JPH01193422A - Current control circuit for hydraulic suspension - Google Patents

Abstract

PURPOSE:To improve the riding comfortableness of a car by providing a phase advance circuit to compensate the lowering, which is caused by an orifice arranged between a pressure control valve and a suspension cylinder or a spring to control the movement of a spool of the pressure control valve, of the responsibility of the pressure control valve to an electric current. CONSTITUTION:An electric current control circuit 50 is additionally provided with a phase advance circuit 51. A target current I1 corresponding to a car running state is inputted through a capacitance 52 and a resistance 53 from an input terminal P into a differential amplifier 54. The current I1 is fed back through a resistance 55 from an output terminal of the amplifier 54 to its input end to form a phase advance circuit. An output current I3 having an advanced phase is inputted into a differential amplifier 59, and a current correspondent to the current I3 flows through a coil 8 of a solenoid, which is driven in the first order leading state. A current I2 flowing actually through the coil 8 is compared with the current I3 by the amplifier 59 to regulate the current flowing through the coil 8, and the current I3 having the advanced phase therefore coincides with the current I2 flowing actually through the coil 8.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a current control circuit that outputs a control current to a hydraulic suspension that actively controls a suspension cylinder using a pressure control valve.

(Prior Art) Conventionally, there is a hydraulic suspension that actively controls the posture of a vehicle, as disclosed in Japanese Patent Application Laid-Open No. 193910/1983. As the output current control circuit,
For example, the required target current I for the solenoid of a pressure control valve, and the solenoid current I2 that actually flows through the solenoid.
There is a circuit that adjusts the base current of a solenoid driving transistor or the gate voltage of a solenoid driving gate according to the deviation.

(Problem to be Solved by the Invention) However, in this type of conventional current control circuit, the input current (target current I+) and the output current (solenoid current I2) have a linear relationship with respect to frequency characteristics. As a result, the following problems arose. In other words, in a hydraulic suspension system that performs active control, the current input frequency characteristics shown in Fig. 6 are applied to the current human power generated from a controller (not shown) in order to suppress roll and pitch of the vehicle body and improve riding comfort. A1(
(gain) and A2 (phase) (ideally, the gain should be as large as possible and the delay in oil pressure change should be small, even for high-frequency currents). On the other hand, in order to control the vibration input from the road surface to the cylinder of the hydraulic suspension by feeding it back to the pressure control valve, it is necessary to
Characteristics shown in (pressure fluctuation gain) and Bg (phase) (Ideally, the pressure fluctuation gain is large regardless of frequency,
The smaller the phase shift, the better). Therefore, first, let's look at 8 in Figure 7. , In order to achieve the characteristics shown in B2,
For example, if an orifice is provided between the pressure control valve and the hydraulic suspension and pressure fluctuations caused when the hydraulic suspension cylinder is vibrated from the road surface are transmitted to the pressure control valve with a delayed phase, the characteristics shown in Figure 7 will be satisfied. , the characteristics shown in FIG. 6 deteriorate the current input frequency characteristics of the pressure control valve due to the orifice, resulting in undesirable characteristics shown by C1 (gain) and C2 (phase). Conversely, if the response to the current input of the pressure control valve is increased in order to achieve the characteristic indicated by AI+42 in Fig. 6, the characteristic shown in Fig. 7 will change to the pressure fluctuation gain in the low frequency range as shown in . In this case, the pressure regulating function of the pressure control valve based on the feedback pressure works too much, the pressure fluctuation gain decreases, and the phase with respect to the cylinder speed advances undesirably as shown by D2, resulting in a decrease in riding comfort. As described above, there was a problem in that the characteristics shown in FIGS. 6 and 7 could not be made good at the same time.

(Means for Solving the Problems) The present invention provides a current control circuit that solves these problems, and outputs a current for control to a hydraulic suspension that actively controls suspension cylinders using a pressure control valve. In the current control circuit, the pressure control valve is compensated for a decrease in responsiveness to the current caused by an orifice interposed between the pressure control valve and the suspension cylinder or a spring that suppresses movement of the spool of the pressure control valve. The present invention is characterized in that a phase advance circuit configured to do so is provided.

