JPH0225944Y2 - - Google Patents

Description

[Detailed description of the invention] (Technical field) The invention makes it possible to temporarily reduce the compression side damping force in the low and medium speed range during the compression side stroke of a hydraulic shock absorber as a rear suspension unit in a motorcycle. The present invention relates to a compression side damping force adjustment device for a hydraulic shock absorber.

(Technical background) When braking on a two-wheeled vehicle, for example when driving into a court or downhill, the rear wheel side is lifted up, and when the rear wheel is pushed up from the road surface, the cushioning effect is insufficient. This will result in poor handling stability.

Regarding this countermeasure device, there is a device proposed by the present applicant as U.S. Pat. No. 58-107336.

(Purpose of the invention) The present invention further improves this and provides a hydraulic shock absorber that responds to the compression damping force applied to the rear wheel during braking of a two-wheeled vehicle and improves handling. purpose.

(Disclosure of the invention) The present invention is a hydraulic shock absorber for suspending the rear wheel of a two-wheeled vehicle, which is provided with a relief valve that applies a compression-side damping force flowing into an oil reservoir chamber, and a relief spring that biases the relief valve in the closing direction. At the same time, a back pressure chamber is defined on the back of the relief valve,
a first orifice that communicates the back pressure chamber with the high pressure side (damper side) upstream from the pressure receiving surface of the relief valve;
A second orifice that communicates this back pressure chamber with the low pressure side (oil reservoir chamber side) downstream from the pressure receiving surface of the relief valve is provided, and a bypass passage is provided that communicates this back pressure chamber with the oil reservoir chamber. A valve is provided to increase the opening area of the bypass passage during braking.

As a result, during braking, by temporarily lowering the back pressure applied to the relief valve, the opening pressure of the relief valve is lowered and the compression side damping force is lowered, so that the rear wheels are lifted compared to the front wheels. It effectively cushions the impact on the rear wheels under such conditions.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 1, a relief valve 4 is interposed in the middle of a passage 5 through which pressure side hydraulic oil flows from an oil chamber A, which contracts when the damper 1 operates on the pressure side, to an oil reservoir chamber B.

The relief valve 4 is slidably housed in the casing 3 and opens and closes a valve port 6 formed in the casing 3.

The valve port 6 communicates with the oil chamber A of the damper 1 via a port 11 and the like.

An annular passage 7 defined between the relief valve 4 and the casing 3 includes a port 8 formed in the casing 4, an annular passage 9 defined between the casing 4 and the housing 2, and an annular passage 7 formed in the housing 2. It communicates with the oil reservoir chamber B through a port 10.

A plurality of ports 12 are formed around the port 6 of the casing 3, and a check valve 13 for opening and closing the port 12 is interposed. It opens without resistance against the pressure side hydraulic oil on the opposite side and closes against the pressure side hydraulic oil on the opposite side.

A relief spring 15 that biases the relief valve 4 in the closing direction is provided in the back pressure chamber 18. A spring receiver 16 supporting one end of the relief spring 15 is screwed into the housing 2, and the screwing position is changed by an external rotation operation via a knob 18a built in the detent mechanism 17. The initial load can be adjusted.

The relief valve 4 has a port 6 with respect to a back pressure chamber 18 defined on the back surface 14 of the relief valve 4.
A first orifice 20 that communicates with the back pressure chamber 18 is formed, and a second orifice 21 that communicates the back pressure chamber 18 with the annular oil passage 7 is formed.

As shown in FIGS. 2 and 3, the housing 2
A casing 23 is housed in the protrusion 22 of the casing 23, and a spool 25 is slidably housed in the hole 24 of the casing 23.

The hole 24 communicates with the oil reservoir chamber B via a passage 26, and communicates with the back pressure chamber 18 of the relief valve 4 via a passage 27. A bypass passage 30 communicating with the storage chamber B is configured.

The spool 25 is formed with a small diameter portion 28 extending in the axial direction, and an annular oil passage 29 is defined between the small diameter portion 28 and the inner peripheral surface of the hole 24 . Depending on the stroke position of the spool 25, this annular oil passage 29 connects the passages 26 and 27.

The spool 25 has both ends protruding from the casing 23, and an operating rod 33 is connected to one end via a pin 32.

The operating rod 33 is slidably supported via a substantially cylindrical member 34 that is threaded onto the casing 23 and a substantially cylindrical member 35 that is threaded onto this member 34 .

An annular spring receiver 36 is fixed to one end of the member 34, and a return spring 37 is interposed between the spring receiver 36 and the operating rod 33.
is biased in the direction of closing the pilot passage 30.

A substantially cylindrical holder 39 is provided at one end of the operating rod 33.
Slideably fit the holder 39 and the operation stick 3.
A spring 47 is interposed between the holder 3 and the holder 3.
9 to prevent it from falling off.

The holder 39 is connected to the brake operation via a wire (not shown) or the like, and is pulled in the direction of the arrow in FIG. 2 during braking.

Next, the operation of this device will be explained. During normal operation of the motorcycle (not braking), the spool 2
5 is held via a return spring 37 in a position that closes the pilot passage 30.

