JPH04123913A - Vehicle suspension device - Google Patents

Abstract

PURPOSE:To prevent the unprepared suspension of supply discharge control and to continue the supply discharge control of hydraulic working fluid even in the case where running on a rough road causes the failure of supply pressure by correcting downward fixed pressure to condition the suspension of supply discharge control when a vehicle running road is rough. CONSTITUTION:A pump 28 draws a hydraulic oil 32 from a reservoir tank 30, and forcedly feeds it to each of high pressure pipes 26F, 26R for a front and a rear wheel through a common high pressure pipe 26. In this case, when supply pressure becomes below a lower limit setting value (fixed pressure P1), an unload relief valve 70 is closed through a control unit, and the hydraulic oil is therefore accumulated in a main accumulator 40 to raise the pressure in the high pressure pipe 26. When the supply pressure becomes lower than the fixed pressure P1, an electromagnetic switching valve 48 is closed at a fixed pressure P2(P2<P1) to stop the supply discharge control, which ends at a fixed pressure P3(P3<P2). In the case where a vehicle running road is rough, the fixed pressure P2 to condition the suspension of the supply discharge control is corrected downward.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention is configured to be able to change suspension characteristics by supplying and discharging working fluid to and from cylinders installed between a vehicle body and wheels. This invention relates to a suspension device.

(Prior Art) A vehicle suspension device generally consists of a combination of a mechanical spring and a shock absorber, but as disclosed in Japanese Patent Application Laid-open No. 83-130418, for example, a suspension system for a vehicle is composed of a combination of a mechanical spring and a shock absorber. By installing a cylinder in and controlling the supply and discharge of working fluid to this cylinder,
Suspension devices configured to freely change suspension characteristics such as vehicle height and hardness and softness have also been proposed.

The above-mentioned supply/discharge control in such a suspension device is generally performed while maintaining the supply pressure of the working fluid within a predetermined range. When the predetermined pressure P1 is reached, pressure is accumulated in a main accumulator serving as a pressure supply source to increase the supply pressure.

Furthermore, conventionally, when the supply pressure is lower than the predetermined pressure P1, the supply/discharge control is stopped at a predetermined pressure P2 (P2 < Pl), and the supply/discharge control is further terminated at a predetermined pressure P3 (P3 < P2). A suspension device configured as described above has also been proposed. This is because if the supply pressure decreases to the predetermined pressure p1, the supply pressure should be increased, but the fact that it has decreased to the predetermined pressure P2 means that
Either a lot of working fluid is being consumed in the cylinder, or something is wrong with the piping system.

Therefore, the supply and discharge control is suspended and the supply and discharge control is waited for the subsequent change in supply pressure, and when the supply pressure rises and recovers to the above-mentioned predetermined pressure P1, the supply and discharge control is resumed as there is no abnormality in the piping system, and on the other hand,
If the supply pressure further decreases to the predetermined pressure P3,
This system is designed to provide fail-safety by terminating the supply/discharge control assuming that there is an abnormality in the piping system.

(Problems to be Solved by the Invention) In such a suspension device, the predetermined pressure P1. P2. It is preferable to set the pressure difference between P3 to be small. This is because if an abnormality actually occurs in the piping system, it is preferable to end the supply/discharge control promptly in order to prevent leakage of working fluid and the like due to this abnormality.

However, if the pressure difference is set small,
When driving on rough roads where the supply load of working fluid is large, the supply and discharge control may stop due to a drop in supply pressure even though there is no abnormality in the piping system. I couldn't make it too small.

The present invention has been made in view of these circumstances, and it is an object of the present invention to continuously control the supply and discharge of working fluid to the extent possible on both normal roads and rough roads while ensuring its fail-safe function. The object of the present invention is to provide a suspension device for a vehicle that can be used in a vehicle.

(Means for Solving the Problems) The vehicle suspension device according to the present invention is capable of
The above LJ is achieved by downwardly correcting the predetermined pressure P2, which is a condition for suspending the supply/discharge control.

In other words, the invention described in claim (1) relates to a vehicle configured to be able to change suspension characteristics by controlling the supply and discharge of working fluid to and from cylinders installed between a vehicle body and wheels. In the suspension device, when the supply pressure of the working fluid decreases, the supply pressure is increased when it reaches a predetermined pressure Pl, and the supply pressure is increased to a predetermined pressure P2 (
The control is stopped when P2 < PI ), the control is terminated when the predetermined pressure P3 (P3 < P2 ) is reached, and the predetermined pressure is stopped when it is detected that the vehicle is traveling on a rough road. The present invention is characterized by comprising a control means configured to downwardly correct P2.

