JPH04100720A - Suspension device for vehicle - Google Patents

Abstract

PURPOSE:To prevent the deceleration of a vehicle at the time when an operating-fluid forcibly feeding pump has been changed over to a load condition by detecting such a condition that the supply of a large quantity of operating fluid to a hydraulic cylinder is necessary, and by correcting the speed-change pattern of an automatic transmission to the low-speed side while synchronizing with the changeover to the load condition. CONSTITUTION:When the main pressure is less than a prescribed value, on the basis of the output signal of a vertical acceleration sensor 57, a control unit 45 judges whether or not the change rate of vertical acceleration is larger than a first prescribed value G1. If it is not so, the control unit provides an electronically controlled fuel injection device with a command for increasing the output of an engine by a prescribed amount, so that an unload valve 43 is closed to bring a pump 32 into a load condition, and the pressure accumulation of operating oil 44 is started. When it is judged that the change rate of vertical acceleration is greater than the prescribed value G1, whether or not the change rate of vertical acceleration is greater than a second prescribed value G2 being larger than the prescribed value G1 is judged, and if it is not so, the control unit emits a command for forcibly setting an automatic transmission 81 into a power mode to close an unload valve 43.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a suspension system for a vehicle, and more specifically, to a suspension system for a vehicle by supplying and discharging working fluid to and from a cylinder installed between a vehicle body and wheels. This invention relates to a suspension device whose characteristics can be changed.

(Prior art) For example, as shown in Japanese Unexamined Patent Publication No. 63-130418, a hydraulic cylinder is installed between the vehicle body and the wheels, and suspension characteristics are improved by controlling the supply and discharge of working fluid to and from the cylinder. A suspension device for a vehicle that can freely change the amount of suspension is known.

In this type of so-called active control suspension device, in many cases, an accumulator for accumulating working fluid is provided in the high pressure line that communicates with the hydraulic chambers of the hydraulic cylinders, and a pump driven by the engine pumps the working fluid above. In order to supply pressure to the accumulator and maintain the internal pressure of the high pressure line within a predetermined range, the pump is put into a load state that increases the internal pressure when the accumulator internal pressure drops to a predetermined lower limit. A switching means is provided for setting the internal pressure to an unloading state in which the internal pressure does not increase when the internal pressure increases to a predetermined upper limit value.

As the switching means, an unload valve provided in a line connecting the high pressure line and the upstream side of the pump is generally used. That is, when the unload valve, which is made of a solenoid valve or the like, is closed, the load state is set, and when it is opened, the unload state is set.

Further, as this switching means, an automatic unloading valve or the like that controls the operating state of the pump according to the pump discharge pressure and switches between the loading state and the unloading state can be used.

(Problem to be solved by the invention) By the way, the above-mentioned pump cannot have a very large capacity, considering the need to prevent deceleration due to increased engine load and to suppress a significant drop in fuel efficiency. . However, if a relatively small-capacity pump is used, it will not be able to cope with the need to supply a particularly large amount of working fluid, such as when driving on rough roads, and it will not be possible to adequately control vibrations and changes in the posture of the vehicle body. There are some things I can't do.

The present invention has been made in view of the above-mentioned circumstances, and can prevent vehicle deceleration when the working fluid pressure pump is switched to the load state, and at the same time, can prevent vehicle deceleration when a large amount of working fluid is required to be supplied. Another object of the present invention is to provide a suspension device for a vehicle that can satisfactorily control the vibration and posture of the vehicle body.

(Means for Solving the Problems) A vehicle suspension device according to the present invention is a vehicle equipped with an automatic transmission, and has a hydraulic cylinder, an accumulator, a pump for pumping working fluid, a loading state and an unloading state, as described above. In a suspension system for a vehicle, which is provided with a switching means for switching between states and a controller for controlling supply and discharge of working fluid to and from a hydraulic cylinder, it is necessary to supply a relatively large amount of working fluid to the hydraulic cylinder. A means for detecting the state, and a correcting means for correcting the shift pattern of the automatic transmission to a lower speed side in synchronization with the switching to the load state when the above state is detected by the means. It is characterized by:

Further, in a preferred embodiment of the present invention, the above-mentioned controller is configured such that when the shift pattern is corrected by the correction means, if the pressure accumulation increase rate in the accumulator is equal to or less than a predetermined value, It is configured to reduce the amount of supply per hit.

