KR940010621B1 - Safety device for a suspension system - Google Patents

Abstract

The fail safe apparatus is made for a small-size and easy to get assembled in the automobile engine room by equipping an electronic pressure-proportional relief valve actuating within a little flow range. The fail safe apparatus comprises a throttle valve (10) controlling the flow in oil supply lines (Ls1,Ls2); a 2-port-2 position type throttle valve (20) controlling the flow in oil feedback lines (Lr1,Lr2); a relief valve (30) controlling the throttle valve (10); another relief valve (40) controlling the throttle valve (20); orifices (50,60) positioned between oil inlets of the relief valves (30,40); a check valve (70) checking the flow in the oil feedback line (Lr1).

Description

Safety device for active control suspension system of vehicle

FIG. 1 is a schematic diagram showing a phenomenon in which a vehicle body of a vehicle using a common suspension device is tilted. FIG. 1a shows a dive phenomenon caused by inertia force during sudden braking, and FIG. FIG. 1C illustrates a rolling phenomenon caused by centrifugal force during sudden curve.

2 is a schematic diagram of a conventional active controlled suspension system.

3 is a partial schematic diagram of a conventional active controlled suspension system.

4 is a view showing an operating state of a safety device for a conventional active control suspension system, FIG. 4a is a hydraulic system diagram in a normal operation state, FIG. 4b is a hydraulic system diagram in which an abnormality or a vehicle is stopped and the vehicle is turned off, 4c is a hydraulic system diagram showing a process of returning to a normal operating state after an abnormality occurs.

5 is a hydraulic system diagram of a safety device for an active controlled suspension system according to the present invention.

6 is a view showing an operating state of a safety device for an active control suspension system according to the present invention. FIG. 6a is a hydraulic system diagram during normal driving, and FIG. 6b is a hydraulic system diagram in which an abnormality or a vehicle is stopped and the vehicle is turned off. 6C is a hydraulic system diagram illustrating a process of returning to a normal operating state after an abnormality occurs.

7 is a characteristic diagram of an electromagnetic proportional pressure reducing valve for pilot pressure control used in the apparatus of the present invention.

8 is a schematic cross-sectional view of a cartridge type throttling valve of the present invention.

* Explanation of symbols for main parts of the drawings

3: Accumulator 3: Electronic proportional pressure reducing valve

5: hydraulic pump 7: oil tank

10: oil supply side throttle valve 20: oil return side throttle valve

30,40: Electromagnetic proportional pressure relief valve 50,60: Orifice

70: check valve

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic device for an active control suspension system of a vehicle, and more particularly, to a fail-safe device for an active control suspension system for a vehicle, in which the size of the hydraulic device is reduced in size and thus easily mounted on the vehicle. will be.

Suspension device of a typical vehicle is composed of a coil spring and a shock absorber (Shock Absorber) has a function to block the vibration is not transmitted to the vehicle body when the wheel vibrates due to the curvature of the road surface when driving.

The ride comfort and adjustment stability of the vehicle to which the general suspension system is applied are determined by the link structure of the suspension system, the weight and elasticity of the tire, the weight of the vehicle body, as well as the elastic coefficient of the coil spring and the vibration damping coefficient of the shock absorber.

In general, the elastic modulus of the coil spring is determined according to the required natural frequency of the suspension system given the weight of the body.

However, in the shock absorber, when the vibration damping coefficient is increased, the tilting of the vehicle body due to the dynamic change of the inertia or centrifugal force is reduced, but the riding comfort is worsened. On the contrary, when the vibration damping coefficient is lowered, the riding comfort is improved but the dynamic force of external force It is very difficult to find suitable design conditions that can satisfy both the ride comfort and the adjustment stability because the tilting of the vehicle increases due to the change of the vehicle body.

That is, in such a conventional suspension system, when an external force such as an inertial force or a centrifugal force is applied to the vehicle body while driving, the coil springs are deformed by the change of the load acting on each wheel, and the vehicle body is oriented in the direction in which the external force acts as the first degree.

