JP5109883B2 - Electronically controlled suspension device, step-out correction method - Google Patents

Description

  The present invention relates to an electronically controlled suspension apparatus having a variable damping force, and more particularly to an electronically controlled suspension apparatus and a step-out correcting method capable of correcting a step-out between a command value damping force and an actual damping force.

  The electronically controlled suspension with variable damping force reduces the damping force, assuming that the direction of relative displacement of the sprung member and unsprung member in the vertical direction of the vehicle and the direction of relative speed are in the excitation direction. If they do not match, the damping force is variably controlled in accordance with the traveling condition, for example, the damping force is increased because it is in the vibration damping direction.

  In order to make the damping force variable, a structure is often used in which the opening of the throttle valve of the shock absorber is controlled by an actuator to adjust the speed at which the hydraulic oil passes through the throttle valve. For this reason, the actuator is driven by a microcomputer or the like so as to obtain a desired damping force. However, when open control is used instead of feedback control, the instructed damping force and the actual damping force do not coincide with each other. . Once out of step, the instructed damping force and the actual damping force continue to deviate from each other.

  Therefore, techniques for preventing step-out and eliminating step-out have been considered (for example, refer to Patent Documents 1 and 2). In Patent Document 1, if the estimated piston speed of the shock absorber is equal to or higher than a predetermined value, it is determined that there is a possibility of a step-out state, and the step-out that causes the step motor to rotate until it comes into contact with the stopper serving as the origin is eliminated. A method is described.

Further, in Patent Document 2, when a predetermined time elapses or when the damping force is changed a predetermined number of times or more, the step motor rotates until it abuts against a stopper serving as a reference position for vibration suppression or vibration. The solution method of is described.
JP 7-186658 A Japanese Patent Laid-Open No. 5-38919

  However, the step-out elimination method described in Patent Document 1 or 2 has a problem in that an uncomfortable feeling occurs in ride comfort and operational stability because the actuator is driven until the stopper contacts the stopper during the step-out elimination operation. Further, since the step motor is rotationally driven again to a position where a desired damping force can be obtained once contacted with the stopper, there is also a problem that it takes time for the canceling operation.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention minimizes the discomfort of riding comfort felt by the occupant during the resolution of step-out, and completes the step-out cancellation in a short time and the step-out correction. It aims to provide a method.

  In view of the above problems, the present invention provides a shock absorber in which two chambers communicate with each other by a flow path, a throttle valve that adjusts the effective flow path area of the flow path, an electric motor that drives the throttle valve, and a rotation range of the electric motor. A pair of rotation restricting means for restricting, a sensor for detecting a vertical motion state of the vehicle body, and a damping force calculating means for calculating the damping force of the shock absorber that suppresses fluctuations in the vertical direction of the vehicle body. In an electronically controlled suspension device that outputs the amount of rotation of the electric motor corresponding to the force to the pre-instruction rotation position to the electric motor and performs open loop control, the pre-instruction rotation position corresponds to the upper limit or lower limit of the rotation range. If it is, the additional rotation amount is added to the rotation amount rotating to the pre-instruction rotation position, and the resultant is output to the electric motor.

  It is possible to provide an electronically controlled suspension device and a step-out correction method that can minimize the uncomfortable feeling of riding comfort felt by the occupant during step-out cancellation and that complete step-out cancellation in a short time.

The best mode for carrying out the present invention will be described below with reference to the drawings.
Whether or not the electronically controlled suspension apparatus 100 of the present embodiment is out of step when the command value of the damping force reaches a predetermined value without particularly determining whether or not it is in a step out state (may be determined). Regardless of the step, the step-out elimination operation is executed (hereinafter referred to as initialization). Hereinafter, the control value of the damping force indicated by the suspension ECU 14 (electronic control unit) is referred to as a command stage, and the actual control position (rotational position) of the step motor 15 is referred to as an actual control stage.

  Specifically, when the command stage is the lowest stage or the highest stage, the step motor 15 is instructed to rotate more than the step motor 15 is rotated to the lowest stage or the highest stage. By this initialization, the actual control stage always matches the lowest or highest stage regardless of whether or not it has stepped out until then, so that the command stage and the actual control stage match, and the step-out is eliminated. .

  When the command stage is the lowest stage or the highest stage, it may be considered that the actual control stage is also in a state that is coincident with or close to the lowest stage or the highest stage, so that a change in riding comfort due to initialization can be suppressed to a minimum. Further, since the actual control stage is close to the lowest stage or the highest stage and the lowest stage or the highest stage becomes the command stage, the initialization can be completed in a very short time.

