JPS58131328A - Safety device of vehicular speed controlling apparatus - Google Patents

Abstract

PURPOSE:To contrive the run a vehicle with safety by a method wherein a valve means for safety, which suppresses the quantity of fuel to be supplied by detecting the abnormality of fluid pressure applied to a negative pressure actuator to control the fuel supplied to a fuel injection pump. CONSTITUTION:A negative pressure actuator 4 controls a fuel injection pump 2 by controlling the position of an operating rod 13. A negative valve 8 communicates through a negative pressure tank 12 to a vacuum pump 17. In order to control the constant speed running and idle running, a control unit 6 outputs valve opening and closing signals S1 and S2 in order to open and close valves 8 and 9 respectively. In case that the atmospheric pressure valve 9 is out of order and the control of the pressure in a negative pressure chamber 4a turns to be impossible, an emergency valve 10 is released by the valve opening and closing signal S3 outputted from the control unit 6. As a result, the pressure in the negative pressure chamber 4a is nearly equal to the atmospheric pressure, resulting in pushing out the operating rod 13 rightward in order to reduce the fuel injection quantity. In such a manner as mentioned above, the vehicle is prevented from running at high speed, resulting in ensuring the safety running of the vehicle.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the safety installation of a speed control device for a vehicle, and more specifically, the present invention relates to a vehicle speed control device that controls the speed of the internal combustion engine or the speed of the vehicle by adjusting the amount of fuel supplied to the internal combustion engine. This article relates to a safety device for speed control snow equipment for vehicles.

Conventionally, internal combustion engine I is controlled by adjusting the amount of fuel supplied to the internal combustion engine.
IO moderate or vehicle speed O driven by the internal combustion engine 111
Various electronically controlled speed control devices have been proposed, and for example, a negative pressure attacher is widely used as the attaching knee of this type of control device. A negative pressure actuator connected to a fuel adjustment member for adjusting the position of the fuel adjustment member of an internal combustion engine includes a negative pressure supply solenoid valve for introducing O negative pressure from a negative pressure source into the interior, and an atmospheric pressure The negative pressure acting on the actuator is adjusted according to the opening and closing operations of these solenoid valves, and the positioning of the fuel adjustment member is controlled. is configured to be performed. Therefore, if there is a problem in adjusting the negative pressure applied to the negative pressure actuator due to a failure of these solenoid valves or a failure of the circuit that controls the solenoid valves, excessive fuel supply may occur. This poses a problem in that there is a risk of the vehicle running out of control.

In order to solve this problem, we added a normally closed emergency solenoid valve to the atmospheric pressure supply solenoid valve, which is the case with conventional devices of this type.
If an abnormality occurs in the actuator or the control system, open the emergency solenoid valve. Negative pressure actuator: Treat the negative pressure inside the actuator to equalize it with atmospheric pressure, and stop or reduce the fuel supply. It is composed of However, in the past, it has been difficult to reliably detect abnormal conditions in the control that occur in the actuator, and it has not been possible to obtain a safety device that is satisfactory in terms of reliability.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a speed control system for a vehicle in which the position of a fuel adjustment member is electrically controlled using a hydraulic actuator, and to prevent excessive supply of fuel due to a failure of the actuator. To provide a highly reliable safety device for a speed control device for a vehicle, which can reliably prevent such problems and ensure safe operation of the vehicle.

The configuration of the present invention includes a fluid pressure actuator connected to a fuel adjustment member, a fluid pressure source, and a hydraulic actuator for controlling the position of the fuel adjustment member of an internal combustion engine. a first pressure regulating means for regulating the working fluid pressure applied to the fluid pressure attaching knee; In response to at least one signal indicating 5i! The above for a predetermined time width at intervals between OwII! A speed control device for an internal combustion engine, comprising a circuit for controlling the output of a drive signal for operating a 1111 pressure means, a stitch number means for repeatedly increasing the number of stitches output from the drive signal within a predetermined fixed time; , the fluid pressure acting on the fluid pressure actuator is activated in response to the counting result of the counting means being equal to or greater than a predetermined value, and operating the fuel adjustment member in a direction to decrease the amount of fuel supplied. The present invention is characterized in that it includes a second pressure regulating means for regulating pressure.