And ride comfort itself depends on road conditions, speed, tire weight and elasticity. FIG. 1a illustrates a dive phenomenon in which the vehicle body is moved forward by an inertia force forward when braking the vehicle. FIG. FIG. 1c illustrates a rolling phenomenon in which the vehicle body is pulled outward by a centrifugal force directed outward during a sharp curve.

In order to solve such problems in the conventional general suspension system, an active controlled suspension system has recently been devised.

FIG. 2 shows the whole system as an example of such an active controlled suspension system, and FIG. 3 shows only one wheel of four wheels.

As shown in FIGS. 2 and 3, the active-controlled suspension system suspends each wheel W together with the coil spring S with the hydraulic cylinder 1, and the hydraulic cylinder 1 A damping valve 2 and a sub accumulator 3 are sequentially connected to the upper end, and a hydraulic pump is provided between the upper end of the hydraulic cylinder 1 and the damping valve 2 through an electromagnetic proportional pressure reducing valve 4. This is by connecting the oil supply line connected to (5).

The hydraulic cylinder 1 is fixed to the vehicle body and supports the first rod 1b on the wheels W. As shown in FIG.

The gas chamber 3a is formed on the accumulator 3.

6 and 6 are pressure relief valves, C is an oil cooler, and F is an oil filter.

The electromagnetic proportional pressure reducing valve 4 connects the oil supply port P ₁ to the hydraulic pump 5 through the main accumulator Am and the pressure relief valve 6, and connects the oil return port P ₃ to the oil. In addition to connecting to the tank (7) is to connect the oil discharge port (P ₂ ) to the upper end of the hydraulic cylinder (1).

The oil supply ports P ₁ and the oil discharge ports P _{2 of} the electromagnetic proportional pressure reducing valves 4 corresponding to the respective wheels W are connected in parallel to the hydraulic pump 5 and the oil tank 7, respectively.

The electromagnetic proportional pressure reducing valve 4 is controlled by an electronic control unit (ECU) installed for each wheel (W) to determine the characteristics of the suspension system.

That is, when the electronic control unit ECU operates the electromagnetic proportional pressure reducing valve 4 to increase the pressure of the oil supplied to the hydraulic cylinder 1, the height of the vehicle body increases, and conversely, the oil supplied to the hydraulic cylinder 1 is increased. As the pressure decreases, the height of the body decreases.

In this case, if the entire load of the vehicle body is suspended only by the hydraulic cylinder, excessive power is required, so that the coil spring shares 50-70% of the body load by using the existing coil spring, and the hydraulic cylinder shares only the rest.

The suspension force of the hydraulic cylinder 1, that is, the pressure of the oil in the hydraulic cylinder 1, is input to the electromagnetic proportional pressure reducing valve 4 from an electronic control unit (ECU) which detects the attitude and vibration state of the vehicle body using various sensors. Is determined by electrical signals.

Therefore, in such an active control suspension system, the height between each wheel (W) and the vehicle body can be independently controlled by an independent hydraulic cylinder with an electric signal, so the roll angle, pitch angle, and horizontal garage height of the vehicle body can be independently controlled. (車 高) has the advantage that can be set arbitrarily.

In addition, as shown in the figure, the acceleration sensor Sa attached to the vehicle body on each wheel W measures the absolute acceleration in the vertical direction of the vehicle body, and converts it into a negative polarity velocity signal by electrical direct processing. When a vibration damping signal proportional to this signal is inputted to the electromagnetic proportional pressure reducing valve 4, a consistent vibration damping characteristic is not affected by road conditions, running conditions, tire weight, elasticity, or the like.

However, in order to control the attitude or vibration of the vehicle body up to a high frequency band by adjusting the pressure of the hydraulic cylinder 1 using the electromagnetic proportional pressure reducing valve 4, a very high flow rate must be supplied from the hydraulic pump 5, Considering the engine power and fuel economy, there is no practical use because there is a limit to the power that can be consumed in the suspension system.

