JP2009160956A - Suspension device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a suspension device capable of adjusting the height of a vehicle, having adjustable damping characteristics, and manufacturable at low cost. <P>SOLUTION: This suspension device S includes a gas spring A interposed between a vehicle body and an axle and elastically supporting the vehicle body, a pneumatic shock absorber D interposed between the vehicle body and the axle parallel to the gas spring A and damping the relative movement of the vehicle body to the axle, and a supply/discharge means C for supplying and discharging a gas into and from the gas spring A and the pneumatic shock absorber D. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a suspension device.

  Conventionally, as a suspension device, a gas spring that is interposed between a vehicle body and an axle and elastically supports the vehicle body, and a relative vibration between the vehicle body and the axle that is interposed between the vehicle body and the axle in parallel with the gas spring. There is known a structure including a hydraulic shock absorber that attenuates (see, for example, Patent Document 1).

  In such a suspension device, since the suspension spring is a gas spring, the vehicle height can be adjusted by adjusting the pressure in the gas spring. Therefore, gas is supplied to and discharged from the gas spring. There may be a pneumatic circuit capable of this.

  The pneumatic circuit includes, for example, a compressor that supplies compressed gas to the gas spring, and a low-pressure tank that accumulates pressure using the gas exhausted from the gas spring. When supplying, it is known that intake of air from a low-pressure tank preferentially reduces energy consumption (see, for example, Patent Document 2).

In turn, as for shock absorbers, hydraulic shock absorbers that use working fluid as working oil are currently the mainstream, but in recent years, even if working fluid is used as a gas, the sliding portion between the rod and the seal member is lubricated and good. Pneumatic shock absorbers have been developed that can withstand suspension applications where vibration input is frequently performed between the vehicle body and axle by ensuring slidability. It has become possible to use it (see, for example, Patent Document 3).
JP 2004-332747 A Japanese Patent Laid-Open No. 2002-87040 JP 2006-349138 A

  Here, the shock absorber and the gas spring are devices that are independent of each other and have different functions. What is required of the shock absorber is generation of damping force, and what is required of the gas spring is elastic support of the vehicle body.

  With further improvements in ride comfort and vehicle body posture control in mind, the damping characteristics are adjusted for the shock absorber and the vehicle height is adjusted for the gas spring because of the difference in function between the shock absorber and the gas spring. Will be required.

  Then, it is necessary to adopt a configuration in which the damping characteristic can be changed for the shock absorber, and even in the case of a pneumatic shock absorber, it is expensive to use such a configuration, and the vehicle pressure is adjusted by adjusting the internal pressure of the gas spring. Since it is necessary to mount a pneumatic circuit for high adjustment, the entire system of the suspension apparatus becomes very expensive.

  Accordingly, the present invention has been developed to solve the above-described problems, and an object of the present invention is to provide an inexpensive suspension device that can adjust the vehicle height and the damping characteristics. That is.

  In order to achieve the above-described object, the suspension device in the problem solving means of the present invention includes a gas spring that is interposed between the vehicle body and the axle and elastically supports the vehicle body, and is parallel to the gas spring between the vehicle body and the axle. And an air pressure buffer that attenuates relative vibration between the vehicle body and the axle, and a gas spring and an air supply / discharge unit that supplies and discharges gas to and from the air pressure buffer.

  In the suspension device of the present invention, since the pressure of the gas spring and the pneumatic shock absorber can be adjusted by providing the supply / discharge means, the vehicle height can be adjusted and the damping characteristic of the pneumatic shock absorber can be adjusted. Can be adjusted.

  In other words, the suspension device can adjust the pressure in the pneumatic shock absorber by the supply / discharge means that should be provided to the gas spring for vehicle height adjustment, so that it does not require a separate damping characteristic adjustment mechanism. The damping characteristics of the pressure shock absorber can be adjusted, and the supply and discharge means are shared by the gas spring and the pneumatic shock absorber, so there is no need to provide a separate supply and discharge means dedicated to the pneumatic shock absorber. The device is very cheap.

  In addition, the pressure of the gas spring and the pneumatic shock absorber can be adjusted, and the weight of the vehicle body can be shared by the gas spring and the pneumatic shock absorber to support the vehicle body. By adjusting the weight ratio of the vehicle body supported by the vehicle, the vehicle height can be adjusted as desired while the damping characteristic of the pneumatic shock absorber is optimally set for the vehicle. Therefore, both ride comfort and vehicle height adjustment in the vehicle can be achieved.

  FIG. 1 is a view showing a pneumatic shock absorber according to an embodiment of the present invention. FIG. 2 is a graph showing the relationship between the vehicle height, the pressure of the gas spring, and the pressure of the pneumatic shock absorber. FIG. 3 is a view showing a suspension device according to a modification of the embodiment of the present invention. FIG. 4 is a diagram showing a suspension device in another modification of the embodiment of the present invention.

