JP3692650B2 - Vehicle height adjustment device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle height adjustment device that adjusts vehicle height by supplying and discharging a working fluid to and from a cylinder device.
[0002]
[Prior art]
In the vehicle height adjusting device that adjusts the vehicle height so that the actual vehicle height becomes the target vehicle height, basically, the cylinder in the cylinder device is connected to either the sprung weight or the unsprung weight. The piston rod of the cylinder device is connected to the other of the sprung weight and the unsprung weight. The vehicle height is raised by supplying the working fluid to the cylinder, and the vehicle height is lowered by discharging the working fluid from the cylinder.
[0003]
Among such vehicle height adjusting devices, there is a device having a pump driven by an engine separately to obtain a high pressure for supplying a working fluid to a cylinder necessary for raising the vehicle height. However, it is not preferable to equip a separate high-pressure generating pump driven by the engine from the viewpoint of cost, weight, fuel consumption, and the like.
[0004]
In order to adjust the vehicle height without using a pump driven by the engine, the pump function for supplying and discharging the working fluid is obtained by utilizing the expansion and contraction of the cylinder device due to the vehicle height displacement that occurs during traveling. Things have been proposed. That is, as shown in JP-A-7-174181, a pump rod slidably fitted in a piston rod is provided integrally with a cylinder, a pump chamber is defined in the piston rod, and traveling The volume of the pump chamber is changed due to expansion and contraction of the cylinder device inside.
[0005]
In addition to the high-pressure chamber in the cylinder whose volume is changed by the piston rod, a separate low-pressure storage chamber is provided, and the working fluid is sucked from the low-pressure storage chamber to the pump chamber via the suction valve. The fluid is discharged into the high-pressure chamber through the discharge valve to raise the vehicle height. A leveling port for communicating the high-pressure chamber and the low-pressure storage chamber is provided at a position where the vehicle height has risen to a predetermined reference vehicle height, thereby restricting a vehicle height increase above a predetermined level due to the pump action. That is, in the vehicle height adjusting device described above, a constant vehicle height (target vehicle height) determined by the leveling port is obtained.
[0006]
In the above publication, when the actual vehicle height is higher than the reference vehicle height determined by the leveling port (a constant target vehicle height), the high pressure chamber and the low pressure storage chamber are opened and closed in order to quickly reduce the vehicle height. It is disclosed to communicate through a communication pipe with a valve. The publication also discloses an accumulator as a high-pressure source in order to promptly raise the vehicle height when the actual vehicle height is lower than a reference vehicle height (a constant target vehicle height) determined by a leveling port. It is also disclosed to supply a working fluid from a high pressure chamber to a high pressure chamber.
[0007]
[Problems to be solved by the invention]
However, since the pump rod that is slid with respect to the piston rod is separately provided in the above-mentioned publication, the entire cylinder device has a very large sliding resistance, which is not preferable. In particular, in the case of a strut type in which the cylinder device also serves as a suspension arm for setting the posture of the wheel as the suspension, a large bending force acts on the cylinder device, so that it cannot be practically employed.
[0008]
In addition, a pump rod that has a separate pump rod is required to have a very high processing accuracy, and although it is cheaper than a pump driven by an engine, it is considerably expensive. It will end up.
[0009]
Furthermore, the target vehicle height is only a fixed vehicle height determined by the leveling port. In order to change the target vehicle height, it is necessary to replace the cylinder device with a changed leveling port position. Once incorporated in the vehicle, it is virtually impossible to change the target vehicle height, and the degree of freedom for setting the target vehicle height is small.
[0010]
The present invention has been made in consideration of the above circumstances, and its purpose is to provide a sliding resistance for the entire cylinder device on the premise of adjusting the vehicle height without using a pump driven by an engine. An object of the present invention is to provide a vehicle height adjusting device that can be set more easily and cheaply without increasing the size.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following configuration. That is,
In a vehicle height adjusting device in which a cylinder in the cylinder device is connected to either one of the sprung weight or the unsprung weight, and the piston rod of the cylinder device is connected to the other of the sprung weight or the unsprung weight.
An accumulator serving as a low-pressure source;
A switchable connection circuit configured in a connection path between the cylinder and the accumulator, the connection state being switchable;
Control means for controlling the switching connection circuit;
Vehicle height detection means for detecting vehicle height;
The switching connection circuit includes at least a first state in which a flow rate flowing from the accumulator to the cylinder is larger than a flow rate flowing from the cylinder to the accumulator, and at least from the cylinder to the accumulator The first state is configured to be switchable between a second state in which the flow rate flowing through the cylinder is greater than the flow rate from the accumulator to the cylinder and a third state in which communication between the cylinder and the accumulator is interrupted. The cylinder device sucks the working fluid from the accumulator by the expansion and contraction of the cylinder device caused by the vehicle height displacement, and the vehicle height is raised, and the cylinder when the second state is established. The pressure is released from the engine to the accumulator and the vehicle height is lowered.
