Slide valve, especially for use in a motor vehicle automatic transmission

Abstract

Slide valve (5) with a valve spool (14) which can be acted upon by an electromagnet (8) in a first direction (16) and by a pressure in a control chamber (36) in a second direction opposite to the first (18), which can hydraulically connect a working port (A) to an inlet port (P) or an outlet port (T) by means of a recess (20), wherein a hydraulic pressure is taken off at a tap point (38) in a flow channel (34) of the slide valve (5) and supplied to the control chamber (36), wherein the tap point (38) is arranged in the region of the recess (20) in the axial direction of the valve spool (14) between the inlet port (P) and the working port (A) and wherein a channel (40) from the tap point (38) to the control chamber (36) is arranged in a housing (6) of the slide valve (5) or in the valve spool (14), characterized bythat an end section of at least one bore not used for the channel (40) is sealed by means of a ball (42).

Description

State of the art

[0001] The invention relates to a slide valve according to the preamble of claim 1.

[0002] Electrically operated solenoid valves, particularly so-called pressure control valves (spool valves), are well known in automatic transmissions of motor vehicles. These valves can be used to directly control the clutches of the automatic transmission. Such valves should be able to operate relatively dynamically and enable a large hydraulic flow in a short time. They should also be stable and insensitive to disturbances.

[0003] A common embodiment of pressure control valves comprises an actuator for operating a valve spool, which can actuate a hydraulic unit. The hydraulic unit has, for example, an inlet connection, one or more outlet connections (drain connections), and at least one working connection, which is hydraulically connected to a return connection via an external hydraulic line. The hydraulic return line runs, for example, via a so-called control plate and serves to return the working pressure to a control chamber adjacent to the valve spool.

[0004] For example, a pressure control valve works as follows: When the actuator is de-energized (the associated electromagnet is not energized), a spring pushes the valve spool together with the armature into a first end position. In this position, the working port is hydraulically connected to the drain port. The pressure control valve is therefore normally closed or “NC”. When the electromagnet is energized, the armature and the valve spool are moved by magnetic force against the spring force towards a second end position. During the movement of the valve spool, the working port is first hydraulically separated from the drain port, and then the working port is connected to the inlet port. The pressure prevailing at the inlet port is now transferred to the working port.Since the pressure increase at the working port is transmitted to the return port via a hydraulic line, the same pressure builds up in the control chamber (return chamber, FB chamber) of the spool valve connected to the return port. This pressure exerts a compressive force on the valve spool that acts against the actuator. If this compressive force, together with the spring force, exceeds the magnetic force of the electromagnet, the valve spool is displaced axially again in such a way that the inlet port is increasingly hydraulically decoupled from the working port or even separated. This creates a force equilibrium between the spring force and hydraulic pressure force on the one hand, and the magnetic force on the other. In this way, the pressure prevailing at the working port can be adjusted within wide limits depending on the current flowing through the electromagnet.

[0005] An example of a patent publication in this field is DE 10 2008 042 624 A1.

[0006] From US 2008 / 0 072 978 A1, a slide valve is known with a valve slide that can be acted upon by an electromagnet in a first direction and by a pressure in a control chamber in a second direction opposite to the first. The valve slide can hydraulically connect a working connection to an inlet connection or an outlet connection by means of a recess. A hydraulic pressure is tapped at a tapping point in a flow channel of the slide valve and fed to the control chamber. The tapping point is arranged in the region of the recess, viewed in the axial direction of the valve slide, between the inlet connection and the working connection, and a channel from the tapping point to the control chamber of the slide valve is arranged in the valve slide.

[0007] From US 2002 / 0 134 443 A1 a slide valve with a pilot valve is known, in which a hydraulic pressure is tapped at a tapping point in a flow channel of the slide valve and fed to a control chamber.