(Operation and Effects of the Invention) If the shift pattern is corrected to the lower speed side as described above, the engine speed will temporarily increase and the pump discharge amount will increase, so a large amount of working fluid can be supplied and Vehicle vibration and posture can be well controlled even while driving.

If the demand for supplying a large amount of working fluid is dealt with as described above, the pump itself can be of a small capacity type. Therefore, it is usually possible to prevent the vehicle from decelerating significantly or from significantly deteriorating fuel efficiency when this pump is switched to the load state.

Additionally, when the speed change pattern is corrected and the rate of increase in pressure in the accumulator is below a predetermined value, it is possible to reduce the amount of working fluid supplied to the hydraulic cylinder per unit time. Pressure can be accumulated more quickly. Therefore, active control of the suspension is prevented from becoming significantly incorrect or completely impossible due to a significant drop in main pressure.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 shows a suspension system for a vehicle according to an embodiment of the present invention, and FIG. 2 shows a hydraulic circuit used in this suspension system. In addition, in the figure,
The main elements corresponding to the right front wheel, left front wheel, right rear wheel, and left rear wheel are numbered rFRJ rFLJ, respectively.
The symbols rRRJ and rRLJ are shown with added symbols, but in the following explanation, those symbols will be added only when it is particularly necessary.

As shown in FIG. 1, a hydraulic cylinder 12 is fixed to the vehicle body 11 for each wheel, and a hydraulic chamber 14 is defined by a piston 13 that is slidably inserted into the hydraulic cylinder 12. has been done. A wheel 10 is held on a piston rod 15 that is integrated with the piston 13. A gas spring 21 is communicated with the hydraulic pressure chamber 14 via a hydraulic passage. The gas spring 21 has a gas chamber 25 defined by a diaphragm 23 as a movable partition wall and a liquid chamber 27, and the liquid chamber 27 is communicated with the hydraulic pressure chamber 14.

In addition, as shown in detail in FIG. 2, in this embodiment, the gas spring 2
Two of them are provided on each ring circumference, and they are connected to the hydraulic cylinder 12 in parallel to each other. An orifice 29 is provided in each of the hydraulic passages 18 that communicate with each of these gas springs 21 . Such a hydraulic cylinder 12, gas spring 2] and orifice 29
The unit consisting of the combination of the above has a basic function as a suspension device due to the buffering effect of the gas spring 21 and the damping effect of the orifice 29.

The above-mentioned hydraulic cylinder 12 has a high pressure pipe 31F or 3
1R is connected and hydraulic cylinder 1 is connected through these pipes.
Hydraulic fluid is supplied and discharged to and from 2. Note that the high pressure pipes 31F and 31R are provided with flow control valves 9F and 31R, respectively.
9R are interposed, and these flow control valves 9 are connected to each cylinder 1.
The cylinder internal pressure is adjusted by controlling the supply and discharge of hydraulic fluid to and from the cylinder.

Hereinafter, a hydraulic circuit for supplying and discharging this hydraulic fluid will be explained with reference to FIG. 2. The vane pump 32 driven by the engine 80 pumps up the hydraulic fluid 44 from the reservoir tank 33 and passes the hydraulic fluid 44 through the common high pressure piping 34 to the front wheel and rear wheel high pressure piping 31F, 31H.
to be pumped to. This common high pressure pipe 34 is provided with a check valve 35, a filter 36, a main accumulator 37 for accumulating pressure, and a hydraulic pressure gauge 38 in this order from the upstream side. Further, an in-pump relief valve 30 is provided in the pump 32 to circulate the discharged hydraulic fluid 44 to the suction side when the discharge side pressure increases abnormally.