Therefore, in the active control suspension system such as the second diagram, the capacity of the hydraulic pump 5 is adjusted so that the electromagnetic proportional pressure reducing valve 4 can control the pressure of the hydraulic cylinder 1 to about 1 to 2 Hz. The vibration of the frequency higher than this is set by the damping valve 2 of the same principle as the existing shock absorber.

That is, when the piston rod 1b connected to the wheel W receives the force from the wheel W to move upward at a high speed, the oil in the hydraulic cylinder 1 passes through the damping valve 2 of the accumulator 3. The gas chamber 3a is introduced into the auxiliary accumulator 3 while compressing the gas chamber 3a.

At this time, since the pressure difference is generated in the damping valve 2 in proportion to the flow rate of the oil, the pressure in the hydraulic cylinder 1 rises so that the resistive force (vibration damping force) proportional to the rising speed of the piston 1a acts on the piston 1a. do.

On the contrary, even when the piston 1a moves downward, vibration damping force proportional to the descending speed of the piston 1a is generated.

In addition, an accumulator (Am) is installed in the middle of the oil supply line to maintain a constant pressure of the oil supplied from the hydraulic pump (5) to the electromagnetic proportional pressure reducing valve (4) without ripple and for a short period of time. High flow rate can be supplied.

The pressure relief valve 6 bypasses the remaining flow rate to the oil tank when the hydraulic cylinder 1 or the accumulator Am does not consume the entire flow rate supplied from the pump. It is prevented from rising above the maximum pressure set with).

The pressure relation at each port of the electromagnetic proportional pressure reducing valve 4 is, as shown in Fig. 4, when the electrical signal, that is, the current signal I is input to the proportional solenoid 4a, the pressure of the oil discharge port P ₂ ( Pa) is set to a size proportional to the current input signal.

This pressure settable range is determined by the pressure Pp of the oil supplied to the oil supply port P ₁ and the pressure Pt of the oil return port P ₃ .

However, in such an active control suspension system, when an abnormality occurs in the electronic control unit (ECU) or the electromagnetic proportional pressure reducing valve (4), or the engine is stopped for the purpose of stopping the operation, the oil from the hydraulic pump (5) is not supplied. If not, there is a fear that the vehicle body falls as the pressure in the hydraulic cylinder (1) drops.

Therefore, in an active control suspension system, when an error occurs in the electronic control unit (ECU) or the electromagnetic proportional pressure reducing valve (4) or the like, or the engine is stopped for the purpose of stopping the operation, the oil from the hydraulic pump (5) cannot be supplied. When an electric signal is applied from the outside, the flow path between the hydraulic pump 5 and the accumulator Am is quickly shut off, and the operating pressure in the hydraulic cylinder 1 is increased to a neutral position by using the oil accumulated in the accumulator Am. It is required to install a separate stabilizer in the flow path between the hydraulic pump (5) and the proportional pressure reducing valve (4) to automatically return to the pressure maintained by the pressure maintained until the repair or restarting operation.

Figure 4 illustrates a conventional safety device, a throttling solenoid valve SV ₁ and a pressure maintaining solenoid controlled by an electronic control unit (ECU) between the electromagnetic proportional pressure reducing valve 4 and the hydraulic pump (5). When the valve SV ₂ is installed and in normal operation, the throttle solenoid valve SV ₁ switches to a state in which oil from the hydraulic pump 5 is smoothly supplied to the electromagnetic proportional pressure reducing valve 4 side, and the pressure maintaining solenoid The valve (SV ₂ ) smoothly supplies oil passing through the throttle solenoid valve (SV ₁ ) to the electromagnetic proportional pressure reducing valve 4 side, and at the oil return port (P ₃ ) of the electromagnetic proportional pressure reducing valve (4). The oil returning to the (7) side is switched so that the oil can be smoothly returned to the oil tank (7) side, and when the abnormality occurs in the electronic proportional pressure reducing valve (4) or the like, the engine is stopped for the purpose of stopping operation. Oil from 5) When not supplied, the throttle solenoid valve (SV ₁ ) remains in the same state as the normal driving state, and the pressure holding solenoid valve (SV ₂ ) is fed back from the oil return port (P ₃ ) of the proportional pressure reducing valve (4). It is installed to be converted to reflux the oil back to the oil supply port (P ₁ ) side.