Further, the invention described in claim (2) is configured to be able to change the suspension characteristics by controlling supply and discharge of working fluid to and from cylinders installed between the vehicle body and the wheels. In a vehicle suspension system, when the supply pressure of the working fluid decreases, the supply pressure is increased when it reaches a predetermined pressure P1, and the supply pressure is increased to a predetermined pressure P2 (P
When l<Pl), the control is stopped and the predetermined pressure P3
The control means is configured to terminate the control when (p3 < Pz), and to correct the predetermined pressure P2 downward when it is detected that the vehicle speed has become below a predetermined value. It is characterized by:

(Operations and Effects of the Invention) As shown in the above configuration, according to the invention set forth in claim (1), when the vehicle travels on a rough road, the predetermined pressure P2, which is a condition for suspending the supply and exhaust control, is corrected downward. Therefore, even if the supply pressure decreases due to driving on a rough road, it is possible to prevent the supply and discharge control from being inadvertently stopped. , while ensuring its fail-safe function, it can be carried out as continuously as possible on both normal roads and rough roads.

Furthermore, if the vehicle speed exceeds a predetermined value, it is unlikely that the road the vehicle is traveling on is or could become a bad road, but if the vehicle speed is below the predetermined value, the road the vehicle is traveling on is a rough road. It is possible that there is something that could happen or that the road could be bad. According to the invention as claimed in claim (2), when the vehicle speed is below a predetermined value, the predetermined pressure P2, which is a condition for suspending supply and exhaust control, is corrected in the opposite direction.
1) Similar to the invention described above, supply and discharge control of the working fluid can be performed as continuously as possible on both normal roads and rough roads while ensuring its fail-safe function.

(Examples) Examples of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a suspension device for a vehicle according to the present invention, and FIG. 2 is an overall configuration diagram of the suspension device.

In addition, in the diagram, the main elements corresponding to the right front wheel, left front wheel, right rear wheel, and left rear wheel are numbered rFRJ.
rFLJ rRRJ and rRLJ are shown with added symbols, but in the following description, those symbols will be added only when particularly necessary.

As shown in FIG. 2, a hydraulic cylinder 4 is fixed to the vehicle body 2 for each wheel, and a hydraulic chamber 8 is defined by a piston 6 that is slidably inserted into the hydraulic cylinder 4. ing. A wheel 12 is held on a piston rod 10 that is integrated with the piston 6.

A gas spring 14 is communicated with the hydraulic chamber 8 via a hydraulic passage. This gas spring 14 has a gas chamber 18 and a liquid chamber 2 defined by a diaphragm 16 as a movable partition.
0, and this liquid chamber 20 is communicated with the hydraulic pressure chamber 18.

As shown in FIG. 1, three gas springs 14 are provided for the front wheels and two gas springs are provided for the rear wheels, and these springs are arranged in parallel and communicated with each hydraulic cylinder 4. The hydraulic passages 22 communicating with each of these gas springs 14 include
Each is provided with an orifice 24. A unit consisting of such a combination of the hydraulic cylinder 4, the gas spring 14, and the orifice 24 has a buffering effect of the gas spring 14,
The damping effect of the orifice 24 provides the basic function of a suspension device.

Each hydraulic cylinder 4 has high pressure piping 28F or 26
R is connected, and hydraulic fluid is supplied to and discharged from the hydraulic cylinder 4 through this piping.

The pump 28 that supplies this hydraulic fluid is a vane pump driven by an engine, and is connected to a reservoir tank 30.
The hydraulic fluid 32 is pumped up through the common high-pressure piping 26, and the hydraulic fluid is passed through the high-pressure piping 26F for the front wheels and the rear wheel.
Pressure feed to 26R. This common high-pressure pipe 26 is provided with a filter 36, a check valve 38, a main aggregator 40 for accumulating pressure, and a system oil pressure gauge 42 in this order from the upstream side. Further, the pump 28 is provided with an in-pump relief valve 44 that recirculates the discharged hydraulic fluid to the suction side when the pressure on the discharge side increases abnormally.

The high pressure pipe 26F for the front wheel is the high pressure pipe 28FR1 for the right front wheel.
It is branched into a high-pressure pipe 26FL for the left front wheel, and each of these pipes 2 [iF R, 26F L is a hydraulic pressure chamber 8 of the hydraulic cylinder 4FR for the right front wheel and the hydraulic pressure cylinder 4FL for the left front wheel, respectively.
is communicated with. The same applies to the rear wheels.