The control means is set to perform switching control of the switchable connection circuit so that the vehicle height detected by the vehicle height detection means becomes a target vehicle height;
The accumulated pressure of the accumulator is set to a small pressure that can guarantee only a vehicle height below the target vehicle height in a state where the accumulator and the cylinder communicate with each other.
It is like that. Preferred embodiments based on the above solution are as described in claims 2 and below in the claims.
[0012]
In the present invention, by setting the switching connection circuit to the first state, the accumulator operates from the accumulator toward the cylinder at a timing when the inside of the cylinder becomes low pressure due to expansion and contraction of the cylinder device during traveling. The fluid is sucked and the vehicle height is raised. By setting the switching connection circuit to the second state, the pressure is released from the cylinder to the accumulator, and the vehicle height is reduced. By setting it as the 3rd state, a cylinder is interrupted | blocked with an accumulator and a vehicle height is maintained.
[0013]
【The invention's effect】
According to the first aspect of the present invention, there is no need to separately provide a pump rod that is slidably fitted into the piston rod. The sliding resistance can be as small as that of the cylinder device.
[0014]
Further, compared with the conventional one having a pump rod, high machining accuracy for the cylinder device itself is not required, and therefore, it can be implemented at a lower cost.
[0015]
Furthermore, the target vehicle height can be arbitrarily set within the range of the minimum vehicle height that can be obtained by the low pressure of the accumulator, while the change of the target vehicle height itself is the setting of the target vehicle height by the control means. It can be done easily and easily with only changes.
[0016]
According to claim 2, a specific structure of the switching connection circuit is provided.
[0017]
According to claim 3, a specific structure of the switching connection circuit is provided. In particular, using a variable orifice provided in the bypass passage is preferable in setting the vehicle height increasing speed and the vehicle height decreasing speed as desired.
[0018]
According to claim 4, a specific structure of the switching connection circuit is provided. In particular, it is possible to obtain the functions of the bypass passage, the one-way valve, and the on-off valve according to claim 2 by using a switching valve that switches between the one-valve state and the communication state, and the switching connection circuit is simplified as much as possible. Preferred above.
[0019]
According to the fifth aspect, the target vehicle height can be changed to a driver's preference using a manual switch.
[0020]
According to the sixth aspect, the vehicle height adjustment during the specific driving state in which the vehicle body is temporarily inclined is suppressed, and the vehicle height adjustment is not necessary or the degree of adjustment when the vehicle body returns to the substantially horizontal state. Can be reduced.
[0021]
According to claims 7 to 10, a specific state of the specific operation state is provided.
[0022]
According to the eleventh aspect, the vehicle height adjustment is suppressed at the time of high vehicle speed, which is preferable in securing the stability of the vehicle.
[0023]
According to the twelfth and thirteenth aspects, the vehicle height control is suppressed at the time of parking or when the vehicle is stopped, so that the driver can be aware of the vehicle height change caused by the change in the loaded load. This is preferable for preventing a change in vehicle height.
[0024]
According to the fourteenth aspect, it is preferable to prevent vehicle height control hunting that frequently repeats vehicle height increase control and vehicle height decrease control within a short period of time.
[0025]
According to the fifteenth aspect, an effect corresponding to the fourteenth aspect can be obtained when traveling on a rough road.
[0026]
According to the sixteenth aspect, the control burden is reduced by prohibiting the vehicle height control, and it is also preferable in reducing the driver's burden of responding to the vehicle height change caused by the vehicle height control.
[0027]
According to the seventeenth aspect, it is possible to easily confirm the convergence state to the target vehicle height.
[0028]
According to the eighteenth aspect, it is preferable to quickly respond to the change in the vehicle height to obtain the target vehicle height.
[0029]
According to the nineteenth aspect, it is preferable to quickly respond to the change in the vehicle height to obtain the target vehicle height.
[0030]
According to the twentieth aspect, the vehicle height caused by fluctuations in the load load compared to the front wheel side while slowly adjusting the vehicle height on the front wheel side, which has a great influence on the steering characteristics, to prevent a sudden change in the steering characteristics. This is preferable in order to quickly set the rear wheel side having a large change width to the target vehicle height.
[0031]
According to the twenty-first aspect, in the cylinder device, in particular, a cylinder device having an inner and outer double cylinder structure as a damper, the damping force generation mechanism using the working fluid supply / discharge between the inner tube and the outer tube is provided. Can be configured externally. Further, by using the first and second damping force generating orifices, a damping force can be obtained in both the expansion side and the contraction side of the cylinder device.
[0032]
According to the twenty-second aspect, in the cylinder device, particularly a cylinder device having an inner / outer double cylinder structure that is generally used as a damper, a damping force generation mechanism that uses the supply and discharge of the working fluid between the inner tube and the outer tube is provided. Can be configured externally. In addition, a damping force can be obtained in both directions on the expansion side and the contraction side of the cylinder device. Furthermore, it is possible to use a variable damping force variable type on the contraction side of the cylinder device by utilizing a change in opening of the variable orifice.
