Damping force variable shock absorber

Abstract

To minimize the decrease in the speed of vehicle height increase due to self-pumping under the influence of the damping force of a damping-force-generating part. A damping force variable shock absorbe

Description

Variable damping force shock absorber

[0001] The present invention relates to a variable damping force shock absorber.

[0002] 2 and 5 of Patent Document 1 show a vehicle height adjusting device that is capable of adjusting the vehicle height by self-pumping and that can adjust the damping force by a control valve having a solenoid.

[0003] Furthermore,

[0014] of Patent Document 2 states that "...even if the vehicle height is deviated from the standard position during vehicle height adjustment, the damping force is set to be greater than the damping force when the vehicle height is not being adjusted, so that with a simple configuration it is possible to suppress the occurrence of hitting the bound stopper or rebound stopper, thereby improving ride comfort."

[0004] International Publication No. 2021 / 044552 Japanese Patent Application Laid-Open No. 2007-245956

[0005] The inventors' investigations have revealed the following problem: In a self-pumping vehicle height control device, the speed at which the vehicle height is raised by self-pumping may decrease due to the influence of the damping force of the damping force generating unit.

[0006] The above-mentioned Patent Document 1 does not mention this problem. Furthermore, Patent Document 2 only discloses a technology for preventing the vehicle height from remaining low when there are a large number of occupants or a large amount of cargo. Patent Document 2 is not related to the above-mentioned problem with self-pump type vehicle height adjustment.

[0007] An object of the present invention is to provide a variable damping force shock absorber that can suppress a decrease in the rate at which the vehicle height increases due to self-pumping, which is affected by the damping force of a damping force generating section.

[0008] As a result of extensive research, the inventors have discovered that by variably controlling the damping force during the spring's pushing and pulling strokes during self-pumping vehicle height adjustment, it is possible to suppress a decrease in the rate at which the vehicle height is raised by self-pumping and also improve handling stability. The present invention was completed based on this discovery.

[0009] According to one aspect of the present disclosure, there can be provided a variable damping force shock absorber (150) including a damping force generating unit (250), a variable damping force actuator (220), and a damping force control unit (210) that controls the operation of the variable damping force actuator, and a height control mechanism (100) including a self-pumping mechanism (69) that uses vibrations accompanying vehicle travel as a driving force to pressurize hydraulic oil and push a spring (60), a variable height actuator (76) that switches the flow path of the hydraulic oil pressurized by self-pumping, and a height control unit (110) that controls the operation of the variable damping force actuator, wherein the damping force control unit (210) performs step-by-step variable damping force control, setting the damping force in the pushing stroke of the spring (60) during a period in which the vehicle height is being raised by the height control mechanism (100) to be weaker than the damping force in the pushing stroke of the spring (60) when the vehicle height is not being raised.

[0010] According to the present invention, it is possible to provide a variable damping force shock absorber that can suppress a decrease in the rate at which the vehicle height increases due to self-pumping, which is affected by the damping force of the damping force generating section.

[0011] 1 is a diagram showing an example of the configuration of a variable damping force shock absorber with a vehicle height adjustment function and an example of the flow of hydraulic oil. FIG. 2 is a diagram showing the flow of hydraulic oil corresponding to each operation of raising, maintaining, and lowering the vehicle height in FIG. 1. FIG. 3 is a diagram showing an example of the flow of hydraulic oil occurring when step-by-step variable damping force control is executed, which variably controls the damping force when raising the vehicle height by self-pumping, and the generated damping force. FIG. 4 is a diagram showing the relationship between the throttle opening of a flow control valve and the damping force. FIG. 5 is a diagram showing the difference in the jack ascent speed when the damping force is set to a weak level or a strong level and step-by-step variable damping force control is not executed. FIG. 6 is a characteristic diagram using a Lissajous curve showing the change in damping force with respect to the stroke length when the damping force is set to a strong level and step-by-step variable damping force control is not executed. FIG. 7 is a diagram showing the difference in the jack ascent speed when the damping force is set to a weak level or a strong level and step-by-step variable damping force control is executed. FIG. 8 is a characteristic diagram using a Lissajous curve showing the change in damping force with respect to the stroke length when the damping force is set to a strong level and step-by-step variable damping force control is executed. 1 is a diagram showing an example of variable damping force control by override type. FIG. 2 is a diagram showing an example of variable damping force control by difference subtraction type. FIG. 3 is a side view of a motorcycle equipped with the variable damping force shock absorber device having the vehicle height adjustment function of FIG.

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. The embodiments shown in the accompanying drawings are merely examples of the present invention, and the present invention is not limited to these embodiments.

[0013] <Example 1> In the following description, the term "variable damping force shock absorber" will be used, but this can also be referred to as a variable damping force shock absorber, a variable damping force damper, a hydraulic damper, or simply a damper. Before describing the detailed configuration of the variable damping force shock absorber, the overall configuration of a motorcycle equipped with the variable damping force shock absorber will be described with reference to Fig. 11. Fig. 11 is a side view of a motorcycle equipped with the variable damping force shock absorber with the vehicle height adjustment function of Fig. 1.

[0014] In the following description, "front" and "rear" refer to the front and rear relative to the direction of travel of the vehicle. Furthermore, "Fr" means "front," "Rr" means "rear," "UP" means "up," and "DOWN" means "down."

[0015] In Figure 11, a motorcycle 1 has a front wheel 2, a rear wheel 3, a body frame 11 that forms the skeleton of the motorcycle 1, an accelerator grip 12, a vehicle body 10 that has an engine 13, etc.