Pilot passages 46F and 4.6R are branched from the high pressure pipes 28F and 2[iR, respectively, and these pilot passages 48F and 46R are connected to an electromagnetic on-off valve 48, respectively. Each of the above high pressure piping 2 [1FR2BFL, 28
RR, 26RL are equipped with pressure guarantee valves 50 sequentially from the upstream side.
A flow control valve 52 with a built-in, a pressurized on-off valve 54, a relief valve 56, and a hydraulic pressure gauge 58 are interposed. and"
The relief port of each relief valve 56 described in 2 is connected to the reflux pipe 60F.
Or connected to BOR.

Further, the hydraulic fluid return ports of the pressure guarantee valve 50 and the electromagnetic on-off valve 48 are also connected to the above-mentioned return pipe BOF or 60R. A return aggregator 62 is installed near the flow rate control valve 52 of these return pipes GOF and 60R, respectively, to perform a pressure accumulating function.

The front wheel side reflux pipe BOF and the rear wheel side reflux pipe 60R are connected to a common reflux pipe 60 that reaches the reservoir tank 30 via a cooling circuit 64. The common reflux pipe 60 and the common high pressure pipe 26 are communicated with each other by relief pipes 66 and 68, and an unload relief valve 70 and an ignition switch interlocking valve 72 are provided in the relief pipes 6G and 68, respectively. Connections between the relief pipes 66 and 08 and the common high pressure pipe 26 are made on the -L flow side and the downstream side of the check valve 38, respectively.

Next, the operation of the suspension device having the configuration described in "2" will be explained.

The operations of the unload relief valve 70, the ignition switch interlocking valve 72, the electromagnetic on-off valve 48, and the flow rate control valve 52 are controlled by a control unit 74 (see FIG. 2) comprising, for example, a microcomputer. This control unit 74 includes the system oil pressure gauge 4.
2. Oil pressure gauge 58 provided for each hydraulic cylinder 4; acceleration sensor 76 for detecting spring-acceleration for each wheel 12FR, +2FL, +2RR, 12RL; 2RR, 12R
The output of a vehicle height sensor 78 that detects the vehicle height (that is, cylinder stroke) for each L is input (in FIG. 2, the oil pressure gauge 58, acceleration sensor 76,
and only the vehicle height sensor 78 is shown). The control unit 74 controls supply and discharge of hydraulic fluid based on the cylinder internal pressure, sprung boat speed, and vehicle height indicated by the oil pressure gauge 58, acceleration sensor 76, and vehicle height sensor 78, respectively.

That is, first, when the electromagnetic on-off valve 48 is closed by the control unit 74, even if the pump 28 etc. are operating normally, the hydraulic fluid in the pilot passage 46 is closed by the electromagnetic on-off valve 48. The supply to valve 54 is cut off. The pressurized on-off valve 54 connected to the pilot passage 46 normally remains closed and opens only when a predetermined operating pressure is received at the operating pressure receiving port 54a. Therefore, when the supply of hydraulic fluid to the operating pressure receiving port 54a is cut off as described above, the operating pressure receiving port 54a is in a closed state. When the pressurized on-off valve 54 is thus closed, the suspension device exhibits characteristics based on the elastic modulus of the gas spring 14 and the throttling resistance of the orifice 24. That is, ]
3 At this time, the suspension device becomes a so-called passive suspension.

On the other hand, when the electromagnetic on-off valve 48 is opened by the control unit 74 while the pump 28 etc. are operating normally, the pressure of the hydraulic fluid is applied to the operating pressure receiving port 54a of the pressurized on-off valve 54. This opens the on-off valve 54. In this way, the pressurized on-off valve 54 is opened, and
For example, when the flow control valve 52 is opened to the opening degree specified by the control unit 74,
When hydraulic fluid is supplied to the hydraulic pressure chamber 8 of the hydraulic cylinder 4 while the hydraulic fluid is being displaced upward (to the left in FIG. 1), the supplied hydraulic fluid causes the piston 6 to move. As a result of the displacement being suppressed, the dynamic spring constant of the suspension device changes in the direction of increasing. By supplying and discharging the hydraulic fluid into the hydraulic cylinder 4 in this way, the same effect as changing the throttling resistance of the orifice 24 and the elastic modulus of the gas spring 14 can be obtained, and the suspension device functions as a so-called active suspension device. do. It is also possible to control the vehicle height for each wheel by controlling the amount of hydraulic fluid in the hydraulic chamber 8 of the hydraulic cylinder 4.