  FIG. 1 shows an example of a block diagram of an electronically controlled suspension device 100. The damping force of the shock absorber 20 is controlled by the suspension ECU 14, and the ECU includes a sprung acceleration sensor 11, a relative displacement sensor 12, a vehicle speed sensor 13, and the like via an in-vehicle LAN such as a CAN (Controller Area Network) or a dedicated line. A step motor 15 is connected. Further, the right side of the figure schematically shows the dynamic structure of the wheel 19 as an unsprung member and the vehicle body 16 as an unsprung member, and the damper 18 and the spring 17 represent the shock absorber 20.

  The suspension ECU 14 is a computer having a CPU, ROM, RAM, NVRAM, input / output interface, ASIC (Application Specific Integrated Circuit), and the like. For example, the ROM stores in advance a program for initializing the step-out, and the RAM stores the command stage instructed immediately before.

  The suspension ECU 14 includes a damping force calculation unit 41, a command stage determination unit 42, a determination unit 43, and a rotation amount addition unit 44 that are realized by a hardware circuit such as an ASIC or a CPU executing a program.

  The damping force calculation unit 41 of the suspension ECU 14 calculates the damping force from the vertical acceleration of the vehicle body 16 and the relative speed between the vehicle body 16 and the wheels 19 based on, for example, the skyhook theory. The sprung acceleration sensor 11 is provided for each wheel 19 and detects the acceleration in the vertical direction of the vehicle body 16. The relative displacement sensor 12 is a sensor that detects the amount of relative displacement between the vehicle body 16 and the wheel 19 for each wheel 19, for example, the amount of extension of the spring 17. The vehicle speed sensor 13 is a sensor that detects the rotational speed of each wheel and then outputs the vehicle speed of the vehicle.

  The output value of the sprung acceleration sensor 11 is integrated by an integration circuit so that the vertical speed Vz of the vehicle body 16 can be detected, and the output value of the relative displacement sensor 12 is differentiated by a differentiation circuit. The relative speed V of the wheel 19 is obtained.

  Briefly explain Skyhook theory. FIG. 2 is an example of a diagram schematically illustrating a dynamic model of the shock absorber 20 to which the skyhook theory is applied. It is assumed that the skyhook damper 18 'fixed in the air is virtually generated and a virtual damping force is generated by the skyhook damper 18'.

If the relative speed of the sprung member (vehicle body 16) and the unsprung member (wheel 19) is V and the relative displacement amount is L, the equation of motion of the vehicle body 16 in the actual dynamic model of FIG. Can do. Where m is the mass of the vehicle body 16, a is the acceleration in the vertical direction of the vehicle body 16, C is a damping coefficient by the damper 18, and f is the spring constant of the spring 17.
m.a = -C.Vf.L
On the other hand, in the shock absorber 20 provided with the virtual skyhook damper 18 ′ shown in FIG. 2, the equation of motion of the vehicle body 16 can be expressed by the following equation. Here, Cs is an attenuation coefficient of the virtual skyhook damper 18 ′.
m · a = −Cs · V _Z −f · L
From both formulas,
C = −Cs · Vz / V = −Cs · Vz / (Vz−Vx)
It becomes. Vx is the speed of the wheel 19 in the vertical direction.

Therefore, by appropriately determining the damping coefficient Cs of the shock absorber 20 that is skyhooked, it is equivalent to controlling the damping force C by the actual shock absorber 20. The damping force calculation unit 41 has a right side that minimizes the amount of displacement of the skyhooked vehicle body 16 in accordance with the vertical movement state of the vehicle body 16 such as vertical acceleration and the vehicle state such as the turning operation of the vehicle. Is estimated. Then, the vertical velocity V _Z of the vehicle body 16 is detected by the sprung acceleration sensor 11, and the relative velocity (V _Z −V _X ) is detected by the relative displacement sensor 12, and the actual damping force C of the shock absorber 20 is calculated. To do.

  According to the skyhook theory, when the actual damper 18 of FIG. 1 is fixed in a soft state (vibration state), the vertical acceleration of the vehicle body 16 increases in the vicinity of the resonance frequency of the vehicle body 16 of 1 to 2 Hz. When the damper 18 is fixed in the hard state (vibration suppression state), it is possible to reduce the vertical acceleration of the vehicle body 16 from increasing in the rugged feeling region of 4 to 8 Hz.