(Function) The current control circuit of the present invention is a conventional circuit with a phase lead circuit added, and this phase lead circuit is configured to have the phase characteristics shown in FIG. The cutoff frequency is approximately equal to the cutoff frequency on the phase characteristics of the pressure control valve. Therefore, by adding this circuit, it is possible to compensate for the difference between the characteristics of C2 and A2 in FIG. 6 regarding the current input frequency characteristics.

As a result, it is possible to improve ride comfort and improve performance regarding vehicle posture control and operational stability.

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

FIG. 1 is a diagram showing the overall configuration of a hydraulic suspension system using a current control circuit according to a first embodiment of the present invention. In the figure, 1 is a pump that supplies a pressure P to a pressure control valve 3 via an accumulator 2. The pressure control valve 3 includes a solenoid section 4, a pilot valve section 5, and a pressure reducing valve section 6.

The solenoid section 4 is provided with a plunger 7, a coil 8 wound around the plunger 7, and a case 9.

The plunger 7 is provided with an oil passage 10 communicating the left and right chambers, an orifice 11 located within the oil passage 10 for damping the plunger 7, and a bushing pin 12.

The coil 8 is provided with a harness 13, and the case 9 is provided with an air vent plug 14.

The pilot valve portion 5 is provided with a pilot spool 15. A circumferential groove 16 is provided around it, and a triangular bell-shaped groove (pilot port) 17 is provided at the left end in the figure.
The illustrated right oil chamber 41 is connected to the drain port 20 by an oil passage 18.19. The circumferential groove 16 is connected to a drain port 20 via an oil passage 21. The oil passage 18 is provided with an orifice 22 for adjusting the moving speed of the pilot spool 15, and the oil passage 19 is provided with an orifice 23 for adjusting back pressure to reduce the influence of pressure fluctuations in the drain port 20 on the pilot pressure P. It is.

The pressure reducing valve section 6 is provided with a main spool 25 within a valve body 24, a supply valve hole 26 of which is connected to a supply boat 27, and a drain valve hole 28 of which is connected to a drain boat 20, respectively.

A pilot chamber 29 whose pressure is regulated by a pilot valve is connected to the supply boat 27 by an oil passage 31 via an orifice 30 for adjusting flow rate. On the other hand, the reaction force chamber 32 is connected to a control boat 35 by an oil passage 34 via an orifice 33, and the control pressure PC is fed back.

The control pressure PC is led via an orifice 36 to a hydraulic suspension cylinder 37 by a hydraulic line 37.

Here, the hydraulic piping 37 is provided with a damping valve 39 and an accumulator 40 for absorbing pressure fluctuations in the high frequency range of vehicle sprung mass vibration.

Is 50 the pressure side? This is a current control circuit that controls the fll valve, and is connected to the harness 13 of the solenoid coil 8. This circuit has a phase lead circuit 51 added to the conventional circuit. That is, the phase advance circuit 51 includes a parallel circuit of a capacitor 52 and a resistor 53, one end of which is connected to the input terminal P, and a differential amplifier 5, one of the input terminals of which is connected to the other end.
4. Parallel circuit of resistor 55, resistor 56, and capacitor 5
The other input terminal of the differential amplifier 54 and the capacitor 57 are grounded. The output end of this phase lead circuit is connected to a differential amplifier 59 via a resistor 58.
is coupled to one input end of the . The other input end is connected to a junction between resistors 60 and 61, one end of which is grounded.

The output of differential amplifier 59 is coupled through resistor 62 to the base of transistor 630. Its emitter is connected to a junction between the other end of the resistor 61 and a resistor 64 whose one end is grounded, and its collector is connected to one side of the harness 13.

The other end of the harness 13 is connected to the positive potential side of the DC power supply 65. Next, the action of the hydraulic suspension will be explained.

Depending on the magnitude of the current output from the current control circuit 50 connected to the harness 13 to the solenoid coil 8, a thrust force proportional to the current value is generated in the plunger 7 in the left direction in the figure. In response to this thrust, the pilot spool 15 in contact with the bushing pin 12 moves in the left-right direction. The flow path area formed by the groove 17 of the pilot spool 15 changes depending on the amount of movement.

Oil at a pressure P flowing into the pilot chamber 29 from the supply port 27 through the oil path 31 flows into the groove 1 of the pilot spool 15.
7 and a part of it flows to the drain boat 20 via the circumferential groove 16 and the oil passage 21, so that the pilot chamber 2
The pressure P of 9 is set to a value according to the amount of movement of the pilot spool. The pilot spool 15 has a solenoid thrust with a pilot pressure P and a pilot spool cross-sectional area S1.
The pilot pressure P is regulated by the flow path area of the groove 17 at this time.