  Hereinafter, the suspension device S of the present invention will be described based on the embodiment shown in the drawings. As shown in FIG. 1, a suspension device S according to an embodiment includes a gas spring A that is interposed between a vehicle body and an axle (not shown) and elastically supports the vehicle body, and a gas spring A between the vehicle body and the axle. And a pneumatic shock absorber D for damping relative vibration between the vehicle body and the axle, and a gas spring A and a supply / discharge means C for supplying / exhausting gas to / from the pneumatic shock absorber D. Yes.

  The pneumatic shock absorber D includes a cylinder 1 filled with gas, a piston 2 slidably inserted into the cylinder 1, and a rod connected to the piston 2 and movably inserted into the cylinder 1. 3, and the piston 2 includes a passage 4 that communicates the upper chamber r1 and the lower chamber r2 defined in the cylinder 1, and the passage 4 is a gas that moves between the upper chamber r1 and the lower chamber r2. It is designed to provide resistance to the flow.

  That is, in the pneumatic shock absorber D, the piston 2 moves upward or downward in FIG. 1 with respect to the cylinder 1 and expands from one of the upper chamber r1 and the lower chamber r2 in which the gas is compressed. When moving to the other of the upper chamber r1 or the lower chamber r2, the gas flow is given resistance in the passage 4 to generate a damping force that attenuates the relative vibration between the vehicle body and the axle.

  In the case of this embodiment, the rod 3 is connected to the vehicle body of the vehicle, and the cylinder 1 is connected to the axle. In the case of this pneumatic shock absorber D, it is set as an upright shock absorber. .

  Further, in this case, the pneumatic shock absorber D is interposed between the four wheels of the vehicle and the vehicle body in parallel with the gas spring A, and gas is supplied into the cylinder 1 by the supply / discharge means C. By supplying the pressure, the pressure in the cylinder 1 can be increased, and the pressure in the cylinder 1 can be decreased by exhausting the gas from the cylinder 1. In FIG. 1, since the drawing is complicated, one gas spring A and one pneumatic shock absorber D are shown, and the other three are not shown.

  By adjusting the pressure in the cylinder 1 in this way, the pressure receiving area difference of the piston 2 (the area facing the upper chamber r1 is subtracted from the pressure receiving area difference of the piston 2 from the area facing the lower chamber r2 of the piston 2). The vehicle height can be adjusted by adjusting the force (hereinafter referred to as “rod reaction force”) that extends the pneumatic shock absorber D multiplied by the area difference obtained in the above.

  Furthermore, the gas spring A includes a bottomed cylindrical chamber 5 connected to the rod 3, and a cylindrical diaphragm 6 connected to the opening of the chamber 5 and the side of the cylinder 1 of the pneumatic shock absorber D. A gas chamber G formed around the outer periphery of the pneumatic shock absorber D is provided, and functions as a suspension spring that supports the weight of the vehicle body. Accordingly, when the pressure in the gas chamber G in the gas spring A is increased by expanding the volume of the gas chamber G by supplying gas from the supply / discharge means C, the vehicle body can be raised. When the gas in the gas chamber G is exhausted to the outside of the suspension device through the discharge means C and the volume of the gas chamber G is reduced, the vehicle body can be lowered, that is, the gas spring G in the gas spring A is supplied by the supply / discharge means C. The vehicle height can be adjusted by controlling the volume of the vehicle.

  Further, when the vehicle height changes due to passengers or cargo, the vehicle height can be kept constant by controlling the pressure in the air chamber G with respect to the weight change.

  In the suspension device S shown in FIG. 1, the gas spring A and the pneumatic shock absorber D are integrated, but the gas spring A and the pneumatic shock absorber D may be installed independently of each other. .

  The supply / discharge means C in the embodiment supplies / discharges gas to / from the four gas springs A and the pneumatic shock absorber D interposed between the four wheels and the vehicle body of the vehicle. The gas spring A and the pneumatic shock absorber D cooperate with each other to form a suspension device.

  Subsequently, the supply / discharge means C supplies gas from the compressor 7, the supply line 8 connecting the discharge side 7 a of the compressor 7, the gas spring A, and the pneumatic buffer D, and the gas spring A and the pneumatic buffer D. An exhaust line 9 that opens to the atmosphere, a spring-side on-off valve 10 that communicates and blocks the supply line 8 and the gas spring A, and a buffer-side on-off valve 11 that communicates and blocks the supply line 8 and the pneumatic buffer D And an exhaust valve 12 provided in the middle of the exhaust line 9 for opening and closing the exhaust line 9.

  Hereinafter, the supply / discharge means C will be described in detail. When driven by the motor M, the compressor 7 sucks gas from the suction port 7b and compresses the gas sucked from the atmosphere side through the discharge port 7a to the supply line 8. It is designed to send out. In addition to driving by the motor M, the compressor 7 can be driven by taking out power from an engine mounted on the vehicle. Further, when the vehicle is provided with a hydraulic pump, the motor M can be driven. A hydraulic motor may be used instead of an electric motor.

