JP2007055518A - Vehicular suspension - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular suspension capable of preventing breakage of a system by limiting the change of the spring constant to be obtained by an accumulator. <P>SOLUTION: The vehicular suspension comprises a system including a shock absorber 10 (a suspension cylinder) and a spring constant variable device 20, an electric control unit (ECU) 41, and various kinds of sensors 45, 46, 47. The spring constant variable device 20 has accumulators 21, 22, and a spring constant selector valve 23. A liquid chamber R1 of the shock absorber 10 is connected to a liquid chamber R5 of the accumulator 22, and connected to a liquid chamber R3 of the accumulator 21 via the spring constant selector valve 23. The electric control unit (ECU) 41 limits the change of the spring constant to be obtained by the accumulators 21, 22 from a low value to a high value when it is determined whether or not the internal pressure of the system is above the permissible pressure-proof lower limit value of the system, and it is further determined the internal pressure is above the permissible pressure-proof lower limit value based on the result of detection of the sensors 45, 46, 47 or the like. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle suspension device, and more particularly to a vehicle suspension device in which liquid chambers of a plurality of accumulators are connected in parallel to a liquid chamber of a suspension cylinder.

As one example of this type of vehicle suspension device, a plurality of accumulators having liquid chambers connected in parallel to a liquid chamber of a suspension cylinder interposed between a vehicle body and wheels, and the suspension among the plurality of accumulators There is one provided with a spring constant change control device that changes a spring constant obtained by the accumulator by changing the one in communication with the liquid chamber of the cylinder.
Japanese Patent Laid-Open No. Sho 63-130419

  In the vehicle suspension device described in Patent Document 1 described above, the liquid chambers of two accumulators are connected in parallel to the liquid chamber of the suspension cylinder. All of the accumulators are gas-filled, and a spring constant switching valve is interposed between the liquid chamber of one accumulator and the liquid chamber of the suspension cylinder. When the vehicle is traveling on a flat road, the spring constant switching valve is open, the two accumulators function, and the gas in both gas chambers functions as a gas spring. For this reason, the spring constant obtained by the accumulator becomes a low spring constant, and the riding comfort of the vehicle is ensured. On the other hand, for example, when the vehicle is traveling on a undulating road and the vehicle height becomes a predetermined amount or more or less than a predetermined amount, only one accumulator functions due to the closing operation of the spring constant switching valve. Only the gas in the gas chamber functions as a gas spring. For this reason, the spring constant obtained by the accumulator is changed from the low spring constant to the high spring constant, the vertical vibration of the vehicle is suppressed, and the steering stability of the vehicle is ensured.

  By the way, in the vehicle suspension device described in Patent Document 1, when the vehicle height becomes a predetermined amount or more or less than a predetermined amount, the spring constant obtained by the accumulator is changed from the low spring constant to the high spring constant. In addition, the spring constant switching valve is always closed. For this reason, when the internal pressure of the system including the suspension cylinder and the plurality of accumulators is already high when the spring constant switching valve is closed, the internal pressure of the system is estimated based on the input from the road surface, for example, a safety factor. There is a risk of exceeding the allowable upper limit value of the set system.

  The present invention has been made in order to address the above-described problems, and its purpose is to ensure the ride comfort or handling stability of the vehicle by changing the spring constant obtained by the accumulator and to prevent the system from being damaged. The object is to provide a vehicle suspension system.

  In order to achieve the above object, in the present invention, a plurality of accumulators having liquid chambers connected in parallel to a liquid chamber of a suspension cylinder interposed between a vehicle body and wheels, and among the plurality of accumulators, A suspension system for a vehicle comprising a spring constant change control device for changing a spring constant obtained by the accumulator by changing the one in communication with the liquid chamber of the suspension cylinder, wherein the spring constant change control device comprises the suspension Determining means for determining whether or not an internal pressure of the system including the cylinder and the plurality of accumulators is equal to or higher than a permissible lower limit value of the system; Spring constant change restriction that restricts the change of the spring constant obtained by the accumulator when it is determined It is characterized by and a stage. In this case, for example, the spring constant change limiting means may limit the change of the spring constant obtained by the accumulator from a low spring constant to a high spring constant. The allowable pressure limit value of the system is, for example, an allowable pressure value set lower by a predetermined amount corresponding to the input from the road surface than the allowable pressure limit value of the system set in consideration of the safety factor. Means.