When the pilot pressure P becomes uniform and the main spool 25 moves to the left and the supply valve hole 26 opens, the supply boat 27 and the control boat 35 are connected and hydraulic pressure is supplied to the control boat 35. This hydraulic pressure Pc is supplied to a hydraulic suspension cylinder 38 via an orifice 36 and a hydraulic pipe 37. Further, the oil pressure P is applied to the oil passage 34 through the orifice 33.
is supplied to the pressure chamber 32 and moves the main spool 25 to the right. At this time, the main spool 25 is connected to the feedback control pressure PC and the main spool cross-sectional area S.
Since the control pressure PC stops when the product of 2 and 32 becomes equal to the product of the pilot pressure PP and 32, the control pressure PC is adjusted to be equal to the pilot pressure P.

On the other hand, when the vehicle body is vibrated from the road surface, the hydraulic suspension cylinder 38 applies hydraulic pressure to the control port 3 according to the excitation force.
Supply to 5. Here, the excitation force in a high frequency range such as sprung mass vibration is absorbed by the damping pulp 39 and accumulator 40 provided in the middle of the hydraulic piping 37, and the excitation force in a relatively low frequency range such as sprung mass vibration is absorbed. Regarding the vibration force, an orifice 36 is provided to delay the phase and the reaction force chamber 3
2.

This relationship is shown in FIG. 7 as D+, Dz (without orifice 36) and Bl, B2 (with orifice 36; target value). In this case, the current input frequency characteristic becomes C1+Ct in FIG. 6 with a current input similar to the conventional one, and becomes thicker (worsened) from the desired characteristic (target value) of A, , A.

In this embodiment, in order to compensate for the especially worsening phase characteristics from 02 to A2 in FIG. 6, a phase advance circuit 51 is added so that the current control circuit 50 has the frequency characteristics shown in FIG. 5.

The operation of this current control circuit 50 will be explained below.

First, a target current (1) corresponding to the vehicle condition is input from the input terminal P to the differential amplifier 54 via the capacitor 52 and the resistor 53. Since the current 11 is fed back from the output end of the differential amplifier 54 to the input end by the resistor 55, a phase lead circuit is formed. Note that the resistor 56 and capacitor 57 are used to stabilize operation in a high frequency range.

The phase-advanced output current I3 is input to a differential amplifier 59 via a resistor 58, and the output current is input to the base of a transistor 63 via a resistor 62. As a result, the base potential of the transistor 63 becomes higher than the emitter potential, and the transistor 63 becomes conductive, so that a current corresponding to the current I3 flows through the solenoid coil 8, and the solenoid is driven in a linear advance. Here, the current (2) actually flowing through the coil 8 can be detected as the terminal voltage of the resistor 64, so by connecting the resistor 64 and the input terminal of the differential amplifier 59 with the resistor 61, the differential amplifier 59 can be detected. Compare the currents I3 and It. As a result, the current flowing through the coil 8 is adjusted, and the target current I3 whose phase is advanced matches the actual current I2 flowing through the coil 8.

In this way, by compensating for the phase delay, the responsiveness of the control pressure PC to the current input can be improved as shown in A2 in FIG. 6, and the preferable characteristics shown in FIGS. 6 and 7 can be simultaneously satisfied. Very good active control of the hydraulic suspension is possible.

2 to 4 are diagrams showing the overall configuration of a hydraulic suspension system using current control circuits according to second to fourth embodiments of the present invention, and the same parts as in FIG. 1 are given the same reference numerals. It is.

In the second embodiment, instead of the orifice 36 of the first embodiment,
The pilot chamber 29 and reaction chamber 32 of the pressure control valve 3 are provided with springs 70 and 71, respectively, and the rest is the same as the first embodiment. Note that only one of the springs may be used.

With this configuration, the spring 70°71
Since the movement of the main spool 25 is obstructed by this, the responsiveness of the main spool 25 to changes in the pilot pressure P9 or the feedback pressure PC guided to the reaction force chamber 32 deteriorates. Therefore, the same effect as the addition of the orifice 36 in the first embodiment can be obtained.