  Further, in the case of this embodiment, the compressor 7 sucks air from the suction port 7b and supplies it to the cylinder C. Therefore, an air filter 13 is provided upstream of the suction port 7b, and a gas spring A or pneumatic buffer is provided. Dust and dust are prevented from entering the container D.

  The supply line 8 has one end connected to the discharge side 7a of the compressor 7 and the other end connected to a spring passage 14 communicating with the gas spring A and a buffer passage 15 communicating with the pneumatic buffer D. The compressor 7, the gas spring A, and the pneumatic shock absorber D are communicated with each other.

  In this case, four spring passages 14 and four shock absorber passages 15 are provided so that gas can be supplied to each gas spring A and each pneumatic shock absorber D arranged in each wheel. The shock absorber channel 15 is connected to the upper end of the hollow rod 3 connected to the vehicle body side, and communicates with the cylinder 1 through the inside of the rod 3.

  In this way, the supply line 8 is connected to the upper end of the rod 3 so as to communicate with the cylinder 1 via the inside of the rod 3, so that each part of the supply / discharge means C including the supply line 8 is connected to the inside of the vehicle body. The components of the supply / discharge means C including the supply line 8 can be protected, and there is an advantage that the handling of the supply line 8 is not complicated.

  In the middle of the supply line 8, in order from the upstream on the discharge side of the compressor 7, a dryer 16 for drying the gas sent out from the compressor 7, a throttle 17 that provides resistance to the flow of the gas, and a throttle 17 are arranged in parallel. The check valves 18 that allow only the flow from the upstream side to the downstream side are arranged and provided.

  In this case, the dryer 16 employs an adsorption type, and contains therein a desiccant that adsorbs moisture such as silica gel and activated alumina, and adsorbs moisture of the compressed gas passing through the interior with the desiccant. Thus, the compressed gas can be dried.

  Further, the check valve 18 arranged downstream of the dryer 16 and in parallel with the throttle 17 positively allows the passage of gas in preference to the throttle 17 when the compressor 7 supplies compressed gas, It is provided so as not to cause energy loss due to the throttle 17 when compressed gas is supplied.

  Further, in the case of this embodiment, when the gas is exhausted from the gas spring A and the pneumatic buffer D to release the gas to the atmosphere, it is connected between the compressor 7 and the dryer 16 in the middle of the supply line 8. A configuration in which exhaust is performed through the exhaust line 9 is adopted so that the dryer 16 passes through the dry gas filled in the gas chamber G of the gas spring A and the cylinder 1 of the pneumatic shock absorber D.

  The restrictor 17 functions to give a resistance to the gas flow during exhausting and to rapidly depressurize and dry the gas exhausted from the gas spring A and the pneumatic buffer D, and to slowly pass the gas through the dryer 16. Therefore, the dryer 16 can be sufficiently dried.

  Note that drying of the desiccant in the dryer 16 depends on the passage of the dry gas as described above, but a method of heating the desiccant may be adopted separately from this. When the desiccant is dried by heating, and especially when no gas passage is required for drying the dryer 16, the gas spring A and the exhaust line 9 are in the middle of the supply line 8 and downstream of the dryer 16. You may make it connect to the pneumatic buffer D side.

  Subsequently, the spring-side on-off valve 10 is provided in the middle of the spring flow path 14. The spring position 14 a that opens the spring flow path 14 to communicate the compressor 7 and the gas spring A and the spring flow path 14 are provided. There is a shut-off position 10b that closes and cuts off the communication between the compressor 7 and the gas spring A, a spring 10c that is provided at one end and energizes to take the shut-off position 10b, and is provided at the other end and faces the spring 10c. The solenoid 10d is configured as a 2-port 2-position electromagnetic switching on-off valve that switches from the shut-off position 10b to the communication position 10a when the solenoid 10d is excited.

  Further, the shock absorber side opening / closing valve 11 is provided in the middle of the shock absorber flow path 15, a communication position 11 a that opens the shock absorber flow path 15 to communicate the compressor 7 and the pneumatic shock absorber D, and a buffer. A spring 11c that closes the compressor flow path 15 and cuts off the communication between the compressor 7 and the pneumatic shock absorber D, and is provided at one end and urged to take the cut-off position 11b; And a solenoid 11d facing the spring 11c. When the solenoid 11d is excited, the solenoid 11d is configured as a 2-port 2-position electromagnetic switching on-off valve that switches from the shut-off position 11b to the communication position 11a. .

  In addition, the exhaust line 9 is connected between the compressor 7 and the dryer 16 in the middle of the supply line 8 as described above. An electromagnetically switched exhaust valve 12 is provided.

  More specifically, the exhaust valve 12 has a communication position 12a for opening the exhaust line 9 and a shut-off position 12b for shutting off the exhaust line 9, and is provided at one end and urged to take the shut-off position 12b. 12c and a solenoid 12d provided at the other end and opposed to the spring 12c. When the solenoid 12d is excited, the switching position 12b is switched to the communication position 12a. It is configured as a valve.