Here, the throttle solenoid valve SV ₁ uses a two-port two-position valve having a straight supply flow path SV ₁ a having an orifice O ₁ interposed therebetween and a simple straight supply flow path SV ₂ b. Install a straight supply flow path (SV ₁ a) (SV ₁ b) to selectively match between the oil supply upstream line (Ls ₁ ) and the oil supply downstream line (Ls ₂ ).

The pressure maintaining solenoid valve SV ₂ has a simple straight supply flow path SV ₁ a, a simple straight return flow path SV ₂ b, a shutoff port SV ₂ c, and a reflux flow path SV ₂ d. By using the port 2-position valve, the shutoff port (SV ₂ c) is installed on the downstream side of the oil supply upstream line (L ₁ ) and the oil return second branch line (Lr ₄ ), and the return flow path (SV ₂ d) is The oil supply downstream line (Ls ₂ ) and the oil return upstream line (Lr ₁ ) is installed to communicate with each other.

The oil return upstream line (Lr ₁ ) and the oil return downstream line (Lr ₂ ) between the oil return first branch line (Lr ₃ ) and the oil return second branch line (Lr ₄ ) in parallel, the oil return agent Orifice (O ₂ ) is installed in one branch line (Lr ₃ ), and pilot check valve (CV) is installed in oil return downstream line (Lr ₂ ).

The pilot line Lp of the pilot check valve CV is connected to the oil supply downstream line Ls ₂ .

When the safety device for the active control suspension system of such a vehicle is operated, in normal operation, as shown in FIG. 4A, the throttle solenoid valve SV ₁ does not receive the control signal of the electronic control device ECV and is driven by its own spring. It is maintained in the returned state, the pressure maintaining solenoid valve (SV ₂ ) is a state in which the control signal of the electronic control unit (ECU) is input and moved with respect to its own spring.

That is, the throttling solenoid valve SV ₁ operates at a position where the simple straight supply flow path SV ₁ b corresponds to the oil supply downstream line Ls ₂ , and the pressure maintaining solenoid valve SV ₂ , also has a simple straight supply. The flow path SV ₂ a is operated at a position coinciding with the oil supply downstream line Ls ₂ so that oil from the hydraulic pump 5 flows straight through the throttle solenoid valve SV ₁ in the oil supply upstream line Ls ₁ . It is supplied to the oil supply port (P ₁ ) of the proportional pressure reducing valve (4) through a simple straight supply passage (SV ₂ a) of the supply passage (SV ₁ a) and the pressure holding solenoid valve (SV ₂ ), where the oil It is supplied to the upper portion of the hydraulic cylinder (1) through the discharge port (P ₂ ).

On the other hand, the oil returning from the oil return port (P ₃ ) of the electromagnetic proportional pressure reducing valve (4) is a simple straight return flow path (SV ₂ b) and pilot check valve (CV) of the pressure holding solenoid valve (SV ₂ ) Through the return to the oil tank 7, the resistance is minimized.

At this time, the accumulator Am is charged to the maximum pressure Pmax.

In such a normal operation state, when the ECU or the electronic proportional pressure reducing valve 4 is abnormal or the vehicle is stopped and the engine is turned off, the throttle solenoid valve SV ₁ still remains as shown in FIG. 4B. Since the control signal of the electronic control unit (ECU) is not inputted, it is maintained in the same state as in normal operation, and since the control signal from the electronic control unit (ECU) is not input to the pressure holding solenoid valve (SV ₂ ), The return port (SV ₂ c) blocks the oil supply upstream line (Ls ₁ ) and the oil return second branch line (Ls ₄ ) and the reflux flow path (SV ₂ d) is the oil supply downstream line. (Ls ₂ ) and the oil return upstream line (Lr ₁ ) is connected to each other so that oil returned from the oil return upstream line (Lr ₁ ) is not returned without flow resistance.