In a preferred embodiment, a negative pressure source is used as the fluid pressure source, and the 2111 pressure means includes, in addition to the first solenoid valve, a first pressure means for introducing atmospheric pressure into the fluid pressure actuator 1. By opening and closing the first and second solenoid valves, respectively, negative pressure or atmospheric pressure is introduced into the fluid pressure actuator. It is configured so that the magnitude of the pressure can be adjusted to an arbitrary value and the position of the fuel adjustment member can be controlled.

The fluid pressure actuator is set such that the amount of fuel supplied increases as the applied fluid pressure approaches the negative pressure of the negative pressure source, and the 2111th pressure means operates in response to the output from the counting means. , atmospheric pressure is introduced into the knee for fluid pressure activation, reducing the fuel supply.

Control of the negative pressure acting on the fluid pressure actuator is performed by the first
(by opening a solenoid valve or a second solenoid valve for a predetermined time period at regular time intervals), by repeating the operation of intermittently introducing negative pressure or atmospheric pressure into the fluid pressure actuator. , according to such a configuration, for example, the second
If the solenoid valve malfunctions or its drive circuit etc. malfunctions and the second solenoid valve is not opened, the level of the opening/closing signal applied to the solenoid valve will change. When osst exceeds a predetermined value, the second pressure regulating means is activated in response to a signal from the counting means, and the atmospheric pressure is adjusted to the fluid pressure attacher via the second pressure regulating means. be introduced within. As a result, it is possible to reliably prevent the engine speed from becoming abnormally high.

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

A first aillK is equipped with a safety device according to the present invention, and a 0-rotation speed control device 1 is shown in a schematic configuration diagram of an embodiment of a rotation moderation control device for an internal combustion engine vehicle. In this embodiment, a diesel locomotive is used as an example. The rotational speed control device 1 has a fuel adjustment device ff1i5 comprising a negative pressure actuator 4 for adjusting the position of the control lever 3 of the fuel injection unit 2; 4 is adapted to perform a fuel adjustment operation in response to a control signal output from the control unit 6.

The negative pressure chamber 4a of the negative pressure actuator 1 holder 4 is supplied with a negative pressure pulse f8, an atmospheric pressure pulse f9, and an emergency pulp 1 by the inner eve 7.
Connected to 0. These /electronic loops 8 to 10 are:
When the atmospheric pressure pulp 9 or the emergency pulp 1o, each of which is configured as a solenoid valve, is opened, atmospheric pressure is introduced into the negative pressure chamber 4a through these pulps. On the other hand, the negative pressure pulp 8 is communicated with the negative pressure tank 12 via the terminal 11), and when the negative pressure/valve 8 is opened,
The pressure in the negative pressure chamber 4a approaches the negative pressure in the negative pressure tank 12, and the operating rod 13 is pulled toward the left.

The negative pressure tank 12 is provided with a check valve 14 and a restrictor 15 in the middle.A vacuum tank 17 is connected to the negative pressure tank 12 via an arm id 16.
As a result, the pressure inside the negative pressure tank 12 is always maintained at a predetermined negative pressure.

A vehicle speed sensor 19 and a rotational speed sensor 2G are connected to the control unit 6, and signals related to the vehicle speed and the rotational speed of the internal combustion engine output from each sensor are controlled.
6. Control unit 6 wires: When the speed of the vehicle is above the power outage value, it operates in constant speed running control mode, and when the speed of the vehicle is below a predetermined value, when the engine (not shown) is in idle operation. K to perform idle operation control
It has become. These controls are performed by opening the nozzle 8 or 9 only for a predetermined time at regular time intervals in response to a pipe close signal 81m8 outputted from the control unit 6. That is, the pulp opening/closing signal 81, Hatake, is formed by outputting pulses of a predetermined pulse width that define the opening time of each pulp at regular intervals.
The generation period of the Norse train signal O is controlled so that the pressure in a becomes the pressure necessary to obtain the desired fuel injection amount.
)6KjP. Therefore, until the negative pressure in the negative pressure 114a matches the target negative pressure calculated by the control unit, the signal S1 or each p4 of B points is
The required number of ruses will be output.

The emergency valve is normally closed), atmospheric pressure/
If the valve 9 fails and the pressure in the negative pressure chamber 41 cannot be adjusted, it is opened by the pulp opening/closing signal ss output from the safety device according to the present invention.