  A spool valve can be used as the spring-side on-off valve 10, the shock-absorber-side on-off valve 11, and the exhaust valve 12. However, although not shown, an annular valve seat and the valve seat are closed. A poppet valve composed of a conical surface, a spherical surface, and a valve body provided with an elastic body that can seal the axial end of the valve seat is preferably used. It is highly resistant, there is no risk of gas leakage, it is resistant to contamination, and it can enjoy the advantages of excellent response speed.

  When the above-described spring-side on-off valve 10 is switched to the communication position 10 a and the shock-absorber-side on-off valve 11 and the exhaust valve 12 are maintained at the shut-off positions 11 b and 12 b and the compressor 7 is driven, the compression discharged from the compressor 7 Gas is supplied into the gas chamber G of the gas spring A, the pressure in the gas chamber G is increased, and the vehicle height can be increased due to the pressure increase.

  Furthermore, when the compressor 7 is driven while the shock absorber side opening / closing valve 11 is switched to the communication position 11a and the spring side opening / closing valve 10 and the exhaust valve 12 are maintained at the cutoff positions 10b, 12b, the compression discharged from the compressor 7 is performed. The gas is supplied into the cylinder 1 of the pneumatic shock absorber D, the pressure in the cylinder 1 is increased to increase the rod reaction force, and the vehicle height can be increased due to the rod reaction force increase. When the pressure in the cylinder 1 increases, the gas density increases, and the resistance when the gas passes through the passage 4 increases. Therefore, the increase in the pressure in the cylinder 1 attenuates the piston speed in the pneumatic shock absorber D. The power can be increased. That is, the damping characteristic of the pneumatic shock absorber D (the property of the generated damping force with respect to the piston speed of the pneumatic shock absorber) can be changed to harder by the pressure increase in the cylinder 1.

  Further, when the exhaust valve 12 is switched to the communication position 12a and the spring side opening / closing valve 10 or the shock absorber side opening / closing valve 11 or both are switched to the communication positions 10a, 11a, the gas chamber G of the gas spring A or the pneumatic buffering is performed. Gas is exhausted from the cylinder 1 of the compressor D or both, and the pressure in the gas chamber G of the gas spring A and / or the cylinder 1 of the pneumatic shock absorber D is decreased, and the vehicle height is lowered in accordance with the pressure decrease. In particular, when the pressure in the cylinder 1 of the pneumatic shock absorber D is decreased, the damping force with respect to the piston speed in the pneumatic shock absorber D is reduced, that is, the damping characteristic of the pneumatic shock absorber D is further increased. It can be changed to software.

  In addition, the gas spring A and the pneumatic shock absorber D are isolated from the outside by setting the spring side opening / closing valve 10 and the shock absorber side opening / closing valve 11 to the cutoff positions 10b and 11b regardless of the operation of the exhaust valve 12. The gas spring A and the pneumatic buffer D are maintained in a sealed state.

  As described above, in the pneumatic shock absorber D of the present embodiment, the supply / exhaust means C is provided and the pressures of the gas spring A and the pneumatic shock absorber D can be adjusted, so that the vehicle height can be adjusted. At the same time, the damping characteristic of the pneumatic shock absorber D can be adjusted. Therefore, even if the loading / unloading of the luggage or the number of passengers changes and the vehicle height changes, the pressure of the gas spring A and the pneumatic shock absorber D can be controlled to maintain the vehicle height at a predetermined value. A change in vehicle height due to a change in the internal temperature of the shock absorber D can also be suppressed.

  That is, since the pneumatic shock absorber D attenuates vehicle body vibration by converting vibration energy into heat energy during expansion and contraction, the gas temperature in the cylinder 1 rises by repeatedly expanding and contracting due to continuous vehicle body vibration during vehicle travel. Even if the gas weight in the cylinder 1 is constant, the pressure in the cylinder 1 may increase due to the temperature rise of the gas, the rod reaction force may increase, and the vehicle height may be increased. In the suspension device S, the gas can be exhausted from the cylinder 1 of the pneumatic shock absorber D with respect to this temperature rise, and the inside of the cylinder 1 can be decompressed to keep the vehicle height constant. Further, the pressure in the cylinder 1 can be reduced to suppress the increase in the force of the seal member, thereby ensuring good sliding performance of the rod 3 and realizing smooth expansion and contraction, and further suppressing the deterioration of the seal member. it can.

  Therefore, since the suspension device S can adjust the pressure in the pneumatic shock absorber D by the supply / discharge means C to be provided on the gas spring A for vehicle height adjustment, a separate mechanism for adjusting the damping characteristic is required. The damping characteristics of the pneumatic shock absorber D can be adjusted without any change, and the gas spring A and the pneumatic shock absorber D share the supply / discharge means C. Therefore, the suspension device S is very inexpensive.

  Further, the pressure of the gas spring A and the pneumatic shock absorber D can be adjusted, and the weight of the vehicle body can be shared by the gas spring A and the pneumatic shock absorber D to support the vehicle body. By adjusting the weight ratio of the vehicle body supported by the pneumatic shock absorber D, the vehicle height can be adjusted as desired while optimally setting the damping characteristic of the pneumatic shock absorber D to the vehicle. Therefore, both ride comfort and vehicle height adjustment in the vehicle can be achieved.