The high pressure pipe 31F for the front wheel is the high pressure pipe 31FR1 for the right front wheel.
It is branched into a high pressure pipe 31FL for the left front wheel, and each of these pipes 31FR, 31FL is connected to a flow control valve 9FR, respectively.
It communicates with each hydraulic pressure chamber 14 of the right front wheel hydraulic cylinder 12FR and the left front wheel hydraulic pressure cylinder 12FL via the inflow valves 52F R and 52F L forming the inflow valve 9RL. The flow rate control valve 9 includes the above-mentioned inflow valve 52 and a discharge valve 5 interposed in the recirculation pipe 40F that returns the hydraulic fluid 44 to the reservoir tank 33.
It consists of 3. Both the inlet valve 52 and the outlet valve 53 can take an open position and a closed position, and have a built-in differential pressure valve that maintains the hydraulic pressure at a predetermined value in the open position.

Further, a pilot passage 39F branches off from the high pressure pipe 31F, and this pilot passage 39F is connected to pilot pressure responsive check valves 50F R and 50F L. Each check valve 50 is controlled by the pilot passage 39F to control the operating hydraulic pressure (Nm pressure in the main accumulator 37: main pressure) in the high pressure piping 31 on the upstream side of the inflow valve 52.
It is designed to close when this pilot pressure is less than 40 kgf/c-, for example. In other words, the hydraulic fluid is supplied to the hydraulic cylinders 12F R, 12P L only when the main pressure is 40 kg f /cd or more.
Ejection becomes possible.

In addition, a relief valve 54F is installed in the high pressure pipe 31FH for the right front wheel.
R, and a hydraulic pressure gauge 55FR is provided. On the other hand, the high pressure pipe 31FL for the left front wheel also has a relief valve 54FL and an oil pressure gauge 5.
5FL is interposed. Relief valve 54FR154F
L opens when the internal pressure of the hydraulic cylinders 12F R and 12F L increases abnormally, and the hydraulic fluid 44 is returned to the reflux pipe 40.
Return to F. This reflux passage 40F includes a hydraulic cylinder 12.
FR112F Operates from L/[Return accumulator 59 that performs pressure accumulating function when Ill liquid 44 is discharged
F is attached.

Exactly the same elements as the front wheel elements described above are also provided on the rear wheel high pressure pipe 31R side. In FIG. 2, the front wheel element and the rear wheel element, which are equivalent to each other, are distinguished by the symbols rFJ and rRJ added next to their respective numbers.

The front wheel side reflux pipe 40F and the rear wheel side reflux pipe 40R are connected to a common reflux pipe 41 that reaches the reservoir tank 33 via a cooling circuit 46. The common reflux pipe 41 and the common high pressure pipe 34 are communicated with each other by a relief pipe 42, and the relief pipe 42 has an unload valve 4.
3 are intervening. This unload valve 43 is operated and controlled by a control unit 45 (see Fig. 1) that receives the output of the oil pressure gauge 38, and opens when the main pressure exceeds a predetermined upper limit (-160 kgf/cd, for example). to bring the vane pump 32 into an unloaded state, and in this state, the main pressure reaches a predetermined lower limit (for example, 120 k
g f /cd) or less. When the main pressure falls below the lower limit, the control unit 45
Then, the unload valve 43 is closed to place the vane pump 32 in a loaded state.

As a result, the main pressure rises to the above upper limit value.

In this way, the main pressure is within a predetermined range (120 to 160 kgf
/c4).

Further, the common reflux pipe 41 and the common high pressure pipe 34 are communicated with each other by a relief pipe 47.
7 is provided with a fail-safe valve 48. This fail-safe valve 48 has the function of being switched to the open position in the event of a failure of other valves, returning the oil stored in the main accumulator 37 to the reservoir tank 33, and canceling the high pressure state. Note that a check valve 50FR15 [I
A throttle 51F is provided to delay the closing operation of the FL.

Next, the operation of the suspension device having the above configuration will be explained. The operations of the unload valve 43, the fail-safe valve 4B, the inflow valve 52, and the outflow valve 53 are controlled by a control unit 45 composed of, for example, a microcomputer. The control unit 45 includes the hydraulic pressure gauge 38, a hydraulic pressure gauge 55 provided for each hydraulic cylinder 12,
A vertical acceleration sensor 57 detects the spring maxillary speed for each wheel 10FR, 10FL, 10RR, IDRL, a vehicle height sensor 58 that detects the vehicle height (that is, cylinder stroke) for each wheel 10FR, 110F L, 10RR110RL, and a vehicle body 11. Outputs from a lateral acceleration sensor 61 that detects applied lateral acceleration, a vehicle speed sensor 62, and a signal indicating the state of the automatic transmission 81 are input (in FIG. 1, an oil pressure gauge 55, a vertical acceleration sensor 57, Regarding the vehicle height sensor 58, only the one corresponding to the left rear wheel 10RL is shown).

