Damper device

Abstract

The present invention provides a damper device that can quickly dampen vibrations transmitted from unsprung mass to sprung mass. [Solution] The damper device 1 comprises a ball screw 2 having a screw shaft 3 and a ball screw nut 4, a rotating body 8 fixed to the ball screw nut 4, a case 5 in which the ball screw nut 4 and the rotating body 8 are rotatably housed, a viscous fluid 9 filled in the case 5 to resist the rotation of the rotating body 8, and an inertial mass 11 connected to the ball screw nut 4 via an elastic member 12. When the case 5 reciprocates relative to the screw shaft 3 in the axial direction, the ball screw nut 4, the rotating body 8, and the inertial mass 11 rotate.

Description

Technical Field

[0001] The present invention relates to a damper device provided in a suspension device of a vehicle such as an automobile.

Background Art

[0002] A suspension device supports the sprung mass such as a vehicle body with respect to the unsprung mass such as a tire of the vehicle, and reduces the transmission of vibrations of the unsprung mass (input vibrations from the ground) to the sprung mass. A damper device that generates a damping force is provided in the suspension device.

[0003] As a general damper device, a direct-acting damper device is known in which a piston is provided in a cylinder so as to be reciprocable in the axial direction, an orifice is provided in the piston, and the cylinder is filled with a viscous fluid. In such a damper device, when the piston reciprocates in the axial direction in the viscous fluid, the viscous fluid flows through the orifice, and a damping force corresponding to the speed of the piston is generated.

[0004] Also known is a damper device that fills a cylinder with a viscous fluid such as a magnetorheological fluid and variably controls the damping force by controlling the viscosity of the viscous fluid (see Patent Document 1). In this damper device, a coil is provided near the orifice of the piston, and the viscosity of the viscous fluid passing through the orifice is controlled by controlling the magnetic field of the coil.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, conventional damper devices have a configuration in which the piston reciprocates in the axial direction, making it difficult to install a rotating inertial mass. This presents a challenge in that vibrations transmitted from the unsprung mass to the sprung mass cannot be dampened quickly.

[0007] This invention has been made in view of the above problems, and aims to provide a damper device that can dampen vibrations transmitted from the unsprung mass to the sprung mass at an early stage. [Means for solving the problem]

[0008] To solve the above problems, one aspect of the present invention is a damper device comprising: a ball screw having a screw shaft and a ball screw nut; a rotating body fixed to the ball screw nut; a case rotatably housing the ball screw nut and the rotating body; a viscous fluid filled in the case to resist the rotation of the rotating body; and an inertial mass connected to the ball screw nut via an elastic member, wherein when the case reciprocates relative to the screw shaft in the axial direction, the ball screw nut, the rotating body, and the inertial mass rotate. [Effects of the Invention]

[0009] According to one aspect of the present invention, an inertial mass is connected to the ball screw nut via an elastic member, so that the reaction force due to the inertial force of the inertial mass acts on the screw shaft in such a way that it cancels out the input vibration with a time delay. For this reason, in a damper device in which the damping force of a viscous fluid is generated with a time delay in response to the input vibration, vibrations transmitted from the unsprung mass to the sprung mass can be dampened earlier. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view of the damper device according to this embodiment. [Figure 2] This is a longitudinal cross-sectional view of the damper device according to this embodiment. [Figure 3]Figure 3(a) is a perspective view showing an example of an inertial mass, and Figure 3(b) is an exploded perspective view of the inertial mass, rubber, and flange for the inertial mass. [Figure 4] Figure 4(a) is a perspective view showing another example of an inertial mass, and Figure 4(b) is an exploded perspective view of the inertial mass, rubber, and fixing part. [Figure 5] This is a graph showing the hysteresis curve of rubber. [Figure 6] This graph shows the simulation results of vibrations of a sprung mass without an inertial mass and vibrations of a sprung mass with an inertial mass. [Modes for carrying out the invention]

[0011] Hereinafter, a damper device according to an embodiment of the present invention will be described in detail with reference to the attached drawings. However, the damper device of the present invention can be embodied in various forms and is not limited to the embodiments described in this specification. This embodiment is provided with the intention that those skilled in the art will be able to fully understand the invention by making full disclosures in this specification.