  Furthermore, since it is not necessary to set the pneumatic shock absorber D to a double rod type, there is no concern that it is difficult to ensure the stroke length required by the vehicle at the expense of the stroke length of the pneumatic shock absorber D.

  In the case of the present embodiment, the spring-side on-off valve 10 and the shock-absorber-side on-off valve 11 close the flow paths 14 and 15 and open the lines 14 and 15 by energization when not energized. Since it is set, the gas spring A and the pneumatic shock absorber D can be maintained in a sealed state even in the unlikely event that the system in the supply / exhaust means C cannot be energized. It is possible to prevent changes in the vehicle height and damping characteristics of the vehicle, and to reliably shift to the fail-safe mode.

  In the supply / discharge means C of the above-described embodiment, the compressor 7 is driven when the gas is supplied to the gas spring A and the pneumatic buffer D, but an accumulator is installed in the middle of the supply line 9, The accumulator may be accumulated and gas may be supplied from the accumulator to the gas spring A and the pneumatic buffer D. Further, the gas exhausted from the gas spring A and the pneumatic shock absorber D is stored in an accumulator different from the one described above, and the compressor 7 sucks the gas from the accumulator side in preference to the atmosphere, and compresses the gas. You may employ | adopt the structure which makes a rate low and energy consumption become small.

  As described above, the suspension device S provided with the supply / discharge means C can realize the vehicle height adjustment and the damping characteristic adjustment as described above, but the suspension device S of this embodiment is specifically described. Includes a control unit 19 that controls the motor M of the compressor 7, the spring side on-off valve 10, the shock absorber side on-off valve 11, and the exhaust valve 12, and the control unit 19 includes the gas spring A and the pneumatic shock absorber D. The vehicle height and damping characteristics are controlled by adjusting the pressure.

  Hereinafter, the control unit 19 will be described in detail. The control unit 19 includes a vehicle height sensor 20, a vehicle speed sensor 21, and a pressure sensor 22 that detects the pressure in the cylinder 1 of the pneumatic shock absorber D. Based on the vehicle height, vehicle speed, and pressure detected by these sensors 20, 21, 22, the motor M of the compressor 7, the spring side on / off valve 10, the shock absorber side on / off valve 11 and the exhaust valve 12 are controlled. Yes.

Specifically, the control unit 19 includes, for example, a vehicle height target value setting unit 19a that determines the vehicle height target value X * based on the vehicle speed detected by the vehicle speed sensor 21, and the vehicle speed and vehicle height target detected by the vehicle speed sensor 21. A pressure target value setting unit 19b that determines the pressure target value P * of the pneumatic shock absorber D based on the value X *, and a low-pass filter 19c that removes high-frequency components contained in the vehicle height sensor signal output from the vehicle height sensor 20 A low-pass filter 19d that removes a high-frequency component included in the pressure sensor signal output from the pressure sensor 22, and a deviation ε _P between the pressure P obtained from the pressure sensor signal from which the high-frequency component has been removed and the pressure target value P *. A value obtained by adding the vehicle height change X ′ to the vehicle height X obtained from the vehicle height sensor signal from which the vehicle height change X ′ generated by adjusting the pressure of the pressure buffer D and the high-frequency component is removed. When A deviation computing unit 19f for calculating a deviation epsilon _X of the high target value X *, as to match the pressure of the pneumatic shock absorber D to the pressure target value P *, and calculated by the deviation calculation unit 19f and the deviation epsilon _X The motor M of the compressor 7, the spring-side on-off valve 10, the shock absorber-side on-off valve 11, and the drive unit 19 g that drives the exhaust valve 12 are configured to be zero.

  The vehicle height target value setting unit 19a obtains the vehicle height target value X * from the traveling speed (vehicle speed) of the vehicle. The vehicle height target value X * may be obtained from the vehicle speed by map calculation, or the vehicle height target value X * may be changed in a stepwise manner in proportion to the vehicle speed change. For example, when the vehicle speed becomes high, driving is more stable by lowering the vehicle height and lowering the center of gravity of the vehicle. Therefore, the vehicle height target value X * may be guided to reduce the vehicle height target value X * so as to be suitable for the vehicle. It is sufficient to determine *.

  The pressure target value setting unit 19b obtains a pressure target value P * that realizes the damping characteristic of the pneumatic shock absorber D suitable for the vehicle speed from the traveling speed (vehicle speed) of the vehicle. The pressure target value P * may be obtained from the vehicle speed by a map calculation, or the pressure target value P * may be changed in a stepwise manner in proportion to the change in the vehicle speed. When the vehicle speed becomes high, driving with damping characteristics becomes more stable, so it is better to guide the pressure target value P * to increase, and the pressure target value P * should be determined so as to be suitable for the vehicle. That's fine. The pressure target value P * calculated by the pressure target value setting unit 19b is input to the drive unit 19g described later.