[0008] Further slide valves are known from CN 1 01 896 752 A and DE 695 08 807 T2. Disclosure of the invention

[0009] The slide valve according to the invention has a valve slide which can be acted upon by an electromagnet in a first direction and by a pressure in a control chamber in a second direction opposite to the first, which valve slide can hydraulically connect a working connection to an inlet connection or an outlet connection by means of a recess, wherein a hydraulic pressure is tapped at a tapping point in a flow channel of the slide valve and fed to the control chamber and the tapping point is arranged in the region of the recess in the axial direction of the valve slide between the inlet connection and the working connection and a channel from the tapping point to the control chamber of the slide valve is arranged in the valve slide.

[0010] According to the invention, an end section of at least one bore not used for the channel is caulked with a ball. In this way, the channel can be easily manufactured using axially and radially aligned bores, with the unused end sections being hydraulically sealed by at least one ball. This reduces the cost of the slide valve.

[0011] Advantageous further training is specified in subclaims.

[0012] The slide valve according to the invention can be provided as a pressure control valve for use in a motor vehicle automatic transmission and, when a working port is hydraulically connected to an inlet port, exhibits a particularly short step response time. This allows, for example, clutches of the automatic transmission to be actuated quickly and reliably.

[0013] The invention takes into account that such slide valves have a – generally electromagnetically actuated – actuator that can actuate a valve slide in a first direction. Furthermore, a pressure prevailing in a control chamber can actuate the valve slide in a second direction, opposite to the first. The slide valve is designed as a pressure control valve in such a way that a force equilibrium can arise between the actuator, on the one hand, and an axial force generated by the pressure in the control chamber, on the other. The latter force is usually supported by the force of a valve spring. This results in the desired pressure control at the working port as a function of the axial force of the actuator.

[0014] The higher the pressure in the control chamber, the less effective the actuator is, and conversely, the lower the pressure in the control chamber, the more effective the actuator is. Therefore, hydraulic pressure is tapped at a tapping point in a flow channel of the spool valve and fed into the control chamber. For rapid opening, the lowest possible pressure in the control chamber is desirable, at least for a short time. For this purpose, the tapping point is located in the region of an axially extending recess in the valve spool between the inlet connection and the working connection. The recess essentially forms the flow channel.

[0015] A comparatively low hydraulic pressure prevails at the extraction point when the inlet connection and the working connection are hydraulically connected to one another when the valve spool is in the appropriate position or movement, resulting in a strong hydraulic flow with a comparatively low hydrostatic pressure in the flow channel, at least temporarily. This effect is also known as the "suction jet effect", for example from a water jet pump. This low pressure is fed to the control chamber. This opening phase of the valve spool movement is therefore supported by the resulting comparatively low pressure in the control chamber, so that the spool valve can quickly generate a high hydraulic pressure at the working connection. The so-called "step response time" is correspondingly short and the dynamics of the spool valve correspondingly high.

[0016] If the inlet port and the working port subsequently have the same hydraulic pressure, the flow in the flow channel disappears or at least decreases, and the control chamber can assume approximately the same pressure as the working port, thus contributing to regulating the desired pressure. However, as soon as a pressure increase is requested again, this can be achieved with high dynamics.

[0017] It is understood that the described connections can be any hydraulic connections of the slide valve with any function, provided that the hydraulic pressure at the “inlet connection” is at least temporarily higher than the pressure at the “working connection”.

[0018] One design of the slide valve provides for a channel from the extraction point to the control chamber to be arranged in a slide valve housing. This channel thus forms the return line between the flow channel or extraction point and the control chamber. By arranging the channel in the slide valve housing, any leaks can be kept to a minimum, thereby improving the function of the slide valve. The extraction point is fixed in position with respect to the slide valve housing.

[0019] A further design of the slide valve provides for the channel from the tapping point to the control chamber to be located in the valve slide. This allows the channel to be designed particularly simply and with optimal flow characteristics. Leakage can also be minimized. Furthermore, existing valve designs can be converted into a slide valve according to the invention with little effort. The tapping point is fixed in position with respect to the valve slide.