[0012] As shown in Figure 1, the damper device 1 according to this embodiment comprises a ball screw shaft 3 and a case 5. The screw shaft 3 is connected to, for example, the vehicle body (sprung mass), and the case 5 is connected to, for example, the suspension arm (unsprung mass). The damper device 1 according to this embodiment is installed in the suspension system of a vehicle and performs a damper function against vibrations of the unsprung mass, such as the vehicle's tires (input vibrations from the ground), thereby reducing the transmission of vibrations of the unsprung mass to the sprung mass, such as the vehicle body.

[0013] As shown in Figure 2, the damper device 1 comprises a ball screw 2, a case 5, a rotating body 8, a viscous fluid 9, and an inertial mass 11. Each component is described in detail below.

[0014] The ball screw 2 comprises a screw shaft 3 and a ball screw nut 4. A helical ball groove 3a is formed on the outer circumferential surface of the screw shaft 3. The ball screw nut 4 is substantially cylindrical with a flange 4a. A helical ball groove (not shown) is formed on the inner circumferential surface of the ball screw nut 4, opposite to the ball groove 3a of the screw shaft 3. A number of balls (not shown) are interposed between the ball groove 3a of the screw shaft 3 and the ball groove of the ball screw nut 4 so as to be able to roll. The ball screw nut 4 is provided with a circulation member for circulating the number of balls. The configuration of the ball screw 2 is well known, so further detailed explanation is omitted.

[0015] Case 5 comprises a case body 6 and a lid member 7 fixed to the upper part of the case body 6 using fastening members such as bolts. The screw shaft 3 passes through the case 5. The ball screw nut 4 is rotatably housed in the case 5. A through hole 6a is formed in the case body 6 through which the screw shaft 3 passes.

[0016] The case body 6 has a viscous fluid filling section 6b and a coil housing section 6c. The case body 6 comprises a substantially bottomed cylindrical outer case body 6-1 and a substantially bottomed cylindrical inner case body 6-2 that is incorporated into the outer case body 6-1. The inner case body 6-2 is fixed to the bottom of the outer case body 6-1 using fastening members such as bolts. A substantially cylindrical viscous fluid filling section 6b is formed between the outer case body 6-1 and the inner case body 6-2. The coil housing section 6c is formed at the bottom of the outer case body 6-1.

[0017] A rotating body 8 is fixed to the ball screw nut 4. The rotating body 8 includes an upper flange 8a fixed to the flange 4a of the ball screw nut 4 using a fastening member such as a bolt, and a substantially cylindrical tubular portion 8b hanging down from the outer peripheral portion of the upper flange 8a. The outer surface of the tubular portion 8b faces the inner surface of the outer case body 6-1. The inner surface of the tubular portion 8b faces the outer surface of the inner case body 6-2. The viscous fluid filling portion 6b of the case 5 is filled with a viscous fluid 9. A seal 13 for enclosing the viscous fluid 9 is provided between the ball screw nut 4 and the inner case body 6-2. A seal 14 for enclosing the viscous fluid 9 is provided between the ball screw nut 4 and the lid member 7. When the rotating body 8 rotates within the viscous fluid 9, the viscous fluid 9 resists the rotation of the rotating body 8, and a damping force is generated.

[0018] The viscous fluid 9 is a magnetic fluid in which iron powder is dispersed (Magnetic Fluid) or a magneto-rheological fluid (Magneto Rheological Fluid) called MR fluid, etc.

[0019] A coil 10 held by a bobbin 17 is housed in the coil housing portion 6c of the case 5. The coil 10 constitutes an electromagnet with the case body 6 as a yoke. The coil 10 is disposed below the viscous fluid 9. When a DC voltage is applied to the coil 10, a magnetic field is generated, and a magnetic loop M is formed in the case body 6. The viscous fluid 9 is disposed on a magnetic path that is the path of the magnetic loop M.

[0020] An inertial mass body 11 is connected to the ball screw nut 4 via an elastic member 12. The inertial mass body 11 is substantially cylindrical. A through hole through which the screw shaft 3 passes is formed in the inertial mass body 11. The elastic member 12 is rubber or a spring.