In this state, if the compression speed of the damper 1 is small, the relief valve 4 does not open, and the hydraulic oil corresponding to the intrusion volume of the piston rod 50 flows into the first orifice 20.
The oil flows into the oil reservoir chamber B through the second orifice 21, and applies a damping force that increases secondarily at the beginning of the operation of the damper 1, etc.

When the compression speed increases and the pressure difference P 1 - _{P 2} between the pressure P ₁ acting on the pressure receiving surface 19 of the relief valve 4 and the pressure P ₂ acting on the back pressure chamber ₁₈ increases to a predetermined value or more, the relief valve 4 opens while compressing the relief spring 15, and applies a damping force to the hydraulic oil flowing in from the port 6 that is primarily proportional to the flow velocity.

On the other hand, during the expansion stroke of the damper 1, the hydraulic oil flows from the oil reservoir chamber B to the oil chamber A of the damper 1 with almost no resistance after opening the check valve 13.

Next, during braking, the holder 39 is pulled in the direction of the arrow in conjunction with the brake operation, and the operating rod 33 moves the spool 25 in the direction of the arrow while compressing the return spring 37, passing through the annular oil passage 29. Connect 26 and 27. As a result, the bypass passage 30 is opened, the pressure P ₂ in the back pressure chamber 18 is reduced, and the relief valve 4 is connected to the relief spring 1.
The differential pressure P ₁ -P ₂ that urges the opening direction against the pressure 5 increases. Therefore, the opening pressure of the relief valve 4 becomes a much lower value than during normal operation, and the pressure side damping force of the damper 1 decreases.

As a result, when a motorcycle is in a state where the rear wheel side is lifted up compared to the front wheel side due to braking operation, such as when driving into a corner or downhill, the impact on the rear wheel is effectively absorbed by damper 1. This prevents the rear wheels from bouncing up and improves ground contact.

Note that when the spool 25 slides by a predetermined stroke, the shoulder 46 formed on the operating rod 33 comes into contact with the spring receiver 36, but if the holder 39 is pulled further in the direction of the arrow. In this case, only the holder 39 compresses the spring 47 and moves in the direction of the arrow, so that the brake operation is not obstructed.

As another embodiment, as shown in FIG.
a small diameter section 40 defining a passageway 26 in its closed position;
A small diameter portion 42 defining an annular oil passage 41 that communicates with the annular oil passage 41 is formed, a throttle passage (second orifice) 43 is formed that constantly communicates both annular oil passages 45 and 41, and a cutout portion 44 is formed. .

As a result, during normal operation, the hydraulic oil is transferred from the back pressure chamber 18 to the throttle passage 43 before the relief valve 4 is opened.
The oil flows into the oil reservoir chamber B through the oil reservoir chamber B, and a predetermined pressure-side damping force is applied thereto. On the other hand, during braking, the spool 25 slides to connect the passages 27 and 26 through the annular oil passage 39, thereby guiding the pressure of the oil reservoir chamber B to the back pressure chamber 18.

Note that, instead of providing the second orifice 21 in the valve 4, a passage that bypasses the spool 25 and short-circuits the back pressure chamber 18 and the oil reservoir chamber B is provided in the housing 2, and the second orifice 21 is formed in the middle of the passage. Also good.

Further, instead of providing the first orifice 20 in the valve 4, a passage is provided in the housing 2 that communicates the passage on the damper 1 side (upstream side) with the back pressure chamber 18 by the pressure receiving surface 19 of the relief valve 4, and a second orifice is provided in the middle of this passage. One orifice 20 may be formed.

Note that it is also possible to drive the operating rod 33 by detecting the acceleration of the two-wheeled vehicle, or an operating lever linked to the operating rod 33 may be attached near the handle of the two-wheeled vehicle for manual operation.

(Effects of the invention) As described above, in this invention, the back pressure of the relief valve that generates the compression damping force on the rear wheel side is controlled via the bypass passage, so that when braking a two-wheeled vehicle, the rear wheel side is When the bicycle is in a state where it is lifted compared to when the bicycle is lifted, the damping force can be reduced, which can contribute to improving the running stability of the two-wheeled vehicle.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a partial sectional view, Fig. 3 is a plan view, and Fig. 4 is a sectional view of a main part showing another embodiment. . B... Oil sump chamber, 1... Damper, 2... Housing, 4... Relief valve, 14... Back, 15
... Relief spring, 18 ... Back pressure chamber, 19
...Pressure receiving surface, 20...First orifice, 21...
2nd orifice, 25...spool, 30...bypass passage.

Claims (1)

[Scope of utility model registration request] In hydraulic shock absorbers that suspend the rear wheels of motorcycles,
A relief valve that applies damping force to the pressure side hydraulic oil is provided, and a relief spring that biases the relief valve in the closing direction is provided.A back pressure chamber is defined on the back of the relief valve, and the back pressure chamber and A first orifice that communicates with the high pressure side upstream from the pressure receiving surface of the relief valve, and a second orifice that communicates the back pressure chamber with the low pressure side downstream of the pressure receiving surface of the relief valve are provided. A rear wheel side hydraulic shock absorber for a two-wheeled vehicle, characterized in that a bypass passage communicating with the downstream low pressure side is provided, and a valve is provided for increasing the opening area of the bypass passage during braking.