When the emergency/temporal lO is released, the pressure of the negative pressure 1114m becomes almost atmospheric pressure, and the operating rod 13 is pushed out to the right to reduce the fuel injection amount and prevent the vehicle from becoming abnormally high speed. The width of the vehicle is set to K to ensure safe driving.

FIG. 2 shows a circuit diagram of the control system of the device shown in the 11th MK. Reference numeral 21 indicates a constant speed control circuit, which is supplied with power from the power supply voltage +V, and a 4 pulse signal whose repetition period changes according to the vehicle speed or engine rotational speed is input to the speed input terminal IN. . Then, the voltage is set so that the power supply voltage +V is applied to the −kg input terminal 8 of the constant speed control circuit 21 via the set switch 22.
When the set switch 22 is closed, the constant speed control state is reset, and the speed information input to the speed input terminal INK is stored at the timing when it is opened. The constant speed control circuit 21 has two output terminals 01.

At each output terminal 01sO, an excitation coil 9a of atmospheric pressure, 14 rutz 9 and an excitation coil 8a of negative pressure pulp 80 are respectively inserted into the coil circuit.
Each pace of the Chinda transistors 23 and 24 is IIm. These exciting coils 8 a # * m are excited when the level of the corresponding output terminal becomes high, the negative pressure pulp 8 is opened, and the atmospheric pressure outlet 9 is closed. Then, these O pulses 9 are opened and closed so that the 9 speed stored in the constant speed control circuit 21 is maintained, and the negative pressure actuator 40 is controlled (the first
(see figure).

The constant speed control circuit 21 is provided with a reset input terminal so that constant speed control operation can be canceled (if desired). Seventh, the input terminal R is normally connected to the power supply voltage +VK via a changeover switch 25 and a brake lamp switch 26, which are switched as shown by the solid line. Brake light 2 in response to brake failure
6 is closed, the brake lamp 27 lights up, the potential of the reset input terminal R reaches the level of the power supply voltage +V, and the constant speed control by the constant speed control circuit 21 is canceled. In addition, the symbol 28 indicates Riji Tame Musui,
It is Chi.

Detects malfunction of atmospheric pressure pulse f9 and emergency pulp lO
In order to open and close the output terminal 01, a binary counter 29 is provided to which the output of the output terminal o1 is applied as a counting input. Count the number of changes between high and low levels of the output level of r-)ノ? The two-way counter 29 is reset at the falling point p of the Luz GP.

The carry signal C from the binary counter 29 is applied to the pace of the switching transistor 30 via the resistor 31, and the binary counter 29 is operated for a predetermined time determined by the error width of 0 and P. (by reaching a predetermined count value in the trench), a carry signal C is output, the transistor 30 is turned on, and the excitation coil 10m for opening the emergency nozzle 10 is energized. . Negative pressure actuator 4
The pressure control of the negative pressure chamber 4a is performed using the negative pressure pulp 8 as described above.
Or by repeating the operation of intermittently introducing negative pressure or atmospheric pressure into negative pressure ml4a by opening atmospheric pressure/4f9 at regular time intervals for a predetermined time width. According to such a configuration, if the atmospheric pressure pulp 9 is not opened even though the atmospheric pressure i4 and f9 have failed and the transistor 23 has been turned off, the change in the level of the output terminal o1 will not occur. Frequency increases. That is, when the atmospheric pressure pulse f9 fails, the pulse flIll close signal IIm
Despite the output of K, the negative pressure in the negative pressure chamber 4a does not approach atmospheric pressure, so the pulse N#g compensation 4#8I is output for a longer period than that required during normal operation. In particular, this causes an increase in 5llR for a given period of time of the level change of the output terminal 010. During the high level period of the 4 pulse OP, the output terminal 01 level changes during normal operation.
If the frequency of level changes at terminal 030 exceeds a predetermined value due to a failure of atmospheric pressure pulp 9, the high level of Within the period, the count result of the binary counter 29 reaches a predetermined value, and a carry signal C is output. On the other hand, during normal operation, the frequency of level changes at terminal 01 is low, so carry signal C is never output. When this frequency exceeds a predetermined value, emergency pulp 10 is opened and emergency pulp lO is Atmospheric pressure is introduced into the negative pressure chamber 4a through the negative pressure chamber 4a.