  In this vehicle suspension system, when the determination means determines that the internal pressure of the system is equal to or higher than the allowable pressure limit value of the system, the spring constant change limiting means limits the change of the spring constant obtained by the accumulator. For this reason, the spring constant obtained by the accumulator does not change and does not increase. Therefore, even if there is a road surface input in this state, it is possible to avoid that the internal pressure of the system exceeds the allowable upper limit value of the pressure resistance of the system.

  In carrying out the present invention, the determination means includes pressure detection means for detecting the pressure in the liquid chamber of the suspension cylinder, temperature detection means for detecting the temperature of the working fluid in the liquid chamber of the suspension cylinder, and the suspension cylinder. Based on the detection result of at least one of the vehicle height detection means for detecting the vehicle height set by the vehicle height adjustment device capable of adjusting the vehicle height by supplying and discharging the hydraulic fluid into and from the liquid chamber It is also possible to determine whether or not the internal pressure of the system is equal to or higher than the allowable lower limit value of the pressure resistance of the system.

  In this case, for example, the determination means determines whether or not the internal pressure of the system is equal to or higher than the allowable pressure limit of the system based on the pressure in the liquid chamber of the suspension cylinder detected by the pressure detection means. If so, it is possible to directly detect the internal pressure of the system, so that it is possible to accurately avoid the internal pressure of the system exceeding the allowable upper limit value of the withstand pressure of the system.

  Further, the determination means determines whether or not the internal pressure of the system is equal to or higher than the allowable lower limit value of the system based on the temperature of the working fluid in the liquid chamber of the suspension cylinder detected by the temperature detection means, for example. If it exists, it is possible to avoid the internal pressure of the system from exceeding the allowable pressure limit value of the system in a situation where the internal pressure of the system is likely to increase rapidly due to the viscosity of the hydraulic fluid at low temperatures.

  Further, in the apparatus using the vehicle height adjusting device, the determination means determines whether or not the internal pressure of the system is equal to or higher than the allowable pressure limit value of the system based on the vehicle height detected by the vehicle height detection means, for example. If it is, the vehicle height detected by the vehicle height detecting means is lower than the vehicle height set by the vehicle height adjusting device by a predetermined amount or more, that is, the internal pressure of the system increases due to overloading of the vehicle. Therefore, it is possible to avoid the internal pressure of the system from exceeding the allowable upper limit value of the pressure resistance of the system.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a left front wheel side in an embodiment of a vehicle suspension device according to the present invention. A vehicle suspension device according to this embodiment includes a shock absorber 10 as a suspension cylinder, a spring constant variable device. 20 and a vehicle height adjusting device 30. Note that the right front wheel side and the left and right rear wheel sides of the vehicle suspension device according to this embodiment are configured in the same manner as the left front wheel side, and therefore, the left front wheel side will be described as a representative here. Description of the front wheel side and the left and right rear wheel sides is omitted.

  The shock absorber 10 is interposed between the vehicle body BD and the left front wheel Wfl, and includes a cylinder 11, a piston 12, and a piston rod 13. The cylinder 11 is connected to the vehicle body BD at the upper end. The piston 12 is housed in the cylinder 11 in a fluid-tight and slidable manner, and divides the inside of the cylinder 11 into an upper liquid chamber R1 and a lower liquid chamber R2. The piston 12 is formed with a through-hole 12a as an orifice for communicating the liquid chamber R1 and the liquid chamber R2. The piston rod 13 is fixed to the piston 12 at one end, and is connected to a wheel side support member LA represented by a lower arm at the other end. The liquid chamber R1 in the cylinder 11 communicates with the pump side passage Lp through the cylinder side passage Lc.

  The spring constant variable device 20 includes two accumulators 21 and 22 and a spring constant switching valve 23. The accumulators 21 and 22 are both gas-filled, and one accumulator 21 includes a liquid chamber R3 and a gas chamber R4, and the other accumulator 22 includes a liquid chamber R5 and a gas chamber R6. The liquid chamber R3 of the accumulator 21 communicates with the pump side passage Lp through the spring constant switching valve 23 and the accumulator side passage La1, and the liquid chamber R5 of the accumulator 22 communicates with the pump side passage Lp through the accumulator side passage La2. The volume of the gas chamber R4 of the accumulator 21 is set larger than that of the gas chamber R6 of the accumulator 22, and nitrogen gas of a predetermined pressure is sealed in each of the gas chambers R4 and R6.