  FIG. 3 shows an example of a cross-sectional view of the shock absorber 20. The shock absorber 20 is configured such that a piston 27 is slidably fitted to a cylinder 21. The piston 27 divides the oil chamber in the cylinder 21 into a cylinder upper chamber and a cylinder lower chamber, and the flow of hydraulic oil between these chambers is permitted by a narrow flow passage 29 formed in the piston 27 and the like. .

  A rod 22 extends from the piston 27 to a concentric shaft. In the shock absorber 20 of the present embodiment, the damping force changes as the effective flow area of the flow path 29 is changed by the throttle valve 28. The adjustment of the opening degree of the throttle valve 28 is realized by changing the linear motion by the rotational motion of the step motor 15.

  In this embodiment, a spool valve is applied to the throttle valve 28, and the spool valve disposed in the middle of the flow path 29 has a spool 26 slidably fitted to a part of the rod 22 that functions as a housing. It is configured. The spool 26 changes the effective flow path area of the flow path 29 according to the position in the axial direction.

  The spool valve is connected to the axial step motor 15 via the rotary shaft 33. The step motor 15 includes a rotor 24 and a stator 34, and a permanent magnet (not shown) is fixed to the rotor 24, and an electromagnet 25 is fixed to the stator 34. By supplying a pulse signal to the electromagnet 25, the rotor 24 can be rotated by an angle. When the rotor 24 is viewed from above, the rotor 24 moves downward when rotated to the right, and the rotor 24 moves upward when rotated to the left.

  When the rotor 24 rotates, the motion conversion mechanism 23 converts the rotational motion into a linear motion of the spool 26. The motion conversion mechanism 23 indicated by a dotted line is mounted as a ball screw mechanism, and includes a female screw member (not shown) that rotates together with the rotor 24 and a male screw member (not shown) that is screwed to this via a plurality of balls. ) And is configured to convert the rotational motion of the female screw member into the linear motion of the male screw member by supporting the male screw member so as to be slidable in the axial direction in a rotation-prevented state. Therefore, since the spool 26 moves in the axial direction by the rotation of the rotor 24, the effective flow path area of the flow path 29 can be controlled.

  The shock absorber 20 of the present embodiment includes a fixed stopper 31 and a locking member 32 that contacts the fixed stopper 31. FIG. 4 shows an example of a plan view of the fixed stopper 31 and the locking member 32. The fixed stopper 31 has a ring-shaped circumferential portion and a pair of fan-shaped convex portions 31a and 31b extending in a radial direction from the circumferential portion on a plane concentric with the rotating shaft 33.

  The locking member 32 protrudes in the radial direction of the rotary shaft 33 and is fixed. Therefore, the locking member 32 rotates integrally with the rotor 24. The radial length of the locking member 32 is longer than the distance from the tips of the fan-shaped convex portions 31 a and 31 b of the fixed stopper 31 to the surface of the rotary shaft 33.

  The fixed stopper 31 and the locking member 32 determine the minimum rotation position and the maximum rotation position in the rotation direction of the rotor 24 together. When the locking member 32 and the convex portion 31a of the fixed stopper 31 come into contact with each other, the rotor 24 stops at its minimum rotational position. Similarly, when the rotor 24 rotates from the minimum rotation position and contacts the locking member 32 and the convex portion 31b of the fixed stopper 31, the rotor 24 stops at the maximum rotation position.

  At the minimum rotation position, the spool 26 is in the most open position (upward), so that the damping force of the shock absorber 20 is minimum. When not stepping out, the command stage of the step motor 15 at the minimum rotational position is “1” which is the lowest stage. On the other hand, at the maximum rotational position, the damping force of the shock absorber 20 is maximized because the spool 26 is at the position where the flow path 29 is most narrowed (downward). When not stepping out, the command stage of the step motor 15 at the maximum rotation position is “10” which is the highest stage. That is, the shock absorber 20 can control the damping force in 10 steps.

  The command stage determination unit 42 in FIG. 1 determines a command stage corresponding to the damping force within a range of 1 to 10. When the rotation amount is instructed to the step motor 15 based on the command steps 1 to 10, the step motor 15 rotates the rotor 24 by the commanded rotation amount. However, if the hydraulic oil exhibits a large rotational resistance with respect to the rotation of the rotor 24, such as when the viscosity of the hydraulic oil is high or when the flow speed of the hydraulic oil passing through the flow path 29 is high, the command stage and the actual control stage match. Do not step out. In the open control, the actual control stage is not fed back, and the rotation amount of the difference from the immediately preceding command stage to the target command stage is instructed.