[0020] The dynamic behavior of the spool valve is improved if the recess and / or a wall section of the housing opposite it is shaped to minimize the pressure at the tapping point during fluid flow from the inlet port to the working port. Methods for this are already known in the field of hydraulics. For example, the hydraulic pressures and flow velocities occurring in the spool valve or in the recess can be calculated using simulations, thereby optimizing the geometry of the spool valve. One goal of such simulations can be to minimize the hydrostatic pressure ("negative pressure") resulting at the tapping point and to maximize the dynamics of the spool valve accordingly, particularly while a hydraulic connection is being established between the inlet port and the working port.

[0021] One embodiment of the slide valve provides that a hydraulic connection is established between the inlet connection and the working connection when the electromagnet is de-energized. Alternatively, a hydraulic connection is established between the outlet connection and the working connection when the electromagnet is de-energized. When the electromagnet is de-energized or the actuator is inactive, the valve slide is moved into the corresponding axial position by the force of the valve spring and held there. This makes the invention applicable to various basic embodiments of slide valves or hydraulic controls of automatic transmissions. Furthermore, the invention is also applicable to slide valves with at least partially "rising" or at least partially "falling" characteristic curves.

[0022] Exemplary embodiments of the invention are explained below with reference to the drawings. In the drawings: Fig. 1 shows a first embodiment of a slide valve in a partial sectional view with a channel in a housing of the slide valve; Fig. 2 a second embodiment of the slide valve similar to the Fig. 1; Fig. 3 a third embodiment of the slide valve in a partial sectional view with a channel in a valve slide of the slide valve; Fig. 4 a slide valve in a partial sectional view with a channel outside the housing of the slide valve; and Fig. 5 a step response of a pressure at a working port of the slide valve of the Fig. 1 to 4.

[0023] The same reference numerals are used for functionally equivalent elements and sizes in all figures, even in different embodiments.

[0024] Fig. 1 shows a slide valve 5 for hydraulically actuating a clutch device of an automatic transmission of a motor vehicle. The slide valve 5 comprises a housing 6, on which an actuator, embodied here as an electromagnet 8, is arranged in the right-hand area of ​​the drawing. Furthermore, the slide valve 5 comprises further housing sections 7 not explained in detail here. The slide valve 5 and the elements belonging to the slide valve 5 are designed to be substantially rotationally symmetrical about a longitudinal axis 15.

[0025] The electromagnet 8 comprises a coil 9 and an armature 10, which can be attracted to the left in the drawing by a pole core 11 when the coil 9 is energized. The armature 10 is coupled by means of a coupling element 12 and a coupling pin 13 to an axially displaceable valve spool 14 arranged in the housing 6. The valve spool 14 is shown in the center and left area of ​​the drawing in an axially center position. An arrow 16 indicates a first axial direction, and an arrow 18 indicates a second axial direction.

[0026] The valve spool 14 has a radially circumferential recess 20 in the form of a stepped constriction, which extends in the axial direction and by means of which a working connection A can be hydraulically connected alternatively to an inlet connection P or an outlet connection T. The inlet connection P, the working connection A and the outlet connection T are hydraulically connected to respective annular spaces 22, 24 and 26 formed in the housing 6. However, these connections are not shown in the sectional view of the Fig. 1. Three arrows 30, 31, and 32 indicate the direction of the possible hydraulic flows flowing through the ports. A flow channel 34 is formed by the recess 20 in a radially inner section of the housing 6. Furthermore, the slide valve 5 includes two drain ports T1 and T2 for draining leaks.

[0027] An annular space in the left-hand area of ​​the spool valve 5 in the drawing forms a control chamber 36. The control chamber 36 is delimited, among other things, by pressure surfaces (without reference numerals) of the valve spool 14, arranged to the left and right of an annular groove 37 present in the valve spool 14. The right-hand pressure surface is larger than the left-hand pressure surface.