  The spring constant switching valve 23 is composed of a 2-port 2-position electromagnetic on-off valve, and when in the open position shown in FIG. 1 (in a non-operating state), the fluid chamber R1 of the shock absorber 10 is connected to the cylinder side passage Lc. When the fluid is connected to the liquid chamber R3 of the accumulator 21 through the pump side passage Lp and the accumulator side passage La1 and is in the closed position (position in the operating state), the communication between the liquid chamber R1 of the shock absorber 10 and the liquid chamber R3 of the accumulator 21 Shut off.

  Thus, when the spring constant switching valve 23 is in the open position, the accumulators 21 and 22 function, and the gas in both the gas chambers R4 and R6 functions as a gas spring. Therefore, the springs obtained by the accumulators 21 and 22 The constant is a low spring constant. On the other hand, when the spring constant switching valve 23 is in the closed position, only the accumulator 22 functions and only the gas in the gas chamber R6 functions as a gas spring, so that the spring constant obtained by the accumulators 21 and 22 is obtained. Becomes a high spring constant.

  A relief valve 24 is connected to the accumulator side passage La1 in parallel with the spring constant switching valve 23. When the spring constant switching valve 23 is in the closed position and the pressure in the pump side passage Lp is larger than the pressure in the liquid chamber R3 of the accumulator 21, the relief valve 24 has a pump side passage Lp. When the pressure in the pump side passage Lp becomes larger than the pressure in the liquid chamber R3 of the accumulator 21 by a predetermined amount or more, the pump side passage Lp is communicated with the liquid chamber R3.

  Thereby, after the spring constant switching valve 23 is closed, the pressure difference between the pressure in the liquid chamber R5 of the accumulator 22 and the pressure in the liquid chamber R3 of the accumulator 21 is suppressed to a predetermined amount or less. Therefore, when the spring constant switching valve 23 is opened, a large amount of hydraulic fluid is prevented from suddenly flowing from the liquid chamber R5 of the accumulator 22 into the liquid chamber R3 of the accumulator 21, so that an unnatural change or operation of the vehicle behavior occurs. It is possible to prevent an impact caused by the inflow of the liquid.

  The vehicle height adjusting device 30 includes a hydraulic pump 31, an electric motor 32, vehicle height adjusting valves 33 and 34, and a vehicle height input switch 44 described later. The hydraulic pump 31 is driven by an electric motor 32 to pump hydraulic fluid from the reservoir tank 35, and the hydraulic fluid passes through the check valve 36 for preventing the backflow, the pump side passage Lp, and the cylinder side passage Lc, and the liquid chamber of the shock absorber 10 Supply to R1.

  The vehicle height adjusting valve 33 is a 2-port 2-position electromagnetic on-off valve that is interposed in the pump-side passage Lp and is in the closed position shown in FIG. The communication between the liquid chamber R1 and the hydraulic pump 31 is cut off, and when in the open position (position in the operating state), the liquid chamber R1 of the shock absorber 10 is communicated with the hydraulic pump 31.

  The vehicle height adjustment valve 34 is a 2-port 2-position electromagnetic on-off valve that is interposed in a tank-side passage Lt connected in parallel to the pump-side passage Lp and is in the closed position shown in FIG. (Position in the non-operating state) When communication between the liquid chamber R1 of the shock absorber 10 and the reservoir tank 35 is cut off and in the open position (position in the operating state), the liquid chamber R1 of the shock absorber 10 is placed in the reservoir tank 35. Communicate.

  A relief valve 37 is connected to the tank side passage Lt in parallel with the vehicle height adjustment valve 34. The relief valve 37 shuts off the communication between the pump side passage Lp and the reservoir tank 35 when the vehicle height adjustment valve 34 is in the closed position and the pressure in the pump side passage Lp is less than a predetermined value. When the pressure is equal to or higher than a predetermined value, the pump side passage Lp is communicated with the reservoir tank 35.

  The vehicle suspension device according to this embodiment includes a drive circuit for supplying current to the spring constant switching valve 23, the electric motor 32, and the vehicle height adjusting valves 33, 34, and the spring constant switching valve 23, the electric motor. An electric control unit (ECU) 41 for controlling the operation of the motor 32 and the vehicle height adjusting valves 33 and 34 is provided.