[0033]
According to the twenty-third aspect, on the premise that the shutoff valve is closed at the time of parking, the inner cylinder and the volume compensation chamber are shut off by the lock valve so that the vehicle height change at the time of parking is ensured. Therefore, it is preferable to prevent it. Moreover, even if the lock valve is closed, the second state can be ensured, so that the vehicle height can be lowered by the vehicle height reduction control during parking.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
[0035]
Description of FIG. 1 (First Example of Entire System Diagram)
[0036]
In FIG. 1, reference numeral 1 denotes a cylinder device having a cylinder 2 and a piston rod 3. The cylinder 2 has an inner / outer double structure having an inner cylinder 4 and an outer cylinder 5, and both end openings are closed by a head flange 6 and a bottom flange 7. A piston portion 8 of the piston rod 3 is slidably fitted into the inner cylinder 4, and a rod portion 9 that is integral with the piston portion 8 extends liquid-tightly through the head flange 6 to the outside of the cylinder. ing.
[0037]
The cylinder 2 is connected to the unsprung weight (wheel side member), while the rod portion 9 of the piston rod 3 is connected to the sprung weight (vehicle body side member). Thereby, when the vehicle height is changed, the piston rod 3 is moved up and down relatively with respect to the cylinder 2 and the cylinder device 1 is expanded and contracted. It is also possible to connect the rod 2 to the unsprung weight while connecting the cylinder 2 to the sprung weight.
[0038]
The inner cylinder 4 of the cylinder 2 is filled with working fluid (working oil). The inside of the inner cylinder 2 is divided into two chambers by the piston portion 8, and a chamber in which the rod portion 9 does not exist is indicated by reference numeral 4a, and a chamber in which the rod portion 9 exists is indicated by reference numeral 4b. A space between the inner cylinder 4 and the outer cylinder 5 is a volume compensation chamber 10, and the volume compensation chamber 10 is filled with a working fluid and a gas (usually nitrogen gas). When the cylinder device 1 is expanded and contracted, the volume change of the chamber 4a is larger than the volume change of the chamber 4b by the volume of the rod portion 9 entering and leaving the chamber 4b, and the difference in the volume change will be described later. As described above, the working fluid in the chamber 4 a is compensated by entering and exiting the volume compensation chamber 10.
[0039]
When the working fluid is supplied into the cylinder 2 from the outside, the cylinder device 1 is extended and the vehicle height is raised, and when the working fluid is discharged from the cylinder 2 to the outside, the cylinder device 1 is contracted and the vehicle height is increased. Is reduced (vehicle height adjustment). In the embodiment, the cylinder device 1 as described above is provided for both the left and right front wheels and the left and right rear wheels, and the vehicle height can be adjusted independently for each wheel.
[0040]
Reference numeral 11 denotes an accumulator disposed outside the cylinder device 1. The pressure accumulated in the accumulator 11 is a small pressure, and the accumulator 11 and the cylinder 2 are communicated with each other. Sometimes, the working fluid is supplied from the cylinder 2 side to the accumulator 11 side, and the vehicle height is lowered. More specifically, the pressure is low enough to ensure that the vehicle height can be reduced to the reference vehicle height (in the embodiment, the wheel is in the vertical neutral position) at least when the vehicle is stopped. In other words, the accumulator 11 functions as a reservoir. The accumulator 11 is divided into two chambers 11b and 11c by a free piston 11a serving as a movable partition wall, and one chamber 11b is filled with a working fluid and pressure is applied to the other chamber 11c. Is filled with gas.
[0041]
The accumulator 11 and the chamber 4a in the inner cylinder 4 are connected via a first passage 12, and the first passage 12 is composed of an electromagnetic switching valve in series from the accumulator 11 side in series. A shut-off valve SL, a one-way valve 13 and a damping force generating orifice 14 are connected. On the other hand, the valve 13 allows only the flow from the accumulator 11 side toward the chamber 4a.
[0042]
A second passage 15 extends from the volume compensation chamber 10, and the second passage 15 is connected to the first passage 12 between the shutoff valve SL and the one-way valve 13. An electromagnetic open / close valve 16 is connected to the second passage 15. The first passage 12 and the second passage 15 are connected by a third passage 17. More specifically, one end of the third passage 17 is connected to the first passage 12 between the one valve 13 and the orifice 14, and the other end is closer to the volume compensation chamber 10 side than the on-off valve 16. Two passages 15 are connected.
[0043]
A damping force generating orifice 18 and a one-way valve 19 are connected to the third passage 17 in series with each other. On the other hand, the valve 19 allows only the flow from the first passage 12, that is, the chamber 4 a side toward the second passage 15, that is, the volume compensation chamber 10 side. Such a third passage 17 forms a bypass passage that bypasses the one-way valve 13 and connects the chamber 4a and the shut-off valve SL in cooperation with a part of the second passage 15.
