of the components is prevented by the spacer 27 and the clamp 29,
Since the strain generated in the piston rod 4 can be accurately measured, the detection accuracy of the damping force acting on the variable damping force type shock absorber 1 can be improved.

Further, since the piezo-type damping force sensor 12 is integrated by the clamp 29, handling at the time of assembly work becomes easy.

Furthermore, since the pressing force from the screw 13 is applied to the piezoelectric elements 21 and 22 via the retainer 24 by spherical contact, the load does not hit the piezoelectric elements 21 and 22 one-sided, so the piezoelectric elements 21 and 22
Can be prevented from being damaged.

Further, since the spacers 27 electrically block the piezoelectric elements 21, 22, the positive electrode plate 23, the negative electrode plate 25, and the piston rod 4, sufficient insulation can be secured.

Further, since the piezoelectric elements 21 and 22 are pressed and fixed to the piston rod 4 via the plate 26, even if the surface accuracy of the contact surface of the piston rod 4 is low, the piezoelectric elements 21 and 22 are not affected by the characteristic parts of the contact surface of the piezoelectric elements 21 and 22. It is possible to prevent concentrated stress from acting.

Further, since the plate 26 and the retainer 24 have high surface accuracy of the contact surfaces on the piezoelectric elements 21 and 22 side, it is possible to prevent the load acting on the piezoelectric elements 21 and 22 via the piston rod 4 from being offset.

Further, in the first embodiment, the negative electrode is body-grounded, but it is not body-grounded to avoid noise. For example, a polycarbonate plate or an inert ceramic plate made of PZT (dummy element) is used. ) The negative electrode plate 25
Also, it may be configured to interpose and insulate on each outer surface of a new negative electrode plate described later. However, in this case, it is necessary to insert a new negative electrode plate between the piezoelectric element 21 and the retainer 24 to connect the negative lead wire.

Further, the shape of the retainer 24 may be any shape as long as it has a concave spherical upper surface and a convex lower surface that can be in spherical contact with the screw 13. Therefore, for example, the retainer 24a shown in FIG.
It can also be shaped like.

Further, the shape of the screw may be any shape as long as it has a lower surface that forms the convex spherical surface of the retainer and an upper surface that forms the concave spherical surface that can make spherical contact. Therefore, for example, the shape of the screw 13a shown in FIG. good.

Further, in the first embodiment, two piezoelectric elements are used. However, for example, a larger number of piezoelectric elements and electrode plates may be alternately laminated.

Next, a second embodiment of the present invention will be described in detail with reference to the drawings. The difference between the second embodiment and the first embodiment is that a screw loosening prevention measure is taken. The piezo-type damping force sensor 40 has two piezoelectric elements 4 as shown in FIG.
1, 42, positive electrode plate 43 interposed between the positive charge generation surfaces of both piezoelectric elements 41, 42, retainer 44 interposed between piezoelectric element 41 and screw 33, negative charge generation of piezoelectric element 42 It is composed of a negative electrode plate 45 arranged on the surface side and a plate 46 interposed between the piston rod 34 and the negative electrode plate 45. The contact surface between the retainer 44 and the piezoelectric element 41, the plate 46 and the negative electrode plate
The contact surface with 25 was polished together (10-point average roughness 3.2Z
The degree). These, piezoelectric elements 41, 42, positive electrode plate 43,
A spacer 47 is provided around the retainer 44, the negative electrode plate 45, and the plate 46, and each member and the lead wire 48 are grasped by a clamp 49 and integrated.

Here, in the screw portion 33a with which the screw 33 of the piston rod 34 is screwed, the through hole 50 is formed from its side portion toward the hollow portion.
Has been drilled. When assembling the piezo-type damping force sensor 40, a predetermined initial applied load is applied by tightening the screw 44 on the piezoelectric elements 41, 42, and then a punch is driven through the through hole 50 to impact the screw portion 33a, and the screw thread And a screw squeezing portion 51 is provided. This allows the screw 33
Is fixed and can be prevented from loosening. Therefore, even when affected by vibration or the like caused by running of the vehicle, the predetermined initial applied load applied to the piezoelectric elements 41, 42 by tightening the screw 44 can be maintained during assembly.