That is, the oil supply port P ₁ and the oil return port P _{3 of the} electromagnetic proportional pressure reducing valve 4 are connected to each other.

At this time, since the orifice (O ₂ ) is installed in the oil returning first branch line (Lr ₃ ) connected to the oil returning upstream line (Lr ₁ ), the oil returned from the oil returning upstream line (Lr ₁ ) is orifice (O ₂ ). In the process of passing through the flow resistance is gradually returned to the oil tank (7) through the pilot check valve (CV).

In this process, the pilot check valve CV sets the pilot operating pressure to half of the maximum pressure Pmax, that is, 0.5 Pmax, so that the pressure inside the hydraulic cylinder 1 and the pressure in the accumulator Am are 0.5. The oil is returned to the oil tank 7 until Pmax is reached.

When the pressure of the hydraulic cylinder 4 and the accumulator Am is 0.5Pmax or less, the pilot check valve CV blocks the return of oil and no longer allows the return of oil.

Therefore, the pressure of the hydraulic cylinder 4 and the pressure of the accumulator Am are maintained at 0.5 Pmax so that the vehicle body does not fall down.

In this case, the pressure of 0.5 Pmax corresponds to the pressure that can support the vehicle body not to fall down.

Additionally, this condition the engine is continues to operate even if a pressure of the hydraulic pump 5, the maximum pressure (Pmax), the oil feed upstream line (Ls ₁₎ blocked port of the solenoid valve (SV ₂₎ for holding the pressure (SV ₂ c) The pressure of the hydraulic cylinder 4 and the accumulator Am is kept at 0.5 Pmax since it is shut off by the.

When the troubleshooting is completed or the vehicle is restarted in such an emergency state, as shown in FIG. 4C, the pressure maintaining solenoid valve SV ₂ is returned to the normal operation state under the control signal of the electronic control unit ECU. In addition, the throttle solenoid valve (SV ₁ ) receives the control signal from the electronic control unit (ECU), and the straight supply flow path (SV ₁ a) in which the orifice (O ₁ ) is installed coincides with the oil supply upstream line (Ls ₁ ). The oil from (5) is supplied to the electromagnetic proportional pressure reducing valve 4 side through the simple straight supply flow path SV ₂ a of the pressure holding solenoid valve SV ₂ .

At this time, since the oil passes through the orifice O ₁ installed in the straight supply flow path SV ₁ a of the throttle solenoid valve SV ₁ , the maximum pressure Pmax of the oil supplied from the hydraulic pump 5 is increased. The pressure of the hydraulic cylinder 1 and the accumulator Am, which was maintained at 0.5 Pmax while being supplied gradually without being supplied directly to the electromagnetic proportional pressure reducing valve 4 side, is gradually raised to the maximum pressure Pmax.

Therefore, while preventing the severe vibration of the vehicle body caused when the pressure of the hydraulic cylinder (1) is raised rapidly, it is gradually converted to the normal operating state.

However, such a stabilizer for an active control suspension system of a conventional vehicle requires the installation of a throttle solenoid valve (SV ₁ ), a pressure maintaining solenoid valve (SV ₂ ), a pilot check valve (CV), and an orifice (O ₂ ). In addition, since the orifice (O ₁ ) must be installed in the straight supply flow path (SV ₁ a) of the throttle solenoid valve (SV ₁ ), there is a problem in that the size of the whole becomes large due to the large number of valve elements. Given the trend that the space of the engine room is gradually narrowed, there was a problem such as difficulty in mounting to the vehicle.

The object of the present invention is to simplify the structure and to fully function as a safety device, the electronic proportional pressure relief valve for controlling the pilot pressure of the throttle valve can be reduced in size because it operates only in a small flow range. The overall device can be miniaturized, and accordingly, a safety device for an active control suspension system of a vehicle has been provided so that the vehicle can be easily mounted in an engine room that is being gradually miniaturized.