[0044]
In addition to the orifices 14 and 18 as a damping force generation mechanism, a damping force generation mechanism 20 is also provided in the piston portion 8 of the piston rod 3. As is known, this damping force generation mechanism 20 includes a passage communicating the two chambers 4a and 4b in the inner cylinder 4, and in the embodiment, when the cylinder device 1 is extended (the volume of the chamber 4b is reduced). Is set to generate damping force only when
[0045]
In the system diagram of the configuration as described above, the portion surrounded by the alternate long and short dash line in the figure constitutes the switching connection circuit R, and the vehicle height rises according to the switching mode of the shutoff valve SL and the switching valve 16. The vehicle height can be lowered and the vehicle height can be maintained, and each aspect will be described below.
[0046]
(1) Vehicle height maintenance [0047]
When maintaining the vehicle height, the shut-off valve SL is closed and the on-off valve 16 is opened. In this state, the cylinder 2 and the accumulator 11 are shut off, and the working fluid does not pass between the cylinder 2 and the outside. The cylinder device 1 is a normal damper (shock absorber) having no vehicle height adjustment function. B)
[0048]
That is, when the cylinder device 1 is extended so that the volume of the chamber 4 a increases, a damping force is generated by the damping force generation mechanism 20 provided in the piston portion 8. Further, the working fluid from the volume compensation chamber 10 flows toward the chamber 4 a in the inner cylinder 4 through the on-off valve 16, the one-way valve 13 and the orifice 14. When the cylinder device 1 is contracted, the working fluid flows from the chamber 4 a to the volume compensation chamber 10 through the orifice 14, the one-way valve 19, and the orifice 18.
[0049]
As described above, the working fluid flows through the orifice 14 when the cylinder device 1 is extended and contracted, but the working fluid flows through the orifice 18 only when the cylinder device 1 is contracted. That is, the damping force at the time of extension is determined by the damping force generating mechanism 20 provided in the orifice 14 and the piston portion 8, while the damping force at the time of contraction is determined by the orifices 14 and 18.
[0050]
(2) Vehicle height drop [0051]
When the vehicle height is lowered, the shut-off valve SL is opened and the on-off valve 16 is opened. As a result, the working fluid from the chamber 4a is discharged to the low pressure accumulator 11 through the on-off valve 16 and the shutoff valve SL.
[0052]
(3) Vehicle height rise [0053]
The vehicle height is raised using the pumping action of the chamber 4a caused by the expansion and contraction of the cylinder device 1 caused by road surface unevenness during traveling, and therefore the vehicle height cannot be raised when the vehicle is stopped. On the premise that the vehicle is traveling, when the vehicle height rises, the shut-off valve SL is opened and the on-off valve 16 is closed. The one valve 13 is opened at the timing when the pressure in the chamber 4a is lowered by the expansion and contraction of the cylinder device 1, the working fluid in the accumulator 11 is sucked into the chamber 4a, and the vehicle height is increased accordingly. At the timing when the pressure in the chamber 4a increases, the flow of the working fluid from the chamber 4a to the accumulator 11 is restricted by the action of the one-way valve 13, and as a result, the vehicle height increases. The pressure in the chamber 4a is fluctuated due to the displacement of the vehicle height caused by road surface unevenness during traveling, and the pressure in the chamber 4a may be instantaneously lower than the pressure in the accumulator 11, but the pressure in the chamber 4a Since the pressure of the accumulator 11 is lower than the average pressure, the flow of the working fluid toward the accumulator 11 is ensured.
[0054]
(4) Other [0055]
Here, assuming that the vehicle height control is not performed, in the state where both the shut-off valve SL and the on-off valve 16 are opened, the volume of the volume compensation chamber 10 (the chamber 4a) increases by the volume of the accumulator 11, and the suspension The same effect as a softened spring can be obtained (soft). In addition, when only the shut-off valve SL is closed from the above state, the suspension spring becomes hard (hard).
[0056]
Description of FIG. 2 (Second Example of Entire System Diagram)
[0057]
FIG. 2 is a modification of FIG. 1, and the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted (the same applies to FIG. 3 below). In the example of FIG. 2, a variable orifice 31 is provided in place of the on-off valve 16 of FIG. Further, a lock valve 32 made of an electromagnetic on-off valve is connected to the second passage on the volume compensation chamber 10 side of the connection portion of the third passage 17. The lock valve 32 is normally open and is closed only at the time of parking, and restricts the flow of the working fluid between the chamber 4a and the volume compensation chamber 10 to prevent the vehicle height from changing. Further, in the case of FIG. 2, the orifice 14 is not provided as compared with the case of FIG.
[0058]
In the case of FIG. 2, when the vehicle height is maintained, the shut-off valve SL is closed and the opening of the variable orifice 31 is set to the intermediate opening (normal) state.
[0059]
When the vehicle height decreases, the shut-off valve SL is opened and the opening of the variable orifice 31 is increased (substantially zero throttle resistance may be used). By increasing the opening degree of the variable orifice 31, the working fluid from the chamber 4a immediately flows to the accumulator 11, and the vehicle height is quickly lowered.