During supply/discharge control, if the pressure in the high pressure pipe 26 (i.e. supply pressure) indicated by the system oil pressure gauge 42 becomes equal to or higher than the second limit set value, an unload relief command is issued by the control unit 74. The valve 70 is opened, whereby the hydraulic fluid is returned to the reservoir tank 30, thereby preventing an abnormal rise in pressure within the high pressure pipe 26. Further, the control unit 74 performs control to close the ignition switch interlocking valve 72 only when the ignition switch is ON, so that after the engine is stopped, the ignition switch interlocking valve 72 is opened and the high pressure state in the high pressure pipe 2G is released. Ru.

On the other hand, during the supply/discharge control, when the supply pressure becomes lower than the lower limit set value (predetermined pressure P1), the unload relief valve 70 is closed by a load command from the control unit 74, and the hydraulic fluid is supplied to the main accumulator 40. The fuel is supplied and accumulated in the main accumulator 40, and the pressure in the high pressure pipe 26 is increased.

When the supply pressure is lower than the predetermined pressure Pl, the control unit 74 closes the electromagnetic on-off valve 48 at a predetermined pressure P2 (Pl<Pl), suspends the supply/discharge control, and further closes the supply/discharge control at a predetermined pressure P3 (p3<Pl). ) to end supply/discharge control. This is because the supply pressure decreases and the predetermined pressure P
1, the supply pressure should be increased, but the fact that it has decreased to the predetermined pressure P2 means that a large amount of hydraulic fluid is being consumed in the hydraulic cylinder 4, or there is an abnormality in the piping system. is occurring.

Therefore, the supply and discharge control is suspended and the supply and discharge control is waited for the subsequent change in supply pressure, and when the supply pressure rises and recovers to the above-mentioned predetermined pressure Pl, the supply and discharge control is resumed as there is no abnormality in the piping system, and on the other hand,
If the supply pressure further decreases to the predetermined pressure P3,
This system is designed to provide fail-safety by terminating the supply/discharge control assuming that there is an abnormality in the piping system.

Furthermore, in this embodiment, when the vehicle travels on a rough road, or when the road is likely to become rough, the predetermined pressure P2, which is a condition for suspending the supply/exhaust control, is corrected downward.

The above control will be explained in more detail below according to flowchart 1 in FIG.

First, in step S1, the supply pressure is monitored, and in S2, the supply pressure P is set to "1 limit set value (160)cgr/CI.
#) Determine whether or not it is above, and if YES, issue an unload command to lower the supply pressure P in S3 and return to SL; if NO, in S4, the supply pressure P is set at a predetermined pressure P1, which is the lower limit set value. (120 kgf/c♂) or less is determined, and if No, the process returns to Sl, and if YES, a load command is issued to increase the supply pressure P in S5, and the process proceeds to S6.

In S6, it is determined whether the road the vehicle is traveling on is a rough road. This rough road judgment is performed when the integral value of the vertical acceleration acting on the vehicle body detected by the acceleration sensor 76 or the integral value of the pressure inside the hydraulic cylinder 4 detected by the oil pressure gauge 58 is set to a predetermined set value. The determination is made based on whether or not the value has exceeded the limit. If it is determined in S6 that the road is rough, the process goes to 88'; if not, the process goes to S7] 7.

In S7, it is determined whether the vehicle speed V detected by the vehicle speed sensor (not shown) is equal to or higher than a predetermined value (80 km/h). If the vehicle speed V is equal to or higher than the predetermined value, it is assumed that the vehicle will not be traveling on rough roads thereafter, and the process moves to S8.

If the value is not greater than the predetermined value, the process moves to 88'.

In S8, supply pressure P or predetermined pressure Pz (11.5kgl
'/C♂) or less, and if No, returns to SL, but if YES, stops supply/discharge control of the hydraulic fluid to the hydraulic cylinder 4 in S9 and shifts to SL, 0. .

At Sl, 0, supply pressure P or predetermined pressure P3 (1,10k
gr/c) or less, and if YES, Sl
At 1, a fail determination (control prohibition determination) is made on the assumption that some abnormality has occurred in the piping system, and the supply/discharge control is terminated.

If the SIO judgment is No (that is, P3<P≦P2), SI2 gives a predetermined grace period, and S13
supply pressure P or specified pressure Pi (120kgr/cJ)
It is determined whether or not the above value has been reached. If it becomes P1 or more within the grace period, it is assumed that there is no abnormality in the piping system in S14, and the suspension of the supply/discharge control is canceled and the process returns to Sl. If it does not become 21 or more, the process returns to S9 to maintain the dormant state. . Then, when the above-mentioned grace period has elapsed, the process shifts to Sll and the supply ulilij control ends. Note that instead of giving a predetermined time delay in Sl2, it may be determined whether the rate of change in the supply pressure P is negative (that is, whether the pressure is in a dropping state).