[0016] The motorcycle 1 also has front forks 19 as front suspension parts that connect the front wheel 2 and the vehicle body 10, one on each side of the front wheel 2. The motorcycle 1 also has rear suspensions 22 as rear suspension parts that connect the rear wheel 3 and the vehicle body 10, one on each side of the rear wheel 3.

[0017] The rear suspension 22 has a vehicle body side mounting member 20, a wheel side mounting member 25, and a spring 24. Note that Fig. 11 shows only the front fork 19 and rear suspension 22 arranged on the left side.

[0018] The front fork 19 and the rear suspension 22 are both electronically controlled hydraulic suspensions, and each is equipped with a variable damping force shock absorber according to the present invention.

[0019] Although not shown, the accelerator grip 12 also has a built-in switch. For example, when the driver rotates a predetermined portion of the accelerator grip 12 in a predetermined direction, the switch is turned on to generate a control current, which is then sent to a vehicle height control mechanism (described later) to adjust the vehicle height. During vehicle height adjustment, the vehicle body 10 rises and falls while maintaining its levelness relative to the road surface G.

[0020] Furthermore, a control current may be sent to a damping force control section (described later) by an operation separate from the above operation, so that the damping force of the hydraulic damper can be variably controlled.

[0021] Next, reference is made to Figure 1. Figure 1 is a diagram showing an example of the configuration of a variable damping force shock absorber with a vehicle height adjustment function, and an example of the flow of hydraulic oil. The flow of hydraulic oil includes the flow of hydraulic oil due to self-pumping when the vehicle height is raised, and the flow of hydraulic oil that absorbs the impact of vibrations generated by external forces when the vehicle height is raised.

[0022] The variable damping force shock absorber 150 includes a vehicle height control mechanism 100 and a variable damping force mechanism 200 .

[0023] The vehicle height control mechanism 100 has a spring 60, a jack 62, a jack position sensor 61, a jack chamber 64, hydraulic check valves 70, 86 as check valves, a solenoid valve 76, a storage chamber 84 for storing hydraulic oil, and a pump chamber 66 with a rod 68 provided inside.

[0024] The spring 60 may be referred to as a coil spring or simply as a coil. One end of the spring 60 is disposed so as to be in contact with the reference surface 51.

[0025] The rod 68 in the pump chamber 66 moves up and down or expands and contracts due to vibrations caused by the vehicle traveling, pressurizing and moving the hydraulic oil. This pressurizing action of the hydraulic oil using the vibrations caused by traveling as a driving force is referred to as self-pumping in this specification. Self-pumping makes it possible to pressurize and move the hydraulic oil using the vibrations caused by the vehicle traveling as a power source, even without a specific electrical power source. The pump chamber 66 and the rod 68 constitute a self-pumping mechanism 69. One end of the rod 68 is installed so as to contact the reference surface 51.

[0026] The solenoid valve 76 is a type of electromagnetic switching valve that switches the flow path of hydraulic oil, and the amount of current flowing through the built-in solenoid is variably controlled to switch between opening and closing the first flow path 80 and the second flow path 82. The solenoid valve 76 functions as a vehicle height variable actuator.

[0027] The vehicle height control unit 110 also has a vehicle height variable actuator drive unit 112. The vehicle height variable actuator drive unit 112 supplies a control current with an adjusted current amount to the solenoid valve 76 serving as the vehicle height variable actuator. This control current can also be referred to as a first control signal S1.

[0028] The vehicle height control unit 110 is supplied with a detection signal from a wheel speed sensor 114 and also with a jack position detection signal from a jack position sensor 61 .

[0029] On the other hand, the damping force variable mechanism 200 has a hydraulic damper 230, a flow control valve as a damping force variable actuator, specifically, for example, an electromagnetic proportional throttle valve 220, and a damping force control unit 210 that controls the operation of the electromagnetic proportional throttle valve 220.

[0030] The electromagnetic proportional throttle valve 220 and the hydraulic damper 230 constitute a damping force generating section 250 .

[0031] The electromagnetic proportional throttle valve 220 changes its throttle opening in proportion to the amount of current flowing through a proportional solenoid (not shown), and can continuously change the flow rate of hydraulic oil.

[0032] The damping force control unit 210 has a damping force variable actuator drive unit 212. The damping force variable actuator drive unit 212 supplies a control current with an adjusted current amount to the proportional solenoid of the electromagnetic proportional throttle valve 220, which serves as an actuator. This control current can also be called a second control signal S2. This control current can change the throttle opening of the electromagnetic proportional throttle valve 220, for example, continuously, thereby variably controlling the damping force.

[0033] The damping force control unit 210 is supplied with detection signals from a wheel speed sensor 214 and an acceleration sensor 216 , as well as a detection signal from a stroke sensor 218 that detects the stroke of the hydraulic damper 230 .

[0034] The hydraulic damper 230 has a damper tube 233, a piston 240, a piston rod 242, an upper oil chamber 232, and a lower oil chamber 234. One end of the piston rod 242 is connected to the piston 240, and the other end is installed so as to contact the reference surface 51.

[0035] When the piston 240 moves upward and the upper oil chamber 232 is compressed, hydraulic oil flows from the damper tube 233 to the jack chamber 64, compressing the spring 60.

[0036] Furthermore, when the piston 240 moves downward and the lower oil chamber 234 is compressed, hydraulic oil flows from the jack chamber 64 to the damper tube 233, and the hydraulic oil flows into the damper tube 233, causing the spring 60 to expand.

