JPH0459417A - Suspension device for vehicle - Google Patents

Abstract

PURPOSE:To prevent hindrance of starting property and unstable idling by receiving the output of a vehicle speed detecting means, and correcting the upper limit value of an accumulator internal pressure for switching pump operating state from load state to unload state, at the time of vehicle stopping, smaller than the value at the time of running. CONSTITUTION:The signals of various sensors such as a vehicle speed sensor 62, a high pressure piping oil pressure gauge 38, an oil pressure gauge not shown for each cylinder 12, a vertical accelerometer 57, and a ground clearance sensor 58 are inputted to a control unit 45 to conduct each control. When the oil pressure detected by the oil pressure gauge 38 is lowered to a lower limit value, the pump is laid in load state, and when it reaches an upper limit value, the pump is controlled to unload state. When the stop of a vehicle is judged by the detection output of the vehicle speed sensor 62, the upper limit value for switching to unload is corrected smaller than the value at the time of running. Thus, the pump is quickly laid in unload state, and engine load can be reduced.

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. 83-130418, 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 communicating with the hydraulic chambers of the hydraulic cylinders, and a pump driven by the engine pumps the working fluid above the 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.

Note that as the switching means, an unload valve provided in a line connecting a high pressure line and an upstream side of the pump is generally widely 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.

(Problems to be Solved by the Invention) However, considering the load on the engine, the pump described above cannot have a very large capacity. Therefore, generally, the accumulator internal pressure does not reach the upper limit unless a considerable amount of time is spent after the switching means switches to the load state.

The accumulator internal pressure often drops below the above lower limit while the vehicle is stopped, and in that case, the pump is put into a loaded state immediately after the engine starts, and pressure accumulation in the accumulator begins. become. In this case, if the loaded state continues for a long time due to the circumstances described above and reaches the time when the vehicle starts, the engine load increases due to the pump operation, and the starting performance of the vehicle may become very poor.

There is also the problem that idling tends to become unstable due to the increased engine load caused by the pump operation.

Such problems are particularly noticeable when the engine is cold.

The present invention has been made in view of the above-mentioned circumstances, and provides a suspension device for a vehicle that can prevent the starting performance of the vehicle from being impaired or idling to become unstable due to the load of the hydraulic fluid pressure pump. The purpose is to provide

(Means for Solving the Problems) A suspension device for a vehicle according to the present invention includes a hydraulic cylinder, an accumulator, a pump for pumping working fluid, a switching means for switching between a loading state and an unloading state, and a hydraulic cylinder as described above. supply of working fluid to the pressure cylinder;
A suspension system for a vehicle equipped with a controller for controlling discharge, comprising means for detecting vehicle speed, and receiving an output from the means to determine an upper limit value of an accumulator internal pressure that specifies switching to an unloading state by the switching means. The present invention is characterized in that, when the vehicle is stopped, a correction means is provided for correcting the value to a smaller value than the value when the vehicle is running.

(Operation and Effects of the Invention) When the above upper limit value is corrected to a small value, the working fluid pressure pump becomes unloaded more quickly.

In this way, in many cases, the pump is in an unloaded state by the time the vehicle starts, reducing the engine load, and the starting performance is not impaired.

Additionally, if the pump is unloaded sooner, the engine load is reduced and the idling state is stabilized sooner.

(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 21 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
1. R is connected, and hydraulic fluid is supplied to and discharged from the hydraulic cylinder 12 through these pipes. Note that the high pressure pipes 31F and 31R are each equipped with a flow control valve 9F.
, 9R are interposed, and these flow control valves 9 control the supply and discharge of hydraulic fluid to and from each cylinder 12 to adjust the cylinder internal pressure.

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 pipe 34 to the front and rear wheel high pressure pipes 31F and 31.
Force feed to R. 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, in the pump 32, an in-pump relief valve 30 is provided that circulates 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 31F R and 31F L is connected to a flow control valve 9FR.
, 9RL are connected to the respective hydraulic pressure chambers 14 of the right front wheel hydraulic cylinder 12FR and the left front wheel hydraulic cylinder 12FL through the inflow valves 52F R and 52F L forming the front right wheel hydraulic cylinder 12FR and the front left wheel hydraulic cylinder 12FL, respectively. The flow control valve 9 includes the above-mentioned inflow valve 52 and a discharge valve 53 interposed in the recirculation pipe 40F that returns the hydraulic fluid 44 to the reservoir tank 33. 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 (accumulated pressure by 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, for example, less than 40 kgf/cd. In other words, only when the main pressure is 40 kgf/cd or more, the hydraulic cylinder 1
It becomes possible to supply and discharge hydraulic oil to 2F R and 12F L.

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, there is also a relief valve 54FL in the high pressure piping 31FL for the left front wheel.

A hydraulic pressure gauge 55FL is provided. Relief valve 54FR
, 54FL open when the internal pressure of the hydraulic cylinders 12F R, 12F L increases abnormally, and return the hydraulic fluid 44 to the reflux pipe 40F. In this recirculation passage 40F, there is a return akinimulator 5 which performs a pressure accumulating function when the hydraulic fluid 44 is discharged from the hydraulic cylinders 12F R, 12F L.
9F is installed.

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 is interposed. The operation of this unload valve 43 is controlled by a control unit 45 (see FIG. 1) that receives the output from the oil pressure gauge 38, and the main pressure is controlled to a predetermined upper limit value (140 or 160 kgf/cd; this point will be described later). ) opens when the vane pump exceeds 3
2 is set to an unloaded state, and this state is maintained until the main pressure becomes equal to or less than a predetermined lower limit value (for example, 120 kgf/c).