Also when it is determined in S6 that the road the vehicle is traveling on is a rough road, and when it is determined in S7 that the vehicle speed V is not equal to or higher than the predetermined value, the same flow 88' to S]4 as described above is performed.
14', S8' to S14' are controlled respectively, but the predetermined value P2 (115kgf/c
J) is S8', the predetermined value pz' (105kgr/
cJ), S8' has a predetermined value Pz (1,10kg
f/c♂) respectively, and along with this,
Predetermined value P3 at SIO (1,10kgf'/cJ
) is the predetermined value P3 (1,00kgr/
c4), S10', the predetermined value P3 (1,05kg
The difference is that f/c+&) are respectively corrected downward.

In this way, the predetermined value Pz (11,5kgr/cJ
) to the predetermined value Pz'(105kgi'/c+#)
By making a downward correction, even if the supply pressure decreases due to driving on a rough road, it is possible to prevent the supply/discharge control from being inadvertently stopped. In addition, the predetermined value P2 (]1
5kgf/cJ) to a predetermined value P2 (110kgf/cJ)
By making a downward correction to cJ), the supply and exhaust control will be inadvertently suspended when the vehicle enters a rough road at low to medium speeds, when the vehicle is currently traveling on a normal road or may be traveling on a rough road in the next moment. can be prevented.

As mentioned above, fail-safe against piping system abnormalities is
This is done under the control of the control unit 74,
In this embodiment, mechanical fail-safe is also provided. That is, for example, high pressure piping 2B
If the oil pressure (supply pressure) upstream of the flow control valve 52 drops abnormally due to damage to the flow control valve 52 (for example, P < 90k
gr/cJ), even if the electromagnetic on-off valve 48 is open, the predetermined operating pressure will not be applied to the pressurized on-off valve 54. As a result, the on-off valve 54 automatically enters the closed state, and at this time the suspension device enters the aforementioned passive state. Of course, even in this state, the basic function of the suspension device is maintained, so there is no problem with the running of the vehicle. Furthermore, when the engine is stopped when the vehicle is parked, the pump 28 is stopped and the ignition switch interlocking valve 72 is opened, so that the predetermined operating pressure is not applied to the operating pressure inlet 54a of the pressurized on-off valve 54. Therefore, in this case, even if the electromagnetic on-off valve 48 fails and is left open, the pressurized on-off valve 54
Since this is in the closed state, a situation in which the hydraulic fluid gradually flows out from the hydraulic cylinder 4 and the vehicle height is lowered is reliably prevented.

As described in detail above, according to the present embodiment, when the road the vehicle is traveling on is a rough road or is likely to become a rough road, the predetermined pressure P2, which is a condition for suspending the supply and exhaust control, is corrected downward. This ensures a fail-safe function for supplying and discharging hydraulic fluid, allowing it to be performed as continuously as possible on both normal and rough roads.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a vehicle suspension device according to the present invention, FIG. 2 is an overall configuration diagram of the above embodiment, and FIG. 3 is a flow chart showing the operation of the above embodiment. . 2...Vehicle body 4...Hydraulic pressure cylinder (cylinder) I2...Wheel 26...High pressure piping 32
...Hydraulic fluid (working fluid) 40...Main accumulator

Claims (2)

[Claims] (1) In a vehicle suspension device configured to be able to change suspension characteristics by controlling the supply and discharge of working fluid to and from cylinders installed between the vehicle body and the wheels, the supply of the working fluid When the pressure decreases, the predetermined pressure P_1
, the supply pressure is increased to a predetermined pressure P_2(
P_2 < P_1), the control is stopped, and when the predetermined pressure P_3 (P_3<P_2) is reached, the control is terminated, and when it is detected that the vehicle is traveling on a rough road, the predetermined pressure is stopped. A suspension device for a vehicle, comprising a control means configured to downwardly correct P_2. (2) In a vehicle suspension device configured to be able to change suspension characteristics by controlling the supply and discharge of working fluid to and from cylinders installed between the vehicle body and the wheels, the supply of the working fluid When the pressure decreases, the predetermined pressure P_1
, the supply pressure is increased to a predetermined pressure P_2(
P_2<P_1), the control is stopped, and when the predetermined pressure P_3 (P_3<P_2) is reached, the control is terminated, and when it is detected that the vehicle speed has become below a predetermined value, the predetermined pressure is stopped. A suspension device for a vehicle, comprising a control means configured to downwardly correct P_2.