[0037] Piston 240 is provided with a flow path consisting of check valve 243 and throttle valve 245, in other words, a first orifice, and a flow path consisting of throttle valve 247 and check valve 249, in other words, a second orifice. By appropriately setting each of throttle valves 245, 247, it is possible to adjust the damping force characteristics of the hydraulic damper.

[0038] Alternatively, each of the throttle valves 245, 247 may be provided with a throttle setting section that can set the throttle amount, so that the driver can manually operate the setting section to variably set the damping force.

[0039] When there is no increase in vehicle height due to self-pumping, the damping force control section 210 and the vehicle height control section 110 can independently execute control operations.

[0040] On the other hand, when the vehicle height is increased due to self-pumping, the damping force control unit 210 and the vehicle height control unit 110 can perform cooperative control by interrelating the variable damping force control and the vehicle height control. Cooperative control can be defined as control in which the output result of one control unit changes adaptively depending on the state of the other control unit, for example.

[0041] For example, as will be described later, the damping force control unit 210 performs step-by-step variable damping force control that changes the damping force value when the vehicle height increases. The timing of this control operation is preferably synchronized with the timing of the vehicle height variable control performed by the vehicle height control unit 110, i.e., the timing of the flow path switching operation of the solenoid valve 76, which is an electromagnetic switching valve. Therefore, it is preferable that the timings of the control units 110 and 210 are matched and the control operations are synchronized with each other.

[0042] In this case, for example, the vehicle height control unit 110 may send a timing control signal as a control signal S3 to the damping force control unit 210, and the damping force control unit 210 may determine the start timing of the step-by-step variable damping force control based on the received timing control signal.

[0043] Furthermore, while the vehicle height is rising, the vehicle height control unit 110 calculates the vehicle height rising speed based on the detection signal from the jack position sensor 61, and transmits the calculation result to the damping force control unit 210 as a control signal S3. The damping force control unit 210 may then appropriately change the damping force switching period in the step-by-step variable damping force control based on the received information on the vehicle height rising speed.

[0044] It is also conceivable that an abnormality may occur during the vehicle height increase, causing a disturbance in the movement of the piston 240 of the damping force generating unit 250. In such a case, the damping force control unit 210 sends a signal informing the vehicle height control unit 110 of the abnormality as a control signal S4, and in response, the vehicle height control unit 110 can perform a coordinated operation in which it temporarily stops the vehicle height increase operation and switches to a vehicle height maintenance operation.

[0045] These linked operations are merely examples, and the contents of the cooperative control are not limited to the linked operations described above.

[0046] By having the damping force control unit 210 and the vehicle height control unit 110 work together to perform cooperative control, the timing of each control is synchronized, enabling efficient and stable vehicle height adjustment. Furthermore, if an abnormality occurs, the two control units work together to respond, which is expected to have the effect of speeding up the recovery from the abnormal state to the normal state.

[0047] Next, the operation of each part and the flow of hydraulic oil when the vehicle height is raised will be described. In Fig. 1, the flow of hydraulic oil is indicated by arrows of solid lines, dashed lines, and dashed lines.

[0048] When the power supply of a vehicle, for example, a motorcycle, is turned on, the height-adjustable actuator drive unit 112 supplies, for example, a low current of three levels of control current as a first control signal S1 to the solenoid valve 76. This causes the first flow path 80 in the solenoid valve 76 to close, allowing the vehicle height to be raised.

[0049] When the vehicle starts moving and self-pumping begins due to unevenness in the road surface, the hydraulic oil is pressurized, the check valve 70 opens, and the hydraulic oil moves from the pump chamber 66 to the jack chamber 64, as shown by the solid arrow LE.

[0050] This causes the jack 62 to move downward, shortening the length of the spring 60. The shortening of the length of the spring 60 means that the reaction force of the spring 60 increases, and the force resisting the load applied to the vehicle body 10 increases, causing the vehicle height to rise.

[0051] In this way, the spring 60 is compressed by self-pumping. However, apart from the compression caused by self-pumping, the spring 60 is constantly vibrating finely due to vibrations while the vehicle is running. To absorb the shock caused by this vibration, the hydraulic oil moves in response to the vibrations, and the shock is absorbed by the electromagnetic proportional throttle valve 220 and the hydraulic damper 230.

[0052] The electromagnetic proportional throttle valve 220 absorbs shock by restricting the movement of hydraulic oil through throttling, while the hydraulic damper 230 absorbs shock by restricting the movement of hydraulic oil through the vertical movement of the piston 240, in other words, by restricting the movement of hydraulic oil through throttling of the throttle valves 243 and 249 that form orifices provided in the piston 240.

[0053] If the flow rate of the moving hydraulic oil is large, the force that reduces the impact of the vibration of the spring 60 and converges the vibration of the spring 60, that is, the damping force, becomes weaker, and the vibration continues for a longer period of time.

[0054] If the flow rate of the moving hydraulic oil is small, the damping force will be strong and vibrations will be quickly contained. The ride comfort will change depending on the magnitude of the damping force. Also, if the damping force is large, the energy that the hydraulic oil uses to move as it slides along the inner wall of the pump chamber during self-pumping tends to decrease. Therefore, the damping force generated by the variable damping force damper must be set appropriately, taking into account the speed at which the vehicle height rises due to self-pumping.

[0055] When the spring 60 is compressed by vibration, a hydraulic oil flow LD1 is generated, as indicated by the dashed line in Fig. 1. In this case, the hydraulic oil is pushed out of the damper tube 233 of the hydraulic damper 230, passes through the electromagnetic proportional throttle valve 220 and the check valves 86 and 70, and moves to the jack chamber 64. Furthermore, a hydraulic oil flow LD3, as indicated by the dashed arrow, is generated within the damper tube 233.