  The electric control unit (ECU) 41 includes a microcomputer whose main components are a CPU, a ROM, a RAM, and the like, and repeats the spring constant changing program shown in FIG. 2 every predetermined time after the ignition switch is turned on. And permitting or limiting the change of the spring constant obtained by the accumulators 21 and 22 from the low spring constant to the high spring constant, and repeatedly executing the roll suppression control program of FIG. The operation of the valve 23 is controlled. The electric control device (ECU) 41 functions as a spring constant change control device together with the spring constant variable device 20. A vehicle speed sensor 42, a lateral acceleration sensor 43, a vehicle height input switch 44, a vehicle height sensor 45, a pressure sensor 46 and a temperature sensor 47 are connected to the electric control unit (ECU) 41.

  The vehicle speed sensor 42 detects the vehicle speed V. The lateral acceleration sensor 43 detects the lateral acceleration Gy in the left-right direction of the vehicle. The vehicle height input switch 44 is a switch for selecting a preset vehicle height mode, for example, “high”, “normal”, or “low”. When the vehicle height input switch 44 is operated by the occupant before the vehicle travels, the electric motor 32 and the vehicle height adjustment valves 33 and 34 are operated and controlled by an electric control unit (ECU) 41. As a result, the hydraulic fluid is supplied to and discharged from the fluid chamber R1 of the shock absorber 10 according to the selected vehicle height mode, and the vehicle height is adjusted.

  The vehicle height sensor 45 functions as vehicle height detection means, and includes a stroke sensor connected between the vehicle body BD and a wheel side support member LA such as a lower arm at the wheel position of the left front wheel Wfl. Thus, the amount of vertical displacement (vehicle height H) of the vehicle body BD relative to the wheel side support member LA is detected. The pressure sensor 46 functions as pressure detection means, and is connected to the pump side passage Lp to detect the pressure P in the liquid chamber R1 of the shock absorber 10. The temperature sensor 47 functions as temperature detection means, and is provided in the shock absorber 10 to detect the temperature T of the working fluid in the liquid chamber R1 of the shock absorber 10.

  Next, the operation of the vehicle suspension device according to the embodiment configured as described above will be described. The electric control unit (ECU) 41 repeatedly executes the spring constant changing program of FIG. 2 every predetermined short time in response to the ON operation of the ignition switch. The execution of the spring constant changing program is started in step S10. In step S11, the vehicle speed V detected by the vehicle speed sensor 42, the pressure P in the liquid chamber R1 of the shock absorber 10 detected by the pressure sensor 46, The temperature T of the hydraulic fluid in the fluid chamber R1 of the shock absorber 10 detected by the temperature sensor 47, a signal indicating switching to each vehicle height mode from the vehicle height input switch 44, and the vehicle detected by the vehicle height sensor 45 Enter high H.

  Next, in step S12, it is determined whether or not the vehicle speed V is greater than 0, that is, whether or not the vehicle is traveling. If the vehicle is stopped, it is not necessary to change the spring constant from the low spring constant to the high spring constant. Therefore, “No” is determined in step S12, and the process proceeds to step S18. In step S18, the restriction flag SFL is set to “0”, and the execution of the spring constant changing program is terminated in step S22.

  This limit flag SFL indicates that the internal pressure of the system is smaller than the permissible lower limit value of the system due to “0”, that is, the permissible upper limit value of the system is set in consideration of the safety factor. This indicates that the pressure is lower than the allowable pressure value that is set lower by a predetermined amount corresponding to the input from, and the closing operation of the spring constant switching valve 23 is allowed. The limit flag SFL indicates that the internal pressure of the system is larger than the allowable pressure limit value of the system due to “1” and the closing operation of the spring constant switching valve 23 should be limited. Is set to “0”.

  Next, a case where the vehicle is traveling will be described. In this case, “Yes” is determined in step S12, and it is determined in step S13 whether or not the spring constant switching valve 23 is in the open operation state based on the excitation signal to the spring constant switching valve 23. As will be described later, the spring constant obtained by the accumulators 21 and 22 by the closing operation of the spring constant switching valve 23 is already set to a high spring constant, for example, in order to suppress the roll of the vehicle body in a turning state of the vehicle. If so, in order to maintain this high spring constant, "No" is determined in step S13, and the restriction flag SFL is set to "0" in step S18. After step S18, the execution of the spring constant changing program is terminated in step S22.