[0021] Figs. 3(a) and (b) show an example of the inertial mass body 11. A circumferential groove 11a provided with rubber 12 as the elastic member 12 is formed on the outer surface of the inertial mass body 11. Reference numeral 16 is a flange for the inertial mass body fixed to the flange 4a of the ball screw nut 4 using a fastening member such as a bolt.

[0022] The rubber 12 is integrally molded with the inertial mass 11 and the flange 16 for the inertial mass. That is, the rubber 12, the inertial mass 11, and the flange 16 for the inertial mass are integrally formed by insert molding, in which rubber material is poured into the cavity with the inertial mass 11 and the flange 16 for the inertial mass placed inside the mold.

[0023] Figures 4(a) and 4(b) show another example of the inertial mass 11. In this example, the inertial mass 11 has a flange 11b. Multiple holes 11b1 are formed in the flange 11b of the inertial mass 11. Reference numeral 18 denotes a fixing part to which a fastening member such as a bolt is fixed for connecting the inertial mass 11 to the flange 4a of the ball screw nut 4. The fixing part 18 is cylindrical. Screw holes for screwing in the fastening member may be formed on the inner surface of the fixing part 18, or the fastening member may be fixed to the fixing part 18 using a fastening member and a nut (not shown). As shown in Figure 2, the inertial mass 11 and the rotating body 8 are fastened together to the flange 4a of the ball screw nut 4 using a fastening member.

[0024] The rubber 12 is annular in shape and is integrally molded with the fixing portion 18 and the flange 11b of the inertial mass body 11. That is, the rubber 12, the inertial mass body 11, and the fixing portion 18 are integrally formed by insert molding, in which the rubber material is poured into the cavity with the inertial mass body 11 and the fixing portion 18 placed inside the mold.

[0025] Both the rubber 12 shown in Figure 3 and the rubber 12 shown in Figure 4 exhibit hysteresis, as shown in Figure 5. In Figure 5, the horizontal axis represents deformation and the vertical axis represents force. When the rubber 12 is stretched and then compressed, the applied load and the deformation of the rubber form a loop. The shaded area in Figure 5 represents energy loss.

[0026] As shown in Figure 2, the inertial mass 11 is rotatably supported by a bearing 15 provided on the cover member 7. Of the ball screw nut 4, rotating body 8, and inertial mass 11, only the inertial mass 11 is rotatably supported by the bearing 15. The type of bearing 15 is not particularly limited, but a cross-roller bearing with high moment load capacity is desirable.

[0027] The damper device 1 is manufactured, for example, as follows. First, the coil 10 held on the bobbin 17 is assembled into the bottom of the outer case body 6-1, and the inner case body 6-2 is fixed to the outer case body 6-1. Next, the rotating body 8 and the inertial mass body 11 are fastened together to the flange 4a of the ball screw nut 4, and then these are assembled into the case body 6. Next, a seal 13 is placed between the inner case body 6-2 and the ball screw nut 4, viscous fluid 9 is filled into the viscous fluid filling section 6b, and a seal 14 is placed between the lid member 7 and the ball screw nut 4. After that, the lid member 7 is fixed to the case body 6 using fastening members such as bolts.

[0028] The operation and effects of the damper device 1 of this embodiment are described below. When vibrations from the ground (input vibrations) are input to the unsprung mass such as a tire, the case 5 moves axially relative to the screw shaft 3, and the ball screw nut 4 rotates. When the ball screw nut 4 rotates, the rotating body 8 and the inertial mass body 11 rotate together with the ball screw nut 4.

[0029] As the rotating body 8 rotates within the viscous fluid 9, a damping force is generated by the viscous fluid 9 that resists the rotation of the rotating body 8, as described above. This dampens vibrations transmitted from the unsprung mass, such as the tires, to the sprung mass, such as the vehicle body.

