Solenoid Valve for a Vehicle Braking System

Abstract

In one embodiment, a solenoid valve for a vehicle braking system includes a magnet assembly having a winding support, a coil winding, a housing, and a cover disc. The solenoid value further includes a valve cartridge having a capsule, a valve insert, a valve seat, and an armature. The valve insert can be connected to the capsule, the armature can be guided within the capsule in an axially movable manner and has a closing element. The closing element and the valve seat can form a valve that can control a fluid flow through the valve cartridge. The coil winding can be wound on the winding support to form an electrical coil, which can be controlled using control signals applied to electrical connectors. The electric coil generates a magnetic force that can move the armature against a force of a return spring.

Claims

1. A solenoid valve for a vehicle braking system, comprising: a magnet assembly including: a winding support; a coil winding; a housing; and a cover disc; a valve cartridge including: a capsule; a valve insert connected to the capsule; a valve seat; and an armature configured to be guided within the capsule in an axially movable manner between a closed position and an open position, the armature including a closing element, wherein the closing element and the valve seat are configured to form a valve that is operable to control a fluid flow through the valve cartridge, wherein the coil winding is wound on the winding support to form an electrical coil, the electrical coil being configured to be controlled by using control signals applied to electrical connectors, wherein the electric coil is further configured to generate a magnetic force that is operable to move the armature against a force of a return spring, wherein fluid temperature within the valve cartridge is changeable based on the control signals, wherein the control signals are configured to be applied to the coil winding as bipolar AC signals having a predetermined frequency and are further configured to generate eddy currents in an iron circuit of the solenoid valve and in the capsule, and wherein the eddy currents are operable to heat up the fluid in the valve cartridge.

2. The solenoid valve as claimed in claim 1, wherein the iron circuit of the solenoid includes the armature, the housing and the cover disc.

3. The solenoid valve as claimed in claim 1, wherein the coil winding is configured to be arranged in a bridge branch of an H-bridge circuit, the H-bridge circuit including four switching transistors.

4. The solenoid valve as claimed in claim 1, wherein the heating operation of the magnet assembly includes at least two heating modes that have in each case a predetermined frequency range for the bipolar AC signals.

5. The solenoid valve as claimed in claim 4, wherein in a first heating mode the frequency of the bipolar AC signal is predetermined from a first frequency range so that the valve does not react to the applied control signals.

6. The solenoid valve as claimed in claim 5, wherein the first frequency range includes frequencies in the range of ca. 0.1 kHz to 2.0 kHz.

7. The solenoid valve as claimed in claim 4, wherein in a second heating mode, the frequency of the bipolar AC signal is configured to be predetermined from a second frequency range so as to achieve a maximal inductive thermal output.

8. The solenoid valve as claimed in claim 7, wherein the second frequency range includes frequencies in the range of ca. 2.1 kHz to 3.0 kHz.

9. The solenoid valve as claimed in claim 4, wherein in a third heating mode, the heating mode is switched between the first heating mode and the second heating mode based on an operating state of the vehicle, and wherein the prevailing frequency of the bipolar AC signal is dependent upon an available onboard network voltage.

10. The solenoid valve as claimed in claim 9, wherein the optimal frequency for each voltage position is stored in the form of a characteristic curve.

Description

[0014] Short description of the drawings

[0015] FIG. 1 illustrates a schematic sectional view of a detail of an exemplary embodiment of a solenoid valve in accordance with the invention for a vehicle braking system.

[0016] FIG. 2 illustrates a schematic switching diagram of an electronic H-bridge circuit for controlling the solenoid valve in accordance with the invention for a vehicle braking system shown in FIG. 1.