As a result, the fuel injection amount is reduced, and it is possible to prevent the engine rotational speed or vehicle speed from becoming abnormally high.

Incidentally, the constant speed control circuit 21 having the above-mentioned function is, for example, an I
In addition to being able to use commercially available dianthus that has been converted to C, it is also possible to use a microcongijima-yuiyoshi structure.

When the vehicle speed is above a predetermined speed, this constant speed control circuit performs constant vehicle speed driving control, and when the vehicle speed is below a predetermined value, this constant speed control circuit performs idle driving control. In order to do this, the control unit 6 is equipped with a switching control circuit 40.

Based on the output from the switching control circuit 40Fi and the vehicle speed sensor 19, the vehicle speed/ll whose repetition period changes according to the vehicle speed.
It has a vehicle speed detection circuit 41 that outputs a soot number PI, and a rotation detection circuit 42 that outputs a rotation/ll sous number PI whose repetition period changes according to the engine rotation speed IK based on the output from the rotation speed sensor 20. are doing. The vehicle speed/error signal P1 is applied to one input of the NOR circuit 44 of the switching M jitter circuit 43, and is also applied to the frequency-voltage conversion circuit (F/V).
V) 415 and is converted into a vehicle speed voltage VrK whose level changes as shown in FIG. 3 with respect to the vehicle speed. The multiple voltage v1 is compared in level with the vehicle speed reference voltage V output from the reference vehicle speed voltage generator 46 in a voltage comparator 47, and if Vl > Va, the level of the output terminal of the voltage comparator 47 is When the level is low and p1v1≦v, O, the level of the output terminal of the voltage comparator 47 becomes high. The output terminal of the voltage comparator 47 is connected to the other input terminal (Noah@@44t) and one input terminal of each of the AND circuits 48 and 49. Therefore, when vl>v, the AND circuit 48 is closed, and only the vehicle speed/ll speed number P1 is taken out via the NOR circuit 44 and the OR circuit 50 and applied to the speed input terminal IN. In this case, since the AND circuit 49 is also closed, its output level is maintained at a low level.
Therefore, the set signal is not input to the set terminal S by the output of the AND circuit 49, and since the level of the output of the voltage comparator 47 is low, the changeover switch 25 is switched as shown by the solid line in the figure. There is. Therefore, constant vehicle speed traveling control can be performed at a desired vehicle speed by manually operating the set switch 22, and the constant vehicle speed traveling control state can be canceled by operating the brake.

On the other hand, the other input terminal of the AND circuit 48 has the rotation a4
Since the pulse signal Pa is applied, if v1≦V, only the rotational pulse signal P is switched vs') y
The signal is output from the circuit 43 and input to the speed input terminal IN. In this case, the AND circuit 49 is opened and the set signal from the rotational speed setting circuit 60 is applied to the set input terminal IK via the diode 51.

The rotation speed setting circuit 60 sets the target rotation speed of the constant speed control circuit 21 to the speed N when the engine rotation speed N reaches a predetermined first idle rotation speed N1.

At the same time as the speed NIK is set, the final target second idle rotation speed 11N, which is lower than the 1st speed N1, is set after a predetermined time has elapsed since the speed NIK is set.
A frequency-voltage conversion circuit (F/V) 6 that converts the rotational pulse signal P into nine levels of rotational voltage VS according to its frequency.
1, the rotational voltage v and the engine rotational speed N are set in a relationship as shown in Fig. 4, and the rotational voltage V
is applied to the voltage comparator 610+ input terminal. code 63
fWt denoted by is a reference rotational voltage generator for outputting a reference rotational voltage V% indicating a predetermined idle speed Ni for the constant speed control circuit 21.

In order to correct the value of the rotational speed Ni set by the reference rotational voltage generator 63 according to the horizontal opening cooling water temperature at the time,
A water temperature detection circuit 64 is connected to the reference rotational voltage generator 63, and the value of the reference rotational voltage vb is corrected according to the cooling water temperature detected by the water temperature detection circuit 64. This correction is the same as the correction operation performed in conventional devices of this type, so a detailed explanation will be omitted.