[0056] When the spring 60 expands due to vibration, a hydraulic oil flow LD2, indicated by the dashed line in Fig. 1, occurs. In this case, the hydraulic oil is forced out of the jack chamber 64 and moves to the upper oil chamber 232 of the hydraulic damper 230 via the second flow path 82 of the solenoid valve 76, the reservoir chamber 84, and the electromagnetic proportional throttle valve 220. Furthermore, a hydraulic oil flow LD4, indicated by the dashed arrow, occurs within the damper tube 233.

[0057] Next, reference is made to Figure 2. Figure 2 is a diagram showing the flow of hydraulic oil corresponding to each operation of raising, maintaining, and lowering the vehicle height in Figure 1. In Figure 2, the same parts as in Figure 1 are given the same reference numerals. Since raising the vehicle height has already been explained, the operations of maintaining and lowering the vehicle height will be explained here.

[0058] First, the vehicle height maintaining operation will be described. When the jack 62 reaches a predetermined target position, the jack position sensor 61 detects this and sends a detection signal to the vehicle height control unit 110. In response, the vehicle height control unit 110 supplies a middle current of the three-stage control current to the solenoid valve 76 as a first control signal S1.

[0059] In this case, as shown by the dashed-dotted arrow LG, the hydraulic oil moves through the first flow path 80, the reservoir chamber 84, and the check valve 86, but the same amount of hydraulic oil sent out from the pump chamber 66 is returned to the pump chamber 66, and the amount of hydraulic oil in the jack chamber 64 does not change. Therefore, the vehicle height is maintained.

[0060] When the vehicle height is to be lowered, the height-adjustable actuator driving unit 112 supplies a high current of the three-stage control current to the solenoid valve 76 as the first control signal S1.

[0061] In this case, as indicated by the dashed arrow LF, the hydraulic oil moves from the jack chamber 64 to the pump chamber 66 via the second flow path 82 of the solenoid valve 76, the reservoir chamber 84, and the check valve 86. As a result, the spring 60 expands, and therefore the length of the spring 60 increases.

[0062] Increasing the length of the spring 60 means that the reaction force of the spring 60 decreases, and the force resisting the load applied to the vehicle body 10 weakens, causing the vehicle height to decrease.

[0063] Next, reference is made to Fig. 3. Fig. 3 is a diagram showing an example of the flow of hydraulic oil that occurs when variable damping force control by step is performed, which variably controls the damping force when the vehicle height is raised by self-pumping, and the damping force that is generated. In Fig. 3, the same parts as in the previous figures are assigned the same reference numerals.

[0064] When the vehicle starts traveling, the vehicle body moves up and down due to unevenness in the road surface, and in response to this, an external force in the pushing direction that pushes and compresses the spring 60 and an external force in the pulling direction that pulls and extends the spring 60 occur alternately. In other words, the vibration of the spring 60 due to the external force alternates between a pushing process and a pulling process.

[0065] In FIG. 3, an external force in the pushing direction is represented as C-force (compression-force), and a damping force that damps the external force in the pushing direction is represented as Dum-Cforce (Dumping-Cforce).

[0066] Furthermore, an external force in the pulling direction is expressed as E-force (Elongation-force), and a damping force that damps the external force in the pulling direction is expressed as Dum-Eforce (Dumping-Eforce).

[0067] In the following description, the damping force Dum-Cforce that damps an external force in the pushing direction will be referred to as the damping force in the spring's pushing stroke, and the damping force Dum-Eforce that damps an external force in the pulling direction will be referred to as the damping force in the spring's pulling stroke.

[0068] 3, C-force and E-force are indicated by solid arrows, and Dum-Cforce and Dum-Eforce are indicated by hollow arrows.

[0069] The flow direction of hydraulic oil in Fig. 3 is the same as in Fig. 1. However, Fig. 3 differs from Fig. 1 in that step-by-step variable damping force control is executed to variably control the damping force when the vehicle height is increased.

[0070] As explained above, the driver can set the strength of the damping force generated by the damping force variable mechanism 200 to his or her liking by using electronic control or by manual setting.

[0071] The damping force of the damping force generating unit 250 can be set to at least a first level that is a relatively weak damping force and a second level that is a relatively strong damping force. When the damping force is at the first level, the ride quality is so-called soft, and when the damping force is at the second level, the ride quality is so-called hard.

[0072] Here, according to the inventors' investigations, it has become clear that, for example, when the damping force is set to the relatively strong second level, the vibration of the spring 60 caused by unevenness in the road surface converges quickly, which tends to result in a shortage of vibration that serves as the driving force for raising the vehicle height through self-pumping, and this can result in a decrease in the rate at which the vehicle height rises.

[0073] Therefore, in order to suppress the decrease in the vehicle height increasing speed, step-by-step variable damping force control is executed in the example of FIG.

[0074] As described above, the damping force of the damping force generation unit 250 can be set to at least a first level at which the damping force is relatively weak and a second level at which the damping force is relatively strong, and the damping force control unit 210 may execute step-by-step variable damping force control when the damping force of the damping force generation unit 250 is set to the first level or the second level and the vehicle height is being raised by self-pumping. In the following description, it is assumed that the damping force is set to the second level, i.e., a relatively strong level, and that in this situation the vehicle has started to move and control to raise the vehicle height by self-pumping has begun.

[0075] This is because when the damping force is set at a relatively weak level, it is thought that the vibrations that are the driving force behind self-pumping are unlikely to be excessively suppressed, whereas when the damping force is set at a relatively strong level, there is a tendency for the vibrations to be excessively suppressed, and it is often necessary to take measures.