[0030] The damping force due to the viscous fluid 9 can be adjusted by controlling the DC voltage applied to the coil 10. When a DC voltage is applied to the coil 10, a magnetic loop M is generated, and chain-like clusters of iron powder, etc., are formed in the viscous fluid 9 between the case 5 and the rotating body 8. When the rotating body 8 rotates, a damping force is generated due to the resistance of these clusters. By controlling the DC voltage applied to the coil 10, the strength of the clusters can be adjusted, and thus the damping force can be adjusted.

[0031] An inertial mass 11 is connected to the ball screw nut 4 via an elastic member 12. When the ball screw nut 4 rotates, the inertial mass 11 rotates with a time delay relative to the ball screw nut 4. This is because, if the elastic member 12 is the rubber 12 shown in the figure, the rubber 12 twists, and if the elastic member 12 is the rubber 12 shown in the figure, the rubber 12 compresses and deforms. As a result, the reaction force due to the inertial force of the inertial mass 11 acts on the screw shaft 3 in such a way that it cancels out the input vibration with a time delay relative to the input vibration. Therefore, in a damper device 1 in which the damping force due to the viscous fluid 9 is generated with a time delay relative to the input vibration, vibrations transmitted from the unsprung mass to the sprung mass can be damped earlier.

[0032] In the case of a variable damping damper device 1 that changes the viscosity of the viscous fluid 9 using a coil 10, the actual damping force is generated with a time delay relative to the target damping force. The method of damping by applying the inertial force of an inertial mass 11 to the screw shaft 3 with a time delay is effective for the variable damping damper device 1.

[0033] Since the elastic member 12 is rubber 12 with hysteresis, the rubber 12 can absorb input vibrations.

[0034] Since only the inertial mass 11 is rotatably supported by the bearing 15, the ball screw nut 4 can be placed at the back of the case 5, and the damper device 1 can be miniaturized.

[0035] Since the rubber 12 is integrally molded with the inertial mass flange 16 and inertial mass 11 that are fixed to the ball screw nut 4, twisting can be generated in the rubber 12.

[0036] Since the rubber 12 is integrally molded with the fixing portion 18, to which a fastening member for connecting the inertial mass 11 to the ball screw nut 4 is fixed, and the flange 11b of the inertial mass 11, the rubber 12 can be compressed and deformed. [Examples]

[0037] Figure 6 shows the simulation results of the vibration of the sprung mass. The dashed line shows the vibration of the sprung mass without the inertial mass 11. The solid line shows the vibration of the sprung mass with the inertial mass present. The viscosity of the viscous fluid is assumed to be constant. It can be seen that the amplitude decreases and the vibration converges earlier when the inertial mass is placed in place. [Explanation of Symbols]

[0038] 1…Damper device, 2…Ball screw, 3…Screw shaft, 4…Ball screw nut, 5…Case, 8…Rotating body, 9…Viscous fluid, 10…Coil, 11…Inertial mass, 11b…Flange for inertial mass, 12…Rubber (elastic member), 15…Bearing, 16…Flange for inertial mass, 18…Fixed part

Claims

1. A ball screw having a screw shaft and a ball screw nut, A rotating body fixed to the aforementioned ball screw nut, The ball screw nut and the rotating body are rotatably housed in a case, A viscous fluid that is filled into the case and resists the rotation of the rotating body, The ball screw nut is connected to an inertial mass body via an elastic member, and the system comprises A damper device in which the ball screw nut, the rotating body, and the inertial mass rotate when the case reciprocates relative to the screw shaft in the axial direction.

2. The damper device according to claim 1, characterized by providing a coil that generates a magnetic field to change the viscosity of the viscous fluid.

3. The damper device according to claim 1 or 2, characterized in that the elastic member is made of rubber.

4. The damper device according to claim 1 or 2, characterized in that, of the ball screw nut, the rotating body, and the inertial mass body, only the inertial mass body is rotatably supported by the bearing.

5. The damper device according to claim 3, characterized in that the rubber is integrally molded with the flange for the inertial mass body, which is fixed to the ball screw nut, and the inertial mass body.

6. The damper device according to claim 3, characterized in that the rubber is integrally molded with the flange of the inertial mass and with a fixing portion to which a fastening member for connecting the inertial mass to the ball screw nut is fixed.

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