[0028] The control chamber 36 is hydraulically connected to a tapping point 38 of the flow channel 34 via a radial bore, an axial bore, and another radial bore (each without a reference symbol) in the housing 6. The tapping point 38 is arranged in the region of the recess 20, viewed in the axial direction of the valve spool 14, between the inlet port P and the working port A. The radial bores and the axial bore together form a channel 40 and are hydraulically sealed at their unused end sections by means of a ball 42 each. The axial bore was drilled through a recess 44 in the housing 6.

[0029] An end section of the valve slide 14, shown on the left in the drawing, is urged to the right by a valve spring 46. The valve spring 46 is supported on a pressed-in end piece 48 of the housing 6. Overall, the leakages of the slide valve 5 are Fig. 1 is comparatively low due to the channel 40 integrated into the housing 6. The Fig. The recess 20 shown in Figure 1 and a wall section of the housing 6 opposite it are optimized for the purpose of minimizing the hydrostatic pressure at the extraction point 38 during a fluid flow from the inlet connection P to the working connection A.

[0030] When the electromagnet 8 is de-energized, the valve spool 14 is pushed to the right in the drawing (arrow 18) by the force of the valve spring 46, hydraulically connecting the working port A to the annular space 26 or the drain port T. The drain port T has no or only a comparatively low hydraulic pressure. Thus, the pressure at the working port A is also low. The spool valve 5 is therefore closed in the de-energized state.

[0031] When the electromagnet 8 is energized, the armature 10 is attracted by magnetic force to the left in the drawing (arrow 16) by the pole core 11. The coupling pin 13 transfers this force to the valve spool 14, whereupon the latter initially moves in the direction of arrow 16. As soon as the flow channel 34 is hydraulically connected to the annular space 22, a hydraulic flow results from the inlet connection P to the working connection A. The inlet connection P has a comparatively high hydraulic pressure. Accordingly, the flow velocity at the extraction point 38 is high and the hydrostatic pressure low, and thus also correspondingly low in the channel 40.

[0032] The low pressure prevailing in channel 40 is transferred to control chamber 36. Because the pressure area to the right of annular groove 37 in the drawing is larger than the left pressure area, an axial resultant force is produced there to the left in the drawing, which supports the action of electromagnet 8. This accelerates the movement of valve spool 14 in direction 16, and working port A can be connected particularly quickly with a large cross-section to inlet port P, thus opening spool valve 5 quickly. In this state, spool valve 5 functions as a pressure control valve, whereby a force equilibrium can arise between the force of valve spring 46 and an axial force generated by the pressure in control chamber 36 on the one hand, and the magnetic force of electromagnet 8 on the other.

[0033] Fig. Figure 5 shows a step response of a pressure 60 at the working port A of the slide valve 5. The pressure 60 is plotted along with a current I flowing through the coil 9 on the ordinate of the illustrated coordinate system. The abscissa represents the time t. A first dashed line 62 represents a nominal value of the current I, a second dashed line 64 represents a setpoint value of the pressure 60. The representation of the Fig. 5, for example, describes the temporal course of the hydraulic pressure in an actuator of a clutch of the automatic transmission.

[0034] Starting at time t1, coil 9 is energized with current I. After a dead time, pressure 60 rises abruptly to a first value 66 at time t2 and then rises steadily to a second value 68 at time t3. At time t3, pressure 60 rises abruptly to setpoint 64. The period between time t1 and time t3 refers to a "step response time" of slide valve 5.

[0035] From time t3 onward, the setpoint 64 of pressure 60 is reached, with the hydraulic flow in flow channel 34 essentially disappearing. Subsequently, the pressure in channel 40 and, accordingly, in control chamber 36 approximately assumes the hydraulic pressure at working port A. As a result, slide valve 5 can regulate the pressure at working port A depending on the current I flowing through the coil in a known manner, similar to a pressure control valve.

[0036] Fig. 2 shows a second and to the Fig. 1 similar embodiment of the slide valve 5. In contrast to the Fig. 1, an annular space 52 accommodating the valve spring 46 is radially enlarged so that the axial bore (without reference symbol) of the channel 40 can be drilled over the annular space 52. The recess 44 is thus dispensable. The housing 6 and the end piece 48 are adapted accordingly. The functional elements of the slide valve 5 of the Fig. 2 are those of the Fig. 1 equal.