The control unit 45 includes oil pressure gauges 5 for each wheel.
5. Vertical acceleration sensor 57, vehicle height sensor 5B for each vehicle,
The supply and discharge of the hydraulic fluid 44 is controlled based on the cylinder internal pressure, spring maxillary speed, vehicle height, and lateral acceleration indicated by the lateral acceleration sensor 61 and the lateral acceleration sensor 61, respectively. By supplying and discharging the hydraulic fluid to and from the hydraulic cylinder 12 in this manner, the same effect as changing the throttling resistance of the orifice 29 and the elastic modulus of the gas spring 21 is obtained, and the suspension device functions as a so-called active suspension device. Function. Further, as described below, it is also possible to control the vehicle height for each wheel by controlling the amount of hydraulic fluid in the hydraulic cylinder 12.

Next, a process for controlling the opening and closing of the unload valve 43 will be explained. FIG. 3 shows the flow of this process by the control unit 45. As shown in the figure, in step P1 of the control unit 45, it is determined whether a flag F indicating a downshift of the automatic transmission 81, which will be described later, is set (F-1). If this flag F is not set, the control unit 45 then takes in information indicating the state of the automatic transmission 81 in step P2, and then takes in the output signal of the vertical acceleration sensor 57 in step P3.

Thereafter, in step P4, the control unit 45 determines whether or not it is necessary to switch the pump 32 to the load state, that is, whether or not the main pressure is 120 kgf/d or less. If the main pressure is 120k
If it exceeds g f /cd, then the flow of processing returns to step P1.

On the other hand, if the main pressure is below 120 kg f /c♂, the control unit 45 performs step P5.
Based on the output signal of the vertical acceleration sensor 57, it is determined whether the vertical acceleration change rate is equal to or greater than a first predetermined value 61. If this is not the case, that is, when the vehicle is traveling on a relatively flat road surface, the control unit 45 then in step P6 issues a command to the electronically controlled fuel injection system (EGI) to increase the engine output by a predetermined amount. The control unit 45 then closes the unload valve 43 in step P7. As a result, the pump 32 enters a loaded state, pressure accumulation of the hydraulic fluid 44 is started, and the process flow returns to step P1.

As described above, by slightly increasing the engine output when switching the pump 32 to the load state, it is possible to prevent the vehicle from decelerating due to an increase in engine load accompanying this switching.

On the other hand, if it is determined in step P5 that the vertical acceleration change rate is equal to or higher than the predetermined value 01, that is, if the vehicle is traveling on a so-called rough road, the control unit 45 then proceeds to step P8 to determine the vertical acceleration change rate. It is determined whether or not is equal to or greater than a second predetermined value MGz that is larger than the predetermined value Gl. If this is not the case, that is, if the degree of roughness of the road is relatively low, the control unit 45 then issues a command to forcibly set the automatic transmission 81 to the power mode in step P9, and then in step P7.
At this point, the unload valve 43 is closed.

The automatic transmission 81 of this embodiment is capable of selectively switching between the power mode described above, which sets a relatively large reduction ratio in each transmission, and the econo mode, which sets a relatively small reduction ratio. .

Then, when switching the pump 32 to the load state, if the automatic transmission 81 is set to power mode as described above, the rotation speed of the engine 80 increases and the pump 32 is switched to the load state.
The discharge amount of No. 2 increases.

When the vehicle is traveling on a rough road, it is necessary to supply a large amount of hydraulic fluid 44 to each hydraulic cylinder 12 in order to control the vibration and posture of the vehicle body. Therefore, by increasing the discharge amount of the pump 32 as described above, this requirement can be met and the vibrations and posture of the vehicle body 1 can be favorably controlled.

On the other hand, when it is determined in step P8 that the vertical acceleration change rate is equal to or higher than the second predetermined value 62, that is, when the vehicle is traveling on a particularly bad road, the control unit 45 next performs an automatic gear shift in step PIO. After issuing a command to downshift the machine 81, a flag F indicating that the downshift has been performed is set at step pH, and then, at step P7, the unload valve 43 is closed.