In the third embodiment, the feedback pressure receiving area Af of the further north main spool 72 is made smaller than the pilot pressure receiving area sieve in the device of the second embodiment, and the set load of the spring is also made stronger on the feedback side (71). be.

With this configuration, the same effects as in the first embodiment can be obtained. Also, if the set loads of springs 70 and 71 are F, , F, respectively, the pilot pressure P
The relationship between p and control pressure PC holds true. This relationship is shown in FIG.

At this time, the control pressure PC is changed from 0 to P. In the conventional method (first embodiment), the pilot pressure P is changed from O to P. However, in this embodiment, it is sufficient to change it from P□ to P,2 in FIG. 8.

Pilot pressure P. There is a relationship between the amount of displacement χ of the pilot spool 16 and the amount of displacement χ of the pilot spool 16 as shown in FIG. The amount of displacement is also
This means that it is sufficient to control within the range from 2 to Xl. In this case, the characteristic part (2□) in which the relationship between the pilot pressure Pp and the displacement amount X is approximately linear is used, and the characteristic part (2,) in which the relationship between the pilot pressure Pp and the displacement amount X is non-linear.

! ! , :+) can be avoided, and the response of the control pressure PC to the displacement amount X of the pilot spool 16 can be kept constant.

In the fourth embodiment, the oil passage 19 of the pressure control valve 3 of the first embodiment is separated from the drain boat 20 and communicated with a newly provided pilot drain port 73, and the drain port 20 and the pilot drain boat 73 are connected to hydraulic piping. 74, and an accumulator 75 and a tank 76 are provided in the middle of the piping, but the rest is the same as the first embodiment.

With this configuration, in addition to the effects of the first embodiment, the following effects can also be obtained. That is, when the hydraulic suspension cylinder 38 is vibrated, oil flows from the control boat 35 to the drain port 20, and the back pressure in the drain port 20 increases. The accumulator 75 provided in the hydraulic pressure chamber 77 can prevent the pilot pressure P from increasing undesirably due to the back pressure, thereby stabilizing the operation of the pressure control valve.

(Effects of the Invention) As described above, the current control circuit for the hydraulic suspension of the present invention gives a phase lead to the target current, so that the deterioration of the current input frequency characteristics that occurs when the cylinder excitation input frequency characteristics are improved is avoided. This makes it possible to improve ride comfort and performance related to vehicle attitude control and operational stability.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing the overall configuration of a hydraulic suspension system using a current control circuit according to a first embodiment of the present invention, FIG. 2 is a system diagram of a second embodiment, and FIG. 3 is a system diagram of a third embodiment. FIG. 4 is a system diagram of the fourth embodiment, FIG. 5 is a frequency characteristic diagram of phase with respect to current input according to the present invention, FIG. 6 is a frequency characteristic diagram of gain and phase with respect to current input, and FIG. The figure is a frequency characteristic diagram of pressure fluctuation gain and phase with respect to excitation input, Figure 8 is a diagram showing the relationship between pilot pressure and control pressure according to the third embodiment of the present invention, and Figure 9 is a diagram showing the relationship between pilot pressure and control pressure. FIG. 3 is a diagram showing the relationship with the amount of displacement of the pilot spool. 3...Pressure control valve 4...Solenoid part 5.
...Pilot valve part 6...Reducing valve part 7...Plunger 8...Coil 15...Pilot spool 16...Circumferential groove 17...Pilot port 20...Drain port 24...・Valve body 25
, 72... Main spool 27... Supply port 29... Pyro throat chamber 32... Reaction force chamber 35... Control port 36... Orifice 37... Hydraulic piping 38
... Hydraulic suspension cylinder 50 ... Current control circuit 51 ... Phase lead circuit 52.57 ... Capacitor 53, 55.56.58.60.6L 62.64
...Resistors 54, 59...Differential amplifier 63...
Transistor 65...DC type i 70.7
1...Spring 73...Pilot drain port

Claims (1)

[Claims] 1. In a current control circuit that outputs a current for control to a hydraulic suspension that performs active control of a suspension cylinder by a pressure control valve, an orifice or a pressure control valve interposed between the pressure control valve and the suspension cylinder. 1. A current control circuit for a hydraulic suspension, comprising a phase advance circuit configured to compensate for a decrease in responsiveness of the pressure control valve to the current caused by a spring that suppresses movement of the spool.