The reference rotational voltage V, is applied to one input terminal of the voltage comparator 62, so if s N > N t,
The level of the output terminal of the voltage comparator 62 becomes high level.

On the other hand, when N≦Ni, the level of the output terminal of the voltage comparator 62 becomes a low level. Therefore, if the AND circuit 49 is open, the level of the set input terminal S will not change from a high level to a low level when it becomes N-1-Nl, and the rotational speed Ni will be in the constant speed control circuit 21. is stored in
Thereafter, the device maintains the engine rotational speed at a predetermined idle link rotational speed f NI K.

As already mentioned, 1This idling rotational speed Ni is
In order to reduce fuel consumption, it is preferable to set it as low as possible, but if the rotation speed changes from high rotation speed to idling speed, there is a strong possibility that the engine will stall. In order to solve this problem, the rotation speed setting circuit 60 is configured to change and set the target idling rotation speed in stages in order to bring the idling rotation speed closer to the target value in stages. The ζO setting is performed by a delay circuit 65, a holding circuit 66, and a reset circuit 67.

The delay circuit 65 has a NOR circuit 69, one input terminal of which is directly inputted the output voltage of the voltage comparator 62, and the other input terminal connected to the output terminal of the timer 68. The timer 68 is applied with the output voltage of the voltage regulator 62 and operates in response to the output voltage of the voltage comparator 20. That is, when the output level of the timer 68 becomes a normal high level and the output voltage of the voltage comparator 62 changes from a high level to a low level Km, it is tied! 6B starts working and time! After the time has elapsed, the output level of the timer 68 is set to be low for the duration of the power outage. Therefore, the output level of the NOR circuit 69 is low level when the output voltage level of the voltage comparator 62 is high level. When the output voltage level of the voltage comparator 62 changes to a low level, the output level of the 1-NOR circuit 69 becomes a high level for a predetermined time after time T has elapsed.

The holding circuit 66 is connected to the OR circuit 70 and the AND circuit 71, and one input terminal of the OR circuit 70 is connected to the delay circuit 6.
5 is input as a set signal, and the AND circuit 71
An output from a reset circuit 67, which will be described later, is input as a reset signal to one input terminal of the . The holding circuit 66 is reset by the reset signal becoming "L", and the output level of the AND circuit 71 becomes rLJ.

Since the output of the AND circuit 71 is fed back to the other input of the OR circuit 70, if the reset signal is at the "H" level after the holding circuit 66 appears in the reset state, the In response to the level change from rLJ to rHJ, the output level of the AND circuit Fl changes to r
It changes to HJ and continues to maintain the "H" level state. The output voltage of the AND circuit 71 is
C) is outputted as an output voltage vk and applied to the reference rotational voltage generator 63.

The reference rotational voltage generator 63 generates the reference rotational voltage V in response to the level of the output voltage vh from the holding circuit 66.

The level is configured to be exhausting. That is, the level of the reference rotational voltage vb is equal to the level r of the output voltage vh.
In the case of LJ level, high eye P IJ shielding degree N, (
For example, 1000 (r, p, m))K corresponding rotational voltage V
, level vb1 and tCl. On the other hand, when the level of output voltage V, is rHJ level, the final target idling cutoff 1
11tlbc (for example, 600 (r, pom)) The rotation voltage v 嘗 changes to the level vb 嘗 corresponding to 72, a high idling rotational speed N, and a slightly higher predetermined rotational speed N.

The voltage comparator 72 sets the level V of the large rotation voltage V corresponding to K to the voltage comparator 72.
The output level of the voltage comparator 72 becomes rLJ when the rotational speed N becomes larger than the predetermined rotational speed FNr. Otherwise, the holding circuit 66 is reset.

According to this circuit configuration, immediately after switching from the vehicle speed control state to the rotational speed control state, the holding circuit 66 is in the reset state WIAK as described above, and its output is at a low level. Therefore, the level of the reference rotational voltage V outputted from the reference rotational voltage generator 63 becomes the level vb1 corresponding to the high idling rotational speed N, and the output level of the voltage comparator 62 becomes the rHJ level. There is. In this state, when the rotational speed N decreases to N1, the output level of the voltage comparator 62 changes from a high level to a low level.