In order to achieve the object of the present invention, each wheel is suspended by a hydraulic cylinder, and a damping valve and an accumulator are sequentially installed at an upper end of the hydraulic cylinder, and an electronic proportional pressure reducing valve is provided between the upper end and the damping valve of the hydraulic cylinder. In the connection of the oil supply line connected to the hydraulic pump, the oil supply side throttling valve to control the oil supply phase, the downstream line connected to the oil supply port of the electromagnetic proportional pressure reducing valve, the oil return upstream line and the oil return downstream line A two-port two-position pilot controlled throttling valve for intermittent operation and an electronic proportional pressure relief valve and an oil proportional control for oil supply side control which are connected directly to the oil supply downstream line and oil return downstream line to operate the throttle valve. The pressure relief valve and the oil inlet side of the oil supply downstream line An electronic proportional pressure relief valve for oil supply side control connected to the oil outlet side and the oil outlet side to the oil return downstream line, and the oil inlet side to the oil airflow downstream line and the pilot end of the throttle valve, and the oil outlet side An oil proportional pressure relief valve for oil return side control connected to an oil return downstream line, an orifice installed between the oil supply downstream line Ls ₂ and the oil inlet side of the electromagnetic proportional pressure relief valve, and the oil supply downstream line And a check valve installed between the oil return upstream line and the oil return upstream line, the safety device for the active control suspension system of the vehicle is provided.

Hereinafter, a safety device for an active control suspension system for a vehicle according to the present invention will be described in detail according to an embodiment shown in the accompanying drawings.

In the following description, the same parts as in the conventional construction are denoted by the same reference numerals, and parts not shown will be described with reference to FIGS. 2 and 3.

FIG. 5 is a hydraulic system diagram of the safety device for an active control suspension system according to the present invention, and FIG. 6 is a view illustrating an operating state of the safety device for an active control suspension system according to the present invention. FIG. 5C illustrates a process of returning to a normal operation state after the occurrence or stopping of driving of the vehicle and turning off the ignition.

As shown in FIG. 5, a safety device for an active control suspension system of a vehicle of the present invention includes an electromagnetic proportional pressure reducing valve 4, a hydraulic pump 5, and oil for adjusting the operating pressure of the hydraulic cylinder 1; Install a 2-port 2-position pilot controlled throttling valve (10) intermittent between the oil supply upstream line (Ls ₁ ) and the oil supply downstream line (Ls ₂ ) connecting the tank (7), and the oil return upstream line (Lr). ₁₎ and the oil return downstream line (Lr _2), and installing the two-port 2-position pilot-controlled throttle valve 20 to regulate between the oil supply-side control electronics for operating those pilot-controlled throttle valve 10 (20) The proportional pressure relief valve 30 and the oil proportional pressure relief valve 40 for oil return side control are connected to the oil supply downstream line Ls ₂ and the oil return downstream line Lr ₂ , respectively.

The throttling valves 10 and 20 use a cartridge type as shown in FIGS. 6A, B, C and 8.

As illustrated in FIG. 8, the throttling valves 10 and 20 have a ratio of 1: 2 to 1: 2.5 in a ratio between the piston inlet area A ₂ and the back pressure side area A ₁ .

This assumes that the pressure of the hydraulic cylinder (1) to maintain the height of the body is 0.5Pmax, the pressure of the accumulator (Am) should be 0.5Pmax when the action to prevent the body from falling down In order to be able to keep the throttle valve 10 in which the pressure Pmax acts on the piston inlet area A ₂ by using this pressure, the back pressure side area A ₁ of the piston 11 of the throttle valve 10 can be kept closed. ) Should be at least 2 to 2.5 times the inlet area (A ₂ ).

The throttle valve 20 may have the same shape as the throttle valve 10 so that the same component as the throttle valve 10 may be used.

The electromagnetic proportional pressure relief valves 30 and 40 receive oil from the accumulator Am for applying pilot pressure to the throttling valves 10 and 20 as shown in FIG. When is added, the control pressure (P ₁ ) (P ₂ ) is lowered.