In this case as well, by shifting down the automatic transmission 81, the engine speed increases and the discharge amount of the pump 32 increases. Therefore, in this case, as mentioned above, the automatic transmission 8
The same effect as setting 1 to power mode can be obtained, or in this case, the engine speed increases more markedly. Therefore, it is possible to meet a request that is characterized by a particularly large amount of hydraulic fluid 44 due to the degree of roughness of the road.

When the automatic transmission 81 is downshifted as described above, it will be determined that the flag F is set in step P1 in the next process. In that case, the control unit 45 then performs the following steps in step P12:
Based on the output of the oil pressure gauge 38, it is determined whether the increase in main pressure is greater than or equal to a predetermined value. If so, the control unit 45 resets the flag F in step P13, and the flow of processing returns to step P1.

On the other hand, when it is determined in step PL2 that the rate of increase in the main pressure has not reached the predetermined value, the control unit 45 then reduces the gain of the hydraulic fluid supply and discharge control in step P14 to maximize the supply and discharge amount. The value Qmax is set to be 10% less than the normal value.

Then, the control unit 45 performs step P15.
, it is determined whether the main pressure has reached 160 kgf/c-. If so, the process flow goes through step P13 described above, and then steps P1.
Return to On the other hand, if the main pressure has not reached 160 kg f /cd, the process returns to step P1, but since the flag F-1 remains, the process flow returns to step P1.
Move on to 2.

As described above, unless the increase rate of the main pressure is less than the predetermined value and the main pressure does not reach the upper limit of 160 kg f /c, the maximum value of the hydraulic fluid supply and displacement is determined in step P14. Q sax is decreased by 10% one after another.

By reducing the amount of hydraulic fluid 44 used in this way, the pressure can be accumulated more quickly.
Due to the significant drop in main pressure, active control of the suspension is prevented from becoming significantly incorrect or even impossible.

[Brief explanation of drawings]

1 CN is a schematic diagram showing a suspension device according to an embodiment of the present invention, and FIG. 2 is a diagram showing the hydraulic pressure i used in the suspension device.
FIG. 3 is a flowchart showing the control process of the working fluid pressure accumulation in the above-described actual example device. 10... Wheels 11... Vehicle body 12...
・Hydraulic cylinder 13... Piston 14... Hydraulic pressure chamber of the hydraulic cylinder] 5... Piston rod 18... Hydraulic pressure passage 21
... Gas spring 32 ... Pump 38.55 ... Oil pressure gauge 40 ... Return passage 44 ... Hydraulic fluid 48 ... Fail-safe valve 53 ... Outflow valve 58 ... Vehicle height Sensor 62...Vehicle speed sensor 81...Automatic transmission 31...High pressure piping 37.59...Accumulator 39...Pilot passage 43...Unload valve 45...Control unit 52...Inflow Valve 57... Vertical acceleration sensor 61... Lateral acceleration sensor 80... Engine No. 3 7"<j

Claims (2)

[Claims] (1) Hydraulic cylinders installed between the vehicle body and wheels of a vehicle equipped with an automatic transmission, and an accumulator that accumulates pressure of working fluid in high-pressure lines connected to the hydraulic chambers of these hydraulic cylinders. and a pump that is driven by the engine and pumps working fluid to the accumulator; and the pump is set to a load state in which the internal pressure of the accumulator is increased when the internal pressure of the accumulator decreases to a predetermined lower limit value, so that the internal pressure of the accumulator reaches a predetermined value. A suspension system for a vehicle, comprising: a switching means for setting the internal pressure to an unloading state in which the internal pressure does not increase when the pressure rises to an upper limit; and a controller for controlling supply and discharge of working fluid to the cylinder; means for detecting a state in which a relatively large amount of working fluid is required to be supplied; A suspension device for a vehicle, comprising a correction means for correcting a pattern to a lower speed side. (2) The controller is configured to reduce the amount of working fluid supplied per unit time to the hydraulic cylinder if the rate of increase in pressure in the accumulator is equal to or less than a predetermined value when the speed change pattern is corrected. The suspension device for a vehicle according to claim 1, characterized in that: