JPH02231209A - Fluid pressure type suspension - Google Patents

Abstract

PURPOSE:To prevent transient and sudden change of vehicle height by controlling pressure control valves inserted in each passage means for the supply and discharge of operating fluid which is acting on operating fluid chambers of actuators increasing or decreasing vehicle height, in accordance with the vehicle height detected at the start of operation. CONSTITUTION:Actuators 1 (1FR-1RL) installed on each wheel are respectively equipped with operating fluid chambers (2FR-2RL). Operating fluid is supplied from a pump 6 too each operating fluid chamber 2 through high pressure passage 18 (18FR-18RL), and the operating fluid discharged from each operating fluid chamber 2 is returned to a tank 4 through low pressure passages 48 (48FR-48RL). Pressure control valves 32-38 are inserted midway of these passages 18, 48, which control the supply and discharge of fluid. At this time, the pressure instructed to the pressure control valves 32-38 is controlled in accordance with the vehicle height detected by a vehicle height sensors 144 (144FR-144RL) to surely prevent transient and sudden change of vehicle height.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a hydraulic suspension for vehicles such as automobiles.

BACKGROUND ART Hydraulic suspensions for vehicles such as automobiles have conventionally generally consisted of an actuator that increases or decreases the vehicle height by supplying and discharging working fluid to a working fluid chamber, and a working fluid that supplies working fluid to the working fluid chamber. A supply passage means, a working fluid discharge passage means for discharging the working fluid from the working fluid chamber, a connecting passage means communicating with the working fluid chamber, and a connecting passage means and the working fluid supply passage means or the working fluid discharge passage means. It has a control valve that is selectively connected for communication and controls supply and discharge of working fluid to and from the working fluid chamber.

In such a hydraulic suspension, working fluid may flow out from the working fluid chamber when the bomb that supplies high-pressure working fluid to the working fluid flood passage means is stopped or when an abnormality occurs in the working fluid supply passage means. In order to prevent the vehicle height from decreasing due to It is already known to incorporate an on-off valve in the middle of the means.

Problems to be Solved by the Invention In a hydraulic suspension incorporating such an on-off valve, when the on-off valve is opened with a relatively large differential pressure existing on both sides of the on-off valve at the start of operation, the on-off valve will not open or close. Since a relatively large amount of working fluid flows through the opening/closing valve when the valve is opened, there is a problem in that the vehicle height temporarily fluctuates rapidly, giving a sense of discomfort to the occupants of the vehicle.

This problem arises because the control valve is a pressure control valve, as shown in FIGS. This is particularly noticeable when the on-off valve is a shutoff valve configured to close in response to the pressure in the working fluid supply passage means upstream of the pressure control valve being below a predetermined value. That is, in such a hydraulic suspension, at the start of operation, the pressure within the working fluid supply passage means upstream of the pressure control valve rises from a predetermined value or less, and when the pressure exceeds the predetermined value, the shutoff valve is activated. This is because the control pressure of the pressure control valve at the time when the cutoff valve opens cannot be known precisely because the cutoff valve is opened.

Further, the control valve is a pressure control valve, and the on-off valve is provided on the opposite side of the pressure control valve from the actuator, and responds when the pressure in the working fluid supply passage means upstream of the on-off valve is below a predetermined value. In the case of a shutoff valve configured to close when the shutoff valve opens, if the command pressure to the pressure control valve is 0 or a pressure different from the pressure in the working fluid chamber, there will be no problem until the shutoff valve opens. When the on-off valve is opened, the pressure control valve functions, and the working fluid flows relatively rapidly before and after the pressure control valve, resulting in a temporary sudden change in vehicle height.

The present invention relates to a conventional hydraulic suspension in which an on-off valve is incorporated between a control valve and an actuator or on the opposite side of the actuator from the control valve, and the above-mentioned hydraulic suspension according to the above-mentioned previous proposal. In view of these problems, improvements have been made to prevent the temporary and sudden change in vehicle height that occurs when the on-off valve is opened, and to prevent the vehicle occupants from feeling uncomfortable due to this. The purpose is to provide a hydraulic suspension.

Means for Solving the Problems According to the present invention, the above-mentioned object is achieved by: vehicle height detection means;
an actuator that increases or decreases the vehicle height by supplying and discharging a working fluid to and from a working fluid chamber; a hydraulic spring that communicates with the working fluid chamber; and a working fluid that supplies working fluid at a supply pressure to the working fluid chamber. a supply passage means, a working fluid discharge passage means for discharging the working fluid from the working fluid chamber, and a working fluid discharge passage means provided in the middle of the working fluid supply means and the working fluid discharge passage means, which is provided when the supply pressure is below a predetermined value. a shutoff valve that closes in response; and a pressure control valve that is provided midway through the working fluid supply passage means and the working fluid discharge passage means and controls supply and discharge of the working fluid to and from the working fluid chamber and its pressure. and a control means for controlling the pressure control valve, the control means being configured to control the command pressure to the pressure control valve according to the vehicle height detected by the vehicle height detection means at the time of start of operation. Achieved by hydraulic suspension.

Functions and Effects of the Invention By supplying and discharging the working fluid to the working fluid chamber, the weight of the vehicle body can be reduced in a vehicle equipped with an actuator that increases or decreases the vehicle height and a hydraulic spring that communicates with the working fluid chamber. is carried by the spring, so when the vehicle height is high, the spring's shared load is small, and when the vehicle height is low, the spring's shared load is large, and there is a difference between the vehicle height and the spring's shared load. There is a certain relationship, and there is also a certain relationship between the spring share/sevenfold and the pressure in the working fluid chamber. Therefore, by detecting the vehicle height, the pressure in the working fluid chamber of the corresponding actuator can be known.

According to the above configuration, the control means is configured to control the command pressure to the pressure control valve according to the vehicle height detected by the vehicle height detection means at the time of starting the operation, and the pressure control valve is configured to control the command pressure to the pressure control valve according to the vehicle height detected by the vehicle height detection means. The pressure within the working fluid chamber is controlled to be substantially equal to the pressure within the working fluid chamber. Therefore, in a structure in which a shutoff valve is provided between a pressure control valve and an actuator, the pressures on both sides of the shutoff valve are made substantially equal, thereby avoiding the existence of a large differential pressure on both sides of the shutoff valve. This ensures that temporary and rapid changes in vehicle height caused by a large amount of working fluid flowing through the shut-off valve at the stage when the supply pressure of the working fluid increases and the shut-off valve opens. can be prevented.

In addition, in a structure in which a shutoff valve is provided on the opposite side of the pressure control valve from the actuator, the pressure control valve is actually connected to the working fluid between the pressure control valve and the actuator until the shutoff valve opens. Although it is not possible to control the pressure in the working fluid chamber, the pressure control of the working fluid is started at the stage when the shutoff valve opens, and the control pressure is controlled to be substantially equal to the pressure in the working fluid chamber, so the shutoff is effective. It is possible to reliably prevent a temporary and rapid change in vehicle height caused by a large amount of working fluid flowing through the pressure control valve when the valve is opened.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings.

Embodiment FIG. 1 is a schematic diagram showing an embodiment of a hydraulic suspension according to the present invention. The illustrated hydraulic suspension has one actuator provided for each of the right front wheel, left front wheel, right rear wheel, and left rear wheel of the vehicle (not shown in the figure). , 11'L, IRI? , IRL, and these actuators have working fluid chambers 2 1'R, 2 PL, 2 Rl?, respectively. , 2}? L
have.

Further, in the figure, 4 indicates a reserve tank that stores a working fluid as a working fluid, and the reserve tank 4 is connected to a suction channel 10 in which a filter 8 for removing foreign matter is provided in the middle.
It is connected in communication with the suction side of the bomb 6. A drain passage 12 is connected to the pump 6 for collecting working fluid leaked inside the pump 6 into the reserve tank 4. The bomb 6 is rotationally driven by an engine 14, and the rotation speed of the engine 14 is detected by a rotation speed sensor 16.

A high pressure flow path l8 is connected to the discharge side of the bomb 6.

A check valve 20 is provided in the middle of the high-pressure flow path 18 to allow only the flow of working fluid from the bomb toward each actuator, and between the bomb 6 and the check valve 20, the working fluid discharged from the bomb is provided. An attenuator 22 is provided to absorb pressure pulsations and reduce pressure changes. The high pressure flow path 18 includes a front wheel high pressure flow path 18F and a rear wheel high pressure flow path 1.
8R is connected to one end, and accumulators 24 and 26 are connected to these high pressure channels, respectively.

Each of these akinimulators has a high pressure gas sealed therein so as to absorb pressure pulsations of the working fluid and perform a pressure accumulating action.