  Subsequently, the low-pass filter 19c removes high frequency components from the vehicle height sensor signal output by the vehicle height sensor 20 detecting the vehicle height. The cut-off frequency of the low-pass filter 19c is set to a frequency that only detects a change in the weight on the vehicle body, for example, about 0.1 Hz or less, and the vehicle height changes even if the vehicle body vibrates while traveling. However, the low-pass filter 19c removes a vibration component caused by the vehicle body vibration from the vehicle height sensor signal.

  The low-pass filter 19c filters signals output from the four vehicle height sensors 20 installed in the four-wheel each wheel portion of the vehicle, and the low-pass filter 19c is a vehicle in the four-wheel each wheel portion. High Xn (n = 1, 2, 3, 4) is output.

  Here, as the vehicle height sensor 20, a laser vehicle height sensor that detects the reflected light of the laser light applied to the road surface and obtains the vehicle height by trigonometry, or detects the stroke displacement of the damper main body 1 to obtain the vehicle height. Various sensors such as a stroke sensor and a sensor for determining the vehicle height by detecting the swing angle of the arm that can hold the suspension axle and swing on the vehicle body with respect to the vehicle body can be used.

  Further, the low-pass filter 19d removes a high frequency component from the pressure sensor signal output by the pressure sensor 22 detecting and outputting the pressure in the cylinder 1 of the pneumatic buffer D. The cut-off frequency of the low-pass filter 19d is set to such a frequency that a vibration component due to a pressure change during expansion / contraction of the pneumatic shock absorber D can be removed, for example, about 0.1 Hz or less. The vibration component caused by the vibration of the vehicle body is removed from the pressure sensor signal that is changed by expansion and contraction during travel of the pressure buffer D.

  The low-pass filter 19d filters signals output from the four pressure sensors 22 installed in the respective four-wheel portions of the vehicle, and the low-pass filter 19d is disposed in each four-wheel wheel. The pressure Pn (n = 1, 2, 3, 4) in the cylinder 1 of the pneumatic shock absorber D is output.

The vehicle height change calculation unit 19e calculates a vehicle height change X ′ generated by adjusting the pressure of the pneumatic shock absorber D from the deviation ε _P between the pressure Pn obtained from the pressure sensor signal from which the high frequency component has been removed and the pressure target value P *. To do. In this case, the vehicle height change X ′ is calculated with the vertical upward direction being positive. This calculation is performed for each pneumatic shock absorber D arranged in each of the four wheels. In this calculation, as shown in FIG. 2, if the relationship between the pressure of the pneumatic shock absorber D and the vehicle height is mapped and the vehicle height change X ′ is obtained with reference to the map, the calculation is performed. It can be done easily.

Then, the deviation calculating unit 19f calculates a deviation ε _X between a value obtained by adding the vehicle height change X ′ to the vehicle height Xn obtained from the vehicle height sensor signal from which the high frequency component is removed and the vehicle height target value X *. This deviation ε _X is an excess or deficiency of the vehicle height with respect to the vehicle height target value X * when the pressure of the pneumatic buffer D is set to the pressure target value P *. If this excess or deficiency is eliminated, The vehicle height matches the vehicle height target value X *. This deviation ε _{X is} also calculated for each wheel part of the four wheels, and the pressure of the gas spring A arranged in each wheel is controlled based on this deviation ε _X.

The drive unit 19g drives the motor M of the compressor 7, the spring side on / off valve 10, the shock absorber side on / off valve 11, and the exhaust valve 12 so that the pressure of the pneumatic buffer D matches the pressure target value P *. To do. Specifically, the pressure Pn detected by the pressure sensor 22 is fed back, the difference between the pressure Pn and the pressure target value P * is taken, and the pressure of the pneumatic buffer D is adjusted by proportional integral or proportional differential integral control. . The driving unit 19g includes a motor M, a spring-side on-off valve 10 of the compressor 7 to the deviation epsilon _X which calculates the pressure deviation computing unit 19f of the gas spring A and 0, buffer-side valve 11 and the exhaust valve 12 is driven. Specifically, it may be adjusted to the pressure of the gas spring A by a proportional integral or proportional-derivative-integral control using a deviation epsilon _X.

  Note that the control unit 19 of the present embodiment converts a signal composed of analog voltages output from the vehicle height sensor 20, the vehicle speed sensor 21, and the pressure sensor 22 into a digital signal (not shown) as hardware resources. An A / D converter, a CPU (Central Processing Unit) that captures these signals and executes the processing of each unit, a RAM (Synchronous Dynamic Random Access Memory) that provides a storage area for the CPU, and the processing of each unit A ROM (Read Only Memory) that stores programs such as an application executed by the CPU and an operating system, and a drive circuit that drives the motor M and the solenoids 10d, 11d, and 12d. The configuration of each unit of the control unit 19 can be realized by executing an application program in order for the CPU to process each unit.