  FIG. 5A is a diagram schematically illustrating the step-out state. In the figure, time [second] is shown on the horizontal axis, and the command stage (dotted line) and the actual control stage (solid line) are shown on the vertical axis. The command stage and the actual control stage coincide with each other until time T1. When the suspension ECU 14 controls the step motor 15 by open control, it is unclear whether the command stage and the actual control stage match, but the vehicle state estimated in the damping force calculation process and sensor detection Step out can also be estimated from the value.

  And when step-out occurs at time T1, the state is continued. In the figure, since the actual control stage is larger than the command stage, the actual damping force is higher than the calculated optimum damping force. That is, the state where riding comfort deteriorates continues.

  Therefore, the electronically controlled suspension apparatus 100 of this embodiment instructs the step motor 15 to rotate the rotation amount so that the rotor 24 rotates more than when it reaches the minimum rotation position when the command stage is the lowest stage. Similarly, when the command stage is the highest stage, the rotation amount is instructed to the step motor 15 so that the rotor 24 rotates more than reaching the maximum rotational position. In other words, when the command stage is the lowest stage, the step motor 15 is rotated by adding a predetermined rotation angle to the rotation angle of the difference between the immediately preceding command stage and the lowest stage, and when the command stage is the highest stage, The step motor 15 is rotated by adding a predetermined rotation angle to the difference rotation angle between the command stage and the highest stage.

  FIG. 5B is an example of a diagram for schematically explaining the elimination of the step-out state. Similar to FIG. 5A, the step-out occurs at time T1. Thereafter, the state in which the command stage and the actual control stage are different continues until time T2, but the command stage becomes the lowest stage at time T2. The determination unit 43 in FIG. 1 detects this, and the rotation amount addition unit 44 adds a rotation amount that instructs the step motor 15 so that the rotor 24 rotates more than reaching the minimum rotation position. For example, when the command stage at time T2 is 3 and the actual control stage is 6, conventionally, a rotation instruction for “3-1 = 2” stages is requested to the rotor 24, but FIG. In this case, the actual control stage reaches only “6-2 = 4” stage as shown in FIG.

  The suspension ECU 14 of the present embodiment requests the step motor 15 to give a rotation instruction of “3-1 = 2” steps + additional step number α when the command step is 3 and the lowest step is the command step.

  The additional stage number α may be greater than or equal to the “difference between the actual control stage and the command stage”, but since the actual control stage is unknown, the “maximum value of the difference between the actual control stage and the command stage” that can occur out of step. It becomes. Therefore, when there are 10 command stages, the step-out can be eliminated by setting the number of additional stages α to “10-1 = 9”, no matter how much the actual control stage and the command stage are deviated.

An excessive number of additional steps may generate heat or generate a loud contact sound because the rotational force is applied even after the locking member 32 and the fixed stopper 31 contact each other. Therefore, the additional stage number α may be determined by a function of an elapsed time from the last initialization of the command stage. The longer the elapsed time, the greater the possibility of step-out and the greater the difference between the actual control stage and the command stage. Therefore, the additional stage number α is determined so as to increase in proportion to the time.
The number of additional stages α = c · t c: constant coefficient t: time Also, as the number of changes in the command stage increases, the possibility of step-out and the difference between the actual control stage and the command stage increase. Then, the additional stage number α may be determined so as to increase in proportion to the number of times the command stage is changed.
Number of additional stages α = d · nd d: constant coefficient n: number of changes Also, the step-out may depend on the viscosity of the hydraulic oil or the flow velocity of the flow path 29 as described above. It may be a function of the viscosity and the change stage at one time.
Additional stage number α = c (viscosity) · t
Additional stage number α = d (changed once) ・ n
c (viscosity) indicates that c is a function of viscosity, and d (one change stage) indicates that d is a function of one change stage.

  FIG. 6 is an example of a flowchart showing a procedure for the suspension ECU 14 to initialize the step-out. The flowchart shown in FIG. 6 starts when the ignition is turned on, and is thereafter repeatedly executed at predetermined cycle times.

  First, the damping force calculation unit 41 reads the sprung acceleration from the sprung acceleration sensor 11 and the relative displacement amount of the vehicle body 16 and the wheel 19 from the relative displacement sensor 12 (S10). And the damping force calculation part 41 estimates the state of the vehicle body 16 using these detected values, the differential value and integral value of a detected value, and the damping force of a command stage (S20).