[0076] By the variable damping force control by step described later, the vibrations that are the driving force behind self-pumping are not excessively suppressed, and the vehicle height rising speed or handling stability can be improved.

[0077] However, this is just one example and is not limiting. That is, even when the damping force is set to the first level, i.e., a relatively weak level, step-by-step variable damping force control may be performed if necessary. In this case, for example, it is possible to suppress the amplitude of vehicle height fluctuation when the vehicle height has reached a desired height position, thereby obtaining the effect of improving ride comfort.

[0078] In FIG. 3, the dashed arrow indicating the flow LD1 of hydraulic oil during the pushing stroke of the spring 60 is shown in bold, which indicates that the flow rate is large.

[0079] The fact that the flow rate of hydraulic oil flow LD1 during the pushing stroke of spring 60 is large means that the damping force Dum-Cforce generated by hydraulic oil flow LD1 is set small. In Figure 3, the length of the outline arrow indicating Dum-Cforce is drawn short.

[0080] On the other hand, the flow rate of the hydraulic oil flow LD2 during the pulling stroke of the spring 60 is the same as or smaller than that in Fig. 1. In Fig. 3, the flow rate of the hydraulic oil flow LD2 is depicted as being the same as that in Fig. 1. In Fig. 3, the length of the hollow arrow indicating Dum-Eforce is depicted as being longer.

[0081] The damping force Dum-Cforce during the pushing stroke of the spring 60 is set small because the external force C-force in the pushing direction acts in a direction that compresses the spring 60, and is therefore a useful external force that enhances the rise in vehicle height due to self-pumping, and significantly reducing this force is undesirable from the perspective of improving the speed at which the vehicle height rises.

[0082] On the other hand, it is preferable to change the damping amount for the external force E-force in the pulling direction from the viewpoint of improving the vehicle height raising speed. However, because changing the damping amount affects the ride comfort, in the example of Fig. 3, the damping force Dum-Eforce is set to the same regardless of whether the jack is being raised or not, i.e., whether the vehicle height is being raised or not.

[0083] According to the variable damping force control by step, the damping force Dum-Cforce during the pushing stroke of the spring 60 is set small, and the damping force Dum-Eforce during the pulling stroke of the spring 60 is not changed, so the pushing side damping force of the entire suspension can be made equal whether the jack is rising or not.

[0084] On the other hand, since the damping force Dum-Cforce during the pushing stroke of the spring 60 is set small, the useful external force C-force that increases the rise in vehicle height due to self-pumping is not significantly reduced, and it is possible to ensure a certain degree of vibration that serves as the driving force for self-pumping, thereby suppressing a decrease in the rate at which the vehicle height rises.

[0085] As described above, the variable damping force shock absorber 150 has a variable damping force mechanism 200 including a damping force generating unit 250, a variable damping force actuator 220, and a damping force control unit 210 that controls the operation of the variable damping force actuator, a self-pumping mechanism 69 that uses vibrations associated with the vehicle's travel as a driving force to pressurize the hydraulic oil and push the spring 60, a variable height actuator 76 that switches the flow path of the hydraulic oil pressurized by self-pumping, and a height control unit 110 that controls the operation of the variable damping force actuator, and the damping force control unit 210 performs variable damping force by step control, whereby the damping force during the pushing stroke of the spring 60 while the vehicle height is being raised by the height control mechanism 100 is set to a weaker value than the damping force during the pushing stroke of the spring 60 when the vehicle height is not being raised, i.e., the normal setting.

[0086] This maintains an appropriate damping force to achieve the ride comfort desired by the driver, while at the same time not excessively suppressing the external vibration force that is the driving force behind self-pumping, leaving a certain amount of vibration component and ensuring the required vehicle height adjustment speed. Furthermore, reducing the difference in damping characteristics between when the vehicle height is rising and when it is not can also have the effect of improving handling stability. This point will be discussed later.

[0087] Next, reference is made to Fig. 4, which is a diagram showing the relationship between the throttle opening of the flow control valve and the damping force. In Fig. 4, the same parts as in Fig. 3 are given the same reference numerals.

[0088] A-1 in Figure 4 shows an example of the throttle opening of the flow control valve and an example of the generated damping force when self-pumping is present and the damping force is set to a weak level. As shown in A-1-1 and A-1-2, the throttle opening of the flow control valve 220 is both set to large. The flow rates of the hydraulic oil flows LD1 and LD2 are both large. As shown in A-1-3, the damping force Dum-Cforce during the pushing stroke of the spring 60 and the damping force Dum-Eforce during the pulling stroke of the spring 60 are both small.

[0089] A-2 in Figure 4 shows an example of the throttle opening of the flow control valve and an example of the generated damping force when self-pumping is present and the damping force is set to a strong level. As shown in A-2-1 and A-2-2, the throttle opening of the flow control valve 220 is both set to small. The flow rates of the hydraulic oil flows LD1 and LD2 are both small. As shown in A-2-3, the damping force Dum-Cforce during the pushing stroke of the spring 60 and the damping force Dum-Eforce during the pulling stroke of the spring 60 are both large.

[0090] A-3 in Figure 4 shows an example of the throttle opening of the flow control valve and an example of the damping force generated when self-pumping is present, the damping force is set to a strong level, and step-by-step variable damping force control is executed.

[0091] As shown in A-3-1, during the pressing stroke of the spring 60, the throttle opening of the flow control valve 220 is set to large, and the flow rate of the hydraulic oil flow LD1 increases. Therefore, the damping force Dum-Cforce decreases.