  On the other hand, for example, when the vehicle is traveling straight on a flat road and the spring constant obtained by the accumulators 21 and 22 is maintained at a low spring constant, “Yes”, that is, a spring constant switching valve is set in step S13. It determines with 23 being in an open operation state, and progresses to step S14. In step S14, it is determined whether or not the pressure P in the liquid chamber R1 of the shock absorber 10 is less than the allowable pressure limit value P0 of the system. When the vehicle is traveling straight on a flat road, since the pressure P is less than the allowable pressure limit P0 of the system, it is determined as “Yes” in step S14, and the process proceeds to step S15.

In step S15, it is determined whether or not the temperature T of the hydraulic fluid in the liquid chamber R1 of the shock absorber 10 is lower than a predetermined temperature T0. The predetermined temperature T0 is set to a predetermined low temperature at which the internal pressure of the system suddenly rises due to the increase in the viscosity of the hydraulic fluid, and the internal pressure of the system may exceed the allowable pressure limit of the system. When the vehicle is traveling under a normal environment, since the temperature T is equal to or higher than the predetermined temperature T0, “No” is determined in step S15, and the process proceeds to step S16.

  In step S <b> 16, it is determined whether or not a signal indicating switching from the vehicle height input switch 44 to each vehicle height mode is “normal”. If the “normal” vehicle height mode is selected, “Yes” is determined in step S16, and it is determined in step S17 whether the vehicle height H is less than the predetermined vehicle height H0. This predetermined vehicle height H0 is compared with the standard vehicle height corresponding to the “normal” vehicle height mode by the operation of the vehicle height input switch 44, and the internal pressure of the system may exceed the allowable pressure limit of the system. The vehicle height is set lower by a predetermined amount corresponding to the overloading amount. If the vehicle is not overloaded, “No” is determined in step S17, and the restriction flag SFL is set to “0” in step S18. After step S18, the execution of the spring constant changing program is terminated in step S22.

  On the other hand, if the “low” vehicle height mode is selected, “No” is determined in step S16, “Yes” is determined in step S20, and the vehicle height H is less than the predetermined vehicle height H1 in step S21. It is determined whether or not. This predetermined vehicle height H1 is compared with the standard vehicle height corresponding to the “low” vehicle height mode by the operation of the vehicle height input switch 44, and the internal pressure of the system may exceed the allowable pressure limit of the system. The vehicle height is set lower by a predetermined amount corresponding to the overloading amount. If the vehicle is not overloaded, “No” is determined in step S21, and the restriction flag SFL is set to “0” in step S18. After step S18, the execution of the spring constant changing program is terminated in step S22.

  Next, for example, a case where the vehicle is traveling straight on an uneven road and the spring constant is maintained at a low spring constant will be described. In this case, it is determined as “Yes” in Step S12 and Step S13, respectively, and when the pressure P in the liquid chamber R1 of the shock absorber 10 becomes equal to or higher than the pressure resistance allowable lower limit P0 of the system, “No” in Step S14. In step S19, the limit flag SFL is set to “1”. After step S19, the execution of this spring constant changing program is terminated in step S22.

  On the other hand, when the pressure P in the fluid chamber R1 of the shock absorber 10 is less than the allowable pressure limit P0 of the system, but the temperature T of the working fluid in the fluid chamber R1 of the shock absorber 10 is less than the predetermined temperature T0, In step S14 and step S15, “Yes” is determined, and in step S19, the restriction flag SFL is set to “1”. After step S19, the execution of this spring constant changing program is terminated in step S22. When the pressure P in the liquid chamber R1 of the shock absorber 10 is equal to or higher than the allowable pressure limit value P0 of the system due to the temperature T being lower than the predetermined temperature T0, the following spring constant change program At the time of execution, “No” is determined in step S14.