  Then, the damping force calculation unit 41 calculates a preferable damping coefficient Cs from the estimated state of the vehicle body 16 by using, for example, the Skyhook theory, and calculates the actual velocity from the vertical speed Vz and the relative displacement speed V of the vehicle body 16. The damping force (damping coefficient C) of the shock absorber 20 is determined (S30). The command stage determination unit 42 determines a command stage corresponding to this damping force.

  Next, the determination unit 43 determines whether the command stage is the lowest stage “1” or the highest stage “10” (S40). When it is neither the lowest stage nor the highest stage (No in S40), the determined command stage becomes the command stage as it is (S50). The suspension ECU 14 calculates the rotation amount (rotation angle) of the step motor 15 according to the difference from the immediately preceding command stage to the target command stage (S70).

  On the other hand, when the command stage is the lowest stage or the highest stage (Yes in S40), the rotation amount adding unit 44 adds the additional stage number α to the difference between the current command stage and the lowest or highest stage (S60).

  Then, the suspension ECU 14 calculates the rotation amount (rotation angle) of the step motor 15 according to the number of steps obtained by adding the additional step number α to the difference from the current command step to the lowest step or the highest step (S70). Thereby, it is possible to instruct the step motor 15 of a control signal that rotates from the current rotational position to the minimum rotational position or to a larger rotational position than the maximum rotational position.

  Since the suspension ECU 14 instructs the rotation amount of the step motor 15 calculated in step S70 to the step motor 15 (S80), the step motor 15 rotates (S90), and the damping force can be changed (S100).

  As described above, the electronically controlled suspension device 100 according to the present embodiment minimizes a change in ride comfort due to initialization by initializing step-out when the command stage is the lowest or highest stage, and The initialization can be completed in a very short time. In addition, almost no additional hardware is required, and the addition of logic on the software can be minimized, thereby suppressing an increase in cost.

It is an example of the block diagram of an electronically controlled suspension apparatus. It is an example of the figure which illustrates typically the dynamic model of the shock absorber to which skyhook theory is applied. It is an example of sectional drawing of a shock absorber. It is an example of the top view of a fixed stopper and a locking member. FIG. 3 is an example of a diagram that schematically illustrates a step-out state and a diagram that schematically illustrates cancellation of the step-out state. It is an example of the flowchart figure which shows the procedure in which suspension ECU initializes a step-out.

Explanation of symbols

11 Sprung acceleration sensor 14 Suspension ECU
15 Step motor 16 Car body (spring member)
19 Wheel (Unsprung member)
20 Shock absorber 22 Rod 24 Rotor 27 Piston 28 Throttle valve 31 Fixed stopper 32 Locking member 100 Electronically controlled suspension device

Claims (3)

A shock absorber in which two chambers communicate with each other by a flow path;
A throttle valve that adjusts the effective flow path area of the flow path;
An electric motor for driving the throttle valve;
A pair of rotation restricting means for restricting the rotation range of the electric motor;
A sensor for detecting the vertical movement state of the vehicle body;
Damping force calculation means for calculating the damping force of the shock absorber that suppresses fluctuations in the vertical direction of the vehicle body,
In the electronically controlled suspension device that outputs the rotation amount to the pre-instruction rotation position of the electric motor corresponding to the damping force to the electric motor and performs open loop control,
When the pre-instruction rotation position corresponds to the upper limit or the lower limit of the rotation range, an additional rotation amount is added to the rotation amount that rotates to the pre-instruction rotation position and is output to the electric motor.
An electronically controlled suspension device. The amount of additional rotation is
More than the rotation amount corresponding to the deviation between the pre-instruction rotation position caused by the step-out and the actual rotation position,
The electronically controlled suspension device according to claim 1. A shock absorber in which two chambers communicate with each other by a flow path;
A throttle valve that adjusts the effective flow path area of the flow path;
An electric motor for driving the throttle valve;
A pair of rotation restricting means for restricting the rotation range of the electric motor;
A sensor for detecting the vertical movement state of the vehicle body;
Damping force calculation means for calculating the damping force of the shock absorber that suppresses fluctuations in the vertical direction of the vehicle body,
In the step-out correction method for the electronically controlled suspension device that outputs to the electric motor a rotation amount to the pre-instruction rotation position of the electric motor corresponding to the damping force, and performs open loop control.
When the pre-instruction rotation position corresponds to the upper limit or the lower limit of the rotation range, an additional rotation amount is added to the rotation amount that rotates to the pre-instruction rotation position and is output to the electric motor.
A step-out correction method for an electronically controlled suspension device.

Images