In the second embodiment, a piezoelectric type damping force sensor
40 is a vehicle damping force detector, piezoelectric elements 41 and 42 are piezoelectric elements, positive electrode plate 43 and negative electrode plate 45 are electrode members, retainer 44 is a transmission member, spacer 48 and clamp 49 is a gripping member. , The screw crushing portion 51 corresponds to the fixing portion, respectively.

As described above, according to the second embodiment, the following effects are obtained in addition to the effects of the first embodiment. That is, since the screw 33 is used to fix the rotation of the screw 33, it is possible to prevent the initial applied load by the screw 33 from decreasing with time, so that a stable electric charge is always obtained from the piezoelectric elements 41 and 42 and the damping force is reduced. It is possible to further improve the reliability of the detection over time and deterioration.

Further, high reliability can be obtained by simple processing such as crushing the screw portion 33a of the screw 33 through the through hole 50.

Alternatively, the piston rod 34 may be processed to expose the screw portion 33a of the screw 33, and the exposed screw portion 33a may be crushed.

Further, as the screw 33, a screw coated with a locking agent may be used.

Furthermore, the screw 33a of the screw 33 may be provided with a loosening preventive adhesive, a resin or the like through the through hole 50 and then cured to prevent the screw 33 from loosening.

[Effects of the Invention] As described in detail above, the vehicle damping force detector of the present invention is
The pressure when the piezo actuator is driven is fixed because it is pressed and fixed by a pressure member that is screwed with the piston rod at a position that does not change the pressure when driving the piezo actuator that changes the damping force of the shock absorber. Detection is always accurate without being transmitted to the detector.

Further, since the screwing portion between the pressurizing member and the piston rod is fixed by the fixing means, the reduction of the initial applied load can be suppressed without loosening the screwing portion.

Therefore, the accurate damping force can always be detected,
The reliability of damping force detection can be improved.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a piezo type damping force sensor according to a first embodiment of the present invention, FIG. 2 is an exploded view showing the same structure, and FIG. 3 is a damping force variable in which the piezo type damping force sensor is also incorporated. 4 is a longitudinal sectional view showing the structure of a shock absorber of the type, FIG. 4 and FIG. 5 are partial explanatory views showing the structure of the main part of another piezoelectric type damping force sensor, and FIG. 6 is a piezoelectric device according to a second embodiment of the present invention. It is a longitudinal cross-sectional view of a type damping force sensor. 1 …… Shock absorber with variable damping force, 4 …… Piston rod, 12 …… Piezo type damping force sensor, 21,22 …… Piezoelectric element, 23 …… Positive electrode plate, 24 …… Retainer, 25 …… Negative electrode Plate, 26 …… plate, 27 …… spacer, 29 …… clamp, 51
...... Screw crushing part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shino Oda 1-1, Showa-cho, Kariya city, Aichi Prefecture Nihon Denso Co., Ltd. (72) Inventor Masayuki Yano 1-1-chome, Showa town, Kariya city, Aichi prefecture Co., Ltd. (56) Reference JP 63-6238 (JP, A) JP 1-55445 (JP, A) JP 61-85210 (JP, A) JP 62-29410 (JP , A)

Claims (1)

[Claims] 1. A drive of a piezo actuator for changing the damping force of the shock absorber inside a piston rod connected to the piston of a shock absorber comprising a cylinder and a piston slidably fitted to the cylinder. A vehicle damping force detector that is pressed and fixed by a pressure member that is screwed with the piston rod at a position that is not subject to pressure fluctuations, and a piezoelectric element that generates an electric charge according to the strain of the piston rod. An electrode member arranged to face the piezoelectric element; a transmission member interposed between the electrode member and the pressing member for transmitting a pressing force by the pressing member; A damping force detector for a vehicle, comprising: a fixing unit that fixes a screwed portion of the piston rod and the piston rod at a predetermined position so as not to rotate.