  In this case, the low-pass filters 19c and 19d are realized by processing by the CPU. However, if the processing up to the point before the low-pass filters 19c and 19d are interposed is executed by an analog circuit, the low-pass filter 19c. , 19d may be filters for processing analog signals.

  In the above description, the vehicle height is detected by the vehicle height sensor 20, but if the vehicle weight does not change, the pressure in the gas spring A and the pneumatic shock absorber D as shown in FIG. Since the vehicle height can be estimated by detecting the pressure in the gas spring A and the pneumatic shock absorber D by knowing the relationship between the vehicle height and the vehicle height, the vehicle height sensor 20 is A pressure sensor for detecting the pressure in the gas chamber G of the gas spring A may be provided, and in this embodiment, since the motor M is used to drive the compressor 7, By monitoring the torque fluctuation of the motor M during the gas supply to the spring A and the pneumatic shock absorber D, the pressure of the gas spring A and the pneumatic shock absorber D can be estimated, and the gas spring Of gas from A and pneumatic buffer D By grasping the relationship between the air volume and the disposal time, it is possible to estimate the pressure drop amount of the gas spring A and the pneumatic buffer D due to the exhaust time. The pressure of the pressure buffer D can be estimated and the pressure sensor can be eliminated.

  Further, since it is possible to estimate the vehicle height and the pressures of the gas spring A and the pneumatic buffer D, it is possible to determine whether the vehicle height sensor 20 and the pressure sensor 22 are operating normally. Good.

Further, as described above, when the vehicle height X does not coincide with the vehicle height target value X *, the pressures of the gas spring A and the pneumatic shock absorber D are controlled. _If the absolute value of the deviation ε _X between the vehicle height X and the vehicle height change X ′ and the vehicle height target value X * exceeds a threshold value, the vehicle height may be adjusted by the supply / discharge means C. In this case, the vehicle height adjustment can be performed in a timely manner without making the vehicle occupant feel uncomfortable by avoiding frequent vehicle height adjustment.

When a threshold is provided, a deviation ε _all between the total value X _all of the vehicle height Xn and the vehicle height change X ′ in each wheel and the total value of the vehicle height target value X ^* _all in each wheel is obtained. If this deviation exceeds a threshold value, the vehicle height may be adjusted so that the vehicle height Xn of each wheel becomes the vehicle height target value X ^* . In this case, too, frequent vehicle height adjustment is avoided. The vehicle height can be adjusted in a timely manner without causing the vehicle occupant to feel uncomfortable. Further, when the vehicle body is tilted because the vehicle height Xn of the four wheels is added, for example, when the vehicle height on the right side of the vehicle is lowered and the vehicle height on the left side is increased, the total value _Xall is not easily changed. When the vehicle body is tilted by turning or going up and down a slope, it is possible to avoid such a situation that this is regarded as a vehicle height change and the vehicle height is adjusted.

  The vehicle height sensor 20 includes a low-pass filter 19c that filters the vehicle height sensor signal output from the vehicle height sensor signal and removes the high frequency component contained in the vehicle height sensor signal, and the vehicle height obtained from the vehicle height sensor signal from which the high frequency component has been removed. Since control is performed using X, vehicle height adjustment is prevented from being performed due to vehicle height change or noise caused by vibration during vehicle travel superimposed on the vehicle height sensor signal, and vehicle height adjustment is frequently performed. Can be prevented.

  Further, in the above description, the vehicle speed detected by the vehicle speed sensor 21 is input to the control unit 19 and the vehicle height target value X * is set by the control unit 19, but the vehicle is based on information other than the vehicle speed. The high target value X * may be calculated, and the control unit 19 does not obtain the vehicle height target value X * but receives the vehicle height target value X * calculated by the host controller. Also good.

  Further, in controlling the operation of the suspension device S, a change in the height of the vehicle while the vehicle is running may be detected to control the vehicle body posture in real time, thereby suppressing rolling, pitching, squatting, etc. of the vehicle body.

  The above-described configuration of the supply / discharge means C is an example, and it is natural that gas may be supplied / discharged to / from the cylinder C using other configurations. However, in the suspension device S, Since the gas spring A and the pneumatic shock absorber D are connected to and cut off from the supply line 8 by the spring-side on-off valve 10 and the shock-absorber side on-off valve 11, and the exhaust line 9 is opened and closed by the exhaust valve 12. These valves 10, 11, and 12 need only have two positions of communication and cutoff, and can adopt a poppet valve. Therefore, the high sealing performance of the entire system including the gas spring A and the pneumatic shock absorber D can be adopted. Can be secured, there is no worry of gas leakage, it is also resistant to contamination and excellent response speed.

  Further, instead of the configuration of the spring-side opening / closing valve 10 and the shock absorber-side opening / closing valve 11 described above, the supply line 8 is connected to the gas spring A, as in the suspension device in one modification of the embodiment shown in FIG. It is also possible to employ a configuration in which a direction switching valve 23 that selectively communicates with the pneumatic shock absorber D, and an on-off valve 24 upstream of the direction switching valve 23 on the compressor 7 side. In addition, the above-described operations can be realized, and the above-described effects can be achieved.