  Further, if the temperature T of the hydraulic fluid in the fluid chamber R1 of the shock absorber 10 is equal to or higher than the predetermined temperature T0 but the “high” vehicle height mode is selected, “No” is obtained in step S16 and step S20, respectively. In step S19, the limit flag SFL is set to “1”. After step S19, the execution of this spring constant changing program is terminated in step S22. This is because, when the “high” vehicle height mode is selected, the hydraulic fluid is supplied from the vehicle height adjusting device 30 into the liquid chamber R1 of the shock absorber 10, and the liquid chamber R1 of the shock absorber 10 is within the liquid chamber R1. This is because the internal pressure of the system may exceed the allowable pressure limit value of the system even if the pressure P is less than the allowable pressure limit value P0 of the system. When the pressure P in the liquid chamber R1 of the shock absorber 10 becomes equal to or higher than the allowable pressure limit value P0 of the system due to the selection of the “high” vehicle height mode, the subsequent spring constant When the change program is executed, “No” is determined in step S14.

  Further, even when the temperature T of the hydraulic fluid in the fluid chamber R1 of the shock absorber 10 is equal to or higher than the predetermined temperature T0 and the “high” vehicle height mode is not selected, the “normal” vehicle height mode is selected. If the vehicle is in an overloaded state, “Yes” is determined in step S16 and step S17, respectively, and the restriction flag SFL is set to “1” in step S19. Similarly, when the vehicle height mode of “low” is selected, if the vehicle is overloaded, “No” is determined in step S16, and “Yes” is determined in step S20 and step S21, respectively. In S19, the restriction flag SFL is set to “1”. After step S19, the execution of this spring constant changing program is terminated in step S22. When the pressure P in the liquid chamber R1 of the shock absorber 10 is equal to or higher than the allowable pressure limit value P0 of the system due to overloading of the vehicle, in step S14 during the subsequent execution of the spring constant changing program The determination process is “No”.

  Next, an operation for controlling the operation of the spring constant switching valve 23 by a roll suppression control program that is repeatedly executed every predetermined time after the ignition switch is turned on will be described. The roll suppression control program is started in step S30 in FIG. 3, and it is determined in step S31 whether or not the restriction flag SFL is “0”.

  If there is no possibility that the internal pressure of the system exceeds the allowable lower limit value of the system and the limit flag SFL is “0”, “Yes” is determined in step S31, and the lateral acceleration sensor 43 is determined in step S32. The lateral acceleration Gy detected by is input. Next, in step S33, it is determined whether or not the absolute value | Gy | of the lateral acceleration Gy is equal to or greater than a predetermined value Gy0, that is, whether or not the roll needs to be suppressed by increasing the roll rigidity of the vehicle. judge. If the absolute value | Gy | of the lateral acceleration Gy is less than the predetermined value Gy0, “No” is determined in step S33, and the spring constant switching valve 23 is controlled to open in step S35. As a result, the spring constant obtained by the accumulators 21 and 22 is maintained at a low spring constant, and the riding comfort of the vehicle is ensured. After step S35, the execution of the roll suppression control program is terminated in step S36.

  On the other hand, when the limit flag SFL is “0” and the absolute value | Gy | of the lateral acceleration Gy is equal to or greater than the predetermined value Gy0, “Yes” is determined in step S33, and the spring is determined in step S34. The constant switching valve 23 is controlled to be closed. Thereby, the spring constant obtained by the accumulators 21 and 22 is changed from the low spring constant to the high spring constant. For this reason, the roll rigidity of a vehicle becomes high, a roll is suppressed and the steering stability of a vehicle is ensured. After the process of step S34, the execution of this roll suppression control program is terminated in step S36. Thereafter, as long as this state continues, the processing of step S31 to step S34 is repeatedly executed, and the steering stability of the vehicle is ensured. From this state, when the absolute value | Gy | of the lateral acceleration Gy is less than the predetermined value Gy0, “No” is determined in step S33, and the spring constant switching valve 23 is controlled to open in step S35. . As a result, the spring constant obtained by the accumulators 21 and 22 is changed from the high spring constant to the low spring constant, and the riding comfort of the vehicle is ensured.

  By the way, in this embodiment, there is a possibility that the internal pressure of the system may exceed the permissible lower limit value of the system. If the limit flag SFL is “1”, “No” is determined in step S31, and in step S36. This roll suppression control program is terminated. Therefore, in this case, since the process of step S34 is not executed, that is, the spring constant is not changed from the low spring constant to the high spring constant, the spring constant obtained by the accumulators 21 and 22 is maintained at the low spring constant. The As a result, in this state, even if there is a road surface input, it is avoided that the internal pressure of the system exceeds the allowable upper limit value of the pressure resistance of the system.