As a result, the high idling rotational speed N is set in the constant speed control circuit 21 to perform constant rotational speed control, and the engine speed is controlled so as to temporarily maintain the high idling rotational speed N. In this case, N≦N.

At the point in time, the output level of the voltage comparator 72 becomes rHJ, but since the output level of the voltage comparator 62 is rHJ, the output level of the delay circuit 6S is rLJ.
The level of the output voltage V is as high as rLJ.

When the output level of the voltage comparator 62 changes from rHJ to rLJK, the output level of the delay circuit 65 changes to a high level after time T has elapsed, and this is held at p by the holding circuit 66, and the level of the reference rotation voltage vb is The higher the idling rotation speed N, the lower the final target idler rotation shielding degree NbK, the corresponding VbsK is changed.

As a result, voltage comparator 61! The O output level becomes high once (PEL KjH), and as a result, the set state of the P constant speed control circuit 21 is released, and the engine rotational speed N begins to decrease.Then, when it becomes NM-N%, the voltage comparison The output level of the controller 62 changes from high level to low level again, and the final idling rotational speed Nb is set to - to the constant speed control circuit 21, and the idle cylinder rotational shielding degree Ni is maintained at Nb. . In this case, the delay circuit 65 will operate again, but since the holding circuit 66 is already in the set state at this time, it will not respond to the above-mentioned O re-operation of masss, and the level of its output voltage vh will be Includes low level 1,
The level of the reference rotational voltage vb continues to be held at νb-.

During the period when the above-mentioned idling rotational speed control is about to be performed, the accelerator pedal is depressed and the rotational speed N changes to N.
When r is exceeded, the output level of the voltage comparator 72 becomes a low level and the holding state of the holding circuit 66 is released. As a result, the circuit 60 returns to the initial state 111, and when the accelerator pedal is released, the above-described control operation is resumed.

In the above embodiment, a safety device for a speed control device for a vehicle using a diesel engine as a driving source has been described, but the present invention is not limited thereto, and can be applied to a vehicle using another internal combustion engine as a driving source such as a gasoline engine. The present invention can be similarly applied to a safety device for a speed control device.

According to the present invention, as described above, by opening and closing the round valve means for adjusting the fluid pressure applied to the fluid pressure actuator at regular time intervals for a predetermined period of time, the fluid pressure actuator is adjusted. monitoring the level of a signal for actuating a valve means in a device for adjusting the applied fluid pressure and regulating the speed of the internal combustion engine; A malfunction of the actuator is detected, and a separately provided safety valve is activated to suppress the amount of fuel supplied to the internal combustion engine, so a simple device can be used to prevent over-injection of fuel due to actuator failure. By reliably detecting the supply and preventing it, we can expect highly reliable operation, which is 11 times more effective.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an embodiment of the apparatus of the present invention,
a is a block diagram of the control system of the 9th device showing the 1st mK;
Figure 4 and Figure 4 are vehicle speed voltage and rotational voltage zero characteristics diagrams, respectively. 1-It! Moderate control device, 2...Fuel injection, 3
... Control unit, 4... Negative pressure actimator, S... Fuel adjustment device, 6-, Control unit, 8-
・Negative pressure valve, -...Atmospheric pressure valve, 1o...Lt
Valve, 29-binary counter, OF...r-) pulp, 81*S1*8m...puff+/1 open/close signal, C...
・Carry signal. Patent applicant: Diesel Kiki Co., Ltd. Agent Patent attorney: Masatoshi Takano 175

Claims (1)

[Claims] 1. A fluid pressure actuator connected to the fuel adjustment member for controlling the position of the fuel adjustment member of a vehicle internal combustion engine, a fluid pressure source, and supplying working fluid from the fluid pressure source to the fluid pressure actuator. The first to control the
a first pressure regulating means including a solenoid valve and regulating the pressure of the working fluid applied to the hydraulic actuator 1; A speed control device for an internal combustion engine, comprising: control means for controlling the output of a drive signal for operation in response to at least one signal indicating an operating state of the internal combustion engine, wherein the drive signal within a predetermined fixed period of time; a counting means for repeatedly counting the number of outputs of the fluid; and a counting means for repeatedly counting the number of outputs of the fluid; 1. A safety device for a speed control device for a vehicle, comprising a second pressure regulating means for regulating fluid pressure acting on a pressure actuator.