[0092] As a result, the damping of the external force C-force that is useful for raising the vehicle height is alleviated, and the vibration caused by this external force is maintained to a certain extent. Therefore, the vibration that is the driving force for raising the vehicle height remains without being excessively damped, and the decrease in the vehicle height raising speed is alleviated.

[0093] On the other hand, as explained above, during the retraction stroke of the spring 60, the damping force Dum-Eforce during the retraction stroke of the spring 60 is not changed. Therefore, the push-side damping force of the entire suspension can be made equal whether the jack is rising or not. The throttle opening of the flow control valve 220 is set to small, and the flow rate of the hydraulic oil flow LD2 is reduced. Therefore, the damping force Dum-Eforce increases. As a result, the external force E-force that hinders an increase in vehicle height is greatly damped in accordance with the initial damping force setting. This ensures the firm ride comfort desired by the driver.

[0094] In this way, it is possible to realize a desired ride comfort and a desired vehicle height raising speed. In other words, it is possible to achieve both a ride comfort and a desired vehicle height raising speed.

[0095] Next, reference is made to Fig. 5. Fig. 5 is a diagram showing the difference in the jack ascent speed when the damping force is set to a weak value or a strong value and when step-by-step variable damping force control is not performed.

[0096] In FIG. 5, the horizontal axis indicates the elapsed time since the start of self-pumping, and the vertical axis indicates the position of the jack.

[0097] The characteristic line Q1 shows the change in jack position over time when the damping force is set to a weak level and when step-by-step variable damping force control is not performed. This characteristic line Q1 corresponds to the example A-1 in Figure 4.

[0098] In the example shown by characteristic line Q1, the jack position reaches the target position TR at time t1. Time t2 corresponds to the maximum allowable time Tc. In the example shown by characteristic line Q1, the jack position reaches the target position TR within the allowable time Tc.

[0099] On the other hand, characteristic line Q2 shows the change in jack position over time when the damping force is set to a strong level and when step-by-step variable damping force control is not performed. This characteristic line Q2 corresponds to the example of A-2 in Figure 4.

[0100] In the example shown by characteristic line Q2, the jack position reaches the target position TR at time t3. In the example of characteristic line Q2, it takes longer than the allowable time Tc for the jack position to reach the target position TR. Therefore, it is required that the jack position reach the target position within the allowable time Tc.

[0101] Next, reference is made to Fig. 6. Fig. 6 is a characteristic diagram using a Lissajous curve, which shows the change in damping force relative to the stroke length when the damping force is set to a strong level and when step-by-step variable damping force control is not performed.

[0102] A characteristic line Q10 indicates the characteristics when there is no self-pumping operation to raise the vehicle height, and a characteristic line Q20 indicates the characteristics when there is a self-pumping operation to raise the vehicle height.

[0103] The damping force value of characteristic line Q20 is significantly greater than the damping force value of characteristic line Q10. In other words, during self-pumping, the shape of the Lissajous curve deviates from its normal shape. This is because during self-pumping, a force pushing up the jack is constantly acting in addition to the normal external force acting on the spring. Therefore, the external force appears to increase by the force pushing up the jack or the reaction force of that force. As a result, the generated damping force tends to be higher than the design value.

[0104] If the actual damping force during self-pumping deviates from the design value, it may affect the vehicle's handling stability, and it may become impossible to operate the vehicle as the driver intends or expects. Therefore, it is necessary to suppress such deviation and bring the damping value during self-pumping closer to the design value.

[0105] Next, reference is made to Fig. 7. Fig. 7 is a diagram showing the difference in the jack rising speed when the damping force is set to a weak level or a strong level and when step-by-step variable damping force control is performed.

[0106] In Fig. 7, the same parts as in Fig. 6 are denoted by the same reference numerals, except that the characteristic line Q2 in Fig. 6 is shown by a dashed line.

[0107] The characteristic line Q3 in Fig. 7 shows the change in jack position over time when the damping force is set to a strong level and when the step-by-step variable damping force control described above with reference to Fig. 3 and Fig. 4 is performed. This characteristic line Q3 corresponds to the example A-3 in Fig. 4.

[0108] As explained above with reference to Figures 3 and 4, when variable damping force control by step is performed, the combined damping force of the damping forces in the spring's push stroke and pull stroke is reduced from the original strong level damping force to a medium level damping force. This ensures that the vibrations that drive self-pumping are not excessively suppressed and that a certain level of vibration is maintained.

[0109] Therefore, in the example of characteristic line Q3, the vehicle height raising speed by self-pumping is improved compared to the example shown by characteristic line Q2.

[0110] Therefore, in the example shown by characteristic line Q3, the jack position reaches the target position TR at time t4. In other words, the jack can reach the target position within the allowable time Tc. This solves the problem described in FIG. 5 and improves the vehicle height raising performance by self-pumping. Furthermore, characteristic line Q4 in FIG. 7 shows the change in jack position over time when the damping force is set to a weak level and step-by-step variable damping force control is implemented. Characteristic line Q4 corresponds to characteristic line Q1 in FIG. 5 shown above. In characteristic line Q4, when the jack position reaches near the target position TR, i.e., after time t2, the amplitude fluctuation is suppressed compared to characteristic line Q1. In other words, step-by-step variable damping force control can suppress the amplitude of vehicle height fluctuation. This results in an improved ride comfort.

[0111] Next, reference is made to Fig. 8. Fig. 8 is a characteristic diagram using a Lissajous curve, which shows the change in damping force relative to the stroke length when the damping force is set to a strong level and step-by-step variable damping force control is performed.