[0060]
When the vehicle height rises, the shut-off valve SL is opened, and the opening of the variable orifice 31 is reduced (can be completely closed). Note that the opening of the variable orifice 31 should be at least greater when the vehicle height is lower than when the vehicle height is increased.
[0061]
Description of FIG. 3 (Third Example of Overall System Diagram)
[0062]
FIG. 3 shows still another modification of FIG. In this example, the passage between the chamber 4a and the shut-off valve SL is only the first passage 12. The first passage 12 is provided with an electromagnetic switching valve 35 in series in addition to the shutoff valve SL. The switching valve 35 switches between a one-valve state that allows only a flow toward the chamber 4a and a communication state. That is, in the case of FIG. 3, the switching valve 35 has the functions of the bypass passage configured using the second passage 15 and the third passage 17 in FIG. Become.
[0063]
In FIG. 3, a damping force generation mechanism 36 including a communication path that communicates the chamber 4a and the volume compensation chamber 10 is provided in the cylinder 1 (the flow of the working fluid for generating the damping force is the cylinder). 2 only).
[0064]
When the vehicle height is maintained, the shut-off valve SL is closed (the switching mode of the switching valve 35 can be either a one-valve state or a communication state). When the vehicle height is lowered, the shut-off valve SL is opened and the switching valve 35 is in a communicating state. When the vehicle height rises, the shut-off valve SL is opened and the switching valve 35 is in a one-way state.
[0065]
1 to 3, a symbol U is a control unit configured by using a microcomputer as a control means. The control unit U receives signals from sensors or switches S1 to S3. The sensor S1 detects vehicle height and constitutes vehicle height detection means. The vehicle height sensor S1 is provided independently for the left and right front wheels. For the left and right rear wheels, the vehicle height sensor S1 detects the vehicle height at the intermediate position in the vehicle width direction of the stabilizer that connects the left and right rear wheels. (The average vehicle height of the left and right rear wheels is detected by one vehicle height sensor).
[0066]
The switch S2 is manually operated to input a target vehicle height. In the embodiment, either the high (high vehicle height) or the low (low vehicle height) is input. The height is set as the vehicle height corresponding to the reference vehicle height. S3 represents a sensor group including a plurality of sensors or switches. The sensor group S3 includes, for example, a vehicle speed sensor, a steering wheel angle sensor, an ignition switch, a parameter, and the like in order to detect parameters necessary for control described later. -It includes a king brake switch, an accelerator opening sensor, an idle switch, and the like.
[0067]
In the case of FIG. 1, the control unit U controls the cutoff valve SL and the on-off valve 16. In the case of FIG. 2, the cutoff valve SL, the variable orifice 31 and the on-off valve 32 are controlled. Further, in the case of FIG. 3, the cutoff valve SL and the switching valve 35 are controlled.
[0068]
Explanation of FIG. 5 and FIG. 6 (flow chart)
[0069]
Next, taking the case of FIG. 2 as an example, an example of vehicle height control by the control unit U will be described with reference to the flowcharts of FIGS. In the following description, Q indicates a step.
[0070]
First, in Q1 to Q9 in FIG. 5, it is determined whether or not a condition for executing vehicle height control is satisfied. That is, in Q1, it is determined whether or not the vehicle is currently stopped. For example, when the ignition switch is ON (during engine rotation), the vehicle speed is substantially zero, and the accelerator is OFF, it is determined that the vehicle is stopped. If the determination in Q1 is NO, it is determined in Q2 whether or not the vehicle is currently parked. For example, when the ignition switch is OFF and the parking brake is activated, it is determined that the vehicle is parked. If NO in Q2, it is determined in Q3 whether or not the vehicle speed is within a predetermined vehicle speed range, that is, whether or not the vehicle speed is between a first predetermined value and a second predetermined value greater than this. Is done. If YES in Q3, it is determined in Q4 whether the steering angle is a large steering angle greater than or equal to a predetermined value.
[0071]
When the determination in Q5 is NO, it is determined in Q6 whether or not the steering wheel angular velocity (value obtained by differentiating the steering angle) is greater than a predetermined value. If the determination in Q5 is NO, it is determined in Q6 whether or not it is during rapid acceleration based on, for example, the accelerator operation state. If NO in Q6, it is determined in Q7 whether the vehicle is suddenly decelerating based on, for example, the brake pedal operation state.
[0072]
If NO in Q7, it is determined in Q8 whether the vehicle height displacement speed (a value obtained by differentiating the detected value of the vehicle height sensor S1) is greater than a predetermined value. If NO in Q8, it is determined in Q9 whether the road is a rough road. The rough road may be, for example, a sensor that detects the vertical acceleration of the vehicle body provided separately, or based on the vehicle height detected by the vehicle height sensor within a predetermined time. A bad road can be determined when the vehicle height change amount occurs more than a predetermined number of times.