[0037] Fig. Figure 3 shows an embodiment of the slide valve 5, in which the channel 40 from the extraction point 38 to the control chamber 36 is arranged in the valve slide 14. The valve slide 14 is shown here in a sectional view. The control chamber 36 is hydraulically connected to the extraction point 38 of the flow channel 34 via two radial bores and one axial bore (each without reference symbol) of the valve slide 14. The radial bores and the axial bore together form the channel 40. The extraction point 38 is, in contrast to the Fig. 1 and Fig. 2 is an element of the valve spool 14 and is therefore movable with it. In the present case, the extraction point 38 is designed as a pipe section 54 arranged radially on the valve spool 14. As a result, the extraction point 38 or the opening of the pipe section 54 can be arranged relatively close to a radially inner wall section of the housing 6.

[0038] In the Fig. 3, the sectional view of the housing 6 is selected so that the channels forming the inlet connection P, the working connection A and the outlet connection T are visible (without reference symbols). The remaining elements of the slide valve 5 are identical to the corresponding elements of the Fig. 1 and Fig. 2 similar or equal.

[0039] Fig. Figure 4 shows a slide valve 5 in which the channel 40 from the extraction point 38 to the control chamber 36 is arranged outside the housing 6 of the slide valve 5. The channel 40 is connected to the control chamber 36 and the flow channel 34 via radial connections 56 and 58. The channel 40 can, for example, be a channel in a control plate of the automatic transmission or a discrete hydraulic line. The remaining elements of the slide valve 5 are similar to the corresponding elements of the Fig. 1 or Fig. 2 similar or equal.

[0040] The Fig. The embodiments described in Figures 1 to 3 show slide valves 5 which are "normally closed", i.e., when the electromagnet 8 is not energized, the working port A is hydraulically separated from the inlet port P. However, it is also possible - for example by exchanging the inlet port P with the outlet port T as well as by redesigning the recess 20 and changing the arrangement of the tapping point 38 - to design the slide valve 5 as "normally open". When the electromagnet 8 is not energized, the working port A is hydraulically connected to the inlet port P. This is shown in the Fig. 1 to 3 are not shown.

Claims

[1] Slide valve (5) with a valve slide (14) which can be acted upon by an electromagnet (8) in a first direction (16) and by a pressure in a control chamber (36) in a second direction (18) opposite to the first, which valve slide can hydraulically connect a working connection (A) to an inlet connection (P) or an outlet connection (T) by means of a recess (20), wherein a hydraulic pressure is tapped at a tapping point (38) in a flow channel (34) of the slide valve (5) and fed to the control chamber (36), wherein the tapping point (38) is arranged in the region of the recess (20) in the axial direction of the valve slide (14) between the inlet connection (P) and the working connection (A), and wherein a channel (40) from the tapping point (38) to the control chamber (36) is provided in a housing (6) of the slide valve (5) or in the valve slide (14) is arranged, characterized bythat an end section of at least one bore not used for the channel (40) is caulked by means of a ball (42). [2] Slide valve (5) according to claim 1, characterized by that the recess (20) and / or a wall section of the housing (6) opposite it are / is shaped for the purpose of minimizing the pressure at the extraction point (38) during a fluid flow from the inlet connection (P) to the working connection (A). [3] Slide valve (5) according to at least one of the preceding claims, characterized by that when the electromagnet (8) is de-energized, a hydraulic connection is established between the inlet connection (P) and the working connection (A). [4] Slide valve (5) according to at least one of the preceding claims, characterized by that when the electromagnet (8) is de-energized, a hydraulic connection is established between the drain connection (T) and the working connection (A). [5] Slide valve (5) according to at least one of the preceding claims, characterized by that the slide valve (5) is intended for use in a motor vehicle automatic transmission.

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