[0112] A characteristic line Q10 indicates the characteristic when there is no self-pumping operation to raise the vehicle height, and a characteristic line Q30 indicates the characteristic when there is a self-pumping operation to raise the vehicle height and step-by-step variable damping force control is being performed.

[0113] As explained previously with reference to Figures 3 and 4, when the step-by-step variable damping force control is implemented, the damping force Dum-Cforce in the pushing stroke of the spring 60 is set small and the damping force Dum-Eforce in the pulling stroke of the spring 60 is not changed, so the pushing-side damping force of the entire suspension can be made equal whether the jack is rising or not.

[0114] Therefore, the damping force value of the characteristic line Q30 during self-pumping becomes smaller, and the characteristic line Q30 approaches the characteristic line Q10 during normal operation.

[0115] In other words, in the example of characteristic line Q30, the shape of the Lissajous curve during self-pumping is prevented from deviating from its normal shape. As a result, the actual damping force during self-pumping does not deviate significantly from the design damping force. This improves the vehicle's handling stability, making it easier for the driver to operate the vehicle in accordance with their intentions and expectations.

[0116] <Embodiment 2> Next, reference is made to Fig. 9. Fig. 9 is a diagram showing an embodiment of the override type variable damping force control by step. Fig. 9 shows the control during the rise of the vehicle height.

[0117] In the example of Figure 9, the damping force control unit 210 has a calculation unit 302 that calculates a control signal value, in other words, a control current value, of an electromagnetic proportional throttle valve 220 serving as a variable damping force actuator, an override setting unit 304 that overwrites the current control signal value with the calculated new control signal value when updating the control signal value in the step-by-step variable damping force control, and a damping force variable actuator driving unit 212 that drives the variable damping force actuator 220 based on the control signal value read from the override setting unit 304.

[0118] 9, the period from time t10 to t11 is the pulling process period TA1 of the spring 60, the period from time t11 to t12 is the pushing process period TB1 of the spring 60, the period from time t12 to t13 is the pulling process period TA2 of the spring 60, and the period from time t13 to t14 is the pushing process period TB2 of the spring 60. As explained above, during the pulling process periods TA1 and TA2, the damping force is the same as the damping force when there is no increase in vehicle height, and is not changed. During the pushing process periods TB1 and TB2, the damping force is set to be weaker than the damping force when there is no increase in vehicle height.

[0119] 9, for example, a storage device such as an override register is used as the override setting unit, and by adjusting the timing of writing to and reading from the storage device, the series of operations can be carried out efficiently. The override method has the advantage that the timing can be easily adjusted.

[0120] <Embodiment 3> Next, reference is made to Fig. 10. Fig. 10 is a diagram showing an embodiment of step-by-step variable damping force control using a difference subtraction method. In Fig. 10, the same parts as in Fig. 9 are assigned the same reference numerals.

[0121] 10, the period from time t10 to t11 is the pulling process period TA1 of the spring 60, the period from time t11 to t12 is the pushing process period TB1 of the spring 60, the period from time t12 to t13 is the pulling process period TA2 of the spring 60, and the period from time t13 to t14 is the pushing process period TB2 of the spring 60. As explained above, during the pulling process periods TA1 and TA2, the damping force is the same as the damping force when there is no increase in vehicle height, and is not changed. During the pushing process periods TB1 and TB2, the damping force is set to be weaker than the damping force when there is no increase in vehicle height.

[0122] The damping force control unit 210 has a calculation unit 404 that, when updating the control signal value of the electromagnetic proportional throttle valve 220 as a damping force variable actuator, in other words the control current value, calculates a new control signal value by subtracting a second value, which is a constant value or a variable whose value changes depending on the situation, from a first reference value.

[0123] The first reference value may be, for example, a control signal value corresponding to the current attenuation value, or a control signal value that is a fixed value that is prepared in advance.

[0124] When the second value is a variable, the second value, which is a difference value, needs to be calculated, and therefore a difference value calculation unit 402 is provided before the calculation unit 404. Note that when the second value, which is a difference value, is a constant value, in other words a fixed value, the second value does not need to be calculated, and therefore the difference value calculation unit 402 is not required.

[0125] Furthermore, if timing adjustment is required, a transfer control unit 405 such as a transfer gate with an output enable function may be provided in the signal transmission path, and the output timing of the signal may be adjusted by an output enable signal, thereby enabling accurate timing control.

[0126] 10, the control signal value can be calculated by calculation alone without writing / reading to / from a storage device, which shortens the time required to obtain the control signal and thus makes it possible to handle high-frequency vibrations. The subtraction method has the advantage of being able to quickly obtain the control signal value.

[0127] Thus, according to the embodiment of the present invention, the damping force can be appropriately adjusted to prevent the damping force from becoming excessively high, thereby achieving good handling stability and improving ride comfort, and also achieving the effect of shortening the time required for vehicle height adjustment.

[0128] The present invention is not limited to the above description and can be modified and applied in various ways. For example, the damping force control unit 210 may execute step-by-step variable damping force control when the spring 60 is fully compressed. While the spring 60 is being compressed, the reaction force of the spring 60 changes, making it difficult to adjust the damping force. Therefore, the damping force change control is executed when the spring 60 is fully compressed, enabling accurate adjustment. Note that it is possible to detect that the spring 60 has reached the fully compressed state by detecting the stroke direction of the spring 60 using, for example, an acceleration sensor or the like.