  Further, like the suspension device in another modification of the embodiment shown in FIG. 4, the on-off valve 24 and the direction switching valve 23 used in the configuration of the suspension device S of the embodiment shown in FIG. The three-port three-position switching valve 25 can be integrated into the switching valve 25, which selectively connects the compressor 7 to the gas spring A and the pneumatic buffer D, positions 25 a and 25 b, the supply line 8, and the gas Three positions 25a, 25b, and 25c can be switched by a push-pull type solenoid 25d provided at one end with a position 25c that cuts off the communication between the spring A and the pneumatic shock absorber D.

  Even when such a switching valve 25 is used, the above-described operations can be realized and the above-described effects can be achieved. In addition, the on-off valve 24 and the direction switching valve 23 are combined into one switching valve 25. Since it can be aggregated, it becomes more economical.

  This is the end of the description of the embodiment of the present invention, but the scope of the present invention is of course not limited to the details shown or described.

It is the figure which showed the suspension apparatus in one embodiment of this invention. It is the figure which showed the relationship between vehicle height, the pressure of a gas spring, and the pressure of a pneumatic buffer. It is the figure which showed the suspension apparatus in one modification of one embodiment of this invention. It is the figure which showed the suspension apparatus in another modification of one embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston 3 Rod 4 Passage 5 Chamber 6 Diaphragm 7 Compressor 7a Discharge port 7b in a compressor Suction port 8 in a compressor Supply line 9 Exhaust line 10 Spring side on-off valve 10a Communication position 10b on spring side on-off valve Shut off on spring side on-off valve Position 10c Spring 10d in spring-side on-off valve Solenoid 11 in spring-side on-off valve 11 Shock-on side on-off valve 11a Communication position 11b on buffer-side on-off valve Shut off position 11c on buffer-side on-off valve Spring 11d on buffer-side on-off valve Solenoid 12 in side opening / closing valve Exhaust valve 12a Communication position 12b in exhaust valve Shut-off position 12c in exhaust valve Spring 12d in exhaust valve Solenoid 13 in exhaust valve 13 Air filter 14 Spring flow Road 15 Buffer passage 16 Dryer 17 Restrictor 18 Check valve 19 Control unit 19a Vehicle height target value setting unit 19b Pressure target value setting unit 19c, 19d Low-pass filter 19e Vehicle height change calculation unit 19f Deviation calculation unit 19g Drive unit 20 Car High sensor 21 Vehicle speed sensor 22 Pressure sensor 23 Direction switching valve 24 Open / close valve 25 Switching valve 25a, 25b, 25c Position 25d in switching valve Solenoid A in switching valve A Gas spring C Supply / discharge means D Pneumatic buffer G Gas chamber r1 Upper chamber r2 lower chamber S suspension device

Claims (6)

A gas spring that is interposed between the vehicle body and the axle and elastically supports the vehicle body, and a pneumatic buffer that is interposed between the vehicle body and the axle in parallel with the gas spring to attenuate relative vibration between the vehicle body and the axle. And a suspension device comprising gas supply and discharge means for supplying and discharging gas to and from the gas spring and the pneumatic shock absorber. The supply / discharge means includes a supply line that connects the compressor to the gas spring and the pneumatic buffer, a spring-side on-off valve that communicates and blocks the supply line and the gas spring, and a communication line that blocks and connects the supply line and the pneumatic buffer. A shock absorber side opening / closing valve, an exhaust line for releasing the gas from the gas spring and the pneumatic buffer, and an exhaust valve provided in the middle of the exhaust line for opening and closing the exhaust line. The suspension device according to claim 1. The supply / discharge means includes a supply line for connecting the compressor to the gas spring and the pneumatic buffer, a direction switching valve for selectively connecting the compressor to the gas spring and the pneumatic buffer in the middle of the supply line, and a supply line An open / close valve that opens and closes the supply line, an exhaust line that releases the gas from the gas spring and the pneumatic buffer, and an exhaust valve that is provided in the middle of the exhaust line and opens and closes the exhaust line. The suspension device according to claim 1, wherein The supply / discharge means includes a supply line for connecting the compressor to the gas spring and the pneumatic shock absorber, a position in the supply line for selectively connecting the compressor to the gas spring and the pneumatic shock absorber, and a position for closing the supply line. And an exhaust line that opens the gas from the gas spring and the pneumatic buffer, and an exhaust valve that is provided in the middle of the exhaust line to open and close the exhaust line. The suspension device according to claim 1. 2. The cylinder is connected to the axle and the rod is connected to the vehicle body to be set upright, and the supply / discharge means supplies and discharges gas into the cylinder through the hollow rod. 5. The suspension device according to any one of 4 to 4. 6. The suspension device according to claim 1, wherein the vehicle height is adjusted by adjusting the pressure of the gas spring after determining the pressure of the pneumatic shock absorber.

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