Further, one end of the high pressure flow path 1gPR for the right front wheel, the high pressure flow path 18PL for the left front wheel, the high pressure flow path 18RR for the right rear wheel, and the high pressure flow path 18RL for the left rear wheel are connected to the high pressure flow paths 18F and 18H, respectively. . High pressure flow path 18FI? ,1 8FL,
There are filters 2 8PR, 2 8PL, 2 8RR, 2 8 in the middle of 1 8RR and 1 8RL, respectively.
RL is provided, and the other ends of these high-pressure channels are connected to P boats of pilot-operated three-boat switching control valves 40, 42, 44, and 46 of pressure control valves 32, 34, 36, and 38, respectively. ing.

The pressure control valve 32 is connected to the switching control valve 40 and the high pressure flow path 18F.
It consists of a flow path 50 that communicates and connects the low-pressure flow path 481'R for the right front wheel, and a fixed throttle 52 and a variable throttle 54 provided in the middle of the flow path.

A low pressure passage 48PR is connected to the R boat of the switching control valve 40, and a connection passage 56 is connected to the A boat. The switching control valve 40 has a fixed throttle 52 and a variable throttle 54.
It is a spool valve that takes in the pressure Pp in the flow path 50 between the When the pressures Pp and Pa are equal to each other, the switching position 40b switches to the switching position 40b, which cuts off communication between all boats when the pressures Pp and Pa are equal to each other.
When the pressure is lower than the pressure Pa, the switching position 4. connects the boat R and the port A in communication. It is designed to switch to Oc. Further, the variable throttle 54 changes the effective passage cross-sectional area of the throttle by controlling the current supplied to the solenoid 58, and thereby works together with the fixed throttle 52 to create a pressure Pp.
It is designed to change the

Similarly, pressure control valves 34 to 38 are each pressure control valve 32
pilot-operated three-port switching control valves 42, 44, 46 corresponding to the switching control valve 40; flow passages 60, 62, 64 corresponding to the flow passage 50; and fixed throttles 66, 68 corresponding to the fixed throttle 52. , 70, and variable apertures 72, 74, and 76 corresponding to the variable aperture 54, and the variable apertures 72 to 76 have solenoids 78, 80, and 82, respectively.

Moreover, the switching control valves 42, 44, 46 are connected to the switching control well 40.
The R boat has a low pressure flow path 48FL for the left rear wheel and a low pressure flow path 48R for the right rear wheel.
R, low pressure flow path 48RI for left rear wheel. One end is connected, and the A boat has connection channels 84, 86, and 88, respectively.
is connected at one end. In addition, the switching control valves 42 to 46
are the flow paths 6 between the corresponding fixed throttle and variable throttle, respectively.
Pressure pp within 0-64 and corresponding connection channels 84-88
This is a Subur valve that takes in the pressure Pa inside as a pilot pressure, and when the pressure Pp is higher than the pressure Pa, the boat P
Switching position 42a s 4 for communicating and connecting boat A with boat A
4a. 46a, and switches to switching positions 42b, 44b, and 46b which cut off communication between all boats when pressures Pp and Pa are equal to each other, and connect boat R and port A for communication when pressure pp is lower than pressure Pa. It is designed to switch to switching positions 42e, 44c, and 46c.

As schematically shown in FIG. 1, each actuator IPR, IFL, IRR, IRL has a cylinder 106PR, 106FL, 106RR, 1, respectively.
06RL, and working fluid chambers 2PR, 2PL, which fit into the corresponding cylinders and cooperate with the corresponding cylinders.
Piston 1 08PR defining 2RR, 2RL,
108PL, 108RR, and 108RL, each connected to a suspension arm (not shown in the figure) through a cylinder, and connected to the vehicle body (not shown in the figure) at the tip of the piston rod. There is.

Also, the cylinders 106FR and 106P of each actuator
One ends of drain channels 110, 112, 114, and 116 are connected to L, 106RR, and 106RL.

The other ends of the drain channels 110, 112, 114, and 116 are connected to a drain channel 118, which is connected to the reserve tank 4 via a filter 120, thereby preventing leakage from the working fluid chamber. The used working fluid is returned to the reserve tank.

Working fluid chamber 2PR. 2PL, 2RR, and 2RL have accumulators 1 that function as hydraulic springs via throttles 124, 126, 128, and 130, respectively.
32, 134, 136, and 138 are connected. Also pistons 10gPR, 108FL, 108R
R. 108RL has a flow path 14Or'R,
140PL. 140RR and 140RL are provided. Each of these channels is a corresponding channel 5.
6, 84 to 88 and working fluid chambers 2PR, 2PL, 2R
R, 2Rl, and filters 142FR, 14 2PL11 4 2RR, 1 are connected in the middle, respectively.
4 Has 2RL. Also, actuator I PI
? , I PL, I Rl? , I RL are vehicle height sensors 144FR, 144FL, 144R} that detect the distance between the vehicle body and the corresponding wheel. ,1
44RL is provided.