[0129] Furthermore, the damping force control unit 210 may vary the amount of damping force control in the step-by-step variable damping force control in accordance with the vehicle speed or the spring stroke speed. For example, since the vehicle height increase speed and ride comfort due to self-pumping are affected by the vehicle speed or the spring stroke speed, optimizing the amount of damping force control in consideration of the vehicle speed and the stroke speed makes it possible to achieve both the vehicle height increase speed and ride comfort. For example, if the vehicle speed suddenly increases, for example, beyond a predetermined value, or the stroke speed suddenly increases, for example, beyond a predetermined value, immediately after the vehicle starts traveling, it is considered that there is a lot of vibration that is useful for self-pumping, and therefore the degree to which the damping force is weakened in the spring push stroke may be reduced.

[0130] Although the above description has been given taking a motorcycle as an example, the present invention can also be applied to three-wheeled and four-wheeled vehicles, and the type of vehicle is not important.

[0131] As described above, according to the present invention, it is possible to provide a variable damping force shock absorber that can suppress a decrease in the rate at which the vehicle height increases due to self-pumping, which is influenced by the damping force of the damping force generating section.

[0132] As long as the functions and effects of the invention are exhibited, the present invention is not limited to the examples.

[0133] The present invention is suitable for use as an electronically controlled variable damping force shock absorber that allows adjustment of the vehicle height of a motorcycle, for example.

[0134] DESCRIPTION OF SYMBOLS 1...Vehicle (motorcycle) 2...Front wheel 3...Rear wheel 10...Vehicle body 11...Vehicle frame 12...Accelerator grip (accelerator grip as an operating part having at least one of a built-in switch for damping force control and a built-in switch for vehicle height control) 13...Engine 19...Front fork (front suspension part) 20...Vehicle body side mounting member 22...Rear suspension (rear suspension part) 24...Spring (suspension spring) 25...Wheel side mounting member 60...Spring 61...Jack position sensor 62...Jack 64...Jack chamber (jack oil chamber) 66...Pump chamber 68...Rod (self-pumping rod, pumping rod) 70, 86...Check valve (hydraulic check valve) 76...Solenoid valve (electromagnetic switching valve, vehicle height variable actuator) 84...Storage chamber 100...Vehicle height control mechanism 110...Vehicle height control part DESCRIPTION OF SYMBOLS 112...Variable vehicle height actuator drive unit 114...Wheel speed sensor 150...Variable damping force shock absorber (variable damping force shock absorber, variable damping force damper, damper) 200...Variable damping force mechanism 210...Damping force control unit 212...Variable damping force actuator drive unit (unit for executing variable damping force control) 214...Wheel speed sensor 216...Acceleration sensor 218...Stroke sensor 220...Flow rate control valve (electromagnetic proportional throttle valve, variable damping force actuator) 230...Hydraulic damper 250...Damping force generation unit 232...Upper oil chamber (compression side oil chamber) 233...Damper tube 234...Lower oil chamber (extension side oil chamber) 240...Piston 242...Piston rod 243, 249...Check valves 245, 247...Throttle valve 302...Calculation unit (unit for calculating control signal value corresponding to damping value) 304...Setting unit (override setting unit, storage device) 402... Calculation unit (calculation unit that calculates a difference value, calculation unit for a second value) 404... Calculation unit (calculation unit that calculates a control signal value by subtraction) 405... Transfer unit (transfer gate, etc.)

Claims

1. A variable damping force shock absorber comprising: a variable damping force mechanism comprising a damping force generating unit, a variable damping force actuator, and a damping force control unit that controls the operation of the variable damping force actuator; and a height control mechanism comprising: a self-pumping mechanism that uses vibrations associated with the running of a vehicle in which the variable damping force mechanism is installed as a driving force to pressurize hydraulic oil and push a spring, a variable height actuator that switches the flow path of the hydraulic oil pressurized by self-pumping, and a height control unit that controls the operation of the variable height actuator, wherein the damping force control unit performs variable damping force by step control, setting the damping force in the pushing process of the spring during the period in which the vehicle height is being raised by the height control mechanism to be weaker than the damping force in the pushing process of the spring when the vehicle height is not being raised.

2. A variable damping force shock absorber as described in claim 1, wherein the damping force control unit and the vehicle height control unit each perform control operations independently when there is no increase in vehicle height due to self-pumping, and when there is an increase in vehicle height due to self-pumping, the damping force control unit and the vehicle height control unit perform cooperative control by interrelating the variable damping force control and the vehicle height control.

3. A variable damping force shock absorber according to claim 1, wherein the damping force of the damping force generating unit can be set to at least a first level at which the damping force is relatively weak and a second level at which the damping force is relatively strong, and the damping force control unit executes the step-by-step variable damping force control when the damping force of the damping force generating unit is set to the first level or the second level and the vehicle height is being increased by self-pumping.

4. A variable damping force shock absorber according to claim 1, wherein the damping force control section executes the variable damping force control by step when the spring is fully compressed.

5. A variable damping force shock absorber according to claim 1, wherein the damping force control section changes the amount of control of the damping force in the step-by-step variable damping force control in accordance with the vehicle speed or the stroke speed of the spring.

6. A variable damping force shock absorber as described in claim 1, wherein the damping force control unit has: a calculation unit that calculates a control signal value for the variable damping force actuator; and an override setting unit that overwrites the current control signal value with the calculated new control signal value when updating the control signal value in the step-by-step variable damping force control.

7. A variable damping force buffer device as described in claim 1, wherein the damping force control unit has a calculation unit that, when updating the control signal value of the variable damping force actuator in the step-by-step variable damping force control, calculates a new control signal value by subtracting a second value, which is a constant value or a variable whose value changes depending on the situation, from a first reference value.

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