The electromagnetic proportional pressure relief valve 30, 40 is controlled by an electronic controller (not shown; see FIG. 3).

Electro-proportional pressure relief valves 30 and 40 are connected in parallel with the oil inlet side to the oil supply downstream line Ls ₂ to install orifices 50 and 60 in the middle thereof, as well as to control the oil supply side. The oil inlet side of the pressure relief valve 30 is connected to the pilot end of the pilot controlled throttling valve 10 for controlling the oil supply line, and the oil inlet side of the electromagnetic proportional pressure relief valve 40 for oil return side control is oil return. It is connected to the pilot end of the pilot-controlled throttling valve 20 to interrupt the line.

The oil outlet side of the electromagnetic proportional pressure relief valves 30 and 40 is connected in parallel to the oil return downstream line Lr ₂ .

A check valve 70 is installed between the oil supply downstream line Ls ₂ and the oil return upstream line Lr _{1 to} check the oil return upstream line Lr ₁ .

In the figure, 1 is a hydraulic cylinder, 3 is an accumulator, and 6 is a pressure relief valve. Hereinafter will be described the operation of the safety device for the active control suspension system of the vehicle of the present invention.

During normal operation of the vehicle, the inlet pressure Pp of the throttle valve 10 is maintained at the allowable maximum pressure Pmax set by the pressure relief valve 6, and the rated current is applied to the electromagnetic proportional pressure relief valves 30 and 40. When Imax is applied, the back pressure P ₁ and P ₂ acting on each throttling valve 10 and 20 are maintained at "0" bar, so the two throttling valves 10 and 20 are completely open and the hydraulic pump The oil supply upstream line (Ls ₁ ), the oil supply downstream line (Ls ₂ ) and the oil proportional pressure reducing valve (4), which are oil passages from which oil is supplied to the oil supply port P ₁ of the electromagnetic proportional pressure reducing valve (4) from (5). The oil return upstream line (Lr ₁ ) and the oil return downstream line (Lr ₂ ), which are oil return paths from the oil return port (P ₃ ) of the tank to the oil tank (7), are formed without flow resistance and accumulator (Am). ) Is filled to the maximum allowable pressure Pmax.

Therefore, the suspension action by the hydraulic cylinder (1) is to be made normally.

On the other hand, when an abnormality occurs in the electronic control unit (ECU) or the electronic proportional pressure reducing balance 4 during the normal operation of the hydraulic system, or when the engine is shut down by stopping the vehicle, the electronic diagnostic unit (ECU) diagnoses the error. When the current signal input to the electromagnetic proportional pressure relief valve 30, 40 from the electronic control unit (ECU) by "off" as shown in FIG. 6b, at the same time the back pressure acting on each throttling valve (10) (20) As shown in FIG. 7, the throttling valves 10 and 20 are forcibly closed by the back pressures P ₁ and P _{2 so} that the oil supply port P of the electromagnetic proportional pressure reducing valve 4 from the hydraulic pump 5 can be closed. ₁ ) oil is transferred from the oil return phase (Ls ₁ ) (Ls ₂ ) and the oil return port (P ₃ ) of the proportional pressure reducing valve (4) to the oil tank (7). the oil phase forming the feedback induced that is fed back, the downstream line (Lr ₁₎ (Lr ₂₎ is completely blocked, eokyu The oil tank (7) passes through the proportional pressure relief valves (30) and (40) in which oil is set to 0.5 Pmax through the orifice (50) or (60) until the filling pressure of the oscillator Am is 0.5 Pmax. Part with)

When the downstream line (Lr ₁ ) (Lr ₂ ) is rapidly blocked, the inflow of oil flows back from the oil return port (P ₃ ) of the electromagnetic proportional pressure reducing valve (4) to the oil tank (7). The oil is absorbed into the accumulator Am through the check valve 70 so that no pressure shock occurs.