[0073]
If NO in Q9, vehicle height control is executed in Q10 so that the actual vehicle height detected by the vehicle height sensor S1 becomes the target vehicle height set by the switch S2, as will be described later. Is done. Further, when the various vehicle height control execution conditions described above are not satisfied, the routine proceeds to Q11, where the vehicle height control is prohibited (suppressing means, prohibiting means).
[0074]
In the vehicle height control execution conditions described above, Q3 to Q7 in FIG. 5 are for detecting whether the vehicle is traveling straight and in a steady operation state. In other words, the vehicle body is substantially horizontal. It is also for detecting whether or not the specific operation state is inclined from the state. Further, Q3 and Q4 are for detecting whether or not the vehicle is turning suddenly.
[0075]
The contents of Q10 in FIG. 5 are shown in FIG. That is, at Q21, it is determined whether or not the target vehicle height selection switch S2 is switched to the low vehicle height selection. If the determination in Q21 is YES, a control for reducing the vehicle height from the high vehicle height to the low vehicle height is performed. That is, after the shut-off valve SL is opened in Q22, the opening of the variable orifice 31 is increased in Q23.
[0076]
After Q23, at Q24, it is determined whether or not the actual vehicle height has become the low vehicle height as the target vehicle height. In the embodiment, it is assumed that the actual vehicle height has converged to the target vehicle height when the vehicle height is within an error (deviation amount) range of a predetermined vertical width with respect to the target vehicle height for a predetermined time. The determination is made (the same determination method when the vehicle is high). If the determination of Q24 is NO, the determination of Q24 is repeated as it is. If YES in Q24, the shutoff valve SL is closed in Q25, and then the opening of the variable orifice 31 is returned to normal in Q26.
[0077]
If the determination in Q21 is NO, it is determined in Q27 whether or not the vehicle is switched to selection of a high vehicle height. If YES in Q27, the vehicle height is raised from the low vehicle height to the high vehicle height. At this time, after opening the shut-off valve SL in Q28, the opening of the variable orifice 31 is reduced in Q29. Thereafter, in Q30, after waiting for a high vehicle height, the routine proceeds to Q25. When the determination in Q27 is NO, the vehicle height is maintained, and at this time, the process is returned as it is.
[0078]
FIG. 4 is a time chart schematically showing the contents of the vehicle height control described above. In FIG. 4, the time point t1 is when the target vehicle height is switched from high to low. The time point t2 is when the actual vehicle height has converged to the low vehicle height (the time immediately after the actual vehicle height continues within a predetermined error range with respect to the target low vehicle height for a predetermined time TL).
[0079]
The time point t3 is when the target vehicle height is switched from low to high. The time point t4 is when the actual vehicle height has converged to the high vehicle height (the time immediately after the actual vehicle height continues within a predetermined error range with respect to the target high vehicle height for a predetermined time TH).
[0080]
The opening change of the variable orifice 31 may be changed stepwise as shown by the solid line in FIG. 4, but when returning to the normal opening, it is gradually performed as shown by the broken line in FIG. It can also be.
[0081]
Description of FIG. 7
FIG. 7 shows a preferable control example from the viewpoint of steering characteristics when the vehicle height control as described above is performed for both the front wheels and the rear wheels. The vehicle height change speed of the front wheels is determined from the vehicle height change speed of the rear wheels. Also try to make it smaller. As a result, a rapid change in the steering characteristic, particularly an under steering characteristic is ensured, which is preferable in preventing oversteering characteristics.
[0083]
First, in Q31, the vehicle height change speed of the front wheels is calculated as VF, and in Q32, the vehicle height change speed of the rear wheels is calculated as VR. In Q33, it is determined whether or not VF is larger than VR. If YES in Q33, the vehicle height control of the front wheels is interrupted in Q34 (no change in vehicle height). If NO in Q33, the vehicle height control for the front wheels is restored in Q35. In other words, the vehicle height change speed refers to the flow rate of the working fluid between the cylinder 2 and the accumulator 11, and the flow rate on the front wheel side is higher than the flow rate on the rear wheel side. The vehicle height control is performed so as to decrease.
[0084]
Although the embodiments have been described above, the present invention is not limited to this, and includes, for example, the following cases.
[0085]
As the switching type connection circuit R, an appropriately modified circuit can be used. Further, the target vehicle height may be a fixed value of only the reference vehicle height, or may be changed in three or more stages.
[0086]
The cylinder device 1 may be of a type that does not have the outer cylinder 5. In this case, for example, the volume compensation chamber 10 is defined in the chamber 4a via a free piston slidably inserted in the chamber 4a.
[0087]
Although Q11 of FIG. 5 showed the case where vehicle height control is completely prohibited as one aspect | mode of vehicle height control suppression, vehicle height control itself is performed so that the amount of vehicle height change per unit time may become small. Suppressing control (suppressing means) may be performed. In this case, for example, the above suppression control can be obtained by reducing the opening degree by, for example, duty control without completely opening the shut-off valve SL, or, for example, the accumulator 11 Further, an opening switching type control valve may be provided between the valve 12 and the shut-off valve SL, and the opening degree of the passage 12 may be reduced during the suppression control. Such suppression control can also be performed in Q34 of FIG.
[0088]
When the vehicle height change speed is high, or when the vehicle is not traveling straight and steady, the vehicle height maintaining state (the shut-off valve SL is closed) is maintained and the control state of the preceding vehicle height increase or vehicle height decrease is maintained. It may be.
[0089]
When parking, only vehicle height reduction control may be performed. That is, vehicle height reduction control may be performed so that the target vehicle height is reached when the vehicle load greatly decreases and the vehicle load greatly increases due to getting off or loading / unloading during parking.
[0090]
The lock valve 32 shown in FIG. 2 can be similarly provided in FIG. Further, when the vehicle height lowering control is not performed at the time of parking, the arrangement position of the lock valve 32 can be set closer to the chamber 4a than the third passage 17 in the first passage.
[0091]
Each step shown in the flowchart can be expressed by adding the name of the means to the high-level concept expression of the function, and other members also add the name of the means to the high-level concept expression of the function. Can be expressed. Furthermore, the present invention can also be expressed as a control method.
[0092]
The object of the present invention is not limited to what is explicitly stated, but also implicitly includes providing what is substantially preferred or corresponding to what has been described as an advantage.
[Brief description of the drawings]
FIG. 1 shows a first example of an overall system diagram to which the present invention is applied.
FIG. 2 shows a second example of the entire system diagram to which the present invention is applied.
FIG. 3 shows a third example of the entire system diagram to which the present invention is applied.
FIG. 4 is a time chart showing an example of vehicle height control according to the present invention.
FIG. 5 is a flowchart showing an example of vehicle height control according to the present invention.
FIG. 6 is a flowchart showing an example of vehicle height control according to the present invention.
FIG. 7 is a flowchart showing a preferred vehicle height control example for the front wheel side and the rear wheel side.
[Explanation of symbols]
1: cylinder device 2: cylinder 3: piston rod 4: inner cylinder 5: outer cylinder 10: volume compensation chamber 11: accumulator 12: first passage 13: one-way valve 14: orifice 15: second passage 16: on-off valve 17: Third passage 18: Orifice 19: One-way valve 31: Variable orifice 32: Lock valve 35: Switching valve (one-way valve or communication)
SL: Shut-off valve S1: Vehicle height sensor S2: Target vehicle height setting switch U: Control unit R: Switching connection circuit

Claims (23)

In a vehicle height adjusting device in which a cylinder in the cylinder device is connected to either one of the sprung weight or the unsprung weight, and the piston rod of the cylinder device is connected to the other of the sprung weight or the unsprung weight.
An accumulator serving as a low-pressure source;
A switchable connection circuit configured in a connection path between the cylinder and the accumulator, the connection state being switchable;
Control means for controlling the switching connection circuit;
Vehicle height detection means for detecting vehicle height;
The switching connection circuit includes at least a first state in which a flow rate flowing from the accumulator to the cylinder is larger than a flow rate flowing from the cylinder to the accumulator, and at least from the cylinder to the accumulator The flow rate flowing through the cylinder is configured to be switchable between a second state where the flow rate from the accumulator to the cylinder is larger than a second state where the communication between the cylinder and the accumulator is blocked,
When the cylinder state is changed to the first state, the cylinder device sucks the working fluid from the accumulator by the expansion and contraction of the cylinder device, and the vehicle height is raised, and the second state is established. Sometimes the pressure is released from the cylinder to the accumulator to lower the vehicle height,
The control means is set to perform switching control of the switchable connection circuit so that the vehicle height detected by the vehicle height detection means becomes a target vehicle height;
The accumulated pressure of the accumulator is set to a small pressure that can guarantee only a vehicle height below the target vehicle height in a state where the accumulator and the cylinder are in communication.
A vehicle height adjusting device characterized by that. In claim 1,
The switching connection circuit includes a one-way valve that allows only a flow from the accumulator to the cylinder, a bypass passage that bypasses the one valve, and the accumulator side of the one valve and the bypass passage. An open / close shut-off valve disposed and an open / close valve that opens and closes the bypass passage;
The second state is established by opening the shut-off valve and closing the on-off valve,
The second state is achieved by opening both the shut-off valve and the on-off valve,
The third state is established by closing the shutoff valve.
A vehicle height adjusting device characterized by that. In claim 1,
The switching connection circuit includes a one-way valve that allows only a flow from the accumulator to the cylinder, a bypass passage that bypasses the one valve, and the accumulator side of the one valve and the bypass passage. An open / close shut-off valve disposed, and a variable orifice disposed in the bypass passage,
The first state is achieved by opening the shut-off valve and reducing the opening of the variable orifice,
The second state is established by opening the shutoff valve and increasing the opening of the variable orifice.
The third state is established by closing the shutoff valve.
A vehicle height adjusting device characterized by that. In claim 1,
A switching valve that switches between a communication state and a one-valve state that allows only a flow from the accumulator to the cylinder; and an on-off type shut-off valve disposed in series with the switching valve. And
The first state is established by opening the shut-off valve and setting the switching valve to a one-way valve state,
The second state is established by opening the shut-off valve and bringing the switching valve into communication.
The third state is established by closing the shutoff valve.
A vehicle height adjusting device characterized by that. In claim 1,
A vehicle height adjusting device comprising a target vehicle height setting switch for changing the target vehicle height by manual operation. In claim 1,
A vehicle height adjusting device, further comprising a suppression unit that suppresses control by the control unit when the vehicle body is in a specific driving state in which the vehicle body is inclined from a substantially horizontal state. In claim 6,
The vehicle height adjusting device according to claim 1, wherein the specific operation state is a time of sudden acceleration or sudden deceleration. In claim 6,
The vehicle height adjusting device according to claim 1, wherein the specific driving state is a sudden turn. In claim 6,
The vehicle height adjusting device according to claim 1, wherein the specific driving state is set when a steering angle is not less than a predetermined value. In claim 6,
The vehicle height adjusting device according to claim 1, wherein the specific driving state is set when a change speed of a steering wheel steering angle is a predetermined value or more. In claim 1,
A vehicle height adjusting device, further comprising a suppression unit that suppresses the control of the control unit when the vehicle speed is higher than a predetermined vehicle speed. In claim 1,
A vehicle height adjusting device, further comprising suppression means for suppressing control of the control means during parking. In claim 1,
A vehicle height adjusting device, further comprising suppression means for suppressing control of the control means when the vehicle is stopped. In claim 1,
A vehicle height adjusting device, further comprising a suppression unit that suppresses the control of the control unit in a specific driving state in which the vehicle height changes rapidly during traveling. In claim 14,
The vehicle height adjusting device characterized in that the specific driving state is when traveling on a rough road. In any one of Claims 6 thru | or 15,
The suppression means is forcibly set as the third state regardless of the height of the vehicle detected by the vehicle height detection means, and is set to prohibit the vehicle height change by the control of the control means, A vehicle height adjusting device characterized by that. In claim 1,
When the vehicle height detected by the vehicle height detection means is a deviation amount within a predetermined range with respect to the target vehicle height continuously for a predetermined time, it is determined that the vehicle height has converged to the target vehicle height, and the third A vehicle height adjusting device characterized by being in a state. In claim 1,
When the vehicle height change speed is high, the first state or the second state continues without setting the third state even if the vehicle height detected by the vehicle height detecting means converges to the target vehicle height. A vehicle height adjusting device characterized by that. In claim 1,
When the vehicle goes straight and is not in a steady operation state, even if the vehicle height detected by the vehicle height detection means has converged to the target vehicle height, the first state or the second state is not set to the third state. Is a vehicle height adjusting device characterized by that. In claim 1,
The cylinder device is provided for each wheel of the front wheel and the rear wheel, and is set so that vehicle height adjustment is performed independently for each wheel,
During vehicle height adjustment, the flow rate change in the front wheel side cylinder device is set to be smaller than the flow rate change in the rear wheel side cylinder device.
A vehicle height adjusting device characterized by that. In claim 2,
The cylinder has an inner cylinder and an outer cylinder;
The piston rod is slidably inserted into the inner cylinder, and a volume compensation chamber is configured between the inner cylinder and the outer cylinder,
The switchable connection circuit connects the inner cylinder and the shut-off valve, and connects the first passage in which the one valve is disposed, the outer cylinder and the shut-off valve, and the open / close valve is connected. A second passage constituting a part of the bypass passage, and a first passage constituting the part of the bypass passage by connecting the first passage and the second passage closer to the cylinder side than the one valve and the on-off valve. 3 passages,
In the third passage, a second one valve that allows only a flow from the first passage toward the second passage and a first orifice for generating a damping force are arranged in series with each other,
A second orifice for generating a damping force is disposed on the inner cylinder side of the first passage relative to the third passage;
The on-off valve is opened in the third state;
A vehicle height adjusting device characterized by that. In Claim 3, the cylinder has an inner cylinder and an outer cylinder,
The piston rod is slidably inserted into the inner cylinder, and a volume compensation chamber is configured between the inner cylinder and the outer cylinder,
The switchable connection circuit connects the inner cylinder and the shut-off valve, and connects the first passage in which the one valve is disposed, the outer cylinder and the shut-off valve, and the variable orifice is connected. A second passage constituting a part of the bypass passage, and a first passage constituting the part of the bypass passage by connecting the first passage and the second passage closer to the cylinder than the one valve and the variable orifice. 3 passages,
In the third passage, a second one-valve that allows only a flow from the first passage toward the second passage and a damping force generating orifice are arranged in series with each other,
A vehicle height adjusting device characterized by that. In claim 22,
A lock valve that is closed during parking is connected to the second passage on the volume compensation chamber side than the third passage.
A vehicle height adjusting device characterized by that.

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