EMBODIMENTS OF THE INVENTION

[0017] As is evident in FIG. 1, the illustrated exemplary embodiment of a solenoid valve 1 in accordance with the invention for a vehicle braking system comprises a valve cartridge 10 and a magnet assembly 20. The valve cartridge 10 comprises a capsule 12, a valve insert 16 that is connected to the capsule 12, an armature 14 that is guided within the capsule 12 in an axially movable manner between a closed position and an open position, said armature comprising a closing element (not further illustrated), and said valve cartridge comprises a valve insert 16 that is connected to the capsule 12 and comprises a valve seat (not further illustrated). The closing element and the valve seat form a valve that controls a fluid flow through the valve cartridge 10. The magnet assembly 20 comprises a winding support 22, a coil winding 24 that is wound on the winding support 22, a housing 26 and a cover disc 28 that closes the housing 26 towards the bottom. The magnet assembly 20 is pushed with the housing 26 and the cover disc 28 onto the upper part of the capsule 12 of the valve cartridge 10. The coil winding 24 that is part of the magnet assembly 20 and is wound on the winding support 22 forms an electrical coil that can be controlled by way of control signals that are applied to electrical connectors 24.1, 24.2 and said electrical coil generates a magnetic force that moves the armature 14 against the force of the return spring 18. In a heating operation, it is possible based on the control signals to change the fluid temperature within the valve cartridge 10, preferably to increase said temperature. In accordance with the invention, the control signals are applied to the coil winding 24 as bipolar AC signals having a predetermined frequency, and generate eddy currents in the iron circuit of the solenoid valve 1 and in the capsule 12, and said eddy currents heat up the fluid 3 that is present in the valve cartridge 10.

[0018] Embodiments of the solenoid valve in accordance with the invention can be used by way of example in an anti-lock braking system (ABS) or a traction control system (ASR system) or an electronic stability program system (ESP system). In the illustrated exemplary embodiment, the solenoid valve 1 in accordance with the invention is embodied by way of example as a non-energized open control valve that can be operated in the case of specific requirements in a QS operation (=quasi switching operation) in which it is possible to switch as quickly as possible from the closed position into the open position. Alternatively, the solenoid valve 1 in accordance with the invention can be embodied as a non-energized closed control valve that can be operated in the case of specific requirements in a QS operation (=quasi switching operation) in which it is possible to switch as quickly as possible from the closed position into the open position. Furthermore, embodiments of the solenoid valve 1 in accordance with the invention for a vehicle braking system can be sealed in a corresponding receiving bore of a fluid block (not illustrated).

[0019] As is evident in FIG. 2, the coil winding 24 is arranged in the bridge branch of an H-bridge circuit 5 that comprises four switching transistors T1, T2, T3, T4. FIG. 2 illustrates the equivalent circuit diagram of the coil winding 24 having an inductivity L.sub.w and an ohmic resistance R.sub.w.

[0020] As is further evident in FIG. 1, the iron circuit of the solenoid valve 1 comprises the armature 14, the housing 26 and the cover disc 28 of the magnet assembly 20. In the illustrated exemplary embodiment, the heating operation of the magnet assembly 10 includes three different heating modes that comprise in each case a predetermined frequency range for the bipolar AC signals.

[0021] In a first heating mode, the frequency of the bipolar AC signals is predetermined from a first frequency range so that the valve does not react to the applied control signals. The first frequency range includes by way of example frequencies in the range of ca. 0.1 kHz to 2.0 kHz. In a second heating mode, the frequency of the bipolar AC signals is predetermined from a second frequency range so that a maximal inductive thermal output can be achieved. The second frequency range includes by way of example frequencies in the range of ca. 2.1 kHz to 3.0 kHz. In a third heating mode, the heating mode is switched between the first heating mode and the second heating mode in dependence upon the operating state of the vehicle, wherein the prevailing frequency of the bipolar AC signal is dependent upon the available onboard network voltage.

[0022] It is preferred that the optimal frequency for each voltage position is stored in the form of a characteristic curve in the control unit of the vehicle braking system.

[0023] Embodiments of the present invention provide a solenoid valve for a vehicle braking system, wherein the thermal output of said solenoid valve is to a considerable extent generated by means of electrical induction and the associated eddy currents directly in the iron circuit of the solenoid valve, and not, as is the case in the prior art, exclusively by ohmic losses in the coil winding.