In this state, the engine continues to operate so that the engine stops operating whether the inlet pressure of the oil supply side throttling valve 10 is the maximum allowable pressure Pmax and is charged to the accumulator Am whether the inlet pressure is "0". The throttle valves 10 and 20 are kept closed by the oil pressure Ps.

Here, in order for the filling pressure of the accumulator Am to be maintained at 0.5 Pmax, the throttling valves 10 and 20 should have good sealing properties. In the present invention, the throttling valves 10 and 20 should be used to improve the sealing performance. Use cartridge type throttling valves.

When the troubleshooting is completed or the vehicle is restarted in such an emergency state, the oil supply side is inputted to the electromagnetic proportional pressure reducing valve 4 after inputting a current signal Ineutral having a magnitude such that the height of the vehicle body maintains the neutral position as shown in 6c. Open the throttling valve 10 and the oil return side throttling valve 20 at the same time, and the oil discharged from the hydraulic pump 5 gradually discharges the oil supply port P ₁ and the accumulator Am of the proportional pressure reducing valve 4. The operating pressure reaches the maximum allowable maximum pressure Pmax and gradually increases the amount of current input to the electromagnetic proportional pressure relief valve 30 so that the vehicle body does not shake violently, thereby gradually opening the oil supply side throttling valve 10. .

As described above, according to the present invention, two cartridge type throttling valves which are structurally simple and have good sealing properties are installed on the oil supply side and oil return side, and the oil supply side and the oil return side by the electronic proportional pressure relief valve controlled by the electronic controller. Since the throttling valve can be controlled steplessly, the structure can be simplified and can fully function as a safety device.The electronic proportional pressure relief valve that controls the pilot pressure of the throttling valve operates only in a small flow range. Therefore, the size can be downsized, so that the overall device can be downsized, thereby making it easier to mount the engine room of the vehicle which is gradually downsized.

The present invention is not limited to the above-described embodiment, and various modifications are possible by those skilled in the art within the spirit and scope of the present invention.

Claims (2)

Suspension of each wheel (W) with a coil spring (S) to the hydraulic cylinder (1), and the damping valve (2) and accumulator (3) in order to install the upper end of the hydraulic cylinder (1), the hydraulic cylinder The oil supply line of the electromagnetic proportional pressure reducing valve 4 is connected between the upper end of the (1) and the damping valve (2) by connecting the oil supply line connected to the hydraulic pump S through the electromagnetic proportional pressure reducing valve (4). Oil supply side throttling valve 10 for intermitting the oil supply phase, downstream line (Ls ₁ ) (Ls ₂ ) connected to the port (P ₁ ), oil return upstream line (Lr ₁ ) and oil return downstream line (Lr ₂₎ A two-port two-position pilot controlled throttling valve (20) intermittent between the throttle valve (10) and the oil supply downstream line (Ls ₂ ) and the oil return downstream line (Lr ₂ ), respectively; The electromagnetic proportional pressure relief valve 30 for oil supply side control and the electromagnetic proportional pressure relief valve 40 for oil return side control Electromagnetic proportional pressure relief valve for oil supply side control where the oil inlet side is connected to the oil supply downstream line Ls ₂ and the pilot end of the throttling valve 10 and the oil outlet side is connected to the oil return downstream line Lr ₂ . 30 and the oil inlet side is connected to the oil supply downstream line (Ls ₂ ) and the pilot end of the throttle valve 20, and the oil outlet side is connected to the oil return downstream line (Lr ₂ ) Orifice 50 and 60 respectively installed between the electromagnetic proportional pressure relief valve 40, the oil supply downstream line (Ls ₂ ) and the oil inlet side of the electromagnetic proportional pressure relief valve 30, 40, and the And a check valve 70 installed between the oil supply downstream line Ls ₂ and the oil return upstream line Lr ₁ to check the oil return upstream line Lr ₁ toward the oil return upstream line Lr ₁ . Safety device for active control suspension system. 2. The safety device for an active control suspension system according to claim 1, wherein the throttling valve (10) is a cartridge type throttling valve.