  Further, in this embodiment, based on the pressure P in the liquid chamber R1 of the shock absorber 10 detected by the pressure sensor 46 by the process of step S14 in FIG. Judgment whether or not. As a result, the internal pressure of the system can be directly detected by the pressure sensor 46, so that it is possible to accurately avoid the internal pressure of the system from exceeding the allowable upper limit value of the system.

  Further, based on the temperature T of the hydraulic fluid in the fluid chamber R1 of the shock absorber 10 detected by the temperature sensor 47 by the process of step S15, it is determined whether or not the internal pressure of the system is equal to or higher than the allowable pressure limit value of the system. Judgment was made. Thus, it is possible to avoid the internal pressure of the system from exceeding the allowable pressure limit value of the system in a situation where the internal pressure of the system is likely to rapidly increase due to the viscosity of the hydraulic fluid at a low temperature.

  In addition, based on the vehicle height H detected by the vehicle height sensor 45 by the processes of steps S16, S17, S20, and S21, it is determined whether or not the internal pressure of the system is equal to or higher than the allowable pressure limit value of the system. did. Thereby, when the vehicle height H detected by the vehicle height sensor 45 is lower than the various vehicle heights “normal” and “low” set by the vehicle height adjusting device 30 by a predetermined amount or more, that is, In a situation where the internal pressure of the system is likely to increase due to overloading, it is possible to avoid the internal pressure of the system from exceeding the allowable upper limit value of the system.

  Further, through the processing of steps S16 and S20, it is determined whether or not the internal pressure of the system is equal to or greater than the allowable lower limit value of the system, based on the “high” vehicle height mode selected by operating the vehicle height input switch 44. I tried to do it. Thus, it is possible to avoid the internal pressure of the system from exceeding the allowable pressure limit value of the system in a situation where the internal pressure of the system is likely to increase due to the setting of the vehicle height “high” by the vehicle height adjusting device 30. .

  In the above embodiment, when the spring constant switching valve 23 is already in the closed operation state, the restriction flag SFL is set to “0” by the processing of steps S13 and S18 of FIG. So that it is not judged as “No”. Therefore, when it is determined “No” in step S31, it is substantially limited when the spring constant switching valve 23 is in the open operation state, and the open operation state is maintained (the low spring constant is maintained). Setting), the change of the spring constant (change from the low spring constant to the high spring constant) is indirectly restricted (prohibited).

  However, if the restriction flag SFL is set to “1” when the spring constant switching valve 23 is in the closed operation state by omitting the process of step S13 in FIG. 2, the determination of “No” in step S31. Thus, the closed operation state can be maintained (high spring constant is maintained), and the change of the spring constant can be indirectly restricted (prohibited). In this case as well, the spring constant obtained by the accumulator does not change and does not increase. Therefore, even if there is road input in this state, the internal pressure of the system will exceed the allowable pressure limit of the system. Can be avoided.

  In addition, when the process in step S13 in FIG. 2 is omitted as described above, the process in step S31 in FIG. 3 can be performed between the process in step S33 and the process in step S34. . In this case, even if the spring constant switching valve 23 is in the closed operation state and the restriction flag SFL is set to “1”, the determination of “No” in step S33 is made when the condition of step S33 is not satisfied. Thus, the process of step S35 is executed, and the change from the high spring constant to the low spring constant is allowed. When the spring constant switching valve 23 is in the open operation state and the restriction flag SFL is set to “1”, the process of step S34, that is, the spring constant is determined by the determination of “No” in step S31. Since the process of closing the switching valve 23 is not executed and the execution of this roll suppression control program is terminated in step S36, the spring constant is directly changed from the low spring constant to the high spring constant. Be restricted (prohibited).

  In the above embodiment, based on the pressure P in the liquid chamber R1 of the shock absorber 10 detected by the pressure sensor 46 in step S14, it is determined whether or not the pressure P is less than the allowable pressure limit value P0 of the system. Based on the temperature T of the hydraulic fluid in the fluid chamber R1 of the shock absorber 10 detected by the temperature sensor 47 in step S15, it is determined whether or not the temperature T is less than a predetermined temperature T0, and step S16. , S17, S20, S21, based on the vehicle height H detected by the vehicle height sensor 45, each standard vehicle height set by the vehicle adjustment device 30 corresponding to “normal” and “low” in the vehicle height mode; Whether the vehicle is overloaded or not, and the vehicle height input switch 44 is operated in steps S16 and S20 to select the “high” vehicle height mode. Luke was to determine whether. However, it is also possible to implement whether or not the internal pressure of the system is equal to or higher than the allowable lower limit value of the system using at least one of the above-described determination conditions.

  In the above-described embodiment, the temperature T of the hydraulic fluid in the liquid chamber R1 of the shock absorber 10 is detected by the temperature sensor 47. In addition to or instead of this, the temperature outside the vehicle is detected. It is also possible to estimate the temperature at which the viscosity of the hydraulic fluid increases.

  Although one embodiment of the present invention and its modified embodiments have been described above, the present invention is not limited to the above-described embodiment and the like, and various modifications can be made without departing from the object of the present invention. Is possible.

  For example, in the above-described embodiments and the like, the case where the vehicle body is rolling as an example of the running state of the vehicle that changes the spring constant has been described. However, when controlling the pitching of the vehicle body other than the vehicle body roll, for example, the spring It can also be implemented to allow or limit constant changes.

  In the above-described embodiment, the spring constant obtained by the two accumulators 21 and 22 is changed to one of the low spring constant and the high spring constant by opening and closing the spring constant switching valve 23. Although implemented, for example, using three or more accumulators, it is implemented so as to be changed to any one of a plurality of spring constants ranging from a low spring constant obtained by a combination of these accumulators to a high spring constant It is also possible to do.

It is the schematic which showed the left front-wheel side in one Embodiment of the suspension system for vehicles by this invention. It is a flowchart of the spring constant change program performed by the electric control apparatus shown in FIG. It is a flowchart of the roll suppression control program performed by the electric control apparatus shown in FIG.

Explanation of symbols

BD ... Car body, LA ... Wheel side support member, Wfl ... Left front wheel, 10 ... Shock absorber (suspension cylinder), 11 ... Cylinder, 12 ... Piston, R1, R2 ... Liquid chamber, 13 ... Piston rod, 20 ... Variable spring constant Device (spring constant change control device) 21, 22 ... Accumulator, 23 ... Spring constant switching valve, R3, R5 ... Liquid chamber, R4, R6 ... Gas chamber, 30 ... Vehicle height adjustment device, 41 ... Electric control device (ECU) ) (Spring constant change control device), 42 ... vehicle speed sensor, 43 ... lateral acceleration sensor, 44 ... vehicle height input switch (vehicle height adjustment device), 45 ... vehicle height sensor (vehicle height detection means), 46 ... pressure sensor (Pressure detection means), 47 ... temperature sensor (temperature detection means)

Claims (3)

A plurality of accumulators having liquid chambers connected in parallel to a liquid chamber of a suspension cylinder interposed between the vehicle body and the wheels, and a plurality of these accumulators in communication with the liquid chamber of the suspension cylinder are changed. In the vehicle suspension system comprising the spring constant change control device that changes the spring constant obtained by the accumulator,
The spring constant change control device includes: a determination unit that determines whether an internal pressure of a system including the suspension cylinder and the plurality of accumulators is equal to or higher than a pressure resistance allowable lower limit value of the system;
And a spring constant change limiting means for limiting the change of the spring constant obtained by the accumulator when the internal pressure of the system is determined to be equal to or higher than the allowable pressure limit value of the system. A vehicle suspension system. The vehicle suspension device according to claim 1,
The determination means includes pressure detection means for detecting the pressure in the liquid chamber of the suspension cylinder, temperature detection means for detecting the temperature of the working fluid in the liquid chamber of the suspension cylinder, and the amount of hydraulic fluid into the liquid chamber of the suspension cylinder. Based on the detection result of at least one of the vehicle height detection means for detecting the vehicle height set by the vehicle height adjustment device capable of adjusting the vehicle height by supplying and discharging, the internal pressure of the system is determined based on the detection result of the system height. It is determined whether it is more than the pressure | voltage tolerance lower limit of this, The suspension system for vehicles characterized by the above-mentioned. The vehicle suspension device according to claim 1 or 2,
The suspension unit for a vehicle is characterized in that the spring constant change limiting means limits the change of the spring constant obtained by the accumulator from a low spring constant to a high spring constant.

Images