When the main pressure falls below the lower limit, the control unit 45 closes the unload valve 43 and the vane pump 3
2 is in the loading state. Thereby, the main pressure increases to the above upper limit value. In this way, the main pressure is within a predetermined range (12
0 to 140 or 160 kg f /cd).

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 check valves 50F R and 50 are provided in the pilot passage 39F when the fail-safe valve 4B is opened.
A throttle 51F is provided to delay the closing operation of F.L.

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 that detects sprung acceleration for each wheel 10FR, 10FL, 10RR, 10RL, and a vehicle height sensor 58 that detects the vehicle height (i.e. cylinder stroke) for each wheel 10FR1], OFL, 10RR, 10RL, A lateral acceleration sensor 61 that detects lateral acceleration applied to the vehicle body 11, a vehicle speed sensor B2, and an engine 8
The output of the water temperature sensor 63 that detects the cooling water temperature of
(Only those corresponding to the above are shown).

The control unit 45 includes oil pressure gauges 5 for each wheel.
5. Vertical acceleration sensor 57 for each wheel, vehicle height sensor 58,
The supply and discharge of the hydraulic fluid 44 is controlled based on the cylinder internal pressure, sprung mass acceleration, 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 determining the above-mentioned main pressure holding range will be described. Figure 3 shows the control unit 4.
5 shows the flow of this process. As shown,
In step P1, the control unit 45 receives the output of the water temperature sensor 83 and determines the engine cooling water temperature Th.
monitor.

Next, in step P2, the control unit 45 determines whether the engine coolant temperature Th is equal to or lower than a predetermined set value Tho. If not, the engine 80 is warmed up and the control unit 45
In Step P5, the main pressure lower limit value for closing the unloading valve 43 to put the vane pump 32 in the loaded state is set to 120 kgf/C-, and then opens the unloading valve 43 to put the vane pump 32 in the unloading state. The main pressure upper limit for this purpose is set to 180 kgf/c-. Thus, in this case the main pressure is 120-16
It is maintained in the range of 0 kg f /c-.

On the other hand, when the engine coolant temperature Th is below the set value Th0, the control unit 45 performs step P.
In step 3, it is determined whether the vehicle speed V indicated by the output of the vehicle speed sensor 62 is approximately zero, that is, whether the vehicle is at a standstill or in a state close to it. If not,
In other words, when the vehicle is running normally, the processing flow moves to step P5, where the main pressure is 120 to 160 kg.
It is held in the f/cd range WJ.

On the other hand, when the vehicle speed V is approximately zero, the control unit 45 sets the main pressure lower limit value to 120 kg f /c-, and sets the main pressure upper limit value to 140 kg f /cj in step P4. Set to . In other words, in this case, the main pressure is 120 to 140 kg.
It is maintained within the f/cd range.

By correcting the main pressure upper limit value to a value lower than that when the vehicle is running in this way, the vane pump 32 can be set to the unloaded state more quickly.

Therefore, in many cases, the vane pump 32 is in an unloaded state by the time the vehicle starts, the engine load is reduced, and the starting performance is not impaired.

Moreover, if the pressure accumulation in the accumulator 37 is terminated sooner, the load on the engine 80 will be reduced, and the idling state will be stabilized more quickly.

In addition, in the embodiment described above, the process of correcting the main pressure upper limit value when the vehicle is stopped to a value lower than that when the vehicle is running is performed because the starting performance of the vehicle is likely to be impaired and the idling state is unstable. Although this correction process is performed only when the engine is cold, when the engine temperature is more likely to change, this correction process may be performed all the time, not only when the engine is cold.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a suspension device according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing a hydraulic circuit used in the suspension device, and FIG. 3 is a working fluid diagram in the device of the embodiment. It is a flow chart which shows control processing of pressure accumulation. 10... Wheels 11... Vehicle body 12...
・Hydraulic cylinder 13...Piston 14...Hydraulic pressure chamber 15 of the hydraulic cylinder 15...Piston rod 18...Hydraulic pressure passage 21
...Gas spring 31...High pressure piping 32...
・Pump 37.59...Accumulator 38.55...Hydraulic pressure gauge 39...Pilot passage 40...Recirculation passage 43...Unload valve 44...Hydraulic oil 45...Control unit 48 ... Failsafe valve 52 ... Inflow valve 53 ... Outflow valve 57 ... Vertical acceleration sensor 58 ... Vehicle height sensor 61 ... Lateral acceleration sensor 62 ... Vehicle speed sensor 63 ... Water temperature sensor 80...Engine

Claims (1)

[Claims] (1) A hydraulic cylinder installed between the vehicle body and the wheels,
In high pressure lines connected to the hydraulic chambers of these hydraulic cylinders, an accumulator that accumulates pressure of working fluid, a pump that is driven by the engine and pumps the working fluid to the accumulator, and an operating state of the pump that is connected to the accumulator. switching means that sets the accumulator to a load state in which the internal pressure is increased when the internal pressure has decreased to a predetermined lower limit value, and to an unload state in which the internal pressure is not increased when the accumulator internal pressure has increased to a predetermined upper limit value; A suspension system for a vehicle comprising a controller for controlling supply and discharge, comprising: means for detecting vehicle speed; 1. A suspension device for a vehicle, comprising a correction means for correcting the value to a value smaller than the value of . (2) The suspension device for a vehicle according to claim 1, wherein the correction means is configured to perform the correction only when the engine is cold.