Pilot-operated shutoff valves 150, 152, 154, 156 are provided in the middle of the connecting channels 56, 84-88, respectively, and these shutoff valves are connected to the corresponding pressure control valves 40, 42, 44, 46, respectively. High pressure flow path 1 on the more upstream side
When the differential pressure between the pressure in 8FR, 18FL, 18RR, and 18RL and the pressure in drain passages 110, 112, 114, and 116 is below a predetermined value, the valve is maintained in a closed state. In addition, the connection channels 56, 84 to 8
The portions between the corresponding pressure control valves 8 and the shutoff valves are downstream of the variable throttles in the flow paths 50, 60, 62, and 64 of the corresponding pressure control valves by flow paths 158, 160, 162, and 164, respectively. It is connected in communication. Channel 158-1
Relief valves 166, 168, 1 are provided in the middle of 64, respectively.
70, 172 are provided, and these relief valves are connected to corresponding flow passages 158, 160, 162, 164, respectively.
The pressure on the upstream side of the flow path, that is, the side of the corresponding connection flow path, is taken in as a pilot pressure, and when the pilot pressure exceeds a predetermined value, the valve is opened and a part of the working fluid in the corresponding connection flow path is transferred to the flow path. 50, 60-64.

The cutoff valves 150 to 156 are connected to the high pressure flow path 18PR, respectively.
1 8PL, 1 8RI? , 18RL may be configured to maintain the valve closed state when the differential pressure between the pressure within RL and the atmospheric pressure is equal to or less than a predetermined value.

The other ends of the low pressure passages 4'8PR and 48FL are connected to one end of the low pressure passage 48F for the front wheels, and the other ends of the low pressure passages 48RR and RL are connected to the - end of the low pressure passage 48R for the rear wheels. has been done. The other ends of the low pressure channels 48F and 48R are connected to one end of the low pressure channel 48 in communication. The low pressure flow path 48 has an oil cooler 174 in the middle and a filter 17 at the other end.
It is connected to the reserve tank 4 via 6. A portion of the high-pressure flow path 18 between the reverse p-stop valve 20 and the attenuator 22 is connected to the low-pressure flow path 48 through a flow path 178 . A relief valve 180 is provided in the middle of the flow path 178 and is set to a predetermined pressure in advance.

In the illustrated embodiment, the high pressure channel 18R and the low pressure channel 4
8R is a flow path 188 that has a filter 182, a throttle 184, and a normally open electromagnetic on-off valve 186 that can adjust the flow rate.
are connected to each other by. The electromagnetic on-off valve 186 is configured to open the valve and adjust the flow rate of the working fluid passing through the valve by energizing the solenoid 190 and changing the excitation current. Also, the high pressure flow path 181
? and the low-pressure flow path 48R are connected to each other by a flow path 194 having a pilot-operated on-off valve 192 in the middle. The on-off valve 192 takes in the pressure on both sides of the throttle 184 as a pilot pressure, and maintains the closed position 192a when there is no differential pressure on both sides of the throttle 184, and when the pressure on the high pressure flow path 18R side with respect to the throttle 184 is high. The valve is switched to the open position 192b. Thus aperture 1
84, the electromagnetic on-off valve 186 and the on-off valve 192 cooperate with each other to selectively communicate and connect the high-pressure flow path 18R and the low-pressure flow path 48R, and therefore the high-pressure flow path 18 and the low-pressure flow path 48, so that the pressure is lower than that of the high-pressure flow path. A bypass valve 196 is configured to control the flow rate of the working fluid flowing into the flow path.

Further, in the illustrated embodiment, a pressure sensor 198 is provided in the high pressure flow path 18H, and the pressure of the working fluid in the high pressure flow path is detected by the pressure sensor 198. In addition, compression coil springs 199FR, 199FL, 199RR, and 1 are provided as suspension springs between the upper seat fixed to the rod portion of the piston of each actinator and the lower seat fixed to the cylinder, respectively.
99RL is loaded.

The electromagnetic on-off valve 186 and the pressure control valves 32-38 are controlled by an electric control device 200 shown in FIG. Electrical control device 200 includes a microcomputer 202 .

The microcomputer 202 may have a general configuration as shown in FIG. 2, and includes a central processing unit (CPU) 204 and a read only memory (ROM) 2.
06, random access memory (RAM) 208,
It has an input boat device 210 and an output boat device 212, which are connected to each other by a bidirectional common bus 214.

The input port device 210 receives a signal indicating the rotation speed N of the engine 14 from the rotation speed sensor 16, a signal indicating the pressure Ps in the high pressure flow path from the pressure sensor 198, and an ignition switch (IGSW) 216 indicating that the ignition switch is in the on state. An emergency switch (located in the vehicle interior and operated by the vehicle occupant)
EMSW) 218 indicates whether the switch is in the on state, vehicle height sensor 144PR, 144F
Vehicle height I1 (1-P) of parts corresponding to the right front wheel, left front wheel, right rear wheel, and left rear wheel from L, 144RR, and 144RL
R, 1? L%RR%I? A signal indicating L) is respectively input. The input boat device 210 appropriately processes the signals input thereto and outputs the processed signals to the CPU and RAM 208 based on the block diagram stored in the ROM 206 and according to instructions from the CPU 204 . The ROM 206 stores the control flow shown in FIG. 3 and the maps shown in FIGS. 4 to 7. In accordance with instructions from the CPU 204, the output boat device 212 outputs a control signal to the electromagnetic on-off valve 186 via a drive circuit 220, and outputs a control signal to the pressure control valves 32 to 38, specifically variable throttles 54 and 72, via drive circuits 222 to 228, respectively.
, 74, 76, and the control signal is output to the display 232 via the drive circuit 230.

The operation of the illustrated embodiment will now be described with reference to the flowchart shown in FIG.

Note that the control flow shown in FIG. 3 is started when the ignition switch 216 is closed. In the flowchart shown in Fig. 3, the flag Ff is related to whether or not there is a failure at any part of the hydraulic suspension, and 1 indicates whether there is a failure at any part of the hydraulic suspension. The flag Fc indicates whether the engine is in an operating state, 1 indicates that the engine has 1,000 operating states, and the flag Fp indicates that the pressure Ps of the working fluid in the high-pressure flow path is Threshold pressure P that completely opens the shutoff valves 150 to 156
This is related to whether or not you have ever experienced a level of C or higher.
1 indicates that the pressure Ps has exceeded the pressure Pc, and the flag Fs indicates the standby pressure Pbl (1-FRSFLSRR,
RL) is set or not.
1 indicates that standby pressure is set.

First, in step 10, a main relay (not shown in the figure) is turned on, and then in step 2
Go to 0.

In step 20, the contents stored in the RAM 20g are cleared and all flags are reset to 0, and then the process proceeds to step 30.

In step 30, a signal indicating the rotation speed N of the engine 14 detected by the rotation speed sensor 16, a signal indicating the rotation speed N of the engine 14 detected by the rotation speed sensor 16,
98, a signal indicating whether the ignition switch 216 is in the on state, a signal indicating whether the EMSW 218 is in the on state, vehicle height sensors 144PR, 144FL. ,14
41? l? , 144RL, and then the process proceeds to step 40.

In step 40, it is determined whether or not the ignition switch is in the off state, and when it is determined that the ignition switch is in the off state, the process proceeds to step 220, and a check is made to determine that the ignition switch is in the on state. When the determination has been made, the process advances to step 50.

In step 50, it is determined whether or not the EMSW is in the on state, and when it is determined that the EMSW is in the on state, the process proceeds to step 200, where it is determined that the EMSW is not in the on state. When the determination has been made, the process advances to step 60.

In step 60, it is determined whether the flag Ff' is 1 or not, and when it is determined that it is Fr-1, the process proceeds to step 200, and it is determined that it is not Ff-1. If so, proceed to step 70.

In step 70, it is determined whether or not the engine is being operated by determining whether the engine rotation speed N detected by the rotation speed sensor 16 and read in step 30 exceeds a predetermined value. is carried out, and when it is determined that the engine is not being operated, the process proceeds to step 110, and when it is determined that the engine is being operated, the process proceeds to step 80.

Note that whether or not the engine is being operated may be determined by determining whether or not the generated voltage of a generator (not shown in the drawings) driven by the engine is equal to or higher than a predetermined value.

At step 80, a flag Fe is set to 1,
Thereafter, the process proceeds to step 9'0. In this case, the flag Fc
If it is already set to 1, it remains that way.

In step 90, the current Ib applied to the solenoid 190 of the electromagnetic on-off valve 186 of the bypass valve 196 is RO
Based on the map corresponding to the graph shown in FIG. 4 stored in M206, calculation is performed according to Ib-1b+ΔIbs, and the process then proceeds to step 100.

In step 100, the current Ib calculated in step 90 is applied to the solenoid 190 of the electromagnetic on-off valve 186, thereby driving the bypass valve 196 in the closing direction, and then the process proceeds to step 130.

In step 110, it is determined whether the flag Fe is 1 or not, and when it is determined that the flag is Fc-1, that is, it is determined that the engine has stopped after being started, the process proceeds to step 200. When it is determined that the engine is not Fc-1, that is, that the engine has not been started at all, the process advances to step 120.

In step 120, it is determined whether the pressure PS in the high-pressure flow path is equal to or higher than Pc at the threshold, and when it is determined that Ps≧Pc is not satisfied, the process proceeds to step 160, where Ps≧Pc When it is determined that this is the case, the process advances to step 130.

At step 130, flag Fp is set to 1, and then step 140 follows.

In step 140, based on the deviation between the table height Hl at the position corresponding to each wheel read in step 30 and the reference vehicle height Hot, the vehicle height adjustment amount ΔH at the position corresponding to each wheel is determined.
l is calculated according to the following formula, and then step 15
Go to 0.

ΔOld■Old-Hot The calculation of the vehicle height 31 adjustment amount ΔHl does not form part of the present invention, and therefore the vehicle height adjustment amount may be calculated in other ways.

In step 150, the solenoids 58, 78,
The electric power all to be applied to 80 and 82 is calculated, and then the process proceeds to step 270.

In step 160, it is determined whether the flag Fp is 1 or not, and it is determined that the flag Fp is Fp-1, that is, the pressure Ps of the working fluid in the high pressure flow path has exceeded the threshold pressure Pc. If it is determined that the pressure has become lower than this, the process proceeds to step 140, where it is determined that the pressure is not Fp-1, that is, it is determined that the pressure PS has never exceeded the threshold pressure Pc. If the process has been performed, the process advances to step 170.

In step 170, it is determined whether or not the flag Fs is 1, and if it is determined that it is Fs-1, the process proceeds to step 270, and it is determined that it is not Fs-1. In some cases, the process proceeds to step 190.

In step 180, the control pressure of each pressure control valve at the start of operation of the illustrated embodiment, that is, the standby pressure P
bl (1-PR, FLSRR, l?L) to the corresponding working fluid chambers 2PR, 2PL. 21? R
, 21? In order to control the pressure to substantially equal to the pressure PI in L, the pressure control valves 32 to 3 are operated based on a map corresponding to the graph shown in FIG. 7 stored in the ROM 206.
8 variable apertures 54, 72, 76 solenoids 58, 78
~ Current energized to 82 II H -PR, PLSR
RSRL) is calculated, and then the process proceeds to step 190.

At step 190, the flag Fs is set to 1, and the process then proceeds to step 270.

In step 200, the solenoid 190 of the electromagnetic on-off valve 186 of the bypass valve 196 is
The current 1b to be applied to is calculated by Ib-1b-ΔIbe, and the process then proceeds to step 210.

In step 210, the current 1b calculated in step 200 is applied to the solenoid 190, thereby driving the bypass valve 196 in the opening direction, and then the process proceeds to step 270.

In step 220, it is determined whether or not a timer related to the time Tart from when the ignition switch is turned off to when the main relay is turned off is activated. If it is determined that the Tofr timer is activated, the process advances to step 240, and if it is determined that the Tofr timer is not activated, the process advances to step 230.

In step 230, the Torf timer is started, and then the process proceeds to step 240.

In step 240, based on the map corresponding to the graph shown in FIG.
b is calculated according to Ib-1b-ΔIM, and then the process proceeds to step 250.

In step 250, the current 1b calculated in step 280 is applied to the solenoid 190 of the electromagnetic on-off valve 186.
By doing so, the bypass valve 196 is driven in the valve opening direction, and the process then proceeds to step 260.

In step 260, it is determined whether or not the time Toff has elapsed, and when it is determined that the time Ton has elapsed, the process proceeds to step 33,0, and the time Tor
If it is determined that f has not elapsed, the process advances to step 270.

In step 270, steps 90, 200, 24
It is determined whether or not the current 1b calculated at 0 is greater than or equal to the reference value lbo, and when it is determined that Ib≧Ibo is not satisfied, the process proceeds to step 300, where Ib≧I
When it is determined that it is bo, step 280
Proceed to.

In step 280, it is determined whether the pressure Ps of the working fluid in the high pressure flow path read in step 30 is equal to or higher than the reference value Pso, and it is determined that Ps≧Pso is not satisfied. When prompted, proceed to step 300 and select Ps.
When it is determined that ≧Pso, step 2
Proceed to 90.

In step 290, the current calculated in step 160! 1 is the variable throttle solenoid 5 of each pressure control valve
8, 78 to 82, each pressure control valve is driven to perform vehicle height adjustment, vehicle body attitude control, etc., and then the process proceeds to step 300.

In step 300, it is determined whether or not a fail exists at any location within the fluid pressure suspension, and when it is determined that a fail does not exist, the process proceeds to step 320, where it is determined that a fail exists. When it is determined that this is the case, the process advances to step 310.

In step 310, the fail flag Fr is set to 1, and the process then proceeds to step 320.

In step 320, diagnosis processing is performed for each part in the hydraulic suspension, and if an abnormality such as a failure exists, a code number indicating the location is displayed on the display 232, and a code number indicating the location is displayed. If there is no abnormality, the process returns to step 30 without displaying the code number on the display, and steps 30 to 320 described above are repeated.

In step 330, the main relay is turned off, thereby ending the control flow shown in FIG. 3 and stopping power to the electric control device 200 shown in FIG. .

Thus, according to this embodiment, when the hydraulic suspension starts operating, a negative determination is made in steps 40 to 60, and a negative determination is made in step 70 before the engine has started yet. It will be done. As shown in FIG. 8, when the engine starts after a certain time Tx has elapsed since the ignition switch was closed, a YES determination is made in step 70, and the process proceeds to step 90. At this point, the current 1b is calculated based on the map corresponding to the graph shown in FIG. In this case, as shown in FIGS. 4 and 8, Ib is 0 from the time the engine starts until time TsI, after which the current 1b completely closes the bypass valve.
Enough current! 1 over time (Ts 2 -Ts I).

Therefore, the bypass valve is gradually closed after the engine has started and reached a complete explosion state, thereby ensuring that the load on the pump and engine will suddenly increase and the engine will stop operating when the hydraulic suspension starts operating. This can be avoided and the pressure of the working fluid in the high pressure channel can be gradually increased.

Note that the bypass valve starts to close, and as a result, the high pressure flow path 18
Until the pressure in the cylinder increases and the pressure rises to the set pressure of the attenuator, the sound of the pressure pulsation of the working fluid caused by the bomb is relatively high, so the current 1b in step 90 is The operations may be performed according to the pattern shown in dashed lines in FIG. That is, as shown in FIG. 8, the current 1b is relatively quickly increased until the current IO reaches the amount by which the bypass valve is closed so that the pressure in the high-pressure flow path 18 reaches the set pressure of the attenuator. & By gently increasing the current 1b to I, it is possible to reduce the generation of noise due to the discharge pulsation of the bomb.

Also, when the engine starts, steps 120, 160,
At step 170, a negative determination is made, at step 180, the control current If to be flooded to each pressure control valve is calculated based on the map corresponding to the graph shown in FIG. The control current is supplied to each pressure control valve, so that the control pressure of each pressure control valve, that is, the pressure in the connecting flow path between each pressure control valve and the corresponding isolation valve, is adjusted to the corresponding working fluid chamber. The standby pressure Pbl is controlled to be substantially equal to the pressure of .

Therefore, since each shutoff valve opens with the pressures in the connecting passages on both sides thereof being substantially equal to each other, the vehicle height increases due to the large amount of working fluid flowing through the shutoff valve when the shutoff valve opens. Temporary sudden changes can be reliably prevented.

In this case, as mentioned above, when the hydraulic suspension starts operating, the bypass valves are gradually closed, thereby gradually increasing the pressure in the high-pressure flow path, and as a result, each cutoff valve is gradually opened. Even if there is some pressure difference on both sides of the shutoff valve, it is possible to avoid a temporary sudden change in the vehicle height when the shutoff valve is opened, and therefore high precision can be achieved in the standby pressure control as described above. It's not even requested.

In the embodiments described above, the cutoff valve is provided between the pressure control valve and the actuator, but the cutoff valve may be provided on the opposite side of the pressure control valve from the actuator. In such a horizontal structure, the pressure control valve cannot actually control the pressure of the working fluid in the connecting flow path until the shutoff valve opens, but it is activated at the stage when the shutoff valve opens. Pressure control of the fluid is started, and the control pressure is controlled to be substantially equal to the pressure of the working fluid chamber. Therefore, even with this structure, it is possible to reliably prevent temporary and sudden changes in vehicle height caused by a large amount of working fluid flowing through the pressure control valve when the shutoff valve is opened. .

Further, in the above embodiment, the working fluid supply passage means and the working fluid discharge passage means are common between the control valve (pressure control valve) and the working fluid chamber of the actuator, but these passage means are At least a portion between the control valve and the working fluid chamber may be independent from each other.

Furthermore, in the above embodiment, the vehicle height Hi and the current II are fixed for the front wheels and the rear wheels, but as shown in FIG. When the supply pressure of the working fluid falls below a predetermined value, that is, when the shutoff valve closes, the command current ll for each pressure control valve (corresponding to the pressure in the working fluid chamber at that time) and vehicle height are set. Hl is read and stored in RAM, a curve on the Hl-11 map is identified based on these values, and then an instruction current I1 for each pressure control valve is determined based on the detected vehicle height and the identified curve. You can.

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to such embodiments, and various other embodiments are possible within the scope of the present invention. will be clear to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of a hydraulic suspension according to the present invention, FIG. 2 is a block diagram showing an electric control device of the embodiment shown in FIG. 1, and FIG. A flowchart showing the control flow achieved by the electric control device shown in FIG. 2, and FIGS. 4 to 6 are flowcharts showing the control flow achieved by the electric control device shown in FIG. Figure 7 is a graph showing a map used when calculating the current 1b supplied to the bypass valve when the operation is stopped.
Graph showing the relationship between current Il and current Il supplied to each pressure control valve, FIG. 8 is a time chart showing changes in current 1b at the start of operation of the hydraulic suspension system, and FIG. It is a graph similar to FIG. 7 showing another aspect of determination. I PR, I FL, 1 1? R, I RL
...actuator, 2PR, 2PL, 2RR,
2RL... Working fluid chamber, 4... Reserve tank, 6... Pump, 8... Filter. 10... Suction channel, 12... Drain channel. 14...Engine, 1
6... Rotation speed sensor, 18... High pressure flow path, 20...
・Check valve, 22... Attenuation valve, 24, 26...
・Accumulator, 32, 34, 36, 38...pressure control valve, 40, 42, 44, 46...switch control valve,
48...Low pressure flow path, 52...Fixed throttle, 54...
Variable throttle, 56... Connection flow path, 58... Solenoid, 66, 68, 70... Fixed throttle, 72, 74, 76
...Variable aperture, 78, 80, 82...Solenoid,
84, 86, 88... connection flow path, 110-118...
・Drain channel, 120...filter, 124-130
...Aperture, 132-138...Accumulator, 1
44FR, 1441"L, 144RR.144RL...
・Vehicle height sensor, 50-156...Shutoff valve. 166-1
72...Relief valve, 174...Oil cooler. 1
76... Filter, 180... Relief valve. 182
...filter, 184...throttle, 186...electromagnetic on-off valve, 190...solenoid, 192...on-off valve, 196...bypass valve, 198, 199...PR
．． 1 9 9FL11 9 9RR, 1 9 9
RL...Vehicle height sensor, 200...Turtle type control device,
202...Microcomputer, 204...CP
U, 206...ROM, 208...RAM, 210
...Manual port device, 212...Output port device,
216...Ignition switch, 218...E
MSW, 220-230... Drive circuit, 232...
Display device Figure 2 Patent applicant Toyota Motor Corporation representative
Masaki Akashi, Patent Attorney

Claims (1)

[Claims] a vehicle height detection means; an actuator that increases or decreases the vehicle height by supplying and discharging a working fluid to and from a working fluid chamber; a fluid pressure spring that communicates with the working fluid chamber; and an actuation of supply pressure to the working fluid chamber. a working fluid supply passage means for supplying fluid; a working fluid discharge passage means for discharging the working fluid from the working fluid chamber; a shutoff valve that closes in response when the pressure is below the specified value; and a shutoff valve that is provided in the middle of the working fluid supply passage means and the working fluid discharge passage means to control the supply and discharge of the working fluid to and from the working fluid chamber, and to control the pressure thereof. a pressure control valve that controls the
control means for controlling the pressure control valve, the control means being a fluid pressure type configured to control the command pressure to the pressure control valve according to the vehicle height detected by the vehicle height detection means at the time of start of operation. suspension.